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| General RC Aircraft Discussion Discuss anything RC related |
Topic Review (Newest First)
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| 06-19-2010 06:05 PM | ||
| Tyler P |
Re: Foam properties when subjected to heat The foam used in Multiplex products, Elapor, pebbles up when exposed to extreme heat. It turns into something akin to reptile skin. I never had any issues with it becoming brittle with sun exposure or anything like that. It did have issues with hitting the ground, however.  
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| 06-19-2010 03:37 PM | ||
| rustycan |
Re: Foam properties when subjected to heat On RCGroups you can find instructions on oven bending foam sheets |
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| 06-19-2010 03:23 PM | ||
| Guest |
Re: Foam properties when subjected to heat When I saw the header, I started thinking about cutting and out-gassing of volatiles due to the hot wire. Seeing that it's leaving the model for extended periods in the car or trunk, I agree with everyone's comments on the impact of UV and heat. Probably one reason why foam ice chests rarely last more than a season..... Seems that the same rule applies to Formosas... keep out of heat and direct sunlight for extended periods and a combination of the two (as found in the back seat or trunk) aren't going to improve its strength. |
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| 06-19-2010 09:06 AM | ||
| Ken Currell |
Re: Foam properties when subjected to heat Quote:
The darker the colour the more heat it absorbs. |
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| 06-19-2010 12:50 AM | ||
| Cross Check |
Re: Foam properties when subjected to heat Hi Max, It has been my experience with polystyrene foam, either molded or scratchbuilt hotwire construction, that heat differentials will cause warps. Unless there is some form of spars/rigging/skin to keep the structure straight. The hot midday sun on my unsupported foamy wings can give me +/- 20degrees of dihedral.  I can 'flip the plane like a BBQ burger', but, I never get a straight wing flight. Although it works in cloudy/ cooler weather ! Unprotected polystyrene from sunlight/UV rays, just breaks down. Period. The thinner it is, the sooner it breaks. The molded 'EPPy' (expanded polypropelene?, that is more 'rubbery' than styrene) plane I have flown for a few years is better, but the thin TEs are getting more brittle/breakable as its time in the sun goes on... Just my experience with plastics, my friends... Balsa gets more practical every flight. Stay Calm, Be Brave, Wait for the Signs... Take care, Have fun, Dave'crosscheck'Fallowfield Maac 6437 Unabashed Combat Team |
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| 06-18-2010 02:15 PM | ||
| Chrisfly |
Re: Foam properties when subjected to heat Hey Max Gravity is probably the biggest enemy! Okay, so back to your question. I will not profess to be a foam expert, however I can tell you that the ability to handle exposure has a great deal to do with the type of foam. Also having lived the majority of my life in Africa I am very familiar with how rapid the decay in "cheap foam" can be when exposed to the sun or just heat. There is a great description here of EPS, EPP, Elapor etc.. http://www.rcgroups.com/forums/showthread.php?t=986842 From my experience the stuff GWS use for the formosa and other similar models (EPS) is extremely sensitive to heat.. Sometimes these kits can be brittle right out the box (although I have not had that issue here.) In fact, Heat and UV are major enemies of their products and even a short period in a hot trunk will affect the mechanical properties significantly. You can get spec sheets from various manufactures of EPS that claim things like this: "Long-term exposure to sunlight causes yellowing and a slight embrittlement of the surface due to ultraviolet light. This has little effect on mechanical properties. If stored outdoors, cover EPS with lightcolored, polyethylene film or tarpaulins"Got love that word "embrittlement"  , but I guess it describes your issue. Of course for insulation purposes it is seldom an issue as barriers are not subject to mechanical stress like our planes.BTW I also noted that Horizon and others have vague notes around Do's and Don'ts.. "Avoiding the Heat and Sun:So, bottom line - I avoid heat and the sun as much as possible as my experience is the same as yours. There is no other choice but to keep them out the trunk on hot days or crash 'em quick enough that you can throw them out and build another one. Cheers Chris |
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| 06-18-2010 12:27 PM | ||
| Ken Currell |
Re: Foam properties when subjected to heat This response is from personal experience. I have used foam sheets for insulation, both pink, blue, white and also expanding canned foam for the same purpose. The expanding foan said right on the can that you were required to paint it to protect it from Ultra Violet light from the sun. The sheet foam doesn't mention it at all. Results The expanding foam turned to brown in daylight without even being exposed directly to the sun (I waited several months before I painted it). It would say that it was deteriorating at a fairly fast rate. One sheet of the pink foam (closed cell) that I purchased as a broken sheet that had been exposed directly to the sun in the lumber yard for several months was also showing signs of deteration. A piece of old white foam I had laying around (probably open cell) just about fell apart in my hands. No experience with the blue but it would likely be identical to the pink in the sun. In my opinion UV exposure appears to be the biggest enemy of foam. You did mention about hitting the foam in the past. Foam can crack easily. The next time it is bumped the crack will get bigger. Eventually it will break with only only a light touch. |
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| 06-18-2010 10:14 AM | ||
| Max |
Foam properties when subjected to heat Okay, I want to hear from the foam experts, particularity those that have an engineering knowledge of foam and its properties. I would also like to read up on any data or papers regarding foam and the issue I would like to discuss. If yu have an links or can refer me to printed material on the following subject, please do! The issue is Foam properties when subjected to heat. I have been flying my foam Formosa almost daily for several weeks now. I just keep it in my car, sometimes in the back seat, sometimes in the trunk. Yesterday, I had the a piece of the elevator break off when I stuffed it in the trunk after several flights I fixed that, and last night as I was getting something from the trunk, the rudder broke off when I handled it again. 2 hangar rash breaks in one day.  What irked me the most was that the second break (on the rudder) happened with almost no force on the rudder. I know I didnt bang the plane that hard, as I have done it many times before, but last night the foam seemed to be less tolerant to abuse. And that got me thinking. Maybe it is more brittle due to exposure to sunlight/heat So my question is: WHAT is the effect of sunlight/heat on foam? At what rate do the bonds of the foam granules degrade with heat? (I know they do, but I don't know to what degree at what temperature) I am eager to hear from anybody with any knowledge or publications that I can refer to regarding this matter. Thanks! |
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