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Old Oct 11, 2012, 11:35 AM
Raised on 80's Pattern
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Originally Posted by doxilia View Post
Matt, you should post more often, your thoughts and contributions would be great! We want to see that Atlanta going together!

David
+1

Yes Matt, your knowlege and insight is a welcome addition here.

Doug
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Old Oct 11, 2012, 04:52 PM
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Thanks for the kind words guys. Funny I've been reading all the great posts from you guys for the past 10 years and never posted. It's not just the cool planes, what I loved about vintage pattern is all the stories and history that came with it, and you guys were always able to piece the stories and history behind the planes together.

There is long line of lineage in the pattern planes and pilots -- from designers to development to building and flying them at WC -- that is wonderful to see and enjoy. And plus they look so cool!!
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Old Oct 14, 2012, 12:27 AM
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Jeff

Great build thread. For what its worth, bending alum tube , rub soap on it , heat with a torch until the soap turns black , let cool, it is annealed and soft, bends much easier now. Next buy a dozen or so pieces of small dia dowels, 1/16" 3/32" or possibly 1/8" x 36". Then slide them in the tube to fill it fairly full make your bends and slide them out. It keeps it from kinking. Next best thing to a mandrel bender I use. The tube will become hard again in a few days all by itself.


Don
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Old Oct 15, 2012, 08:43 AM
That's so classic you.
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Don, thanks for the tip. I have a few extra lengths of tube left that I might practice on. The only trouble I had was with the thin wall tube. It's soft and easy to bend, but it would tear and kink if the radius was too small. The spring bender produced acceptable results with the thicker walled material.

I "thought" I was pretty close to being ready to apply cloth and resin, but after I stared mocking everything up with the new Airtronics servos, it turns out I still have a bit of work to to. (The whole point of mocking it up...)

It turns out my rudder pushrod was all but touching the exhaust stinger. I decided to re-route it with Nyrod.

I also discovered/remembered that the elevators need to be re-made with the same thickness material as the new stab. The originals are just a bit thicker. Enough for me to notice. Making replacements will be easier than trying to sand the originals to the right thickness.

The last bit I still need to fabricate is a tank hatch. The plans just call for a plank of wood to be glued in place, but a hatch would be smarter in case I ever need to see/access the front of the tank.

I ran the engine on the test stand again. This time with the stinger extension to see if there were any adverse effects and I'm happy to report, the engine runs exactly the same, but with a different exhaust note.
Here is a couple short videos of the engine running... The tach numbers on the second video are far from peaked. (she's still new...) No comments about my dodgy test stand.
VIDEO0003 (2 min 12 sec)


VIDEO0006 (1 min 17 sec)
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Old Oct 15, 2012, 12:54 PM
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Use sand in the tube when you bend it. Some have suggested salt as another option.

Bend it around a form, with tension on it.

Andy
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Old Oct 15, 2012, 06:12 PM
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That 25VF sounds fantastic Jeff! I can already see the Skymaster zooming by. Gonna be hard to see! What prop and fuel did you use?
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Old Oct 15, 2012, 06:24 PM
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Originally Posted by frequentflyer1 View Post
Great build thread. For what its worth, bending alum tube , rub soap on it , heat with a torch until the soap turns black , let cool, it is annealed and soft, bends much easier now.
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Don, how would soap "aneal" the aluminum and would it then always stay soft afterwards?
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Old Oct 15, 2012, 07:33 PM
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Hey Matt, the process is called annealing, basically softening a metal so it can be worked with.

By using soap stone marks on the piece of aluminum you get a visual aid as to when it’s annealed.
The marks will turn black from white letting you know it’s ready to be worked with, you can also just coat it with some soot from an acetylene flame and when it’s heated and the soot disappears(burns off) the aluminum will be ready for bending etc.

Name: HPIM3411.jpg
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Description: soap stone and marks made on a piece of aluminum tubing before being an anealed.

After the aluminum tubing is annealed it will start to harden again as long as it’s left to cool down on its own. You can also anneal the tubing more than once, especially if you need to set up for multiple bends in the tubing to make a header.



Quote:
Originally Posted by Huang View Post
how would soap "aneal" the aluminum and would it then always stay soft afterwards?
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Old Oct 15, 2012, 08:43 PM
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Thanks Paul! That makes sense. I have to give it a try!! Matt
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Old Oct 16, 2012, 10:33 PM
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Looks very tight! Is the elevator on a carbon pushrod? How did you do the Y in the back?
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Old Oct 17, 2012, 12:23 PM
That's so classic you.
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Quote:
Originally Posted by Huang View Post
Looks very tight! Is the elevator on a carbon pushrod? How did you do the Y in the back?
Hi Matt.
Yes, the elevator is on a carbon pushrod with 2-56 ends. On the wye end, two rods are bent, then wrapped with copper wire and soldered to a short section. The short section is epoxied in the carbon rod about 1" deep.
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Old Oct 17, 2012, 05:23 PM
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Thanks Jeff. Brilliant simple solution! I've been thinking how to get the Y to the carbon rod without drilling. Is the short section is just another piece of 2-56 wire, glued in with 30 min epoxy / JB weld like how we do with the Central Hobbies carbon/titanium pushrod systems?

What is the size of carbon rod used? It looks perfect for the 25 size planes. I would like to use your setup in 40 size Curare. Would this be too flexy on a larger plane?
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Old Oct 24, 2012, 04:24 PM
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Matt, yes its the same principal as the Central hobbies product. I use the 4mm OD x 2.5mm ID carbon tube. The ID is a little large so it is best to use JB weld versus epoxy. A better product is EpoGrip epoxy. Its very thick and wont run or drip. Be sure to only insert well cleaned threaded rod into the carbon tube as straight wire might pull out. The threads give the epoxy something to grip on to.
As for it being ok for 40 size models, I would say yes. If done rigt, its as strong as the Dave Brown fiberglass pushrods.
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Old Oct 24, 2012, 04:37 PM
That's so classic you.
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The SM is all mocked up so I can check the balance. The battery (4.2oz 2200mAh 4 cell NiMh) will have to be mounted behind the stinger extension. I will have to make an access hatch and fabricate a mount for the battery. The absolutely last thing prior to finishing.
I weighed it, with everything and it came to 3lbs 5.5oz. I'm happy with that.
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