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Old 05-12-2014, 13:12   #76
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Re: A Catamaran question.

What I think will be a big improvement is the ride on foils should be much smoother as they operate under the waves- where there is hopefully much less break and up and down forces most of the time. This little company seems to infer that on their "tests".
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Old 05-12-2014, 15:18   #77
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Re: A Catamaran question.

Yes, if a boat is fully foiled, then the ride will be smooth indeed. I don't think we will ever see fully foiling cruising boats - the problems and risks are just too high. Even the AC72 in calm waters and a professional crew had trouble foiling upwind and foiling at all in lighter wind. Throw in waves and you have a real disaster. Throw in a cruising couple and the need to control foiling surfaces and you have deaths.

Using foils to partially lift boats is free of much of all that. However, the ride won't be smooth like a full foil boat because the hull will still be interacting with the water like usual. I do think we will see many multihulls that use foil surfaces to provide some horizontal lift in the future.

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Old 05-12-2014, 15:22   #78
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Re: A Catamaran question.

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Originally Posted by colemj View Post
I do think we will see many multihulls that use foil surfaces to provide some horizontal lift in the future.
I'll stick my neck out and predict, if it happens at all, that it will be vertical lift.

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Old 05-12-2014, 16:22   #79
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Re: A Catamaran Question

Is there a Moth design in a multihull?
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Old 05-12-2014, 18:29   #80
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Re: A Catamaran Question

Don't these foil surfaces create drag, especially at lower speeds? It seems like all of these trimarans with foils do amazing with 25kts of wind, but what happens when it drops to 6 kts?
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Old 05-12-2014, 19:58   #81
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Re: A Catamaran question.

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I'll stick my neck out and predict, if it happens at all, that it will be vertical lift.

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oops!

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Old 06-12-2014, 05:31   #82
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Re: A Catamaran Question

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Is there a Moth design in a multihull?
Indeed there are. Here's one >> Phantom International | Flying Phantom by Phantom International

But this one and Moths are a long way from being cruisers.....

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Old 06-12-2014, 09:37   #83
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Re: A Catamaran question.

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Doesn't have to ride on foils. Even moderate lift from foils - say 35% - will help tremendously. I think the very near future of multis are to incorporate foiling surfaces toward a modicum of lift, rather than outright foiling. The boat will still be in the water, but "lighter".

Might make those new Lagoons finally reach 50% of wind speedů

Mark
anything taking 35% of lift is indeed riding on its foils

Foils have to be completely submerged to have anything like this effect. You are in a sense, flying through water, just as aeroplanes fly through their medium, but where water is 800 times as dense.

Is it possible that hydrodynamic devices could accomplish this? Navies the world over are researching this sphere for several decades, but there is a lot of existing history from the Soviets which suggests some significant downsides, and the 'new Russia' isnt significantly upholding their use.

Some success has been seen in more sheltered waters for ferries and naval FAC's, where sea states are more under control. I think any adventure offshore would quickly reveal some vast shortcomings in heavy seas, and thats why we dont see offshore use.

Where navies do appear to be going is in multihull concepts, I guess I dont have to explain to you that we are already there

The future of sailing may spend more attention on the cleanliness of the rig and parts above the water than the spaces below. Not to say I would completely exclude foils, but more more as hydrodynamic fixes than lift supporting devices.
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Old 06-12-2014, 12:06   #84
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Re: A Catamaran Question

Well, yes, I guess technically any lift at all means riding on the foils. I thought I was being clear about pure foiling being when the hull itself is out of the water.

Boats now have lift-generating foils that are designed to keep the hull in the water. Mostly racing ones, but Catana and MM have drawn up some cruising versions. The MOD70 racing tri, for example, uses foils to lift 70% of its weight - it never fully foils.

I was assuming multihull all along here, since that was the topic of the thread. I also expect that the future will be paying attention to this area.

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Old 06-12-2014, 12:45   #85
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Re: A Catamaran Question

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Well, yes, I guess technically any lift at all means riding on the foils. I thought I was being clear about pure foiling being when the hull itself is out of the water.

Boats now have lift-generating foils that are designed to keep the hull in the water. Mostly racing ones, but Catana and MM have drawn up some cruising versions. The MOD70 racing tri, for example, uses foils to lift 70% of its weight - it never fully foils.

I was assuming multihull all along here, since that was the topic of the thread. I also expect that the future will be paying attention to this area.

Mark
Typically foil born sail boats are configured a little differently, as there has to be two sets of planes, one amidships, and another set aft.

The impacts on a surface ship are obvious; even without considering the weight, in calmer conditions the flatter trajectory is likely to decrease pitching and consequently increase speed, in deep rough seas the boat will bury its bows in the peaks, and allow the crest to flood mid ships. As the forward mass brings the bow sections back down I fear it will really bury itself into the troughs and absolutely stall.

Take really rough weather out of the equation and there seem to be a lot of apparent advantages, but in steep short seas I think, its really quite a dangerous scenario.
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Old 06-12-2014, 14:21   #86
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Re: A Catamaran question.

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...I think LightSpeed (Atlantic 44) may still be for sale...much less expensive than a Gunboat.
Yep, LightSpeed an Atlantic 42 is now for sale in San Francisco bay area.
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Old 06-12-2014, 14:33   #87
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Re: A Catamaran question.

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Yep, LightSpeed an Atlantic 42 is now for sale in San Francisco bay area.
Listing link? Asking price?
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Old 06-12-2014, 14:48   #88
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Re: A Catamaran Question

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Originally Posted by ZULU40 View Post
Typically foil born sail boats are configured a little differently, as there has to be two sets of planes, one amidships, and another set aft.

The impacts on a surface ship are obvious; even without considering the weight, in calmer conditions the flatter trajectory is likely to decrease pitching and consequently increase speed, in deep rough seas the boat will bury its bows in the peaks, and allow the crest to flood mid ships. As the forward mass brings the bow sections back down I fear it will really bury itself into the troughs and absolutely stall.

Take really rough weather out of the equation and there seem to be a lot of apparent advantages, but in steep short seas I think, its really quite a dangerous scenario.
The boats I listed are using only daggerboard foils. There aren't any aft foiling surfaces. Keep in mind that the boat hull stays in the water, so any pitching will simply be that it normally sees. Yes, the speeds would be a bit more than normal (else why have the foils at all), but we aren't talking speeds significantly different than if the boat did not have foiling surfaces.

To be clear, I am talking about using foils to virtually "remove weight" from the boat - not put it above the surface. There will be other performance enhancements, of course, from using efficient foiling surfaces.

Again, these boats exist now and others are in design phase. They are used, and intended for use, in all sea conditions.

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Old 06-12-2014, 15:29   #89
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Re: A Catamaran Question

I am pretty sure I read an interview talking about Gunboat developing C foils for their large boats. The intent is to lift ~50% of the boat weight, but have no intentions of trying to lift the boat fully.

The only large boat I know designed to fully foil offshore is Hydroptere and that beast is just insane.
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Old 06-12-2014, 16:22   #90
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Re: A Catamaran Question

One of the main reasons stated that a hydrofoil cannot be used for a cruiser is that we cannot drive it. I predict that the evolution of autopilots will eventually overcome this, and allow for the safe passage of large foil boats in almost all types of weather while foiling. When they cannot foil, deep fins may keep them upright, as well as things like remote deployed drag cutes and masts that telescope back into itself, providing a much lower center of gravity.
Bottom line- if it was 100% safe we probably wouldn't be doing it anyway.
Let the flames begin....
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