We were always among those who thought things like propellers were Black Magic, Voo-Doo and a little bit of smoke and mirrors thrown in... to some extent we still believe that but the smoke is slowly clearing.
So, tongue in cheek we proudly present...
On any other configuration of plane you have proven components and technology to select from; choosing a propeller is a matter of your preference of vendors. To our knowledge there are few proven configurations of our plane and engine so we are in uncharted territory. Given that, we feel it would take several propellers to "dial into" the best compromise between climb and cruise. It is also our understanding that there may not be a fixed pitch design that will satisfy both climb and cruise needs with this much available horsepower.
Our choice for an first propeller will be one that strongly favors a climb pitch for safety in initial testing.
One way to carve a propeller is to generate blade profiles at 2" intervals, make templates and carve away. Another way is to put the templates in a fixture, a glued up clear pine blank in another and with a duplicating machine you follow the templates with a tracer while a router carves the blank. You then finish the blank, swap positions in the machine and it now becomes a blade master template. In other words you only actually carve a single blade, after that you only duplicate that master blade a multiple of times for either a two blade or three blade propeller.
You can also use a known good propeller, even a broken one as a template to clone a new master blade template. It is possible to make small adjustments in pitch when jigging up the master blade.
We decided to start small; actually a friend heard we had a duplicator we will call the Super Duper and asked if we'd like to try it out on a small motorglider prop. Just in case they gave us two glued up oak blanks. Nothing like learning on someone else's donated oak. They came out beautiful! There is just something about a nice wood prop.
John Slade has a Cozy Mk-IV with basically the same Mazda rotary engine and it is also turbocharged. His prop was working out pretty good, possibly a bit too much pitch. While he is installing his new IVO Magnum inflight adjustable prop he loaned us his nice wood prop, you KNOW what we did with it :-)
Clear pine master blank glued up:
Prop to be cloned, hub template, Forstner bits and "Super
Counter boring hub for SAE 2 hub:
Master blank and prop to be cloned ready to go:
Setting up "Super Duper":
Results; front side of the pattern done:
A little sanding.....
And a little epoxy....
When we have some time...ok a lot of time, we will glue up a 3 bladed blank and use the master template to make our own prop for our Cozy, we will probably decrease the pitch a few degrees in favor of a good climb for initial flights.
Other people's propeller sites, our inspiration and also so you will know we are not out of our minds:
Al Wick's propeller page: http://www.maddyhome.com/canardpages/pages/alwick/prop.html
Lee Devlin's propeller page: http://k0lee.com/propfab.html
Nick Ugolini's propeller page: http://mywebpages.comcast.net/unick3/Nicks Website/Prop Number1/PropStart.htm
Phillip Johnson's propeller page: http://www.canardzone.com/members/PhillipJohnson/Propeller/propeller.htm
Mathieu Gratton's propeler page: http://www3.sympatico.ca/mathieu.gratton/Props4sep04.htm
Some interesting ideas from Jukka Tervamaki: http://www.icon.fi/~jtki/prop.html
"How I Make Wood Propellers" PDF by Al Schubert
Bates Engineering Propeller Design Software: http://www.geocities.com/aeroopt/prop.htm
JC Propeller Design Program: http://www.jcpropellerdesign.com/
The ultimate propeller carver: http://www.wood-carver.com/gemini.html