Ok, this thread has gotten huge, but as promised I called the Warp Drive
folks again. And of course, my memory "ain't what it used to be." They
know of no application in use with their props running at 350 mph
forward velocity.
There were many caveats, like amphib versus airplane versus airboat, and
massive power strokes to the prop (like Lyc's and Continentals) and
several others I don't remember, BUT, in general:
1. the Warp Drive props are outstanding in low speed and horsepower
ranges
2. 2 blades can be used up to about 100 hp,
3. 3 blades must be used above about 100 hp to about 160-180 hp,
4. 4 blades must be used above the 160-180 hp range,
5. 200 hp is about their total limit,
6. 200 (kts or mph?) is about the upper limit for their speed range
7. for cruise in the 175-200 mph range, the multi-blade Warp Drive
solution will be about 7 mph slower than a top-notch wood prop, but
equal or better to the heavier metal props,
8. at max speeds above about 175-200 mph, the Warp Drive will be approx
15 mph slower,
9. one gets much better static and take off thrusts with engines below
200 hp due to the much lighter weights of the Warp Drive carbon blades
(several caveats there, too.)
10. a multi-blade Warp Drive solution will get an amphib up on step much
quicker than almost any other type of prop solution,
11. with my 143 hp Ford engine in a Mustang II, and optimized for
cruise, I may lose as much as 5 mph max cruise (not max overall speed)
as compared to an optimized wood prop, but the carbon prop will last
many years longer and will take off and climb better. Further, my CG is
greatly enhanced with only 12 lbs hanging in front of the engine. It's
almost the ideal solution for my (isolated?) situation. By adding wheel
pants, I can get nearly 20 knots back according to Ken Paser anyway.
12. The 3 bladed Warp Drive with nickel leading edge solution costs from
1/2 to 1/8th the next nearest in efficiency for my app.
Whew! There is more but I have forgotten by now 8-).
HTH,
AI Nut
This is a lot of marketing hype:
Comments:
1: Perhaps true.
2: 50 hp per blade.
3: 60 HP per blade. (?)
4: 50 HP per blade.
5: 50 HP per blade.
6: IIRC, their blades have no twist, so this seems pretty high.
7: I doubt it. Metal props are typically a 2-5% more efficient than wood
props. Thicker is less efficient, esp at higher tip speeds. The LAEV is
going to be a few percent less efficient than an ultra thin tipped prop to
make it A) produce better T/O and climb thrust and B) structurally much
more robust. Planned that way.
8: Very substantial differences in efficiency cause relatively small
differences in
top speed due to the HP required being a CUBE function of speed. 7mph
slower is a LOT less efficient. 15 mph is a huge loss. If you assume a
prop delivering 200 HP to the air and a speed of 175 mph; at 160 mph the
HP delivered to the air is 153 HP (cube function). This implies that
the 15mph
slower prop is 77% as efficient as the prop that will drive the A/C 200 mph.
Extremely poor efficiency. This is an example of how top speed is a very
poor
indicator of the effectiveness of a prop.
9: This is nonsensical. The weight of the prop has ZERO effect on anything
except initial acceleration of the prop from one RPM to the next (tiny
effect)
and the direct effect on the weight of the aircraft. Prop weight does
not affect
prop thrust in any way. The quicker RPM acceleration is probably on the
order of less than 1/2 second saved in coming up to RPM.
10: This means that their design has good thrust at very low speeds. This is
often a harbinger of poor high speed performance. I think these were
originally
designed for ultralights where the entire performance envelope is covered by
less than 60 mph. For this application, untwisted thick blades are
reasonable.
They are far off optimum for higher speed ranges. (If I am thinking of the
correct blades, they are relatively thick, constant chord and untwisted).
11: A climb-pitched wood prop should provide similar T/O & climb perf, with a
similar penalty in cruise speed. My wood prop weighs about 7-8 lbs.
Expecting
20 kts from wheel pants is expecting a lot. I got about 8 kts on my LE. My
Great American thin-laminate wood prop has 800+ hrs on it and has NEVER
been repaired due to FOD because of the urethane leading edge and
kevlar mat wrap on the blades. My "real" aluminum props have MUCH more
FOD over that time period. I will lobby for a urethane LE and kevlar wrap on
the "production" LAEV blades. Perhaps not for the initial prototype blades.
I watched Jeff Ackland (Legend turbine homebuilt) do his testing of a
Glassair II
which he replaced a 150 Lyc with a "200 hp" Blanton-Ford V6. Dramatically
less performance across the board. I'll bet the actual hp was more like
100-110,
and a lot heavier. He swapped it back after about 6 months of trying to make
it work. Best of luck with the Ford V6, perhaps you can work it out better and
get more performance and reduce the installed weight.
Be careful believing everything a salesman tells you, some of it is in error
and
some of it is a lie. This is why Physics is an important class for
everyone. ;-)
Bill Freeman
Long EZ builder & pilot
BSME, MSME
EAA Technical Counselor
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