How does the Gel coat work

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projectile

Gambusia
MFK Member
Oct 24, 2007
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hi Guys!
how does the "Gel" coat in Plywood Frp tanks work?
Do we get a smooth finish with it?
or do we need to sand the frp down before applying "gel Coat"

can somebody pl shed some light on using polyurethane rigid foam + frp laminate, cause its looks like an easier option for making tanks/outdoor tubs/ponds probably eliminating plywood on the whole (some boat builders pl chip in)

Projectile
 
projectile said:
hi Guys!
how does the "Gel" coat in Plywood Frp tanks work?
Do we get a smooth finish with it?
or do we need to sand the frp down before applying "gel Coat"

can somebody pl shed some light on using polyurethane rigid foam + frp laminate, cause its looks like an easier option for making tanks/outdoor tubs/ponds probably eliminating plywood on the whole (some boat builders pl chip in)

Projectile
Click to expand...

I'm not exactly sure what you're asking. If you buy pre-maded panels of FRP you don't need to apply and gel coat to it.

If you mean making your own fiberglass reinforced panel, then gel coat is not necessarily required. There are fish tanks that have been sealed with nothing but basic polyester resin. Gel coats, especially vinyl ester or epoxy gel coats, do decrease the moisture permability of cured polyester resin. People have taken this to mean that polyester is not waterproof but that is really not accurate.

If you want to make rigid foam panels this is certainly doable. But I suspect it will be much more expensive than plywood since more mesh reinforcement and resin will be required to achieve the same strength and/or rigidity. That's an educated guess on my part, but a guess nonetheless.

Just to be clear, in theory any fiberglass reinforced tank could be built with enough layers of reinforcement and resin to the point that all of the plywood could be removed and the fiberglass tank left could be strong enough to hold water on its own. Having the plywood there reduces the need for that much reinforcement and resin, thereby bringing costs down.

I hope this helps.
 
Thanks a lot , I want to make frp tubs like the ones we get to see in many thai videos.
Those blue coloured tanks/above ground pools are almost 2" thick and very smooth on all sides . that kind of thickness can easily be achieved via foam and also making a seating for glass/acrylic would be easy when working with foam for an average diyer( no screws , no sealing of holes etc ).

This is just a wishlist , the real procedure might be very different, I stay far away from any beach hence can't check it up with any boat builders .

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projectile said:
Thanks a lot , I want to make frp tubs like the ones we get to see in many thai videos.
Those blue coloured tanks/above ground pools are almost 2" thick and very smooth on all sides . that kind of thickness can easily be achieved via foam and also making a seating for glass/acrylic would be easy when working with foam for an average diyer( no screws , no sealing of holes etc ).
Click to expand...

Can you post a video or two? I'm curious to see these.

To address my previous reply, I should say I'm less concerned about the strength of the foam than I am the rigidity. Even the extruded polystyrene foam sheets you can buy at home centers (the pink or blue ones) are incredibly strong. But to support a window you would need to support them enough to minimize flex and that's where it could get expensive. We know that foam panels can be made rigid with resin and fiberglass but the question is how much?

And to address the question in your thread title, gelcoats are really just resin-based topcoats that go over a mesh reinforced resin system. They can be used to create a more finished look or to decrease the moisture permability of the structure. But they are not absolutely required in DIY tanks.
 
That's a fiberglass aquaculture tank that appears to have some sort of decorative matching panels on the outside.

There are a few approaches to making these. Basically you make a mold and saturate it with release agent and then do your layup work inside of the mold. Once everything is cured the product slips out of the mold or the mold is taken apart. Many of these aquaculture tanks with those stiffening ribs have to be done inside of molds that can be taken apart because their shape doesn't allow them to slide out.

These designs require a lot more resin and reinforcement fabric because they are free standing.

Layup work can be done by hand or with a chopper gun or some combination of both.

If you're only making one tank I would encourage you to make the "mold" part of the design. If it adds structure you don't need as much resin and fabric for it to be sturdy enough to hold water. Of course one way of doing this would be to make a traditional plywood tank.

Do you have some reason why you want a free standing fiberglass tank? Is there a reason why you're considering making one with foam panels (other than ease of construction)?
 
Considering foam as a replacement for plywood (weight) and I like the overall surface finish (smooth) of these tanks ( plywood+frp is costlier than glass where I stay , them taxes I guess ).

Thanks for all the inputs guys.

Sent from my GT-I9003 using MonsterAquariaNetwork App
 
Bump , cmon boat builders and sea shore dwellers , help out a fellow land locked mfker.

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projectile said:
hi Guys!
how does the "Gel" coat in Plywood Frp tanks work?
Do we get a smooth finish with it?
or do we need to sand the frp down before applying "gel Coat"

can somebody pl shed some light on using polyurethane rigid foam + frp laminate, cause its looks like an easier option for making tanks/outdoor tubs/ponds probably eliminating plywood on the whole (some boat builders pl chip in)

Projectile
Click to expand...


Greenterra has a wonderful 800 gallon fiberglass tank with gorgeous fish.
Here are his threads on his tank build:

http://www.monsterfishkeepers.com/f...3-Plywood-fiberglass-and-800-gallons-of-water


http://www.monsterfishkeepers.com/forums/showthread.php?254175-794-gallon-ply-tank-build


Have you considered using polyurea as a sealant? It can be applied to a variety of surfaces, is waterproof and is used in potable water tanks, fish tanks, pools, etc.

http://foammesa.com/roofing/roofing.shtml?roofingtabs=4


http://polyurea.com/spps/ahpg.cfm?spgid=89

You would need a polyurea contractor to spray it on for you.
 
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