Miller 251...

I'm useing a Miller 251 with the Alum. spoolgun ... to build my boat. i need opinions pros and cons on the machine.. 1/4 3/16 and 1/8 5052 alloy

Everything below the waterline will be Tig welded. thank you Tom

 

you don't want to Tig weld the bottom. It puts too much heat into the boat. Weld the seams inside and out.
The Miller 251 is a fine machine. I personally don't like the feel of the 30A gun,but it is a good gun.
If you have the chance ,the 350 Mpa pulse machine is incredible with the Aluma pro gun. There are still places that the spool gun is the only tool to get into tight places.
Good luck with your project ,post a few pictures as you progress.

 

Welderbob,

I would appreciate it if you could help me understand all this a bit more. I recently purchased a miller mig with an aluminum spool gun and am learning how to use it. But my question has to do with my limited understanding of how all of this works. I thought the beauty of TIG welding was the control of the heat that was possible.

Does mig welding put less heat stress into the boat because it is a faster process?

 

WelderBob... thank you for the input... throwing money at it,sure i can get a better welder... machine is good but others have said the same the spoolgun leaves a bit to be desired... The gun comes with brass tip. I'm going to try copper as we used that many years ago... Iv'e heard the extended tip gives better performance. Who knew longer is better, oh well. Haaa..! When all is said and done I want the outside finnish welded in tigbelow the waterline... So i can Sleep at night. Too many alloy boats have the bilge pump running all the time..

 

Welding Aluminum Hulls

Accurate, Tolly, welderbob

I don't know that power supply well, but MIG for any part of the hull is fine IF the welder can weld. I'd say if there were any metal boat that had weld leaks the person doing those welds wasn't qualified to do that work?

MIG below the waterline is fine in aluminum boats, TIG is OK for corners and tie-ins and for locations that might have multiple thicknesses coming together in the weld zone, but overall its not very efficient because its generally slow.

The high heat results from the speed of travel of the welding process, inches per minute compared to feet per minute with a MIG torch. So, net heat, all-up energy imparted to the metal is less with MIG because the weld deposition rate [travel speed] is higher when compared to most unmechanized TIG.

TIG's heat control is at the puddle level, right there at the tip of the tungsten you can add more or less heat not true with MIG where you have to move much more rapidly and control is harder adjust in any single puddle. But, TIG does move slow so the heat of fusion is added to the parent metal longer and therefore for the same amount of bead you'd have more net heat.

You might say that MIG is like driving a car using only the steering wheel -no gas pedal or gear shift. TIG is like having the foot pedal and other controls AND the steering wheel. So with MIG you set the related rate values of amperage/voltage; wire speed feed; gas flow; angle of arc and 'go'- guiding the weld only. [Of course you can vary the angle, whip the puddle and do other slight adjustments but you can't necessarily reduce voltage unless you've got remote controls; that are not common.]

With TIG you adjust the amperage/voltage, filler feed rate, angle and travel all the time and that is why the statement that TIG is more controllable. The control costs speed in most TIG applications.

Spool guns are fine but there are some very tight corners they simply won't fit into and still allow you to see the arc and weld. Some other physical arrangements make the pistol type [Spool] gun more useful than push pull- it depends; I prefer the slimmer push pull type for all welding. [But...] Push-pull guns are much more expensive, on the other hand I think they afford far better overall welding access inside a boat or in a tank. I also like their agility being more compact and aligned to your hands instead of T shaped with wire housing on the forearm.

cheers,
Kevin Morin

 

Thanks Kevin,
LOL, as a rookie I need all the help I can get. I just got done making a new tensioning arm for my alternator, finally I can effortlessly tighten my alternator belts. Welding is like magic

 

Kmorin... Appreciate the input on the mig... and tig... Even the best welder with all the qualifications in the world can't build a no leak boat period...
this is the reason for non-destrictive testing... any smart person having an alloy boat built will dye test below the waterline. Iv'e built 3 Aluminum boats in my lifetime.. and now i'm building mine... all sailboats. Now mine will be a powerboat. What kind of welder am i to think that my welds are so perfect not to need testing... Now that's a fool right there... If i can find the dye i will use it. Can't tell you the number of boats that sunk for grinding outside welds... A boat with vibration and pounding.... Tig it is my friend.

 

Leaks?

Accurate twrs,
"Even the best welder with all the qualifications in the world can't build a no leak boat period... "

If a man has an experience that seems to run counter to anothers' experiences, that first guy most often won't be able to rely too heavily on the second's experience.

You may have had some leaks and that leads you to believe all welded aluminum boats are leakers, but having built a few myself, welding every inch, I don't have the same experience. So I can't buy into your statement about all welded boats leaking.

"this is the reason for non-destructive testing... any smart person having an alloy boat built will dye test below the waterline. I've built 3 Aluminum boats in my lifetime.. and now I'm building mine... all sailboats. Now mine will be a powerboat. What kind of welder am i to think that my welds are so perfect not to need testing... Now that's a fool right there... If i can find the dye i will use it. Can't tell you the number of boats that sunk for grinding outside welds... A boat with vibration and pounding.... TIG it is my friend."

I agree that some places NDE is useful but all the welded aluminum hulls I've built were MIG inside and MIG outside and didn't have any testing besides launching. Some of the hulls did have flotation decks or air voids under the deck so I could pressure test the welds, but even then it takes 3-4 lb. to show any soap bubbles.

There were also many boats that were open bottom and no way, except die, to test the welds and they didn't leak- so I can't see spending time with dye.

I may not be smart for doing it this way- but since I haven't had any leaks in the few hundred welded boats I've built, from 10' to 42' I don't see the need to spend time die testing. Different experiences, lead us to different points of view.

I may be a fool by your experience, but it seems more foolish to me spending time tie testing when I know the quality of the welds; they are tight.

Now as to grinding off MIG weld- that is not accepted practice in welded aluminum single pass welds, and it can expose a root porosity that is native to Aluminum MIG making the weld subject to crater cracking or flexure failure by notches. I agree that sanding off the bead on welded alloy is poor practice. [Only Pulse w/Pulse MIG or globular transfer MIG seems to be completely free of root porosity in 5000 series aluminum welds.]

If the bead will be sanded off, then a butt seam backer should be used and the weld put down in lifts or passes. This means there would be root pass where the two butted [gapped] parent metal hull panels were fused to the fully consumed and permanent backer in one uphill 'hot pass'. Next, the second pass would be lighter and may be done down hand, and it may even require some clean-up filler when sanding exposes the occasional gas pocket. When MIG is made to this level of cosmetic surface prep it must be welded correctly to begin- that is the joints have to be prepared for this weakening of the final weldment.

I like TIG and use it often, wouldn't be without it, in fact; I prefer to TIG weld over all other welding processes.


Here is the TIG gun I use on the Miller Dynasty 300DX, rigged for steel, and the welds I do in aluminum with this torch.



Here is an example of all three types of welds. The 'key' cleat is TIG welded to a TIG welded base set against a MIG welded liner pipe that is on the inside of the 1/2 pipe gunwale MIG weld that is sanded fair to create the sheer's rounded and smooth look. To prepare the sheer joint where the 1/2 pipe extrusion forms the right/outer side of a U joint the sheer clamp is the opposite side and the hull's topsides forms the bottom of the prep. Then an overly hot single pass MIG weld is 'soaked' into the U joint so the puddle sags slightly into the topsides plate/sheet. This allows a full fusion and high penetration weld to be sanded off but leaves the joint full strength.



I think TIG is the best weld there is- baring none. But it still takes a lot longer, and I'm using a cold wire feed gun that is much faster than anyone can hand feed dip rod when I say that, and have welded for more than 6k hours of aluminum.

MIG for long hull seems is fine, and widely used by all the major builders without any NDE testing without any problems or leaks. I do agree with you that nobody sands off the weld bead crown of single pass Aluminum welds unless they're inexperienced or uniformed.

TIG is great and I pressure test all tanks and air voids in all boats and use TIG to float closed the pressure leaks, but 99% of all [my] leaks are in the keyhole welds of the decks or tank tops. Having done a few miles of 'both sided' MIG chines without any leaks I consider that pretty normal too. Knowing lots of other shops who use similar methods with similar results, combined with my building experiences; I just can't agree there's a need to dye test double sided MIG seams.

Cheers,
Kevin Morin

 

Thank you for setting the record on welded aluminum boats. You are right,aluminum is the miracle metal.

 

LOL,
Do KEY cleats cost extra? That looks like something off of Orange County Choppers!

 

They boat looks like the boat that Kevin built for his wife. The key has aspecial meaning.

Go over to www.aluminumalloyboats.com and check out the memorial piece that Kevin built for a friend.

 

Kevin.... Nice little gaget you got there... sorry but i could'nt rely on that cute toy... if you have that much time on that torch. Great you trust it and it has worked well for you. Between the aluminum tanks and other sheet related projects i just perfected my tig to the best of my ability.. just pressure test and go...That would never make it on Anodized pipe. Most all my clients want t-tops and towers for their boats www.AccurateTowers.com. When i have enough pictures of the boat i'll post them.. when i find out how to post pix..

 

Holy cwap.... Kevin... the memorial you made is phenominal. The detail and boat are estounding. thought i was going to drown in the waves.... truly
creative.

 

Kmorin... Refereing to the auto tig torch that i called a toy... OK you got me thinking about it. Years ago i always thought someone would make such a torch... The more i thought about it and you haveing such a torch... makes more and more sense all the time.. It looks bulky to use. Is it easy to use ?
I can't imagine how it would function... Sometimes tig torches are touchy enough.. but haveing multiple functions all at the same time...what can you say about it...??? Tom

 

OTC TIG Gun

Accurate twrs,
The TIG gun is easy to use once you have converted, mainly because its two handed welding compared to both hands separated -torch and dip rod.

The controls are all on the torch on the right hand. A trigger is on/off and starts whatever sequencing your power supply provides- like gas prepurge and hi-freq arc initiation then power on.

I have modified the gun to allow both the amperage remote and the wire feed speed to be under the right thumb as rotating knobs/wheels on potentiometers to increase decrease both wire feed speed and amperage. The system on off toggle switch is just above the thumb on the side of the case with the two pots.



I find it much easier to use than hand torch and dip rod because I'm more steady and don't weld regularly -unfortunately. There are places where the torch is not convenient -like hand rails close to the gunwales with angled legs. The torch body is too large to swing under the rail and above the gunwale- or where the torch has to reach in to an enclosed space and you can't see past the case.

Generally this torch will increase TIG speed by 10x maybe 20x over hand torch and rod because there is no pause for wire replacement for 50-150 feet of weld (size dependent) and there is no/very little fatigue in out-of-position welding. So you can weld nearly continuously for hours on end without doing any more than moving to the new weld and fire up.

In structural pipe welding - like towers and railings it will have many more times an interference issue than open hull and tank work, so it may not be as helpful for everyone's work as it is for mine. I do 99% of all my TIG work with in -including metal memorials, and steel pressure pipe and steel. I've even welded copper buss bars for industrial motor control centers with this torch.

As to controlling the torch, I get into the weld zone with the tungsten close enough to light and pull the trigger, holding it on. The power supply's hi-freq lights the arc. Next, I dial up a little heat, which I've closed to "0" on the last puddle in the previous weld to back out of the crater, and continue adding heat until the puddle flows. This is done with the thumb on the pot's knob.

After I have a little wet spot I add some wire by rolling the other wheel a bit and the wire feeds to the puddle and I'll generally add some heat and wire once or twice more in small taps of the two controls to get to the puddle size and shape I want.

This takes 5 to 10 seconds then I weld with both hands stabilizing the torch steadying the entire cup and electrode with the back of my left hand as I would with a MIG torch. My right hand rides the two controls- wire feed and amperage and I reverse the process to stop and finally let off the trigger when the wire is stopped and the arc reduced to 'nothing'.

Just like hand torch work with a pedal but I can walk and bend and reach overhead without moving the pedal or bothering with a slider on my torch hand. The off-hand doesn't need to have back clearance for the rod and the overhead welds are just like down hand or uphill- less work with both hands together than apart.

I don't know any right handed welder who ever went back to a hand torch from this gun once they'd spent a few hours getting the feel. Controls can be set up in many different ways, I used to climb in and out of boats for 14 hours a day with one or another torch and found this gun made my TIG time much more productive.

Like any specialized tool it takes time to make the tool 'yours' but it does bring very high levels of productivity to TIG by comparison to a hand torch.

TollyWally, the cleats are a little off the beaten path, http://forums.iboats.com/showthread.php?p=2405118#post2405118
this link explains what they're all about.

Cheers,
Kevin Morin