Engines with sail drive position

[Nidnoi_V]

Hi All
My question might be strange however here it comes if you place the Sail drive more midship “possible with Electric engines “due to size.”
what would be the downside/ benefit?


I do not see much downside to it besides it might be harder to turn due the distance from the rudder if by engines.

[Tin Tin]

Some older style cats have mid engined diesel sail drives - (St Francis?), from years ago. Electrics might solve this problem, but the main reason for disliking mid mount diesels was accessibility for service and the stink they leave inside the boat, which often is an issue with shaft drives - nothing to do with steering.

[tkeithlu]

Hmmm. What's the power source for these electric saildrives? Unless you've got bunches of solar plus bunches of batteries, there's going to need to be a genset in there somewhere. Two 10 HP motors means a theoretical 27 KW genset, with the practical one being bigger than that, assuming that you want full power.

As for the rig itself, you've moved the center of thrust to midships, rather than in the stern. That might well pivot the hull better, as long as you are steering by differential engine thrust. On the other hand, steering with the rudders likely suffers, because you are no longer directing prop wash against the side of the rudder.

[deblen]

Originally Posted by Nidnoi_V

Hi All
My question might be strange however here it comes if you place the Sail drive more midship “possible with Electric engines “due to size.”
what would be the downside/ benefit?


I do not see much downside to it besides it might be harder to turn due the distance from the rudder if by engines.

If your propellor is more than 1/2M / 20" from the leading edge of your rudder,You will have poor steering control while under power IMHO.
Cheers/ Len

[ggray]

I wouldn't like that big hole down low in the middle of my boat....

[tkeithlu]

Good thought, ggray. Reference the problems people bring to the forum regarding the gaskets around sail drives...

[ggray]

Actually, I'm not sure how frequent a problem with the diaphragms is, considering how many of these things are out there. It certainly would ruin your day though if it happened

But the potential is there, exacerbated by how vulnerable the saildrive is to an impact. I prefer mine hiding behind the keel. And in a small compartment separate and watertight from the rest of the boat. And an oversized bilge pump to boot.

An aside, irrelevant to the question, but speaks to the toughness of the diaphragms. Years ago, while one engine was out for a rebuild, I was determined to go out for a couple days. While sailing along, looked down into the empty engine bed, and boy was the saildrive moving around! Well, there was one engine mount keeping it from falling out! I don't think I would do this again.

[UFO]

Originally Posted by deblen

If your propellor is more than 1/2M / 20" from the leading edge of your rudder,You will have poor steering control while under power IMHO.
Cheers/ Len

Well that depends on if you have 1 or 2 engines - My rudders are behind my saildrives so zero from the prop in forward - You can quite easily maneuver with the 2 engines alone in close quarters.


This setup is far from perfect though, with reversing (Max Props) creating and unpleasant amount of wash over the rudders. The benefit though is that the engines are in their own compartments and not under the rear bunks, which for me and a live aboard is a big no.

[Factor]

Originally Posted by ggray

I wouldn't like that big hole down low in the middle of my boat....

Not such an issue if it is a properly designed and built cat, it would be unsinkable. There are however some production cats that will sink just as well as a Mono.

[Factor]

Originally Posted by UFO

Well that depends on if you have 1 or 2 engines - My rudders are behind my saildrives so zero from the prop in forward - You can quite easily maneuver with the 2 engines alone in close quarters.


This setup is far from perfect though, with reversing (Max Props) creating and unpleasant amount of wash over the rudders. The benefit though is that the engines are in their own compartments and not under the rear bunks, which for me and a live aboard is a big no.

with engines behind rudders there is also the large negative of having all the weight aft, not a good thing on a multi,

[UFO]

Originally Posted by Factor

with engines behind rudders there is also the large negative of having all the weight aft, not a good thing on a multi,

Correct, but still a worthwhile payoff to get them out of the rear cabins IMHO.



That's one of the advantages of not having a performance cat - They are built to take the weight and create the living space, albeit at the expense of performance Although on the bigger crossings I still average 150 miles per day, a long way off 200, but still acceptable.

[ggray]

Originally Posted by Factor

Not such an issue if it is a properly designed and built cat, it would be unsinkable. There are however some production cats that will sink just as well as a Mono.

Yeah, that's what they say, and I'm confident mine is "unsinkable", but I think it is still an issue if the sterns are down from the weight of the engines and the deck is awash. But I'm still floating!

No, I would not say it's not an issue. Just because it could be worse doesn't make it a happy situation!

[skipperpete]

Originally Posted by Nidnoi_V

Hi All
My question might be strange however here it comes if you place the Sail drive more midship “possible with Electric engines “due to size.”
what would be the downside/ benefit?


I do not see much downside to it besides it might be harder to turn due the distance from the rudder if by engines.

I had a bit to do with a Knysna cat that carried her engines amidships, one under the galley, the other under a workbench. The saildrives were rotated one bolt hole on the flywheel housings and they angled towards each other between the hulls. Its an unusual arrangement but has worked flawlessly for many years. She was a bit different to dock, a little slower to turn but rotated better than other cats I’ve operated.
The engines were easy to work on and the compartment could have possibly been made watertight by enclosing the engine in a sort of a low sided “tub”..... although that would mean sacrificing accessibility quite a bit, however the breaching of a saildrive diaphragm would be less of a crisis.
Pete.

[Nidnoi_V]

Originally Posted by ggray

Actually, I'm not sure how frequent a problem with the diaphragms is, considering how many of these things are out there. It certainly would ruin your day though if it happened

But the potential is there, exacerbated by how vulnerable the saildrive is to an impact. I prefer mine hiding behind the keel. And in a small compartment separate and watertight from the rest of the boat. And an oversized bilge pump to boot. .

(when it comes to have the Sail drives hidden behind the Keel in my case wont make any difference since i will have daggerboard and not mini keels
so they will be exposes no matter what)

[Nidnoi_V]

[QUOTE=tkeithlu;3378174]Hmmm. What's the power source for these electric saildrives? Unless you've got bunches of solar plus bunches of batteries, there's going to need to be a genset in there somewhere. Two 10 HP motors means a theoretical 27 KW genset, with the practical one being bigger than that, assuming that you want full power. QUOTE]

To answer your question my Idea is the following.
2 kraeutler SDKH-ED 15,0 AC these can turn 360 degrees which hopefully mean I can avoid to have a bow thruster) placed roughly midship in each hull
Batteries located under the bed aft “yes will lose some storage space there “
In the “old engine rooms having a Fischer panda AGT-DC 10000
The total weight of this system will be 840 KG
And that ill give me enough sailing time on batteries for roughly 4-5 hours at 4-5 knots depending on Sea stake.
If I compared that with Yanmar HJ57, Bow thruster and a Generator that will be 1160 KG
So I will save 280 Kg in total
However, regen will come partly from Solar power around 3000-3500 watts “when at anchor more than enough even in the Nordic region for daily usage “ and of course also when sailing due to regen