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Old 18-08-2015, 12:51   #136
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Re: Steel Hull?

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From Jim Cate's post above....Micah, you seem bound and determined to draw this discussion into diverse pathways...
Yes; more on that in a bit. There's more to a boat than ultimate strength, especially when nobody builds these theoretical hulls. Even if someone did, they still have serious drawbacks; all materials do. The OP modified his question from whales, to impacts in general. I wish he'd been more careful in his choice of thread title...it is all encompassing, rather than solely about impacts. Let's run with it, and the question will be dead for the next few months until it all kicks off again from scratch.

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But it is interesting (at least to me) that the only boat that we personally have known that succumbed to a fire was... a steelie!

In this case, a small engine room fire that melted several hoses,the through hull valves for which were not accessible due to the fire... and the boat sank.
The hoses weren't steel, were they? I've seen a frp boat burn, it was spectacular; all the way to the waterline. It was also insured, so actually just an upgrade for the commercial owners. It happened in harbour, nobody was hurt (apart from a soaking in pristine eau-de-port for the skipper who wisely chose MOB).

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Further, now delving into mythology, I have never heard of a frp boat sinking due to osmosis blisters, but I have heard of steel boats sinking because of corroded plates.
No, blisters by themselves won't sink a boat quickly on their own....but frp owners don't like them, and spend considerable money to fix them, because they do weaken the structure. If they get bad enough, the boat is a writeoff, totally uneconomical to fix. The two steel horror stories in this thread were both fixed, by amateurs. There is enough evidence quoted already that shows proper construction and maintenance scotches the corrosion myth. Neglect will kill any boat.

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The point is that by cherry picking specific cases, one can "prove" almost any hypothesis one wants. One can build to any given required strength in most any medium... I think we can all agree to that, can't we?
Yes, one could also build in gold, marshmallow, or papier-maché.

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So, in the long run, the choice of materials should not be driven solely by any one parameter.
Careful, you don't want to get accused of drawing the discussion into diverse pathways.

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The wise builder will integrate factors like costs of materials, strength and availability of materials, skills of fabricators, ease of repair in the environment proposed for usage, even aesthetics in making the choice.
Not to mention fatigue and failure behaviour, and how the materials display signs of nearing their limits. Aesthetics is one we haven't hit yet.

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The blind trumpeting of ideological beliefs (steel is strongest...) is not a good position for a NA, be he a pro or an amateur.
I agree. Who, by the way, is trumpeting steel is strongest? Or composite? Go back and look. Certainly not me. What I will maintain, however, is that steel's advantages suit a certain kind of application, determined by an individual's requirements. I'd like for people to choose the best kind of boat for them, and to do so safely. Steel gets a bad rap from many poorly built and maintained privately built hulls over the years...but one can say the same for many pro-built frp's, if one ignores the many successes in both materials.

Steel Hull?

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And the bloody whales better watch out...
Agree, they've suffered enough. So have docks, reefs, containers, logs and other boats. Stop colliding! If you can't, deal with it, wherever and wherever it happens. Let's get to talking about aesthetics next....the safety aspect seems to have migrated to another thread. I've pictures of some very pretty hulls you wouldn't think were steel....they're not all hard chine or hungry horses. Mind you, the workboat scruffy look might have the advantage of discouraging thieves....

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Old 18-08-2015, 20:58   #137
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Re: Steel Hull?

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From a toughness viewpoint the graphs above pretty well say it all. The composites are brittle materials even though they may have higher tensile strengths. A point loading impact will lead to a rapid, progressing failure of the composite materials where the metals will yield then deform and absorb the energy of the impact.
No, they don't say it all. The comparison discussed has been between equal masses of the same material, and when you scale the composites up for that, their toughness scales by the same factor.

Toughness is given by ductility AND strength. Increasing either increases toughness.
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Old 18-08-2015, 21:33   #138
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Re: Steel Hull?

https://www.google.com.au/url?sa=t&s...HIp9rC4jWQmexA An interesting link to a crash test on a GRP dehler. Another one Here https://www.google.com.au/url?sa=t&s...rHbrikwgUW2pIQ

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Old 19-08-2015, 04:44   #139
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Re: Steel Hull?

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No, they don't say it all. The comparison discussed has been between equal masses of the same material, and when you scale the composites up for that, their toughness scales by the same factor.

Toughness is given by ductility AND strength. Increasing either increases toughness.
You mean thee comparison you've been discussing has been between materials of equal masses.

The op just wanted to know if a steel hull would give him an edge in bumper boats.

Most steel boats I've come across haven't been the same mass as most fibreglass boats of the same length I've happened across. Your whole argument has just been a podium to pitch custom fibreglass boats from the start.

You've got some followers and that's nice, but it really isn't what the op was asking.

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Old 19-08-2015, 05:09   #140
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Re: Steel Hull?

Have any of you expert boat building types considered what the whale is made of its durability, tensile, strength, hardness, brittleness, composition and all that sort of toughness stuff

And of course the type
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Old 19-08-2015, 06:19   #141
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Re: Steel Hull?

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You mean thee comparison you've been discussing has been between materials of equal masses.

The op just wanted to know if a steel hull would give him an edge in bumper boats.

Most steel boats I've come across haven't been the same mass as most fibreglass boats of the same length I've happened across. Your whole argument has just been a podium to pitch custom fibreglass boats from the start.

You've got some followers and that's nice, but it really isn't what the op was asking.

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I've been extremely clear about what I've discussing. If you haven't followed you've only got yourself to blame.

I posted here to show people that making judgements about a hull based solely on its material is not accurate nor of any particular value.

I'm not pitching anything - if I were the type to pitch for my potential benefit I'd be pitching aluminium.
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Old 19-08-2015, 06:28   #142
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Re: Steel Hull?

If you're not pitching then I'm not sure what it is your doing because you've been talking about theoretical boats. Production fibreglass boats, for the most part aren't built as you describe. Only very pricey custom and maybe rare production boats are built as you describe.

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Old 19-08-2015, 08:29   #143
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Re: Steel Hull?

I'm pitching for the whales
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