Puzzler: How Do You Figure The Shaft Angle??

[Rick D]

I am part owner of a 1915 launch. We recently pulled the shaft and prop because of a lot of vibration. To make a long story short, the prop and shaft are toast due to electrolysis. The shaft log, upon which I was going to place a PSS seal is also shot. Shaft logs rest upon the keelson and provide the pathway for the shaft. The one on this craft is about 18" long and 3 1/2" wide. My concern is that they are available in a variety of shaft angles. It looks very shallow, but I would like some help from somebody to determine a method to calculate the angle provided by the box. Any wood boat folks have an idea? (PS: the front of the log that accepts the stuffing box bellows is shot, so I cannot use it for measurements.) Thanks in advance... Rick Dinon

 

[Rich Stidger]

How about this-

I assume that the shaft and the engine are in-line with each other. If so, -Using a 2-foot carpenter's bubble level and a protractor, measure the angle of the engine bed by resting the level at one end and either holding or shimming the other end until the level is horizontal. Then measure the angle of the level with the mounting plane of the engine bed.This will give you the *relative* angle of the bed to the *true* horizontal.Now, since the boat is on land and is *not* perfectly level, perform the same measurement on some convienent vertical or horizontal surface on the boat. This surface should be known to be truely vertical when the boat is in the water. I would choose a vertical bulkhead. This measurement will tell you the true angle of the boat as it sits on land.By adding or subtracting these two angles, you can arrive at the shaft angle.Rich

 

[Mike DiMario]

opposite over adjacent

Rick,Can you measure the length and the drop? If so, the drop divided by the length equals the Tangent of the angle. A trig table will do it. Something tells me it is not this simple!I have used a 2 foot level and measured the drop in 2 feet. If you have two different angles the keel and the prop angle, measure the drop/rise in each individually and then add them together.hope this helps!Mike D