Plywood tank - liquid rubber. Question about edges

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contoursvt

Feeder Fish
MFK Member
Nov 2, 2005
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Toronto
Hi All, I've seen some videos online about the application of liquid rubber where they make a wooden pond and they apply what almost looks like drywall tape to the corners then they liquid rubber over.

I don't get why this is necessary. If a wooden tank is built solid, there is no movement in the edges so wouldn't a few coats extra of liquid rubber in the corners be enough?

Many thanks in advance :)
 
contoursvt said:
Hi All, I've seen some videos online about the application of liquid rubber where they make a wooden pond and they apply what almost looks like drywall tape to the corners then they liquid rubber over.

I don't get why this is necessary. If a wooden tank is built solid, there is no movement in the edges so wouldn't a few coats extra of liquid rubber in the corners be enough?

Many thanks in advance :)
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That's like fiberglass cloth. Since there is a small amount of spacing in the wood you need to push the mat into the seam. It also helps strengthen the seams
 
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I see, so it kind of gets the cloth fibers into the tiny gap to fill it - I'm over building the tank itself so I think I could probably park two SUV's on top of it without flex :) ... but maybe then I should investigate and use the cloth.
 
contoursvt said:
I see, so it kind of gets the cloth fibers into the tiny gap to fill it - I'm over building the tank itself so I think I could probably park two SUV's on top of it without flex :) ... but maybe then I should investigate and use the cloth.
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Yeah you should for sure use the cloth on the seams, or else it will leak. Or you can go the safe side and do 3-4 coats of fiberglass in the whole tank and then 2-3 coats of the epoxy. Fiberglass one the inside will strengthen the tank plus not really anyway for it to leak haha
 
M@T!@$ said:
Yeah you should for sure use the cloth on the seams, or else it will leak. Or you can go the safe side and do 3-4 coats of fiberglass in the whole tank and then 2-3 coats of the epoxy. Fiberglass one the inside will strengthen the tank plus not really anyway for it to leak haha
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Oh I'm actually using liquid rubber. I did some research and it seems a few people have done 6-7 coats of liquid rubber without any seam strengthening and the tanks lasted for years. I guess the fact that the rubber is flexible means its very durable in the corners as long as the structure is rigid.
 
Just got off the phone with liquid rubber support. They said if the tank is structurally sound (no flex..etc, then there is really no need to reinforce the corners or edges with other materials but as a precaution, to build up a slightly thicker layer with a few more coats in those areas.
 
The thing with wood especially in a humid environment is that it will flex regardless of how well it's built. I believe there is a reason you don't see to many people posting on their 10+ year old tanks. I built mine to where you could easily park a car on it but I still used fiberglass in the seams because I want my tank to outlast me (and I don't want 500 gallons of water in my home floating around). Better safe than sorry, besides, it's not that difficult so it's far and away worth the extra insurance.
 
Oh I totally get that there will be some flex especially as humidity levels change but isn't I'm not sure how much movement fiberglass will take and if its expansion / contraction is much different than what the wood is capable of, I'd imagine it can be an area for separation or cracking. I'm thinking something like liquid rubber can stretch quite a bit so should be able to handle the situation. This is of course in theory.

In my case, I'm hoping to essentially have an elastic membrane that a wooden box is basically holding. for the window, I'll be using 3M 5200 which should bond to the glass and the rubber or at least from what I've read.

Well lets see what happens. Hopefully I'll have the opportunity to post an update 10 years down the road :) Fingers crossed.

BTW I'm storing the wood in my basement for a couple weeks so that it can equalize to the average humidity of the area and then I'll assemble. I think that's better than getting fresh wood from the lumber yard and doing it because it might move more once the climate changes. Again another theory :)
 
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