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Old 29-07-2017, 09:17   #16
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Re: Glass over ply.

Anybody?
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Old 30-07-2017, 05:23   #17
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Re: Glass over ply.

Looks like Oregon, also called douglas fir. The smell would be a giveaway.
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Old 30-07-2017, 05:39   #18
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Re: Glass over ply.

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Originally Posted by honey badger View Post
Whilst hacking out some dead plywood on the catamaran I am restoring, a thought sparked from my epoxy saturated synapses.

So with the advances made in modern epoxies thanks to the aerospace/military/and racing worlds.
Could you forego the use of glass cloth for hull sheathing? I realize that there are some jobs that will always require glass.

Asking for a friend...
Depends what the purpose of the ply coating is.

If the sole purpose isto seal out moisture, then just resin is fine. (If the resin is epoxy, then it Must be protected from UV with some other overcoat.)

If the intent is to add the strength of composite construction, then glass is essential.
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Old 30-07-2017, 05:52   #19
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Re: Glass over ply.

The wood in your picture is clear vertical grain Douglas fir from NW USA or Canada.

One layer of 10oz fiberglass with epoxy resin has a primary function of protecting wood surfaces from abrasion. It is not meant to be structural.

The rot on your catamaran is due to checks, splits, and/or chips in the paint, resin, and/or fiberglass. The hull/deck joint and beam troughs are especially vulnerable to opening enough to allow water to penetrate. It starts with salt water, then eventually fresh water. The water gets between the layers of ply and the rot starts inside.

Epoxy and paint alone can develop microscopic openings that will allow water inside. A layer of e-glass helps to avoid chips and cracks as well as providing adequate resistance to abrasion. Any place that has a better chance of knocking into something (earth, dock pilings, etc.) or may open due to twisting (beam troughs, lashing points) should be reinforced with bi-axial e-glass, and/or extra lumber and plywood to avoid openings that will allow water inside.

Since you have had Wharram's before, you can remember where the extra reinforcements and glass were placed. All Tikis are sheathed in glass and have extra reinforcements in certain areas. The Classics need this as well, but you will not find that data in the plans. You need to do it yourself.

I am a big proponent of e-glass on the outside and water-based latex exterior paint on the inside of the hulls. Latex is a one way barrier that will allow any trapped water to escape. Epoxy will seal the water inside the layers if you use it on the interior.
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Old 30-07-2017, 05:59   #20
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Re: Glass over ply.

Quote:
Originally Posted by UNCIVILIZED View Post
When glassing things like hulls, does anyone have experience flow coating, in order to fill the weave of the glass, & minimize sanding & fairing? I've done decks & other horizontal projects with this technique, but never hulls. Though I've always been curious about it since I heard Kurt Hughes mention it in passing.
If you've done it much, it'd be interesting to hear about your experiences doing it. And the info may also help the OP.
I mix light weight .25g micro balloons into epoxy until I get it thick enough to not run. I spread it into the curing weave with a large trowel, pressing just hard enough to fill the weave but not leave a heavy coat (I can still see the glass after application.) It sands very quickly and easily. It can be left thicker where needed to fill small depressions or overlaps. I have used this successfully on inverted surfaces.
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Old 30-07-2017, 06:00   #21
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Re: Glass over ply.

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Originally Posted by Captsteve53 View Post
Note in your comment you said Polyester ? Should be Epoxy if going over ply or timber, if for some reason that is out of the question then Vinyl-esters would be better than Poly

Cheers Steve
Pretty much every production builder that has made a polyester FRP boat has glassed cloth over ply or balsa with polyester. Done properly (and the procedure is virtually identical as with epoxy), polyester works just fine, having about 80% of the adhesion strength of epoxy, but needing about 10% of it's adhesion strength to perform reliably.

As with any resin, if moisture gets into the wood core, the bond will fail.
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Old 30-07-2017, 09:03   #22
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Re: Glass over ply.

Food for thought thank you all. The cats name was Anike. I am thinking this boat was built in the northern hemisphere originally. The hardwood of the stem posts does not look local either.
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