Gatorboard

[rlphoto]

Zack,
I just happened upon this web page.

http://www.happitrails.com/

Teardrops built out of a foam board material.
Norm

It looks a lot like gatorboard alright. I only use 3/16 myself. It is very nice stuff to work with for a foam core, But it is still not near as strong as plywood.

[WoodSmith]

It looks a lot like gatorboard alright. I only use 3/16 myself. It is very nice stuff to work with for a foam core, But it is still not near as strong as plywood.

Ok now you're getting down to usefull info. If you have some scrap gatorboard, can you do some scientifical type tests on it for us to determine strength? Take a piece - say - 4 inches wide and 16 inches long, rest the two ends on 2x4's and stack weights on it in the middle till it breaks? Then let us know what wieght it took to break so we can get an idea of its strength.

Maybe Andrew can come up with a better test, this was the best I could come up with off the top of my head.

[Zack]

Thanks for the link.

I suspect that the SIPs they're using there are luan/styrofoam sandwiches. these are supposed to be pretty strong.

[angib]

If you have some scrap gatorboard, can you do some scientifical type tests on it for us to determine strength?

Already done here.

This is the load in the middle 12" x 12" to cause failure of a 12" wide panel over a 36" span:



The columns headed 2", 4" and 6" are the loads to cause that deflection in the panel.

For comparison, I'd expect unsupported 1/4" plywood to fail at a load of about 60lb in the same test.

Andrew

[rlphoto]

If you have some scrap gatorboard, can you do some scientifical type tests on it for us to determine strength?

Already done here.

This is the load in the middle 12" x 12" to cause failure of a 12" wide panel over a 36" span:



The columns headed 2", 4" and 6" are the loads to cause that deflection in the panel.

For comparison, I'd expect unsupported 1/4" plywood to fail at a load of about 60lb in the same test.

Andrew

Nice link! Gator is pretty neat stuff! It does contain formaldihyde however. I dont know if I would want to be shut up in a box of the stuff for long!


Randy

[angib]

It does contain formaldihyde however. I dont know if I would want to be shut up in a box of the stuff for long!

As do Formica and many plywoods, the latter perhaps mostly in the past. Did they kill or injure many people? Or have I not heard the latest scare story?

I'd bet that if I tried I could not create in a teardrop a risk to my health that is as much as one tenth the risk of driving to a campsite. If you care about your health, teardrops should only be used in your own backyard.....

Andrew

[WoodSmith]

Already done here.
Andrew

Well there you go - see I told you Andrew could come up with a better test.

So if I read the table right, it looks like it is about 1/3 as strong?

[angib]

So if I read the table right, it looks like it is about 1/3 as strong?

I would say just as strong and probably much less weight - the valid comparison would be with, say, 1/8" outer ply + 3/4" foam + 1/8" inner ply and the Gatorboard seems to be just this, but ready made.

Gatorboard users: how does it bend? If you've only used the 3/16", then I guess this is gonna bend easily. The problem could arise in trying to use, say, 3/4" or 1" with any sort of teardrop shape. For Zack's Weekender, I don't see any problem.

Andrew

[Zack]

It sounds as though I've been approved for construction! SWEET!

Returning to the issue of sealing around the door...what about epoxy? You could brush some glue around the exposed foam, maybe?

[Zack]

It sounds as though I've been approved for construction! SWEET!

Returning to the issue of sealing around the door...what about epoxy? You could brush some glue around the exposed foam, maybe?

[WoodSmith]

I would say just as strong and probably much less weight - the valid comparison would be with, say, 1/8" outer ply + 3/4" foam + 1/8" inner ply and the Gatorboard seems to be just this, but ready made.

Gatorboard users: how does it bend? If you've only used the 3/16", then I guess this is gonna bend easily. The problem could arise in trying to use, say, 3/4" or 1" with any sort of teardrop shape. For Zack's Weekender, I don't see any problem.

Andrew

Ahh right, cause we aren't using it in place of the 1/4" ply we are using it in place of the entire inside skin/insulation/outside skin panel. However, the same strength benefits that make it worth using would seem to preclude bending around all but the largest radiuses. I suppose you could kerf it, but then you need to put a skin on the inside to cover that and regain some of the strength lost in the kerfing.

Sounds almost like a wash in the long run. At least for the cieling.......

As for the sides, perhaps casing the openings entirely with wood/metal/... would protect them from physical abuse and UV light.

[angib]

However, the same strength benefits that make it worth using would seem to preclude bending around all but the largest radiuses.

That's what I'm thinking. Some practical tests might be needed - there's always the possibility that, say, 1/2" Gatorboard would bend round a large radius (so only for Cubbys, not Benroys) and, with the stiffening effect of the curve, might be strong enough.

Building strong enough for someone to climb on is a big challenge with Gatorboard, but then ask the Fiberglass RV people and they'll tell you they'd be stupid to climb on their 'eggs', that have lasted 30 years quite happily. The Gatorboard is so light* that holding itself up is not a problem.

* 10.7 lb for a 4x8 of 1/2" Gatorboard is the same weight as 1/8" ply and 13.9 lb for 1" Gatorboard is 2/3rds the weight of 1/4" ply.

Sounds almost like a wash in the long run. At least for the ceiling.......

Unless you want to build a trailer with only flat panels like Mike's Weekender (as Zack does) or my Simple, in which case it looks good.

The details of joints and edges still need to be looked at, as the extra work here could swamp savings elsewhere.

Hmmmmm......

Andrew