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offset propeller shaft

Mark F

Contributing Partner
Blogs Author
Do I remember correctly that the propeller shaft on my 1976 E27 is offset to port?
 

Dave Hussey

Member III
This is a picture of my 78 (oops, it's a 76) E27..note that the shaft is off center to starboard...this is great if you have a RH propellor, but a bear if it is LH like mine...it requires a lot of helm :esad:to go straight at full throttle.
 

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Mark F

Contributing Partner
Blogs Author
Thanks Dave,

I've got a right hand prop and I thought I remembered the shaft being off set to port. I'm having lots of fun backing out of a tight slip due to the prop walk to port (not really). I was thinking if I changed to a left hand prop it might help. What engine do you have that requires a LH prop?
 

Dave Hussey

Member III
I've got a Volvo MD6B diesel. I hate backing up...mine is completely uncontrollable. I've spent hours trying different tactics to maneuvre around a bouy, and if I learned anything from it, it is to avoid it..at least you can rely on the prop wash and use it to your advantage to kick the stern to starboard. What do you have for power?
Mark I just noticed you are from Felton. I lived in Santa Cruz in the 70's. Very sad to hear about those recent fires. I hope you made it through OK.
 
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Mark F

Contributing Partner
Blogs Author
I have a SolidNav 48 volt electric motor that I am finishing up the install on. It is setup for a RH prop right now but it's not too difficult change the direction of the motor. I'm pretty sure my prop shaft is offset to port and I was thinking if I had a LH prop it might help with prop walk. At least the prop wouldn't start out pointed in the direction of the walk. It's been a bear to back out of my slip. Although, last time out I tried steering toward the prop walk (steering to port in reverse), giving the motor maybe half throttle for a few seconds then slowly turned the wheel to starboard, it worked (that time anyway). My thought was to get some flow over the rudder and then make my turn. I have about 2 boat lengths to get the stern headed in a starboard direction!

What's nice about the electric motor is once the stern starts to back to starboard I can jamb it into forward and make a quick turn to port. The immediate torque and power is great.

So far we've been ok with the fires, although the Boony Doon fire was a bit too close.
 

Dave Hussey

Member III
When you are going forward at full throttle, do you require any helm compensation to maintain a straight course, or is the rudder amidships? Mine (a tiller) requires a considerable amount of port helm (tiller to starboard) to just go straight! What a DRAG litteraly...I bet I'd gain a knot or two if I didnt need to counter steer. I am planning on installing an auto pilot, and I bought a series 31 deep cycle battery to power it due to the extra constant current drain it will cause.

Is the 30 foot tall "man" still standing along the hiway 9? The sculpture made out of redwood laminated scraps and fiberglass resin...I interviewd and photographed the artist for the college news paper (Cabrillo)
 
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Dave,
A very long time ago I had a similar problem, but not with the severity you describe. When the boat was out of the water I had my rudder faired. Frankly, I do not know if it was the rudder shaft that was not true, but the fairing helped a lot. It strikes me that are facing a similar type of problem, which is fixable. Permanently.
Morgan Stinemetz
 

Dave Hussey

Member III
I would like to try fairing mine. Did you add a lot of material to one side to change the foil shape, and in doing do, create more lift on that side?
 
Dave,
I don't have those kind of skills or that kind of time. I had it done professionally at the boat yard where I keep my boat. All I know is that it worked. If you want to know how well, in the 20+ years I raced my boat after that, we failed to get a podium finish maybe 5 times. I am pretty much retired from racing now.
Morgan Stinemetz
 

Dan Morehouse

Member III
While having my bottom painted last week, I noticed for the first time that my prop shaft is also offset. Mine appears to be offset to port; and by "offset", I mean not parallel to the centerline of the boat. Because of the hull shape of the E-38 at the point where the shaft exits, it is difficult to tell if the shaft exits at centerline, or to one side or the other; but the shaft is definately set at an angle skewed in relation to the centerline. The picture Dave posted of his shaft seems to show it definately exiting the hull to starboard of the centerline. But is it also skewed, or is it parallel to the boat centerline? How about anyone else's?

Mine has a fixed right hand two blade prop, and exhibits fairly generous prop walk to port in reverse. It does seem that a port offset would cancel the prop walk generated by a left hand prop in reverse...and that a port offset would also aggravate the same prop walk generated by a right hand prop in reverse. Which leaves one wondering...what design advantage was being pursued that was more pressing than the disadvantage presented by coupling a port shaft offset with a right hand prop?

Dan Morehouse
1981 E-38 "Next Exit"

P.S. in order to maintain a straight course while backing once sternway is established, I have to position the top of the wheel at 3:00. Anything less than that allows the stern to begin a turn to port.
 

rwthomas1

Sustaining Partner
Dan,
My E38 is exactly the same way. I am guessing the main reason the shaft is offset is to allow the shaft to be removed with the rudder in place. The other trick I use to back up straight is to give a good shot of throttle to get her moving and then take it out of gear. Once you have a little headway the rudder responds better without the prop turning/walking. RT
 
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