henward Posted October 16, 2012 Report Share Posted October 16, 2012 or can i do 2 pieces they come in 2400 x 1200 i am thinking of doing 1500 x 1200 (2 sheets) Quote Link to comment Share on other sites More sharing options...
henward Posted October 16, 2012 Author Report Share Posted October 16, 2012 can i use MDF? i am thinking 12mm thick as i will be putting another 15mm of poly on top Quote Link to comment Share on other sites More sharing options...
F15hguy Posted October 16, 2012 Report Share Posted October 16, 2012 I'd avoid MDF as it may swell if it gets wet and crack your tank. I don't see a problem using 2 sheets as long as there is poly on top and you try and get the 2 sheets level. Quote Link to comment Share on other sites More sharing options...
henward Posted October 16, 2012 Author Report Share Posted October 16, 2012 I am told, really, i need the following 1) both sides machined 2) treated or marine ply but to get both sides machined, only marine ply is available I guess ill be getting marine ply! Quote Link to comment Share on other sites More sharing options...
henward Posted October 16, 2012 Author Report Share Posted October 16, 2012 what does everyone think of 12mm marine ply with 15mm poly on top? Quote Link to comment Share on other sites More sharing options...
smidey Posted October 16, 2012 Report Share Posted October 16, 2012 marine ply isn't treated, it has special hot type glue so it can be steamed and curved and is intended to be glassed over. treated ply is treated. as long as the stand is good enough the ply is not going to be doing anything apart from stopping the poly sagging. I used particle board on my stand. Quote Link to comment Share on other sites More sharing options...
smidey Posted October 16, 2012 Report Share Posted October 16, 2012 two pieces will be fine, the stand should be holding the weight not the ply. Quote Link to comment Share on other sites More sharing options...
henward Posted October 16, 2012 Author Report Share Posted October 16, 2012 So you think i should just put a 15mm poly under the tnak? I can even go 20mm poly.... would marine ply serve no purpose under the poly? feedback anyone? lfs said that i really should have ply then poly for maximum buffer and safety Quote Link to comment Share on other sites More sharing options...
Bishop Posted October 16, 2012 Report Share Posted October 16, 2012 Sounds expensive . I know you have done this before so probably not telling you anything new, but make sure that ply goes down super level middle and at each end. even 12 mm ply can bend so a 2mm difference will put some real stress on your tank. Especially at that length. Sounds like a fun project though. Quote Link to comment Share on other sites More sharing options...
smidey Posted October 16, 2012 Report Share Posted October 16, 2012 i would put a sheet on the top of the stand but it's not really critical what you use IMO. It will provide bracing for the stand which is useful for timber stands but i expect your going steel. I will hold up the poly so again i think you should put a sheet of something under the poly. I used 12mm particle board and two layers of 10mm poly on my stand. Sounds expensive . I know you have done this before so probably not telling you anything new, but make sure that ply goes down super level middle and at each end. even 12 mm ply can bend so a 2mm difference will put some real stress on your tank. Especially at that length. As long as your stand is flat the weight of the tank will flatten out the sheet, just make sure nothing is between the sheet and the stand so it can. Quote Link to comment Share on other sites More sharing options...
henward Posted October 16, 2012 Author Report Share Posted October 16, 2012 yes, i wont glue the ply, i will just place it on top. this will make sure that when it flattens, it can 'move' with the weight. then the poly too. thats what i thought, using it to not nly rest the poly on but to disperse more kinks and weights. the stand , presumably will be of high standard seeing its made by a reputable lfs. but yeah, its all bout safety. the base of my tank will be a total of 20 to 25mm glass. I am going for a 'braceless' bottom. soi willo have the base as 15mm glass, then another whole sheet to go on top of that to act as one giant bracing and slide that into the tank, this will give the look of no bracing but achieve the same if not more as bracing, also, this gives the bottom pane much more structural strength. so i am assuming that the tank mater will use 10mm to 12mm braching strips at the bottom. so i will use an entire sheet to brace the entire surface of the bottom (if that makes sense) suffice to say, this tank aint moving anywhere, heavy and strong base. but, safety is safety, the tank will eventually house thousands of dollars with of fish. no risks will be taiken i guess. PARTICLE BOARD: from what im thinking, someone said particle board will absorbe water and swell. but how will that break the tank. cos of the weight of the tank, the particle board will never push the tank up, all it will do is let the water absorbe futher into the board instead of one corner. does that make sense? should i use MDF? cheap, light. similar to particle board. Quote Link to comment Share on other sites More sharing options...
Bishop Posted October 16, 2012 Report Share Posted October 16, 2012 As long as your stand is flat the weight of the tank will flatten out the sheet, just make sure nothing is between the sheet and the stand so it can. I meant if the stand is 2mm higher in the middle than at each end and then the ply goes down over that. There is no way the tank can flatten that our as the ply has nowhere to go. Just heaps of stress at each end. Anyway regardless, if it's a steel stand, as you say I doubt it will matter what you lay on top of it, it will just be there to support the poly. Edit: I see what you are doing now. MDF should be fine I reckon, with a layer of poly and the weight of the tank I doubt you will run into issues, could undercoat the MDF if you wanted that extra level of being safe in your mind. Quote Link to comment Share on other sites More sharing options...
smidey Posted October 16, 2012 Report Share Posted October 16, 2012 PARTICLE BOARD: from what im thinking, someone said particle board will absorbe water and swell. but how will that break the tank. cos of the weight of the tank, the particle board will never push the tank up, all it will do is let the water absorbe futher into the board instead of one corner. does that make sense? should i use MDF? cheap, light. similar to particle board. use particle board before MDF. particle board is porous which means it will soak it up but will also release it, it will swell but will reduce when it dries out. It won't go back to flat but it will reduce. It is stronger than MDF due to the particles being glued together in a random pattern unlike MDF which is a layered product so it has a grain and will curve and hold its shape. MDF will absorb water like particle board but retain it, go fluffy and start to break down so particle board is the best option of the two. Ply will perform the best with regard to swelling/rotting etc but i think is overkill, my particle board has been under my tank for what must be a couple of years now and ther'es no swelling i can see and plenty of water gets spread around when doing what changes or chasing trophs with a net. i spent 8 or 9 years in the kitchen industry and around 5 years of that designing and making kitchens for Housing New Zealand houses, i have seen which works best for abuse and for water damage. Quote Link to comment Share on other sites More sharing options...
henward Posted October 16, 2012 Author Report Share Posted October 16, 2012 i guess i have to see hwo much particle board is vs ply. i got quoted for this piece (3000 x 1200 - 12mm marine ply machined both sides) $245 shipped to my house and cut to size. Ill see what particle board will be. the end of the day, this tank is gonna sit there for AGES. it will see minimal catching of fish. lids will be designed so even if the fish splash, water wotn leak front and back. particle board may be a winner if its much cheaper. Quote Link to comment Share on other sites More sharing options...
smidey Posted October 16, 2012 Report Share Posted October 16, 2012 particle board should be a similar price to MDF for a good sheet. Approach a kitchen manufacturer, they may have a packing sheet which could be free. Quote Link to comment Share on other sites More sharing options...
smidey Posted October 16, 2012 Report Share Posted October 16, 2012 i used a packing sheet for mine, cost me $15 i think and that was just to cut it to size. Quote Link to comment Share on other sites More sharing options...
henward Posted October 16, 2012 Author Report Share Posted October 16, 2012 particle board is half price. they can cut it to size too. Quote Link to comment Share on other sites More sharing options...
David R Posted October 16, 2012 Report Share Posted October 16, 2012 The ply is thinner than the glass you'll be using, don't waste your money. I wouldn't use MDF/particle board either, unless its really well sealed. Even then it might suffer from the moisture if you're going to have sump etc under the tank and have the stand closed in. Do9n't much around, you're spending too much time and money and love on this tank, the difference between a piece of 21mm H3 CD ply vs the piece of mind you get is money well spent IMO. Quote Link to comment Share on other sites More sharing options...
Hamstar99 Posted October 16, 2012 Report Share Posted October 16, 2012 Can you use 20mm partilcle board? Use a flooring sheet. It'll handle the moisture and comes in 3.6m long. About $100 a sheet. Quote Link to comment Share on other sites More sharing options...
Warren Posted October 16, 2012 Report Share Posted October 16, 2012 Any sheet of wood you put under the tank will do almost nothing to distribute the weight. The glass deflection on the thickness you're planning will be minimal. If you put the same force distributed on 20mm of flat wood panel it will deflect much more than the glass therefore will supply no extra supporting strength. I wouldn't trust most of the stands I've seen in a fish shop. They're often made without any stress calculation and will collapse in an earthquake easily. If it's a steel frame then most of the force will be taken up by the tank with the highest pressure points where the legs join the rest of the frame. Unless the steel members directly under the tank are very wide they will also deflect more than than the glass and not support nearly as much of the tank as you might think. If you were to use 150 x 50 x 6 RHS under the tank and support that with a leg every 600mm then the steel will give good support as there will be almost no deflection between the legs. Quote Link to comment Share on other sites More sharing options...
smidey Posted October 16, 2012 Report Share Posted October 16, 2012 Can you use 20mm partilcle board? Use a flooring sheet. It'll handle the moisture and comes in 3.6m long. About $100 a sheet. that's a waste of time and money as it simply won't support any better than a thinner sheet as the sheet on the stand isn't doing the supporting, the stand is. It also won't handle the moisture any better because its a flooring sheet, most plans are specified to be treated ply to wet areas for particle board floors. Quote Link to comment Share on other sites More sharing options...
Hamstar99 Posted October 16, 2012 Report Share Posted October 16, 2012 that's a waste of time and money as it simply won't support any better than a thinner sheet as the sheet on the stand isn't doing the supporting, the stand is. It also won't handle the moisture any better because its a flooring sheet, most plans are specified to be treated ply to wet areas for particle board floors. Just chucking an option out there for a full length sheet if he wanted to go that way. Didnt say use it or else. A flooring sheet will handle the moisture far better than a standard particle board sheets or packing sheets due to the resins they use, as they can handle being in the weather for a couple of months. Have you ever seen floors done in the 70s and 80s done out of standard particle board? Quote Link to comment Share on other sites More sharing options...
alanmin4304 Posted October 16, 2012 Report Share Posted October 16, 2012 Flooring sheets have a wax coating to protect from rain until the roof goes on. They are not waterproof. Getting a steel stand built accurately by someone who knows what they are doing is the way to go. Quote Link to comment Share on other sites More sharing options...
smidey Posted October 16, 2012 Report Share Posted October 16, 2012 Just chucking an option out there for a full length sheet if he wanted to go that way. Didnt say use it or else. A flooring sheet will handle the moisture far better than a standard particle board sheets or packing sheets due to the resins they use, as they can handle being in the weather for a couple of months. Have you ever seen floors done in the 70s and 80s done out of standard particle board? how do you think they make 12mm particle board? the same way they make 20mm so again no advantage in using flooring over any other particle board. Quote Link to comment Share on other sites More sharing options...
henward Posted October 16, 2012 Author Report Share Posted October 16, 2012 Any sheet of wood you put under the tank will do almost nothing to distribute the weight. The glass deflection on the thickness you're planning will be minimal. If you put the same force distributed on 20mm of flat wood panel it will deflect much more than the glass therefore will supply no extra supporting strength. I wouldn't trust most of the stands I've seen in a fish shop. They're often made without any stress calculation and will collapse in an earthquake easily. If it's a steel frame then most of the force will be taken up by the tank with the highest pressure points where the legs join the rest of the frame. Unless the steel members directly under the tank are very wide they will also deflect more than than the glass and not support nearly as much of the tank as you might think. If you were to use 150 x 50 x 6 RHS under the tank and support that with a leg every 600mm then the steel will give good support as there will be almost no deflection between the legs. Hi Warren, The stand i am looking at is 50 square tube steel stand. It is quite hefty. BUt i would like to you to elaborate on your comment above, sorry just having a hard time fully digesting it. so what are you suggesting? do you suggest, that i dont bother with the wood, just use poly bu tinstead, get the stand maker to make the gaps on the top of the stand ever 60cms? there is a supporting bar? is that better? deflection term you used, confuses me a little. could you elaborate :thup: I guess the question here is as well. there are 2 companies quoting me, lfs and an engineering place (rex engineering) who made my last stand. good work they did too. the engineering place, precision is key to them, i also stress that the stand has gotta be almost perfect in its levelness. the lfs one, they go through someone i dont know who but they go through these guys for all their stands. let me know your thoughts. if i can skip the ply and go for a 20 or even 25 mm poly to sit the tank on. the stand can have lots of support along the top to support the base of the tank. i can have heaps of support if needed, even ever 30 cms! cos the pipes will not come from the bottom of the tank. Quote Link to comment Share on other sites More sharing options...
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