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Old Jun 12, 2012, 12:02 PM
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Reco's Avatar
USA, NC, Greensboro
Joined Mar 2002
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Originally Posted by jofro View Post
I was working out your 18 pounds AUW at 4000watts, which gives you some 220watts per pound. You didn't say anything about your "supposed" 12lb thrust, which is all subject to your inlets, outlets and other factors. Did you test your thrust? If you get 1320g/Kw you are laughing. I find the easiest way to check my real thrust, by holding the model in vertical position with exhaust 4-5 feet above the ground or higher and get someone to advance full power. If she hovers I'm happy chap. My 17kg "Triptych" pulled out of hover between 3/4 to full stick, meaning it must pull over 18kg. 10.5kg "Panther" almost but not quite hangs there on 9300watts at some 200 amp draw with 127mm fan. So both models produce some 400w/lb. With your 18pound Hornet it shouldn't be any problem to do vertical test to see what she really pulls. But then again, there is static and dynamic thrust and to get best of both takes some experimenting, Joe.
Along the same line as Joe here, I have always wondered if hanging the model from the tail attached to a digital fish scale and having full throttle brought up then taking the thrust from the reading would work? If I ever tried this I would probably use saddle straps around the wings to hold it up. Just a thought..
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Old Jun 12, 2012, 12:10 PM
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JurassicJet's Avatar
United States, WI, Chetek
Joined Jul 2011
470 Posts
Quote:
Originally Posted by Reco View Post
Along the same line as Joe here, I have always wondered if hanging the model from the tail attached to a digital fish scale and having full throttle brought up then taking the thrust from the reading would work? If I ever tried this I would probably use saddle straps around the wings to hold it up. Just a thought..
Hanging an aircraft from the tail and running it full power would be a really bad idea. If the aircraft weighed 35 lbs and you added 25 lbs of thrust you are talking 60 lbs of stress on the aft fuselage and empenage area.

Better to put I nice thick strap around it while sitting on the ground and use a fish scale for a static thrust reading. even a strap around the leading edge of the wings would be better IMHO.
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Old Jun 12, 2012, 02:36 PM
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Joined Apr 2003
451 Posts
Quote:
Originally Posted by JurassicJet View Post
Hanging an aircraft from the tail and running it full power would be a really bad idea. If the aircraft weighed 35 lbs and you added 25 lbs of thrust you are talking 60 lbs of stress on the aft fuselage and empenage area.

Better to put I nice thick strap around it while sitting on the ground and use a fish scale for a static thrust reading. even a strap around the leading edge of the wings would be better IMHO.
To check the thrust in turbine model aircraft, I know of guys who placed a bathroom scale against a wall (or other immoveable surface), placed the nose of the aircraft against the plenum of the scale with the aircraft on its wheels on the ground, and ramped it up to full power.

Assuming that the nose of your T-38 is stout enough, this would be an easy way to determine the static thrust.

-- Mark
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Old Jun 12, 2012, 02:53 PM
RC Fanatic
Reco's Avatar
USA, NC, Greensboro
Joined Mar 2002
1,333 Posts
Quote:
Originally Posted by JurassicJet View Post
Hanging an aircraft from the tail and running it full power would be a really bad idea. If the aircraft weighed 35 lbs and you added 25 lbs of thrust you are talking 60 lbs of stress on the aft fuselage and empenage area.

Better to put I nice thick strap around it while sitting on the ground and use a fish scale for a static thrust reading. even a strap around the leading edge of the wings would be better IMHO.
True if you hung it from the tail, I was talking about using straps around the wings. I think the wings could hold that weight. Using the ground method would suffer from the drag of the wheels.
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Old Jun 12, 2012, 03:12 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
4,959 Posts
I'm sure this is a great idea, but don't forget this is 12 feet long!! He may have to rent some hanger space to do it. How many of us have a 15-16 ft ceiling you could hang it from. Then there is reading the scale!
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Old Jun 12, 2012, 03:26 PM
Low rates are for wimps
bwoollia's Avatar
United States, CO, Colorado Springs
Joined May 2008
3,237 Posts
CONGRATS ON THE MAIDEN! Looks like it flies like a pussycat!
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Old Jun 12, 2012, 03:32 PM
Capt. Z
falcon5's Avatar
Tonopah, Nevada
Joined Dec 2004
2,540 Posts
Well I took the day off from work today and guess were I went...yep back out to the lake bed. I flew the T-38 and she fly's beautifully. Yeah a bit under powered as we expected but that can be fixed. I will give a detailed flight report a little later but for now enjoy the video..My only request is you crank up the volume to neighbor busting levels on the two low passes...man those two Stu fans and that big airframe sound SWEET!!!

My retracts are not up to the challenge of a 40 pound plane rated for only 20 pounds and it showed. Nose motor not strong enough to retract the gear against the head wind, Right main only retracted 3/4 of the way up. I cut the flight short seeing this and worked on getting the gear back down. Mains came down nose gear only 3/4 of the way down due to a striped jack screw but did not fold on landing. Phew!!

I am going to invest in a real nice set of retracts for the jet that are properly rated for 40 pound planes,

Quick run down:
Fly's like it's on rails, a real SWEET flying airplane!!!
Aerodynamically the airframe absolutely does not care it weighs 40 pounds and from how it handles I would guess it wouldn't care if it weighed 50 pounds as long as it had the proper power plant.

Lands like a feather.

T-38 maiden1.wmv (4 min 25 sec)
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Old Jun 12, 2012, 03:42 PM
Registered User
Slovakia, Veľký Krtíš
Joined Dec 2006
666 Posts
Flying beauty...congratulation...I especially like smooth landing...It fliees like a glider
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Old Jun 12, 2012, 03:43 PM
Fly it like you STOL it!
Endlesslag's Avatar
USA, VA, Spotsylvania
Joined Jan 2011
3,993 Posts
Quote:
Originally Posted by falcon5 View Post
Well I took the day off from work today and guess were I went...yep back out to the lake bed. I flew the T-38 and she fly's beautifully. Yeah a bit under powered as we expected but that can be fixed. I will give a detailed flight report a little later but for now enjoy the video..My only request is you crank up the volume to neighbor busting levels on the two low passes...man those two Stu fans and that big airframe sound SWEET!!!

My retracts are not up to the challenge of a 40 pound plane rated for only 20 pounds and it showed. Nose motor not strong enough to retract the gear against the head wind, Right main only retracted 3/4 of the way up. I cut the flight short seeing this and worked on getting the gear back down. Mains came down nose gear only 3/4 of the way down due to a striped jack screw but did not fold on landing. Phew!!

I am going to invest in a real nice set of retracts for the jet that are properly rated for 40 pound planes,

Quick run down:
Fly's like it's on rails, a real SWEET flying airplane!!!
Aerodynamically the airframe absolutely does not care it weighs 40 pounds and from how it handles I would guess it wouldn't care if it weighed 50 pounds as long as it had the proper power plant.

Lands like a feather.

http://www.youtube.com/watch?v=WBF_Pf2uGFQ
Freakin AWESOME!!!!!
I've been following since the beginning, and this made my day! Keep it up! MOAR POWAH! And now that it flies, get a film crew with a really nice camera out there to capture it in it's full glory
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Old Jun 12, 2012, 03:47 PM
Crikey never leave beer behind
steve wenban's Avatar
Mt Annan Sydney Australia
Joined Dec 2003
23,033 Posts
Absolutely bloody fabulous mate ,well done glad I stayed around to see the end result. Power is not my normal outlet but this was something special. Excellent ,ok what next then ?
Cheers
SteveW
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Old Jun 12, 2012, 03:49 PM
Fly it like you STOL it!
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,821 Posts
Congrats!
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Old Jun 12, 2012, 03:53 PM
it wasn't me flying that plane
Hover or die's Avatar
United States, NC, Wilmington
Joined Mar 2011
704 Posts
Great flight and so so well deserved...We are all sorry for working your nerves over the last few days Andy..
I bet the after beer was especially good!!!
Take care and tell me........What's next.....lol.....
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Old Jun 12, 2012, 03:55 PM
Have Fun! Land, Sea or Air
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United States, TX, Austin
Joined Jul 2006
1,353 Posts
Way to go falcon! Congrats!
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Old Jun 12, 2012, 03:55 PM
building building building!
aerophilia's Avatar
Melbourne Australia
Joined Jun 2006
5,042 Posts
Yeehaa!! Nice one Falcon. So great to see it in the air. Congratulations. Was that on 10s?
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Old Jun 12, 2012, 03:59 PM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
21,492 Posts
curse you youtube work filter block!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

awesome andy!!! how did the cg feel?

you should have rolled it over and retracted them lol. thats what i do when they arnt strong enough.

i have to wait for friday to see the video now...you suck lol!!!

i guess my home brew airfoil works after all haha.

we need a in depth report wingman
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