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Old Feb 12, 2013, 08:38 AM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
8,666 Posts
I'm thinking drilling a couple of holes, one in front and one in back and wrapping some CF strands right through them and around the boom.
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Old Feb 12, 2013, 08:41 AM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
USA, OH, Worthington
Joined May 2002
6,774 Posts
Carbon is fairly brittle and not good for wrapping applications, especially if it goes over a square corner or edge. Use Kevlar instead.

On the supergee wing mounts, the carbon tow was wrapped around the boom and around the carbon posts, then CA'd. The carbon-carbon bond with CA is amazingly strong, and probably doesn't need to be drilled thru.
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Old Feb 12, 2013, 08:44 AM
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United States, NC, Raleigh
Joined Sep 2010
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it's carbon and foam on the pylon... more surface contact would be better than drilling holes. Just uni, flat to the surface of the pylon and boom would be my bet. Not sure why it broke off to begin with... I'd like to see some pictures to better understand what caused the failure.

E
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Old Feb 12, 2013, 09:04 AM
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Joined Dec 2007
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I glued with epoxy, on sanded surfaces. It's enough for my stream. I fly about 6 months with it
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Old Feb 12, 2013, 09:26 AM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
USA, OH, Worthington
Joined May 2002
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Since the fuselage is painted, make sure you sand all the paint away. Perhaps the bond that failed was the paint - epoxy bond from the original molding? Just throwing things out there.
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Old Feb 12, 2013, 09:42 AM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
8,666 Posts
Quote:
Originally Posted by NCDLG View Post
it's carbon and foam on the pylon... more surface contact would be better than drilling holes. Just uni, flat to the surface of the pylon and boom would be my bet. Not sure why it broke off to begin with... I'd like to see some pictures to better understand what caused the failure.

E
I see, maybe a thin wrap around the boom and then up the sides of the pylon. The one I saw that was wrapped with thread had a flange on the front and rear and the thread wrapped over those.

I'm with Tom though, what caused it to let go to begin with. Maybe some mold release? I always sand the sections I intend to glue together and then I clean them with denatured alcohol.
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Old Feb 12, 2013, 09:43 AM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
USA, OH, Worthington
Joined May 2002
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Mike,

Stick with sanding. The denatured alcohol will NOT remove two of the three mold release products I use when molding. I'd imagine most other manufacturers are using similar stuff.
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Old Feb 12, 2013, 10:10 AM
Aeromodeller by heart!
RubSon's Avatar
Herning, Denmark
Joined Dec 2002
634 Posts
Hi.

Thanks for all the imput! Itīs one of the great things about RC-groups. So much help just around the corner!

And then to clear things a little!

The fuse is only painted in the front, but some releaseagent could have been left over on the boom.
It was sanded though and the pylon was made to fit it as good as I could. (see pictures in one of the first posts)
Gluing was done with 5min epoxy, and that could be the problem.
Pylon is made from Rohacell and Carbon, so it will withstand the use of CA but I needed the time to get every thing in prober allignment.

Reattachment has been done with 30min epoxy and all thatīs left is to make a tiny path of FG and wrap it around the boom and secure it to the pylon. I plan to do this with CA. It will not look pretty, but it will not break either. Small price to pay on such a beautyfull plane.

Ruben
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Old Feb 12, 2013, 10:17 AM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
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Quote:
Originally Posted by tom43004 View Post
Mike,

Stick with sanding. The denatured alcohol will NOT remove two of the three mold release products I use when molding. I'd imagine most other manufacturers are using similar stuff.
What about acetone? I keep a gallon of that stuff around as a solvent too or will that soften the part too much? Basically, I'm always sanding and I figure a damp rad with some solvent on it will remove, 1) the sanding particles and 2) the oils left behind by my handling the part.... lastly, I had hoped it would remove any residual mold release. It's amazing how much stronger the bond gets with just an extra minute or two of prep.
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Old Feb 12, 2013, 10:27 AM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
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oops... Double Post
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Old Feb 12, 2013, 10:34 AM
Aurora Builder
United States, MD, Lusby
Joined Nov 2003
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Ruben sorry for your failure, that is never fun I lost an elevator linkage about 300' up one time, major damage . I think in your case the 5 minute epoxy was to blame, I don't trust that for critical structural joints. 30 minutes is much better.

Tom I'm curious what won't come off with acetone? At least on the PVA/wax system I'm using it works. Perhaps you've switched back to Freekote?
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Old Feb 12, 2013, 11:07 AM
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I glued with 24 hour epoxy. In this place use the best you can
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Old Feb 12, 2013, 11:20 AM
Father of Fr3aK, DLG Pilot
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USA, OH, Worthington
Joined May 2002
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Most fuselages are made with a semi-permanent release like Frekote or McLube 971 etc. The guys in Europe seem to have a better selection than we have here in the US. Anyhow, these release agents use Ketone or Heptane as a carrier because the active agents aren't soluble in water / alcohol / acteone. Mechanical removal is really the only viable option.

Water or alcohol will remove PVA, depending on the formulation.

As far as ensuring the pylon stays attached, it doesn't take alot of material. I lightly dust a piece of waxed paper with 3M77, then apply it on top of a piece of scrap light glass (1.2-1.6 works great) and roll it flat. Now cut thin strips of this about 8-10mm wide with the fibers at 45/45. Cut a piece just shorter in length than the pylon and lightly 3m77 the glass cloth side. Press it in place across the seam with the fuse so half of the glass is stuck to the pylon and the other half is stuck to the boom. Gently peel off the waxed paper and hit it with a drop of CA or your favorite epoxy system. Blot of excess epoxy or press the CA into the weave with a poly bag over your finger. It will NEVER come off.
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Old Feb 12, 2013, 11:30 AM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
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Tom,

I'm glad you explained how you do that with the light glass and 77. My Blaster came with something done like that to hold the vertical fin tight to the boom and I've never been able to reproduce such a nice finish as that was. NOW, I think I know how it was done.

All these little tidbits make this forum such a treasure trove of information.
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Old Feb 12, 2013, 01:19 PM
I added lift to my stable!
tbird911's Avatar
Knoxville, TN
Joined Feb 2007
647 Posts
....fiber glass cloth . . .

I have always:
  • Sanded the two surfaces that meet
  • cleaned with acetone or similar
  • used suggested adhesive (CA for carbon to carbon)
  • used thin CA or finishing epoxy to run a 1/2" wide strip down one side of the stab mount, around the bottom of the boom and then up the other side

Have yet to see on come loose when done that way . . . 2 cents added
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