One last thing, the biggest weakness in terms of stress would be the corners. I would seriously consider a 2x4 frame on the outside reinforcing the corners. It probably would hold without it but I wouldnt want to be the one that finds out. If I can find it, I will post a pic of the 1100 gal plywood tank I built, it might give ya a few ideas
My Plywood Tank
- Thread starter marinelife
- Start date
I agree with the several suggestions of reinforcing the seams/corners... That is a carryover from the original design thread about plywood. Stugray was on the money with the pressure calculations... Imagine an acura pushing double walled plywood... the ply may not break, but the seams will feel it bigtime.
Maintenance will be a bear... you may have to design a whole new class of reef tools. Tongs are hard enough to use at 30"s... Now make that 80".
Maintenance will be a bear... you may have to design a whole new class of reef tools. Tongs are hard enough to use at 30"s... Now make that 80".
marinelife
Active member
Top access will be open with only a few support beams across.
I am planing at this time to have a closed loop pull from about 1 foot from the top and return the water in all 4 corner along the bottom. I will also have 4 streams at an angle pointing across the tank near the top.
At this time I can not do anything to the outside for reinforcing the corners. I will have my equipment cabinet on the one end and a book shelve on the other. What my happen is some metal supports will be added to the bottom on the outside.
I am planing at this time to have a closed loop pull from about 1 foot from the top and return the water in all 4 corner along the bottom. I will also have 4 streams at an angle pointing across the tank near the top.
At this time I can not do anything to the outside for reinforcing the corners. I will have my equipment cabinet on the one end and a book shelve on the other. What my happen is some metal supports will be added to the bottom on the outside.
marinelife
Active member
cmoresps - please post pictures
marinelife
Active member
Cool I will have a swap party 
Once it is finished and in I will see what I can do about having a gathering for anyone wanting to see it.
Once it is finished and in I will see what I can do about having a gathering for anyone wanting to see it.
You mentioned a clam shelf at the 70" depth. I dont think a 400w halide will have enough punch for a clam that deep.
I applaud your efforts, but if it were in my house, I'd build it out of steel or a lot more wood than you have.
Be sure to thin the first coat of epoxy so it soaks into the wood. Lots of people just paint it on and it peels off since it doesnt soak in.
Good luck. Cant wait to see it.
I applaud your efforts, but if it were in my house, I'd build it out of steel or a lot more wood than you have.
Be sure to thin the first coat of epoxy so it soaks into the wood. Lots of people just paint it on and it peels off since it doesnt soak in.
Good luck. Cant wait to see it.
marinelife
Active member
Hey,
The shelve will be at about 25-30" below the lights for the clams, they will not sit 70" down. No way would they live like you said.
The first layer will be fiberglass.
The tank is pretty solid right now, I think the wood will work out ok.
The shelve will be at about 25-30" below the lights for the clams, they will not sit 70" down. No way would they live like you said.
The first layer will be fiberglass.
The tank is pretty solid right now, I think the wood will work out ok.
SoFloReefer
New member
What kind of epoxy are you using?
stugray
Premium Member
"no need for 1000watters, I will live with the 400s"
I use 2 X 400W on my 125Gal less than 24" depth.
"the ply may not break, but the seams will feel it bigtime"
- Agreed
If you do not reinforce the bottom seam with some steel, then you are looking for trouble.
Imagine that your epoxy laminate "bag" ( made of fiberglass & epoxy ) inside the "box" ( made of plywood ) is a lot like a ziplock bag with water inside a shoebox.
Now your "Bag" Is glued to the inside of the box. It cannot move around.
As you raise the head height, the bag expands and trys to push out on the plywood Box. As the box changes shape, the "skin" of the bag will rupture due to the expansion and leak.
You need a very rigid structure ( steel frame ) or ANY failure of the box seam is catastrophic.
Stu
I use 2 X 400W on my 125Gal less than 24" depth.
"the ply may not break, but the seams will feel it bigtime"
- Agreed
If you do not reinforce the bottom seam with some steel, then you are looking for trouble.
Imagine that your epoxy laminate "bag" ( made of fiberglass & epoxy ) inside the "box" ( made of plywood ) is a lot like a ziplock bag with water inside a shoebox.
Now your "Bag" Is glued to the inside of the box. It cannot move around.
As you raise the head height, the bag expands and trys to push out on the plywood Box. As the box changes shape, the "skin" of the bag will rupture due to the expansion and leak.
You need a very rigid structure ( steel frame ) or ANY failure of the box seam is catastrophic.
Stu
marinelife
Active member
Most likely WEST SYSTEM epoxy or Sweetwater
marinelife
Active member
My current tank is 30 deep with 400s and that is about were the clams will be. 400W Mhs can go deep
The bottom seam is reinforced with wood triangles on the inside. What many successful plywood tank makers have done. A steal frame maybe needed, who knows I have not seen alot of plywood tanks reinforced with steal. Really I have not seen many tall tanks at all. Several have calculated everything up and say what I have will work. As I said before I may had some metal at the bottom. I have found several 90s at the store for roofing that I may add.
The bottom seam is reinforced with wood triangles on the inside. What many successful plywood tank makers have done. A steal frame maybe needed, who knows I have not seen alot of plywood tanks reinforced with steal. Really I have not seen many tall tanks at all. Several have calculated everything up and say what I have will work. As I said before I may had some metal at the bottom. I have found several 90s at the store for roofing that I may add.
el aguila
Member
Before I reply I want to make it clear that I have never built a plywood tank or worked with plywood/fiberglass; I am interested in building one in the future.
However in my youth I worked as a form carpenter on some tall concrete forms. There is tremendous lateral pressures while concrete is being placed. Especially at joints, which are typically reinforced on the exterior with extra lumber.
I've really never understood the idea of putting 2x2 cut on a 45 on the inside. The strength that you would achieve by placing them on the outside is considerably higher.
Anyway not to bash you "in my ignorance", rather than extra framing lumber/steel on the exterior, you may want to consider putting fiberglass sheets on the exterior of the tank. All of your pressure is going to be pushing to the outside for a blowout, especially at the bottom.
In my mind on this deep of a tank the fiberglass would provide more structual strength on the exterior.
Here again it would probably be nice if somone that has considerable experience working with some of the monster plywood tanks would chime in.
However in my youth I worked as a form carpenter on some tall concrete forms. There is tremendous lateral pressures while concrete is being placed. Especially at joints, which are typically reinforced on the exterior with extra lumber.
I've really never understood the idea of putting 2x2 cut on a 45 on the inside. The strength that you would achieve by placing them on the outside is considerably higher.
Anyway not to bash you "in my ignorance", rather than extra framing lumber/steel on the exterior, you may want to consider putting fiberglass sheets on the exterior of the tank. All of your pressure is going to be pushing to the outside for a blowout, especially at the bottom.
In my mind on this deep of a tank the fiberglass would provide more structual strength on the exterior.
Here again it would probably be nice if somone that has considerable experience working with some of the monster plywood tanks would chime in.
marinelife
Active member
Thanks for the reply. I take all post to heart and think about what is said in them.
I have been planning this tank for many months and designed the tank after talking with several different people. All of these people are tank builders and most of them have plywood tanks. Several of them have build large 1000+ gallon systems. Most have said no fiberglass is need with the 45s in the corner. I felt adding fiberglass inside was best just for my piece of mind and extra support it would give. It is very hard to find someone that has built a tank so tall let alone one out of plywood. I will be testing it in my garage for several months before it comes inside.
I have been planning this tank for many months and designed the tank after talking with several different people. All of these people are tank builders and most of them have plywood tanks. Several of them have build large 1000+ gallon systems. Most have said no fiberglass is need with the 45s in the corner. I felt adding fiberglass inside was best just for my piece of mind and extra support it would give. It is very hard to find someone that has built a tank so tall let alone one out of plywood. I will be testing it in my garage for several months before it comes inside.
marinelife
Active member
I also wanted to add to remember that is is going up against a wall so the back will have that to support it and the end both will have something else build onto them. The front is the only thing that will not.
Another argument that the seams will hold is that the wood glue manufacturers typically claim that the glue will hold 1200 to 3000 psi. Even if that is optimistic and we say that the seam can only hold 400 psi, one foot of seam is still strong enough to hold the entire tank, with water, hanging from the roof. So the seams are really strong. The idea that they can give in is probably wrong. There is a risk that the back may bend a little. My guess is it won't, but it is only a guess. But if you test it first as you say and see that it doesn't bend, then you'll be fine. If it bends, then placing 2 layers of fiberglassed epoxy on the outside of it will solve the problem.
My only concern is how you will glue the acrylic in place. I say this because I've seen a guy losing a $20000 tank because he couldn't get that seal water thight. He used MS-Polymer bases sealant. Here is a link to his site, text is in Norwegian unfortunately, but the pictures may be useful. Really sad because most stuff was top quality, it was only the mistake with the seal that ruined everyting. Remember that the sealer will most likely not function as a gasket between the glass and the epoxy. The water pressure is not large enough to squeeze it to be deformed.
Failed 1000 gallon project
My only concern is how you will glue the acrylic in place. I say this because I've seen a guy losing a $20000 tank because he couldn't get that seal water thight. He used MS-Polymer bases sealant. Here is a link to his site, text is in Norwegian unfortunately, but the pictures may be useful. Really sad because most stuff was top quality, it was only the mistake with the seal that ruined everyting. Remember that the sealer will most likely not function as a gasket between the glass and the epoxy. The water pressure is not large enough to squeeze it to be deformed.
Failed 1000 gallon project
He filled it in January 2005 and had big problems with leaks in the start. Then he managed to get it waterproof for awhile. But it started again and it was a constant struggle. He did all sorts of resealing for a whole year and then in the end he was so fed up that he decided to shut down the whole project. The last photo is the tank sawed in half yes.
What he should have done was to take out the windows, remove all the sealant and insert them with a new sealant that works with acrylics.
What he should have done was to take out the windows, remove all the sealant and insert them with a new sealant that works with acrylics.
tundra1000
New member
Thats a shame, it looked like a great project.
