canting keel-towing tank

What tests would be interesting to do in the towing tank to study canting keels hydrodynamics characteristics?

Thanks

 

A matrix of cant angles, leeway angles, and heel angles. Objective would be to characterize effective span vs cant and heel. The hydrodynamic figure of merit for any keel is (effective span)^2/(total wetted area), known as the "wetted aspect ratio".

The data could then be compared with theoretical predictions, and be plugged into a conventional VPP, modeling the canting keel as a vertical keel of the same effective span and with an equivalent amount of water ballast (but keeping the total displacement the same).

 

Canting keel tests

Some major areas of canting keel use that should be looked at are the use of a canting keel with a twin hydrofoil system on larger monohulls(a retractable foil on a daggerboard ahead of the canting keel strut and one on the rudder-already being tested in one meter rc models) ; investigation of the downforce(extra righting moment) that can be supplied by a flap on the canting keel strut(or possible nose down mountng of canting keel pivot axis). Along with a study of the various systems used to make up for the lateral resistance lost due to the keels cant including twin rudders(CBTF), wings similar to IACC type wings but used specifically for lateral resistance at high cant/heel angles similar to the new "Bondi Tram" mentioned in Australian Sailing and in the November Seahorse; twin retractable asymetric daggerboards and a single gybing ,retractable daggerboard.
The twin hydrofoil system (with retracting main hydrofoil) offers the greatest potential for breakthru speeds in some monohulls and would be(is) an interesting subject.
But all these areas need study......

 

Forgive me, this is entirely out of my league, but endlessly fascinating.

Could there be any benefit to a canting keel with an "A-frame" type configuration? Sort of like splayed legs and ballasted horizontal foil? Wouldn't this obviate the need for additional canted daggerboards?

If the "A-frame" canting keel could cant and also roll to a windward angle of attack, would this provide lift similar to a single leg canting keel coupled with an assymetrical daggerboard?

Would this even be beneficial to a transoceanic racer? Is there any other market for canting keels?

DC

 

Canting keels

DC-the closest I've seen to what you describe is a French boat the has two side by side canting keels: upwind the windward keel is brought to the point of being 100% clear of the water!
I believe that this technology and its myriad variations is in its infancy and there is a lot of room for experimentation. A study like the one proposed to start this thread IF the results were accessible and IF it was thorough could be invaluable down the line.

 

Canting keel-Towing tank

Many nice ideas. I started the thread but wasn't login. : )

I am a student, doing a project on canting keels. I have access to towing tank, but only for a very limited amount of time. So the best configurations will be tested in the tank, and the others will be investigated theoricaly or with past data. My idea is to investigate most of the configuration with modern tools. (VPP, CFD).
My wish is to publish my work and the data. (this is subject to my university regulations, but i believe it should be allright).
So keep posting ideas.

Nico

 

I hope you're familiar with CFD and VPP. Remember, that a keel on a hull is effectively (as an approximation) a wing on a symmetry plane. I'm just looking at the underslung rudder and stern-hung rudder question. Very similar in terms of the underslung (rudder against the hull bottom) case and a keel.

Good Luck,

Tim B.

 

By 'publish' I was meaning 'make available my results', I don't expect to do the work of an experienced yacht designer or fluid engineer.
I am not that much familiar with CFD(apart from some of the theory), (little experience with Fluent), But this is the reason why I am studying, CFD is part of my study. I think is an interesting tool to investigate small changes, but not the general characteristics.

Nico

 

nico,
Are you at the University or the Institute?
I graduated from "The Institute" when it was still "The College"
Steve

 

I am at the Institute.

Nico

 

nico,
Good for you - far the best place to be ;-)
PLease say "hi" for me to Stuart Roy (who taught me while I was there) and Adrian Lee (who was in my class)
Thanks,
Steve Baker (the bearded one, since there were two of us that year)

 

Steve,

Stuart Roy and Adrian Lee were my teachers in the first year. But since, they left the Yacht design course.

Sorry.
Nico

 

nico,

Sounds like a great project, but daunting in its scope. I'd be keenly intrested in knowing what sort of righting moment vs. drag may be generated by twisting the keel foil. This might be done by placing the bulb CG forward, and it might by done like the 3d mini keel (Raison?), and it might be done by raking the foil forward (BakewellWhite). I feel certain that there is a sweet spot somewhere in there.

 

Nico,
Don't be sorry - hopefully they have gone on to better things.
If you ever get to Hamble, you could say "Hi" to my old house for me. The gate lodge to the old vicarage, next to the fire station. Unless it's been torn down...
Steve

 

Nico,
Back on topic, I could have used this question about 6 years ago, when I was designing this thing:
http://members.aol.com/Saildesign/private/scbweb/bs40.htm

Steve