Need to lift my stern out of the water a little. Pillows?

[Chotu]

Originally Posted by boatpoker

Sounds like the anticavitation plate being level with the hull and vacuum created by the prop could be pulling more air down what essentially is a tunnel. I still think it should be below the hull.

I think I have had a problem with that the whole time. I’ve done 1000 nautical miles on this boat as configured.

I definitely was sucking some air because I have the gouges in the lower unit to prove it. There are some gouges along the sides of the lower units right where they exit the hull.

This might be one of those rare cases where you have one problem at first, then you are able to fix two problems with one solution.

[boatpoker]

Originally Posted by Chotu

Speaking to everyone else participating right now, the consensus is I’m good to get rid of the anti-cavitation plate? And put the rubber mat system in so that it plugs up the hole when the Outboards are deployed?

I would say saildrive design supports this idea.

They don’t have much in the way of anti-cavitation plates at all. But they do not have a hole above them.

Agreed.

[Madehn]

is it possible to grind off part of the cavitation plate and then bolt a piece of rubber to what remains to give yourself a bit of "flexible" cavitation plate that will bend enough to fit up and down the hole yet still seal and provide cavitation protection?

[rslifkin]

Originally Posted by Madehn

is it possible to grind off part of the cavitation plate and then bolt a piece of rubber to what remains to give yourself a bit of "flexible" cavitation plate that will bend enough to fit up and down the hole yet still seal and provide cavitation protection?

That would be possible, but plugging up the hole will give a bigger benefit. And once that's done, the anti-vent plate on the outboard won't really be doing anything, as there's no source of air for it to isolate (being that it's under the hull).

[Chotu]

Originally Posted by rslifkin

That would be possible, but plugging up the hole will give a bigger benefit. And once that's done, the anti-vent plate on the outboard won't really be doing anything, as there's no source of air for it to isolate (being that it's under the hull).

I definitely agree with this.

Do you want to know how fast I am moving on all of this stuff?

Already went to tractor supply and got a big thick heavy rubber mat.

About the only thing I’m worried about at this point is the outboard well filling up with cooling water. But there should still be enough water transfer I think even with the mat that the cooling water will leave the outboard well.

[rslifkin]

Originally Posted by Chotu

I definitely agree with this.

Do you want to know how fast I am moving on all of this stuff?

Already went to tractor supply and got a big thick heavy rubber mat.

About the only thing I’m worried about at this point is the outboard well filling up with cooling water. But there should still be enough water transfer I think even with the mat that the cooling water will leave the outboard well.

A couple of small holes in the rubber (towards the trailing edge) would fix that problem if it shows up.

[Chotu]

Originally Posted by rslifkin

A couple of small holes in the rubber (towards the trailing edge) would fix that problem if it shows up.

That’s true. I wonder if those could work the same as the automatic bailing things on power boats.

Those work because the deck is above the water line though, right? Like they don’t actively pull water out because of the motion of the boat if it’s below the waterline right?

Because it sure would be cool if I could pull the water out of my outboard well like that.

[rslifkin]

Originally Posted by Chotu

That’s true. I wonder if those could work the same as the automatic bailing things on power boats.

Those work because the deck is above the water line though, right? Like they don’t actively pull water out because of the motion of the boat if it’s below the waterline right?

Because it sure would be cool if I could pull the water out of my outboard well like that.

Deck drains typically work by being above waterline, yes. But there are those sailing dinghy self bailers that will suck water out while you're moving.

[MicHughV]

I may have related this to you before.

While I was building my boat, I got to know a guy building a Piver trimaran.
For power, he had a 15 hp Honda outboard in a well, under the cockpit seat, so that the prop was alongside the hull. The idea being that the engine could be removed and a plug put in it's place, for extended sailing periods.

In theory, I though this was an admirable idea, but the reality of the situation quickly reared it's head.
Turns out that a wave rushing past the boat, would have the same height inside the engine well, as the outside. Needless to say, in smooth water everything was fine, but the moment some wave action was encountered, the engine well would get engulfed with water, causing a lot of problems, besides splashing into the cockpit.

So I'm wondering how you will deal with this situation ??

[Chotu]

Originally Posted by MicHughV

I may have related this to you before.

While I was building my boat, I got to know a guy building a Piver trimaran.
For power, he had a 15 hp Honda outboard in a well, under the cockpit seat, so that the prop was alongside the hull. The idea being that the engine could be removed and a plug put in it's place, for extended sailing periods.

In theory, I though this was an admirable idea, but the reality of the situation quickly reared it's head.
Turns out that a wave rushing past the boat, would have the same height inside the engine well, as the outside. Needless to say, in smooth water everything was fine, but the moment some wave action was encountered, the engine well would get engulfed with water, causing a lot of problems, besides splashing into the cockpit.

So I'm wondering how you will deal with this situation ??

I don’t know. It hasn’t really come up. My sterns don’t typically go underwater because they don’t weigh anything and have a lot of buoyancy. They are supposed to have Diesel engines in them and are designed for that weight.

I have had some monster chop and 70 foot Sportfisher wakes come at me under power but the sterns bounce up above that.

So I don’t really know the answer to this. It just hasn’t happened yet for me.

The Sportfisher wakes at semi displacement are the most steep things I have experienced with this boat. Even chop isn’t as bad.

I’m trying to think of times when I would be motoring that I would experience this type of situation. Hopefully I’m only motoring when I am approaching harbors and things like that. I guess you can motor offshore a bit as well. I don’t really know the answer.

[RaymondR]

Originally Posted by Chotu

I don’t know. It hasn’t really come up. My sterns don’t typically go underwater because they don’t weigh anything and have a lot of buoyancy. They are supposed to have Diesel engines in them and are designed for that weight.

I have had some monster chop and 70 foot Sportfisher wakes come at me under power but the sterns bounce up above that.

So I don’t really know the answer to this. It just hasn’t happened yet for me.

The Sportfisher wakes at semi displacement are the most steep things I have experienced with this boat. Even chop isn’t as bad.

I’m trying to think of times when I would be motoring that I would experience this type of situation. Hopefully I’m only motoring when I am approaching harbors and things like that. I guess you can motor offshore a bit as well. I don’t really know the answer.

A few years ago I was slipping my boat and there was a cat in the yard which the owner was refitting his outboards on so that he could hoist them up on slides to get them completely out of the water whilst sailing. I had seen this before but what I thought was ingenious was the doors within doors arrangement he was building into the bottom of the box (like the bomb doors on a WW2 bomber) whereby they were closed after the engines were retracted to present a smooth fair hull. He was hoping for a significant speed increase under sail.

[MicHughV]

True, the Piver had his engine in the forward part of the cockpit, at a guess, I'd say 8-10' forward of the transom. Having your engines closer to the stern might make a difference....maybe ??

I can relate a personal experience, where, for a short period of time, I had a 15 hp outboard, with a strut extension, strapped onto the stern of my 38' monohull. With calm water, I was ok, but any wave action, would lift the transom up, and with it, the prop would come out of the water.

The Beneteau 432 has a transom similar to yours. At rest, the bottom edge is 4" or so clear of the water. Once underway, the 4" becomes 0", but it's rare to see any water higher than that, unless running downwind, where a wave has been known to climb aboard.

You will have to decide for yourself what works best for you and your boat and this will take some offshore trips to iron out.

[Chotu]

Originally Posted by RaymondR

A few years ago I was slipping my boat and there was a cat in the yard which the owner was refitting his outboards on so that he could hoist them up on slides to get them completely out of the water whilst sailing. I had seen this before but what I thought was ingenious was the doors within doors arrangement he was building into the bottom of the box (like the bomb doors on a WW2 bomber) whereby they were closed after the engines were retracted to present a smooth fair hull. He was hoping for a significant speed increase under sail.

That’s the gold standard. I agree. Would love to do those. I have three weeks. Bronze standard for me for this winter. Ha ha

[Chotu]

Originally Posted by MicHughV

True, the Piver had his engine in the forward part of the cockpit, at a guess, I'd say 8-10' forward of the transom. Having your engines closer to the stern might make a difference....maybe ??

I can relate a personal experience, where, for a short period of time, I had a 15 hp outboard, with a strut extension, strapped onto the stern of my 38' monohull. With calm water, I was ok, but any wave action, would lift the transom up, and with it, the prop would come out of the water.

The Beneteau 432 has a transom similar to yours. At rest, the bottom edge is 4" or so clear of the water. Once underway, the 4" becomes 0", but it's rare to see any water higher than that, unless running downwind, where a wave has been known to climb aboard.

You will have to decide for yourself what works best for you and your boat and this will take some offshore trips to iron out.

Well, of course. That’s not the right place to attach propulsion to a monohull (or catamaran).

Your boat was designed to have a propeller in a specific place. Not hanging off the back as the aftmost piece of the boat.

Same with mine. It is designed to have a saildrive in a specific place and that’s precisely where my Outboard leg is. That’s why it works properly.

I have 1000 nautical miles on the boat so far.

My chief complaint is that the propellers are too small. I wish they were larger in diameter.

They tend to slip at 7-8 knots. They are the largest diameter props I can get on the outboard leg so that’s what I have. There is no changing them.

It’s frustrating because I don’t run out of power. I run out of ability to transmit the power to the water. There’s plenty more power to go even faster than that motoring. But the prop just starts to slip once I apply that extra power.

My second complaint is about the air getting dragged down through the Outboard wells. That is now solved thanks to this thread.

And the rubber mat should also reduce any surges that try to come up through the hole as well.

[rslifkin]

You might gain some speed with the wells sealed off. Less air to the props will get a bit more bite.