Originally Posted by Jeff_H
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.
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.
The suggestion that any wooden boat can be as strong as steel is ludicrous. They survive no more than minuites on a coral reef in surf.Steel hulls sometimes last decades. The Yankee went ashore in Rarotonga in 64. In 73 I walked around her, hull and decks still intact. How many plywood boats last more than a few minutes in that situation, fibreglass boats not much longer.
How many hurricane seasons in open ocean on a coral reef was that?
Exceptional sailing abiliity in the average, heavily loaded cruiser, with all the owners worldly possesions aboard is almost non existent in the cruisers plying the worlds oceans ,nor do any realistic cruisers so naively expect it.Middle of fleet is the best they expect, and that does the job just fine. Those who spend megabucks for that extra quarter of a knot are still at home paying for it, while the slowpokes are out cruising, early and long.
Ease of handling, seaworthiness, seakindliness, of my boats have been proven over many decades and many ocean crossings to be one of the better proven ocean cruisers, certainly far better proven that one freshly off the drawing board. If they hadn't ebeen they wouldnt continue to be so polular and so much in demand , and no one after a pacific circumnavigation, would be building a second one, let alone a third. As for aesthetics, the photos Smackdady posted in this thread should clear that up.
We get all our steel wheelabraded and primed with cold galvanizing primer , eliminating the need for sandblasting , making prep minimal and easy.Did your cost estimates include sandblasting, an expense we dont have?
The 1 1/2 inch of spray foam we put on our interioirs is a far better insulator that plywood and epoxy. I remember living under the plywood deck on my first boat, seeing a layer of ice above my head ,with the wood stove roaring. Living under a foamed steel deck is warm and dry, as warm and dry as any boat can get, without the inevitable deck leaks from bolted down fittings, instead of the permanently waterproof welded down fittings, which cost me a dollar a pound. Someone speculating on the difference can be extremely naive, without having lived under both options thru a BC winter; definitley not a good source of advice on the matter.
The demand for my boats is also strong for their reputation for extreme comfort in winter, both underway and at anchor. The difference between plywood and steel, after an inch and a half of foam, is negligible.
Were your cost comparisons for a plywood boat of the same weight as the steel boat, or the same impact resistance, a plywood hull nearly 12 inches thick ?I dont think your thin coat of kevlar would be the equivalent stopping power of 3/16th plate.
The claim that it is only heat which makes wooden gun barrels impractical is ludicrous. Hunting rifle barrels dont heat up noticably. They are stamped 13 tons to 19 tons per square inch. How would your wooden barrel stand up to that kind of pressure.
They thought the use of aluminium for warships was a good idea til the Faulklands war, when they found they burn like cardboard. Looks like the military will have to re-learn that lesson of history with composites. I think that is the oxy moron called "Military intelligence". No surpirse considering it took until ww2 for them to change from Roman strategy to a strategy which caught up to their firearms technology.
Getting dark time to go. Swimin tomorow, while the guys paying for their High teck boats go back to work. Water was 71 degrees F alongside today, warmer tomorow . Will jump overboard several times a day. Do I wish I was working; to pay for a boat which goes a quarter knot faster? Not a chance!