Let’s Heat bend Foam … Please !!! No more kerfing ...

[tomhawk]

… Any questions ???

Once bent, is there any spring back? Do you need to over bend a bit to compensate?

I am thinking doing two 1 inch thick layers and laminating them like folks have done with kerfed foam might be easier than bending 2 inch foam?
See: http://www.tnttt.com/viewtopic.php?f=55&t=54099&start=120 for George's example.

I was in NOLA last week. It was not any warmer than Iowa. However, we don't get dew points like Louisiana. My glasses kept fogging up when we left air conditioned spaces.

Thanks for the video!

Tom

[GPW]

Tom there’s a little springback , not much and that’s easily taken care of … The thinner materials didn’t do that hardly at all .

In the past for making foam wings , we marked off a couple inch intervals on the foam and bent the curved shape in a little at a time , and we put a “stop” on the bending board so it would only go so far making the same bends reproducible so each wing had the same exact shape … We could do that for gluing together two pieces ... Or just bend the thicker material … It’s really not difficult as one would think …

[OP827]

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

Heating internal, i.e. compressed foam surface only makes more sense to help foam bend while external surface remains cool to help maintain needed geometry.Only a narrow strip would be required to be heated and then when one feels that the foam bends, then keep moving the heat jig... Subscribed, will follow your jig experiment I do not see a reason it can not work... with a right jig and method.

[GPW]

i think once we fine tune this bending process for home use , it will revolutionize TTTrailer building … just sayin’ …

[DaddyJeep]

Ok, so you made that look too easy. I wonder if my issue was really old (27 yr old) foam or I just need to be more patient. I have another idea for when I get some new foam.

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I built this oven for my BBQ business. It is just big enough to fit the pieces for all of my bends.

[GPW]

Nice heat box …

[DaddyJeep]

Ok.... I tried again with a little more patience and a new idea. Much better results this time. With a form to bend over I think the results will be even better. It was a little tough getting a nice uniform curve to match the radius I needed.

I found that a foil backer helped distribute heat around the back.

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I used up the rest of my scraps starting to visualize my compound radius.

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[GPW]

OK, there ya’ go !!! NIce job !!!

I was thinking about bending the sheets to a nice contour and then making the sides to fit that curve , rather than the other way around , but either is entirely possible , as you can see now ...

[tomhawk]

I bought a heat gun and have experimented with bending foam. One thing that I noticed was I don't have enough hands to bend foam and hold heat guns.

Here is an idea to possibly achieve more controlled bends of larger sheets. A board acting as a foot pedal depresses an attached bending board that deforms the heated foam lying below it. The maximum deformation of the foam is limited by the spacing(D) of additional boards lying on either side of the line beneath the bending board.



Here is the realized bender. Note: I added bungee cords between the table and the foot pressure bar to return the bending board to an elevation sufficient to allow travel of the foam to the next spot to be bent.

The foam here is only 0.75" thick. So far I have only tried bending small pieces of scrap foam. I won't try anything larger until Spring since I need to give back the garage to the car until then. I feel confident this will work with 1" foam. 2" foam might be difficult. I am not sure how much more difficult wider pieces will be to bend. I suspect using more aluminum foil to direct air flow and retain heat might be useful.

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I, for one, would like to hear what other folks are doing with bending foam.

Tom

[GPW]

For bending large sheets of Foam , I envision THREE people needed , One to heat the upper side , one to heat the backside ,and one to do the bending … a “family” project ...

[DaddyJeep]

Since I am back to finally building my camper and have got to the point of adding foam it is time to put some more effort into this process. For those that are not familiar with my build and all of my challenges with curves... here it is.



I built a quick form to bend the foam over. The first couple pieces shown here worked ok, but it was a very slow process. These were only 4" wide pieces. The spacing between my internal structure is about 21". I have some thoughts and will update as I pursue them.

[QueticoBill]

Congrats on getting back to it.

I wonder if a row of infrared lights - like in a row on a bar over worktable - wouldn't heat large areas uniformly.

[OP827]

Here is an idea that was mentioned on this forum before on bending foam by compression method. There is nothing really new, similar idea and technique was used centuries ago for steam bending hardwood when a steel banding is fixed to the wood layer that will be stretched so that the whole piece mostly gets compressed during hardwood steam bending. It should be possible to do the same with XPS foam by using large sheet metal sheets with angles fixed to edges to keep foam in compression while bending.

Skinning one side first and then bending could be more practical:

1. Glue thin plywood (3mm thick, less is better) or thick canvas or thin flexible FRP to one side of XPS foam 3/4" to up to max 1.5" thick, depending on curvature required.
2. Carefully bend the above mentioned sandwich with uncovered foam surface facing inside the required curve.

Since foam is relatively soft on compression it should conform to required shape without too much force. Glued outer skin will prevent foam from cracking. Foam can be glued with gaps on plywood to then glue the plywood skin to curved framing. Internal skin such as canvas or other type will have to be applied after the curve is shaped.
Curved panels can be made and then glued together. Or curved framing built first and then one sided foam panels are bent and glued to framing.

Heating foam takes time and electric power. What do you think?

[pchast]

Just had an idea?
Do you know a Luthier?

There are heating blankets used bending wood for instrument sides.
Not your usual sleeping blanket. I'm told they can be controlled to
provide a specific temperature .

[OP827]

Just had an idea?
Do you know a Luthier?

There are heating blankets used bending wood for instrument sides.
Not your usual sleeping blanket. I'm told they can be controlled to
provide a specific temperature .

Yes, just need some quantity of these blankets and they might be a little too hot for foam.
This underblanket pad might actually work as its highest temperature setting is ~+50oC which is getting close to XPS foam softening temperature of 60oC.
At +50oC XPS foam could be sufficiently bendable.