Restoring an old ship - need help

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I am working with a group restoring a WWII ship.  I am trying to patch the cowl vents that routed fresh air to the interior spaces.  Most of the damage are small holes from rust damage, and much of the surface material is rusted.  I am a new welder using my Lincoln MIG 140 with fluxcore wire (.035) to fill small holes and weld on patches (14ga) to the larger areas. The cowl is made of 14ga mild steel, but seems to have many thinner spots because of 60 years of weather damage. I am using settings suggested by the mfg for 14ga mild steel.I don't have any experience in welding material other than new, so I don't have much experience with old rusty material.  I have removed as much surface crud with wire brush and sanding disk as I dare without creating more damage.  It is very easy to create a big hole while trying to fix a small one.  I am getting mechanically sound, but really ugly welds.  The arc sputters a lot and the margins are anything but uniform. If you have thoughts and suggestions, I would be glad to hear them.  I want to do a good job and suspect most of the problem is my technique, not the equipment.Thanks for the help.......
Reply:I would use a .023 wire with 75/25 gas, low volts and matching wire feed.  This is lower heat than you will get with fluc core and possible a nicer weld with no slag or spatter.  JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:What he said.  Bare wire is so much easier to work with.  It does what you want with less heat.  NO slag at all.  If you  are patching holes in rusty stuff, ditch the flux core.  You will be one happy weldor.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Another useful trick is to back up the weld area with another hunk of metal. If you can leave it there, a strip of the same material is fine. Let the weld burn into the backer.If you can't (or don't want to)leave it there, back steel up with copper or aluminum. Aluminum is cheaper and easier to find. For 14Ga, a hunk 1/4" to 3/8"  thick should be fine. Copper is better (higher melting point, better thermal properties), but more expensive. The metal supports the weld metal keeping the puddle from falling through as well as leaving a clean back side, and conducts heat away, helping the back freeze in quickly and reducing the risk of burning excess material. The better the fit to the backside, the easier the weld will be. Try a few practice pieces, and you will find the fit that meets your needs.BTW: Which ship, and is the plan to have it operable? Queries have come in at one of my jobs over the last couple years about boiler rebuild and recertification for a couple major projects.Last edited by enlpck; 10-27-2007 at 11:31 AM.
Reply:Thanks for the advise.I think I can leave a backer in place, and will try smaller wire and lower amperage. We are trying to make all repairs period correct, and a patch on both sides should be OK. One of the goals is to keep water from getting to the base material in the damaged areas, and cosmetics are part of the equation.  I will be working on it next week and will give the suggestions a try.The ship is a Victory ship launched in late 1944 from yard 1 in Richmond, California.  It is generally in good shape but has a zillion details to be dealt with, so it is a long term project.  I am new to the group so I have much to learn - should be fun.Thanks again for the tips, and I will no doubt have other questions as I get deeper into the project............
Reply:This is the Red Oak or something?  I was thinking of volunteering there a while back.  I wonder if it would be easiest to just epoxy/glue a patch over the hole.  Panel bonding adhesive seems like it would do the trick.  It's the same stuff they use to glue body panels on cars.  You don't have to deal with the fire hazzard, either.  You never know what is lurking in those ducts (primarily old paints and grease) and a fire can travel just about anywhere in the ship through the ducts.  I'm sure your fire dampers are rusted away and non-functional so it would be difficult to stop a duct fire.Last edited by 76GMC1500; 10-27-2007 at 03:08 PM.
Reply:Yes, it is the Red Oak.The vent cowls are on the deck for welding so there is no chance of fire spreading through the ship.  We want to weld the patches so the repair is period correct - the goal is to make the ship as historically correct as possible, even though it is often more work.If you are still interested in volunteering, come on down - there is still plenty to do.Thanks for the reply........