A question on forces on a tank (joining two)

[Anonymous]

Yeah, I know physicist asking about forces, but its not so much not knowing the forces but I'm curious if anyone has an experience in the subject and might have some insight or helpful hints to what might go wrong.

Ok say I want to join two tanks together, they have the same "footprint" the side they are touching, as if both sides didn't have a side panel (imagine removing one side from two glass tanks, and butting them together). Now I realize all sides will feel a force outward, and since there's no "side" where the two tanks would be connected there's no balancing force in that direction, so the tanks most likely will have a netforce to either side away from the middle, and that the two halves would migrate from one another, opening up the seam (whether coated with silicone or whatever) and making disaster for anything dry around it.

Now the curious aspect is how much force an I expect? I'm guessing silicone on glass while yes it might be strong, won't be strong enough to hold the two pieces together (or is it?) I know the friction of all that weight on the stand probably will help negate a great amount of the force (how much though??), Would somehow joining the two outer "frames" together with a metal plate, or a strong epoxy resin be sufficient to hold the tanks together (and of course silicone over the seam). I'm hoping the stand they'll rest on is sufficiently rough enough to provide enough friction to prevent the tanks from sliding as much as possible, but this isn't exactly something I can experiment on a small scale (say a couple 10g tanks) and scale it upward, maybe put "teeth" into the bottom frame so as to dig into the tank stand and prevent the slippage.

Btw the two tank sizes in question a are 135 & 115g respectively.

 

[Anonymous]

I am completely stumped. Sorry.

Louey

 

[Anonymous]

I guess I don't understand the question. If the tanks are the same depth the pressure will be the same on all four ends. If you remove both ends and join the tanks, how will you structurally splice the fronts and backs together so they don't deform?

Why not cut a 4-6" opening in both ends and then push the tanks together with silicon between the two mated ends. You will keep structural integrity.

 

[Anonymous]

Fuzzicist ask this question a few months ago, I guess we did not discourged him enough to stay quiet...

It can be done with two acrylic tank. There is a half-yin-yang tank done with by jointing three panels of curved acrylic together, essentially the same type of joint you are talking about. However, for glass, it can only be siliconed together.

The main force that you need to worrry is the outward force perpendicular to the panel's surface. It is pretty much hydrostatic force (F=mgh). The easier way to deal with it is with a metal bracket on top (and bottom). You got to have something as strong/rigid as glass as if the jointed panels is one whole piece.

The secondary (weaker) force is the one that pulling the tanks apart. A bracket will handle it too.

 

[Anonymous]

hehe Seven, yeah I know I asked this some time ago, but those were with acrylic tanks, now I have a 6 foot long and a 5 foot long glass tank.

I'm curious is there any sort of epoxy that'll attach to glass? superglue? just a little something else I can put along the seams of both tanks that can add further strength.

The main force that you need to worrry is the outward force perpendicular to the panel's surface. It is pretty much hydrostatic force (F=mgh). The easier way to deal with it is with a metal bracket on top (and bottom). You got to have something as strong/rigid as glass as if the jointed panels is one whole piece.

Yeah I figured this was going to be the main issue, although both tanks have that glass top brace on both sides (as well as the larger one in the center), and I'm hoping this will suffice for strength reasons. Although putting a bracket will still be done, and maybe even something over the seam itself (if at the very least to hide the seam).

Glad to hear the force that would push the tanks apart isn't terribly large and I really don't need to worry about it.

Now if my cousin would get his stuff out of my basement I can start on building an 11 foot long stand

 

[Anonymous]

It is more doable with acrylic tank than a glass tank, IMO. But you will need to make sure the panels are sufficiently thick when they are jointed. I will definite consider using two part epoxy for this type of cementing.

Glass is more tricky since I don't know any epoxy that have the same refractive index as glass, able to bond to it, and sufficinet strong for this application.

 

[minibowmatt]

I think this *might* be able to be done. You may need to build a small frame that will go on the outside of the joint, so both panels are supported a bit. I do think that it would take considerable bracing, because now your talking about holding back a lot more water.
Personally, I wouldnt try it.

 

[Anonymous]

Ahhh, go for it. This biggest problem I can see is the bracing from front to back since in essence now you have a pane of glass 11 feet long (with one division) that has to hold back water. I am sure you know how to handle that.

Just my opinion, but I would try it with silicone first because it flexes. Gluing glass together with an relatively inflexible medium (epoxy) seems like asking for trouble to me. I believe that is one reason they use silicone in aquaria construction in the first place.

Test it.

Set it up in your garage/patio/outside and build a cheap 55 gallon surge device out of a fast pump (sump pump?) and a trash can and some three inch pipe. Surge it along the length as fast as the pump will go and see how the joint holds up. If you braced well from front to back, your only concern should be the forces trying to break the two tanks back apart again and the surging will stress that bond nicely. Check for leaks and then cut them apart, put them into place and silicone them up again. (Moving them while attached together would be asking for trouble IMHO) Should be no more difficult than fixing a broken tank. (twice if you want to test it)

 

[Anonymous]

Hmmm, well I'm not too worried about any refractive index since at the seam it will be visible, either the seam or the bracing I put around the seam.

I'm curious how much of this flexing occurs with water in a tank, I just measured the tanks and the width of my 135 with water in it, is 24 1/8" and the tank with no water in is only 24", hopefully that's some flex associated with the water pressure. But yeah, this isn't going to be done anywhere there is anything I care about damaging (my new fish room!) there's no real lower point other than the concrete subfloor, so might as well do it there (that way if it does work I don't need to separate it. I was planning on incorporating some braces into the stand itself to hopefully prevent the tanks from wanting to split. Only real issue I can see now is some flexing at the seam, eitherway I hope the tanks are the same size though, 18"w by 24" high is a standard height, but the empty one is 24" high including bracing, and mine is 25" high including bracing (which is both the same in either case). *sigh* Anyways, good stuff to know, it'll be a little while before I am able to set this up, I still need to set up my 100 acrylic as a temporary storage for the fish in the 135 before.

 

[Anonymous]

So there is no way for you to move a 11 foot glass panel into the fish room and have it built there in situ? Is it due to the size issue, cost, or some other problem?

I just feel that it is best not to do it with glass if you can use a single panel, and not have to deal with that ignoring bar in the middle of your tank.

 

[Anonymous]

Well, I wouldn't say there's no way to get an 11 foot long pane of glass. Infact my plan was to build a custom tank on site, but I have a 135 glass, and this other glass tank just fell into my lap (it cost me a few frags) so figured I might give this a go instead since the price was right. If this plan doesn't end up working, I can always replace the pane of glass I removed, and use them for sumps/refugium and build a tank.

The size of 11 feet just happens to be the combined length of both tanks and really didn't have my mind set at that size infact I have about 15 feet I could technical work with.. although manuvering a piece of glass (or acrylic) that size might be problematic, not to mention expensive as all hell.

 

[Anonymous]

So the main reason you are doing this is due to the available of recycleable, cheap parts?

Just a idea, how about building a steel frame, powder coat it, etc., and move it there as one whole welded piece, or have it made to be bolted together, then you just put the 7 pieces of glass panels on the frame, silicone them together, and you have a solid tank that should last for several year?

 

[Anonymous]

yes the main reason is the availablity of recyclable parts

Interesting idea for steel frame. That's basically what I want to incorporate into the stand. Problem is my welding skills are less than desirable (that and I don't have any welding equipment here!). I could do it out of wood though, and really wouldn't have to worry terribly much about coating the wood since all the wood would be external (ie I could get away with some non-reef safe water proofers), that and getting a 12 foot long piece of wood would not be too difficult (or that expensive) I could route out a groove in a 2x4 as a "lip" for the glass to rest on and if I have the 2x4 laying flat it should give plenty of strength outward, and I could probably do away with the glass bracing at the top and replace them with much smaller straps or something.

That definately could be a way to go, disassemble 2 perfectly good tanks to turn it into a larger tank.. I like it! Bonus here is if I wanted... I could also get some wider sidepanels (since 18" deep really isn't that good) and a 2' x 2' (or maybe even 3'??) piece of 1/2" glass isn't that pricy, along with a few extra pieces for the bottom ...

Uh oh.. I'm back in dreamer mode again.

 

[Anonymous]

Make a L instead of a rectangle - beef up the ins too :wink:

 

[Anonymous]

Hey now! lets not give me too many damn ideas! I might wander out into dreamer mode again!

Hmmmm

Although .... nah.. n/m
Bad andy!

I have room for 15 feet worth of tank in the room, and about 10 feet wide, but not wanting to deal with the humidity of a tank that size I think I'll settle for something a tad smaller.

Trust me I've run through a plethora of ideas involving large tanks, most of which were plywood based, but since I have glass now (pieces) I can ditch the idea of plywood, spend a few more bucks getting whatever extra piece I might need and just stay within the confines of what i have to work with.

 

[Anonymous]

Post pics.

 

[Anonymous]

Pics of what? My ideas? Or the final product? if its the latter you'll have to wait a bit.

 

[Anonymous]

Not if you get out of the sump and get busy.

 

[Anonymous]

Heheh, being in the sump isn't the limiting factor, my cousins crap from when he went to central america is still downstairs in my soon to be fish room! He recently found a place to move into, but I'm not holding my breath for him to move his crap out. I was planning on converting the room during my winterbreak. But cest la vie

 

[Anonymous]

>...Problem is my welding skills are less than desirable (that and I don't have any welding equipment here!).

I am sure you can find local steel fabricator that can build it to your specs. A 4X8X3 steel frame with powder coat was quoted for a few hundred dollars, so yours should not be that much more. With all the money you saved from these recycled glass panels, you could almost get a frame out of plated 18K gold or solid titanium