Paul I respectfully disagree. One of the biggest troubles for some
systems, like a 20B
RV-10 will be the lack of a CS prop. That is saying that a fixed pitch
won't work at all
but carrying enough pitch for cruse/top speed will lengthen takeoff
distance by a
significant amount.
Bill Jepson

Not if you start with a p-port 3 rotor. How many RV10 out there have 375
HP?

Paul Lamar

I also disagree about the need for a PRSU that will handle a CS prop, but
when I looked at the Variprop website, its only rated for 300hp. If a NA
20B P-Port will make 375hp (not sure about that), I'm not sure it would hold
up. Certainly the 20B P-Port will make more that 300 hp in any case. I
think the greatest need is for a PRSU that will take a CS prop. At this
point, everyone just has to settle for what we can get and hope for a new
product!!

Don

Don,
I'm in total agreement with Paul that a P-port 20B will make major HP. In a talk with
Daryl Drummond he said you would have to intentionally hold it back to make only 300!
I agree that it would be best if the CS could be a light one. Senstitch (sorry I never
could
spell their name right) Is doing a new all composite CS. Egg Subaru has been selling them.
They have several blade configurations. Just a possibility.
Bill Jepson

Hi Paul,


This may be a good time for a survey. IE Everyone who would pay XXX dollars
MORE to have Constant Speed Prop Capability---line up here.  Everyone who is
positive they will Always Be Content with Fixed Pitch ----line up here.
Even if a builder never uses the capability of the hollow shaft, he/she may
want it simply to enhance the aircraft value at resale time.  The big
question is "How Much???" There is about a $5000 difference between a CS
prop and a Fixed pitch, and a Governor can be bought for around $2000
rebuilt.  These are investments you can chose to make OR CHOSE NOT TO MAKE
if you have a hollow shaft.  If you have a solid shaft this option is not
available.  I've been very intimate with Tracey's gearbox and have not yet
found a way to adapt it to a CS prop that I would feel comfortable flying
with, so I believe a "clean sheet" design would be approiate.


I have also
watched your Rhino renderings for PSRU's.  I have no feel for how much
more/less your new designs would cost COMPLETE, but for the most part I
cannot see where a hollow shaft vs solid shaft should cost more than around
$500 dollars differential.  Most of that differential is simply in the cost
for large bearings which seem to get exponentially more expensive with size
increase.  The two big costly problems a CS PSRU must overcome are bearing
size/life and seals which must now retain high pressure instead of just
drain pressure.  A fair survey would have to account for the additional
cost, but I think the results maysurprise you.

Dave M

It is not just the price and extra weight of the PSRU. Constant speed props are not cheap. They are in the category of $10,000.  Mark S is apparently rich :)

Paul Lamar