Welding a steel hull

Ive never used the propane for cutting myself, worked with other welders that did, didnt cut as clean or fast as acetylene. I use the 125 CF size bottle and it last quite a while.
Not much mentioned on flux cored wire. Anyone actualy use it to build a boat? I use to use it a lot in the field but gave up on it, It was a lot faster on some jobs but very expencive compared to stick or mig. My bigests problem was the fumes made me sick, had to wear filterd mask and on a hot day in direct sun it was miserable. One of the things about it was you had to run the bigger sizes .068" and up, the smaller .045" didnt burn consistant. Back then it was NR211 and 203 N that we used, NR211 was declassified after earth quakes and they came out with a replacment 232 or something like that cant remember exactly.
Tom

 

I'm not into steel boats, but I use argon for the tig (similar to Wynands) and mox gas for the mig, which is also an argon mix.

I don't mean to tread off topic here, but how do one prepare a steel hull so it won't rust through in a week ?

Steel is relative easy to build something with, it could be that there is not enough knowledge about using steel and hence is not as popular as other materials ?

 

Shot blasting and Epoxies Fanie. During steel boat building boom so to speak - late 60' to 80" the best option was hot spray galvanize and or the paints available at the time. Since most steel boats were built by amateurs, very few had access or the funds for shotblasting. You just cannot shotblast a boat in your backyard:!: and due to these shortcomings, many a home builder resorted to checmical and other strange brews of rust remover that does not really work.
And this is the very reason steel got it's bad reputation as rust buckets...
Only one way to clean steel and that is shot blasting. And one needs the "velcro like" surface created by the shot for the paints to adhere properly.

With the advent of epoxies, steel can come into its own now as proven over the last 20 years using epoxy.
If a hull and deck is properly shotblasted, and a complete compatible epoxy paint system used, it will require less maintenance than a plastic boat, providing any damage gets repaired soonest, as is the case with GRP.

 

There are some yards here in Gautengeleng where you can take big metal things to for sandblasting... a common thing to do if you are ie doing some old rusted car over. Thanks Wynand ! Nice answer

 

I try get all my steel shotblasted and pre primed with cold galvanizing primer at the suppliers. Many suppliers have wheelabraders here. You then have to keep the primer up to avoid having to sandblast later. My boat took one month from steel arrival to launching, so it wan't a problem. The paint job is 24 years old and as good as the day I put it on except where it has chipped, where touch up has been easy.
Ordering your plate wheelabraded and primed is far cheaper and simpler than having to sandblast it later.
It's a good idea to wash the zinc primer with TSP , then vinegar , then water to get rid of the welding smoke and zinc oxide before painting her with epoxy.
Trimming outside corners with stainless trim and putting your stainless handrails on the corner of the cabin instead of inboard drasticaly reduces paint chipping on corners and thus drastically reduces maintenance later.
Brent

 

What you spend on a propane tip will be recovered many times over in the price of gas. I've burned six big bottles of oxygen with one 20 lb bottle of propane, at $18 per bottle.. Acetylene tends to be roughly one to one, and far more expensive per bottle..
I like to show beginners the very easy stuff first to encourage them, like horizontal welding with 7024. Once they have welded all their bulkwark caps on, they feel less intimidated by welding , and find it much easier to learn other rods. I let them weld the lugs on for pulling the hull together, then let them try to pound them off with a sledge hammer. By the time they are dripping in sweat, it gives them great confidence in the strength of their welds.
Several have gone from rank beginners to getting welding tickets and have gone from poorly paid labourers to highly paid welders, after building their boats.
Brent

 

I agree with Brent that pre-blasted and primer coated plates are the way to go by amateurs. Just one little problem with this. All or most primers but all epoxy primers have overcoat times otherwise the bonding between coats are not on par.
For instance, the epoxy primer I had now sprayed on a hull has an overcoat time of only 3 months max...

 

Gas Mix Ratios

Brent,
the correct gas ratio for acetylene to oxygen for cutting 0.187" 3/16" (maybe this applies up to 1/4" if you have good hands) and thinner material is 6:1 where the typical setting for O2 is 18-24 lb and the gas from 3 to 4 (or 5 depending on how good the gauge on the output side of the regulator is).

In running jobs with 35 welder/fitter teams and ordering rod, gloves and gas for the entire job- I'm sure that the ratio is at least 6 to one O2 to gas. If the plate is thicker this ratio drops because the blow-out (burning) O2 drops radically when you have to get 40 or 50 lb. of pressure to burn cleanly through 1" deck plate panels using a track torch.

So while propane, at a fraction of the heat value of acetylene, could work fine for some applications in thinner material the idea that the ratio's of gas to O2 would be different seems inaccurate. Why would hotter gas, that cuts more steel per cubic foot because of that heat ratio, need to flow at higher rates and be used up faster than a colder gas like propane?

I've see people use higher gas flow settings than listed here but since I've used these settings for so long, I don't see the need. I think you're mistaken on the ratio of one to one for acetylene and I'm sure the propane would take drastically more flow in any material thicker than say 1/4".

I've used a 'rosebud' burning acetylene to heat metal and I've used a propane 'weed' burner to do the same. The difference is so dramatic that I don't bother with the propane unless the job is very small and the oxy/acetylene bottle set is out of reach.

Cheers,

 

Wynand
Some of the epoxy zink primers have a year or more recoat time. Problem here in California it's been outlawed, to high of VOC I quess.
I am using Macro poxy 646 from sherwin williams and they claim it has one year allso.
I tryed to get pre primed sheets but could not find any anywhere in the western US. Getting to be kinda a bummer around here, cant get any good paints anymore, sandblasting has been outlawed in a lot of places. and you cant get pre preped and primed eather.

Rest
I never realy thought about the ratios between 02 and acetylene, I think I average around 1-1/2 to 2 bottles 02 to acetylene. I was tought when I first started 7 Lbs acetylene, 30 Lbs oxy. I run 8 to 10 lbs acetylene and 35 Lbs oxy. no matter what tip or thickness Im cutting, bit high but I use 100' hoses.
Tom

 

Wynand
The epoxy manufacturers usually sell a product such as (from memory) Devoe's Devprep88 that you wash an aged epoxy surface with and let sit followed by washing off with water, It removes the oxidised layer and the new epoxy bonds after the recoat time

Trouble is that you want weldable primers and these are not zinc rich primers so it is debatable whether you are better sandblasting afterwards inside and above the waterline decks etc and using a decent galvanising base coat which negates the need to get pre-primed steel in the first place. A few boats I have supervised had their own sandblasters which was very hady blasting at different stages even if it took two days with a small setup.

Epoxies are really coming of age. We can get products now that have no thinners 100% solids (no shrinkage) that can give 3mm build in one application. ( 150 microns used to be high build. )

 

Mike Johns
What brand or type of epoxy are you speaking of that has that high of build?

Anyone have any experiance with water based epoxy?

Back to welding
My take on brands of 6011, around here they mainly sell 3 brands.
Murex is the cheapest price and most common,welds pretty good and can handle moisture
Esab is a lttle higher priced than Murex, I like the way it welds and it can handle moisture allso
Lincoln is the most expencive and does welds good when dry, problem I have with it is it will colect moisture out of the air and not weld as good, even in the summer dry heat. Needs to be keped in sealed dry container, Murex and Esab can take a lot more moisture and still weld the same.
Tom

 

When you buy a tank of acetylene , the gas is disolved in a porous filler material to stop it from spontaneously exploding. The acetylene is also disolved in acetone, which leaves little room for the acetylene. Thus there is not all that much acetylene in a full tank. With propane, you get nothing but propane in the tank, you own the tank outright, no contracts, and you can get it filled for $18, even on a sunday. This is why acetylene is becomming increasingly rare in fabricating shops and shipyards. Expect the peddlars of acetylene to give you all kinds of ******** to try talk you out of using propane. They have a huge financial stake in it.
Propane tips cost around $15.
Try it. You'll like it.
Brent

 

Epirez 733.

Never even heard of the water based epoxy, I know some of the waterbased silicates are incredibly durable and are also a good option as a zinc loaded basecoat.

 

I haven't found that Devprep all that effective without a lot of labourious scrubbing.
When stick welding , look at the end of your stick. If the metal is sticking out beyond the flux, it will stick , Drag it across the steel until the metal is well back from the end of the flux. You can hear the change in sound when that happens. Then it won't stick. You may burn it back too far, then have to tap it a bit to break a little bit of the flux off.
When it sticks it sounds like the end of the metal rod is beyond the flux. Drag it a few times until you hear the hollow sound, then drag it up to your weld and continue welding.
I have found epoxy tar to be a very effective coating at $44 a gallon.
Brent

 

AC with 6011 is far better than DC for fitting , as it is far less prone to sticking when you are in an awkward position.
Brent