I need large strong trays!

[Smertrios]

I need the know-how to make some trays that would measure around 4x12 foot then around 4-6 inches deep. I believe fiberglass could be a good way to get them relatively cheap but I know nothing about working with or choosing supplies for fiberglass let alone how to make a tray that big *and* strong enough that it can support its bottom when being supported by the edges most of the time (and without much distortion). The weight per square foot would not be more than 3-4 pounds per square foot but if the weight per square foot can be made considerably higher without raising price much that would be good!

[rowbare]

You are asking an awful lot from a big piece of material. There are very few materials that size that can be supported by the edges with minimal distortion. If the bottom doesn't have to be flat, then you can mold ridges into it to help but it will take some engineering to figure it out. A lot also depends on what you are putting in the tray. An inch of water in a container that size will weigh about 250 lbs...

If you can support the bottom something like Expanded PVC might work.

[Geof]

Go and find someone who makes fiberglass boats. What you are looking for is not much different to a flat bottomed boat except the force on the bottom is in the opposite direction.

The bottom could probably be rigid polyurethane foam with fiberglass all round and my guess is that it would not need to be much thicker than about 40mm for the weight you mention.

These will not be cheap.

[martinw]

Originally Posted by Smertrios I need the know-how to make some trays that would measure around 4x12 foot then around 4-6 inches deep. I believe fiberglass could be a good way to get them relatively cheap but I know nothing about working with or choosing supplies for fiberglass let alone how to make a tray that big *and* strong enough that it can support its bottom when being supported by the edges most of the time (and without much distortion). The weight per square foot would not be more than 3-4 pounds per square foot but if the weight per square foot can be made considerably higher without raising price much that would be good!

Dear Smertrios,

What do you want it to do, and why?

I will jump the gun, and tell you about our water drip tray.

GRP/ fibreglass should work, IMVVHO.

We made drip tray 1.9 metres by 1.2 metres by 0.075 metres deep last month (say 7 foot by 4 ft by 3 inches). OK, OK, that is pretty small compared to your project, but the loading is not too awful in your case. We used a 1/2 " plywood base and timber up-stands round the edge, and glued the upstands with PU adhesive. Then we "laminated" 450 gram per square metre chopped strand mat onto it (using about 5kg of laminating resin) and brushed on another coat of resin when the laminate was still "green". I'd never done much with GRP before, and it was surprisingly easy, once you appreciate that things happen a bit fast when it comes to resin gel times. (TAKE THE PHONE OFF THE HOOK!)

Your base will obviously have to be better than a 1/2" sheet of ply, but just stick a few beams underneath. I do not know how much deflection matters to you.

Advice on this kind of thing can be had by searching on Glassfibre/ GRP roof sheathing . The technology of waterproofing plywood-based flat roofs in this way has been around for years.

I'm sorry if this is irrelevant to your particular application...

Best wishes,

Martin

[martinw]

Here is a link that I forgot to post, Smertrios, apologies,

http://www.cfsnet.co.uk/acatalog/1project-roofs.html

Best wishes,

Martin

[Smertrios]

Appreciate the replies they helped me make my decision about using fiberglass for strong trays =P... I am going to use heavy-duty shelves with wire decks and maybe a "tray" made from whatever material is the cheapest and waterproof. I believe cheap 3/16" sealed wood will make a good enough waterproof tray when using these shelves.

Just FYI the trays are going to be used for raising feeder insects

[martinw]

Originally Posted by Smertrios Appreciate the replies they helped me make my decision about using fiberglass for strong trays =P... I am going to use heavy-duty shelves with wire decks and maybe a "tray" made from whatever material is the cheapest and waterproof. I believe cheap 3/16" sealed wood will make a good enough waterproof tray when using these shelves. Just FYI the trays are going to be used for raising feeder insects

Dear Smertrios,

Whatever trays you use, here is some advice for the GRP crowd.

GRP has residual styrene that hangs about after laminating for a long time. The best advice for toxic sensitive beasties ( like fish ) is to use a low styrene laminating resin, and let it cure for a couple of weeks. Then you flush the laminate with hot water for as long as you value your beasties.

Best wishes,

Martin

[Geof]

Originally Posted by martinw ...The best advice for toxic sensitive beasties ( like fish ).....Martin

He is growing insect larvae; do these qualify as toxic sensitive beasties?

[martinw]

Originally Posted by Geof He is growing insect larvae; do these qualify as toxic sensitive beasties?

Dear Geof,

Well you really have got me on that topic.

I was always told that the last evidence of life on the Earth would be the insects, so I suppose that they do actually have a bit of a head start.

Whether or not they have developed a genetic immunity to styrene is a question that only others can answer.

My guess is that it will probably do them no good.

Flush those GRP trays with hot water, or they will die.

Best wishes,

Martin

[Smertrios]

Was thinking about using this rubber...
http://www.jgreer.com/concrete%20molding.htm

[Geof]

Originally Posted by martinw ...Whether or not they have developed a genetic immunity to styrene is a question that only others can answer....Martin

It would appear that the bio-toxicity of styrene is not a given:

http://www.ncbi.nlm.nih.gov/pubmed/7818769

http://www.sciencedirect.com/science...8cf0bad9388eb1

http://www.pubmedcentral.nih.gov/art...?artid=1475194

http://www.informaworld.com/smpp/con...all~order=page

http://www.epa.gov/chemfact/styre-sd.pdf

[ImanCarrot]

I take it these trays have lids on them? if so, that makes a box- you could stick little poles from the lid to the tray bottom which would make a stronger structure.