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Wing Mold

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Old 07-20-2004, 04:50 PM
  #26  
daven
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Default RE: Wing Mold

This mold will be all glass. They will be made shortly by Wayne Seiwert, owner of Aerotech Models. I was at his shop yesterday, and his molds for his warbirds looked fantasic with all the details built right in. A friend of mine works for Wayne, and I got to watch him lay up a P-47 tail which was pretty interesting. I was amazed at the amount of Carbon that goes into that tail.

http://www.aerotechmodels.com/
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Old 07-20-2004, 05:17 PM
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Default RE: Wing Mold

I haven't used MDF for anything but the flange splitter plates, but my answer to you would be "lots of lacquer sanding sealer, sanding between coats." That's what I use on my splitter plates and I've never had a problem.

-David
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Old 07-30-2004, 03:19 PM
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Default RE: Wing Mold

Just curious, has anyone tried substituing Depron for Rohacel?
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Old 07-30-2004, 10:56 PM
  #29  
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Default RE: Wing Mold

The molds were finished today.

I'm just waiting on a few more supplies and I should be ready to dive in. I can't wait.
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Old 07-31-2004, 02:21 AM
  #30  
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Default RE: Wing Mold

As I understand it, depron is rather soft or spongy/rubbery. Rohacell is a rigid foam.
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Old 07-31-2004, 11:40 PM
  #31  
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Default RE: Wing Mold

I posted a note over in the pylon forum too, but you can also try Spyder Foam as a replacement for rohacell. I've used it on many occasions where it provided a better bonding surface to kevlar. Even though it has a vertical grain structure that you can use to your advantage, it still will dent like rohacell and easier. It is cheaper, but you have to hot wire it into thin sheets.

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Old 08-01-2004, 08:02 AM
  #32  
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Default RE: Wing Mold

Michael,

Do you think you can hot wire it as thin as 2mm ?
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Old 08-01-2004, 09:18 AM
  #33  
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Default RE: Wing Mold

It can be done... I was using a cnc cutter to do so, but first tried hot wiring it from wood templates and shifting the foam up by 2mm on each cut. Obviously, the cnc cutter fared better.

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Old 11-06-2004, 12:28 PM
  #34  
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Default RE: Wing Mold

Lots of hard work, and trial and error, but I finally have a wing ready to test today.

The first wing I pulled 2 months ago was not flyable, but made a great tool for me as I cut it apart and looked inside as to what I did. I screwed up the hinge on the first one, but that helped me with this one.

Although not perfect, this wing turned out pretty darn good (better than I expected so quick). I new it was going to be heavy, and it is at 20 oz ready to go (with servo). I know I can easily cut 2 oz, and probably 3 in resin alone.

Heres a couple pictures, I'll let you know if it survives the 160 mph "nelson" test this afternoon.

Thanks to everyone for your help, it really was a good learning experience that I can see will take years of practice to perfect.
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Old 11-08-2004, 11:57 PM
  #35  
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Default RE: Wing Mold

Congratulations.

Let us know what your results are. (And on this forum, I think it's safe to say that we'd all enjoy seeing some photos of what you did, and/or what you'll do on the next set.)

Good luck with the test flights!
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Old 11-09-2004, 03:32 PM
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Default RE: Wing Mold

Test flights were this past Saturday, and they went very good. I originally flew it with an O.S. .46 AX and it handled 125 mph with ease. After two trim flights, I removed the O.S. and put a Nelson .40 Q500 motor on. I flew it twice with the Nelson, approaching speeds of 170 mph. I had plenty of elevator throw and really snapped some turns and the wing held up great.

Everything is still solid, so I think I have a winner. Now I just gotta cut 3 oz minimum. I think I can easily get 1-2 out of the next wing, and finding that last oz may take some time.

I found that laying up glass on Rohacell is a pain in the rear. A friend suggest laying the glass up on wax paper, and then flipping it onto the rohacell. I think I will give this a try, if it works, it will save me quite a bit of resin right there.
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Old 11-09-2004, 05:38 PM
  #37  
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Default RE: Wing Mold

how do you join moulded wings, just like a fuse
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Old 11-10-2004, 09:16 AM
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Default RE: Wing Mold

Not like a fuse. I lay up each wing half in a female mold and let dry in a vacumm bag. After each half is dry, I fit all the internals (spar, torque rods, blocks for wing hold downs, etc).

I then lay a bead of Pro Set Epoxy mixed with Colladial silica around the perimeter of the mold halves. After this, I flip one mold half on top of the other, clamp and let dry. The glue forms the seam, there is no flap of fiberglass or anthing to join them.
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Old 11-10-2004, 06:21 PM
  #39  
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Default RE: Wing Mold

cheers Daven, is rhonacell bendable.
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Old 11-11-2004, 10:28 AM
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Default RE: Wing Mold

It will take gentle bending, but probably not anything complex. I've been told that if you add heat with a gun it does soften it up a bit for more than gentle bending, but I have not tried that.
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Old 02-04-2005, 08:05 PM
  #41  
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Default RE: Wing Mold

Do you leave the wing halves in the molds when you join them? Wouldn't the expoxy stick to the mold, making it impossible to get the wing out?
BTW, looks great, hope to hear more about it, this thread has cleared up alot of issues for me.
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Old 02-05-2005, 08:01 AM
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Default RE: Wing Mold

The molds are heavily waxed, so the epoxy does not stick to the molds. For the first 4 wings I used a product called PVA on top of the wax which aids in release. Every time you use a mold it needs to be waxes a few times, but after a while the mold will kinda get "seasoned" and you will only need to wax one time between parts. I have been using Dolphin Wax from H&M Racing, but have used PartAll with good success also, its just a little tougher to apply, but it is a good wax.
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Old 02-07-2005, 03:17 PM
  #43  
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Default RE: Wing Mold

ORIGINAL: daven

Lots of hard work, and trial and error, but I finally have a wing ready to test today.
Looks good. Im interested in how you did the bonding at the leading edge in particular. Does glass/balsa/glass core get trimmed flush with the mold flange? Or do you chamfer it back a bit & fill it with a bead of thickened epoxy & stand the mold on edge? Everyone has a different pet technique & Im interested in how & why.
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Old 02-08-2005, 09:45 AM
  #44  
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Default RE: Wing Mold

dave,

Check out www.r-g.de in the shop.
Under sandwich materials.. look for plates of airex.. or sometimes called herex. A friend of mine uses it in wingconstruction for F5D models.
It's in various thicknesses.. 1.2mm is the thinnest and should be fine for your wing


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Old 02-13-2005, 11:16 AM
  #45  
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Default RE: Wing Mold

ptxman,

The LE is where I have the most problems. I've built 4 wings now, the first was basically a test wing that I cut apart. The 2nd is still flying well, the 3rd has not flown yet, and the 4th seperated at the LE and basically blew up in the air.

The Rohacell is trimmed slightly undersized in the mold when I bag each half. The gap is filled with epoxy mixed with colladial silica. After I pull them out of the mold, I buzz the overhanging fiberglass and sand it down to the LE.

Since I have been having some trouble with the LE seperating, I am going to try something a little different on my next wing. I'm going to put an 1/8" thick balsa spar about 1/8"-3/16" back from the LE. I'll CA it on the bottom to make sure it stays in place when I join the halves. When I join the halves, I'll add a little extra glue in the LE to form a nice I beam up front. This will also help limit the amount of epoxy that normally spooges into the mold. When using Coladial Silica you don't have to stand the mold on edge, it doesn't move or settle like you would think.

Thanks for the link Peter, I'm just about out of rohacell, and this stuff is expensive. I may just go to balsa, or try the stuff you mentioned.
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Old 02-13-2005, 11:17 AM
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Default RE: Wing Mold

Peter, I'm going to need a little more help with that site.

I can't read that language, and am struggling finding "Sandwich Materials".
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Old 02-13-2005, 01:28 PM
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Default RE: Wing Mold

ORIGINAL: daven
I can't read that language, and am struggling finding "Sandwich Materials".
Click on the English flag and it will take you to the English language version. Or, in German it's "Bestellen," then "Sandwich-Werkstoffe," followed by "PVC-Hartschaum." In English, they have it under "Rigid PVC foam boards."


-David
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Old 02-14-2005, 02:56 AM
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Default RE: Wing Mold

ORIGINAL: davidfee
Click on the English flag and it will take you to the English language version. Or, in German it's "Bestellen," then "Sandwich-Werkstoffe," followed by "PVC-Hartschaum." In English, they have it under "Rigid PVC foam boards."

-David
Have you tried this stuff yourself David? If so, what is your impression over balsa & rohacell?
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Old 02-14-2005, 06:32 AM
  #49  
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Default RE: Wing Mold

Peter I have used it for tests and have had excellent results....I am told that C-ARF uses it on all their airplanes...the material for use is the 1.2 and 2mm types...I could email you the details of the German Retailer who caters to modellers and shall be happy to send you samples..send me an email and I can send you the exact details of the material with prices..

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Old 02-14-2005, 12:09 PM
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Hi Peter,
No, I haven't used the PVC stuff myself, other than repairing a molded wign which was made with it. It seems to be much like Rohacell in its properties (other than color). I can't remember exactly, but I think the bubbles in it were about the same size as in Rohacell. Airex is so much less expensive than Rohacell that it's really tempting. I think a lot of the ARF producers are going with Herex/Airex these days because getting a solid supply of consistently good balsa at reasonable prices isn't easy. With the manufactured foams you don't have to worry about changes in density, grain structure... etc.

-David
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