natural finish

Fiberglassing over plywood and one-off fiberglass methods. See: "Boatbuilding Methods", in the left-hand column of the Home page.

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thaiboats
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natural finish

Post by thaiboats »

Hey,

I have been building boats for a while and have a question about the natural plywood finish I see people using.

I sheathe my boats in Pollyester Resin and paint them. I have heard Pollester and Epoxy resin doesent hold up well under sunlight so I am wandering how these people get away with it. I am thinking they use a UV inhibitor but that product isnt availiable here where I am.

Does anyone here know if I can get away whith just fiberglass sheathing and Pollyester and what can I expect as far as wearability. If I had to recoat every couple of years no problem.


Also what kind of stain should I use , water based or oil based.


Thai Sean

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Graham Knight
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Post by Graham Knight »

Sean, if I understand you right you want to stain the ply then sheath it with epoxy/glass or polyester/glass?
You are right in thinking that neither stands up well to UV exposure, and you'll have to coat the resin with a good UV resistant varnish. You'll need to do some research and see what you can get hold of.
Without the varnish you'd probably be wasting your time, I'm guessing the UV index in Thailand is pretty high and will degrade your finish very quickly otherwise!
There are resins, both epoxy and polyester, that are UV resistant and you may want to look into those.

If you want to stain the wood I'd play it safe and use a water based stain, although I did read that Mark Bronkalla used an oil based stain successfully, he does recommend sanding with 220 grit paper after staining to improve adhesion.
See his comments and method here http://www.bronkalla.com/fiberglass_and_paint.htm
Graham in Shepperton, England

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LG

Finish paint

Post by LG »

I, too, am concerned about the finish coat over the encapsulated exterior. Currently, I am leaning towards a two-part linear polyurethane finish. It offers excellent UV ray and abrasionprotection and is very compatible with epoxy. The problem is, I have never worked with the stuff. Does anyone have any related experience? I have heard it is a b---- to apply. Comments?

bronk
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Post by bronk »

You may want to look at my article in Webletter 52 on spraying LPU. I have heard of good results doing roll and tip off , but this was definitely not recommended for the clears.

Careful surface prep and safety equipment are the major issues.

Actual application was not too bad. I was also speaking with another builder who recently used one of the water reduced LPU finishes and he had a horrible time (matching my fears).

I would stick with conventional LPU finishes (e.g. Imron, Sterling, etc).

The finish still looks good after one summer and part of a winter. Can't wait for spring (20 below here this morning).
Mark Bronkalla
www.bronkalla.com - 50 mph furniture

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Dave Grason
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Re: Finish paint

Post by Dave Grason »

LG wrote: Currently, I am leaning towards a two-part linear polyurethane finish.
...... Does anyone have any related experience?
By "two part" are you saying that you have to catylize it like epoxy? I have not worked with any two part stuff............. but.........

I may be offering help where I have ZERO expertise here, but when I used to sand and finish hardwood floors, we did a LOT of polyurethane applications. The stuff is hard as nails when dry and will last many years without showing much wear and tear at all.

The trade-off is that it is NOT easily repairable. Varnishes can be spot repaired and blended into the old finish but not so with poly. If you DO manage to scratch it, you'll always have a place where the line between the old and the new will show.
Isn't it amazing!! The person that never has the fortitude to pursue his own dreams, will be the first to try and discourage you from pursuing yours.

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Graham Knight
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Post by Graham Knight »

Dave, if you think single pack PU is hard as nails you should try 2 pack, it's bulletproof!
Yes it is catalysed, just like epoxy, acrylic etc..., but that can make it more difficult and hazardous to apply. If you have the neccessary skills and equipment to use it though it's the best (with the possible exception of the epoxy paint which I've used, time will tell...)
Graham in Shepperton, England

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