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Old 07-01-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Quote:
Originally Posted by Brent Swain View Post
Jeff , when your criteria are low cost, speed of construction, and impact resistance, could you put together your wood and kevlar hull and decks for a 36 for $9K worth of materials, in less that a week with only one skilled worker and one unskilled, working in a backyard, which I have done for a 36? How far could you get in that time with $9K worth of materials? Would it survive a sledge hammer for as long as you cared to pound, as one of my boats will?
Brent,
First of all, when I mentioned "low cost, speed of construction, and impact resistance" as primary design criteria, that was my attempt at paraphrasing my understanding of what seemed to be your consistent primary concerns in all of these discussions over the years. My primary concerns would include exceptional sailing ability, ease of handling, seaworthiness, seakindliness, and appealing aesthetics, and that would preclude steel for boats of a size that would appeal to me.

But that aside, as you should probably recall from our earlier detailed discussion on this, and the spreadsheet and reference notes that I provided at that time. In that earlier exchange, I had taken one of your Origami designs and had calculated the sheet sizes and weight of steel, welding rod, etc. involved in building it, and gotten a local, delivered price for those materials.

I did the same for the plywood, kevlar, glass and resin to build the same boat stitch and glue. They were close in price with the plywood composite construction being slightly less expensive.

On that spreadsheet, I had also gone to a welding manual and showed the rate of speed that an average professional welder could cut and weld the hull of that boat in steel and had put together a similar estimate of number of hours for the plywood composite boat built to a similar simple level of finish.

As you may recall from that analysis, you were right that you could 'pull together a steel hull faster. But when you factored in the time to prep and paint the steel boat, and that the wood composite version had more of its interior in place, the difference in time was negligible, and if there were layouts for cutting out the interior components, it looked like the wood composite version could be ready to go cruising slightly faster than the steel version.

And, yes, if constructed with kevlar and plywood skin of an equal weight to your steel hull skin, I would expect the composite hull to stand up equally well to being beaten by a sledge hammer for as long as you would like.

Quote:
Originally Posted by Brent Swain View Post
I found the statement about wood being as strong as steel, hilarious. Thank you for posting that. It points out clearly how far removed from reality some numbers jugglers can be. Now its up to you to tell the military that they will have to start making battle ships, aircraft carriers, tugs ,submarines and tanks out of wood as it is stronger and has more impact resistance. Then you could also do wooden gun barrels . I think they would find it as hilarious as I do. Anything less than your passing this "Breaktrhu knowledge "along to them would be treason!
Brent:
You really need to read more carefully, what was actually said was a wood/ kevlar composite hull would be stronger than a steel hull of an equal weight. But the military does not need me to tell them about composites. The latest US Navy front line ships are being constructed using primarily composite construction. They are doing this as a cost savings in terms of life cost, strength to weight, performance and the ability to protect the crew in battle.
Naval Composite Ship Program Moves Ahead

As to gun barrels, they are made from steel for material behavior reasons that has nothing to do strength concerns. Steel conducts heat much more effectively than composites. In the case of a gun barrel, one of the prime concerns is being able to keep it cool and there steel is more effective than composites.

On the other hand, on a cruising boat, the ability of a composite hull to reduce heat flow through the skin is a good thing making it more comfortable below than a steel boat, assuming equal weight and equal external insulation levels.

Respectfully,
Jeff
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