Asymmetrical thrust
02-01-2013, 07:30 AM
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Asymmetrical thrust
The ongoing thread re repercussions of a one-engine FO on a twin-engine jet brought up an old interest. Sometime back, and I can't find the reference, a 'center-line thrust' type twin (F-15?) using a single pipe, outletting thru just one nozzle, was proposed and analysed; perhaps flown, as well. The engine was at a bit of a diagonal, then, the outward angling nozzle expected to counter the off-line (asymmetrical) thrust. The idea, of course, being that the thrust line thru the CG and the slight vectoring of the nozzle would counter the off center thrust. I.e., less loss thru a single pipe than a split one, w/ less pipe weight, vs some minimal crabbing easily countered. Maybe hardly worth it w/ our high T:W models, but:
Anton has flown the new Sky Master X-treme F-15 using a JC 60, says it's 'almost overpowered', and indicated a Wren 44 Gold might be 'perfect'. And, perhaps by using the above method w/ a Wren, an even 'more perfect' model might be achieved
. A small split pipe will lose as much as a half-pound thrust, this vs a half-pound increase using Wren's augmented single pipe, should result in about a one pound thrust advantage over a bi-pipe. Plus whatever the weight difference of the single pipe. IOWs, a 15-pound wet weight(?) model w/ a bi-pipe would have an approximate thrust of 9.5 pounds vs, say, a 14-3/4 pound model w/ 10.5-pounds thrust. Significant difference, I'd think (T:W of .633 vs 7.1). Antons T:W was about .77, if the model weighed 15.5-pounds (JC60 is 8-oz heavier than a Gold).
Anyone recall an asymmetrical thrust model; Anton...what did your JC60-powered F-15 actually weigh (empty; full)? Flaps, ailerons? Tx, everyone for your comments!
Ray
Anton has flown the new Sky Master X-treme F-15 using a JC 60, says it's 'almost overpowered', and indicated a Wren 44 Gold might be 'perfect'. And, perhaps by using the above method w/ a Wren, an even 'more perfect' model might be achieved
. A small split pipe will lose as much as a half-pound thrust, this vs a half-pound increase using Wren's augmented single pipe, should result in about a one pound thrust advantage over a bi-pipe. Plus whatever the weight difference of the single pipe. IOWs, a 15-pound wet weight(?) model w/ a bi-pipe would have an approximate thrust of 9.5 pounds vs, say, a 14-3/4 pound model w/ 10.5-pounds thrust. Significant difference, I'd think (T:W of .633 vs 7.1). Antons T:W was about .77, if the model weighed 15.5-pounds (JC60 is 8-oz heavier than a Gold). Anyone recall an asymmetrical thrust model; Anton...what did your JC60-powered F-15 actually weigh (empty; full)? Flaps, ailerons? Tx, everyone for your comments!
Ray
02-01-2013, 08:35 AM
#6
RE: Asymmetrical thrust
Hi, Ray
I think you are mistake , I flew the Sky e master F-15 EDF conversion to 6 kg thrust. not XTreme F-15,
here is web page, http://www.skymasterjet.com/ef15.htm
the F-15 Length: 1760 mm(69”). Wingspan: 1125mm(44.3”).
dry weight : 7.8kg (without the ailerons / only Flaps with elevons and rudders)
http://youtu.be/lkOj-ZTThYM
Best regards
Anton
I think you are mistake , I flew the Sky e master F-15 EDF conversion to 6 kg thrust. not XTreme F-15,
here is web page, http://www.skymasterjet.com/ef15.htm
the F-15 Length: 1760 mm(69”). Wingspan: 1125mm(44.3”).
dry weight : 7.8kg (without the ailerons / only Flaps with elevons and rudders)
http://youtu.be/lkOj-ZTThYM
Best regards
Anton
02-01-2013, 04:03 PM
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RE: Asymmetrical thrust
Mick...that's very encouraging.....glad someone beat me to it and had a good experience!
Anton.......beautifully flying model(!), and you are correct, of course, I was mistaken re which model. The S60 certainly seems plenty of power!
It is a much greater weight than I hoped (17-pounds dry)....and I'm amazed it's that heavy. How heavy is an EDF version? With 48-ounces of fuel, that would add another kilo (2.2-pounds)....over nineteen pounds at take-off; perhaps a T:W of 1:2 using a split pipe 44 Gold. And that would be enough power ('perfect power'); enough for decent vertical maneuvers like loops, etc.? What would a grass TO distance be do you guess? Tx!
Ray
Anton.......beautifully flying model(!), and you are correct, of course, I was mistaken re which model. The S60 certainly seems plenty of power!
It is a much greater weight than I hoped (17-pounds dry)....and I'm amazed it's that heavy. How heavy is an EDF version? With 48-ounces of fuel, that would add another kilo (2.2-pounds)....over nineteen pounds at take-off; perhaps a T:W of 1:2 using a split pipe 44 Gold. And that would be enough power ('perfect power'); enough for decent vertical maneuvers like loops, etc.? What would a grass TO distance be do you guess? Tx!
Ray
