Thrifty Alternatives ..Building Foam Campers

[pat g]

Hey GPW, Eagle, Mike and All,

Thanks for this thread. You have me hooked. I plan to start building some time this week on a foam based trailer pod. I may make it removable as has been discussed here. I will start a build thread in that section when I have something to post.

Anyone on here know how tight a radius you can bend the 2 inch foam? I can figure it out but if you have already done the test, it will save me the time.

BTW I have a few pictures of my just recently completed trailer in my album. It has not even been out on a maiden voyage yet. May take it out this weekend for a trial.

Thanks,
Pat G

[Cliffmeister2000]

Eagle kerfed her 1", if I recall correctly, so I imagine you will have to put a pretty hefty kerf in 2"

[mikeschn]

Anyone on here know how tight a radius you can bend the 2 inch foam? I can figure it out but if you have already done the test, it will save me the time.


Pat G

Pat,

I don't think 2" foam will bend at all. And I've not experimented with kerfing it yet.

If you want to use 2" foam you might want to consider the weekender, as it uses flat panels.

I don't know what thickness I am going to use, nor how many layers... but I suspect I'll be doing a lot of kerfing...



Mike...

[GPW]

You know the Foam does Bend ... @ 190F ... There's the rub !!! We've routinely bent the smaller thickness foam before ...up to 3/4" with a carefully applied heat gun ... But that's tricky !!! Too Hot too long in one place and you melt the foam .... I'd thought of boiling water , much as some bend plywood ... That's tricky too , but won't melt the foam ... The kerfing seems to be the easiest way , if not the most labor intensive ... cutting the kerfs... I thought of burning the kerf slots with a solder gun ...Quick but stinky , fumes , so that Must be done outside ... a board for a guide would make it fairly easy to get nice straight slots ... careful you leave at least 1/2" of solid foam... Or one of those little zip routers would quickly hog out the kerf slots and you could set the depth fairly accurately ... Again , some type of sliding fence/guide would be necessary ...
Then there's putting on 2-3 layers of the thinner foam on top of each other ... But that requires more glue ... and Gorilla Glue would be best for this ... or a water based contact cement ...

I thought along time about this ... which is why I decided to do the more Weekender flat design ... No bending necessary ...

[RAYVILLIAN]

I've painted bed sheet on both sides of 1/2" foam and bent in a 5" radius with out it breaking but don't know if it would work with 2"



Gary

[mikeschn]

Very impressive Gary!!!

Mike...

[eaglesdare]

i did not even attempt the bend in the 2" foam. i used 1" for my curve. we scored it. they were not very particular with it, i don't think. the only thing is they made sure not to go all the way thru with the cut.

http://tnttt.com/viewtopic.php?t=43647

check that page out. scroll down you will see them marking and then you can see the score marks also as they were glueing it to the spars. you can see how far the scores are. and the next pic you can see the inside where it was scored. there are lots of cuts. not sure you needed all of them. but it took the curve perfectly.

i only used the 1 sheet of 1" stuff for my roof. i did not double up on it. 2" foam was only used on my sides.

[vreihen]

...and watch them make the new 787 Dreamliner out of carbon fiber and may be able to get some large scraps of the fabric....

I would be surprised to find out that Boeing is still doing wet layups using dry fabric. I would think that they would be using prepreg materials, cut to specific patterns for each spot by CNC machine and optimized to avoid material waste.

Prepreg (cloth pre-impregnated with heat-activated resin) yields the strongest/lightest parts due to the ability to control the resin/fiber ratio, but the material usually requires refrigeration before use and a strict application of controlled heat in a special oven to use it. Prepreg has a use-by date on it, and sometimes winds up on the surplus market for those who don't care about the material certifications that the aviation industry must adhere to.

My thought is that a kevlar foamie would be made for about half the cost of carbon. Non-ballistic 5oz kevlar is $100 for a 5'x12' sheet, which isn't exactly thrifty but is probably bear-proof if attached to the trailer frame solidly.....

[pat g]

Thanks for all the replies. I know that Eagle had at least some spars but do not think that GPW intends to use them. I like the graphic BTW, GPW.

Gary, that is impressive!

All the replies provided useful information. I do like the weekender profile, thanks Mike, but since my last trailer was angular, I thought that I'd like to try something with some radii. I have cash in hand and will go to the store tomorrow for some materials. I may experiment with a couple of layers of thinner foam for the roof.

Cannot wait to see the results some of the experienced builders achieve with foam.

Pat G

[68galaxie]

Vreihen they have the fabric for the training classes and bonding shop for repairs, they use all cnc pre cut for the body forms

[GPW]

I think Gary (Rayvillan) is on to something ... the forces involved in bending are tension and compression ... Foam is very strong in compression , but in tension the top surface wants to pull the surface apart , causing the break .... Foam breaks in tension , and as we've found , heat relaxes the surface under tension allowing it to bend ( it becomes more flexible )
If the surface is covered like Gary did , the tension forces are now on the covering material and not the surface of the foam ...allowing it to bend safely ... Now I'm sure that 1" foam covered as Gary did would bend easily around a large radius , especially on a warm day ... Possibly even the 2" foam ... once covered on the top ... It would take some straps and muscle to slowly bend the 2" , but I think it's doable .... attach one end , then slowly bend in the contour .... and a little heat from a Carefully applied heat gun should help ... Once bent with heat the foam stays in that shape with 0 spring back ... In the industrial world , we've seen strip heaters , long flat devices much like an electric blanket ... but much hotter ... so anyone having access to some type of heater should be easily able to bend foam ..

Just another thought .... If we're covering the inside first , like I'm doing now, that may be OK on a flat surfaced Weekender type , but if we bend the foam for a rounded surface , the inside covering may wrinkle with the bends ... so with rounded surfaces , you may want to cover the inside last ..

[GPW]

Doesn't Dow make a pre kerfed foam ??? http://building.dow.com/na/en/products/ ... rimate.htm


Just FYI , here is a discussion we had years ago on the model forum about bending 1/4" foam ... Its rather off topic most of the time ,boring to most , but we were able to bend permanent curves (airfoils ) in the Blu Styrofoam ... Just have to figure out how to do this on a bigger scale ... http://www.rcgroups.com/forums/showthre ... ndfoam+gpw

[GPW]

Covering is getting Much easier ... got most of it done now , just a couple little pieces to go ...

Still looks like a mattress ...

[GPW]

WARNING :.... I brushed against a dry panel and the corner skin popped off ... The smooth foam skin offers little tooth to adhere the T2 to , so we've taken to sanding/scuffing up the foam surface to provide better adhesion ... Just a light pass with some 80 grit on a block to break the gloss .... then vacuumed ...
I Do want to provide the Best adhesion possible so this extra step may be worth the little added effort ...

[CARS]

WARNING :.... I brushed against a dry panel and the corner skin popped off ... The smooth foam skin offers little tooth to adhere the T2 to , so we've taken to sanding/scuffing up the foam surface to provide better adhesion ... Just a light pass with some 80 grit on a block to break the gloss .... then vacuumed ...
I Do want to provide the Best adhesion possible so this extra step may be worth the little added effort ...

I was wondering how water based glue was going to stick to the smooth surface. In all honesty, I was wonder how it was going to stick to foam at all. I understand the exterior wrap wont go anywhere, but doing it panel by panel and then bonding them together??? I guess as long as they hold up till you get the whole thing wrapped...

Good work everyone! I am still thinking of doing a hybrid on mine. If I can get 1/2" foam to bend, I may do the roof in foam.

Problem is that it won't be "thrifty". I just really like the curved top edge that is on the drawing GPW posted! Hmmm....