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hard points in a composite wing

Old 11-20-2008, 12:08 AM
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seflyer
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Default hard points in a composite wing

I want to add hard points into my composite reaction wings. what method do you guys recommend? I have thought about adding a dowel vertically in the wing with light ply panel on the upper skin to spread the load around. making the arms and pylons is no problem. just want some opinions on modifying the wing.

thanks Kevin
Old 11-20-2008, 12:30 AM
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Harley Condra
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Default RE: hard points in a composite wing

For a primer on hard points and pylons, see www.bvmjets.com.
The Bandit ARF section shows a drawing for tank and pylon construction and installation.

On the drawing, pay particular attention to the hardwood dowel relationship to the wing spars and ribs.

I think that it is wise to distribute the flight loads from the dowels to the spars. As long as the dowel locations are correct, and the skins are thick enough, there should be no need for an external skin doubler.
Old 11-20-2008, 12:52 AM
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Gordon Mc
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Default RE: hard points in a composite wing

Here's a thread from when I asked for suggestions a while ago: http://www.rcuniverse.com/forum/m_72...tm.htm#7293761

I found that Dan from Details4Scale has some neat 2-piece plastic doohickeys for mounitng pylons etc: http://www.details4scale.com/ - not sure if these parts are shown on his pages, but you can get his contact info there and email / phone him.

I now prefer to use Deltron rather than hardwood for any home-made pylon mounts - taps better, holds the threads better, etc.
Old 11-20-2008, 12:56 AM
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Harley Condra
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Default RE: hard points in a composite wing

Gordon,
The only "Deltron" that I am aware of is made by PPG. Deltron acrylic urethane enamel.
Do you mean "Delrin"?
Old 11-20-2008, 02:03 AM
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Default RE: hard points in a composite wing

A trick I learned was drill a hole in the wood, then CA some of that yellow nyrod into the hole, now use a wood screw into the yellow nyrod. Sounds very similar to the use of delrin. In concept anyway.
Old 11-20-2008, 09:10 AM
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Gordon Mc
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Default RE: hard points in a composite wing


ORIGINAL: Harley Condra

Gordon,
The only "Deltron" that I am aware of is made by PPG. Deltron acrylic urethane enamel.
Do you mean "Delrin"?
You may well be right Harley - I never did see the name written anywhere, I just got told what it was when I bought it from Tap Plastics.
Old 11-20-2008, 09:33 AM
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seflyer
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Default RE: hard points in a composite wing

I will try and get a good idea of where the spars are located in the wing and see what can be done.

thanks for the tips and ideas. Kevin
Old 11-21-2008, 07:19 PM
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Default RE: hard points in a composite wing

Maybe it is Delrin or Delron, I forget the correct spelling. It is extremely good plastic, used a lot for heli gears and other model parts.
Old 11-21-2008, 07:31 PM
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Default RE: hard points in a composite wing

Definitely call Delrin...nice material to work with. Not sure how well epoxy sticks to it though.

Craig.
Old 11-21-2008, 08:11 PM
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ianober
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Default RE: hard points in a composite wing

I just drill a hole in the the bottom of the wing, insert the same sized dowel, usually at least 3/8 if not more, and glue it in with Gorilla glue. Then when the glue dries I trim the dowel flush with the surface, drill a hole for a bolt and then tap the hole with 4-40 and soak the threads in thin CA. Works good, I used this method the 339 ordinance, very solid.

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