Strange engine setup

[chuck53]

Has anyone ever seen anything like this before? The shaft comes out of the boat at an angle of at least 10 degrees to the side. I've never seen anything like this and can't understand any purpose of doing it this way.

100_0148.jpg picture by chuck53 - Photobucket

[dabnis]

Chuck,

Many years ago, my dad had a wooden boat with the same
arrangement. My guess is that the engine was added at a later
time and they didn't want to cut into the keel, or as in the boat pictured,
the skeg & rudder assembly? Looks like perhaps that boat wasn't
designed for an inboard and it was added later?

dabnis

[mdbee]

Type of boat? Custom? Original set up? Wood hull?

Might compensate for prop walk

[JiffyLube]

That's the weirdest setup I've ever seen...must have been on drugs when they they thought that one up.

[chuck53]

When I saw the boat, I was so shocked at what I saw, I didn't pay any attention to any other details of the boat. But I seem to remember the boat being a little too big and not set up for an outboard. Next weekend when I go to the marina, if the boat is still there, I'll get more details.
It looked like a production boat - not built in someone's back yard and it didn't look like a real racer that wouldn't have an engine at all.

[msmith10]

Actually many of the older C&Cs are like that. My '77 30-mk1, with an Atomic 4, is like that. If the purpose was to counteract for prop walk, it wasn't very successful. In the case of the boat pictured, I suspect it was to avoid having the prop shaft exit the hull at an extreme downward angle.

[SlowButSteady]

I've seen a couple of other boats with an off-set prop like that. I think the idea is to have the shaft angled out to port a bit to counter the tendency of an off-set prop on the port side to yaw the boat to starboard, and to allow placing the engine along the centerline of the hull. Of course, under sail the drag would make the boat yaw a boat to port a bit.

As to why they didn't just install a shaft log along the center line, besides the possible easier installation (since you don't have to drill through the keel itself), if you look closely this set-up allows for greater prop clearance w/o having to angle the the shaft down at a much greater angle. Its a trade-off that might well make sense in some designs.

Edit: D'oh!! msmith beat me to it by one minute!! (I gotta start typing faster.)

[funjohnson]

My Sabre has this... all of them did until the 90s. It's for the reasons listed above. I just worry about it getting ripped off by something.

[chuck53]

I had thought about the downward angle part but many boats have a deep downward angle and we're talking about a sailboat - not a go-fast. And I would think the drag on the prop would be worse under sail. So maybe a little faster under power but a little slower under sail.

[JonEisberg]

Originally Posted by chuck53

Has anyone ever seen anything like this before? The shaft comes out of the boat at an angle of at least 10 degrees to the side. I've never seen anything like this and can't understand any purpose of doing it this way.

100_0148.jpg picture by chuck53 - Photobucket

Looks like an 80's vintage Sabre to me...

Roger Hewson did that with a number of his designs back then, according to the Sabre they "implemented the left offset propeller to diminish the effect of torque created by the rotation of the propeller. This design also allowed propeller shaft removal without necessitating removal of the rudder."

I've never run one, so I can't say... but I would imagine it would also reduce the buffeting effect of the propwash on the rudder to a certain degree, as well... Always looked like they went slightly overboard with the concept to me, however, that's a pretty serious angle, and must involve a significant loss of forward thrust...