Epoxy for plywood tanks - Page 2

masharp1126 · #26 09/05/2007, 09:15 AM

I'm also building my sumps, and water storage containers (one for RO and one for salt water) out of plywood. I don't intend to use the fiberglass on these, but do plan on 4 to 5 coats of epoxy to ensure an adequate seal.

luv951 · #27 09/05/2007, 09:22 AM

masharp - how big are you sumps and storage containers going to be?

smcnally · #28 09/05/2007, 09:40 AM

I built this cabinet/sump combo (40 gallons) and it has been running for a month so far with no issues with 4 coats of the sweetwater epoxy. Not that a month is long, but I don't foresee it leaking in the future either. IMO, you don't need fiberglass if you build the enclosure properly. Boats have fiberglass because they get slammed around and twisted at times. A stationary sump built properly shouldn't need it. My stand/sump is polyurethane glued and pocket screwed every 4 inches. All the pocket screw holes on the inside were filled with fiberglass resin and sanded smooth and then the entire inside was coated with 4 coats of epoxy. If you are really worried, you can always silicone the corners. Silicone actually bods really well to the epoxy paint.

Fiziksgeek · #29 09/05/2007, 09:57 AM

You could also just add fiberglass tape to the joints for a little extra piece of mind, but skip laying fiberglass over every surface.

I really like the sump/cabinet combo idea...you can really maximize space that way!

I was thinking if I had some epoxy left over that I would build a spill tray just 3 or 4 inches high under the tank to catch at least some of the water if there were a leak or accidental spill.

luv951 · #30 09/05/2007, 10:13 AM

Thats a really cool design. What is polyurethane glue? What brand name did you use?

smcnally · #31 09/05/2007, 10:32 AM

I used "Gorilla Glue". It is ridiculously strong and 100% water proof when cured.

luv951 · #32 09/05/2007, 10:50 AM

I thought it might be Gorilla Glue.

What about internal supports? Are the cross braces structural, or only divider supports?

It looks like you have a simple box construction, except for the front pane, that is supporte on three sides by the frame. What is stopping the back and sides from bowing? other than the screws?

BrainBandAid · #33 09/05/2007, 11:49 AM

I built my 110g plywood tank using only epoxy. I'm paranoid about chemicals, so I used WaterGard 300 . It's the only 100% solids, non-solvent epoxy I could find in my price range, that I could get online. It's a little pricey (~$88 for 3 quarts), but it's the same stuff that's approved for potable water tank use (well, the Watergard isn't "approved", but apparently, it's the generic label version of the stuff that is. Add another eight bucks for the approved stuff) About 100 square feet per gallon, so the 3 quart kit should be fine.
A few hours after applying the epoxy indoors, with little ventilation, the smell is gone.

Just another option for you to look at.

(The sellers site is horrible to navigate, so if you want to find the page you can actually buy from, it's here.)

luv951 · #34 09/08/2007, 08:37 PM

Does anyone know if the brands that we are talking about (Sweetwater, WaterGard, Westsystem, Raka, or MAS) can be sprayed through a commercial paint sprayer?

slandis3 · #35 09/08/2007, 09:08 PM

You would probley have to thin it down and that would make it no longer safe. The thinners could leack in to your tank.

luv951 · #36 09/08/2007, 09:46 PM

Thats what I thought. I have never worked with the stuff, it is pretty thick?

Whats the best application technique, rollers?

slandis3 · #37 09/08/2007, 10:10 PM

Ive seen most people brush it on. Im going to do mine a little different.Im going to roll in on and if needed brush it one in the corners. Im not useing the epoxy for strenght, im useing it for water proof. Im going to use regular resin and fiberglass matt then cover it with sweetwater epoxy paint. Theres a guy at a lfs that built a plywood look down tank 10+ years ago using nothing more that pool paint. No fiberglass matt and its still holding great.

wooden_reefer · #38 09/09/2007, 12:19 AM

I don't know why people say one cannot use solvent to dilute epoxy resin. I used about 5% acetone on mine for the first layer. Subsequent layer I did not dilute. It seems to me that the solvent will evaporate since the plywood is porous. The other side of the plywood was not finished. My tank has not been toxic to fish.

This time though I might not use a solvent.

I think a slow cure epoxy for plywood tank application has the advantage of deeper penetration into the wood fiber. Deeper penetration into wood fiber was my reason for using the 5% solvent last time, over 15 years ago.

fillibar · #39 09/09/2007, 10:29 AM

Has anyone had any problems with SW and it degrading from UV? I checked it out on the Aquaticeco site and saw they mentioned it could take on a chalky surface after exposure to UV... But I have seen a couple postings where people say to use SW to act as a UV protector for resin. I am not building a tank (yet) but I would like to know for when I do.

wooden_reefer · #40 09/09/2007, 02:01 PM

Quote:

Originally posted by fillibar
Has anyone had any problems with SW and it degrading from UV? I checked it out on the Aquaticeco site and saw they mentioned it could take on a chalky surface after exposure to UV... But I have seen a couple postings where people say to use SW to act as a UV protector for resin. I am not building a tank (yet) but I would like to know for when I do.

I was told by an epoxy vendor here in SoCal that if you add the max allowable percentage of pigment (I think up to three precent) the cured product will have good UV resistance. How good is good I don't know.

BeanAnimal · #41 09/09/2007, 02:14 PM

Quote:

Originally posted by slandis3
You would probley have to thin it down and that would make it no longer safe. The thinners could leack in to your tank.

The thinners are VOCs that evaporate, they do not become part of the cured resin.

smcnally · #42 09/10/2007, 09:08 AM

Quote:

Originally posted by luv951
I thought it might be Gorilla Glue.

What about internal supports? Are the cross braces structural, or only divider supports?

It looks like you have a simple box construction, except for the front pane, that is supporte on three sides by the frame. What is stopping the back and sides from bowing? other than the screws?

Sorry for the late reply...Those internal braces were initially put there as supports, but I later realized they are not needed. I removed the one on the left and the area where the board was has not changed at all. It is a simple box construction with the top and bottom sandwiching the sides and back. The front frame may help support the front but isn't really there for anything more than looks. The plywood is 3/4" so it is pretty hard to get it to bow with only 13" of water when it is kept dry.