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Old 06-01-2011, 05:39 AM   #1
Tom Sawyer
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Default Repairing dents and chips in foam?

Does anyone know if it is possible to effectively repair dents and chips in foam?

I dug out an 'old' airframe of mine just recently and noticed alot of pressure marks near the leading edge of the root of the main wings where it had been lifted and as its a semi scale warbird it would be nice to see if I could get any of these these out or improve them in any way.
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Old 06-01-2011, 05:47 AM   #2
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Boiling water poured on to the dent helps with some types of foam. Others need a surface skim of Balsalight or Spackle.

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Old 06-01-2011, 06:40 AM   #3
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What works great too, is to mix some lite weight spackle with some 5 min epoxy, 1/2 epoxy to 1/2 lite weight spackle, then take some wax paper and cover the area to smooth out the epoxy filler, take off the wax paper after about 15 mins, hope that helps, Chellie

Note : practice on a piece of scrap foam

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Old 06-02-2011, 05:28 AM   #4
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Thanks for that I will give it a go.
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Old 06-15-2011, 01:48 AM   #5
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Another good tip i found off youtube of all places was run some warm(NOT BOILING HOT) water over any areas and most foam compounds should either come back out 90%-99.9%.
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Old 01-03-2014, 07:05 AM   #6
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Post creased and bent wings

old thread but I need advice and I always know I can find it here. I received a wattage tangent today and the wings have two different types of foam. a thick foam core and a thinner foam over it not sure what type either of them are. I have seen the videos and advice on the hot water methods. Does the hot water effect all foam the same or just certain kinds? I am going to try it but before I do I want to make sure they can be repaired with the wing tip kinda rolled up here are some pics

http://s801.photobucket.com/user/duk...les/slideshow/
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Old 01-03-2014, 08:16 AM   #7
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Originally Posted by Dukepiles View Post
old thread but I need advice and I always know I can find it here. I received a wattage tangent today and the wings have two different types of foam. a thick foam core and a thinner foam over it not sure what type either of them are. I have seen the videos and advice on the hot water methods. Does the hot water effect all foam the same or just certain kinds? I am going to try it but before I do I want to make sure they can be repaired with the wing tip kinda rolled up here are some pics

http://s801.photobucket.com/user/duk...les/slideshow/
You have one problem with hot water here .... the last photos show the type of foam that has a shiny 'skin'. I have a couple of models with this, I'm not sure how it's done but when you apply heat - the 'skin' reacts different to the foam underneath. The underlying foam expands as you want - but the 'skin' loses it's shine and on one of mine actually split and contracted.

Water is no problem for any foam used in model construction. It's when you get 'skin' like this you have to alter method.

Maybe another can detail how they worked with this 'skinned' foam ?

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Old 01-03-2014, 09:33 AM   #8
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with the skined foam, your Danged if you do and your Danged if you dont try to repair it , a couple of things you can do, poke some holes in the foam with a pin, that will help to relax the skin and use some hot water or steam, also on the wing tip, use a cloth soaked in some water and use a Iron to press out and straighten the foam with, on the wrinkles on the wing poke some holes in the foam around the wrinkle and use the wet rag and iron to help pull the foam flush, on minor dents, you can use some lite weight spackle and a few drops of canopy glue to fill them in with, on the wing tip that is rolled, use some flat weights to hold it in place until it cools down, you will just have to try a few different things to see what works best for you, hope that helps, Chellie

here is some more tips from Ed Anderson

HOW TO FIX WARPS, DENTS, TWISTS OR UNCRUNCH FOAM PLANES and PARTS
HOW TO FIX WARPS, DENTS, TWISTS OR UNCRUNCH FOAM PARTS
by Ed Anderson

I never crash, but maybe you do. Crashing can crunch the foam of a Radian or other foam planes to the point that the parts donít fit or it introduces a twist or warp as you try to put it back together. Or it can introduce a twist or warp in the fuselage. I am going to outline a method of getting the foam back to straight or uncrunching parts. This can also be used to take twists or warps out of new parts and it will take dents out of your foam wings or even bagged wings, like DLG wings.

Letís suppose your Radian, Easy Glider, Easy Star, etc. has a tendency to turn in the air requiring you to trim in a lot of rudder to get it to fly straight. How can you fix it? Well first you have to find the cause. Turn your foamy over and site down the fuselage seam. It should be straight from nose to tail. Or, tape a piece of string to the tail end of the fuse, again inverted and then gently stretch the string to the nose. It should track down the center of the fuse. If it does not, you have a warp. We are going to fix it.

This can happen at the factory, from a fuse not sitting right in the box or from a crash where one side of the fuselage compressed from an impact. This can also happen if you leave a foam plane in a hot car for a long time. Believe me, what you will learn here will come in handy for the rest of your foam flying life.

Heat does wonderful things to foam. It can stretch it, expand it and help straighten it. You can put twists in or take them out. You can use this when making some foam replacement parts too.

Since we are fixing the fuse, take the wings off, you won't need them. Take the h-stab off if it comes off. Tape the rudder so it is straight.

Try to figure out where the warp is centered. I am going to guess it will start behind the wings, somewhere along the boom. Flex the fuse to see if you can get it to look straight. You may have to use something to apply pressure in the center of the curve on the opposite side to get it straight. If you can flex it to straight, you can fix it.

Basically you are going to apply heat to the inside of the curve as you flex the boom away from the curve and a bit past straight. As you apply heat the gas that is trapped in the foam beads will expand. As the beads expand they extend that side of the fuselage making the heated side longer and helping you take that warp out. If this was caused by a crash this will uncrunch the crunched beads.

This goes under various names, but you might hear it called the Elapor soup method as it really became popular with the Mulitplex Elapor foam planes. But it works well with most beaded type foams. Easy Star pilots would crunch the nose of the plane in a crash. They would plunge the nose, Elapor foam, it into boiling water and the foam would expand, thus the soup reference.

Heat Methods.

HOT running tap water - You hold the part to be expanded under the hot water while you shape it. In this case you flex the fuse just a little past straight while it is under the running hot water. The foam beads will expand, extending that side of the fuse. After a minute or two you take the fuse out from under the water, still holding it and let it cool. Then site and see if it took. Go back under the water if needed. As tap water is only 100 to 140 degrees sometimes this is not hot enough to do the job. So we need more heat.

Placing the part into boiling water - this works well for small pieces like a rudder a wing tip or a crunched nose. You can also pour boiling water over the area.

Steam from boiling water sometimes works. Use a BIG pot and make lots of steam. This works well for large areas like wings.

My favorite is using a heat gun/hair dryer to heat a wet cloth or paper towels. Don't let the towels dry out completely. You heat the wet cloth till it steams and starts to dry out. You have the part stretched while you do it, just as above.

BTW this works well for bagged composite wings, like DLG wings. It can take a dent our by heating the foam under the skin. I use paper towels and my covering iron. They just magically disappear. Works well for dents in your Raidan, Easy Glider, etc. here you want to be more focused, so a covering iron or a hot clothes iron is best. Just use the tip to focus the heated area over the dent.

In each case the purpose of the water is to keep the foam from getting too hot and melting. We want to get it up to about the temperature of boiling water, though sometimes hot tap water, 120 to 140 degrees can do it too.

Using these methods I have taken Radians and Easy Gliders that have been broken into numerous smashed and crushed pieces, reshaped the foam and glued it back together with great success. Recently I shredded my Radian while slope soaring. A high speed crash through bare tree branches did a nice job on the fuse. The wings just came and got a few dents, but the fuse was in 5 pieces. It flies today!

Regardless of the method, you want to spread the expand over a somewhat broad area, not a pinpoint. Again, in the case of dents in a wing you want to be more targeted. That is why I use my covering iron rather than a heat gun.

In the case of the fuse we are using as our example, you want to expand the most in the center of the warp curve but you want to extend that somewhat forward and back of the center or you will have to overheat one area too much and perhaps not have enough expansion ability to make it work.

Try it! If you have some scrap Styrofoam or other beaded foam you can try this out for practice. Take a foam drinking cup. cut out the bottom. Now do a top to bottom slice. Use the method above and see if you can take the curve out of the foam and make it flat. You may not get it totally flat but you will see the impact. Note that the cup material is thin so donít heat it to much at once or you will expand all the bead instead of just the ones on the inside of the curve. The heated beads will get bigger.

When working on a fuse, wings or other parts, be sure you don't introduce a twist as you do this or you will have another problem. But no worry, that can be fixed too.

Clear Skies and Safe Flying.

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Old 01-03-2014, 09:36 AM   #9
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Posts: 716 Quote Reply Posted: 04/Sep/2010 at 8:56am Also, I've had success using the "steaming" technique:

soak a paper towel...then lay it on a kitchen towel, fold over the towel and pat it slightly (you want the towel still quite wet, almost dripping)...



lay the towel flat on the foam material, then take a sealing iron (no sock), set on medium low...run the iron over the wet towel...(you should hear a sssss sound as the water vaporizes). You can lay something heavy (such as a field battery) on the surface while it cools.


This technique works best to take out dings and creases, but also works to unwarp surfaces.
Works best on Depron, adequate on EPO, not so much on EPP.




Hope that helps. ~Bud

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Old 01-03-2014, 12:14 PM   #10
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Most of us have a Workmate ... those folding work tables that you can wind in / out one half the top as a vice / clamp.

They are amazing tools for straightening bent fuselages / wings etc.

Set fuselage into the gap ... wind the gap closed and measure the bend. Unwind the moving part and cut foam blocks that you can insert in between fuselage and jaws .. wind closed and using the blocks you can force the fuselage past straight - to slightly the other bend. Apply hot-air by wafting a hot-air gun over the fuselage in sweeps - not too long on one area. Warm the fuselage so it accepts the bend being put in by the Workmate. Let it cool.
Take Fuselage out and test for straightness ... the slight over bend you applied should have come out and fuselage be as near straight as you'll get. If not repeat ...

Bent ailerons, elevators etc. can all be cured this way as well. But remember that once bent - they all are easier to bend again later. So twists and deformities do later return by themselves.

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