Skymaster F-4
#51
My Feedback: (25)
Here is my current setup. You will notice the blistering on the stab. I started the engine for 45 seconds and immediately shut her down when I noticed the heat issue. The second test run...I put the 1000 degree tape and a coat of 1000 degree silver paint....I still saw signs of heat damage after 30 seconds of run up at idle only.
I open to suggestions.....Ive considered flipping the Pipe...but it wont fit without major grinding and adjusting the angel of the exhaust nozzles. I have some room to grind the rear formers down to get a bit more of a down angle...but will have to raise the engine mounts too...to avoid getting hot spots on the pipe.
I open to suggestions.....Ive considered flipping the Pipe...but it wont fit without major grinding and adjusting the angel of the exhaust nozzles. I have some room to grind the rear formers down to get a bit more of a down angle...but will have to raise the engine mounts too...to avoid getting hot spots on the pipe.
#52
Hi
I flipped the skymaster pipe upside down, but grinded the upper part of the formers. With the turbine at 6º down, it flew wonderfull today
For those who remember, I toasted my stab a year ago. Now it is covered in flitemetal with rivets and so on and there is NO ABSOLUTE SIGN of heat in the stab
Cg at 330mm
Happy man today
Regards
Nuno
I flipped the skymaster pipe upside down, but grinded the upper part of the formers. With the turbine at 6º down, it flew wonderfull today
For those who remember, I toasted my stab a year ago. Now it is covered in flitemetal with rivets and so on and there is NO ABSOLUTE SIGN of heat in the stab
Cg at 330mm
Happy man today
Regards
Nuno
#53
My Feedback: (13)
BLUF: how do you service the air/oil nose strut?
I'm assuming you input a volume of x weight car shock oil, cap it and then add air pressure
Ive been able to deduce its 40psi but I don't know the volume or weight of the oil.
I asked a buddy today today but he said "fill the oil to the top". That doesn't do it in that it creates a hydrolock (unless I'm using too heavy an oil"
thanks in advance
Dave
I'm assuming you input a volume of x weight car shock oil, cap it and then add air pressure
Ive been able to deduce its 40psi but I don't know the volume or weight of the oil.
I asked a buddy today today but he said "fill the oil to the top". That doesn't do it in that it creates a hydrolock (unless I'm using too heavy an oil"
thanks in advance
Dave
#55
My Feedback: (13)
Joe,
thank you. I knew I saw it somewhere but couldn't find it
Two errors on my part:
1. Using high viscosity shock oil. The ATF worked great!
2. I filled the strut full on the extended position and then capped it. The right answer is bleed it, compress it, then cap it.
I think the book says 37-52 psi. That seemed high for the nose strut. That must be a measurement for the mains
thanjs again
Dave
thank you. I knew I saw it somewhere but couldn't find it
Two errors on my part:
1. Using high viscosity shock oil. The ATF worked great!
2. I filled the strut full on the extended position and then capped it. The right answer is bleed it, compress it, then cap it.
I think the book says 37-52 psi. That seemed high for the nose strut. That must be a measurement for the mains
thanjs again
Dave
#56
My Feedback: (55)
Join Date: Mar 2005
Location: Mission Viejo, CA
Posts: 171
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SM F4 Balooning on take off
Hi everyone,
Recently fixed up a few issues (landing gear plates, etc) with my SM F4 (Stock SM pipe) with KT 210 which seems to have excellent power and plane flies great. Replaced my old batteries in the nose as well going with Li 3800 v.s two 4800 before. I didn't see any reason to double check the CG after the changes. I have marked the plane at 300-310 previously. Here are the two issues i noticed:
1) Plane starts ballooning after take off without any elevator input if take off role angle is little higher than 25 degrees or so (only if you take off at very low angle (10-15 deg) it won't balloon. i immediately banked to take the high angle or gave it major push elevator to level if off otherwise it would pitch to full vertical. Checked my take off flaps and were around 33mm TE from CL.
2) i am also noticing pitch coupling on full throttle in cruise mode. (which i am thinking of adding some throttle to elevator mix, I can mix any profile with 28X)
As i mentioned at this point I could not be sure if my CG is off and by how much but it flies and lands very easy. no odd behavior other than what was noted.
Any feedback is greatly appreciated.
Jason
Recently fixed up a few issues (landing gear plates, etc) with my SM F4 (Stock SM pipe) with KT 210 which seems to have excellent power and plane flies great. Replaced my old batteries in the nose as well going with Li 3800 v.s two 4800 before. I didn't see any reason to double check the CG after the changes. I have marked the plane at 300-310 previously. Here are the two issues i noticed:
1) Plane starts ballooning after take off without any elevator input if take off role angle is little higher than 25 degrees or so (only if you take off at very low angle (10-15 deg) it won't balloon. i immediately banked to take the high angle or gave it major push elevator to level if off otherwise it would pitch to full vertical. Checked my take off flaps and were around 33mm TE from CL.
2) i am also noticing pitch coupling on full throttle in cruise mode. (which i am thinking of adding some throttle to elevator mix, I can mix any profile with 28X)
As i mentioned at this point I could not be sure if my CG is off and by how much but it flies and lands very easy. no odd behavior other than what was noted.
Any feedback is greatly appreciated.
Jason
#57
My Feedback: (2)
Join Date: Nov 2003
Location: Stittsville,
ON, CANADA
Posts: 86
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The jet will pitch up at low speeds at full throttle settings with the stock SM tailpipe....not sure if this is what you are describing. I actually hold a little down elevator on take-off roll until it reaches take-off speed, otherwise it will take-off by itself. My igyro helps at 40%gain (with 10% hold) in pitch for better behavior on take-off. Also, I dropped the aft end of the pipe lower at the rear mount for even better behavior. My F-4 does not change pitch trim in flight. CG at about 315mm. Make sure as well you have down thrust on your engine...should be approx 5 degrees down. Hope this helps.
Here's a video of mine from Thurderthrust in Sep 17.
Cheers,
Cheers,
Here's a video of mine from Thurderthrust in Sep 17.
Cheers,
Cheers,
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kwik (07-14-2023)
#58
You should flip the stock pipe upside down. I did it and the throtle elevator issue almist went away. Be sureyour turbine is 6—8° with downthrust
cg should be no less than 330mm
regards
Nuno
cg should be no less than 330mm
regards
Nuno