Aluminum tank construction

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I am a noob at MIG welding aluminum but I am about to fab up a tank and have some questions for the experts.  I have a few criteria that I need to follow, so I'll give you the down and dirty. I am making a 125 gallon tank (livewell) that must me under 100lbs, and must be robust. I am planning on going with 11 gauge (0.090) but I am afraid that thin of material won't be to forgiving for a novice MIG welder like me. I have TIG'd aluminum many moons ago though. I plan on going with 3003 because the corners will be bent. What do you guys think, to thin, unreal expectations?Ok here are a few questions also, I have gotten a few prices on "11 gauge" material through my local welding shops and the prices have varied anything for $125-$175 a sheet. I didn't think much about it until I saw the gauge thickness charts on here......those numbers are for STEEL not aluminum. 11 gauge aluminum is .090 but steel is 1/8", BIG difference. I referenced back to my prices and I got to wondering if some of the welding shops assumed I meant 11 gauge steel equivalent instead of .090AL. Also in my haste I didn’t ask if they were quoting me 3003 and not 6061 which I will assume they weren't. Is it "best practice" to assume 11 gauge is referenced as .125 for all materials?Allen
Reply:In the welding/fabrication world, never assume anything.  Call back with more specifics to get the correct pricing.
Reply:I'd like to hear more about this live well. Size (I know 125 gal. L X W X H ?), how is it going to be used, going in a boat? Stuff like that. I work in the marine industry and am curious.You didn't mention how big of a sheet of alum.. I'm paying (in South Carolina)$190.00 for 6061  .125 X 4' X 10'If I knew that I was going to live this long, I would have taken better care of myself
Reply:Originally Posted by Happy BobI'd like to hear more about this live well. Size (I know 125 gal. L X W X H ?), how is it going to be used, going in a boat? Stuff like that. I work in the marine industry and am curious.You didn't mention how big of a sheet of alum.. I'm paying (in South Carolina)$190.00 for 6061  .125 X 4' X 10'
Reply:It should work. 3003, or 5052 will be good choices. Both are easily formed with a good brake, and weld nicely. I was paying $270 for a sheet of .125, 5052. 4ftx12ft.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Just practicing my drawing Attached Imageslive well.pdf (38.2 KB, 77 views)live well2.pdf (31.9 KB, 37 views)
Reply:Minner,I also work in the marine industry and have a couple comments/suggestions.1.  125 gal is pretty large for a small boat.  Filled, we're talking about in excess of 1000# of weight.  What will this do to the boat loading?2.  Pretty large tank for the gauge material you're talking about.  I've used that gauge for fuel tanks of comparable size, but they were reinforced with internal baffles.  Baffles are out of the question when you're talking about a livewell.  You may want to consider some external bracing made from angle material.3.  You may want to reconsider your overall design.  I've found that oval livewells vs those with square corners work much better.  The fish tend to survive much better.4.  Unless you're pretty good with a spoolgun (doesn't sound like you've got a lot of experience), you may be better off tacking it up with your spoolgun and taking it to someone to do the finish welding in tig.  Aluminum can be funny stuff and is sometimes, especially for a newbe, difficult to get water tight welds with the spoolgun.Just my .02.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by minnerI am a noob at MIG welding aluminum but I am about to fab up a tank and have some questions for the experts.  I have a few criteria that I need to follow, so I'll give you the down and dirty. I am making a 125 gallon tank (livewell) that must me under 100lbs, and must be robust. I am planning on going with 11 gauge (0.090) but I am afraid that thin of material won't be to forgiving for a novice MIG welder like me. I have TIG'd aluminum many moons ago though. I plan on going with 3003 because the corners will be bent. What do you guys think, to thin, unreal expectations?Ok here are a few questions also, I have gotten a few prices on "11 gauge" material through my local welding shops and the prices have varied anything for $125-$175 a sheet. I didn't think much about it until I saw the gauge thickness charts on here......those numbers are for STEEL not aluminum. 11 gauge aluminum is .090 but steel is 1/8", BIG difference. I referenced back to my prices and I got to wondering if some of the welding shops assumed I meant 11 gauge steel equivalent instead of .090AL. Also in my haste I didn’t ask if they were quoting me 3003 and not 6061 which I will assume they weren't. Is it "best practice" to assume 11 gauge is referenced as .125 for all materials?Allen
Reply:Originally Posted by SundownIIIMinner,I also work in the marine industry and have a couple comments/suggestions.1.  125 gal is pretty large for a small boat.  Filled, we're talking about in excess of 1000# of weight.  What will this do to the boat loading?Who said I had a small boat?  Seriously though it's a 22 foot bay boat and have been running a 100 gallon tank (stock tank) for serveral years without problems2.  Pretty large tank for the gauge material you're talking about.  I've used that gauge for fuel tanks of comparable size, but they were reinforced with internal baffles.  Baffles are out of the question when you're talking about a livewell.  You may want to consider some external bracing made from angle material.I can't go external but plan on some internal "v" shaped bracing. 3.  You may want to reconsider your overall design.  I've found that oval livewells vs those with square corners work much better.  The fish tend to survive much better.I haven't lost a fish yet in my old tank, but you are correct about oval design. The area in front of my console is the determining factor of the shape, it will be a "drop in" fit and will be partially supported on 5 sides.4.  Unless you're pretty good with a spoolgun (doesn't sound like you've got a lot of experience), you may be better off tacking it up with your spoolgun and taking it to someone to do the finish welding in tig.  Aluminum can be funny stuff and is sometimes, especially for a newbe, difficult to get water tight welds with the spoolgun."difficult to get water tight welds with the spoolgun" Do tell on this one, like I said I'm a noob.Just my .02.
Reply:Leaks:1-amen to what Sundowner sez about making leak proof welds:    a.--the starts and stops, especially in MIG, WILL LEAK   b.--there's techniques to combat this, however if you've never done leak tight weldingin aluminum MIG before.....do you really want to learn on this tank?  c.-most practical way is to carefully MIG it, then TIG over the starts and stops, or just TIG the wholeshebang. (If I've migged an aluminum or steel tank, I break out the TIG to go after the leaks.)2-Heat distortion:    Despite what others may adamantly say about MIG---it 'can' have significantly less total heatinput to the aluminum than TIG can. Even fine tuning a high end inverter TIG via pulsing and frequency overlays....been there, dun' that.    All of that is dependent on the setup and equipment of the operator.     Before diving  into this project head first, try fitting up, tacking and welding some large, bent, formed, mockup pieces of the same gauge aluminum sheet. If the distortion doesn't 'get-u', the leaks will!Blackbird
Reply:Dave let me see if I can answer a few of your questions to clear things up.I have thought of the details on this so here goes.1.)By my calculations 2 sheets of .09 should run right at 82 lbs. This leaves room for wire, fittings etc. I could go thicker but that will drive the price up pretty quick.2.)I wasn’t planning on lapping the corners because I was planning on bending the sides, two U’s leaving only two welds. And welding along the bottom.3.)This is the first tank I have ever built so I am new to water tight welds but figured it couldn’t be much different……am I wrong?4.)There won’t be mounting tabs; it’s a drop in fit.5.)Yes reinforcing the lid area, as well as some internal “V” supports running on the long sides as well.6.)It will sit flat on the deck, supported 100%7.)It will sit on a rubber mat, if I can it water tight I plan on having it sprayed with Line-X, which will help in a lot of ways.8.)Yes1.)Yeah I know .090 is a little thin, and I’d be willing to go with .125 if I knew I could do it myself. I hate to spend the money on .125 and screw everything up.2.)Spoolgun3.)I’m usually pretty slow when it comes to welding; I try not to rush things. So should I abandon the idea because I have no access to a TIG machine? I was quoted $1K by the local shop? .Last edited by minner; 12-17-2008 at 08:47 AM.
Reply:Minner, its' not at all impossible. With some dedication toward it, you can make it work. With a small boat, the weight of the water will be a factor, and you should consider the problems it will create: You may take on water easier. You may capsize easier. You WILL be slower; you may need to change props to push the weight. I used to have a 57gallon bait tank on my 23ft. sportfisher, and even the weight of that was enough to make a difference in performance, holeshot, planing speed. I went down to a 45 gallon tank to compensate and find a happy medium.Good luck, Paul.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:You guys have already covered anything I was going to say. Weight is definatly an issue. That extra 25 gal. (from 100 gal. to 125 gal)is going to add about 200lbs. more than what you're used to. BobIf I knew that I was going to live this long, I would have taken better care of myself
Reply:Originally Posted by Happy BobYou guys have already covered anything I was going to say. Weight is definatly an issue. That extra 25 gal. (from 100 gal. to 125 gal)is going to add about 200lbs. more than what you're used to. Bob
Reply:A grand to weld it does'nt seem too bad. When I was doing fuel tanks, we charged $8.00 per gallon. 8 X 125 = $ 1000.00. That was about 5 years ago.If I knew that I was going to live this long, I would have taken better care of myself
Reply:Sundown hit all the concerns I had, mainly the baffling or lack of.I've made freah water tanks for fishing boats from 1/8" s/s roughly the same design and size, I put two baffles in those. Without suitable support either by baffling tied in properly or support of some kind outside I'd be scared of the seams popping. You get a couple hundered pounds of liquid banging around in a tank against a flat surface the impact is going to be quite high.....Mike
Reply:Minner,LOL,Wasn't trying to be critical with the comment "small boat".  For the last 20 yrs or so, I've been involved (Dealer, Broker, etc) with the sale and rigging of Bertram, Viking, Hatteras, Egg Harbor,etc.  Most of my deals are in the 50-75' range.  Most anything that will go on a trailer and down the highway is a "small boat" to me.  Sorry.  No insult intended.Back to the mig welding of the tank.  If I was building this tank, it would be tig welded.  With that said, if you decide to mig it, I would, as a minimum have someone "wash" the welds with a tig.  Think you'll find that that will eliminate a lot (if not all) the leaks which are inevitable with the mig process (particularly for a newbe).  Use 5356 wire for the spoolgun.I think you need to decide whether it's important to reduce the tankage slightly and add additional reinforcement or just build it to your design.  If you stay with the current plan, I suspect you're going to experience some bulging of the tank with the "live loading" you're going to experience from 125 gals of water sloshing around.For a one off project, and lacking the proper equipment (tig), have you considered using fiberglas to fabricate the tank.  Molds are easy to constuct from wood and bracing can be easily added.  When dealing with fiberglas, adding reinforcement is a lot easier than it is with aluminum.  Also don't have to worry about heat warping the plate.I've been working with aluminum for over 40+ years (heliarc welding our fuel cells for our race boats in the mid 60's) and if I was building this livewell for "my boat", I'd probably build it out of fiberglas.I know this is a welding forum but that's just my opinion.  Everybody's got one.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Yeah fiberglass was one of the original thoughts but the actual weight of the tank itself is of concern. I'm am trying to keep it to 100lbs max weight so that it's a one man lift out of my boat. Most summer months I dont need the well unless its a tournament; about every 6 weeks in the summer. During the winter I like to keep it in the boat just in case I catch a record.Thanks,Allen
Reply:Allen,A fiberglas build doesn't necessarily mean more weight than aluminum.  Proper design with emphasis on reinforcement will give you a lightweight but strong tank.All and I mean all the custom livewells we've built (built into the transom covering boards) have been fabricated in fiberglas.  You'll find that a rounded corner on the tank is much stronger than a 90degree butt joint.In the old days we were taught that fiberglas was (pound for pound) seven times stronger than steel.Just something to think about.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by minnerYou are right about the extra weight of 25 gallons, but in my plans (in my head ) I will have two overflows one for 100 gallons then another for 125. I wont need to run 125 in most tournaments but will in a few.......I like the way you guys think.
Reply:Originally Posted by Happy BobAre you planning on using this tank in addition to your 100 gal. tank?? Man, that's like 1800 lbs. that you are putting in a 22 ft. boat! Overflows or not, that's a lot of weight. Is your boat rated for that kind of weight?
Reply:Ok, You had me scared for a minute.If I knew that I was going to live this long, I would have taken better care of myself
Reply:Allen,Figured I'd post here since some others may be interested also.No, I'm not talking about a wood cored tank.  What you'd do is build a male plug (form) in the shape/dimension of the inner side of the box/tank.  Plywood or plywood covered with formica works well.  In the corners I generally use 1/2" plywood with a series of kerfs (done with the table saw) cut into it.  This allows for bending the plywood to shape.  Once the form is built I'll coat it with polyester resin (don't need to coat the area covered with formica).  Let cure.  Sand to very smooth finish.  Also, rounded corners release easier than square ones.Now that you have the male form completed, coat the entire surface with mold release wax (to prevent bonding to the plug).  Apply resin and glass, building up to desired thickness (I'd recommend about 1/8").  Once the build has cured, turn over and pull out the plug.  If the plug does not release easily, you can cut the molded part in half, pull from the plug and glass back together.  Add stiffeners as required.  What I'll often do is use 3/4" pvc pipe split in half.  Glass these in with a tab about 4" wide.  The pvc doesn't add much to the strength, just provides a form for the fiberglas.Top is easy.  Just lay out a piece of plywood covered with formica.  Wax.  Apply resin and glass til you get to desired thickness (here I'd recommend 1/4").  Once cured, just cut to size.  Oh yea, forgot to mention, for the bottom section, leave a lip around the edge where you'll attach the top.If you want to then get fancy, spray the whole assembly, inside and out, with gelcoat.Fiberglas is really easy to work with (sometimes messy but easy).  Been working with the stuff since I was about 10yrs old.  We used to build our own race boats (outboard racing) in the old Glaspar boat plant in Colonial Heights, VA.  We used their old, discard molds, add lifting strakes, grind off hooks, etc.  Became pretty good with the stuff.  Bought my first Corvette (wrecked) at 15.  Back then the insurance guys just didn't understand glass.  Two months later, I had a nearly new Vette for less than 3K invested.Well, that's the quick and dirty explanation.  May want to do a search on fiberglas fabrication or ask any questions.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Just thinking further.If you have a tub or pool fabricator nearby, you may want to check with them.  I would think that the winter would be a slow time for them and you may be able to have them pop you out a "tub" pretty cheaply.Building the mold is a large portion of the expense in fiberglas boatbuilding.  The technology is advancing rapidly though.  A couple years ago Viking Yacht (New Gretna, NJ) made the investment in a large 3 axis router.  The plugs are cut from a continuous piece of high density foam.  Really sped up the mold building process.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:You've got my wheels turning now on this fiberglass. What would happen if you used 1/4" styrofoam board for a core and glassed both sides? This way it would be insulated. I guess it would be nearly twice as heavy too since you are making two shells instead of one. Thoughts? Should I look for fiberglass in the marine realm, at say, West Marine or the like, or try a more direct route. How can I get the most for my buck?....good stuff....good stuff.....Allenminner,Styrofoam won't work for a coring material.  It's destroyed by polyester resin.  Not affected by epoxy resin but epoxy is very expensive and not needed for this build.Divinicel or end grain balsa are the two most used core materials.Coring will add significant stiffness/rigidity to the structure.  The separation of the two layers of glass (I beam principle) is where the rigidity comes from, not from the core material.If I was building this livewell, I'd core the top and bottom, and add stiffeners to the sides.West Marine has several good books on the use of fiberglas.  They are generally found in the section where the fiberglas accessories are located.I've also had good luck using body plastic (bondo) for creating molds that are hard to build out of wood.  Easy to work and releases well.  Also good for fairing the corners in a female mold.Years ago, Bertram Yachts used to build their fuel cells out of fiberglas using small squares of plywood as the core material.  Also used the small squares to core their deck hatches and decks as well.  With the divinicell you get basically an egg crate effect.  It works better if vacumn bagged, but will still "fill" to a certain degree.Most of the "better" yacht builders have been using coring in their decks & hullsides for years.  Viking began coring their hulls (below the waterline) about 5 yrs ago.Not sure where you're located, but with the slowdown in the boat business, many manufacturers are laying off people.  You may be able to find a fiberglas guy "on vacation" who would be willing to knock out your livewell for you for just a few hundred bucks.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.