starting my 70" long, 46" wide, 25" tall build

[scottswald]

looks like a good job, keep us updated

 

[greenterra]

went out to the garage and sit in the tank and used my legs to push against the back of it as hard as i could, nothing popped or cracked but the center of the plywood did bow just a little, maybe 1/4" tops. so ive decided to add 3 braces to the center and 1 or 2 on each side. i guess to make everything smooth i wlll go buy some 1.5" foam to put between the braces on the side and back then fiberglass it. extra insulation never hurt.

At 25" high you won't need any vertical uprights at all. That is if you are definitely going to fiberglass it inside and out as stated earlier in the thread. The frame as you have already done will be plenty. Only I would have your timbers on edge and not flat against the ply and include a couple of top cross supports. The fiberglass over the ply will strengthen the build immensely.
The outside layer of fiberglass is what will stop it from bowing vertically as it is under tension.(meaning it has to stretch for the tank to bow).
My build is 40" high and it has never shown any bowing whatsoever.
One thing I must point out is to not use silicones before you do any fiberglass work. Resins wont stick to silicone.(silicone will stick to resin though)
Round off every external corner perfectly and fillet every internal corner with bondo/bog. Resin mixed with talcom powder will suffice( Home made bondo). Making sure every corner is rounded perfectly will make fiberglassing around them much easier.

To be quite honest, if I was to build another at only 25" high. I wouldn't use any bracing at all. Just the top internal uero brace and cross supports as the fiberglass will take the pressure all day long. Hope this helps some and I look forward to seeing your end result. Good luck.

 

[john73738]

Sorry dude, missed the fiberglassing the entire tank. I take back what I said about the OSD, it will be fine with the fiberglass.

Looks good so far.

 

[gamerdemon]

Looking good so far!

 

[verruckt]

thanks for the info green, i would take the bracing out if i knew i could trust it. but its in there so i guess i might as well leave it. can never be to safe. altho it is gonna take up some room inside the tank. i have done siliconed the plywood, so i might as well leave the frame in there so i dont have to cut every bit of it out. would be such a pain. i will be adding top supports as soon as i get my glass. fixing to cut the hole for the glass in a second actually so will be posting pic of that in the next hr or so. build has slowed down a bit past day or so. got some bills to pay before continuing so im just doing little "freebies" here and there. i dont have to buy any bondo, i have some pirahna putty (a brand of spot putty, like bondo only smoother) i got a while back, should still be good. so the plan for today is a couple more screws here and there, veiwing window cut out, and some spot putty work. like i said, pics will be up later of the progress.

verruckt

 

[verruckt]

got that part done, 61" long and 21.5" tall. hands r still vibrating

the pirahna putty wasn't dry but wasn't wet enough to mix and spread so it got tossed. will have to go buy a small thing of bondo in a couple days. or maybe a medium size. depends on what i wanna do with it .

verruckt

 

[verruckt]

 

[verruckt]

umm ok? wtf the pic shows for me in the reply bar but won't post. ahh well. there is the link to it if u cn't see the pic itself

 

[pengu13]

I'm doing something similar. i used osb because it was free but my tank is 36" t x 84"L x 27"w my plan was to fiber glass it inside and out, then coat with pond armor. now that i made it this far i kinda do wish i put in some 2x4 bracing for safty little worried about the back bowing. i did put in some angel strips in all the corners that i covered woth bondo fine fiber fill. i'f you use bondo buy the gallon can i went threw 2 small ones could of used more, almost every thing i bought i should of bought more in bulk, like the glass and resin. the othere thing i found was make sure you get all the air bubbles out or they could burst under the presusre of the water. If i knew or had worked with fiberglass befor i could of saved my self some money and trips to the store

 

[Heathd]

Im not big on bondo, but if you are going to use a plastic filler for finishing work, use rage gold extreme or something similar. You are way less likely to get pinholes and other nussance effects that you get with bondo.

Also keep in mind that any amount of flex will cause the plastic filler to crack