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Author Topic: Combat model foam bits repair  (Read 1200 times)

Offline GERALD WIMMER

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Combat model foam bits repair
« on: May 08, 2019, 05:54:33 AM »
Hello I saw an article on repairing dinged wingtips on another NZ forum and decided I should share this repair technique I developed to repair the foam in the leading edges easily. My diesel models (built by Bryce Gibson in the 1990's) had the foam eaten up by fuel over many flights leaving the spars and LE strips floating about in LE bags.
By poking a small hole large enough to insert the expanding foam straw into the LE covering and pumping just a small amount of foam in it quickly restored the foam LE shape with a now fuel proof polyurethane foam. The trick is not to inject too much as it quickly expands to fill the whole LE then continues out any gaps . Caution here as I locked the bellcrank this way on one model and had to open it up and remove the excess foam . A bit of tape over the holes and your done. Expanding foam can be real messy but if contained by covering or tape can be used to selectively replace lost foam easily.

I'm sure it could be a great way to make new leading edges if you made a mold lined it with paper and placed the spars and LE in , then shot in foam, worth a try?
Regards Gerald
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Offline Bob Mears

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Re: Combat model foam bits repair
« Reply #1 on: May 08, 2019, 07:06:18 AM »
A little more controllable is the expanding Gorilla glue. Put a small amount in there, spray it with water, put your tape over it and iron the tape. a little extra ironing leaving heat on the area will really make that stuff go off.
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Offline GERALD WIMMER

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Re: Combat model foam bits repair
« Reply #2 on: May 09, 2019, 04:58:26 AM »
Hello
Thanks Bob. I have used Gorilla Glue and a spray mist on many model repairs but will get the iron out next time and will try that out too.

Regards Gerald
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Offline phil c

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Re: Combat model foam bits repair
« Reply #3 on: June 18, 2019, 11:22:47 AM »
Both the foaming insulation foam and making Gorilla glue foam work, but are a lot heavier than 1lb styrofoam.

I repaired a speed limit plane last week using G Glue.  All the seams around the center boom/motor block and the foam plastic had split.  It came out plenty strong, but just the glue added an ounce and a half, as did some carbon fiber/epoxy to reinforce the boom/trailing edge joint.

It's not easier, but cutting a few foam blanks will let you get the plane nearly back to its brand new weight.  Short chunks can be spliced in for bad dings.
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phil Cartier

Offline GERALD WIMMER

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Re: Combat model foam bits repair
« Reply #4 on: June 20, 2019, 05:38:25 AM »
Hello
Yes glue epoxy or Gorilla are heavier then the materials they replace and the more they get dinged the weight climbs till a major rebuild/recover or replacement is necessary.
The other good one for a quick weight gain is a leaking fuel tank and a pressurized tank on a balsa model is good recipe for this. It happened it on the weekend to a fabric covered vintage model and the fuel sprayed right to the outboard wing tip and it also dissolved my water based contact glue into a slimy mess!
Regards Gerald
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