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             Patching aluminum
 Dennis wrote:

 I have an old ChrisRomer aluminum hull that I have repowered from twin to
 single engine and have had a lot of problems patching the old holes in the
 bottom. I have had advice from overlapping patches to holes in aluminum cannot
 be repaired. I am hoping you can give me some sound advice. The hull is 5086
 and I am patching with the same. The hull has small amounts of corrosion. I am
 using a mig welder with 5356 wire. It seems to me that during the weld I get
 small holes in the weld that leak when I do an air test. What do you think?
 Thanks Dennis

             Walke Point Marine Consultants

It is possible to repair  aluminum hulls. Can you provide more details of the
repair. What is the thickness of the hull. What is the amps and voltage that you
are trying to weld at. What is your gas flow. How big is the holes to be
repaired.  Your main problem may be the cleanliness of the material being welded.
Have you tried GTAW instead.  Please provide me with some more info. I also can be
reached at (757) 426-1405.


Dennis wrote:

 Thanks for your help. My welder only has numbers on the power from 1 to 6 and
 wire speed from 0 to 100. I have been using 5 and 70. Gas flow of 35. The
 patches are around 4"x8" with the largest 8"x12". I don't know what GTAW
 welding is. I think that  it must be dirty because as I am welding the sound
 changes at times and it will start to crackle and I have seen the weld just
 split with some on both sides of the joint and nothing in the middle. I clean
 with a ss brush and have also used acid. Dennis


Walke Point Marine Consultants wrote:

GTAW = tig. What is the thickness of the material that you are welding. Are you
using a lap weld joint or an open root joint. If you are using open root try
using a ceramic backing strip, this will hold the shielding gas. Are you taking
measures to prevent loss of shielding gas. An argon mix provides a greater
cleaning action/ hotter arc.

Dennis wrote:

> Lenny, The aluminum is .190. What is a ceramic backing strip? I am doing a
> butt weld. Tacking on one side then welding the other side but only about
> three inches at a time trying to keep it cool. Then using a saw back chipping
> the other side and welding there. How wide should the weld be or how high. I
> am using 035 wire. Since I am working outside maybe the shielding gas is the
> problem. Working inside the boat I didn't think I was getting any wind. Is
> black soot normal  and can you reweld over it without cleaning it off?
> Dennis

Walke Point Marine Consultants wrote:

I think we have found the problem. The loss of shielding gas results in a black
sooty weld. Take precautions to block the wind from blowing the shielding gas
away. It is necessary to remove the soot, it will make welding more difficult and
contaminate the weld. Ceramic backing can be purchased from a welding supply
store, it is a series of ceramic tiles held in place by a metallic heat resistance
tape. The weld should be fairly flat, if the weld crown is 1/8" above the base
metal it is satisfactory. Good Luck

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