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Old 13-01-2011, 22:24   #1
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Go the Triple Diagonal

Here is a bold statement - and I am already wearing my flak jacket.

Well-constructed triple-diagonal (cold moulded) hulls are the best form of hull construction.

I have owned a steel boat and classified it as fairly easy to maintain.

I have owned a very well built plywood boat and classified it as easy to maintain.

Currently I own a well built GRP boat and it is also easy to maintain. When I say easy, I mean one has to bend the back from time to time, but it's not too appalling really.

But I think the cream of the crop for a raft of reasons is the well-built triple diagonal with a dynel/epoxy sheath. The downside of course is the cost of construction. Compared to other methods it is very expensive, making it prohibitive for most peoploe unless you have the skill to do it very well yourself.

I would be interested in your comments.
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Old 13-01-2011, 23:23   #2
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But I think the cream of the crop for a raft of reasons is the well-built triple diagonal with a dynel/epoxy sheath. The downside of course is the cost of construction. Compared to other methods it is very expensive, making it prohibitive for most peoploe unless you have the skill to do it very well yourself. I would be interested in your comments.
That's just a strip plank, isn't it? Three layers of it? I always understood strip plank was cheap in terms of materials because it's glued and nailed and glassed so you can use odd lengths, and because you need only a temporary jig out of any rubbish timber. Of course lots of labour but you never tally that :-)
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Old 13-01-2011, 23:52   #3
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Here is a bold statement - and I am already wearing my flak jacket.

Well-constructed triple-diagonal (cold moulded) hulls are the best form of hull construction.
LOL Is that it? No explanation as to why you believe it is the best form of construction? It certainly isn't the fastest, nor cheapest. How do you define "best"?
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Old 14-01-2011, 00:04   #4
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No, it is not strip planked. That is another method.

Triple diagonal cold moulded is good because of -

strength for weight

no osmosis

no rust

no worms

no electrolysis worries (unless you're affected by something like stray currents)

easy upkeep.
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Old 14-01-2011, 00:43   #5
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No, it is not strip planked. That is another method.
Quite right. I'm blaming the weather.
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Old 14-01-2011, 15:48   #6
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No Dynel?

Having built a small plywood yacht I find Dix's advice to use additional thickness of wood rather than (from memory he was talking about fibrelass rather than Dynel) sheathing compelling.

I would imagine that a final layer of a hardwood that takes glue well would impart fairness, strength and a little buoyancy. Not to mention impact resistance.

On a separate note I have been way less than impressed with the peel strength of the foaming polyurethane glue that I have been using on my interior. I'll probably go back to PVA.
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Old 14-01-2011, 17:40   #7
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Yep. The foaming polyurethane seems to have the adherence characteristics of bluetac.
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Old 14-01-2011, 17:42   #8
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Talking

Is nobody going to hammer me on the triple diagonal thing? Call me a scoundrel and a mongrel and so on?
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Old 14-01-2011, 17:51   #9
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Is nobody going to hammer me on the triple diagonal thing? Call me a scoundrel and a mongrel and so on?
Nahhh, you're not a scoundrel, but strip plank is a better format! This from a strip plank boat owner, of course!

But, IMO use of glass and epoxy is a better scheme than Dynel, since it adds structural strength as well as just a worm-proof sheathing.

Either technique in the hands of a good shipwright can produce a wonderful hull and deck -- light, surprisingly strong, pretty (if left bright, inside or out), pox and worm free, and well adapted to one-off construction. And (although I can't back this up with fact) it seems to be not that much more expensive than any other one-off hull construction IF you specify round bilges rather than chines.

So, yay for modern timber construction!

Cheers,

Jim and Ann s/v Insatiable II lying Towlers Bay, NSW, Oz
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Old 14-01-2011, 17:53   #10
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Is nobody going to hammer me on the triple diagonal thing? Call me a scoundrel and a mongrel and so on?
You scoundrel! When are you going to tell us no-nothings what a triple diagonal thing is?
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Old 14-01-2011, 17:55   #11
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If "best" means a strong boat, you're correct. But G-d help you if y'have to repair a good sized hole going all the way through. Got a lotta peeling to do.
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Old 14-01-2011, 17:57   #12
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Is nobody going to hammer me on the triple diagonal thing? Call me a scoundrel and a mongrel and so on?
Nope because years ago I read this:

Northwest Passage Solo: Amazon.co.uk: David Scott Cowper, Walter Kemsley: Books

Its the story of a mad Englishman (they all are ) who took an old lifeboat through the Northwest Passage only he didn't quite make it in one go so left it there for a winter and went back to unfinished business.

Having done that and had quite enough of ice he then took it around the world again.

Not bad for a wooden boat


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Old 14-01-2011, 17:57   #13
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Before a war gets started, which type of hull material works best for any given vessel depends on the application and budget. This is why there is no one best material, it all depends on the type of vessel and how it is going to be used.
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Old 14-01-2011, 17:59   #14
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Sure, cold molded ply is a great construction technique. Excellent strength to weight, very long lived and fatigue resistant if built well. The downside is that it is slow to build. If you don't mind putting in the time (or money, if you're hiring the work out) it yields an excellent product.

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Old 14-01-2011, 19:12   #15
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Don1500...cold moulded is a technique whereby planks of wood are laid up in directions diagonal to each other - usually two or three layers of timber. it can be viewed as a plywood, but made of solid wood planks. Apart from being known as cold-moulded, it is also sometimes known as diagonal planking. Depending on the number of layers, it's known as "double diagonal" or "triple diagonal".

Also, I agree that strip planking is pretty cool also.

I've never owned a cold moulded or strip planked boat, but a friend built a triple diagonal which is a work of art.

The boat designer and builder Fred Amor in Canada's own boat "Timeless" is strip planked.

Now, I'm not necessarily a wooden boat fan. I just like the cold moulded construction and the strip planked idea as well, for the reasons I've already stated.
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