I have been trying to draw a scale model propellor for a large model boat. It is a design known as a surface piercing cleaver design and is found on fast racing outboards. I can draw it using a swept profile along a helix but I really want to get an airfoil section to the blade. I normally design machines and automation equipment so this is a one off. any help would be much appreciated.
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 email@example.com) and remove _FASTBOAT from the address.
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.
--------------------------------------------------------------- "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?