Boat Propellor - surface modeling skills?

Do you have a NACA airfoil number for the screw??

I have a proggy to generate NACA sections, I can send it to you.

MC,

I race an inboard hydroplane (2003 APBA US Nation High Point Champion !!!) and would be very interested in how you make out with your model. The surface piercing propellors I use have progressive pitch and I don't know how they define the cross sections.

I do know there is a company in Washington (??) Herring Propellors that finishes their props on a multi axis milling machine to make all the blades identical so the model you are looking for does exist. My props are cast and then hand finished by a true craftsman, it is really a black art.

I would love to come up with an accurate model and then have someone do a STL model for my guy to look at. Seems like there are some investment casting places that could take the STL model and provide the raw casting pretty cheaply.

If you get a chance drop me a note (dankanfoush snipped-for-privacy@yahoo.com) and remove _FASTBOAT from the address.

Thanks.

Dan

I sort of hate to mention this but if you have the design equations for the surfaces "Philippe Guglielmetti" may have a program that would be of aid. See MathSurf 2003 at

and the somewhat old thread(s) ... one of which was "MathSurf 2003 : generate mathematically defined surfaces with a few Visual Basi"

HTH

Thanks Cliff. In fact I'm still looking for a *real* application of MathSurf, so if you guys have the EQUATIONS of your propeller surface, I'll do it for you...

Sorry for the late reply. I believe what you are trying to do may be slightly unnecessary. A surface piercing prop provides propulsion by creating a positive pressure (p.. p.. p.. p.. p..!) on its aft face. This is in contrast with an ordinary prop that creates a negative pressure on its forward face (like an aircraft wing) sucking the boat along. The forward face of a surface piercer spends virtually all of its operating life ventilated. Therefore an airfoil shape for a surface piercing prop would be useless for any hydrodynamic purpose. The sectional shape should largely be driven by structural requirements for the really high loads encountered.

-- Ralph

--------------------------------------------------------------- "Just 'cos I don't care doesn't mean I don't understand." Homer J. Simpson

So the OD & the ID of the prop would have the same surface speed at it turns?

And the same unit volume of water (cubic inches per rev per swept radial volume) (if this differs a great deal I suspect much of the energy goes into non-laminar turbulence & shearing of the fluid and you have a mixing blade instead of a prop) independant of radial location?

Just to mention that our FREE MathSurf and SketchFile macros might help you a lot.

As I understand from , modern propellers are obtained by "inverse airfoil design" which gives NACA-1 or NACA-16 profiles.