Lift onset, planing, and lift coefficient

New paper posted on lift onset with planing defined. Delta wing-type lift coefficient provided in agreement with Clements' data on v-bottoms.

 

What the hell is a "finite transom", used several times in the discussion ?

 

The hell finite transom is finite beam.

 

Are there boats that don't have finite beam ?

 

I think they are referring to the analysis, with a theoretical infinitely wide surface there is no lateral flow so easy to calculate, with a finite beam it is much more difficult to calculate the real world position.

"A 1950s era discussion of planing as lift (Du Cane[9])is based on a back of the envelope calculation that predicts a lift coefficient proportional to cos α , with finite lift at no attack angle. This is wrong.
Lift must vanish as α goes to zero. The calculation is based purely on leading edge spray for a boat of infinite beam (two dimensional flow), neglecting the side spray and waves that are the main cause of lift-reduction and drag."

 

Are you asking 'are there boats that do not have a finite beam at the transom, where the transon meets the bottom? Yes, plenty of them.

 

DuCane assumed 2D flow with no Kutta condition and got a lift coefficient that makes no sense
(see the end of the paper) because it remains finite as trim angle vanishes. I treat only 3D flow.

 

Maybe there is a language or translation confusion here.

 

A theoretical convenience ? Maybe so.

 

You should not be confused. Look at fig. 1 and 2.

 

No, clearly defined. Again, see figures 1 and 2.

 

No, I'm not confused, just wondered about the usefulness of talking about finite beam transoms.

 

A related thread: Froude and planing https://www.boatdesign.net/threads/froude-and-planing.57340/

 

Outdated by my posted ms above.

 

Good thing to think about because that's the key to lift and planing.