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Old 02-06-2020, 21:17   #16
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Re: Steel hull how thin?

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Originally Posted by Boatguy30 View Post
My mistake on the guage, but still an interesting discussion on how much of a steel boat can be reached.

I'm not an engineer but I would assume 144 1" pieces welded together is not as strong as a single 1 square foot piece? Or is the weld 100% if done right?

Weld efficiency (without radiography) is typically:


Single butt weld = 70%
Single lap weld = 50%


But other factors can be used with inspection or other weld designs. Double butt welds with inspection are generally 100%, but I doubt many boatyard weld will meet pressure vessel standards in a number of regards. Additionally, corrosion is a bit more common near welds (often in the heat affected zone next to the weld).
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Old 02-06-2020, 22:29   #17
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Re: Steel hull how thin?

Quote:
Originally Posted by Boatguy30 View Post
My mistake on the guage, but still an interesting discussion on how much of a steel boat can be reached.

I'm not an engineer but I would assume 144 1" pieces welded together is not as strong as a single 1 square foot piece? Or is the weld 100% if done right?
Probably stronger if the welding is good.

If you tack the patch in place on the outside then go inside and lay down a good bead all around then go back outside and grind a bevel down to the inside weld metal then fill and grind back flush you end up with a piece of plate surrounded by a thicker "fence" made from generally stronger metal than the original mild steel plate. Mild steel does not heat effect to badly.
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Old 02-06-2020, 22:32   #18
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Re: Steel hull how thin?

The strength of the weld isn't that important when it comes to joining plates on a boat imo. Even a lack of root penetration is somewhat irrelevant as the weld reinforcement / throat thickness will usually compensate. Defects such as lack of fusion, porosity and undercut can, however, have an adverse affect.
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Old 03-06-2020, 12:25   #19
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Re: Steel hull how thin?

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Originally Posted by Boatguy30 View Post
10 guage I thought was .100" so less than 1/8". t...
10 gauge is actually slightly over 0.14", so that's 40% thicker than 0.100".

An easy way to remember is that 16 gauge is 1/16". Then SKIP 15 gauge (never seen it myself) and for each step heavier add 1/64", so 14 gauge is 5/64", 13 is 3/32", etc.
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Old 03-06-2020, 17:05   #20
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Re: Steel hull how thin?

Steel doesn't have to waste. Properly coated and maintained, it will last forever. Either the right epoxy or zinc. I owned a former navy tug that was zinc spray coated many years before I got it. The was no wastage at 35 years old when I had it surveyed. Some test holes were drilled to verify. It made me a believer.
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