60'+ or - 20' Ocean Racing Monofoiler Design Discussion

your're of course right, Paul

given: 3000lbs, which is 1'363.6 kilos (I tend to use metric, sorry ;-)

which given that water density is 1 (let's ignore small variations due to salt water), gives a required volume of 1.36 cubic metre.

now assume diameter of tank, 2 feet, i.e. 60.96cm (I think you're optimistic here, by the way). So cross section of tank would be 0.29 sq.metre.

so required length of tank would be 4.67 metres, which is 15.3 feet indeed. Of course a boat like Hydroptere is 24 metres wide, so from a very theoretical point of view it could be done. But I have to admit that the idea of such a large tank moving around, does not really appeal to me much ;-)


plus, sorry Doug, but I really wonder about the practicality of having a moving tank, I mean it also means some complexities. Not to mention the fact that you'd still need a pump to fill / empty it, even if this would be done less often.

If all went perfectly smoothly, I guess you could hope for something faster than pumps, but when would that speed be useful? When doing match racing around a short course maybe?


I'm in Paul's camp on this one - traditional water ballats, fed by pumps, seem fine and less complex.

take care

 

60' Moth

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You might read the FIRST post. If the tank system is used it would have a max length of 6-7' and would be inside an eliptical or thick airfoil
shaped crossarm. The single wing cross arm has several advantages that could be very beneficial to this boat-low drag shape, buoyancy, strength, quick ballast movement and more..
But the details of L'Hydroptere's pumped water ballast system have surfaced since the original conception of this idea and may or may not be a better way to go.

 

No need to be sorry. I think only we silly Americans still fear the metric system. Even in my business I use metric, but for some reason I always revert to my childhood comfort when doing things for myself.

You are correct. I was being optimistic by allowing a diameter of 2 feet. I was trying to give the most benefit of the doubt. It is so funny to see the reply, that we should have used 1.5' x 6'! As I said, no REAL understanding of the world we live in. Very typical of this guy's "engineering" on so many of his ideas.


I see you are in Geneva. I visit Geneva/Morges/Lausanne a few times each year. You have some very interesting monohull boats there, such as the Psaros 40. There seems to be a few older, smaller trapeze boats (maybe 8 meters) in the marina in Lausanne, maybe from some development class, all slightly different but similar. Can you tell me what class they might be? I am attaching photos of some, including one with a cabin added and a much newer boat with wings.

 

In all fiarness to Doug...

...he had apparently been referring to a movable tank within the wing-shaped arms of a flying tri. So the cross-section would have been larger indeed. Still, sorry Doug, I feel that the idea of a moving tank is just a bit too complicated, more complicated than fixed tanks with pumps. Also it would add weight, the arch-enemy.

This being said, from my teenage years in the late 70s I've always thought that a flying boat should / might have wing-shaped arms. You could even do it on Hydroptere I guess, by adding a "skin" over the current squarely-shaped arms. Issue would be the weight of course. You could even imagine to design the wings w zero lift but w flaps to be used to (1) create lift, and (2) possibly, add righting momentum. If you're indeed the Doug who designs and builds functioning models of flying multihulls (I have seen a video somewhere), then maybe you'll one day build one with wings not arms?


Now back to Paul. Yes the Psaros 40 is a nice, modern, fast boat. They didn't make it longer because the Bol d'Or, Europe's largest regatta on closed waters, has a LOA limit; and also to limit the cost. As or the other smaller boats your photos show, I'm sorry but I cannot identify them at 100% (they could be Luthi 33 or 34's, one-of protos designed by Seb Schmidt, the same who did the Psaros 40).
There is a lot of custom building of boats going on around Lake Geneva, and sometimes it adds up to a few units, and sometimes these remain one-offs (sometimes designed by non-professionals who are passionate sailers and always wanted to try this or that idea). This happened w the Psaros 40 - I think 5 have been built so far -, and it happened already in the old days w boats such as the Tiolu's, the Jeudi 12's, etc. By far the most successful of all these was the Toucan, launched in the mid-70s, with several dozen still sailing around the country - that boat can still do better than top 10 percent in large regattas, even though its hull has only limited planing abilities.

And of course today the fastest boats are the multihulls, and we have the Decision 35 class, named after the shipyard that builds them (and which built Alinghi's boats). These are 35 foot long catamarans with a small central pod (doesn't touch the water), 6.9metres wide, displacement 1.2 tons, 122m2 sail area upwind, 223m2 downwind. There are 10 of these sailing around.


take care

 

The boats in the photos, except the one with wings, all appear to be quite old in design and construction. They seem to be some sort of development class based on a certain set of dimensions, similar to the Libera boats, only smaller and less extreme. There are about 10 of them scattered about in Lausanne's marina, all with similar rigs and similar number of trapeze wires. It must be some old class that has since died.

I know well the Toucan, and also the Asso 99s from long ago. Both very fast still. I did the drawings for modifications to the Libera A "Cassiopiea Due" back in the mid-1980s, so was familiar with many of the lake racers of the time.

My own boat is a smaller version of Cassiopiea Due, a Libera Classe C boat of that generation. It is somewhat similar to these boats, but more modern in shape.

 

60' Moth

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Antoine,sliding ballast inside a (monohull) cross arm was first put forward(to the best of my knowledge) by Julian Bethwaite for his Maxi skiff design concept about 6 years ago.I don't think he had decided whether it should be lead or water.
I've been experimenting with sliding on-deck ballast on models for 15 years. On most smaller models the ballast needs to move fore and aft as well as side to side. On this boat(LOA 56",Beam 72") fore and aft ballast makes little to no difference:


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There is video of the F3 on my site; is this the one you saw?
This next boat was never good enough to become a production boat because it is incredibly difficult to sail with manual(no wand) altitude control and no F&A movement of the ballast. The entire rack(including the buoyancy pods) of the "Trapeze Power Ballast System" moves side to side; it needs to move fore and aft on this particular boat as well:


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more on the microMOTH:
Address:http://www.microsail.com/micromoth.html Changed:6:29 PM on Sunday, July 8, 2007

 

No Foiling Keelboats??

Here's an interesting article by Andy Rice, developer of the foiling RS 600(see thread elsewhere in this forum) saying ,among other things, that there probably won't be any foiling keelboats.
Predictions
Address:http://www.inqbator.org.uk/rs600ff/TheRS600FF/Predictions/tabid/275/Default.aspx
I'd say that he is probably incorrect....

 

Pterodactyl,again

Here are some neat views of Bethwaites concept boat:

 

Quick question for Doug

The production foiler in post #51 - ....

What is the strongest wind that it has been sailed in?

Any photos of that?

Have you tried sailing it in ever stronger wind stage by stage to see what happens?

 

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22mph wind with no jib and main reefed maximum. Boat speed was close to 18mph. Video was taken and was part of the original presentation on the website but was removed when the site was downsized. No still pix. No boat was tested to destruction. My windmeter only measured in mph...
Still some video on the microsail site. The difference in boat speed from 5-6mph wind to 22mph was only about 6mph; in very light air it would sail at 2+ times wind speed.

 

Interesting, thanks. I would like to see the video. Maybe you could put it on utube one day.

I don't know if you ever do this, but i would always stay right close to my models ( to leeward always, of course) so i could get a really close look at what was going on. The most wind i've ever sailed one of my models in was close to thirty knots (christmas winds).

So you find V does keep climbing but V/W steadily drops, right? That is certainly as expected to a point.

18 mph is pretty good, especially since i would assume those vertical foils (not the horizontal ones) are ventilating at least somewhat at that speed.

Or have you been able to make them so they do not ventilate hardly even when at those speeds? And do you know for sure? As in, have you ever been able to really get a close look at it when at the higher end of its envelope? With radio control one misses out on a lot of the action in some ways.

(I looked through your site a few months ago)

 

There was no evidence of ventilation of either the vertical or horizontal foils in terms of side slip,spinout or crashes. The first two F3's were tested together for about a year and there were no crashes or pitchpoles.

 

I was referring to ventilation from a resistance point of view rather than a control point of view. And might some ventilation be responsible for the decreased V/W at higher W ? Or do you think it is purely to do with the fact that you' re less aerodynamically efficient due to being so heavily reefed?

I made one experimental model foiler to see if a foiler could be made with no control surfaces at all except for the rudder. That part of it did work as it proved to be auto stable in both pitch and roll.

It had a fixed Tfoil at the stern and fixed, angled foils out to either side about midships. The hull was a very slender shape. The rudder was at the very bow with a windvane operating directly.

At a certain wind speed it would function fairly well in non flying mode. Then from about ten knots W on it would start to fly but quickly would fly so high that only the very tip of the rudder would be in the water , ventilating like crazy and the boat would settle onto a broad reach regardless of what i set the windvane to.

The day with the strongest wind it was off on the broad reach with me running after it as fast as i could in shallow water. At those speeds it would only draw 15 mM or so.

I could not reef it.

It measured 30 cM loa x 30 cM boa.

A couple of things surprised me. One was how inefficient it was as the best it could do was a reach. The other was how much ventilation i was getting on the lateral foils. The latter i think was the chief culprit for the gliding angles and the latter was mostly due to using a foil that was much too thick for those reynolds numbers. It was about 9% with a flat underside, but next time i think i'll use metal and try to go down to about 1% thickness. (This when i was making monohulls that could point at 30 degrees)

The flying too high i fixed by installing a sensor with another Tfoil at the bow, to actually pull the bow down. Then it would fly earlier and be controllable at high W since the rudder no longer ventilated but it added some more resistance so there was no improvement in efficiency.

I never got any pictures of it and it eventually got destroyed by the police so i cannot show you no more but it was a pretty neat learning experiment and cannot wait for the opportunity to make my next (improved) foiler.

 

Sounds like a great experiment. As best I can tell there was no ventilation associated with the F3 in any condition. It sailed in big waves(for it) where the main hull would bottom out and either the windward or leeward main foil would sometimes pop out but immeditely re-entered and continued to work. Interesting things go on with foils at the very low Reynolds numbers the F3 operates at.

 

That bottoming out is interesting . I guess it can be prevented by modifying the proportions a bit (much like deck clearance on a cat) .

The fact that the boat would recover from a windward foil emergence event means it was not providing downforce so in theory you could have used a lot more sail but as soon as(if/when)) the windward foil emerges it would automatically capsize.

I think models are very useful as they allow to simulate quite easily the conditions encountered by a full size foiler in a storm.

What is the highest your machine can point? I watched the video but could not tell from that.