tim tracey wrote:

 I'm finally to the stage where I can start looking
 really hard at the actual build-up of my 13B for my
 pusher config......I'd appreciate any and all
 suggestions(no matter how outrageous)as to producing a
 consistently high HP output at 4,000-4,500RPM. The
 unit will be geared 2:1 to an inflight adjustable
 3-blade 58" prop with 30-105" of pitch and oodles of
 blade area.

 I am now lowering my shields........LOL!

Why? I understand Perry Mick setting up his ducted fan Long eze with the
goal of avoiding the use of a PSRU. It hasn't been a convincing performer,
but has met Perry's goals some what. But if you are going to to all the
trouble of a PSRU, what does holding the rpm to 4000-4500 gain you? If you
want a slow turning, large Diameter prop for noise abatement, or low speed
thrust, or looks on an antique, then get on Tracy's list for a 2.85:1 RD-1C
and tune your 13B for 6000 rpm.

58"@ 2000rpm is 154 m/s or about 0.52M (sea level). Well below the 0.75M
recommended for wooden props or up to 0.8M for composite and metal props
with thin tips.

A 58" prop with pitch to 105" and oodles of blade area is a high speed, high
altitude prop and turning it at 2000 rpm sounds like it might just stir the
gravy, but won't beat the cream in time for thanksgiving :)

Can you get a refund on the prop, or exchange it for something more usable?

Mark Wrathall

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