Spoke with Warp
Drive today about a prop. Their
number is 641-357-6000. They said I
would require at least 3 blades for 180-200 HP from a Mazda with 2.178
redrive. Over about 220 HP, I’d
have to go with 4 blades. A 2.85
redrive would also require a 4 blade even for 180 HP. This is to be able to absorb the power
without overstressing the blades. They said
a 3 blade prop on the Mazda would be extraordinarily smooth. Gotta like that.
They recommend
that I start with the standard blade, rather than the tapered blade, because
they think I’ll need all the tip area I can get for the power. Once it’s flying, and I give them some
numbers, they can determine if some tapering will help, and the blades can be
tapered at that time.
There’s really no
limit to the blade angle, other than cavitation. They said 22 degrees (about 82”) pitch
was the limit before some cavitation would occur.
Rain will erode
the prop leading edge, unless you slow the prop down to 2200 RPM or less, or
unless you have the Nickel leading edge strips. They cost $40 per blade, and are always
added as the last step, so they can be added at any time after the prop has been
in service. In fact, they recommend
flying the prop first to finalize the length and shape of the blades, then
having the LE strips added. It
might be worth flying the prop until the rain proves to be a problem, then
having the strips added if necessary.
Probably won’t be needed for me.
They recommend a
max prop tip speed of 850 fps, which is about what I’ll end up with at
cruise. The prop can be run faster,
and 3400 rpm for a 7000 RPM engine run should be no problem.
They sell
fiberglass spinners as well, and have a 12” available for about $160. It will completely cover the prop
hub.
At this time,
nobody makes a variable pitch hub for the warp blades at this power level.
They did warn me
that their prop will always be a bit slower on top speed than a properly made
2-blade wood prop. He said it
should be within 10 mph though.
Small price to pay for an adjustable prop.