Outer Limits 4x4 Board

I want to build some sill tanks to hold water under the cruiser. Off the shelf ones are $500 - $790 ea - ouch
I figure I can do it out of sheet stainless. Now I could steal the old mans baby tig and learn to weld stainless, but I'm worried about cracking, embrittlement etc. Also worried about the long runs warping the metal.

So, I thought, what about glue. If the edges were folded, and then joined with Sikaflex, I reckon this would have a massive strength hold over a 15mm overlap.

Has anyone seen anything like this?

Thanx
Paul

Maybe add a few stainless blind rivets to give the sika seal maximum compression.

Other than checking to make sure sikaflex is suitable for drinking water.

guzzla wrote:Maybe add a few stainless blind rivets to give the sika seal maximum compression.

Other than checking to make sure sikaflex is suitable for drinking water.

If sika is not suitable you could use silicone for aquariums as they don't leech chemicals out. The rivets should hold it together if you use enough of them LOL

why do u think LRA and others weld their tanks? why not do it right first time? no point finding out in a few klms you have no water left.

Blind pop rivets will do nicely. Seal before riveting. You wont have any problems.

I was concerned the rivets themselves might provide a leak path as opposed to a clamped join. Assuming you are talking about normal aluminium pop rivets.

Sikaflex Pro is drinking water safe.

Paul

http://www.roymech.co.uk/Useful_Tables/Rivets.html

You'll need sealed pop rivets.

if you use a sealant the corners and rivets are far more likely to leak than a properly welded tank.
with 18yrs in building, most metal roof or box gutter leaks ive seen will be at a failed sealant join or through rivets or poorly sealed corners.
you cant get inside the tank your talking about to make sure you seal every seam properly from the inside and oversealing on the outside is a piss poor way of sealing something.
Id also be concerned about sealants tainting your drinking water, might not harm you but sikaflex and others dont taste too good

80's_delirious wrote:if you use a sealant the corners and rivets are far more likely to leak than a properly welded tank.
with 18yrs in building, most metal roof or box gutter leaks ive seen will be at a failed sealant join or through rivets or poorly sealed corners.
you cant get inside the tank your talking about to make sure you seal every seam properly from the inside and oversealing on the outside is a piss poor way of sealing something.
Id also be concerned about sealants tainting your drinking water, might not harm you but sikaflex and others dont taste too good

of course you can get inside to seal the seams from inside. you can build it either with a separate lid that goes on last so all the other seams are fully cleaned and sealed from the inside, or build it with an inspection port in the top big enough to get an arm in to work and to hold a mirror to inspect all the seams before jamming a cover over the port with heaps of overlap and ploenty of sealant.

I would be more inclined to make it out of aluminium but I think that is largely a matter of personal preference. the only real issue I see is with brackets, if you don't want to weld, you'll have to use a strap system like a lot of fuel tanks, might be slightly complicated.

I think it's a great idea.

dumbdunce wrote:

80's_delirious wrote:if you use a sealant the corners and rivets are far more likely to leak than a properly welded tank.
with 18yrs in building, most metal roof or box gutter leaks ive seen will be at a failed sealant join or through rivets or poorly sealed corners.
you cant get inside the tank your talking about to make sure you seal every seam properly from the inside and oversealing on the outside is a piss poor way of sealing something.
Id also be concerned about sealants tainting your drinking water, might not harm you but sikaflex and others dont taste too good

of course you can get inside to seal the seams from inside. you can build it either with a separate lid that goes on last so all the other seams are fully cleaned and sealed from the inside, or build it with an inspection port in the top big enough to get an arm in to work and to hold a mirror to inspect all the seams before jamming a cover over the port with heaps of overlap and ploenty of sealant.

I would be more inclined to make it out of aluminium but I think that is largely a matter of personal preference. the only real issue I see is with brackets, if you don't want to weld, you'll have to use a strap system like a lot of fuel tanks, might be slightly complicated.

I think it's a great idea.

Lid was the plan. Hadn't thought of straps, I like that.
Aluminium has too many "maybe's" when it comes to water tanks and possible health effects. I'll skirt the argument and not use it.

Paul

sikaflex isnt toxic for drinking water, sealed pop rivets normally leak before normal blind rivets and do it and see.

itll hold water fine with roof and gutter silicone normally lasts for 5 years or so in sunlight so think of the life in a shady wet environment.

the only problem will be expansion contraction which will cause the silicone to seperate and crack etc. space the rivets about 40-50mm apart to keep it strong and stop the sheet rippling.

even better idea would be to get a fold put on it that will lock into itself sort of thing (like on round downpipes) and put rivets through that.

delerious. roofs only leak when shit people do them...... thats why they made proffessionals with ethics like me most roof leaks with silicone happen because alot of roofers thinks that a tiny amount of silicone will do.....the tubes arent expensive, just blow a few tubes on the thing and not think about it again. by doing a roper joint it will reduce the chances of leaking also.

ring a rainwater tank place and ask what sealant they use

I should note, i'm not just thinking sealant. Sikaflex is a hell of a lot stronger than silicon. The intent is for the adhesive to be structural, rivets would only be for clamping.

I mean it worked for the F1 Mclaren, Lotus, your windscreen and who knows what else these days.

Paul

me3@neuralfibre.com wrote:I should note, i'm not just thinking sealant. Sikaflex is a hell of a lot stronger than silicon. The intent is for the adhesive to be structural, rivets would only be for clamping.

I mean it worked for the F1 Mclaren, Lotus, your windscreen and who knows what else these days.

Paul

I would not rivet, sika alone is strong and will be more watertight without having holes drilled through it. if you are thinking about a box + lid design, you can clamp the corners of the box until the sealant sets, and if you design the 'box' section with an internal flange at the top, so that the lid glues down on the top of the flange, you can clamp that one too.

if you have access to a panbrake or bender, you should be able to make very accurate folds so the box is 80% waterproof with no sealant at all, so you have to force the seams apart to actually ooze the sealant in there, then lightly clamp it up. the bottom, sides and top flange are all easily developed from a single sheet.

me3@neuralfibre.com wrote:I want to build some sill tanks to hold water under the cruiser. Off the shelf ones are $500 - $790 ea - ouch
I figure I can do it out of sheet stainless. Now I could steal the old mans baby tig and learn to weld stainless, but I'm worried about cracking, embrittlement etc.

do you have some welding experience? get some scrap stainless and experiment. a large part of the work is in folding up the sheet metal

me3@neuralfibre.com wrote:Also worried about the long runs warping the metal.

long runs can be welded with a series of stitches to help reduce warping

me3@neuralfibre.com wrote:So, I thought, what about glue. If the edges were folded, and then joined with Sikaflex, I reckon this would have a massive strength hold over a 15mm overlap.

Has anyone seen anything like this?

I had a fish tank that held 300litres, was made from 6mm glass butt jointed together with silicone with 2mm silicone join between the glass panels.

if you clean mating surfaces thoroughly and can clamp the folded seams effectively maybe ok.
Ive spent years doing metal roofing, lots of it was fixing other peoples shoddy work (I have ethics too). lots of sumps and box gutters leak due to flat sheet metal moving through expansion and contraction pulling riveted and silicone/sikaflex sealed joints apart. this is much more of a problem with stainless steel compared to mild steel. rivets are a common source for a leak

a tank under a 4by is probably not going to cop the same temperature extremes as a metal roof (ive been on roofs in sydney with 10mm layer of ice in winter and well over 40 degrees in summer), though could have more movement/flex/vibration to pull it apart.

another thing to think about is how it will stand up to being dragged over rocks. better or worse than a welded tank?? I dont know

Im not saying it wont work, sikaflex is awesome stuff (100x better than silicone IMHO)
I just think for the work involved Id spend the time to weld it.[/quote]

sika comes in different grades, strength with not as much sealer to pure sealer only good for gutters and shit with no stress. just remember it isnt meant to stretch at all. the company recomend a 20% stretch rate...... 20% of 1mm per metre. remember that when thinking about mounting etc. id still fold a seam on 2 sides to joins it up together and like lock it into place sort of thing. even use some tech screws with rubber washers.