Automatic keel trim tab?

[BTG YACHT DSGN]

The empty bulb will be TOTALLY immersed. In that case there will be no wave drag as for a hull, that's the main drag advantage I wante to obtain.

If- you wish to call it a trimaran- here you go! For me a trimaran must have a main hull and TWO supporting hulls partially immersed.

Anyway- how do you think: is this gonna work?

[Doug Lord]

I don't think the empty "bulb" idea will work well at all . One reason is that it would probably be difficult or inefficient or both to get it far enough below the surface not to have wave drag or drag related to its proximity to the surface. I think you'd have to have two of these wouldn't you? Or flood it on one tack and empty it on the other? What about in conditions when you don't need it?

[BTG YACHT DSGN]

Originally Posted by Doug Lord

I don't think the empty "bulb" idea will work well at all . One reason is that it would probably be difficult or inefficient or both to get it far enough below the surface not to have wave drag or drag related to its proximity to the surface. I think you'd have to have two of these wouldn't you? Or flood it on one tack and empty it on the other? What about in conditions when you don't need it?

Assuming that the foil of the empty bulb will be canting 80-90 degrees and the boat will be heeled- there's no possibility that the bulb will get close to water surface acting on the leeward side enough to pierce the water surface ,I think...

When would I don't need it? Even in light airs it will contribute to the displacement. Additional wetted surface? Maybe a little bit...

Huh! Another thing might be that the center of drag will be pushed more to the leeward and the yacht might have the tendency to turn because of that fact... But maybe this effect will be quite small- if it's not disturbing sailing with canting keels on ex VOR boats, why should it disturb sailing on my boat. The situation is similar, only the wing is canted not windward but leeward...

[Doug Lord]

I missed the canting part-I thought you were talking about adding an empty bulb to something like the DSS wing. My mistake....
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Do you envision this as the boats' only source of RM?

[Timothy]

Doug. My point was that a gybing board in a rotating trunk could be lifted for downwind sailing or shallow water anchoring or steaming. Another benefit would be that the slot unlike that of a centerboard's would be sealed board,up, partially up, or all the way down. After reading Tom Spears posts I am not sure the perceived benefit of either a gybing board or a trim tab are worth the complication but I still can't help thinking that a hull travelling in the direction of its longitudinal axis would have less drag.

[BTG YACHT DSGN]

Originally Posted by Doug Lord

I missed the canting part-I thought you were talking about adding an empty bulb to something like the DSS wing. My mistake....
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Do you envision this as the boats' only source of RM?

No, not only, the hull will generate some (hopefully 70%) in a traditional way and other 30 will be generated by the canting empty bulb acting on the leeward. That's my vision.

So it can be applied to a ,,normal" hull just as an appendage. As a helping device.