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Old 12-22-2013
Brent Swain Brent Swain is offline
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by outbound View Post
Good thing my wife knows my on/off switch but too bad she also knows just how to push my buttons.

Getting back to the O.P. Down at the yard there's a ~60' steel bulbous bow trawler. We've had a lot of wind recently and given the size of the thing and the windage she went bump into something hard. ( don't know the details). The cut water and port side of the bow were struck when she was leaving to go south. There were three significant indents. What surprised me was when talking with yard hands was:
Dented areas could not be hammered out or forced out with hydraulics. Any indent stretches the metal so original shape cannot be restored. Just like with a car skin.
Dented area should be presumed weak and should ideally be cut out.
even if not struck on frames- frames and symmetry of the hull need to be examined closely. Repair may need to involve area much larger than area of apparent damage.
Area to be refinished will also encompass area much larger than apparent damage.
Mounts and welds quite some distance from point of impact also need to be examined and may have failed.

It's true the hull skin remained intact but the repair bill looks like it will be quite significant. Surprising so given the external damage did not seem so bad to my un educated eye.

This boat was fully framed. I can see how after repair she'll be "as good as new". I can't see in a similar circumstance how one could restore a frameless hull to it's original conformation if the dented portion of the hull was in a portion that was bent as part of the origami method?

Brent has made much of the strength and ease of building in steel. I have some limited knowledge of repairs in solid glass, cored glass/synethics, and cold molded wood. I thought metal repair was much, much easier.I thought that was one of the major advantages of metal boats. It was an eye opener to hear of the potential complexities of metal repair. Particularly if one wants to restore to original beauty and hull conformation. I think I gained understanding why with commercial boats it's not uncommon for dents to just be recoated and left alone.
Sounds like your yard hands really know how to talk their way into a lot of extra work and wages. Kinda like the sand blaster who will blast to white metal perfectly good paint, with nothing wrong with it, as soon as your back is turned. He is paid by the hour, the more hours the more pay.
My reference to toggle switch vs rheostat, was an interview with a neurologist on AM radio KGO San Francisco. He was talking about religious and political fanatics having the disorder. It was a reference to Mike's suggestion that a curve adds nothing to strength, until it reaches a certain point then and only then does it become suddenly stronger. The added strength starts as soon as the metal starts to curve, increasing gradually the more curve you put in. He has stated that Lloyds makes no allowance for this, and ABYC only 15%. The difference between a square pressure bottle and a round one is a whole lot more than 15%, and undeniably more than the Zero Lloyds gives. His posts contain many "either or, black or white " toggle switch type assertions.
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Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"

Last edited by Brent Swain; 12-22-2013 at 08:43 PM.