Teardrops n Tiny Travel Trailers

You know ( or may not know) we’ve been heat bending thin foam sheets for many years now … It’s very easy , it’s quick , and as soon as it cools it keeps that shape forever… no “springback” … And especially no kerfing , which turns out to be a messy job one way or the other, and actually weakens the panel , whereas a heat bent curve retains all of it's material strength , plus takes on the strength of the curve too … We need to do this for our trailers … and it has to be able to be done cheaply at home … or garage , barn, shed … or even outside .

The goals ….
1. Heating Foam to 190 F - 212F … to make it easy to bend ..
2. Making a form to bend exact curves to … ( maybe finally a use for your kids old skateboard ramp … )

My thoughts are, it’s going to take a couple friends to help make it easy to do …

You guys have any ideas ?

I think it would take a long time and a big oven to heat 2" of foam to 200º.

I find kerfing on a table saw with the vacuum hooked leaves very little mess. But I'm not dealing with full sheets, either.





Tony

If building like Tony or as I plan to with ply skins, it should not matter. Even with fiberglass skin, its the skin. PMF and this might make a difference. Seems unlikey a home builder and bend 1 1/2 or 2 inch foam to typical td radii.

My latest thinking is we don’t have to HEAT but a little bit at a time . making it relatively easy for two people with cheap HF heat guns to heat an area of around 4’ by 8” , one on each side , Tension and compression.. Then you could bend that heated edge slightly over a PVC drain pipe or something rounded … move on a couple inches and bend some more ... I’ve done it for years with thinner foams … I’m pretty sure it would work and be relatively quick with a couple semi skilled helpers … Less than a $50.00 investment to try it out Couple of those and you’d have an Instant nose , either vertical or horizontal … no mess . Just a possibility ( “ schmaybe” ? )

Guys , you know I’d be trying this myself if I wasn’t already feverishly working to finish our EVAC trailer here at almost the height of the Hurricane season … Eventually we’ll get a Round tuit !!!

OK. Here's a $36 digital temp controller that goes to 210 F, adjustable. Simple extension cord style, whatever you plug into the "OUT" gets turned on and off based on the probe reading.

https://www.amazon.com/Temperature-Cont ... 1013&psc=1

Buy that, and plug your heat gun into it. Tent the sheet of foam, put the heat gun blowing into the tent, and at the other end arrange a hole for an exit vent so the hot air passes clear over the foam sheet. Stick the temperature sensor on the sheet of foam.

Notice it's a bit weak, only 1100 watts, make sure your heat gun isn't too big. It should hold a pretty accurate temperature as long as you wish.

Thanks , that’s an idea …

Has anyone tried heating matts? There must be something like this judging by the name of the heat controller in the previous post.

Slap on heat mats to both sides of the foam. Cover with blankets of insulation to incubate. Open it up to bend

Oh yes there are heating mats. Try Omega at this link https://www.omega.com/temperature/

Or try Briskheat at this link https://www.briskheat.com/

Silicone rubber industrial heating pads ( they like to call them blankets) come in an endless variety of shapes, sizes, and power ratings. This one is 200 dollars for one foot by two feet.



I was once a senior engineer at one of those two. I think the air heat gun will work better. The pads deliver great heat, well controlled. But only to something in direct contact. The foam has a poor thermal conductivity, the heat won't spread out really at all. That's what makes it a useful insulating foam, it's kinda true by definition for any good insulating material. The heat gun in a tent will eventually heat the whole sheet of foam evenly no matter the size or shape.

I like that little controller above because it solves all the problems for less than fifty dollars. At omega and briskheat you will see many controllers that need you to add a thermocouple or RTD sensor, or add a power cord or add a solid state relay. That little all-in-one controller ( or one like it) is ready to plug in and use with nothing added. The top of its control range is only just where you asked, no headroom for a higher temp setting. Google around for”inexpensive PID temperature controller” to find others like it.

I wonder if an electric blanket or electric mattress pad would warm it enough. Maybe it doesn't need to be at 190?

...Or, sandwich the Styrofoam between the two to heat it up?

Couldn't hurt to give it a try, right?
Any heating blanket or pad that's UL listed (all of them are UL listed) has to have a safety over temperature thermostat in series with the main control setting thermostat, so they only get so hot before they shut themselves off in case the main control somehow fails ON. I don't know what that max temp is for consumer heated sleeping blankets and warming pads in the UL standards, but I expect that would be down around 115 F or so. The industrial pads go much higher, over 400F.

I'd love to know what you find that works well.

What we found … the xps foam will bend at a slightly lower heat , but very slowly … and although we’ve never tried it , a electric blanket may ( or may not ) work …Industrial blanket heat will have to be “controlled” A 1’ X 4 ‘ industrial heat blanket would work and not be too pricy …
The 190F softens the foam enough to bend easily and quickly , but not enough to melt , although with heat guns , you must keep them moving or they will melt/blister the surface if careless … But the bending process ( as done on thinner foams ) is fairly quick and not difficult at all …

I don’t think we’d want to soften the whole sheet of foam at once , unless we had a form/mold to drape it over…. otherwise it’d be like handling a big flat floppy noodle …

Trust me , heating a relatively narrow area is pretty easy with heat guns and making small incremental bends result in a nice rounded surface … That Retains that shape forever afterwards , no bracing and STRONG …

Here’s how we did it in the past https://www.rcgroups.com/forums/showthr ... t=bendfoam

Similar principle ...

GPW wrote:
... I don’t think we’d want to soften the whole sheet of foam at once , unless we had a form/mold to drape it over…. otherwise it’d be like handling a big flat floppy noodle …

Good point. That's the kind of deeper insight that comes from actually doing a thing with your own hands.

I used to bend lexan to make boat windshields at a boat factory. Cut the lexan to shape, put it in a big oven similar to a pizza oven, pull it out when hot, lay it on a mold and gently push it to bend it (wearing oven mitts). Clamp down the top mold piece to hold it in place, and let it cool for a few hours.

Solar ovens can reach 200F easily. Wrap the foam piece to be molded in a plastic bag. Use silver space blanket type tarps to focus the sun on the foam piece. Maybe a black cloth on top of the foam piece would help collect heat. It might work.

I like the idea of solar with reflecting panels. I would add a box of foil faced foam or wood around the area to be heated to keep the heat in with a fan inside to move the air around. I think you would need an hour at temp for the heat to soak into the center of 2" foam. Heat it then bend over a form.