I think I mite need a ventral fin for a large seaplane I'm building. (Kangke Monocoupe). I'm just not sure what shape and size to make it.
Any help on it would be great.
Thanks
Joe

I'm not sure if there's a formula, but I'd say about a 1/4 to a 1/3 of the vertical stab total area (including rudder) would be sufficient. Just don't extend so far down that it would drag in the water, and you'd want it to be in keeping with the 30's style of the Monocoupe. Something like the one on my Cub would work, and look okay.