box

Hello Everyone,

i have looked and looked for a fiberglass forum but it has been a futile search. i have come across several audio and boat forums.. thank god i found this forum it seems to be the best with knowledgeable persons.. i understand if you are not willing to help being its not a boat or boat project..


i am looking to build a box that will be 32"L x 2'W x 2'H and will hold about 50 gallons of water. this water will that flow through the box with static water pressure 24 hours a day 365 days a year.

materials i was thinking of using

1) ORANGE TOOLING MOLD GELCOAT MARINE, FIBERGLASS

2) carnauba based wax for release agent

3) fiberglass chopped strand mat 2.0 oz

4) resin kit


i have zero experience with fiberglass, but this is what i was thinking..

1) i was going to build a mold from 3/4" mdf and then round all the inside corners with a filler like bondo. then i would coat the inside with 5 coats of an Oil-based polyurethane varnish sanding between each coat.

2) i would coat the inside of the box with a carnauba based wax.

3) apply a gel coat

4) apply 1 layers for the chopped strand mat and roll out layer before applying the next layer for a total of 3 layers

5) ?????

like i said i have zero experience.. so the questions i have are these..

1) i selected chopped strand mat because i thought it would be the best to work with and offer the strongest sides because of the random orientation. is this correct?

2) will using 3 layers of 2 oz chopped strand mat be strong enough to hold this amount of water.

3) do i need to use gel coat on the inside of the box to make it smooth or is these something else i can do

4) what would be the best products to use on a project like this?


thank you for any input

kwick

 

No, chopped strand is NOT the strongest, especially 3 x 2oz.

based on similar builds, I would use one layer of 4 oz chop on top of the Gelcoat layer, and 6 oz (better 12 oz) on the outer layer.

Sure, its not a huge box, and maybe 2 oz chop will hold the water in - but you have to think about the whole lifecycle - I mean you could buy a flimsy plastic trough about the same dimensions.

 

I would build a box out of marine plywood and install wood inside corners. Use regular fiberglass say 7 ounce for the outside using regular epoxy. 2 coats of epoxy. on the inside do the same with 2 coatings of 7 ounce. Use food approved epoxy or water approved and give it heavy finish coat Put a round waterproof opening fitting
on the top big enough to put your arm into to finish coating the edge to the top panel and for futcher cleaning.
Simple to do, won't ever leak, will not degrade. Make it oversize to allow for expansion. 1/2 inch ply is adequate. Throw a couple of pieces of pure copper wire in loose for purity. Epoxy your fittings in before sealing top on. GROUND your fittings if metal.

 

i have looked but the highest chopped strand mat i could find is 3oz per square foot. what site should i look to for a higher weight mat

as for the 6 oz or 12 oz mat is that a chopped strand mat or a woven mat?

the gel coat will be applied to the inside of the mold and then i will be applying the fiberglass to the inside of the gel coat. should i use another layer of gel coat the inside to make it smooth? or is there another option to make it smooth inside the box.. i need it smooth so debris do not stick to the sides of the box

as for using a flimsy plastic box that will not work for this project. there will be chambers on the inside of the box with rotating parts so the box needs to be rigid..

thank you for the reply

 

i dont think i could use wood because of the added weight..

are you saying to use the epoxy instead of the gel coat?

 

I would not use MDF on anything. Awful stuff, weak, unstable in long term, swells when wet and much heavier than plywood. Mat is the weakest glass material you could use. Non-woven biax or triax is the strongest glass.

 

the mdf is just the mold or plug the box will be removed for the mdf once it is cured..

thank you for the other mat types i will look into them what weight should i look for?

 

If you have to go fiberglass look for 1708 this 17 oz per sq yd bi axle glass with 8 oz per sq ft matt attached to it,youll need a few layers of this to get the thickness that will be required.You should be able to find a chart that will give you the finished thickness of this type of glass with hand layup.

I guess pending on location and how it will be used, I'd go plywood and epoxy,it will be done by the time you make a mold.But I don't know exactly what your after.

 

Maybe it would be best to approach this differently. What's the box for?, What are the static and dynamic considerations? How many do you need to make? Final use environment, wear and tear expectations, etc., etc., etc.

It's difficult to design something, until you know what it needs to do and what it has to tolerate.

 

Indeed so.

 

1) this will be a filter box
2) it will be flowing about 3,000 to 10,000 gallons per hour
3) 5 as of now may be more depending on success
4) wet location and it could also be directly outside
5) should be none on the box itself

this is a video on you that i made out of pvc i want to replace the box with the glass box.. hope this helps shed some light into the project
https://www.youtube.com/watch?v=SDsWdes0hIQ

 

yes, use epoxy not gel. water approved. check your weights................please re-read my post,

FORGET MY POST................10 THOUSAND GALLONS PER HOUR.

 

The 6 - 12 oz is woven. The only matt is the layer against the gellcoat to create a good connection. You can get 11oz matt fairly easily, but, 3 or 4 layers of the lighter is ok. Place the woven cloth over the matt while it is still wet. Also, the heavier cloth with be much easier to drape and wet out than the lighter stuff.

Using proper measures, you are looking at 150 kilos of water, . That is about the same as two people standing in it.

Without doing any math, as well as the 12 oz woven cloth, I would be putting quite a few strengthening ribs on it as well. The flow rate at 10,000 gallons per hour is a about 3 litres ( approx 1 gallon) per minute, so its not a huge load.

If you are using gelcoat, epoxy resin may not be required, but as it has been pointed out, Polyester resin is not waterproof. The cost may not be that much different.

 

The first thing to work out is the static column of water it will need to support. Couple this with anything else that'll be in the water or box, as these are the loads the walls will need to tolerate, plus a safety margin (3:1 is typical).

If only making 5, I'm not sure a mold is the best route. A lot of costs in a mold for such a short production run.

 

That is a very small box, and there must be plenty of ice-boxes mass produced in that size range, you might even be able to approach the manufacturer and just buy the boxes without lids, it seems like the best way out to me.