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Old 18-05-2007, 16:33   #16
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Aloha Sean,
Canvas and paint were used on many boats and I had a friend who did it on his 55' Marco Polo. It is described very well in "Complete Amateur Boat Building" by Michael Verney.
I don't use it because of the rain factor (120 plus inches a year) we get here and any wear or splitting of the canvas can cause it to leak in freshwater. It needs to be checked and painted more often than the 10oz glass epoxy resin method.
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JohnL
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Old 18-05-2007, 22:16   #17
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Hi Sean

Stick with the Fibre glass and cloth. I did exactly what you are proposing 21 years ago. The commercial boat I had, had canvass and paint and a small dog house cabin. I redid it using the technique discribed by SkiprJohn. I used 1/4 " G2S fir for the sides and 5/8" for the roof cambered over sawn KDfir 2x3 (I used the roof to store an 11 ft. Inflatable) I put 2in. Polystyrene foam in the walls and cieling. Put a teak veneer on the inside walls and thin vinyl coated white ceiling sheet on the celing with mahogany battens. This was still in good condition when I last saw the boat 5 years ago.
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Old 19-05-2007, 01:08   #18
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I would agree with SkiprJohn and Lancerbye. There is a reason that canvas and paint is not the standard anymore. There are better alternatives out there. You need to keep the top light so if you go with 1/4 ply I would probably space the beams closer together say 12 inches. With closer spaced beams they could be somewhat smaller in dimension. If you are not going to be walking around up there SkiprJohns wider spacing would be okay. 3/8 ply would also be an option for a little more load carrying but 1/2 is starting to get to heavy don't even consider 3/4. Aside from the fact you would have a hard time bending it to the camber of the beams. The cambered laminated beams will provide the support for the thin plywood.
Now this is alot of beams to laminate up so I think there is a better alternative. Stringer frame construction. Widely spaced laminated beams with stringers running fore and aft. The stringers do not have to be laminated and would be something like a 1x2 laid on edge and notched into the beams. It is like aircraft construction. The Searunner trimarans use this type of construction. The deck and cabintop on my 40 is 3/8 ply with around a 40 inch beam spacing. Stringers running fore and aft are about 10 iches apart. The cabintop is 12 feet wide. There is no noticable deflection when walking around on the deck or cabintop. The cabintop has a noticable camber and the decks a very slight camber. Don't try a "quick and dirty" flat top it will look like **** and will have to be built out of heavier materials. One more thing, if you use fir plywood you have to use cloth and resin on the exterior. Trust me on this one. Check out Defender Marine they have several types of cloth available at decent prices. There are other types besides glass fiber that will do the job. 6-10 oz will be heavy enough. If you are interested in this type of construction PM me and I can get the exact dimensions, beams and stringer spacing ,etc.
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Old 19-05-2007, 01:29   #19
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Quote:
Wow! I'd like to find out about using painted canvas
NOOOOooooooooooooo. That was a very very old school way. You don't ever see it done anymore for a very good reason. There are better methods and materials these days. It is called fiberglass. The old canvas way was a long time before Fiberglass was invented. And anything from paint to pitch was used to waterproof and stick it down.
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Old 19-05-2007, 02:45   #20
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Quote:
Originally Posted by ssullivan
Extra info:
...I just spoke with a guy who did up a BEAUTIFUL one for some people in NY...
...The object will be to make as cheap and light (and WATERPROOF!) a structure as possible as an extension to the wheelhouse...
...I need to find the cheapest and lightest material that will be waterproof and hopefully be able to take a capsize without detaching from the vessel or falling to pieces..
How did the guy you spoke to construct the beautiful one ?

Cheap, light, & waterproof are often mutually exclusive, much like the old saw:
There are three important qualities that apply to any construction job (cost, quality, & time). The client gets to choose any two.

Any significant change in a boat’s designed superstructure, should involve a significant re-engineering study - not something normally associated with cheap & amateur. I fear your specification for “capsize safe”, may prove a self-fulfilling prophesy.
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Old 19-05-2007, 10:14   #21
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Quote:
Originally Posted by ssullivan
Hi Andy,

Wow! I'd like to find out about using painted canvas. Any links? More description? I'm a huge fan of old ways of doing things.
Yo Sulli,

as you specified CHEAP, ergo my suggestion for the old paint-and-canvas method, which has been around for about a hundred years or more. A search on traditional methods should find something, as it was still being used on production boats into the 60's. Talk to some old fisherman in your area--it's probably what they've used on their workboats for years.

Yes, many modern materials offer improvements, but they're a lot more expensive--and often bad for your health and the environment.

best, andy
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Old 20-05-2007, 06:51   #22
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Hi Sean,

I have seen ply,foam,ply used before using cheaper urethane type foam's.

Makes a well insulated, stiff light panel, and may not even need beams.

Insulation would be good in the cold as other method's could have a condensation problem.

Used for hull's and bridgedeck panel's, so compound shapes can be done.

Given uses the method,

Ron Given Catamaran Design, sail and power, New Zealand and Noumea

And Malcolm Tennant uses it as well and makes mention here.

Welcome Tennant Design

Welcome Tennant Design

Good luck,

Dave
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Old 20-05-2007, 08:21   #23
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Originally Posted by cat man do
Hi Sean,

I have seen ply,foam,ply used before using cheaper urethane type foam's.

Makes a well insulated, stiff light panel, and may not even need beams.

Dave
Yo Dave,

unfortunately lightweight composite panel construction is one of the most expensive and labor intensive methods used in boatbuilding.

best, andy
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Old 20-05-2007, 15:28   #24
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Yo Dave,

unfortunately lightweight composite panel construction is one of the most expensive and labor intensive methods used in boatbuilding.

best, andy
This method can be as cheap or as expensive as you'd like.

Temporary chipboard frames to hold shape of the structure.

The ply "could" be cheap Luan "door skin's" [i'd prefer 4mm marine]

The foam can be white polystyrene, the thicker the foam, the stiffer the structure, and the better the insulation.[i'd prefer blue polystyrene or HD urethane, no need for divinicell or termanto]

There will be fewer deck beam's required, making a cleaner look, and saving weight and $$$.

It will use marginaly more resin than straight ply construction, but the less deck beam's and insulation should pay off.

This is a strong teqnique, think insulated truck panels.

In the long run, this is not much more labour intensive than other method's,your own labour is free, yet will have many more benefit's, like more professional look, cleaner interior and warmer in winter, cooler in summer.

Dave
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Old 21-05-2007, 00:38   #25
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I would agree with the previous poster who suggested timber framing, marine ply skin and then fibreglass to finish.
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Old 21-05-2007, 01:54   #26
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I would definitely go with a ply/foam/ply construction. House frame construction is quite heavy, just seems light cus you are working with one 2x4 or sheet of plywood at a time, but that weight adds up in a hurry. You can get 4x8 sheets of rigid foam insulation for about $20 a piece, and cut some 1/2 x 2" lath to go around the edges, and 1/8 luan plywood for the skins. The trick is to get good adhesion between the skins and the foam, otherwise the structure doesn't work. You can use construction adhesive, ore wood flooring glue, etc. To put pressure on the panel as it is setting up, put something like a large kiddie pool, or make one frome a frame with some heavy plastic and fill it with water. Then epoxy the panels together, edge to edge, and fiberglass the whole thing to keep the elements away from the cheap wood. Your problem will be the roof - unless you have supports in the middle, you would need something like 2x10's every 2' to support snow or somebody walking on it, and it would need to be crowned to shed water. Foam sandwich panels are very strong, and the insulation is built in, though only about R8 or so.
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Old 21-05-2007, 05:19   #27
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Thank you very much for all these alternatives. Wow. I guess there are quite a few ways to do it. Just took at look at some of the prices for resin and cloth - OUCH! Several thousand dollars for this structure.

I just got back online after another hundred miles or so, so pardon the late reply. I have a couple hundred more to go before I'm in a final destination somewhere in Maine. Once we find a good harbor to work from, I'll be online asking a few more questions about these thoughtful and helpful responses. Thank you again for the information. I'll be thinking about it as we make our way to Maine.
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Old 21-05-2007, 10:40   #28
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I'm going to disagree with the plywood proponants. Plywood is one of the least desirable materials to use in boat construction, IMHO. I still think that good boat building foam (not polystyrene) and glass laminate would be the ideal. Light, strong, easy to construct, durable and warm. I would build it in panels and then join them in place to save the cost of a crane rental.
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Old 21-05-2007, 10:44   #29
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Quote:
Originally Posted by GordMay
How did the guy you spoke to construct the beautiful one ?

Cheap, light, & waterproof are often mutually exclusive, much like the old saw:
There are three important qualities that apply to any construction job (cost, quality, & time). The client gets to choose any two.

Any significant change in a boat’s designed superstructure, should involve a significant re-engineering study - not something normally associated with cheap & amateur. I fear your specification for “capsize safe”, may prove a self-fulfilling prophesy.
Hey Gord,

Are you familiar with these boats?

Did you know they are designed to carry 5000+ lb loads? They are workboats, not pleasure vessels. Their stability curve is specifically designed to withstand coastal conditions, and some have been designed to withstand offshore as well (they change the hull shape and bring up the topsides on those for fishing pelagic North Atlantic fish). These are the boats used to fish the waters in the North Atlantic well past Nova Scotia. One incident I saw where someone DID overload one was putting 14,000 lbs of lumber on the back of a 30 foot version of this boat I'm looking at. He had made it quite far up into New Brunswick and had a tropica storm come by. The addition of the 14,000lbs, combined with several barrels of diesel, crab pots and a lengthening of the wheelhouse conspired to cause his vessel to "pitch dangerously." (Did you know my CAR only weighs a bit under 2000 lbs?)

The captain from this 30 footer made a more crucial mistake than overloading this boat. He sat her so low in the water that the self bailers from the deck admitted water. So... he plugged them up and used a bilge pump to pump water off the deck. His deck was also not watertight. The boat did NOT capisze even with 14,000lbs of items aboard in 20ft seas in tropical storm Juan. It was lost due to downflooding from the scupper/non-waterproof deck problem.

So... I'd like to say that given that I'm getting the 40 foot version of this same boat (think more payload ability): How could the boat *not* handle an extension to its existing wheelhouse, when I could carry 2 of my cars stacked right on the back of the boat without even coming close to being overweight?

PS: Of course, I'll do my own stability testing (a la 50 gal drums)
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Old 21-05-2007, 12:02   #30
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You ask “… How could the boat *not* handle an extension to its existing wheelhouse …”; when the engineering question would be how could the boat handle an extension.
The boat you thumbnailed earlier, was obviously carrying a deck load (traps), which implies that you could substitute an equivalent structure.
I think the available evidence suggest that an engineering study might be optimistically justified, in proving your concept.

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