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Old Feb 10, 2013, 06:26 PM
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More progress!
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Old Feb 10, 2013, 06:34 PM
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Looks like a cool build, Ive always liked the F35. It was hard to tell in the pics, are you going to have a thrust tube off the back of the fan?
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Old Feb 10, 2013, 07:43 PM
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Thanks Lt599! Yes, I just haven't had a chance to order materials to build it yet.

I'm a little concerned about weight, it looks like AUW will be around 1100-1200 grams...with a max 1700 grams of thrust. Does this seem like a reasonable T/W ratio?

I'm looking at 880W constant, 1000W max. Worst case (1.2 kg, 880W), I would be at 332 w/lb.

I haven't calculated what the L/D will be...I don't know what kind of airfoil I'm going to use. I scrapped my previous airfoil (GOE 188) because it was way too thick. I might end up with an airfoil around 4% thickness.

Please give me any advice! This is my first larger scaled build
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Old Feb 11, 2013, 01:21 AM
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More progress, wings are done!
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Old Feb 11, 2013, 01:48 AM
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It's really starting to take shape. Nice job!
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Old Feb 11, 2013, 07:52 PM
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Thanks Cooler,

So I did a quick run-up today to make sure all the electronics work and I tested out the thrust a bit. Definitely an immense amount of thrust!

However, I can feel the ducted area leading into the EDF flexing inward from the suction a little bit. I'm going to glass the entire outside of the aircraft...but how concerned should I be? And what should I do if anyone suspects that glassing won't do the trick. Cheater hole? I'd rather not...but I will if needed.

Thanks all!
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Old Feb 11, 2013, 08:23 PM
Do it Right, the first time!
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Quote:
Originally Posted by DoubleOne View Post
However, I can feel the ducted area leading into the EDF flexing inward from the suction a little bit. I'm going to glass the entire outside of the aircraft...but how concerned should I be? And what should I do if anyone suspects that glassing won't do the trick. Cheater hole? I'd rather not...but I will if needed.
I had to go back and see what you had done on ducting. Posts 12/13 show your set-up. You mention "I like awrightbrother's method,"
http://www.rcgroups.com/forums/showt...672388&page=45
You must remember that the duct work for the T-38 is all custom made fiberglass. A whole bunch stronger that the foam you have. I don't think glassing the ouside will do much, you would need to glass the inside of the ducting to do any good. That's where all the suction is. Just my 2cents.

If the top of fuse is not glued on yet, you can still go back and do it!
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Old Feb 11, 2013, 09:16 PM
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It was glued, but I surgically removed it I don't have time to fiberglass tonight, but I've fit the cloth inside the duct. I'm using .75 oz cloth with polycrylic miniwax, I hope these materials are good enough.
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Old Feb 11, 2013, 09:29 PM
Do it Right, the first time!
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Don't know that the polycrylic miniwax will cut it? Maybe? With the 3/4 oz cloth it's on the skimpy side, I should think. But if that's all you have, it will just have to be good enough. Of course I like to go on the "beefy" side of things, where strength comes in.

A little heavier glass and epoxy are what you should use.
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Old Feb 11, 2013, 10:19 PM
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Im no glass expert by any means but I think 3/4oz cloth would be just fine with epoxy instead of poly. Or maybe glass both sides of the foam, inside and outside of the ducts area, that would not add much weight. Its looking good and I think you should have plenty of thrust if you are careful on finish.
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Old Feb 11, 2013, 10:48 PM
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Thanks guys! I couldn't resist, I attempted to glass inside the duct. I plan on glassing the outside too, but I want to see how strong it comes out first.
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Old Feb 12, 2013, 11:39 PM
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I've reconstructed the nose, strengthened and rearranged the duct, built a exhaust tube, and made a spot for my electronics that is accessible from the top fuse.

I also managed to make the maiden flight on my 18", 50mm EDF F-35C and it was a rocket! Thrust/Weight ratio was 1.5, which is my goal for this F-35 as well. All I can say is, if this 68mm bird flies anything like its smaller brother, I'll be ecstatic!
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Old Feb 12, 2013, 11:47 PM
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The "little" guy! 386 grams thrust, 266 grams AUW
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Old Feb 13, 2013, 08:12 PM
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Top fuse attached, vert stabs temporarily installed. Filled in some of the grooves, should be ready for sanding soon!
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Old Feb 13, 2013, 08:20 PM
Do it Right, the first time!
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So how did the glassing go? Did the ducts strengthen up like you wanted?
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