Hugh Welbourns's DSS 25

[Doug Lord]

This looks to have a lot of potential. Uses the Dynamic Stability Systems foil invented by Hugh Welbourn on a sportboat designed specifically for it. The DSS foil sticks out of the lee side of the boat to generate extra righting moment thus allowing more SA or a lighter crew/ballast.
A further expansion of the use of "foil assist" on monohulls-just another facet of the on-going foiler revolution which is changing sailing forever........

http://www.harken.com/Interviews/DynamicStability.php

pix-from ,SA,illustrated W25 from the Daily Sail, render from Harken article. DSS foil in water from Ocean Navigator

[Chris Ostlind]

What? No Helium?

[Paul B]

Originally Posted by Chris Ostlind

What? No Helium?

How do you know?

[Tanton]

Based on Palmquist research and Patent.
Comprising a single buoyant hull having mounted transversely across the hull a hydroplaning wing. The wing having a positive angle of incidence, providing hydroplaning to conteract the heeling moment and thrust of the sail.

[Paul B]

Originally Posted by Tanton

Based on Palmquist research and Patent.
Comprising a single buoyant hull having mounted transversely across the hull a hydroplaning wing. The wing having a positive angle of incidence, providing hydroplaning to conteract the heeling moment and thrust of the sail.

I believe Alberto Calderon did similar research for an America's Cup team in '88.

[Zappi]

Is a canard based on the same principle?

[Doug Lord]

Originally Posted by Tanton

Based on Palmquist research and Patent.
Comprising a single buoyant hull having mounted transversely across the hull a hydroplaning wing. The wing having a positive angle of incidence, providing hydroplaning to conteract the heeling moment and thrust of the sail.

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Very interesting, Yves! Has it been built?

[Doug Lord]

Originally Posted by Paul B

I believe Alberto Calderon did similar research for an America's Cup team in '88.

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The second CBTF patent uses a canting keel strut with a flap whose purpose is to develop a downward lift on the windward side(as opposed to lift up on the leeward side for DSS) adding to the boats righting moment. They say that it can reduce the ballast in the canting keel bulb- which is already more or less 40% less than a fixed keel-a further 30%.


http://www.google.com/patents?id=5Fw...lderon&f=false

[Paul B]

Originally Posted by Doug Lord

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The second CBTF patent uses a canting keel strut with a flap whose purpose is to develop a downward lift on the windward side(as opposed to lift up on the leeward side for DSS) adding to the boats righting moment. They say that it can reduce the ballast in the canting keel bulb- which is already more or less 40% less than a fixed keel-a further 30%.

That's not the research I was referring to.

[Doug Lord]

Originally Posted by Zappi

Is a canard based on the same principle?

=======
No, this concept has nothing in common with a canard. A canard is a small foil placed ahead of a larger foil with a greater angle of attack than the larger foil. Its a canard because of its relationship to a second foil.
I think DSS MIGHT be improved in combination with a rudder t-foil on some designs. In that case it would be a tractor configuration-depending on loading and how much the main foil was retracted. It might also defeat one of the great advantages of DSS: the foil(or foils) can be 100% retracted in light air. If the rudder T-foil was done in the manner of the National 12 then it too could be retracted.

[bistros]

Originally Posted by Doug Lord

=======
No, this concept has nothing in common with a canard. A canard is a small foil placed ahead of a larger foil with a greater angle of attack than the larger foil. Its a canard because of its relationship to a second foil.
I think DSS MIGHT be improved in combination with a rudder t-foil on some designs. In that case it would be a tractor configuration-depending on loading and how much the main foil was retracted. It might also defeat one of the great advantages of DSS: the foil(or foils) can be 100% retracted in light air. If the rudder T-foil was done in the manner of the National 12 then it too could be retracted.

And I was certain a canard meant duck in French, or a nonsense story or cheat in English.

The word was adopted describing aerodynamic wing arrangements where the main lifting surface was to the rear, much like a duck's silhouette in flight with the long neck and short body.

Still remember the visit to Wright-Patterson and seeing the XB-70 Valkyrie. Now it had canards! Same thing for the Wright Flyer at the Smithsonian.

--
Bill

[Zappi]

I see. It would seem its a lot of unnecessary drag if a keel is still required and these are supplemental. Unless maybe if it lifts the boat up for um.... Planing?

[Doug Lord]

Originally Posted by Zappi

I see. It would seem its a lot of unnecessary drag if a keel is still required and these are supplemental. Unless maybe if it lifts the boat up for um.... Planing?

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In many respects it does the same thing the main foil does on the Moth: it lifts up. But because the center of lift is offset to leeward it also creates righting moment-something the Moth foil doesn't do. The lift is equal to a proportion of boat weight-it doesn't lift the whole boat clear of the water but it reduces the wetted surface to facillitate-and improve-planing characteristics of the boat as it increases the righting moment. Careful design is required to make sure the benefits outweigh the drag....

[Doug Lord]

I wanted to post this to give those interested in DSS an idea of another way the system can work. The picture illustrates a foil on each side that pivots in a slot like a centerboard:

[Timothy]

On the DSS web page they say that the lifting foil is applicable to cruising vessels. I would of thought that its main purpose was to aid in planing when off the wind. How much lift could such a foil generate when beating at the displacement boat speeds of the average cruising boat ? If its an amount sufficient to significantly effect righting moment and you elect to rely on that lift and the boat is rigged accordingly what do you after coming about before the boat accelerates and the foil is providing no lift? (presumably sheet out and move the board across while its not under load?). Doug if the wings do prove effective I think the DSS approach is the way to go . It would appear that the pivoting retractable fins in your illustration would suffer from the same slot drag that has plagued center boarders and makes dagger boards a better option for higher speeds. Sorry if the answers to my questions are self evident but I know next to nothing about lifting foils and my interest in them is limited to their application to cruising boats at displacement speeds.