Hybrid Low-Iron & Acrylic Tank?
 

I am trying to determine the feasibility of building a large hybrid acrylic tank with a low-iron (Starfire) viewing pane. My idea is essentially to build the tank from acrylic with a sort of a bracing style front and set low-iron glass into the tank for viewing.

My reasoning behind this is that because I live in an earthquake area, it would be inordinately risky to have a full-blown glass tank, but I feel that with most of the structure being acrylic, it would be stout enough that inserting a glass front may work, and help me keep the glass clean. I have had a horrible time with the viewing pane on my tank because for some odd reason, my tank grows coraline like there is no tomorrow. It is so thick and fast growing that in many areas it is peeling off and exposing fresh new coraline under it, much like when a sunburn peels.

Anyone have any experience with this or insight as to how this could be accomplished? My current tank's overall dimensions are 96l x 60d x 35h.

dosent AGE make glass tanks with acrylic braces? i would think they would be the ones to call about this because they seem to have the most knowledge in the field of bonding 2 different things. id love to see it done especially in your 1000 gal

there is a couple of ways to skin that cat. the one way that comes to mind is to use a steel frame work made from angle ironthat sorunds the entire outside of the tank. if you used rino lining to cover the steel and then glued in the pannels with dow corning 795 silicone it would seal the tank completly. dow corning 795 will stick to acrylic and to glass with out loosing its bond like regular silicone. the big problem is you haveto let the silicone sit for 2 months to completly dry. its a very slow process and is not a good way to mass produce tanks. that is why no one uses dow corning 795 to put tanks together. threr is also a urethane glue that can be used that will bond to acrylic and glass at the same time. the frame work would be unsightly in some ways but in others it would be awesome becasue it would leave the top open. if you used steel round rods for cross bracing it would be alot les intrusive than an acrylic top woluld be. im planing on building a tank that is 5 ft x 3 ft x 24" tall and it will have a steel rimmed top on it. the rest of the tank will be acrylic that is glued together the old fasion way. this will reduce the problems with acrylic tops that get in the way of equiptment placment.

you would need to make sure that all the steel is covered with the rino lining to seal it completly from the salt water. the seams in the tank would be sealed with the dow corning 795.

this would make the tank alot more shock proof to tremmors becasue all the seals would be pressure seals. the higher the pressure the harder the seal woud be. the only down fall is that frame would be covering the corners and would be lass apealing to view. this design would work well for an inwall tank that is not viewed from more than 1 side. or if you viewed it on 3 sides you would want to cover the steel with wood trim.
the steel would make the seams rigid and the DC795 would make the seal.

That's interesting and thank you for your post Scott. I understand what you are saying, and have no problem waiting 2 months for it to cure. My tank is in-wall and I have no problem with the strapping as I hide all edges behind the wall anyway.

But would I really need the 795 all the way around?

Wouldn't it be better to build the tank out of acrylic with an open front like a euro-brace, and then use 795 to bond the glass pane to the bracing from the inside? My current tank has the top and bottom 3" and 6" of each end hidden behind the wall.

About the Rhino lining: It has been my impression that it does not coat very evenly. That it would be somewhat lumpy and therefore create pressure points. Am I getting that wrong? I read one thread where a guy had his stand coated with it, and then it created pressure points and they had to shim it all over the place.

Couldn't 316 be used just as well, or a good quality powder coat?

i have worked on a tank that was ringed with steel around the top. it was rhino lined, and the rhino lining was pretty good in my mind.
if you made the tank in the normal fation and then framed it in steel the problem would be making the frame work so it can be bolted together instead of welding it together. it can be done but not very easy.
the other way would be to make a very expensive bolted flange made from acrylic on the front of the tank and then installing the glass inbetween the acrylic flange. you would need to use a rubber gasket on the outside and then use DC 795 on the inside to make sure it sealed properly. this would allow the glass to floatin the gasketed flange. it would be expensive to make this because of the design but it not out of the question either. if you cnc cut the pieces and then laminated them together it would make the flange cheaper but it still would be time consuming.

hmmmm...another good idea. I got ya on the frame...it couldn't be welded if there was acrylic already in it, and it would be nearly impossible to place the pieces inside the metal frame and then bond the acrylic.

I had originally envisioned the viewing pane with acrylic slots bottom and sides with the glass slid down inside and then the top piece installed.

[QUOTE][i]<a href=showthread.php?s=&postid=11487835#post11487835 target=_blank>Originally posted</a> by spazz [/i]
[B].....dow corning 795 will stick to acrylic and to glass with out loosing its bond like regular silicone. the big problem is you haveto let the silicone sit for 2 months to completly dry.....[/B][/QUOTE]
Spazz, I believe the full cure time is 14-21 days and not 60.

[QUOTE][i]<a href=showthread.php?s=&postid=11488459#post11488459 target=_blank>Originally posted</a> by jnarowe [/i]
[B]
I had originally envisioned the viewing pane with acrylic slots bottom and sides with the glass slid down inside and then the top piece installed. [/B][/QUOTE]
the big problem ther is the thicknes sof the acrylic you would haveto use. then there is the way of sealing it with silicone or some sort of gasketing material. not an easy task.
if you used 1" thick actylic and cut pieces out of the sheet on a cnc router to fit together like a jig saw puzzle and the used slovent cement to glue the frames together it would save on the cost of acrylic and would make both the inside and outside frames. but he milling would need to be perfect and the problem there is that acrylic is very uneven in its thickenss. i have had a sheet of polycast brand acrylic. the thickness in the middle of the sheet was .510 and the thickness on the outsides was .450
so that would make it alot tougher to build the front frame work like a jig saw puzzle. but it can be done.

[QUOTE][i]<a href=showthread.php?s=&postid=11488490#post11488490 target=_blank>Originally posted</a> by GuySmilie [/i]
[B]Spazz, I believe the full cure time is 14-21 days and not 60. [/B][/QUOTE]
on standard silicone it is 12-14 days. but the dow corning 795 is a totaly dfferetn type of silicone. bill wann used it on his big tank to seal upthe acrylic to the concrete. after 3 weeks it was still soft and you could stick your finger in it and it was not set up. it takes a minimum of 30 days to cure but bill let it sit for 2 months to make sure it was solid.

Of course curing depends on temp and relative humidity but he 14-21 day spec is from the Dow 975 spec sheet.

I was using it once for a building maintenance project so I happen to have the spec sheet for it. Before getting some for that project, I was not aware that it was so good for use with plastics.
Still, 2-3 weeks is a long time for us impulsive types :D

[QUOTE][i]<a href=showthread.php?s=&postid=11488851#post11488851 target=_blank>Originally posted</a> by GuySmilie [/i]
[B]Of course curing depends on temp and relative humidity but he 14-21 day spec is from the Dow 975 spec sheet.

I was using it once for a building maintenance project so I happen to have the spec sheet for it. Before getting some for that project, I was not aware that it was so good for use with plastics.
Still, 2-3 weeks is a long time for us impulsive types :D [/B][/QUOTE]
bill had to fill in a 2" wide rebate with that silicone. he called the manufactureto see wht they had to say about it. they told him the thicker the application the longer it takes to cure. im not sure how thick you had your silicone but bills is about a 2" x 2" sealing area that had to cure. in a situation where it has to hold water i would want it to cure fully so i would wait a long time to put any pressure on it.

has anyone had any experience with the marine sealant 5200? i have not used it on tanks as of yet but i have on boats numerous times, and it is the stickiest, messiest stuff around with about a 1 week cure time. Once it is set though, the bond strength is ridiculous. 700psi adhesion with 1350% elongations before breaking. whatever you stick together with this stuff never comes apart, even on deep water ocean faring boats (where i have my experience with it) that get pounded left and right.

we once used some to seal a transom at the motor mount. 5 years later when we went to change the motor we unbolted everything and started lifting with the motor winch. it the motor was not lifting off the transom so we got a knife in there to try to cut some of the sealant. tried lifting the motor again with no success, we were actually lifting the entire boat off the trailer by the motor this stuff bonded so well. when the motor finally broke loose from the transom the 5200 never came apart, but actually separated the gel coat from the fiberglass!!! that is some serious bonding.

[url]http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtMXfXnXfXEVuQEcuZgVs6EVs6E666666--[/url]

My dad knows a lot about glazing and is going to post a sketchup of a suggestion later today.

I've used 5200 on a concrete tank with large acrylic panels. IIRC, the original seal was 795.

We had to reseal the tank due to Urchins eating the sealant. (My buddy at Long Beach, said he's had to reseal tanks due to the Naso tangs eating it too)

We had 316SS anchor bolts holding the acrylic in since it was a frameless top and the span was pretty long, for the thickness of the acrylic.

We gooped it all up with 5200, retightened the bolts, and gooped the nuts with more 5200. Worked great. I remembered being worried about the 5200, whether it was safe or not (chemical leaching). But the tank was 4000 gallons, and it was never an issue.

I have used gallons of 795. You HAVE to use it by its expiration date or it is useless (will NOT cure). Toss it out if its even close to the date on the tube.

Scott,
I noticed on Bills tank that he only put silicone between the rebate and the acrylic face. I think I would have added a fat bead all around afterward- between the edge of the acrylic and the face of the concrete. Do you know if he used acetone or something to clean the epoxy before sealing? The epoxy cures with a wax skin that must be removed (general info here, Bill obviously knows this:) ) before adhering the glass.

Not sure where he's at with the project, but it'd be nice to see some pics sometime, with no prying into the mans life.

[QUOTE][i]<a href=showthread.php?s=&postid=11490182#post11490182 target=_blank>Originally posted</a> by H20ENG [/i]
[B]
Scott,
I noticed on Bills tank that he only put silicone between the rebate and the acrylic face. I think I would have added a fat bead all around afterward- between the edge of the acrylic and the face of the concrete. Do you know if he used acetone or something to clean the epoxy before sealing? The epoxy cures with a wax skin that must be removed (general info here, Bill obviously knows this:) ) before adhering the glass.

Not sure where he's at with the project, but it'd be nice to see some pics sometime, with no prying into the mans life. [/B][/QUOTE]
he used 2 different things in the rebates for the tank. the fist thing was rubber blocks to cusshion the acrylic from rubbing against the concrete. the next was backer rod and then the 795. he called the factroy and got the exact specs on how to apply it to his tank. im not sure what cleaning methoid he used but i will say you will never remove those pannels from the tank ever again. you would have to cut them out with a saw.

as for pictures im not sure what is going on there yet. im sure there will be a site that has his pictures with some brief discriptions in there with no way for people to make comments jst a digital time line of photos. you migt wo wait to see it in a book. there is talk of it being in one of the more well known authors books on how to build big tanks.

[QUOTE][i]<a href=showthread.php?s=&postid=11490076#post11490076 target=_blank>Originally posted</a> by matt_54351 [/i]
[B]has anyone had any experience with the marine sealant 5200?
[/B][/QUOTE]

yes this is the other sealant that would be recomend for this application. i just couldnt remember the name of it off the top of my head. this will bond to glass and some plastics with an extreamly high bond. now what plastics it will bond to is not known. testing would be needed to determin the bond strenght with acrylic. its not hard to do a little testing with weights and scales to determin what the bond strength is to acrylic. the other material it is bonded to does not matter becasue i do know it will bond to glass with a very good bond strength.
this is a ureathane sealant if i remember right. it has been around for years.

5200 is not a magic bullet either. I have used it for most of my life, and it can be a great seal, but I have seen it fail too. I am not real sure about how well it would adhere to glass, but the damn stuff is sticky as can be.

Regardless, my thought was to create an acrylic slot for the starfire that is 2" larger on all dimensions, fill the bottom with the appropriate sealant, and lower in the glass. I would hold the glass with pneumatic suction cups so that it hangs just below the contact point, and then fill the sides with sealant. Allow that to cure while hanging and when it was cured, I would release the suction cups, fill the top with sealant, and mount the acrylic top.

[b]Redstratplayer:[/b] I would be very interested to see how a glazer would approach this project! :)

Thank you all for posting. I really appreciate the flow of ideas!

i was thinking something along the lines of this for a glass acrylic high breed tank.
[IMG]http://i22.photobucket.com/albums/b308/spazz129/acrylic%20stuff/acrylictoglass.jpg[/IMG]

Yeah, that is what I meant by a front with bracing...having an acrylic edge to bond to.

Maybe I am making it more complicated by adding the block behind the glass to form a "slot", but it seems to me that would be significantly more stable, particularly if the tank had to be shipped.

It sounds to me like you guys think this could be done. Scott, can you describe the method to test the 5200 bond? I have plenty of acrylic & 5200 to try it out.

The real question to be answered is, will this still be stable in an earthquake, and how diminished is the risk of failure in comparisson with an all glass tank? In other words, is it worth the effort?

I would glue 2 edges together, stick one in a vise, then clamp a bucket to the other piece, with a fish scale between them. Slowly fill it with sand or water to add weight and see what the shear strength is.

Crude but will demonstrate the effect.

Try several samples with different prep styles too. Sand 2 pieces with 120Grit, and leave 2 with saw cut edges, clean it with alcohol so it will stick well.

[QUOTE][i]<a href=showthread.php?s=&postid=11490882#post11490882 target=_blank>Originally posted</a> by jnarowe [/i]
[B]....Maybe I am making it more complicated by adding the block behind the glass to form a "slot", but it seems to me that would be significantly more stable, particularly if the tank had to be shipped.....[/B][/QUOTE]

A block behind the glass may or may not help for shipping, but if done the way shown in Spazz's drawing above, that front glass ain't going anywhere, once there is water pressure against it.

Of course the bottom edge would need the same treatment as the sides. Upper cross bracing (for the glass) would depend on the engineering limitations of its expanse and thickness vs load.

[QUOTE][i]<a href=showthread.php?s=&postid=11490942#post11490942 target=_blank>Originally posted</a> by H20ENG [/i]
[B]I would glue 2 edges together, stick one in a vise, then clamp a bucket to the other piece, with a fish scale between them. Slowly fill it with sand or water to add weight and see what the shear strength is.

Crude but will demonstrate the effect.

Try several samples with different prep styles too. Sand 2 pieces with 120Grit, and leave 2 with saw cut edges, clean it with alcohol so it will stick well. [/B][/QUOTE]
this is pretty much waht my thoughts were. if you apply a steady pressure to the seam to see what its long term strength is you can really tell if it will hold or not. you can calculate the psi that will be applied to the seam. then you should just double that number, and then apply it to the square surface area that will be bonded. if you make 2 test pieces that are 1 sq inch and then 2 square inches to see what he difference is in bond strength. it will be more with the 2 sq.in. of surface area but it might not be double. you will need a scale that is bigger than a fish scale but not much bigger. you can always use a digital scale to measure the weight inthe pail and the hook it on the edge of the acrylic .then leave it there for a week and see how far it streched out. if there is too much strech its not going to work. you cant have alot of strech or it will cause the acrylic to bow out on the sides.


if you have the single block like i have in the picture it will be alot easier to install. it will also be alot easier to clean up once the glass is set. the nice thing about this design is the glass will float some what in the frame becasue of the elasticity of the 795 or 5200 the glass will be protected from major shock. its like a rubber cusion in there. also the pressure of the water against the glass will increase the pressure on the seal so it wont leak.

OK guys. I am going to try this in January. I am not sure of the properties of starfire are different from regular glass, so I guess I would have to get a couple pieces of it to try.

My 225 gallon in wall is acrylic with a starfire front. I'll take some photos of the metal strapping that was used on it this weekend. I don't know what type of sealant they used between the acrylic and starfire though.

Joyce

Sweet Joyce! Can you post who made it as well? I am extremely interested in seeing what you have. Thanks!