Teardrops n Tiny Travel Trailers

The foam will expand if you can get it to the temperature you need to bend it but you can then sand it fair afterwards.

... since we will only be bending in small increments at a time ( creating a much larger curve, small bend by small bend bend ) we only need to heat a little area of the Foam and in that area only the top and bottom surfaces … The middle of the foam doesn’t feel the full tension and compression forces and being thnner , just goes along with the bend …The top (outside of the curve is being stretched , the inner curve (inside is being shoved together , or compressed) Just a little heat makes this process easier .
...and then it cools completely in a minute , no waiting … stays bent in that shape permanently .
Just a couple cheapest Harbor Freight heat guns and a “bending jig” is all we need … And as soon as I get the FoamStream repairs finished, I’m going to make a jig for bending 1” & 2” foam , and a You Tube video of the process … ( bending 1” will be EASY )

Anyone wanting to test this without much investment , just lay a piece of foam over a table edge , heat along that edge with a heat gun ( or a kettle of boiling water = 212F ) and apply pressure to the outer end till it bends where you want … hold it there till it cools … and then you’re done … If you mark the foam with a line across every few inches, and bend slightly at each mark , you end up with a nice Curve …




Trust me , once you bend your first piece of foam to the shape you want , you’ll see how easy and quick it is , and with no mess to clean up or track in the house …( and have to clean that up too)… It does take some help , but it is Not difficult .

I know all this seems as incredible as the original idea of someone making a camper trailer out of foam ( we know that works, now )… but if we all work through this , well be able to essentially build any shape we want …

You guys could come over and put the foam on my blacktop driveway! :-) Seriously, the comments about foam being slow to heat and slow to bend should be obvious, foam being a super insulator. I could not get my roof ply to bend so I pre bent it half way over night. I suppose foam could be tented in clear plastic sheet in the sun over blacktop and a simple jig putting gentle pressure on the bend. A heat gun would then work better after several hours in the hot sun.

An interesting experiment as I have never liked the idea of kerfing the foam.

Tt

This is interesting … https://www.youtube.com/watch?v=OwABZT2pIn8 in some pics , you can see the heat gun handy …

GPW wrote:( bending 1” will be EASY )

I did my first test of this process last night and was not blown away at how easy it was. My camper has a radius all the way around the edges so I will need to bend a fair amount of 1" foam.



The spacing between my framing is 21" - 23" so that is the size of piece I will be bending. Maybe picking up a second heat gun will help instead of going back and forth. I am anxious to see your video of how easy it is to bend 1" foam GPW.

Thanks for sharing your actual shop-floor test.
I still think the idea has a lot of merit, but getting even heat on the foam to a precise temperature will be a trick.

Using engineering-speak, the foam has both low specific heat and a low thermal conductivity. The low specific heat means it changes temp fast in both directions. Put too much heat gun on it and it melts right away. Move the heat gun away and the foam temp races back down to room temp, so its gone hard again when you move away to heat the bit just over a few inches. The low thermal conductivity means that the heat just won't spread out from the spot you are aiming the heat gun. To use a simile, our foam is a lot more like a loaf of bread and a lot less like a pan of water. That's why I think an oven will work better, like it does for bread. The oven is the heat gun with a temperature controller blowing into a tent with the foam inside.

The original poster GPW might have trained themselves to developed just the right touch and feel with that heat gun to dance the gun around just right, like the skills a good car painter develops for using the spray gun.

Me, I'd build that tent/oven, turn it on at breakfast, and check the foam after lunch.

Of course there is always a few approaches that can work. I suppose if we put a strip of thick metal (high specific heat, high thermal mass, high thermal conductivity) laid it onto the foam, and used the heat gun on the metal, it would evenly heat the foam underneath and keep the temp stable.

I just keep the gun moving backing forth with an eye on the surface … any melting (shininess) or bubbling means we’re too close or not moving fast enough … but then again , we’re only heating a small line across the foam , not a large area which would be subject to the science "a guy” was talking about … ^

GPW wrote:I just keep the gun moving backing forth with an eye on the surface … any melting (shininess) or bubbling means we’re too close or not moving fast enough … but then again , we’re only heating a small line across the foam , not a large area which would be subject to the science "a guy” was talking about … ^

You are just going to have to show us how it can be done.

I'm thinking steam with a box to keep the heat in. I've measured how long it takes for the heat to soak through a 1/4" of XPS and I think it's going to take an hour or more for 2" foam.

In the drawing above of the bender , what about using a steel pipe and forcing hot air or water through it.

The bender unit has been tried many ways by the RC guys , but the simplest is still the best …

Now that we’ve caught up with the FoamStream renovation , we’ll have to construct a bender for the 1” foam out of scrap … Hopefully we can make a quick video … Stay tuned ...

“You are just going to have to show us how it can be done.” …. https://youtu.be/5WVKttqb6HQ

… and to the extreme … sorry about the low rez video , new camera …

Any questions ???

Looks pretty easy, but what would be your approach to bending a 60" wide piece of 2" thick foam?

It seems that as you pass back and forth over that width there would be significant heat loss and would take a long time to get hot enough (if ever ).

You’ve seen it !!!!

For big sheets … Two people with heat guns , one on top ,one on the bottom , despite what you think it will do , you can obviously see it will bend , that’s just with a little 1000Watt hobby heat gun … Then you need one person doing the pushing/bending … 3 people … That’s why it may require the help of friends or family for big sheets … ( and a little PRACTICE handling a heat gun or you’ll surely scorch it if you’re not paying attention... )

The whole secret is to not be greedy or rushed and try to do too much at one time ( a No No ) …. you can actually FEEL it letting go , bending a little at a time … With two people heating top and bottom simultaneously it will go much quicker…

Now what to do with this 1” foam Taco … ???

Watch the video … https://youtu.be/5WVKttqb6HQ

Now I don’t know about heat loss in TN , but here in LA it’s Hot as Heck , my pickup truck emblem melting ... There’s NO heat loss here … Maybe don’t even need a heat gun .