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Old 03-01-2012, 02:35 PM   #1
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Default How to fix warps, dents, twists or uncrunch foam 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, Easy Star, Super Cub or other foam planes to the point that the parts don’t 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 or a bagged wing Supra competition glider.


Let’s 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 too, 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 don’t 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 03-01-2012, 03:18 PM   #2
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Nice write up Ed! I too have used boiling water to remove some small dents and warps from foam.

Just a word of caution when using boiling water (and I'm sure you know this already, but adding it to the tutorial). Don't leave the part in too long, just dip it for a few seconds at a time until the dent/warp is fixed. Otherwise you'll get the dreaded "aligator skin" look, like it had been left out in the sun too long.

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Old 03-01-2012, 11:33 PM   #3
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Default up to a point....

Good advice once again Ed. Both my radian and Easy star were basically destroyed in a couple of crashes, plus a starmax and an alpha plane that literally exploded on contact. Pretty much gone off all other foam except EPP, but I did find that using packing tape, both clear and coloured, and judicial use of CF tube and ribbon improved things dramatically. Keeping things as light as possible reduces kinetic energy on impact, and bubble wrap around lipos and rx's acts like airbags. My flying conditions are hostile at best,( the wind comes straight from Antarctica) so crashing is a fact of life. I know I come across pretty critical of z foam, elapor, eps and similar foams, but I only comment on my actual experiences with these foams, not from what someone else has experienced. Then again, I could be completely deluded, and live in a place where the ground is harder, and the trees more ferocious than any where else on the planet....and I just started on another balsa kit, happy flying
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Old 03-02-2012, 03:00 AM   #4
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Originally Posted by pattern14 View Post
Good advice once again Ed. Both my radian and Easy star were basically destroyed in a couple of crashes, plus a starmax and an alpha plane that literally exploded on contact. Pretty much gone off all other foam except EPP, but I did find that using packing tape, both clear and coloured, and judicial use of CF tube and ribbon improved things dramatically. Keeping things as light as possible reduces kinetic energy on impact, and bubble wrap around lipos and rx's acts like airbags. My flying conditions are hostile at best,( the wind comes straight from Antarctica) so crashing is a fact of life. I know I come across pretty critical of z foam, elapor, eps and similar foams, but I only comment on my actual experiences with these foams, not from what someone else has experienced. Then again, I could be completely deluded, and live in a place where the ground is harder, and the trees more ferocious than any where else on the planet....and I just started on another balsa kit, happy flying
Do you feel wood or fiberglass would have survived better? Or that they would have been quicker and easier to repair?

In any case, the discussion is not about how indestructible foam is but how to get it back to shape so you can fix it when you dent, twist or break it.

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Old 03-02-2012, 04:46 AM   #5
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Very nice write up!

Something to add to Pat's "alligator skin" condition from too much heat.

When you are sanding your repaired areas, don't sand too long in one spot. The heat from sanding will cause the foam to expand into the dreaded skin condition.

And you'll be like a dog chasing his tail trying to get it smoothed out.

When I die, I want to go like my Grandfather did, in his sleep...... Not screaming like the passengers in his plane.
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Old 03-11-2012, 05:45 PM   #6
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Originally Posted by AEAJR View Post
Do you feel wood or fiberglass would have survived better? Or that they would have been quicker and easier to repair?

In any case, the discussion is not about how indestructible foam is but how to get it back to shape so you can fix it when you dent, twist or break it.
Unlikely that wood or fibreglass would outdo EPP in the crashproof stakes, but you did mention your radian having its' fuse in 5 pieces, and I just wanted to add my experience with Z foam/elapor. My starmax He 162 is made from really brittle foam, but gentle heat aplication with a heat gun and some deft untwisting have put it back to flying straight again. I tried hot water and steaming with less success Pulling things straight with packing tape has also worked very well. EPP has a much greater "memory " than the other foams, and generally does not need too much untwisting, and I have had the best results from hot glue and 3m 77 when it comes to adhesives. I also tried repairing my radian fuse a few times, and used gorilla glue and 3m 77 in an attempt to keep the weight down. Gorilla glue is great for gap filling, and sands down easy; Hot glue is normally reserved for really high stress joins like wing halves. Epoxy and CA is my least favourite glues, but they of course still have their place. CF ribbbon inserted in repaired areas also adds strength for minimal weight gain, and is easy to work with, along with correctly applied bi directional tape. Another word on EPP repair- you can generally only sand it in one direction, not back and forth as in a piece of timber. You'll rip chunks out if you do. When fixing combat planes that have had a section torn off, I insert another piece of foam instead of trying to glue something that a prop has chewed up, and then sand it to shape before taping. If I use hot glue, it is a real pain to sand through any excess, so I always wipe off as much as possible, and then cut a slit or two into the repaired section. A further cut is made into the undamaged foam surrounding the repair, and CF ribbon is sprayed with 3m 77 and then pushed down into the slit, giving a "bridge " effect from the undamaged foam through the inserted piece. My combat planes have been going for years with these sort of repairs hope this was of some help to someone, cheers
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Old 03-18-2012, 08:49 AM   #7
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Small items of addition ....

If you have a Workmate bench, one of those fold up vice like bench things. They are good for straightening fuselages.

Getting blocks, rags, anything to pack out the vice jaws ... you align the fuselage in the jaws, pack out with the blocks where needed and place thin block at point you want to bend back..... with soft rag or sometyhing to protect the foam. Now carefully wind the jaws closer till fuselage is caught and tyhin block is creating the slight opposite bend. Now using a hot-air blower ... your shrink film air-gun is good taking care to waft it over and not in one place too long. Basically you warm up the structure to relieve the vice pressures ... and fuselage only springs back to straight when released AFTER it's cooled.

Same procedure can be used for half wings, elevators, ailerons etc.

One point though ... warming and bending will straighten or regain a shape - but the structure still literally remembers what happened to it and is weaker / more likely to deform back again when impacted or suffer warming suich as in back of car in summer ! Ask how I know.....

Do you have a bend / crack / deformity that defies above ? The humble BBQ bamboo skewer can help here. With it's sharp point you can in your abiove workmate bench hold the article straight, skewer the bamboo into the article, cutting at length req'd. You can epoxy it in or not ... depends on location and stress.
You can as I have had to do with extreme cases ... cut the item NOT all way through but enough to open up the cut till item is straight and then inserted shaped foam pieces with white wood glue. You can fill the gap nicely with such ... it's light, the white PVA glue is excellent and light ... sand it fill with some wall filler and done.

Got a canopy that refuses to stay on / down ? Cocktail stick in end to engage in hole in other part ... simple. Both ends a problem ? Cocktail stick one end as here, other end a cocktail stick pushed in from other part with short end proud to remove by. Or a short piece of plastic such as servo arm. Small screw through into main body .. acts as turnpiece to lock canopy / hatch down.

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Old 07-03-2012, 02:42 PM   #8
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Let's bring this back to the top to help the new guys.

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Old 07-04-2012, 02:55 AM   #9
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Default I thought it was on topic?

Originally Posted by AEAJR View Post
Let's bring this back to the top to help the new guys.
No offence intended, but I thought the two previous posts by myself and Solentlife were about repairing foam.Just to add, I have tried to do the elapor soup method ( boiling water immersion) on several planes now, with no real benefit. It seems foam isn't foam, but there are obviously differing types from different manufacturers. The brittle foam on the Guanli and Starmax planes differs in its response to the repair strategies that appear to work on parkzone and Multiplex products. EPO is not EPS, or elapor, Z foam or the other variants of chinese styro out there. Just providing more info for the "new guys" to take into consideration when attempting repairs on various planes from various manufacturers....good luck....
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Old 07-04-2012, 03:19 AM   #10
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Originally Posted by pattern14 View Post
No offence intended, but I thought the two previous posts by myself and Solentlife were about repairing foam.Just to add, I have tried to do the elapor soup method ( boiling water immersion) on several planes now, with no real benefit. It seems foam isn't foam, but there are obviously differing types from different manufacturers. The brittle foam on the Guanli and Starmax planes differs in its response to the repair strategies that appear to work on parkzone and Multiplex products. EPO is not EPS, or elapor, Z foam or the other variants of chinese styro out there. Just providing more info for the "new guys" to take into consideration when attempting repairs on various planes from various manufacturers....good luck....
You seem upset, not sure why. I have not deleted any of your posts.

What's the problem?

Of course, you are right, there are a variety of foams.

EPS - Beaded - Styrofoam
EPP - Not beaded - common on slope gliders
EPO - Beaded - Becoming popular
Elapor - Beaded - A Nultiplex branded foam.
ZFoam - Beaded - A Parkzone/Horizon Hobby branded foam
Depron - don't know much about this one

I am sure there are others. And yes, they all have somewhat different characteristics. But I have found that most beaded foams will respond well to some kind of heat treatment, as outlined by the original article.

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Old 07-04-2012, 03:34 AM   #11
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I'm not upset at all It's just that your post said to" bring it back on topic to help the new guys", and both posts immediately prior to that were about repairing foam. Must be a misunderstanding Either way, any contribution to get people back in the air is worthwhile...cheers....
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Old 07-04-2012, 03:37 AM   #12
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No, it says let's bring this back to the top, the top of the forums. The word topic was not in my post.

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Old 07-04-2012, 03:43 AM   #13
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Originally Posted by AEAJR View Post
No, it says let's bring this back to the top, the top of the forums. The word topic was not in my post.
Sorry about that...I really have to get my glasses replaced, and not reply to threads in the middle of working nightshift....
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Old 08-26-2012, 04:47 PM   #14
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I read this topic just now for the first time. I'm so glad I did. I have two foam planes with damage--one a Champ, the other an Easy Star.(Have some balsa planes with damage too--) I had no idea you could repair crunched foam. This info will help greatly.

AEAJR and the rest--thankyou!
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Old 12-04-2012, 07:51 PM   #15
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Originally Posted by Beemerider View Post
I read this topic just now for the first time. I'm so glad I did. I have two foam planes with damage--one a Champ, the other an Easy Star.(Have some balsa planes with damage too--) I had no idea you could repair crunched foam. This info will help greatly.

AEAJR and the rest--thankyou!
How did your repair work out?

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Old 02-14-2013, 02:02 AM   #16
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Default a little more advice.....

I nosed in my starmax F22 testing the limits, again, and this time the whole nose section is so crunched, that when I removed the packing tape from the last repair, the foam itself has lost all of its firmness and feels like wet cardboard. Re applying tape over this is a waste of time, as it needs structural stiffness as " base". Just wondering whether it is worth using silkspan and wbpu or some other "crunchie" type coating to give it some rigidity again? It is beyond the usual repair methods, but has been such a fun EDF jet that I am reluctant to bin it. Thought about cutting off the whole front third of the plane and scratchbuilding a new section ( out of what , I am not sure) if no-one has any better suggestions....cheers
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Old 03-23-2013, 12:50 AM   #17
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What a great thread!
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Old 06-16-2013, 05:13 AM   #18
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Originally Posted by rafiraza View Post
Hi
After crash....my Rc Helicopter S08, 3.5 gyro....., rotates the blades okay but does not lift off..
I has Double set of BLADES.......both sets seem to be rotaing okay with the gears.....Charge is ok....it is only one day old....
WHAT [possible could be wrong......for not lifting off even the blades spinning at full speed?
I don't know what is causing your problem but it probably has nothing to do with how to fix warps, dents, twists or uncrunching foam parts, which is what this discussion is about.

I would suggest you post your question in a thread about helicopters. That way you are more likely to find someone who has the same heli and will be able to help you.

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Old 06-16-2013, 02:13 PM   #19
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Originally Posted by rafiraza View Post
Hi
After crash....my Rc Helicopter S08, 3.5 gyro....., rotates the blades okay but does not lift off..
I has Double set of BLADES.......both sets seem to be rotaing okay with the gears.....Charge is ok....it is only one day old....
WHAT [possible could be wrong......for not lifting off even the blades spinning at full speed?
Hello Rafiraza,, welcome to Watflyer, I'll bet someone here knows just what to do, let me try to get your post put over on the Heli thread,, your at the right place and we'll help you anyway we can,, bubsteve


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Old 06-16-2013, 08:09 PM   #20
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I moved the post about the heli problem to its own thread in the beginner forum.

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Old 11-04-2013, 09:29 AM   #21
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Originally Posted by AEAJR View Post
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, Easy Star, Super Cub 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 or a bagged wing Supra competition glider.


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 too, 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.
Thanks for taking time for sharing this,I too have used boiling water to remove some small dents and warps from foam.
When you are sanding your repaired areas, don't sand too long in one spot. The heat from sanding will cause the foam to expand into the dreaded skin condition.
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Old 11-04-2013, 11:21 AM   #22
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On Aliigator skin , I found that right after the hot water treatment, applying (rubbing) the back of a large , cold soup spoon works great to remove the alligator-like beads. The virtually disappear.

So, shortly before I do the hot routine, I place a spoon in the fridge.

Cheers,

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Old 12-10-2013, 09:00 AM   #23
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Lets get this thread going again !!

OK -there's you with your pristine foamie ready to launch and cavort the skies ...

Oh Dear - she's gone in ...

Lets assume model is in reasonable condition ... crack or break here and there that a bit of epoxy or whatever solves ... model back to one pic and flyable again. But it now has those typical nicks and dents in wing leading edge etc.

Remedy :

There are various ways to cure the nicks and dents ... but two are my preferred and they work well.

a) Taking similar foam ... packing foam ... depron ... even a broken replaced item, cut a piece that is larger than the nick or dent.
Cut out the nick or dent leaving straight clean sides.
Insert first piece into the area and glue up with PVA or similar non-hard glue that can be sanded.
Once dry - sand to shape ... any little gaps etc. - use the sanding dust with PVA to fill ...
Once sanded and faired in ... use thinned water based paint to seal the foam and then finish with required to match into original.

b) Gorilla Glue ... actually cheaper and just as good to buy the Generic PU Wood glue at local DIY shop ...
Make the nick or dent more workable by roughing up ... quite often enlarging a bit as well.

Take masking tape and film ... tape either side to create a 'box-mould' with the film as the surface glue will contact ...

Give a generous dollop of PU glue into the 'box' so it adheres to the roughed up area ... filling the 'box'.

Leave it to expand and cure.

Now you can remove the tape and film ... and as with a) sand and shape to necessary. Take care not to stress the joint too much especially if it's a dent - you can pull the repair out.

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Old 03-07-2014, 02:47 PM   #24
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Great post thanks!
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Old 05-24-2014, 02:29 PM   #25
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Thanks for the tips!...I had a float on my Flyzone Beaver that was utterly destroyed and I glued it back as well as i could but the keel-line still ran crooked...just tried the hot water method and now I'm back in business!
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