up-thrust change...what affect???
07-23-2007 | 04:18 PM
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From: Canaan,
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up-thrust change...what affect???
i'm in the proccess of dialing in more downthrust on my engine setup and was wondering if i should expect any change in my next take off behavior. i've noticed that the plane likes to climb a bit under acceleration. i'll stick a couple of washers behind the top mounts and try it again. this is a tail dragger but the tail doesnt lift before take off. the plane just goes up on it's own and i'm kind of used to this behavior. just wondering what to expect after these changes. any input would be great. i'll post my observations after the next flight. this plane flys really well. someone in the club mentioned that the engine looked like it might have too much upthrust so i took a look at it and agreed. hey...while i'm here...anyone fly a modeltech magic? i just orderd one and will be mounting a magnum 52 on it. i flew a friend's magic last week and it was great. it had a saito 40 and was a blast to fly. thanks fellow flyers..have a great day
07-23-2007 | 07:52 PM
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From: Jacksonville, FL
RE: up-thrust change...what affect???
If i remember right, the way to check for proper down thrust angle is to fly at 3/4 throttle inverted. then cut power if your plane gains altitude then you had too much up thrust.
tail not coming up on take off...there are a few things or combination of things which might cause this too slow a take off, tail incidence wrong(down) wing incidence wrong (up) cg tail heavy.
the aircraft gaining altitude when power is applied is normal
since your changing the thrust angle be ready on the elevator on take off, and you might have to have some back pressure on the elevator with power applied
Good Luck
tail not coming up on take off...there are a few things or combination of things which might cause this too slow a take off, tail incidence wrong(down) wing incidence wrong (up) cg tail heavy.
the aircraft gaining altitude when power is applied is normal
since your changing the thrust angle be ready on the elevator on take off, and you might have to have some back pressure on the elevator with power applied
Good Luck
07-23-2007 | 08:36 PM
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RE: up-thrust change...what affect???
ORIGINAL: bobrev06x
i'm in the proccess of dialing in more downthrust on my engine setup and was wondering if i should expect any change in my next take off behavior. i've noticed that the plane likes to climb a bit under acceleration. i'll stick a couple of washers behind the top mounts and try it again. this is a tail dragger but the tail doesnt lift before take off. the plane just goes up on it's own and i'm kind of used to this behavior. just wondering what to expect after these changes. any input would be great. i'll post my observations after the next flight. this plane flys really well. someone in the club mentioned that the engine looked like it might have too much upthrust so i took a look at it and agreed. hey...while i'm here...anyone fly a modeltech magic? i just orderd one and will be mounting a magnum 52 on it. i flew a friend's magic last week and it was great. it had a saito 40 and was a blast to fly. thanks fellow flyers..have a great day
i'm in the proccess of dialing in more downthrust on my engine setup and was wondering if i should expect any change in my next take off behavior. i've noticed that the plane likes to climb a bit under acceleration. i'll stick a couple of washers behind the top mounts and try it again. this is a tail dragger but the tail doesnt lift before take off. the plane just goes up on it's own and i'm kind of used to this behavior. just wondering what to expect after these changes. any input would be great. i'll post my observations after the next flight. this plane flys really well. someone in the club mentioned that the engine looked like it might have too much upthrust so i took a look at it and agreed. hey...while i'm here...anyone fly a modeltech magic? i just orderd one and will be mounting a magnum 52 on it. i flew a friend's magic last week and it was great. it had a saito 40 and was a blast to fly. thanks fellow flyers..have a great day
A guy told me that to much up thrust would cause this along with incidence issues. You'll see the plane now in "My Models" after the rebuild as i rebuilt the firewall and readjusted the incidence (this was an Arf). Been fine ever since. Later
07-24-2007 | 02:41 AM
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From: Warialda NSW, AUSTRALIA
RE: up-thrust change...what affect???
G'day Mate,
You don't say what the plane is, or what the wing airfoil shape is, but if it climbs excessively, with lots of down trim, & has a flat bottom wing, it needs more down thrust, you won't notice anything at take off, but you may need to retrim your elevators.
If it has a symetrical airfoil, try this test, fly it into the wind, out in front of you, trim it for straight & level at full throttle, then at a resonable altitude, cut the throttle to idle, don't touch the elevators, & watch what the plane does, if it pitches up, you have too much down thrust, you have added lots of up trim to counteract the excessive down thrust.
If it pitches down you need more down thrust, opposite to the above.
If it stays level & slowly sinks as it slows down, it is good.
You don't say what the plane is, or what the wing airfoil shape is, but if it climbs excessively, with lots of down trim, & has a flat bottom wing, it needs more down thrust, you won't notice anything at take off, but you may need to retrim your elevators.
If it has a symetrical airfoil, try this test, fly it into the wind, out in front of you, trim it for straight & level at full throttle, then at a resonable altitude, cut the throttle to idle, don't touch the elevators, & watch what the plane does, if it pitches up, you have too much down thrust, you have added lots of up trim to counteract the excessive down thrust.
If it pitches down you need more down thrust, opposite to the above.
If it stays level & slowly sinks as it slows down, it is good.
07-25-2007 | 04:52 AM
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From: Canaan,
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RE: up-thrust change...what affect???
ok, i flew this plane last night two times. the first time, i spent most of the flight observing and re-trimming. it was just a bit on the windy side so it took me a while to get it where i was satisfied. the take off was much flatter and better looking by far. second trip, i flew inverted quite a bit and noticed a huge difference in the way it handled. very little down elevator was needed compared to before. the landing was very different from before. i need just a click more throttle on my final. this was a very positive adjustment for this plane and i am very pleased. this plane is a low wing 60 scale sport/scale plane with a 61 two stroke, (soon to get a 91 four stroke) similar in design to an edge...for those wondering. should be posting a video soon. thanks for all the help . happy flying.
