About inclined underwater hull form

In reality, I think, is not get a real important lift, is obtain a favorable form to gain the more lift possible and principally do not not have a "bad" form to diminish the good keel action, because the total lift is a vectorial sum of all lift. If we have a hull form that do not generate lift or the lift generated even small is against the action of the keel (in the wind direction) we will have a prejudice in the efficiency of the hull + keel generate an effective force.
Simplifying, it was as if we had an airplane and on some part of the wing foils are reversed.
I can try to you run your boat design.

 

Earl, have you the Rip Tide hull form in Freeship file?

 

Earl

Seeing better I think that Rip Tide have a chine with the edge rounded.

 

What an astonishing shape at 30 deg heel... like a deep V-bottom powerboat. Also, effective length increases nicely with heel - a design more than 100 years old http://www.starclass.org/history/star_boat_design_development.shtml. What happens to wetted surface when you heel from 0 to 15 to 25 deg?

30 degrees is maybe a bit too much heel - typical heel angles for the Star are 22 to 27 degrees, but never under 15, they try to heel it as soon as there's little wind.

 

The Juan K simulation is not completely realistic: 15 degrees is too little heel, and the stern is never dragging that deep in the water, rather just the corner digging in. But then again, he would not publish his most realistic simulation.

 

Fredschmidt,

Could you send me the 3D Star model in some format?

 

Mikko

Yes, is a beautiful and surprising simple form hull.

The fbm file for Freeship version 3.28+ is attached, I lost a non mirrored drawing. I not remember in save it before mirrored.

The wetted area diminishes with heel, a chine consequence:

0 degrees --> 6.9 m2
5 --> 6.85 m2
10 --> 6.7 m2
15 --> 6.35 m2
20 --> 6.1 m2
25 --> 5.85 m2

 

thx, was curious but 3.1 dont open this file, will try Freeship version 3.28+ later and play

 

I don't have freeship, can it export IGS or STL or something?

 

Mikko

.igs attached.

.dxf also

 

Thank you.

 

You know, Fredschmidt, I have done a theoretical calculation from my post #13 and am not satisfied with the results I am getting. A very simple model, with no hydrodynamic interference between the hull and the keel, shows that there might be some benefits form a lifting hull, in terms of the overall (hull+keel) L/D ratio. So I am not satisfied with these results, because they apparently go against my intuition and in favor of your intuition.

I will now try to estimate the effect of hydrodynamic interference (angle of attack induced by the hull on the keel and vice-versa) and see what happens. If I am still not satisfied, then I will ask to see a test-model study before conceding a defeat.

Where are now all those students in search of a thesis subject? This one would be really nice and useful.

 

Rip Tide

One of our members, who has worked as a professional loftsman, has lofted a computerized version off Ted Houk's original drawing. One caution about analysis of older model yacht drawings: they are approximations, because the final fairing was done on the building board. This is particularly the case with Rip Tide, which was cold molded from thin cedar over a carved form. Anyhow, I've attached what he submitted to us. I have offsets are in csv format which any spreadsheet should be able to open, but the forum won't accept that. I don't have any tools to open the dxf and igs formats so I don't know if they will work for you.

Cheers,

Earl

 

Daikiri



Earl

Thanks very much, I will try open.

After try see Rip Tide in 3D I will put the results here.

 

Try changing the file type to .txt which the forum accepts.