maintaining plywood integrity

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fish4me

Feeder Fish
MFK Member
Nov 21, 2008
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I have begun my 300 gallon plywood tank build after much research. All of my pieces have been cut to speck but everytime I have worked with plywood the sides never seem to perfectly mesh due to imperfections in the wood. I am most worried about my framing pieces on the front of the tank which do not line up near perfect. I decided to frame the front which the glass will go against with four separate pieces, two for each side and two go across the front (top and bottom).

I am a bit worried about the integrity of the seals b/w the plywood.......
Any tricks or helpful hints about how to fill in these cracks and simply strengthen the build by doing so.

Could I further brace internally, if so any suggestions as to what might work best.

-D
 
Since the pieces are already cut, there are still ways to address the problem. Actually it really isn't a problem if the gap is only due to "imperfections" in the wood. Small gaps are not an issue but larger ones will need to be addressed slightly different. Larger gaps should be filled with 'fiberglass putty'. This is an extra thick resin that is still mixed with hardner but you don't use fiber or mat. Just as the name implies, you use it just like putty. After it cures, it can be sandes to remove any imperfections. Small gaps can be ignored as long as you seam the joints. To seam the joints and corners, cut six inch wide strips of fiberglass cloth the length of the seams and corners. Roll these in and allow to cure before fiberglassing the rest of the tank. You can sand and feather the edges of the seams to make them invisible in the finished product.
 
By the way, there are two primary types of fiberglass resin (orthophtholic and isophtholic). I don't remember which is which but one is suitable for continuous underwater use. The other is not. Do a google search on them to find out which is which before you buy the resin. Some dealers will try to sell you the wrong one because it is cheaper (and usually because they don't stock both).
 
thanks for all the info chompers. That is extremely helpful. Where might I find the fiberglass putty. I already have the mat and the resin to use. Do you know if fiberglass resin would be fish safe without some other type of covering/coating. Can I simply fiberglass all the interior wood in the tank.

My plan was to fiberglass and then paint with pond shield from pond armor.

Update:
All wood framing is completed and a layer of GE 1 silicon has been added. Have also added braces to several of the corners and a middle brace. Next step, fiberglassing!
 
I will be posting pics tonight. I have taken about 10 pics of the plywood framing process and all of the bracing.
 
fish4me;2455490; said:
thanks for all the info chompers. That is extremely helpful. Where might I find the fiberglass putty. I already have the mat and the resin to use. Do you know if fiberglass resin would be fish safe without some other type of covering/coating. Can I simply fiberglass all the interior wood in the tank.

My plan was to fiberglass and then paint with pond shield from pond armor.

Update:
All wood framing is completed and a layer of GE 1 silicon has been added. Have also added braces to several of the corners and a middle brace. Next step, fiberglassing!
Click to expand...


You can get the fiberglass putty at any fiberglass/polymer distributor. Most boating stores will have it too. Check your phone book for what is local.

Fiberglass is fish safe after it has fully cured and has off gassed (when it stops smelling like a ship yard). However is is ugly as sin. Depending on the resin formula, it is either booger green or booger brown. So yes, coating it with the Pond Shield will be a good thing.
 
Ya pics always like new ideas on tank builds.
 
auto bondo works well too, as long as you're sealing and epoxying over it.
 
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