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Why hasn't someone part II


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is really that much buggering about for the 'tactics' guy to be dropping or lifting a foil on the windward side going into or out of mark. We are talking new race boats - I would have thought some properly machined acetal bearing blocks in the case and a well sanded board would be next to no effort.

 

I have no experience here but from discussions on the subject with the Frantic Drift guys - if the windward foil is touching and any pressure on it at all then pulling them up is a bit of a mission -esp as with inward angled boards you are kind of hanging off the side of the boat. FD apparently have some sort of aluminium tube frame sitting up from the ama with a block on it to allow them haul it up from an inboard posn. Maybe their boards are very snug within the cases? I'm pretty sure they would have thought of the sand paper idea.

 

I guess I may have to try and recreate the same system to move them but I'll try and avoid it if I can. I'll probably just see what happens first and how much of an issue it is with dihedral etc. Any advise on how to get boards moving easily when potentially under load be interested to hear. The cats mentioned that do the lifting thing, how much hassle is it?

 

It is good to have a simple setup - my current boat has running backstays and I hate the f**kers...slows every tack down.

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Lionmark, you already have vertical boards - why don't you consider J's instead - then you're lifting the leeward ama as well as the board stopping leeway. Whole platform will be higher out of the water because of the J lift, less wetted surface area, more speed etc. etc.

Also on the point of the windward foil being unable to be moved (when most of it is out of the water anyway) rig a block and tackle and do it from the cockpit, as Frantic Drift does. On the point of extra work aboard; get used to it, yachting is getting more and more complex, canting, rotating rigs are here with more coming, soon there'll be solid wings once the AC 45's appear and that is going to stir the pundits up, even the keel boats are lifting bulbs sideways and dropping and lifting daggerboards. No more sitting like an intelligent vegetable on the weather rail.

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Dan. I've had inverted T rudders on my tris for 30 years now. Here's the rough first stage for my latest version, Seditious Sid, 7.62 x 8 metres.

 

Cc, I would think that your set up would be fine in presure when the lift is required but if you cant retract the boards fully to eliminate drag in the light it will have a cost.

 

This is an interesting discussion for sure, and without being any sort of expert by any means this is what we think we have learned at this stage after a season with curved boards.

 

In the light we use no Curved Ama Board (CAB) as we are better off minimising drag and just using Main Board (MB). The MB is 7m long and we draw about 4.2 when fully down. We will even reduce MB in the extra light.

 

One of the really interesting aspects of the CAB's, and these are asymetrical and can be adjusted for both horizontal and verticle angles of attack by chock changes, is that the first bit of board you put down is vertical, effectively producing horizontal lift and as you put down more the curve means it becomes horozontal, producing vertical lift.

 

We find bellow 10- 12 knots of air up hill we use no CAB and just MB, minimum drag. As pressure increases we start running CAB up to 60% max so mostly lateral loads not lifting. So up hill that is max.

 

As soon as the boat is over 20-22 knots of boat speed, so cracked or running in moderate or heavy, we use full CAB and she effectivly becoms a foiler with only the last 6-10ft of ama in the water and the foil taking 70-80%of the load. The difficult area is where its puffy like the harbour and you are on and off the gas and dont need full CAB all the time, its a bit of a compromise.

 

With ours in good slids you can winch when under load but it is hard on gear so we generaly try to preplan and compromise, or slow a little to unload for changes in CAB.

 

We also have another MB we got with the boat which has a tab, so can be made asymetrical which would be faster in the light light we expect but at this stage we havent felt we have needed anything else to play with, maybe soon?

 

And canting riggs, we have been amazed at the extra lift this creates. When we even run the rig central you notice a significant reduction in performance. Recon that a canting 8.5 of any design would clean up because of the gains, it just huge, maybe 10%+

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On the point of extra work aboard; get used to it, yachting is getting more and more complex, canting, rotating rigs are here with more coming, soon there'll be solid wings once the AC 45's appear and that is going to stir the pundits up, even the keel boats are lifting bulbs sideways and dropping and lifting daggerboards. No more sitting like an intelligent vegetable on the weather rail.

 

Sometimes I like sitting like an intelligent vegetable (with beer in hand). The biggest thing holding the boats performance back initially will be the fact that I (and my usual crew) haven't sailed multi's much before - We will have big "L" plates on for quite a while. I'd like to make things as simple and easy as possible, initially. Basically leave refinements like canting rigs, fancy foils etc till we've figured out how to get round the course without turning turtle, running into things or breaking stuff continuously.

 

Lionmark, you already have vertical boards - why don't you consider J's instead - then you're lifting the leeward ama as well as the board stopping leeway. Whole platform will be higher out of the water because of the J lift, less wetted surface area, more speed etc. etc.

 

Must admit I did stare at your J boards pics for quite a while... I might try and manufacture some for the 2nd season of racing...

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hey Bull, that is a very interesting thread you posted; it is refreshing to read stuff won by hard earned experience rather than mathematical theory. I agree drag is THE problem. By the way, the J foils can be lifted so only the curved section remains below ama. But in light conditions I'll leave the leeward working one right down to stop leeway. And here I am being theoretical, because Seditious Sid isn't in the water yet. On my other foil tris (which have inverted V foils set permanently below the amas) I also carry a mainhull dagger. The inverted V's are an okay compromise - but I think the J's will be better. I had deep, angled, straight foils before ... but although the boats flew and were very fast, the foils would suffer cavitation in large waves and the platform (this on the smaller tri, not on the larger Groucho) would crash, and that is slow, although spectacular. The inverted V's don't do this. But they don't lift as much either. And if they lift too much, (because initially I built them too large) the platform will begin death rocking - which also ends in a crash. Compromises.

Jpegs of Groucho. The foiling shot in light airs is with the too large inverted V's, since reduced.

post-3088-141887171426.jpg

post-3088-141887171428.jpg

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Re Raising Boards on an 8.5.

On Attitude we definitely raised our Windward board as soon as we even slighty started lifting a Hull (With exception of short tacks). Makes a huge difference, boards were not assymetric or on eny sort of lifting mechcanisim. I would sugest if you don't raise them you are just been lazy. Definitly worth the gain just need to pick the time to raise & lower.

On Charleston Boards are slighty aysemetric so have to be raised.

 

- Shane

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Greg W said "Cool. I presume the only one built? (here anyway). Would be keen to come have a look at what your doing with it some time if convenient."

 

You are very welcome but might be hard to arrange? I am in Perth WA and the boat (bits) are in a 40ft container in Nelson NZ.

As far as I know Manuahi is the only firebird in NZ. I heard from Malcolm that one was built in Queensland, I think, but that one was even heavier than mine. My floats are 4mm stress ply and go 120kg each (guess), the old (now in the tip) main hull was solid glass and way over built by Richard Pilkington before he refined his methods, circa 450kg+.

 

TB

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Richard Pilkington should be hung up by his toenails and whipped with barbed wire for building such a grossly overweight main hull. The whole complete Firebird with foils, rig and sails was probably designed to be that weight. Tensioned ply was not his forte ... just polyester snot with chopper. I've sailed with him on Sundreamer and his brother used to crew with me on Bamboo Bomber - hence my taking the p**s.

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To Richard's credit he only moulded one hull this way and he put it to one side knowing it was too heavy. Then along comes a young, completely nieve (sp?) chap who knows not much more than how to sail a Hartley 16 and who buys it with a set of incomplete plans from someone that Richard gave? it too. Maybe Richard should have done what I did many years later, ......cut it up.

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Not sure if any one else has mentioned it or not, but another nice thing about a central centreboard only is that as you power up, and lift your main hull, drag from the foil is reduced.

With the boat flying the main hull you don't need as much foil down to prevent leeway, and that is exactly what happens automatically.

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Greg W said "Cool. I presume the only one built? (here anyway). Would be keen to come have a look at what your doing with it some time if convenient."

 

You are very welcome but might be hard to arrange? I am in Perth WA and the boat (bits) are in a 40ft container in Nelson NZ.

As far as I know Manuahi is the only firebird in NZ. I heard from Malcolm that one was built in Queensland, I think, but that one was even heavier than mine. My floats are 4mm stress ply and go 120kg each (guess), the old (now in the tip) main hull was solid glass and way over built by Richard Pilkington before he refined his methods, circa 450kg+.

 

TB

 

LOL yeh, it might be a bit difficult - I'm in Ak. be interested in any other pics you have. I always liked the look of the Firebird on paper. I see you can still get plans too. The article below is from 1976.

 

Getting back to the original topic Malcolms late 1980s F28 Stinger 28' has angled foils in the floats, a dagger board in the main hull and room for FA else.

Firebird article 1.jpg

Firebird article 2.jpg

firebird2.jpg

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Good stuff, Greg. Interesting that 30 years ago design aspects from Malcolm Tennant are just now being considered ... meaning approach and philosophy, meaning wide beam, angled foils, decent sized wing masts, very light construction - and meaning the turkeys around now are a conservative and backward bunch by comparison.

Three decades ago, knowledge of foil placement had not gone through the sorting out stage and the ama foils are actually too far forward; the platform would sail bows up with this setup (which is what the designer would have wanted for safety reasons; he was also pioneering over long floats forward) but this could have been compensated for by inverted T rudder design so the boat would be near level at speed. Or shifting the steering position forward. Interesting that the angled aft rudder design on Firebird now is considered very wrong (lifting the stern with a quick course steering change; the GBE had the same setup) - but that too, had not been sorted in those days. He rectified it with Stinger. Anyone building a Stinger today with slight alterations, foil positions, square top main, would have a really excellent multihull.

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Anyone building a Stinger today with slight alterations, foil positions, square top main, would have a really excellent multihull.

I'd be more inclined to say they would have an excellent racing multihull. Most people want more than 4' headroom in their toys nowdays.

 

meaning approach and philosophy, meaning wide beam, angled foils, decent sized wing masts, very light construction - and meaning the turkeys around now are a conservative and backward bunch by comparison.

.

 

I think some of MTs 70s and 80s work is right up there with Newick in terms of cutting edge ideas and being able to distill relatively simple, fast, minimalist boats. The Newick F28 from the same time also has angled float foils and a central dagger.

 

Horses for courses eh? Its probably more of a challenge to design a boat with meaningful accomodation and performance capability than it is to design a pure racer. MT also designed a Firebird sized boat (Demon) with accomodation and full headroom. I know which of the two I'd rather have.

 

No boatbuilding today - the middle of the shed is flooded :problem: Bloody Weather!

Newick F28 001.jpg

Demon1 001.jpg

Demon2 001.jpg

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A Jim Young quote that will always remain relevant:

"Everyone wants sports cars but when the moment of truth comes, they invariably end up with family saloons."

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A Jim Young quote that will always remain relevant:

"Everyone wants sports cars but when the moment of truth comes, they invariably end up with family saloons."

 

A good analogy, but there are some pretty quick family saloons out there these days.

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