Foam thickness and strength??

[GPW]

Strange machine....just proves the denser,heavier foam is stronger...and by how much according to their standard , yet not understood (by me) Just some kind of crush test eh ???

[Conedodger]

Thats why i posted it, as i thought there was very little strength in the foam and this is saying there is.

Its not a crush test its a bend test. At the bottom of the machine you will see 2 metal rods and black brackets. They take a piece of foam thats 1" x 1" thick and place it across the 2 bars like a beam, The verticle part then bends the beam and records the results.

The material fails the test if at 60psi the beam has 5% or more deflection

However as the beam is longer than 1" there must be some calculation.

60lbs is 27kgs so quite a lot and IMHO there is no way a 1" piece of foam would not fail with 60lbs on it.

I am going to contact them

[GPW]

Please be so good as to do so ... doesn't sound right to me either... Having used foam for many years , it is Strong ... if used right ...

[tinksdad]

I'm going to throw in another idea running through my addled brain. Sometimes I just run with first impulse and other times I tend to over think things. Just a thought on increasing the area for glue application at the joints.

I don't know the proper terms, so I added a picture to try to illustrate. If I can ultimately find 2" foam locally, the idea is to use the router and cut rabbets (?) at the joints and increase glue area by 50% {the blue in the picture}. If I end up face gluing 1" sheets together, just cut one smaller than the other to achieve the same effect {the pink in the picture}. I am thinking the bi-directional glue joint would add some additional strength to this juncture of foam.



If the 1" bends fairly easily as alluded to in another thread, I may even be able to redesign some curves into the trailer instead of all straight lines. Maybe a combination of 2" for the walls and 1" for the roof.

[Conedodger]

I finally found a company who supply the foam in the UK (Yippeeeee) and after a call to them they were so interested that i was put through to a senior technical sales person. They sell a lot to caravan companies as made up panels. These have alluminium on the outside and a finish ply on the inside.

The foam he suggested is what is commonly used under floor boards in house building which already has a perfectly cut rebate as in your picture (blue one) all the way round. Its available in 2500mm x 600mm (8' x 2')

When i asked about it only being 600mm high and would mean having more joints he was clear that a well glued joint is stronger than the plain foam and vertical joins can be staggered. They use a 2 part glue and in testing the foam always breaks way before the joint. The rebates fit together to make a perfect flat surface or a perfect right angle join. He explained that normally (under a floor) these are not glued together and a butt joint could slip where a rebate one does not.

He suggests that glueing two 1" pieces together is not a good thing and said as all glued foam joints "MUST" be clamped so the joint is under pressure until dry, on such a large joint a DIY builder could have a problem.

I said i was sure it could be done and he agreed but it would need a perfectly flat floor and perfectly flat weight so the same weight was distributed all over the join. He thinks with DIY when you lift off the weight the double foam would be wavy when viewed along its length.

I think he then realised i only wanted a few sheets so made an excuse to go as he had to quote on panels for 140 prison vans.

Two things he would not comment on was the use of PVA (TB2) and cloth covering and using GG on joints as he had no knowledge on this.

Company details:

I first contacted http://www.styrofoam-online.co.uk and they are also http://www.panelsystems.co.uk

lots of info on there

[GPW]

Great resource Cone !!!! I'd Love to see the Al clad foam ...

Dad, the more gluing area the better ... every little bit adds up ...

[Conedodger]

Just had an email asking if i want to visit the factory, I have said yes and will take a camera when i go (If they allow me). I wonder if he thinks I am going into business building TTT's

Also Tinksdad, section III of this http://www.hookedupfilms.com/category/huf-adventure-vehicle/ has a video of him joining foam.

The camper is a bit like what i want to do and he is using wood glue until wrapped, and it looks like PVA, he is then using screws so i wonder is he has any idea that the PVA will never dry in the middle.

[eaglesdare]

i hope they allow camera's, but i wouldn't be surprised if they did not. enjoy that visit. can't wait to hear about it.