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PostPosted: Wed Sep 14, 2011 4:37 am 
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Joined: Sat Sep 22, 2007 9:49 am
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Location: Colborne ON Can
Hoping for some expert advice here. I've been pricing my fuel and holding tanks. :shock:
The fuel tanks are proposed to be 16 ga. mild steel ( One full sheet per tank)
The holding tank is proposed to be stainless, about a little more than a sheet of 16 ga.
I'm also planning to build a SS rudder.
Question is; I have fairly extensive mig welding experience, having build a 34' steel sailboat, and was wondering if it is possible (never tried it so unsure ) for me to mig the mild steel tanks, and two, whether it is also possible to mig the stainless tank.
Have purchased some 023 wire and tips, planning on a sample test ( for me ) I have a Lincoln 170 mig (220 volts )
Thanks; Doug


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PostPosted: Thu Sep 15, 2011 4:07 pm 
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Not Kevin, but a very experienced welder.

You should have no issues mig welding the tanks, however my personal preference would be at least an .030 wire. I would recommend at least a 75/25 ar/CO2 mix. Stay away from the straight CO2. If you can easily get it I really like 95/5 argon/oxygen mix. Makes the puddle a lot more stable and gives good pen without as much of a chance of blow thru.

As for the stainless rudder, mig welding stainless is easier with a tri mix gas. You may not want to spend the extra money but if you can get a small spool of a flux core stainless the welds will look a lot better. However you can do the SS mig welding with 75/25 gas. It will be a decent weld, it will just look like crap LOL!!. If you are using SS over 3/8" thick you may want to use a little preheat to ensure good pen with your mig set up. Anything smaller than that and you will be OK with your rig.


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PostPosted: Thu Sep 15, 2011 4:28 pm 
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Location: Colborne ON Can
Thanks for the feedback MCM.
Looks like I'm gonna go for it. Prices so far are beyond my budget.
I have somebody that will do tig where absolutely necessary.

Are you suggesting the 030 wire rather than the smaller (025 ) wire?

As for the stainless,flux core rather that using gas?

Thanks; Doug


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PostPosted: Thu Sep 15, 2011 5:46 pm 
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Actually the SS flux wire is a dual shield type wire and requires a gas shield also. The wire gives very good tie in and penetration with excellent bead appearances. Depending on the thickness of the plate and extrusions for the rudder, a stick electrode if you have a stick welder might be a better choice than having to buy the flux wire and shielding gas. A McKay 3/32 300 series of rod is a sweet easy running rod, especially if you can lay the material flat. Any plate 14ga or thicker would be a good candidate for the stick option.

I perfer the .030 over the .023 more as a personal preference over any tech reasons, although I think the higher energy with the .030 insures better weld quality. Are you building a steel hull boat?


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PostPosted: Thu Sep 15, 2011 7:17 pm 
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Joined: Thu Jan 24, 2008 11:36 am
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Location: Kenai, Alaska
slug, mcm, I don't know if the time allows or the budget can handle it but steel fuel tanks seem like they could use some discussion? Before discussing the welds I'd ask if you're prepared to treat the steel to some coating system that would insure it lasts? A good sand blast or wheel abraded sheet with some high quality epoxy will do the trick. What to put inside? Detroit and other (high volume) gas tank manufacturers all use sheets coated with some fairly high tech surfacing agents we can't buy at the metal suppliers.

The reason to ask is that the inside of the tanks may require some exotic treatment to stand up to rust with only 0.060"/16 gauge material to begin the tanks? I'd want to look at what your coating plans are before agreeing with the plans to use mild steel tanks- for anything!

Welding 0.060 with wire is fine if you're used to welding thinner metal (?) but your boat work may not prepare you for the travel speed and finer bead that mcm is used to using welding sheet metal. It welds fine, .023/.025" wire or even three-oh will do the work- but the issue to me is the post weld surface treatments? Even with a nice back bead and good welds, what surface will the gasoline and vapor face?

If the tank will be coated outside then you can blast or etch the HAZ and get adhesion, but the inside is another matter and that would cause me to head toward aluminum fuel tanks.

(well almost anything from the price of bread to hip-hop music causes me to head toward aluminum tanks... so my extreme bias should be noted in any reading of my opinion(s).)

As to the holding tank in SS, since it would fuse weld in 0.060" SS so you could skip the MIG entirely and use pulsed TIG. If you do MIG weld this sheet then I agree that dual shield will give a good edge to edge fusion for that sheet metal. I use wire feed TIG so I tend to do the work with that torch since the travel speeds are comparable to MIG but the control using high pulsed DC TIG is a bit more than I can put down (old hands) with MIG.

The rudder would have to be described for me to offer any views. If you're building a hollow shape around a shaft then one set of ideas seems most workable but if you're building a simply plate rudder on a shaft (?) then MIG or stick is more than enough. If you'd describe the rudder both mcm and I could 'see' a little more about what welds may lend themselves.

hope this helps some in your planning?

Cheers,
Kevin Morin

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Kevin Morin


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PostPosted: Thu Sep 15, 2011 8:22 pm 
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Beginning to think you had disappeared Kevin,,,, good to see you posting!!!


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PostPosted: Thu Sep 15, 2011 8:33 pm 
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Location: Kenai, Alaska
mcm, not a lot of metal boat work here and I don't spend much time commenting on cellulose except for furniture and the like.

Cheers,
Kevin

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Kevin Morin


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PostPosted: Thu Sep 15, 2011 8:39 pm 
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Doug I have to go with Kevin on this,,, I too had some concerns regarding a steel gas tank and the ability to control the corrosion. Like him I am all about some aluminum when it comes to tanks in a marine enviroment. Also I have to agree with him on the .023/.025, I guess I misread your original post, I was thinking of 14ga, not 16. You are going to need some pretty good skills to make the welds tight.


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PostPosted: Fri Sep 16, 2011 12:40 pm 
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Joined: Sat Sep 22, 2007 9:49 am
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Location: Colborne ON Can
Actually the tanks are for diesel, and I will probably do something on the interiors. Have decided to up to 14 ga and will definatly use the mig for the ms plate. As far as the stainless holding tank, not sure, but I found out ss flux cored is only available in large reels....to expensive for one tank.
Will either mig it or get someone else to tig.
As for the rudder, I'm going to go with a Schilling type rudder ( just have to try it...it's the way I am :wink: :lol: ) I will stick the 1/4 " top and bottom plates to the shaft, then probably mig the 1/8 side panels to the top and bottom plates.
Actually just got back from the water jet company, and the top and bottom plates are only $11 to $13 ea including material and profiling. Can't beat that.
Thanks again, and I will post pics when I have something.
Doug


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PostPosted: Fri Sep 16, 2011 1:04 pm 
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Joined: Thu Jan 24, 2008 11:36 am
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Location: Kenai, Alaska
Slug, I'd agree that thicker tanks in mild steel are prudent but I usually find by the time I've got decent coatings on steel I'm back to affording aluminum, but I can weld that with my equipment so its not much to convince me.

SS holding tank can be sheared and edge welded by TIG most easily if the 50lb roll of wire is more than you'll use elsewhere and you don't need it except for the tank.

Is the rudder mild steel or SS? not sure which is the Schilling, which is the Kitchen and several other types but they're all interesting to me as well. I end up with almost all outboard skiffs so the rudder shaft work is rare, I prefer it to outboards but the owner's are always right and we build what they want, not what I want.

sure would like to learn more about your rudder decisions I used to make the fixed blade types of plate welded to a shaft and usually used 3/32" SS rod to keep the bead fine and the heat down. Adding blades to shafts is sometimes a rodeo to keep the shaft element straight enough not to foul the stuffing box or pintle bearing.

Looking forward to learning what your project looks like as you progress.

Cheers,

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