Russell Kent wrote:

Ed Anderson wrote:

Contacted Finn and he will lend me his chut should there be a

flight test of the

LAEV.

I have one thing to say regarding the testing of the LAEV on Ed's

plane before the

tilt-a-whirl torture test: how is this going to look in the NTSB

accident summary?

Russell Kent

Risky business.  Like any homebuilt activity, you want to test

everything possible on the

ground before taking to the air. That's why I recommended several full

power runs down the

runway. Another thing to consider, LAEV has wide-chord blades. So Ed,

with the same pitch as

your fixed-pitch prop, you may not turn up the same RPM. I think you

said 68 inch diameter

prop?  LAEV is 72.

Perry

Hi Perry,

72"!, Yes, you are correct, that increase in diameter will undoubtedly made
rpm/pitch comparisons unfeasable.  That bascially means I will get more
thrust than my current prop but run lower engine rpms.  It will interesting
to see.  My engine is turning my current prop up to 5800 rpm during static
run up.  I believe that is due to the prop stalling and producing less load
enabling the engine to turn high rpm  and not necessarily producing more
thrust.  One the other hand, since I don't have a thrust meter attached -
perhaps the engine is producing a bit more HP.

I forget now who did the prop dimension calcuations, but I was wondering if
the program would give the calcuated thrust for a 68x72 (length x pitch)
runing at say 2300 - 2500 rpm.  Then calculate the rpm for the LAEV prop to
give the same thrust.  That way I would have some assurance that of what
engine rpm would be adequate to get me airborn with the LAEV prop.

Thanks

Ed Anderson

I think Bill did the original calcs but Vance can get us in the ball park.

We can also measure the static thrust of your plane with the prop it has.
We just need a couple of calibrated garage door springs. Or a pulley, a long rope
and a 50 gallon garbage can or drum partially full of water. (400 pounds max.). Start with
course pitch and reduce the pitch until the new prop equals the
current prop in static thrust. At that point that becomes the
lower limit of the fine pitch setting for the new prop.

The reason you don't want to get the pitch setting too fine (if you are
going to fly with that fixed pitch setting) is it could run out of thrust at
the higher air speeds if the engine were RPM limited. This probably
does not apply in our case as your rotary engine will continue to
increases its HP right up to 8000 RPM or so. All should be OK
in this regard.

A few taxi runs and you will know right away if things are OK as
the acceleration difference will be noticeable. We can also
mark the sides of the runway at Shady Bend every 100 feet.
If you are not off the ground in the same number of feet
or less you can abort.

BTW the long rope would come in handy. We can tie the tail to a
tree and I can raise and lower the tail rapidly while you are in the cockpit
running the engine at max. static RPM. Any blades flying off will
fly off radially. If they do we may never find them in the jungle
down there :)

Paul Lamar

Paul, I thought that was the beginning of the desert, we could drive all over the place, and
there is even an open field next to the Run Way :-)
Royce

Beginning of the desert? Shady Bend? The open field is a new development.
That used to be jungle :) 

Paul Lamar
 
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