THE 21 st CHESAPEAKE SAILING YACHT SYMPOSIUM ANNAPOLIS, MARYLAND, MARCH 2013

Save this PDF as:
 WORD  PNG  TXT  JPG

Size: px
Start display at page:

Download "THE 21 st CHESAPEAKE SAILING YACHT SYMPOSIUM ANNAPOLIS, MARYLAND, MARCH 2013"

Transcription

1 THE 21 st CHESAPEAKE SAILING YACHT SYMPOSIUM ANNAPOLIS, MARYLAND, MARCH 2013 A Refinement of the Methods Used to Determine the Balance of a Sailing Vessel during the Design Phase, with Application to Sail Design and Subsequent Sail Selection and Sailing Operations Capt. Iver Franzen, Iver C. Franzen & Associates, Annapolis, MD ABSTRACT The thrust of this paper is, first, to attempt to define the relationship between the individual sails, both together and separately, and the hull with somewhat more precision, and secondly, to develop a calculation tool to better establish this relationship, and to better anticipate the vessel's over all sailing behavior. Because of those factors that effect balance including and beyond those addressed by the traditional design approach as taught by most current texts on sailboat balance, the need for the factor "lead" will never go away. However, by including, as will be demonstrated, an additional balance factor, specifically the longitudinal sheet positions, into the balance equations during the design phase, sailboat balance can be predicted with better accuracy. The primary objective of this refinement will be the ability to design sail profiles, especially the complement of headsails, which will result in the least (adverse) change of balance when changing from one headsail to another, and which can be applied to either new designs, or to existing boats in need of out-of-balance remedies. This would mean that each anticipated sail combination can be analyzed for its lead, and therefore adjusted during the design phase to insure that proper helm is maintained from one combination to the next. NOTATION AR AWA AWS CEg CEd C D C L CLP CLRg CLRd D GM GZ max L LOD Aspect Ratio = luff²/sa, per sail, averaged Apparent Wind Angle Apparent Wind Speed, knots Center of Effort, geometric Center of Effort, dynamic Drag Coefficient Lift Coefficient Center of Lateral Plane Center of Lateral Resistance, geometric Center of Lateral Resistance, true dynamic Aerodynamic Drag Metacentric Height Heel Angle of Maximum Righting Arm Aerodynamic Lift Length on Deck, ft. LWL Length Waterline, ft. SA Sail Area, sq.ft. S/VBP Sailing Vessel Behavior Prediction TWA True Wind Angle TWS True Wind Speed, knots V Boat Speed, knots VDC Vertical Distance between CLRg and CEg VPP Velocity Prediction Program WHSR Wind Heel Stiffness Ratio = AWS²/Heel Angle Air Density,.0024 lb sec 2 /ft 4 Displacement, pounds Heel Angle INTRODUCTION A number of well-known design texts, papers, and dissertations have over the years addressed that aspect of yacht design pertaining to the balance of a sailboat, and in so doing have made it clear that it's, well, not clear, to the extent that, in spite of this extensive and valuable work, establishing a proper "lead" for a given design requires either an exhaustive, exhausting amount of calculation, or reliance on educated guesswork to estimate the lead. Numerous influences on a sailboat's balance include, but are not limited to her tenderness or stiffness; her keel and underbody profile; her beam, draft, and displacement relative to her length; the fullness of her lines, especially forward; the aspect ratio of her rig and whether she's a single- or multi-masted rig; even the age and condition of her sails. And, of course, that she will be expected to sail properly in a wide variety of conditions further complicates her designer's efforts to correctly and accurately determine her "lead." Most competent sailors understand the concept, function and, indeed, the importance of balance on a sailboat. And that understanding, even if only visceral, generally extends to most of the various ingredients and factors that result in good balance. The traditional approach to determining balance during the design phase, however, typically concentrates only on the geometric relationship between the centers of effort (CEg) of the sails themselves (and including only the generic foretriangle instead of individual

2 headsails) relative to the center of lateral plane (CLP). The attempt to apply this traditional design approach to balance within the operational realities of achieving good balance in a variety of conditions has therefore made it necessary to arrive at a specific lead for a given boat only by estimating within a broad range known by experience to be successful for that boat's genre. This has led to a number of out-ofbalance designs requiring adjustment, and sometimes significant surgery, after sea trials. One variable not previously discussed, however, is the position of the longitudinal sheeting positions, i.e., where on the boat does the sail, by way of the sheet, actually transfer all or part of its load to the boat? What effect might this sheeting position have on balance? And, once that sail's position of influence is more accurately determined, what improvements to, or new procedures for, the prediction of "lead" might be possible? BACKGROUND Years ago, the author was delivering a 38' cruising sailboat from the Virgin Islands to Newport, Rhode Island, and, a few days into the passage, found himself in building winds and seas. Nothing alarming, but time to shorten sail. In changing from a genoa (about 140%) to a working jib (about 80%), he suddenly found that his previous weather helm had not only eased, but had actually become a slight lee helm. Some years later, this experience repeated itself on a different boat. The larger genoa was replaced with a smaller working jib, and the helm changed from weather to lee. Given the teachings discussed above, perplexing. Back at the drawing board, these two situations were drawn up roughly from memory and investigated from the point of view of comparing the various actual sail plans to the boats' underwater profiles. Design method leads were within the ranges one would expect. Taking the actual sail shapes involved, the smaller headsails coupled with their respective mains resulted in CEgs farther aft than those based on the larger headsails. Again, as one might expect. Yes, heel had been reduced which would explain some lessening of weather helm, but certainly not to the extent experienced. Given that the balance leads had been effectively shortened with a smaller jib, the expectation was for a small increase in weather helm, which in turn would hopefully be eased again by the reduction in heel due to reducing power. Such, however, was not the case. Having considered all the other variables that might have had a bearing on these situations, the only remaining variable that could explain this dichotomy was the sheeting positions themselves, and how they might change the geometry of balance. with the geometric CEg of the mainsail (and other sails if applicable) to determine the CEg of the entire sailplan, and indicated on an outboard profile drawing. The CLP of the underwater profile of the boat is also geometrically determined, and shown on the same drawing. The longitudinal positions of the CEg and the CLP are compared, and the horizontal distance between them, i.e. the lead (balance lead), is expressed as a percentage of the waterline length. As we know, CEg is with very rare exception always ahead of CLP. One should be reminded here, well explained by numerous texts and papers, that a distinction exists between CEg and CEd, or dynamic CE. A similar distinction exists between CLP, a geometric measurement, and CLR, the dynamic position of the center of lateral resistance as a boat is sailing. In both cases, these dynamic positions move forward of their parent geometric positions when sailing, the magnitude of their movements depending on many variables such as wind speed, angle of attack, depth of draft of the sail, longitudinal position of that draft, depth of keel, length of keel, cross-sectional shape of the keel, shape of the leading edge of the keel, etc. Since these dynamic positions are constantly shifting depending on conditions at the moment, it's therefore impossible to rely on these positions as arbiters of balance. But, since they both move forward more or less concurrently, their "lead" approximates that of the geometric lead, therefore justifying the continued use of CEg and CLP to estimate the boat's lead, especially in the design phase. THE GEOMETRY OF "LEAD" Figure 1 shows a typical balance diagram, variations of which have been in our lexicon for decades. To review, the area of the foretriangle is used to geometrically determine the generic CEg of the headsail(s). This CEg is combined Figure 1 Typical Balance Diagram

3 Having said that, an additional refinement to the CLP can and should be applied. Since this discussion is concerned primarily with upwind sailing, the CEg of the rig can remain in play. However, since the CLR moves forward of the CLP immediately upon forward motion, regardless of point of sail, then an establishment of its position must be made in order to better establish the relationship between the sails and the hull, and to address helm considerations to be discussed in depth below. A geometric version of this CLR position, shown on Figure 1, has been well established by a number of experts as lying on a "vertical" chord line of the keel 25% aft of the leading edge of the keel, and 40% down from the waterline to the bottom of the keel. (The forefoot and the rudder are considered as offsetting each other.) Since other factors influencing its longitudinal position (Monk moments, leading edge shapes, etc.) can move the CLR in either direction, this geometric position of the CLR (henceforth, the CLRg) will be taken as the most useful tightly estimated point from which to formulate the following analyses. MODIFIED GEOMETRY OF "LEAD" Figures 2a & b Balance Diagrams for Actual Sails Figure 2a is a balance diagram showing the geometric lead, in this case with the actual genoa headsail shape coupled with the main. Figure 2b shows the balance and lead condition with a reduced headsail. While departing from using the generic foretriangle, both are otherwise based on the traditional means of establishing CEg. It can be seen that, as the headsail is reduced in size, the overall sail plan CEg moves very little. Until now, this has in part been a justification for using the generic foretriangle as the headsail portion of the balance diagram. However, if the sail area is considered as coupling with the lead dimension to create a moment, then the lesser moment with the smaller headsail should theoretically have, in the anecdotal situations above, allowed the bow to round up more readily, i.e., a greater weather helm. However, the sails, especially the headsails, do not impart their load upon the boat directly under the CEg of that sail, as the traditional balance diagrams suggest. If the sail were to be sheeted to a position on the boat directly below its clew, such as a club-footed staysail, then yes, such would be the case. However, all other headsails by necessity have their sheets led a certain distance aft in order to maintain proper tension on both foot and leach. The magnitude of this distance is based primarily on the height of the clew above the deck. All sailors have experienced the dynamic loads on these sheets. The next step then is to incorporate some representation of these loads into the geometry of lead.

4 Figure 3 Modified Balance Geometry, #2 Genoa, 100%. Figure 3, based on the same boat and sail plan as Figure 2, proposes a geometric method for doing this. First, it requires that the generic foretriangle be abandoned, and that the actual proposed headsails be worked with instead. On the drawing, indicate a given sail's sheet and where it meets the deck (the sheet position). (Authorities vary as to the exact angle the sheet should travel from the sail. Some say to bisect the angle at the clew, others to split the difference between this bisector and the line from the sail's CEg to the clew, still others say to start at a point on the luff 40% of the hoist up from the tack and draw a line from that to the clew, the extension of which is the sheet. The right answer for a given sail is generally somewhere in between these variations, which will more closely coincide with higher clews and lower aspect ratios.) Once the sheeting position is located, draw a triangle the corners of which are the head and tack of the sail and the sheet position (ignoring the clew). Find the geometric center of this triangle in the normal fashion. This now becomes that sail's CEg, which will more closely approximate its actual influence on the boat. When coupling this sail with the rest of the sail plan (main, etc.) to establish the overall CEg, continue to use the sail's actual area, but with this modified position of its center of effort.

5 APPLICATION TO EXISTING VESSELS Figures 5 represents a fairly close approximation of the arrangements described in the anecdotes above. In this arrangement, the helm stayed slightly lee until about 18 knots of wind, above which it went weather. What becomes apparent is that this sailing vessel example, which showed a traditionally derived lead of 18%, now, with its #1 genoa, and accounting for the inclusion of the sheet's influence on the boat, shows a lead in Figure 4 of 14.3%. If the same modified process is applied to Figure 5, with the smaller headsail, then a lead of 14.9% is arrived at as shown. This is contrary to the virtually unchanged lead when using only the sails themselves to determine the lead. Figure 4 Sail Plan of the boat described in the anecdotal example, in this case with her #1 genoa.

6 Figure 5 Modified Balance Geometry, small working Jib It is perhaps now becoming apparent as to why, in the experiences described above, the smaller headsail induced a lee helm. Simply put, the sheet position for the smaller headsail was too far forward, creating a balance lead that differed significantly and detrimentally from that derived from the genoa. The correction for this vessel then, if it is assumed that the balance was correct for the genoa (i.e., the full sail plan), is that any smaller headsails should have profiles which, with their sheet positions included, would generate a similar or lesser lead. In this case, this would be accomplished by reshaping the smaller headsails with higher clews in order to move their sheet positions aft. Figure 6 shows how this might take shape, in that a small working jib of an area similar to the small jib in Figure 5 is reshaped with a higher clew so as to move the sheet position aft significantly. The resulting balance lead is 12.6%, less than the genoa's 14.3%, resulting in a reduced sail plan that continues to maintain acceptable balance, such that, while the helm still stays lee in light air, it becomes weather at a more useful lower wind speed of about 14 knots, or about when you'd want to reduce sail.

7 Figure 6 Reshaped small working jib to correct lead and helm. As a further illustration of how this approach might be applied to correcting an existing boat's performance, let's look at the case of a 31' fractionally rigged racer-cruiser whose weather helm with her 160+% genoa was annoyingly excessive. The clew of this sail was not particularly high, but high enough to put the sheet position quite far aft, at about the.8lod position. The owner of the boat, however, was particularly enamored of this sail, most likely due to the magnitude of the financial investment therein. After being the last boat at the windward mark with discouraging consistency, the crew rebelled, and insisted that the #2 jib be tried next time out. Next race (wind about 10kt), first to the mark, first to the finish line! In addition to quicker, more efficient tacking, this 110%, fairly low clewed, full hoist sail put its sheet position quite a bit farther forward at about the.5lod position. Applying the modified geometry described above, this sail increased the boat's balance lead and lessened the weather helm significantly. The foot came off the brake and the boat was allowed to sail as intended. Of course, lessening the heel helped as well, while still keeping plenty of power. The big genoa was still useful as an off-the-wind sail, so the owner was not entirely bereft. But the #2 became his #1 windward sail.

8 APPLICATION TO NEW DESIGN Therefore, if the primary headsail's contribution to the overall balance has been determined by design or proven by experience to be correct, and can therefore be taken as the "baseline" lead, then, by shaping all other headsails such that their sail+sheet position geometry yields similar or lesser balance leads, good overall balance should be easier to maintain throughout the suit of sails. It will appear that lead dimensions will be smaller using this method. But, if the boat sails properly with the slight weather helm known to produce the best windward performance, then so be it, these numbers might become our new benchmarks. This presents a new problem, however. If the effort is to establish a single indicator of how a boat is going to balance itself, as the traditional approach presently does, then having a distinct dimensional lead for each headsail is counter to that. To further investigate this issue, an additional factor must be introduced into the modified lead calculations. This was hinted at above in the discussion of Figures 2 and 3, but without the benefit of accounting for the effects of the sheeting positions. Now that those effects are being included, the idea of considering lead as a moment rather than a dimension becomes more important. For example, looking again at Figures 5 & 6, lead moments of lead x SA (assuming the same wind pressures for both) further confirm the adverse helm change with that particular smaller headsail. Even with this it will be necessary to approach this as a range of moments for a given boat, since we're dealing with multiple sail combinations, rather than a single foretriangle, making a new single indicator for the entire sail complement difficult. It might be possible, however, to minimize the magnitude of this range such that a firm sense of overall balance can be achieved, especially with the primary headsails. If the idea of balance is to compare the effects of competing entities, then the lead moment must be considered as offsetting another moment for this to have meaning. Since the lead moment is one which is meant to be a falling-off moment, it's function then can be seen as offsetting a rounding-up moment, or, more accurately, offsetting most of that rounding-up moment, since a small amount of it is considered beneficial. And the best indicator that the amount of residual rounding-up moment is correct is the amount of rudder angle required to offset that moment while keeping the boat on the most favorable windward course. The generally accepted range of optimum effective rudder angles to offset the rounding-up moment, while providing lift with minimum drag is 3-5 degrees. Therefore, part of the design process is to design the sails in such a way that the rudder angle for a given set of sails and conditions can be determined, as closely as practical. Then, if excessive weather or lee helms are calculated for a given sail combination within the range of wind strengths anticipated for that combination, then sail profile shapes and their associated sheet positions can be modified as necessary. One good way to test this application is to look at an existing boat considered by all to have been a very successful design. One such boat is the Cal 40, by C. William Lapworth, and for which he designed a full complement of headsails. Figure 7 is a simple profile sketch of this boat, showing both her traditionally derived lead of 18.5% relying on geometric centers only, and her lead of 9.2% based on her CEg as relating to her CLRg, or the geometrically derived CLR as discussed above. Figure 7 Profile of the Cal 40, showing traditional lead determination both from CLP, and from the CLRg. Also shown is the steering arm.

9 Figure 8 Cal 40, full main, #2 jib, moderate air, showing the Leads.

10 Figure 9 Determining the Lead dimension and the Transverse Offset dimension of the sail plan shown in Figure 8. The concept of solving for rudder angle to determine the final balance condition will require that the two competing balancing moments, Lead (Falling Off) and Luffing (Rounding Up), which can also be thought of as torques, be determined beforehand. First, for the arm components of these moments, the positions of the CEg and the CLRg relative to each other must be determined both horizontally and vertically, including accounting for the heel of the boat. Referring to Figures 8 & 9, the fore and aft Lead dimension between CEg and CLRg is shown in the normal fashion on Figure 8 and on the plan view of Figure 9. Also required is the total transverse offset of the sail plan, or the distance that the CEg is moved laterally off of the centerline due to both the camber/sheeting offset and the angle of heel. The range of these offsets, and the force components of the two moments in question will then be determined by the... S/V BEHAVIOR PREDICTION (S/VBP) TOOL With a few additional assumptions, sufficient and proper information is now available to utilize Figure 11 below, the S/V Behavior Prediction Tool spreadsheet, developed by the author for this paper. A typical condition calculated for is shown in Figures 8 and 9 above, and demonstrates the derivation of certain of the pre-entries required prior to final calculation, such as the lead dimension, the vertical distance between CLRg and CEg (VDC), and the initial camber offset sheeted closehauled. Additional foundation information required includes displacement, metacentric height (GM) derived from previously established stability information, sail area, beam, and main foot length (E). Also required will be rudder area and rudder arm, taken from the rudder's CEd to the CLRg. A plot of various curves, an example of which is shown below in Figure 12, will be created based on the output of these calculations. These curves will be plotted against a range of true wind speeds at a given apparent wind angle, in this case 30º. The assumptions for the specific Figure 11 calculation are a) apparent wind is 30º; b) AR-related lift and drag

11 coefficients and their associated ratios are derived from numerous sources and averaged into the Table B matrix as shown on Figure 11, c) boundary layer considerations will be ignored, and d) performance information has been established either by VPP or by underway experience, and indicated in Figure 10. In the S/VBP Tool, first enter, from condition parameters and from Figures 8 and 9, the following: TWS and AWS in knots, primary (reference) SA, actual SA for the condition being tested, AWA, GM, LWL, rudder area, rudder arm, VDC, horizontal distance CEg-CLRg (Lead), and the aspect ratio (P[or I]² / SA) per sail, averaged. Additional manual entries from prompts in the spreadsheet are: upright offset factor, lift coefficient, and Drag-Lift (D/L) ratio. The subsequent calculations first yield the profile drag heel angle and the resulting effective sail area. Table A in the S/VBP tool shows righting moments against heeling moments per degrees of heel. The pertinent used in the subsequent calculations is taken from the coincidence of the two moments for a given wind speed. Righting moment is taken as times GM (in this case estimated, as actual hull lines and stability information is unavailable) times. Heeling moment is wind pressure at the given AWS times the SA adjusted for heel times the VDC adjusted for heel. Table B indicates the lift and drag coefficients to be used, in this case parametrically estimated, which then yield the lift and drag forces, which in turn, by way of the standard forces/vectors diagrams shown, yield the angle between the lift and the resultant. Since lift is now known, the resultant is calculated. The angle between the resultant and the side force is now determined, which, along with the resultant, are used to calculate the thrust. That same pair of factors now also yields the side force. To this horizontal side force is added a downlift /downforce adjustment in the form of: sine² of the profile drag heel angle, times the side force. This Adjusted Side Force, together with the Thrust, comprise the forces that will be applied to the Lead and the Transverse Offset respectively to arrive at the Falling Off and Rounding Up moments. These moments can, and perhaps should, also be considered torques. The transverse offset is then calculated. The upright camber offset is determined by diagram as shown in the plan view of Figure 9, or by a predetermined fraction of the beam. This upright offset is then multiplied by the cosine of the heel angle to arrive at an adjusted camber offset. This is added to the offset caused by the boat's heel, which is found by multiplying VDC by the sine of the heel angle. The sum of these two offsets is the total transverse offset, based on the profile drag heel angle. Since the adjusted side force is greater than the profile drag, the profile drag heel angle is adjusted accordingly, becoming the side force (Adjusted) Heel Angle. This adjustment is applied to the transverse offset, becoming the Adjusted Transverse Offset. It is the outboard end of this transverse offset arm upon which the thrust force acts, thereby creating the Rounding Up moment/torque. Now that the Lead has been more precisely measured by incorporating the sheeting position and confirming the CLRg, and the side force established, multiplying one times the other yields the Falling Off moment/torque. These two opposing moments/torques can now be compared as shown, specifically by subtracting the Falling Off (Lead) Moment from the Rounding Up (Luffing) Moment to arrive at the Residual Steering Moment. A positive result indicates a weather helm, a negative result a lee helm. The magnitude of this residual moment needs to be offset by a similar steering moment in order to hold a desired course, which in turn, assuming the range of steering moments vs. rudder angles has been established as shown on Figure 11, yields the effective rudder angle required, in this case at 4º. A distinction needs to made here between effective rudder angle and actual rudder angle. Since a boat sailing to windward will be making a certain amount of leeway, the water flow approaching the rudder will not be parallel to the boat's centerline. Generally speaking, the angle of that flow into the rudder, the downwash angle, will be about half the leeway angle. If the leeway angle is often approximately 4 degrees, then the downwash angle will be about 2 degrees, and can be used as the correction for most normal sailing situations. Therefore, if the effective rudder angle is 4º, then the actual rudder angle will be 6º. At a true wind speed of 10 knots in this case, the resulting effective rudder angle from the calculations in Figure 11, at 4º, is essentially optimum. Considering the gradually increasing draft of aging sails, this is a good starting point, although something closer to 2.5-3º might be even better with new sails. Of note is that the modified method dimensional lead, at 3%, is very close to the main/genoa arrangement at 2.8%. Given that the #2 jib most closely approximates the foretriangle, one might consider this condition to be her benchmark condition. For a racer-cruiser like this boat, having this primary sail with a foot you can see under and not scoop water, while still low enough for good racing performance, is just right. For a true racer, this foot might be closer to the deck, with the rest of the CEg/CLRg/steering geometry designed such that similar results to Figure 8 are still achieved. The larger #1 can then be tailored to be a true deck-sweeper. For a world cruiser, a #2 with a slightly higher foot/clew might be advisable, with the rest of the configuration designed accordingly. Two items should be noted at this point: First, The HM derivation, described above as part of Table A, of wind

12 pressure at the given AWS times the heeled SA times the heeled VDC is essentially the same as the HM = HM0º x Cos² This construct is presently under review (Johnson, et al, 2013), especially for higher heel angles (>GZ max ). This S/VBP tool may need to be modified accordingly as this research progresses. Second, that this sail plan has been calculated up through winds much stronger than would normally be carried by this plan, as shown in the graph in Figure 12. A by-product of this S/VBP Tool may then in the future be the ability to also predict behavior when the boat is in extremis, not only in terms of both heel and helm response, but also downflooding. However, since neither lines nor stability information are available in this case, the effects of heel angles beyond GZ max have not yet been incorporated into the S/VBP Tool. GM in this case has been parametrically estimated. Figure 10 Performance data for the Cal 40 sailing to windward, assuming 30º apparent wind. Figure 10a Performance data obtained from showing estimated adjustments for 50% ± reduced sail, and sailing with 45 degrees of apparent wind.

13 Figure 11 - Construction of the Rounding Up (Fig. A) and Falling Off (Fig. B) Moments (Torques), in addition to the calculations to determine her Residual Steering Moment, and, finally, the rudder angle needed to hold a steady course. See also the Appendix for additional Rounding Up & Falling Off Moment/Torque constructions for other upwind points of sail.

14 Figure 12 Graphic Results derived from the S/VBP calculation procedures in Figure 11, Sail Plan #1, the reference plan. Figure 13 shows the Cal 40's S/VBP curves with her genoa. Applying the modified balance geometry shown above and the balance/helm calculations now results in very light to moderate weather helm up to about 10 knots of wind, becoming heavier to handle in the knot range, as one would expect for full sail. Experience has taught that weather helm in light air is generally very minimal, and occasionally becomes a tolerable lee helm. This condition is confirmed here. In extremis situations also now become more apparent. Figure 13 S/VBP results, Sail Plan #2, Full Sail.

15 As the wind freshens, shortened sail configurations at 45º apparent wind are shown in Figures 14 and 15. It is interesting to compare these two configurations, as they have somewhat similar sail areas, but Figure 14, Plan #6, is showing a double reefed main with a working jib, while Figure 15, Plan #8, has a single-reefed main with a storm jib. Their balance leads are 3.34' (11%) and 0.04' (0%) respectively, a significant difference. As might be expected, the weather helm for Plan #8 starts to get heavy fairly early at around knots of wind. Plan #6, on the other hand, is keeping a reasonable helm until about knots of wind, which most would consider preferable in these conditions, even at the expense of a lee helm at winds less than 12 knots. Figure 14 S/VBP results, Sail Plan #6, double-reefed main & working jib. Figure 15 S/VBP results, Sail Plan #8, single-reefed main & storm jib.

16 It is also interesting to note, however, that, while Plan #6 exhibits better helm behavior than #8, it also heels about 8-10% more than #8. Granted, the sail area for #6 is about 10% greater, but its VDC is about 5% less. So, yes, in this case the proper lead has everything to do with keeping a better helm, even in spite of a very small disadvantage in heel. For purposes of calculating these reduced sail scenarios, the boat speed information shown above in Figure 10a is adjusted downward assuming the sail area is reduced by approximately half, and whose approximation is shown in that Figure by the curve "1/2 sail area boat speed." By the way, getting back to the anecdotal situation in Figures 4 & 5, applying the S/VBP Tool to the full sail arrangement, including sheets, Figure 4 yields an optimum weather helm of about 3º in moderate conditions. But, as suspected, the smaller headsail (low clew, forward sheet position) actually reduced that helm to less than half, even in stronger conditions. (That it didn't go to a lee helm in the S/VBP as experienced is most likely due to the author's inadequate memory of the details of the boat's actual configuration.) As also suspected, when calculating for a small higher clewed jib (sheeting farther aft) of the same area, the resulting weather rudder angle increased back up to almost 3º. Clew height and sheet position do make a difference. The consistency of good balance results shown here throughout the Cal 40's sail plan complement would appear to lend some credence this approach, as well as indicating certain combinations that might be less than ideal (e.g., Figure 15). If so, it would then indicate that Mr. Lapworth had an excellent sense of how to arrange a suit of sails to best advantage. He, like all experienced sailors, knew the best shapes of sail profiles for the conditions those sails were expected to operate in. Granted, those profile shapes have always been driven by other factors as well, such as heavy weather visibility and keeping them out of the water. But his additional sense of maintaining good sailing balance throughout the complement of sails is apparent, as shown in Figure 17. Figure 17 The Cal 40 with all the headsails shown together as drawn by Mr. Lapworth. Note the relationship of the heights of their clews and the resulting relative coincidence of their sheeting positions. SPLIT RIGS The discussion to this point has focused on sloops. This proposed procedure, however, is just as applicable to ketches, yawls, schooners, and any other sailing craft of any rig, perhaps even more so. If, from the above study, one can assume that sail shapes can now be designed with somewhat more accuracy, then the inherent additional flexibility of split rigs lends itself well either to better fine-tuning of design development, or to the ability to more easily remedy existing balance and performance problems. An excellent example of the latter point is the pair of anecdotal situations described earlier. Yes, these boats balanced nicely with their highclewed genoas and their mains, and suffered when sailed with the small low-clewed jibs and the mains. What was not mentioned above, however, was that both these boats were ketches, and setting the mizzens in both cases immediately solved the lee helm problems. As is the case with many ketch rigs, they sailed nicely to windward in light/moderate conditions as sloops, with the mizzens not coming into play until other conditions and points of sail were encountered. However, as soon as the situation changed, and the balance changed, having the mizzens available became essential to get the balance back where it should be. Indeed, given the difficulty that the big genoas often presented for other reasons, sailing with the mizzen as a matter of course along with the smaller low-clewed jibs became the standard practice. And, where a sloop may have needed the expense of a new sail or two to correct the overall complement, not so with the ketches, at least not these two. OTHER OBSERVATIONS AND THOUGHTS Headsail roller-furling, in addition to being a very handy tool for sail handling (when done correctly), especially for short-handers, has introduced an interesting, and actually very useful wrinkle to the balance question. As the forgoing has demonstrated, smaller heavier-weather headsails do better for many reasons, including maintaining balance, when the clews of these sails rise as they get smaller. It so happens that, as a roller-furled headsail is rolled in, the clew does exactly that. Consequently, when they are "reefed," or rolled only part way so as to allow a smaller portion of the sail to remain, they behave not unlike the suit of sails shown in Figure 17 (albeit with lower aspect ratios). Balance is therefore less likely to go astray as the sail is reefed for the sailing conditions that require that reefing. The remaining caveat here then is that sails which are going to be used as such be carefully designed, built and reinforced in the key areas in order to limit the damage and poor sail shape (excess draft, etc.) that otherwise occurs when a standard sail is partially rolled up. Since these big roller-furling genoas are generally considered cruising sails only, their clews tend to be

17 higher to begin with, with their commensurate well-aft sheeting positions. A common sight, especially on bareboats in the Caribbean Christmas winds, is for those sailors, perhaps a bit spooked by handling a strange boat in those hefty winds, to simply roll out the genoa and sail under that alone. Yes, sail has been reduced, and the boat is more or less in control. The quality of seamanship thus displayed is perhaps best left for another discussion, although one aspect does stand out they seem to be sailing in reasonably good balance (and which they seem to like to brag about at the bar at the end of the day). Figures 18 and 19 may provide some insight as to why this can happen. This is the Cal 40 again, this time rigged for cruising with a typical big roller-furling genoa, sailing to windward (30º apparent wind) in "bareboat" mode. Applying the modified lead approach, it can be seen that, in normal Christmas winds, her helm becomes weather at a little over 14 knots of wind. This is one case where extra heel may work to advantage to a point! In stronger Christmas winds, weather helm can actually become a handful at about 24 knots of wind. Light air, lee helm as would be expected. And at broader apparent wind angles starting at about 45º, the helm becomes weather even in light winds. Figure 18 Cal 40 rigged for cruising, sailing with genoa only. S/VBP results: Figure 19 S/VBP curves for the Cal 40 sailing in "Bareboat Mode."

18 A variation on this phenomenon, which has been much used for many years, is the sail combination "jib and jigger." On many ketches and yawls, sailing with the big jib alone may result in a neutral or slight lee helm, which is then corrected by setting the mizzen. Back when genoas weren't quite so big, this was a fairly effective way of shortening sail, or perhaps just sailing in a more relaxed fashion, especially with a midship awning on a hot sunny day. CONCLUSION The idea of using moments to determine balance is certainly not new. It has become clear from the forgoing, however, that simply using the traditional geometric methods, especially the profile sail area x profile wind force (or even a more precisely calculated side force, for that matter) times the basic geometric lead to get the falling off moment would give an erroneously high result, and therefore a false lee helm. The thrust has always been calculated correctly, as has the offset arm due to heel, but if it's balanced against an over-simplified falling off moment, then its value is sabotaged for purposes of determining balance. The idea of showing the CEgs of the actual headsails rather than the foretriangle is also not new. Several sources have used actual headsail shapes for otherwise traditional balance discussions, as well as showing figures as to how the CEg moves fore and aft with different sail combinations. None would appear to have gone beyond this, though, and have spoken only generally of being careful with different combinations so as not to go out of balance. However, it would also appear that none have included the sheet positions as part of the geometry of establishing the CEg of headsails, something which now appears beneficial in establishing the sail's actual effect on the boat, especially when considering the falling off moment. The approach proposed herein to predetermining sailing balance is meant to augment the traditional approach to lead that has been in practice for many years, and, indeed, is still a good conceptual starting point today when working up a new design in the early going. With the understanding that the many factors discussed above that have complicated the traditional approach have not changed, this proposed refined approach is similarly constrained to a certain degree of approximation. Any "improvements" generated by this particular proposal are, well, probably only that improvements, refinements, adjustments. It is hoped, however, that these suggested procedures might a) be a useful tool for correcting existing balance problems and b) take at least some of the guesswork out of determining the proper shape of a boat's hull, and especially the arrangement of her appendages (also, by the way, fairly easily adjustable in the design process), her rig, and her complement of sails so as to achieve good sailing balance, particularly in the later stages of refining a design. And in time, perhaps some better agreement and narrowing of the often very wide ranges of suggested appropriate leads for a given genre of boats can be achieved. Finally, it should be noted from the results graphs that, with too much sail in too much wind, the result is not only too much heel, but, just as dangerously, rapidly increasing weather helm. Professor Bruce Johnson, Captain Jan Miles, et.al. have been doing excellent work over the course of several papers (Miles et al, 2007; Johnson et al, 2009 and 2013) in confirming this fact from a shipboard measurement approach. While establishing the WHSR as a useful measure of stiffness, they are also confirming that efforts by a helmsman to fall off during a gust, especially when close reaching, are wholly ill-advised, not only because it's counter to the idea of depowering when necessary, but also because, as seen from the graphed results herein, increasingly excessive weather helm will simply not allow it. REFERENCES Baader, J., "The Sailing Yacht," W.W. Norton & Company, New York, NY, Chapelle, H., "Yacht Designing and Planning," W.W. Norton & Company, New York, NY, Claughton, A. & Pemberton, R., "Hull Sailplan Balance, "Lead" for the 21 st Century," 22 nd International HISWA Symposium on Yacht Design & Yacht Construction, Amsterdam Edmunds, A., "Designing Power & Sail," Bristol Fashion Pub., Enola, PA, Gillmer, T. & Johnson, B., "Introduction to Naval Architecture," Naval Institute Press, Annapolis, MD, Johnson, B., Lasher, W., Miles, J., Curry, W., "Uncertainties in the Wind-Heel Analysis of Traditional Sailing Vessels," Proceedings of the 21 st Chesapeake Sailing Yacht Symposium, Annapolis, MD, March 12-13, Keuning, J.A. & Vermeulen, K.J., "On the Balance of Large Sailing Yachts," 17 th International HISWA Symposium on Yacht Design & Yacht Construction, Amsterdam Keuning, J.A. & Vermeulen, K.J., "Keel Rudder Interaction on a Sailing Yacht," 19 th International HISWA Symposium on Yacht Design & Yacht Construction, Amsterdam Larsson, L & Eliasson, R., "Principles of Yacht Design," International Marine, Camden, Maine, Marchaj, C.A., "Sailing Theory and Practice," Dodd, Mead & Company, New York, NY, Milgram, J.H., "Sail Force Coefficients for Systematic Rig Variations," Technical & Research Report R-10, SNAME, September, 1971.

19 Skene, N., "Elements of Yacht Design," Sheridan House, Dobbs Ferry, NY, website, "Swedish Sailing and Racing," APPENDIX:

Navigation with Leeway

Navigation with Leeway Navigation with Leeway Leeway, as we shall use the term, means how much a vessel is pushed downwind of its intended course when navigating in the presence of wind. To varying extents, knowledge of this

More information

S0300-A6-MAN-010 CHAPTER 2 STABILITY

S0300-A6-MAN-010 CHAPTER 2 STABILITY CHAPTER 2 STABILITY 2-1 INTRODUCTION This chapter discusses the stability of intact ships and how basic stability calculations are made. Definitions of the state of equilibrium and the quality of stability

More information

Multihull Preliminary Stability Estimates are Fairly Accurate

Multihull Preliminary Stability Estimates are Fairly Accurate Multihull Design (Rev. A) 45 APPENDIX A ADDITIONAL NOTES ON MULTIHULL DESIGN MULTIHULL STABILITY NOTES Multihull stability is calculated using exactly the same method as described in Westlawn book 106,

More information

Sail Trimming Guide for the Beneteau 40

Sail Trimming Guide for the Beneteau 40 INTERNATIONAL DESIGN AND TECHNICAL OFFICE Sail Trimming Guide for the Beneteau 40 October 2007 Neil Pryde Sails International 1681 Barnum Avenue Stratford, CONN 06614 Phone: 203-375-2626 Fax: 203-375-2627

More information

NORTH SAILS FAST COURSE MAINSAIL

NORTH SAILS FAST COURSE MAINSAIL NORTH SAILS FAST COURSE MAINSAIL Contents: Introduction. Step 1 Set twist with mainsheet tension. Step 2 Set depth with mast bend and outhaul tension. Step 3 Set draft position with luff tension. Step

More information

National Maritime Center

National Maritime Center National Maritime Center Providing Credentials to Mariners (Sample Examination) Page 1 of 8 Choose the best answer to the following Multiple Choice Questions. 1. In illustration D001SL, what is the edge

More information

North Sails Seattle Thunderbird Tuning Guide

North Sails Seattle Thunderbird Tuning Guide Page 1 of 6 North Sails Seattle Thunderbird Tuning Guide Introduction The following tuning guide is meant as a good starting point in setting up your boat. Since not all Thunderbirds are exactly alike

More information

Thanks to North Sails, who gave us these fast rigging tips.

Thanks to North Sails, who gave us these fast rigging tips. Mast Step Mast Rake Thanks to North Sails, who gave us these fast rigging tips. Congratulations on your purchase of North Club 420 sails. We have worked hard to design and produce the fastest, easiest

More information

Principles of Sailing

Principles of Sailing Principles of Sailing This is a PowerPoint set of charts presented by Demetri Telionis on March 21, 2015 at the Yacht Club of Hilton Head Island. The aim of this presentation was to help the audience understand

More information

Reliable Speed Prediction: Propulsion Analysis and a Calculation Example

Reliable Speed Prediction: Propulsion Analysis and a Calculation Example Reliable Speed Prediction: Propulsion Analysis and a Calculation Example Donald M. MacPherson VP Technical Director HydroComp, Inc. ABSTRACT Speed prediction is more than just bare-hull resistance. Speed

More information

Melges 24 Sailing Guide

Melges 24 Sailing Guide RACING GUIDES www.ullmansails.com Upwind Sailing Melges 24 Sailing Guide The Melges is most efficient when sailed as flat as possible. Excessive heel causes leeway which is slow. The skipper must work

More information

Optimist Tuning Guide

Optimist Tuning Guide Optimist Tuning Guide Sail Care: To help you re new racing sail stay in top condition as long as possible here is some tips - Try not to crease your sail, some creases can cause MIT tears in your sail

More information

The Definite Guide to Optimist Trim

The Definite Guide to Optimist Trim The Definite Guide to Optimist Trim by Martin Gahmberg & the WB-Sails team The purpose of this tuning guide is to help you trim your WB sail optimally by learning the effects of the controls: How to change

More information

OFFSHORE RACING CONGRESS

OFFSHORE RACING CONGRESS World Leader in Rating Technology OFFSHORE RACING CONGRESS ORC Speed Guide Explanation 1. INTRODUCTION The ORC Speed Guide is a custom-calculated manual for improving performance for an individual boat.

More information

HIGHLANDER TUNING GUIDE

HIGHLANDER TUNING GUIDE HIGHLANDER TUNING GUIDE This document provides information on preparation, Quantum s sail tuning and technique, and other helpful tips to make sure you re ready to meet your challenge in today s competitive

More information

PERFORMANCE PREDICTION

PERFORMANCE PREDICTION PERFORMANCE PREDICTION Design #622 First 35 with 2.3m Fin Keel For Chantiers Beneteau Farr Yacht Design, Ltd. Copyright May 7, 2012 PO Box 4964, Annapolis, MD 21403 USA Tel: +1 410 267 0780, Fax: +1 410

More information

SHIP FORM DEFINITION The Shape of a Ship

SHIP FORM DEFINITION The Shape of a Ship SHIP FORM DEFINITION The Shape of a Ship The Traditional Way to Represent the Hull Form A ship's hull is a very complicated three dimensional shape. With few exceptions an equation cannot be written that

More information

THE INTERACTION BETWEEN SAILING YACHTS IN FLEET AND MATCH RACING SITUATIONS

THE INTERACTION BETWEEN SAILING YACHTS IN FLEET AND MATCH RACING SITUATIONS THE INTERACTION BETWEEN SAILING YACHTS IN FLEET AND MATCH RACING SITUATIONS P.J. Richards, Yacht Research Unit, University of Auckland, New Zealand N. Aubin, École Navale, France D.J. Le Pelley, Yacht

More information

Comparative Stability Analysis of a Frigate According to the Different Navy Rules in Waves

Comparative Stability Analysis of a Frigate According to the Different Navy Rules in Waves Comparative Stability Analysis of a Frigate According to the Different Navy Rules in Waves ABSTRACT Emre Kahramano lu, Technical University, emrek@yildiz.edu.tr Hüseyin Y lmaz,, hyilmaz@yildiz.edu.tr Burak

More information

THE 21 st CHESAPEAKE SAILING YACHT SYMPOSIUM ANNAPOLIS, MARYLAND, MARCH 2013

THE 21 st CHESAPEAKE SAILING YACHT SYMPOSIUM ANNAPOLIS, MARYLAND, MARCH 2013 THE 21 st CHESAPEAKE SAILING YACHT SYMPOSIUM ANNAPOLIS, MARYLAND, MARCH 2013 A wind tunnel study of the interaction between two sailing yachts P.J. Richards, D.J. Le Pelley, D. Jowett, J. Little, O. Detlefsen

More information

Choosing a sailplan..finding a sailplan which suits the deck layout, the interior, the hull, and the intended use...

Choosing a sailplan..finding a sailplan which suits the deck layout, the interior, the hull, and the intended use... Chapter 3 (..of The Cambered Panel Junk Rig...) Choosing a sailplan..finding a sailplan which suits the deck layout, the interior, the hull, and the intended use... Note: All diagrams are shown in full-page

More information

STABILITY OF MULTIHULLS Author: Jean Sans

STABILITY OF MULTIHULLS Author: Jean Sans STABILITY OF MULTIHULLS Author: Jean Sans (Translation of a paper dated 10/05/2006 by Simon Forbes) Introduction: The capsize of Multihulls requires a more exhaustive analysis than monohulls, even those

More information

Tall Ships America Safety Under Sail Forum: Sailing Vessel Stability, Part 1: Basic Concepts

Tall Ships America Safety Under Sail Forum: Sailing Vessel Stability, Part 1: Basic Concepts Tall Ships America Safety Under Sail Forum: Sailing Vessel Stability, Part 1: Basic Concepts Moderator: Captain Rick Miller, MMA Panelists: Bruce Johnson, Co-Chair Working Vessel Operations and Safety

More information

Thank you for choosing a North Sails P Class Sail

Thank you for choosing a North Sails P Class Sail North Sails New Zealand Pakenham St, Viaduct Basin PO Box 37419, Parnell Auckland, N.Z. Ph (09) 359 5999 Fax (09) 359 5995 Email derek@nz.northsails.com Web Site www.nz.northsails.com Thank you for choosing

More information

DESIGN #446 First 36.7-Cruising Keel for Chantiers Beneteau S.A.

DESIGN #446 First 36.7-Cruising Keel for Chantiers Beneteau S.A. DESIGN #446 First 36.7-Cruising Keel for Chantiers Beneteau S.A. Farr Yacht Design, Ltd. Copyright March 12, 2001 P.O. Box 4964, Annapolis, MD 21403 USA Tel: (410) 267-0780 Fax: (410) 268-0553 E-mail:

More information

DESIGN #446 First 36.7-Racing Keel for Chantiers BeneteauS.A.

DESIGN #446 First 36.7-Racing Keel for Chantiers BeneteauS.A. DESIGN #446 First 36.7-Racing Keel for Chantiers BeneteauS.A. Farr Yacht Design, Ltd. Copyright March 12, 2001 P.O. Box 4964, Annapolis, MD 21403 USA Tel: (410) 267-0780 Fax: (410) 268-0553 E-mail: info@farrdesign.com

More information

Bluenose Class Jib Trim by: Andreas Josenhans (North Sails Atlantic)

Bluenose Class Jib Trim by: Andreas Josenhans (North Sails Atlantic) Bluenose Class Jib Trim by: Andreas Josenhans (North Sails Atlantic) The current Bluenose Jib has been unchanged from 2006-2015. Over the years, a Bluenose headsail was changed to achieve the following.

More information

Figure 1 Figure 1 shows the involved forces that must be taken into consideration for rudder design. Among the most widely known profiles, the most su

Figure 1 Figure 1 shows the involved forces that must be taken into consideration for rudder design. Among the most widely known profiles, the most su THE RUDDER starting from the requirements supplied by the customer, the designer must obtain the rudder's characteristics that satisfy such requirements. Subsequently, from such characteristics he must

More information

SAMPLE MAT Proceedings of the 10th International Conference on Stability of Ships

SAMPLE MAT Proceedings of the 10th International Conference on Stability of Ships and Ocean Vehicles 1 Application of Dynamic V-Lines to Naval Vessels Matthew Heywood, BMT Defence Services Ltd, mheywood@bm tdsl.co.uk David Smith, UK Ministry of Defence, DESSESea-ShipStab1@mod.uk ABSTRACT

More information

Front Cover Picture Mark Rasmussen - Fotolia.com

Front Cover Picture Mark Rasmussen - Fotolia.com Flight Maneuvers And Stick and Rudder Skills A complete learn to fly handbook by one of aviation s most knowledgeable and experienced flight instructors Front Cover Picture Mark Rasmussen - Fotolia.com

More information

The USA Canterbury J. Class Rules

The USA Canterbury J. Class Rules Canterbury J Class Owners Association The USA Canterbury J Class Rules 2010 As Accepted 2008 and Revised February 2010 Published March 2010 The Canterbury J Class Rules ~ 2008 Page 1 of 10 THE CANTERBURY

More information

PERFORMANCE PREDICTION

PERFORMANCE PREDICTION PERFORMANCE PREDICTION First 40 Carbon Pack With Deep Fin Keel/ Carbon mast/ Asymmetric Spinnaker on Retractable Sprit For Chantiers Beneteau Farr Yacht Design, Ltd. Copyright July 22, 2014 PO Box 4964,

More information

CSC Learn to Sail Class

CSC Learn to Sail Class CSC Learn to Sail Class JUNE 2014 Pedram Leilabady LNYC Nomenclature Sailors Lingo! Direc@ons Ahead Astern 1 6/3/14 Main Parts Mainsail Jib Sails / Spars Head Mast Head Leech Luff Leech Luff Mainsail Clew

More information

DESIGN #374 Farr 40 With Masthead Spinnakers

DESIGN #374 Farr 40 With Masthead Spinnakers DESIGN #374 Farr 40 With Masthead Spinnakers Farr Yacht Design, Ltd. Copyright June 26, 2006 P.O. Box 4964, Annapolis, MD 21403 USA Tel: (410) 267-0780 Fax: (410) 268-0553 E-mail: info@farrdesign.com DESCRIPTION

More information

DESIGN #543 Beneteau First 10R For Chantiers Beneteau Deep Keel with Bowsprit

DESIGN #543 Beneteau First 10R For Chantiers Beneteau Deep Keel with Bowsprit DESIGN #543 Beneteau First 10R For Chantiers Beneteau Deep Keel with Bowsprit Farr Yacht Design, Ltd. Copyright July 29, 2005 P.O. Box 4964, Annapolis, MD 21403 USA Tel: (410) 267-0780 Fax: (410) 268-0553

More information

Handicap Adjustments The following are adjustments that PHRF NE normally makes to a base boat for non-standard equipment.

Handicap Adjustments The following are adjustments that PHRF NE normally makes to a base boat for non-standard equipment. Handicap Adjustments The following are adjustments that PHRF NE normally makes to a base boat for non-standard equipment. Base Boat Definition of a Base Boat: Will include all specifications per the manufacturer,

More information

STANDARD SAIL AND EQUIPMENT SPECIFICATIONS (Updated February, 2017)

STANDARD SAIL AND EQUIPMENT SPECIFICATIONS (Updated February, 2017) 1. Headsails, distinctions between jibs and spinnakers A. A headsail is defined as a sail in the fore triangle. It can be either a spinnaker, asymmetrical spinnaker or a jib. B. Distinction between spinnakers

More information

DESIGN #354 Benetau First 40.7 Racing Version for Chantiers Beneteau

DESIGN #354 Benetau First 40.7 Racing Version for Chantiers Beneteau DESIGN #354 Benetau First 40.7 Racing Version for Chantiers Beneteau Farr Yacht Design, Ltd. Copyright May 3, 2001 P.O. Box 4964, Annapolis, MD 21403 USA Tel: (410) 267-0780 Fax: (410) 268-0553 E-mail:

More information

An Investigation into the Capsizing Accident of a Pusher Tug Boat

An Investigation into the Capsizing Accident of a Pusher Tug Boat An Investigation into the Capsizing Accident of a Pusher Tug Boat Harukuni Taguchi, National Maritime Research Institute (NMRI) taguchi@nmri.go.jp Tomihiro Haraguchi, National Maritime Research Institute

More information

Drawing a detailed sail..the final job before cutting in canvas...

Drawing a detailed sail..the final job before cutting in canvas... Chapter 4 (..of The Cambered Panel Junk Rig...) Drawing a detailed sail..the final job before cutting in canvas... Introduction Before we are ready to construct a sail (see chapter 5), we need to produce

More information

Date: 18th December 2001

Date: 18th December 2001 Coaching Tips - J/24 Tuning Guide & Sail Trimming Written By: Stuart Jardine Date: 18th December 2001 Stuart Jardine, J/24 national champ five times over, tells you how to get the best results from your

More information

II.E. Airplane Flight Controls

II.E. Airplane Flight Controls References: FAA-H-8083-3; FAA-8083-3-25 Objectives Key Elements Elements Schedule Equipment IP s Actions SP s Actions Completion Standards The student should develop knowledge of the elements related to

More information

1. A tendency to roll or heel when turning (a known and typically constant disturbance) 2. Motion induced by surface waves of certain frequencies.

1. A tendency to roll or heel when turning (a known and typically constant disturbance) 2. Motion induced by surface waves of certain frequencies. Department of Mechanical Engineering Massachusetts Institute of Technology 2.14 Analysis and Design of Feedback Control Systems Fall 2004 October 21, 2004 Case Study on Ship Roll Control Problem Statement:

More information

ODOM CLASS SPECIFICATIONS

ODOM CLASS SPECIFICATIONS ODOM CLASS SPECIFICATIONS Effective March 1, 2004 1. GENERAL 1.1 Purpose of the Measurement Rules 1.1.1 The ODOM is a One-Design Class as defined by the American Model Yachting Association (AMYA). However,

More information

TUNE YOUR RIG FOR OUTRIGHT SPEED. J/88 Tuning Guide Solutions for today s sailors

TUNE YOUR RIG FOR OUTRIGHT SPEED. J/88 Tuning Guide Solutions for today s sailors TUNE YOUR RIG FOR OUTRIGHT SPEED 2 We hope you enjoy your J/88 Tuning Guide. North class representatives and personnel have invested a lot of time to make this guide as helpful as possible for you. Tuning

More information

Solo TUNE YOUR SAILS FOR OUTRIGHT SPEED. Solo Tuning Guide Solutions for today s sailors

Solo TUNE YOUR SAILS FOR OUTRIGHT SPEED. Solo Tuning Guide Solutions for today s sailors 1 Solo TUNE YOUR SAILS FOR OUTRIGHT SPEED 1 The Solo is a boat with a relatively simple rig. Once you are on the water there is little adjustment possible. It is essential therefore that you get the right

More information

E Scow Racing and Rigging Manual

E Scow Racing and Rigging Manual E Scow Racing and Rigging Manual Written by Mark Ehlers Editing and content revisions by Andrew Bartling Aspects of Sailing E Scows Crew weight should never exceed 675lbs. The target weight for 4 people

More information

J/24 Tuning Guide. Before The Boat Hits The Water

J/24 Tuning Guide. Before The Boat Hits The Water J/24 Tuning Guide Haarstick Sailmakers have used our years of experience building and racing J/24 s to develop a FAST set of sails, geared for performance in a variety of conditions. Together with the

More information

FROM OPERATIONAL PROFILE TO HYBRID PROPULSION Ir. P.T. van Loon, Ir. P van Zon, Feadship, The Netherlands

FROM OPERATIONAL PROFILE TO HYBRID PROPULSION Ir. P.T. van Loon, Ir. P van Zon, Feadship, The Netherlands SUMMARY FROM OPERATIONAL PROFILE TO HYBRID PROPULSION Ir. P.T. van Loon, Ir. P van Zon, Feadship, The Netherlands Every Feadship is designed, engineered and built to a specific and unique design brief,

More information

1 Tuning Platform Reseating Beam Pads Rudder alignment Noisy Foils Rig Tension...

1 Tuning Platform Reseating Beam Pads Rudder alignment Noisy Foils Rig Tension... Contents 1 Tuning... 2 1.1 Platform... 2 1.2 Reseating Beam Pads... 2 1.3 Rudder alignment... 3 1.4 Noisy Foils... 3 1.5 Rig Tension... 4 1.6 Mast rake... 4 1.7 Spreader rake... 5 1.8 Diamond tension...

More information

for Naval Aircraft Operations

for Naval Aircraft Operations Seakeeping Assessment of Large Seakeeping Assessment of Large Trimaran Trimaran for Naval Aircraft Operations for Naval Aircraft Operations Presented by Mr. Boyden Williams, Mr. Lars Henriksen (Viking

More information

Applications of trigonometry

Applications of trigonometry Applications of trigonometry This worksheet and all related files are licensed under the Creative Commons Attribution License, version 1.0. To view a copy of this license, visit http://creativecommons.org/licenses/by/1.0/,

More information

2002 Tuning in a Vanguard 15

2002 Tuning in a Vanguard 15 2002 Tuning in a Vanguard 15 If you are the kind of person that likes to roll up to the regatta an hour before the start, throw the mast up, select a catch-all shroud setting, and then just focus on getting

More information

Numerical study of aeroelasticity of sails

Numerical study of aeroelasticity of sails Numerical study of aeroelasticity of sails Alessandro Leone, Luciano Teresi* SMFM@DiS, Università Roma Tre, Roma, Italy * Corresponding author: Dip. of Studies on Structures, via Corrado Segre 6, 00146

More information

Heavy Weather Sailing How to be prepared

Heavy Weather Sailing How to be prepared Heavy Weather Sailing How to be prepared Vancouver International Boat Show - 2016 Introduction: Who has been in heavy weather? What did you experience? 1 INTRODUCTION strong & gale force winds not survival

More information

The Physics of Lateral Stability 1

The Physics of Lateral Stability 1 The Physics of Lateral Stability 1 This analysis focuses on the basic physics of lateral stability. We ask Will a boat heeled over return to the vertical? If so, how long will it take? And what is the

More information

PERFORMANCE MANEUVERS

PERFORMANCE MANEUVERS Ch 09.qxd 5/7/04 8:14 AM Page 9-1 PERFORMANCE MANEUVERS Performance maneuvers are used to develop a high degree of pilot skill. They aid the pilot in analyzing the forces acting on the airplane and in

More information

To My Friends in the UK

To My Friends in the UK To My Friends in the UK I seem to have promised Steve and Simon that I would write an article on tuning a Sonar for your website. Since tuning alone is not enough to be useful, here are some of my thoughts

More information

Planning and general precautions ithrust Tunnel Systems installations.

Planning and general precautions ithrust Tunnel Systems installations. Version 1.0 This recommendation will go through the different factors to consider when choosing where and how to fit thruster tunnels in a boat. Some of these recommendations might be difficult, or even

More information

THEORY OF WINGS AND WIND TUNNEL TESTING OF A NACA 2415 AIRFOIL. By Mehrdad Ghods

THEORY OF WINGS AND WIND TUNNEL TESTING OF A NACA 2415 AIRFOIL. By Mehrdad Ghods THEORY OF WINGS AND WIND TUNNEL TESTING OF A NACA 2415 AIRFOIL By Mehrdad Ghods Technical Communication for Engineers The University of British Columbia July 23, 2001 ABSTRACT Theory of Wings and Wind

More information

Setup &Tuning guide. Updated 1st February 07

Setup &Tuning guide. Updated 1st February 07 Setup &Tuning guide Updated 1st February 07 Boat preparation Tape a piece of batten to the backstay ram with a calibrated scale drawn on it. This will allow you to reproduce the same backstay settings

More information

Analysis of Shear Lag in Steel Angle Connectors

Analysis of Shear Lag in Steel Angle Connectors University of New Hampshire University of New Hampshire Scholars' Repository Honors Theses and Capstones Student Scholarship Spring 2013 Analysis of Shear Lag in Steel Angle Connectors Benjamin Sawyer

More information

SOLUTIONS FOR TODAY S SAILORS. Tuning Guide 05/11 NORTH SAILS

SOLUTIONS FOR TODAY S SAILORS. Tuning Guide 05/11 NORTH SAILS SOLUTIONS FOR TODAY S SAILORS Tuning Guide 05/11 NORTH SAILS The Farr 40 One-Design is a modern Grand Prix-type yacht designed specifically for the fun-loving owner-driver. A highly competitive Offshore

More information

Span. Windows Version 11.1 User Manual

Span. Windows Version 11.1 User Manual Span Windows Version 11.1 User Manual Formation Design Systems Pty Ltd 1984 2005 License & Copyright Span Program 1987-2005 Formation Design Systems. Span is copyrighted and all rights are reserved. The

More information

Calculating Forces in the Pulley Mechanical Advantage Systems Used in Rescue Work By Ralphie G. Schwartz, Esq

Calculating Forces in the Pulley Mechanical Advantage Systems Used in Rescue Work By Ralphie G. Schwartz, Esq Calculating Forces in the Pulley Mechanical Advantage Systems Used in Rescue Work By Ralphie G. Schwartz, Esq Introduction If you have not read the companion article: Understanding Mechanical Advantage

More information

INCLINOMETER DEVICE FOR SHIP STABILITY EVALUATION

INCLINOMETER DEVICE FOR SHIP STABILITY EVALUATION Proceedings of COBEM 2009 Copyright 2009 by ABCM 20th International Congress of Mechanical Engineering November 15-20, 2009, Gramado, RS, Brazil INCLINOMETER DEVICE FOR SHIP STABILITY EVALUATION Helena

More information

U.S.N.A. --- Trident Scholar project report; no. 315 (2003)

U.S.N.A. --- Trident Scholar project report; no. 315 (2003) U.S.N.A. --- Trident Scholar project report; no. 315 (2003) Performance Prediction of the Mk II Navy 44 Sail Training Craft with respect to Tank Testing, Velocity Prediction Programs, and Computational

More information

Instruction Manual. Features. Specification: Length: 730mm Width: 500mm Height: 1000mm Sail Area: 0.15m 2. Weight: 692g (w/o battery & receiver)

Instruction Manual. Features. Specification: Length: 730mm Width: 500mm Height: 1000mm Sail Area: 0.15m 2. Weight: 692g (w/o battery & receiver) AN UNBELIEVABLE SPEED MACHINE Instruction Manual Features Specification: Length: 730mm Width: 500mm Height: 1000mm Sail Area: 0.15m 2 Weight: 692g (w/o battery & receiver) Thank you for purchasing your

More information

Landing Craft - Choosing the Right Tool for the Job

Landing Craft - Choosing the Right Tool for the Job Landing Craft - Choosing the Right Tool for the Job ABSTRACT Nick Johnson, Jeremy Atkins BMT Defence Services, UK NJohnson@bmtdsl.co.uk Far from being simple ships [Ref 1] the design of landing craft poses

More information

ECO 199 GAMES OF STRATEGY Spring Term 2004 Precept Materials for Week 3 February 16, 17

ECO 199 GAMES OF STRATEGY Spring Term 2004 Precept Materials for Week 3 February 16, 17 ECO 199 GAMES OF STRATEGY Spring Term 2004 Precept Materials for Week 3 February 16, 17 Illustration of Rollback in a Decision Problem, and Dynamic Games of Competition Here we discuss an example whose

More information

DP Ice Model Test of Arctic Drillship

DP Ice Model Test of Arctic Drillship Author s Name Name of the Paper Session DYNAMIC POSITIONING CONFERENCE October 11-12, 211 ICE TESTING SESSION DP Ice Model Test of Arctic Drillship Torbjørn Hals Kongsberg Maritime, Kongsberg, Norway Fredrik

More information

APPLICATION NOTE: MARINE APPLICATIONS Trim, Roll and Leeway.

APPLICATION NOTE: MARINE APPLICATIONS Trim, Roll and Leeway. APPLICATION NOTE: MARINE APPLICATIONS Trim, Roll and Leeway. An Alternative VBOX Application Examples of Trim Angle effects Traditionally, the VBOX has been used by automotive markets but the wealth of

More information

Voith Water Tractor Improved Manoeuvrability and Seakeeping Behaviour

Voith Water Tractor Improved Manoeuvrability and Seakeeping Behaviour Amsterdam, The Netherlands Organised by the ABR Company Ltd Day Paper No. 2 9 Voith Water Tractor Improved Manoeuvrability and Seakeeping Behaviour Dr Dirk Jürgens and Michael Palm, Voith Turbo Schneider

More information

DUKC DYNAMIC UNDER KEEL CLEARANCE

DUKC DYNAMIC UNDER KEEL CLEARANCE DUKC DYNAMIC UNDER KEEL CLEARANCE Information Booklet Prepared in association with Marine Services Department 10/10/2005 Dynamic Under Keel Clearance (DUKC) integrates real time measurement of tides and

More information

4 ALBERT EMBANKMENT LONDON SE1 7SR Telephone: +44 (0) Fax: +44 (0)

4 ALBERT EMBANKMENT LONDON SE1 7SR Telephone: +44 (0) Fax: +44 (0) E 4 ALBERT EMBANKMENT LONDON SE1 7SR Telephone: +44 (0)0 7735 7611 Fax: +44 (0)0 7587 310 MEPC.1/Circ.850/Rev.1 15 July 015 013 INTERIM GUIDELINES FOR DETERMINING MINIMUM PROPULSION POWER TO MAINTAIN THE

More information

The OTSS System for Drift and Response Prediction of Damaged Ships

The OTSS System for Drift and Response Prediction of Damaged Ships The OTSS System for Drift and Response Prediction of Damaged Ships Shoichi Hara 1, Kunihiro Hoshino 1,Kazuhiro Yukawa 1, Jun Hasegawa 1 Katsuji Tanizawa 1, Michio Ueno 1, Kenji Yamakawa 1 1 National Maritime

More information

The Windward Performance of Yachts in Rough Water

The Windward Performance of Yachts in Rough Water 14th Chesapeake Sailing Yacht Symposium January 3, 1999 The Windward Performance of Yachts in Rough Water Jonathan R. Binns, Australian Maritime Engineering Cooperative Research Centre Ltd. (AME CRC) Bruce

More information

Offside. Judging Involvement in Play Ohio South Module A On-Line Intermediate Referee Recertification Training

Offside. Judging Involvement in Play Ohio South Module A On-Line Intermediate Referee Recertification Training Offside Judging Involvement in Play 2014 Ohio South Module A On-Line Intermediate Referee Recertification Training CJK 1999 World Cup Offside Scenario 2014 Mod A.ppt OFFSIDE VIDEO The following video is

More information

PROJECT and MASTER THESES 2016/2017

PROJECT and MASTER THESES 2016/2017 PROJECT and MASTER THESES 2016/2017 Below you ll find proposed topics for project and master theses. Most of the proposed topics are just sketches. The detailed topics will be made in discussion between

More information

Measurement Rules RG-65 CLASS

Measurement Rules RG-65 CLASS Measurement Rules RG-65 CLASS 2014 MEASUREMENT RULES RG-65 CLASS The RG-65 is a Radio Controlled monohull development class, where all isn t prohibited in these rules of measurement is allowed. MEASUREMENT

More information

Dynamic Stability of Ships in Waves

Dynamic Stability of Ships in Waves Gourlay, T.P. & Lilienthal, T. 2002 Dynamic stability of ships in waves. Proc. Pacific 2002 International Maritime Conference, Sydney, Jan 2002. ABSTRACT Dynamic Stability of Ships in Waves Tim Gourlay

More information

Launch Vehicle Performance Estimation:

Launch Vehicle Performance Estimation: Launch Vehicle Performance Estimation: John Schilling john.schilling@alumni.usc.edu (661) 718-0955 3 December 2009 Precise determination of launch vehicle performance typically requires the use of three-

More information

Deepwater Floating Production Systems An Overview

Deepwater Floating Production Systems An Overview Deepwater Floating Production Systems An Overview Introduction In addition to the mono hull, three floating structure designs Tension leg Platform (TLP), Semisubmersible (Semi), and Truss Spar have been

More information

THE WAY THE VENTURI AND ORIFICES WORK

THE WAY THE VENTURI AND ORIFICES WORK Manual M000 rev0 03/00 THE WAY THE VENTURI AND ORIFICES WORK CHAPTER All industrial combustion systems are made up of 3 main parts: ) The mixer which mixes fuel gas with combustion air in the correct ratio

More information

Two yachts, ten possibilities

Two yachts, ten possibilities NEW Oceanis 35.1 AND 38.1 Two yachts, ten possibilities Le Grand Large, Givrand, 13 JULY 2016 Beneteau will show the two new cruising yachts of the Oceanis range this autumn. These are a step further in

More information

Ma Long's forehand Power Looping Backspin Power looping backspin is the most common attacking method, and it is one of the most powerful forehand

Ma Long's forehand Power Looping Backspin Power looping backspin is the most common attacking method, and it is one of the most powerful forehand Ma Long s Technique Ma Long, the latest men-single winner in Asian games, has beaten lots of top players in the world. Characteristic of his game is obvious - very good at initiating attack, fast and fierce,

More information

NEW CLASSIC YACHTS - SY VELACARINA

NEW CLASSIC YACHTS - SY VELACARINA NEW CLASSIC YACHTS - CLAASEN SHIPYARDS NEW CLASSIC YACHTS - Classic Yachts with a modern twist The Dutch are known for their straightforward approach to life and business, and this is also reflected in

More information

Principles of glider flight

Principles of glider flight Principles of glider flight [ Lecture 2: Control and stability ] Richard Lancaster Email: Richard@RJPLancaster.net Twitter: @RJPLancaster ASK-21 illustrations Copyright 1983 Alexander Schleicher GmbH &

More information

SD2706. Sailing for Performance Objective: Learn to calculate the performance of sailing boats

SD2706. Sailing for Performance Objective: Learn to calculate the performance of sailing boats SD2706 Sailing for Performance Objective: Learn to calculate the performance of sailing boats Predict Performance - Velocity Prediction Program Wind: -speed -angle Boat data Performance: - Speed - Heel

More information

Agood tennis player knows instinctively how hard to hit a ball and at what angle to get the ball over the. Ball Trajectories

Agood tennis player knows instinctively how hard to hit a ball and at what angle to get the ball over the. Ball Trajectories 42 Ball Trajectories Factors Influencing the Flight of the Ball Nathalie Tauziat, France By Rod Cross Introduction Agood tennis player knows instinctively how hard to hit a ball and at what angle to get

More information

MSC Guidelines for the Submission of Stability Test (Deadweight Survey or Inclining Experiment) Results

MSC Guidelines for the Submission of Stability Test (Deadweight Survey or Inclining Experiment) Results S. E. HEMANN, CDR, Chief, Hull Division References a. 46 CFR 170, Subpart F Determination of Lightweight Displacement and Centers of Gravity b. NVIC 17-91 Guidelines for Conducting Stability Tests c. ASTM

More information

TUNE YOUR SAILS SPEED

TUNE YOUR SAILS SPEED TUNE YOUR SAILS FOR OUTRIGHT SPEED J/70 Tuning Guide Rev. R02 After countless hours sailing, testing and competing in the J/70 One Design, North Sails has updated our tuning notes and tips in an effort

More information

Maximum Rate Turns. Objective To carry out a balanced, maximum rate, level turn using full power.

Maximum Rate Turns. Objective To carry out a balanced, maximum rate, level turn using full power. Advanced Manoeuvres Maximum Rate Turns To achieve the maximum rate of turn, the greatest possible force toward the centre of the turn is required. This is achieved by inclining the lift vector as far as

More information

Advanced Hydraulics Prof. Dr. Suresh A. Kartha Department of Civil Engineering Indian Institute of Technology, Guwahati

Advanced Hydraulics Prof. Dr. Suresh A. Kartha Department of Civil Engineering Indian Institute of Technology, Guwahati Advanced Hydraulics Prof. Dr. Suresh A. Kartha Department of Civil Engineering Indian Institute of Technology, Guwahati Module - 4 Hydraulics Jumps Lecture - 4 Features of Hydraulic Jumps (Refer Slide

More information

Perceived Temperature & Thermal Danger Level Determine the atmospheric temperature. Adjust for wind chill. Adjust for altitude. Adjust for humidity.

Perceived Temperature & Thermal Danger Level Determine the atmospheric temperature. Adjust for wind chill. Adjust for altitude. Adjust for humidity. Cold, Windchill, & Altitude Effects Rules For The Adventurer s Club Campaign By Mike Bourke Wind chill: Methods of determining wind chill are different from country to country and have also changed over

More information

Long and flat or beamy and deep V-bottom An effective alternative to deep V-bottom

Long and flat or beamy and deep V-bottom An effective alternative to deep V-bottom Boat dual chines and a narrow planing bottom with low deadrise Long and flat or beamy and deep V-bottom An effective alternative to deep V-bottom Here is a ground-breaking powerboat concept with high efficiency

More information

An innovative windvane pendulum system for sailing boats with outboard rudders.

An innovative windvane pendulum system for sailing boats with outboard rudders. An innovative windvane pendulum system for sailing boats with outboard rudders. Jan Alkema 26 sept. 2005 figure 8. The oar blade retracted figure 7. The oar blade in the water Preface On boats with outboard

More information

Lift for a Finite Wing. all real wings are finite in span (airfoils are considered as infinite in the span)

Lift for a Finite Wing. all real wings are finite in span (airfoils are considered as infinite in the span) Lift for a Finite Wing all real wings are finite in span (airfoils are considered as infinite in the span) The lift coefficient differs from that of an airfoil because there are strong vortices produced

More information

Queue analysis for the toll station of the Öresund fixed link. Pontus Matstoms *

Queue analysis for the toll station of the Öresund fixed link. Pontus Matstoms * Queue analysis for the toll station of the Öresund fixed link Pontus Matstoms * Abstract A new simulation model for queue and capacity analysis of a toll station is presented. The model and its software

More information

Numerical Analysis of Wings for UAV based on High-Lift Airfoils

Numerical Analysis of Wings for UAV based on High-Lift Airfoils Numerical Analysis of Wings for UAV based on High-Lift Airfoils Sachin Srivastava Department of Aeronautical Engineering Malla Reddy College of Engineering & Technology, Hyderabad, Telangana, India Swetha

More information