Also keep in mind that these model engines have a TBO of 25 hours.

Mike Schumann

wrote in message
oups.com...
Bob Carlton converted a Silent to jet power (and it is anything but
silent!):

http://www.silentwingsairshows.com/jet.html

He uses two 45 lb thrust model a/c jets. The engines are small and
light, but it burns about 18 gallons per hour. For a 1000 lb glider you
will need 4 of these puppies, pushing fuel burn to 36 gal/hr (my DG-400
burns 5 gal/hr). Going with less than 4 means a longer takeoff run (a
LOT longer!). How long? Try F = M*A, or A = F/M, where F is the USEABLE
accelerating thrust, M is the mass of the glider and A is acceleration.
Remember that for useable acceleration you need to subtract off the
rolling resistance from engine thrust (pull your glider with a rope and
a BIG fish scale to measure this). Four engines also increases the risk
of engine failure by a factor of 4. Of course, you could still climb
with only 3, just slower.
Also, the 25:1 glider ratio doesn't apply because you have the
additional drag of the engines and pylon. Jets help here because of
their small size, but 4 of them will probably knock your glide angle to
under 20:1.

Tom Seim
Richland, WA