Riviera Draft Shaft Hole Boring

Transcription

1 Riviera Draft Shaft Hole Boring

2 a. Height from bottom of hull thru the hull to the center of the drive shaft. This will be calculated. b. Height of drop of strut. The strut for the Riviera is 7.5 c. Distance from rear of hull to center of rudder shaft. This is set at 6 per the plans. d. Distance from center of rudder shaft to front of strut. Adding 1 clearance between strut and prop, prop collar thickness, 1 for prop nut and space to take prop off (estimated at 3 ). Be sure to add the distance from center of rudder shaft to rear most point of rudder. The rudder I am using measures 2.5 from center of rudder shaft to rear edge. For my purposes, I needed 8 inches clearance between the strut and rear edge of the rudder. I determined to set this at 10. e. Distance from strut face to entry into hull as measured on center line of shaft Using an online calculator to determine the distances. The calculator can be found at In this measurement, I am using the 7.5 drop on the 16* strut to get the measure from face of strut to entry point in hull. The entry point measure is c or This is my e measurement on my engine drawing. Thus: c = 6 from rear of transom to center of rudder shaft

3 d = 12.5 : 2.5 (center of rudder shaft to rear edge of rudder) + 3 (clearance for prop removal) +1 (nut) + 3 (prop collar) + 1 (space clearance between prop and strut face) + 2 (just because) e= distance from face of strut to shaft entry as measured on centerline of shaft Total of distance from transom to shaft entry hole. I then wanted to verify the engine location to verify position between the frame members. To get the distance between the center line entry hole into the hull and middle of flange on rear of engine, I had to reverse some calculations on the calculator. I estimated my shaft at 10 coming out of the keel to the rear of the engine. This is a combination of the length of the shaft log, shaft bearing, thickness of the shaft mounting flange plus giving myself 2 extra between the flange face and shaft bearing. The calculator showed that my hole measured 8.16 thru the hull. This gives me a shaft length from the entry hole to the face to transmission at Thus, the measurement from the entry hole center line to face of transmission is 17.45

4 This is the f value in my original drawing So bringing it all together to determine the engine location From the original drawing C= 6 D= 12.5 E= F= Total from transom to face of transmission is perfectly fits in the engine compartment between the frame members

5 I cut a 4x4 block of wood to receive the drill bit and direct it cleanly into the hull. The face of the block was cut at 16 angle so that it was square with the line of the drill bit. I also cut the bottom of the block so that it fit over the angle of the keel at the anticipated point on the hull. The bottom measured about 8 degrees sloping in both directions from the keel. The cut was made on the table saw. I am working on the hull prior to final fairing in preparation for fiberglass.

6 On the face of the block I drew a 1 diameter circle and located the center. This was to emulate the drive shaft. The bid I will be using is a 1 ¾ Forstner bit so the circle was raised about ¾ from the bottom of the block to clear the hull at the this entry point. I used a spare batten for preliminary lineup. Remember, the block has to move forward from the expected entry point of the shaft into the hull.

7 I then insured my strut was in position and used a framing square to line up the center line of the shaft with the hull location measurement.

8 Checking to make sure my angles are right using an inexpensive angle finder from Lowe s. The keel has a little more than a degree rise from from the transom going forward so I expected the angle finder to show about 15 degrees. The strut is 16 but setting on the keel which lowered the angle closer to 15 degrees.

9 Time to flatten the area for the strut to be mounted. Since the Riviera has a relatively flat bottom near the transom, I did not feel it necessary to route a spot for the base of the strut and simply flattened the area with a belt sander. Any minor deviation in the sanding will be remedied with thickened epoxy. The sanding effectively lowered the position of the strut on the keel by about ½ inch. I recalculated how this effected the position of the entry hole and position of the engine. It shortened the distance by 1 ¾. This is great for it moved my engine rearward. I needed all the room I can get.

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11 Setting the strut in the flattened area and checking the angle again. Here I am using the drill bit extension rod to hold the magnetic angle finder. The extension is only 5/8 in diameter so I had to insert a wedge to center it in the shaft. The angle is good.

12 Time to set everything up. I purchased an inexpensive rotating lazer from Lowes for about $60. I set it up on the transom straddling the keel over the rudder location. This allowed me to shoot a line down the strut, across the block and down the keel line to insure everything lined up. The drill is a 1 ¾ Forstner bit with 2 18 extensions. This was sufficient length to get me thru the hull and keel. The Forstner bit is hard work but it cleans as it goes. A hole saw is faster drilling but you have to stop and clean out the plug with a chisel every inch or so. Once the Forstner bit breaks thru the keel inside it will lock up. I used a hole saw to finish the hole all the way thru. It was simple to climb under the boat and break out the plugs at this point rather than working from inside the bored hole.

13 Everything was fastened down. I used the strut to guide the drill extensions. The strut was screwed down to prevent moving. I did not drill the mounting holes at this time in the event something changed. The block as strapped down and 1 screws were set at each corner. I made sure the screws were out of the alignment of the drill bit. I found a piece of 1 aluminum rod to emulate the shaft and lined up the circle on the block perfectly. I wooden rod would have worked just as well.

14 One last check with the lazer and angle guage to make sure everything is lined up. Time to drill.

15 Hole Drilled. Upon cleaning up, the measure mark on the hull where the shaft center was anticipated was dead on the mark. Now time to clean the hull completely and fiberglass. I fiberglass insert will be made later when I have the engine and drive shaft so that everything has plenty of clearance. Some chips on the edge of hole did break loose which will be restored with the fiberglass work. Total time: About 2 1/2 hours including calculations Total cost: $180 including lazer, drill bits (both hole bit and forstner bit), two 18 drill bit extensions, and angle gauge. Everything was purchased at Lowe s and nothing had to fabricated. I am a simple guy and just do things with common sense. This was inexpensive and rather quick. Some purists would take objection to my methods but it worked so what can I say. Please pardon the work in progress on the hull. The final product will be much nicer looking than this. However, in all construction, the ugly stage is just prior to the final product. David V. Lott