Design for DSS-Foil Assist for Keelboats

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The righting arm of the DSS foil is from the heeled CB to the center of lift of the foil. The righting arm of the hull is, in essence, from the heeled CB to a vertical line thru the boat CG. see post 258


The tradeoffs on wider or narrower beam are the same as with any other design except where a rule gets in the way like the Mini Rule. Depending on a lot of factors there is not likely to be any benefit from making a boat wider so you can have a longer DSS foil. Among the advantages of DSS is vertical lift which reduces wetted surface so the primary focus would be to accent the advantages of the foil by having a low wetted surface design that takes full advantage of the foil for RM. You certainly wouldn't design a DSS boat with water ballast?! And it is probably better in most cases to have a fixed keel with minimal ballast.

 

No such thing as a moment couple where both vectors are the same direction.
The total upward vector is the buoyancy + the lift on the foil + any hydrodynamic lift on the hull.
The total downward vector is the weight of boat including crew & contents + any downward component of aerodynamic forces.

 

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My apologies- brain fade-I think.I'm too tired to go any further.

 

OK, thanks. I agree that this more recent sketch represents the physics as I understand them. I would sum the ups (determining the center of this total), sum the downs (determining the center of that total), then find the lever. #3 is still not a moment couple, but I see now that you're taking all the moments about that point, and that's legit. But I think my point holds that all the levers will be greater on the wider boat, yes?

 

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I'm sorry, I'm really tired and I don't get what you are referring to as "Your#3".

 

I was in the middle of editing my post and got cut off (we have a storm here, as you might have heard).
I see what you're doing, taking all the moments around the same point, CB.
That's totally legit, of course, so my bad saying otherwise.
But I think my point stands that the arms are greater on a wider boat, yes?

 

I think you're right about beam but it reduces to basically the same consideration beam would anyway. Except that since the foil lifts vertically then you might want to enhance that effect by starting out with a low wetted surface easily driven hull that will have far more stability(due to the foil) than that type hull would normally have.
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Good luck with the storm. We got brushed by it but no more than a normal thunderstorm except that it lasted longer.

Heres another sketch:

 

Infinity 36 DSS-two boat testing

From the Daily Sail: ( http://www.thedailysail.com/inshore/13/64443/1/video-two-dss-infiniti-36s-trialled )
"For the tests we went sailing yesterday with initially Skazka having her foil deployed while the foil was retracted on Foiled. Upwind in around 8-10 knots there was little to choose between the two in terms of their speed, however Skazka was showing less dynamic movement in terms of pitching, roll, etc. The most compelling demonstration of the DSS foil was when the wind picked up a little and kites were hoisted on the two boats (around four minutes into the video below). At this point Skazka's foil was brought in (initially) and Foiled's was deployed and it was noticable that with the DSS foil out, cruising along at 14-15 knots Foiled was able to hold her sail better and if required could sail significantly higher."


Two boat testing-DSS : http://www.youtube.com/watch?feature=player_embedded&v=DRMhvR0nOAE

 

So they didn't even say it was faster?

 

Infinity 36

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Thats not the impression I got. Strange wording.

 

I sure couldn't figure out what they were doing on that vid. It was pretty clear that upwind the boat without the foil was at least holding it's own, maybe even gaining a little to weather. Downwind the camera angles made it impossible to tell anything. It did sort of appear that the leeward boat was sailing faster, don't know if they had their foil out. Foiled's was out the whole time but from about 2:30 to 4:00 it looked like they were trying to figure something out and not concentrating.

If that video was supposed to show us performance differences in their 2 boat testing it failed.

 

Mini Proto DSS

The first Proto using DSS has been launched. The boat is much narrower than a "normal" proto and about the same maximum beam with the foil deployed. Going to be great to see how she does!

 

Dss

Infinity and Danish Yachts have just announced a 100' DSS equipped cruising yacht with nothing spared for top performance: http://www.dynamicstabilitysystems.com/infiniti-and-danish-yachts-announce-the-100s/

 

DSS Mini

From the DSS site today: http://www.dynamicstabilitysystems.com/sea-trials-for-the-dss-mini/


DSS Mini completes first day of sea trials. Jean Saucet, skipper of the DSS Mini was all smiles as he completed the first day of sea trials in 10-14 knots of wind and overcast conditions. “The boat is fast and easy, we cannot wait to continue testing".

 

Nothing new there. Just Another over stylized, impractical, unusable, Gee Whizz is that carbon ? 30m yacht ......with a long overhanging sprit and no place to take cover from the ferocious sun.