Fiberglass for a plywood tank???

  • We are currently upgrading MFK. thanks! -neo
I

iDRINKbLEACH

Feeder Fish
MFK Member
Dec 31, 2011
75
5
0
Miami, Florida
Hello,

Because of access and my comfort level, I would like to use fiberglass cloth in the seems and gelcoat to about 50mils. I am shoring up the top rim to eliminate any flex there. The rest of the tank seems to be very rigid and I don't expect any flex (5ft x 3ft x 2 ft high). I am using 3/4 in birch plywood and two 1/4 inch threaded rods across the top to eliminate flex. My biggest concern is when I move the tank when it is empty. I am planning on moving within the next year.

Is fiberglass cloth with resin and gelcoat an acceptable waterproofing solution for a plywood tank?

Thanks in advance and happy New Year to all!
 
The method you're proposing has been the main staple for home tank builds for decades. A 900 I built using the same method in the 70s lasted for over 17 years before I sold it. I had to move it 7 times and a couple of times were from coast to coast. It developed a small leak once that was repaired by draining, drying, sanding, and overlaying FG cloth and additional resin. The small crack was filled in with FG fibers and resin before overlay was added (I wound up recoating the entire bottom just to be safe from 10+ years of wear from substrate grinding).
Keep a running log on the site of your progress in the project.
 
Oddball, that is priceless. I new to building plywood tanks. I learn about it from watching a Youtube video in which the person making the tank uses liquid rubber. I get the genius idea of using fiberglass/gelcoat and I think I am being new, innovative and creative just to learn that this method is the "old school" method of making a tank. I feel refreshed. Thanks for your input, I feel much better about what I am doing now. :headbang2
 
I used CDX plywood. It's the same grade recommended for home-built boat hulls. I also treated the top as if it was an acrylic tank and fastened a sheet of plywood to the top (with 2 large access ports) to prevent excess bowing. Also, be sure to use glass instead or acrylic as your window. Silicone sealer adheres to glass and FG but, doesn't bond to acrylic. It only provides a removeable seal like a gasket.
 
thats wat i used as a base for my 300g ply tank.. works great for me
 
Thanks for the input.

Oddball (or anyone tat knows the answer), one question. If I am hard headed and insist on using acrylic can I use 3M 5200 rather than silicone. I prefer to buy a 4x8 sheet of acrylic and start having materials for my next build.

Thanks.
 
You don't use silicone sealant at all when working with acrylics since silicone doesn't adhere to acrylics as anything more than a gasket. You use one of the Weld-On acrylic bonding agents. Better check around the DIY forum before beginning an acrylic project.
 
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