St Francis 44 MkII Diagonal Sail Drive

[Red Herring]

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.

[Dave852]

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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[2Hulls]

Originally Posted by Red Herring

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.

Dave

[Red Herring]

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

Originally Posted by 2Hulls

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

[Warren149]

Shaft drive is heavier than 'sail drives" and are considerably more expensive to install. Builders are going to use a saildrive whereever possible to save cost.simple.
The angled sail drive on the st Francis gets the weight in the right places, it actually will catch crab pots less as most lines come from the outside
it also allows the boat to stand on the ground without additional supports Very valuable to a cruiser.
Having recently raced on a st Francis 44 I can report it works very well.
Cheers Warren
Short video here
https://youtu.be/nITygmH8NsY

[Triumphant]

Another advantage is that as the props are closer to the surface it is much easier to clean them or clear them.

[ggray]

Originally Posted by Warren149

, it actually will catch crab pots less as most lines come from the outside

How so?

[Intentional Drifter]

Having owned a SF 44 for 5 years and cruising on her for two, I know these boats well. I thought the placement of the engines and saildrives to be one of the several ingenious things about these boats.
It's all about the balance of probabilities regarding situations you are more and less likely to encounter and the advantages given with such a placement.

The advantages:
1. Optimal weight distribution of the engines (not so much the saildrives as they don't weight all that much) in the center of the boat. This lessens hobby horsing.
2. By having the engines/drives in the center, the aft hull shape allows for a much cleaner water exit with slender transoms. You only get this advantage so long as you keep added weight well trimmed! If you stow a lot of heavy stuff aft without trimming your boat well, you will lose this advantage. The SF has narrow hulls and that improves performance, but you must also watch for added weight to the boat.
3. Cavitation in choppy conditions is pretty much eliminated as the center of the boat always stays in relatively quiet water.
4. Putting people in the water or getting them out from the transoms while having the engines engaged is much safer. You simply cannot safely do that with engines aft. You can with the SF 44. You still don't want to do that, but it's much safer if you must.
5. The design greatly minimizes the likelihood of fouling the props with lines in the water, as they are more likely to be on the outside of the hulls or trailing from aft.
6. Although any cat with twin screws will be relatively easy to maneuver in close quarters, having the screws in the center of the boat makes it even easier. In quiet water you can literally put one engine forward, the other in reverse and spin around in a circle. There have been some tight fairways when I miscalculated my approach and this was quite nice to have.
7. With the exception of something coming straight down the middle between the hulls, which of course requires that you be steering directly for it, the props are better protected especially from groundings. BTW, the keels in the SF 44 are "sacrificial" in that if you ground hard and crack one open, salt water will contaminate the water tank on that side, but is much less likely to enter the boat. Of course, you've lost a water tank, but hopefully you still have the other and you will have not hit on the sail drive, dislodged it at the mount and then have water pouring into your boat.
8. Daily servicing can be done from inside and not hanging out on a transom. This is also nice when you've been in some chop and a fuel filter has clogged, or you've broken a water pump impeller, or lost a belt, etc. You can get to all those bits quickly and easily and without exposing your butt to the weather or seas.

Disadvantages:
1. The cowlings for the engines intrude in the starboard passageway and the port galley. Yeah, you "get used to it" but I'd still rather not have the intrusion. We modified the galley countertop to lift up over the engine which made the daily checks much easier.
2. Minimizing engine noise is more difficult in those positions as you don't have the noise insulation from your bedding, etc to help. Hence, engine noise when under way is more. We replaced the sound insulation in the cowlings to something better (sorry, I don't recall what we used) and that helped a fair bit.
3. Engine heat after you're done. The blowers do a good job of pushing that outside when under way, but when you've stopped for the day, the engines keep radiating. That isn't much of a deal (at least to us) and can be an advantage if you're in a cooler clime.

SF 44's are great boats if you're looking for more of a performance oriented cruiser but don't have the budget for Outremer or Catana. Well built, can sail very well, yet still quite comfortable so long as you aren't over 6'1". The headroom is low for taller people. People like to criticize them for their relatively lower bridgedeck clearance, but that also reduces windage and lowers the center of gravity. The bridgedeck is shaped in such a way that pounding isn't a big deal and all cats will pound in some conditions.

Hope this helps.

ID

[Warren149]

Originally Posted by ggray

How so?

All cats will be exposed to crab pot a lot more because they are so wide. If a bouy runs down the outside of the hull or you turn to leeward just before you run over a pot bouy you can let it run down the outside of the hull and miss the saildrive as it’s inboard , a more normal vertical drive will catch more. If you drift down on a crab pot bouy it’s the same as the same as the the same as windward side!