Where are the catamaran innovations?

Sigurd, looks interesting. There is another: put the pivot axis at the top of the foil but running fore and aft. That way the foil can be pivoted either inside the ama toward the main hull or outside. But it can pivot with the boat moving. Not only that but if you use a T foil, the low side of the pivoted foil can act as a daggerboard....

[sigurd]

"pivoted foil can act as a daggerboard...."

Yes, that is the idea with the splay but as I have drawn it you cannot adjust the splay. The reason I drew them like this, and not with the pivot axis going fore/aft, as you suggest, is that for the latter neither kickup nor AoA adjustment is implemented in the same axle - so it would have to be slightly more complex. Not a lot, though - if you did not need the AoA control, the kickup mechanism could be made very simple. And the fore/aft pivot axle may offer additional attractive retrieval options.

Originally Posted by sigurd

"pivoted foil can act as a daggerboard...."

Yes, that is the idea with the splay but as I have drawn it you cannot adjust the splay. The reason I drew them like this, and not with the pivot axis going fore/aft, as you suggest, is that for the latter neither kickup nor AoA adjustment is implemented in the same axle - so it would have to be slightly more complex. Not a lot, though - if you did not need the AoA control, the kickup mechanism could be made very simple. And the fore/aft pivot axle may offer additional attractive retrieval options.

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Sigurd, you don't want a foil to kick up(with the boat moving) with an athwhartship pivot axis-it would be likely to destroy something because all the lifting force would suddenly pull down and then aft very,very quickly.

[sigurd]

yes I do want that. The alternative when you crash into something is that something breaks. Are you saying you would design the foil and its mounting to withstand less than the maximum lift it was capable of?

No, I'm thinking that if the foil was to kick up while it still had a load on it that the foil and it's whole mounting might tear off the boat since the load instantaneously switches from lift up to down and back and a huge pull back force would be generated. I'm afraid if you designed for that pull back load the whole think might be too heavy.

[rayaldridge]

One possibility is an articulated foil-- similar to what some have done to put T-foils on kickup rudders-- the horizontal surfaces pivot so that as the rudders kicks back, the foil remains horizontal.

It's a complication, but foils are complicated.

[Chris Ostlind]

Originally Posted by Doug Lord

... you don't want a foil to kick up(with the boat moving) with an athwhartship pivot axis-it would be likely to destroy something because all the lifting force would suddenly pull down and then aft very, very quickly

All this has been said already in other postings. To continue to ignore the reality is asking for trouble.... your choice. It is nice of Doug to finally acknowledge that rotating foils are going nowhere as a design solution.

Originally Posted by Doug Lord

... I'm thinking that if the foil was to kick up while it still had a load on it that the foil and it's whole mounting might tear off the boat since the load instantaneously switches from lift up to down and back and a huge pull back force would be generated.

Yes, Doug, that is exactly the scenario. Again... nice of you to acknowledge the obvious.

Originally Posted by Doug Lord

I'm afraid if you designed for that pull back load, the whole think might be too heavy.

Yes, Doug, again you've hit the nail on the head. The whole thing is a fool's errand and it's about time you recognized it as such. There seems to be no end to the so-called, creative solutions, for being able to foil without having the foils become excessively vulnerable to a vast range of problematic issues.

Baigent, Lord and their crew can just fester a while on the whole thing, while other, less fiddly boats, simply go on their way, unfettered by the same problematic concerns.

You want to lift off the water and possibly go fast, then you have a downside you will pay. There is no way around that reality short of installing an engine for propulsion and an airborne lifting wing assembly. But, then... is that really a boat?

Originally Posted by rayaldridge

One possibility is an articulated foil-- similar to what some have done to put T-foils on kickup rudders-- the horizontal surfaces pivot so that as the rudders kicks back, the foil remains horizontal.

It's a complication, but foils are complicated.

Yes, Ray, it is a complication. In fact, it is an over-complication to what is already too complicated. So, let's add levers, rods and linkages in a high maintenance, salt water environment, to a boat that is already well over the top when it comes to complicated mechanical and human controlled parts.

This is an inordinately mechanical and maintenance oriented complication, which is scheduled to fail as soon as you do not expect it to do so. It's Murphy's Law of the Sea... If there is a weakness in your planning or design, the sea will find a way to screw it up and make you lose, or break, the attendant (and critical) parts.

Ask any SCUBA diver if this is not true.

Who is more connected to the vagaries of the sea than one who dives with his backpack breathing apparatus for the essence of life? I've been a NAUI certified diver since 1971 and I can't tell you how many times I've had to replace gear that I "thought" was under control.

Proceed under your own conclusions, gentlemen. The ocean awaits your decision.

[Gary Baigent]

Christopher
For all your nauseously smug and negative rants about foil yachts and your boring overplaying that they will never be mainstream (and who cares by the way?) take a look at the Foiler Design multihull thread here in boatdesign.net. For a topic that is supposedly a dead end and an area the domain of the lunatic fringe, this thread has to date 53 pages and 133,333 hits, way ahead of just about any thread listed here. If that doesn't spell out some popularity (or controversy, or interest bordering on mainstream acceptance) then I'm whistling up hill (so to speak).

[Gary Baigent]

My mistake: the 133000 odd foil thread is in Sailboats, not Multihulls.

[Chris Ostlind]

Originally Posted by Gary Baigent

... then I'm whistling up hill

Yes, Gary, I believe you are doing just that, though it gives me no joy to say so.

Do keep in mind that the Pet Rock was one of the singularly most sold items in the world when it was introduced via late night infomercials. The originators made millions of dollars (US) Some would have called the product a mere blip on the commercial radar screen, but there it is, for all to behold.

You wouldn't be putting your foiling obsession in the same league as the mighty Pet Rock by quoting me all those numbers, now.... would you?
http://www.petsdo.com/blog/pet-rock-...6-months-lives

Imagine that. A guy who I love and adore for all that is magical about his boating person... and it turns out he's obsessed by the Pet Rock Syndrome of pure numerical relevance.

Write me anytime, directly (you have the email address) We can find a way out of the morass together and get you back into the place where you belong.

Your most sincere friend,

Christopher

Originally Posted by Gary Baigent

My mistake: the 133000 odd foil thread is in Sailboats, not Multihulls.

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And don't forget 99,000 on "Moth on Foils" for a combined 233,000!
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And in your vicious attack dog horsemanure you didn't even understand what I said! A rotating t-foil system is simple and effective-if it rotates the right way-like an airplane prop. The rudder t-foil can also be rotated if the idea is to reduce wetted surface in very light air. Hydroptere, The Rave, Osprey, RS600FF,Mirabaud and all my full size boats have retractable foils to permit beach sailing.Gary's boats may also have retractable foils? You,Ostlind, are lost in a cold, unimaginative and particularly poorly informed world-glad I-and most people at boat design-are not there too. Pitiful...

[Chris Ostlind]

Originally Posted by Doug Lord

And don't forget 99,000 on "Moth on Foils" for a combined 233,000!

So, I guess I should just assume that you are a club carrying member of the Clan of the Pet Rock, as well?

Pet Rock Syndrome, or not.... This numbers thing is pretty funny.

I'm sorry to share this with you, Doug, but my offer to pal around with Gary during his foiling intervention is not extended to you. Gary has a well developed sense of humor and there's real hope in his case.

You're taking all this just waaaay too seriously, my man.

While I can't fix that issue for you, I can suggest that you go read some Elmore Leonard novels and get yourself a fifth of Jack and settle in for a few days. The world will be a much better place when you turn down the big knob on the angst machine.

And that language....Land Sakes!! My Okie Granny would have been inclined to wash out your mouth with soap.

[Fanie]

Mother calls in the house - 'Kids'
Yes mother ?
What are you doing ?
We're having sex mother...
Ok, as long as you don't fight, ok ?

[sigurd]

Originally Posted by Doug Lord

No, I'm thinking that if the foil was to kick up while it still had a load on it that the foil and it's whole mounting might tear off the boat since the load instantaneously switches from lift up to down and back and a huge pull back force would be generated. I'm afraid if you designed for that pull back load the whole think might be too heavy.

Really so? What could be those forces, tearing at the foil?

wikipedia:

The Cd of a real flat plate would be less than 1, except that there will be a negative pressure (relative to ambient) on the back surface. The overall Cd of a real square flat plate is often given as 1.17.

We have already a foil that should be able to withstand between CL 1 and 2 in the upward direction - plus a healthy margin of safety. As we know, beyond this the foil stalls and gives no more lift but the drag increases.
Would it take so much to ensure it can withstand a CD between 1 and 2 in the negative direction?
Am I overlooking important contributions to the forces applied to the foil assembly when it is kicked up/back?

Maybe-the forces would be applied within milliseconds at something approaching ,say 60 degrees,to the designed "normal" load.
There won't be much difference to what happens with the foil kicking up and just taking the impact. Some foil systems are strong enough to take a grounding while on foils or major impacts w/o damage.