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martinwellby
09-22-2006, 02:10 AM
I am building a couple of very small rowing dinghies for my young kids. I have seen John B use a colourful fabric on the bottom of a dinghy, and want to know what you can use. Can the fabric be nylon or cotton, and could it be used instead of glass matt or as well as. I am hoping that my 5 year old is going to enjoy learning to row, and anything i can do to make the boat look more attractive is going to help. I realise that a light cloth is not going to be as durable as 6oz glass, but i can keep an eye on it.

Dan McCosh
09-22-2006, 05:37 AM
At that weight, the cloth doesn't do much of anything anyway. You probably could use cotton for the pattern, or eliminate it altogether.

P.I. Stazzer-Newt
09-22-2006, 06:01 AM
I'd not be happy with cotton but I have seen (on competition slalom kayaks);

1. - Thomas the Tank Engine - a polyester duvet set.

2. - Psychedelic 60s paterns from fiberglass curtains.

Lewisboats
09-22-2006, 08:47 AM
The most the cloth might do is help to prevent checking if using a plywood that does in fact check. Most A/C ply will... You can get coloring to add to epoxy to help give it a bit of a gel coat appearance or to better blend in with a colored paint. Using a colored cloth under colored epoxy would be one step further.

Steve

paladin
09-22-2006, 10:03 AM
if ya really wanna have some fun.....
Back in the late 60's........Okiehoma had just changed the law from "dry" to 3.2 beer......beer joints opened all over the place......because alkiehawl wuz served everything had to be fireproof...
every beer manufacturer gave curtains to the joints made of fiberglass cloth, with their advertising printed thereon......we would cruise the beer joints, take away their old dirty curtains, wash them and use them in the layup of canoes...we had made a mould from an old aluminum Grumman 17 footer.......made for some interesting designs....

Thorne
09-22-2006, 10:30 AM
If the design calls for fiberglass cloth, you may want to replace it with something fairly heavy -- or consider laying a thin polyester 'fun fabric' over the glass cloth. Otherwise you may find the boat cracking, leaking, or doing other non-fun things.

Todd Bradshaw
09-22-2006, 11:55 AM
Most of the available nylons and polyesters that you'll find in stores are treated during the finish process with chemical compounds that may keep epoxy from sticking to them very well. Silicone is one common one, and will almost guarantee that sooner or later, the fabric is going to delaminate. Peel-Ply (a light cloth commonly used for squeegeeing onto the outer surface of a composite layup and then later peeled off, leaving a nice smooth surface) is an example of such a fabric and you would be surprised at how many of the synthetics in a typical fabric store can be used as poor-man's Peel-Ply.

Cotton saturates very well with resin, though it soaks up a lot of it, so you would want a very lightweight cotton fabric to save weight and money. It won't have the tensile strength that fiberglass fabric would, so if the boat needs glass to hold it together, I'd add the cotton, rather than replace some or all of the fiberglass cloth with it (fiberglass mat is a different type of fiberglass fabric and is not commonly used with epoxy resin or on wooden boats).

Considering that a clear finish over colored cloth still has to be regularly maintained with U.V. filtered varnish or the epoxy goes bad, the possible difficulties in getting tightly woven colored fabric to drape and lie down properly when laminating and the fact that you'll have no idea of how light-stable the colors are on a random hunk of cloth, the best option by far for a brightly colored boat would seem to be, build it to plan and then paint it.

John B
09-22-2006, 02:42 PM
Thin cotton Martin, its there for abrasion and appearance reasons not structural strength, although its waterproof. As Todd says, it saturates.
And it has worked well for the last few years having been thrashed by about 6 different kids and done countless beaches and a few collisions of the rocky kind.
New.
http://www.imagestation.com/picture/sraid91/p37334c4c2a6a31a3db0991267421e16c/fa5c9b83.jpg

The boy has a matching shirt.( whether it still fits this year I don't know):rolleyes:

martinwellby
09-22-2006, 08:00 PM
Thanks folks, cotton fabric it is (if it fades i can always paint it later). The covering is for abrasion resistance on the bottom over 4mm ply. Johns picture is where the idea came from. I'll have to head of down the fabric shop with my daughter now.
Cheers

bob goeckel
09-22-2006, 09:06 PM
i have used a fabric called nexus cloth from a woodenboat place in wa. state(something... lumber) i have CRS !!!!. it's probably 2-3 oz. i can't recall the location right now as i haven't done any stitch and glue boats lately. they sell books about building the "clancy sailboat " though. the cloth material reminds me of handywipes. works great.

seo
09-23-2006, 11:21 AM
The cloth is NOT there for abrasion resistance. That's what the surface (gelcoat, epoxy, whatever) is for. One proper name for fiberglass is "FRP," which stands for "Fiber Reinforced Plastic," which describes it very well. The fiber adds tensile strength and panel rigidity to the plastic (epoxy or polyester), which is hard, stiff, and brittle.

Todd Bradshaw
09-23-2006, 11:30 AM
Actually, cotton reinforced epoxy resin is substantially more abrasion resistant than plain epoxy. If you don't believe me, lay up a nice big fillet with epoxy and WEST System 403 microfibers (which are cotton) and try sanding it.

Cuyahoga Chuck
09-23-2006, 11:50 AM
I don't understand the reason for doing the bottom. Most of it can't be seen in the water.
The boat in the picture is in a pool. But, in a more natural venue the bottom will incurr scrapes and gouges which will be hard to conceal because of the pattern.
Why not decorate the seat tops or the upper exterior of the hull which is less inclined to be damaged?