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Old 19-09-2015, 20:48   #1
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St Francis 44 MkII Diagonal Sail Drive

So... I was once again lustily looking at Yacht World after watching Hugh Howey's latest video of his new SF 50 "Wayfinder", and was checking out some SF 44 MKII's. They have a very odd sail drive set up, so here I am asking for some info on the pros and cons of their diagonal sail drive set up.



I know St Francis likes to center the weight with motors, batteries and tankage positioned mid ship, and it seems like a clever design, as it would be easy to beach, but wouldn't it leave the sail drives exposed to collision with anything that might happen along between the hulls?

You don't see this configuration very often, so there must be a reason. What are your thoughts? Good design, obsolete nonsense, or something in between?

Here is another pic for reference.

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Old 20-09-2015, 01:58   #2
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Re: St Francis 44 MkII Diagonal Sail Drive

For sure they would be more exposed to large floating but partially submerged objects passing under your bridge deck. But, the benefit of keeping the weight forward is a big one. Many st Francis 44's have circumnavigated and I have never heard of any problems.
The Gunboat 62's were done the exact same way, not sure about later models. On the Gunboat it was also important the have them cocked to prevent them being the lowest point as she has dagger boards and retractable rudders. This is not part of the benefit on the 44 as she has keels.


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Old 20-09-2015, 08:21   #3
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Re: St Francis 44 MkII Diagonal Sail Drive

Quote:
Originally Posted by Red Herring View Post
I know St Francis likes to center the weight with motors, batteries and tankage positioned mid ship, and it seems like a clever design, as it would be easy to beach, but wouldn't it leave the sail drives exposed to collision with anything that might happen along between the hulls?
A couple observations:

Sail drives are not very heavy. I just replaced the rubber bellows/boots on mine so I had a good chance to learn just how light they are, removed from the transmissions. Centering the engine weight, however, seems a good design feature notwithstanding the high difficulty of removing/reinstalling centered engines vs those in stern "engine rooms" through hatches. (I have photos of an engine on my boat (from the previous owner) being rigged out and reinstalled through the normal stern access hatch. No major surgery required.)

A shaft drive makes more sense to me with a centered engine position and probably has negligible weight differences vs a saildrive. Further, with the angled saildrive you lose whatever advantage that might have existed with prop wash over the rudders.

On a boat with LAR keels it seems unnecessary to expose the saildrive inboard as beaching should be achievable because of the keels.

So unless I'm missing some other advantage of this angled saildrive installation, it seems to be the only solution available from a poor decision to center the engines but insisting on saildrives vs shafts.

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Old 20-09-2015, 11:19   #4
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Re: St Francis 44 MkII Diagonal Sail Drive

I would think shafts would be a better alternative as well. Maybe not as quiet, but certainly simpler.

Quote:
Originally Posted by 2Hulls View Post
A couple observations:

Sail drives are not very heavy. I just replaced the rubber bellows/boots on mine so I had a good chance to learn just how light they are, removed from the transmissions. Centering the engine weight, however, seems a good design feature notwithstanding the high difficulty of removing/reinstalling centered engines vs those in stern "engine rooms" through hatches. (I have photos of an engine on my boat (from the previous owner) being rigged out and reinstalled through the normal stern access hatch. No major surgery required.)

A shaft drive makes more sense to me with a centered engine position and probably has negligible weight differences vs a saildrive. Further, with the angled saildrive you lose whatever advantage that might have existed with prop wash over the rudders.

On a boat with LAR keels it seems unnecessary to expose the saildrive inboard as beaching should be achievable because of the keels.

So unless I'm missing some other advantage of this angled saildrive installation, it seems to be the only solution available from a poor decision to center the engines but insisting on saildrives vs shafts.

Dave
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