For a SeaWind Doug I think you will need a 3 rotor. What is the gross
weight?
We have several people on here building SeaWinds with three rotor engines.
Paul Lamar
SeaWind gross weight seems to be a moving target:) I have been told
anywhere from 2250 to 2650. My sole goal in life at the moment is to
lighten the plane up through good fabrication techniques and substitution of
carbon fiber in some components. Obviously I am aiming towards the lower
figure. The prototype SeaWind flew with a 200hp engine. Presently a few SWs
are now flying with 250Hp and long water takeoffs can be done but it is
generally recommended to have 300Hp for the water.
I want this plane to go high and far, as in around the world. Even though
the plane has lots of room for fuel tanks I'll still need to have a good
fuel burn or I'll be treading water in the Pacific Ocean.
I have some friends in San Luis Obispo I usually stop in and see so I can
stop by on the way. Anything small you want me to bring over from this side
of the pond?
Cheers
Doug
Well you can always take a tip from Ken Welter and use nitrous oxide to get
up on the step. Might be hard to find in some parts of the world however.
Ken's Coot grosses close to 3000 pounds with 100 gallons of fuel.
If you choose a 2.85:1 PSRU you should be able to swing a 74 or 76 inch
prop at 7200 to 7800 engine RPM for good low speed thrust. An electric
Hoffman or MT variable pitch prop would also help greatly getting up
on the step and still giving a good cruise speed.
Paul Lamar
Hi Paul,
Yes I've heard about Ken's Coot. I believe my gross with 110 gals of fuel
plus other gear will be closer to 3400lbs. Over long ocean stretches I may
have to carry another 200 lbs or more of fuel and let the my 110lb wife take
a commercial flight with our baggage. I will be taking off at gross only on
land however.
Doug
How important is 20% lower fuel burn to you? Are you willing to do some R&D
on turbo compounding? The big problem is the turbine gear box. There is not a lot
of torque from an exhaust blow down turbine but there is a lot of RPM.
That calls for a tiny sun gear, large dia. narrow planet gears and a large
dia. narrow ring gear. Gear boxes like this are standard equipment in APU's.
The turbine gear box will only need to handle about 40 HP max for takeoff and
about 30 HP for cruise.
Paul Lamar
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