Glen-L.com

i just watched Glen L's DVD on fiberglassing. it was a great DVD but it left me with a few questions. It does not address the putting multiple coats of cloth. Is this ever needed. I am building a "Scooter" and it will be used mainly in back bays of Texas. There are lots of oyster reefs where I fish. Do i need to put multiple layers of cloth on....or use a heavier cloth? Also I was told to make the last lap of cloth from the sides onto the deck. does it matter where the laps are. The DVD said it does not and I believe it over the person that told me to make the last lap onto the deck. One more thing....what kind of paint do yall recommend. thanks, jason.

Looking at it I think one layer is plenty. The bigger issue, in my mind, would be the paint. Are you going to keep this trailered? If so, the teflon bottom paint stuff is what I would use. For the deck I would want something non-slip. Someone here mentioned making their own non-slip with bright-sides (I think) and sand or microspheres. A search for non skid is sure to turn up something.

_________________
Bill

I told my wife we needed a three-car garage for my projects...she told me to ask her for permission next time before I buy a house.
http://www.unitybuild.net

The depot(orange box store) has an additive called shark skin to make concrete/porch /deck paint non-slip.

I have used this on my concrete porch.

I have also painted a coat of paint on my ramp for my shed,used my portable sandblaster to "spray apply" sand evenly to the wet paint,then applied another coat of paint over the sand after the first coat dried.

When I worked a boat trailer co. , back in painted trailer days(1974),That's how we added non-slip to the foot ramps on the trailer(wet paint,sand,wet paint)

The sand is, as expected, a bit rougher than the shark skin

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Boat building can best be defined as an endless series of
tragedies obscured by the occasional miracle, followed by a good bottle of beer.

Don't Dream Your Life, Live Your Dream

Wherever you bought the epoxy, you can get sand (silica) specifically for non-skid. If you have a large area to do and are using epoxy resin, look around for ground walnut shells. They're used as a bead-blasting abrasive, and epoxy bonds to them really well.

The idea behind using a single layer of 6 oz cloth and epoxy is simply to provide a waterproof barrier. The epoxy does this and the cloth counters the epoxy's brittleness and provides a bit of abrasion and puncture resistance so the coating survives launching, beaching, trailering, etc.

If you want to use more epoxy and cloth you won't be doing any harm but a boat designed for a simple epoxy sheath derives its strength from the structure and not from the sheathing. JMHO, but I think it's just throwing money away.

Of course, then there's the issue of filling the weave before applying the next unit of cloth, and doing it all while the previous layer is still 'green' so you get a primary (chemical) bond rather than a purely mechanical one. And then there's amine blush to keep in mind as well....

_________________
-Brian

"Do or do not. There is no try."
- Yoda

the main purpose of the fiberglass isnt to make the boat waterproof it's for abrasion resistance.

Hehe...now here's an old boatbuilders' debate.

If it were abrasion resistance alone, I think that polyester resins would be more than adequate and at far less cost. This would also allow one to easily wet out a much heavier cloth at the waterline and stem, where impacts are most likely.
Unfortunately, polyester resins aren't inherently waterproof and require a barrier of epoxy to seal 'em up as part of the bottom paint system.

One of my projects is to install a sacrificial cutwater on the stem of my kayak because the glass keeps getting scrubbed away from beaching it. I have some Knytex left over that I'm thinking of using - it takes a ton of epoxy to wet out but it does provide way more abrasion resistance than just cloth.

But you know, I think the original builders of baidarkas and other skin-on-frame boats would have loved to have epoxy....for BOTH traits !



Good idea ! Sounds like it worked pretty well ?

_________________
-Brian

"Do or do not. There is no try."
- Yoda

polyester also has some issues with sticking to plywood (there is some debate as to how to make it stick or IF you can make it stick). That is one of the reasons for the switch to epoxy.

You know, I thought that about the poly/wood bond too, until I built for a guy who used exterior ply as his deck coring in 24 to 29 foot cabin cruisers. The trick I learned was to thin the first coat with styrene ~10%. The resin is catalysed at 4% of the thinned volume, not the resin content. This goes on as a 'flood coat' specifically to soak into the wood. The 'trick' is to plan the work so that the first unit goes onto the flood coat while still green.

His engine mounts were solid 8/4 Doug Fir laminated with bearshit (poly resin thickened with chopped strand) and they secured Volvo D6s, both singles and twins. I don't recall whether the bilge stringers were ply or solid, but I think they were laminations of plywood. Having personally (and skeptically, I might add) built them, I have been surprised at how much value these boats hold over the years.

Most powerboat transoms (if not all) are laminated from plywood as well.

Then there's the most common coring in glass boats, bar none: end grain balsa. And when most production builders need a hard point in the core for winch pads, portlight framing, etc; the coring gets replaced with plywood. THAT is about the only application where exterior ply is absolutely inappropriate IMHO.

I think the biggest boost in favour of epoxies is simply how user friendly they are: no vapours (as compared to styrene based resins), wider mixing tolerance, and MUCH less specialization in individual products and applications. Poly layups with a skilled crew and a good mold will always be more cost effective than an epoxy build.

That said, does anyone know of an uncored epoxy hull design ?

_________________
-Brian

"Do or do not. There is no try."
- Yoda

This is good info, thanks for sharing

So, with ALL of that said......does anyone think i need to put more than one layer of cloth for abrasion resistance against oysters.

Personally, I wouldn't bank on a single unit of 6 oz cloth providing much serious resistance. I just finished sheathing a cedar punt and even the trolling motor left marks in the glass. Granted , the epoxy will continue to harden a bit more...
If you expect to be scraping it, I'd definitely beef it up a bit (at least the stem and keel), but that's just my .02

Has anyone tried using hard undercoating in wear areas ?

Mine has a flat bottom and I've already found that shape takes quite a bit of abuse on beaching: if there's one rock sticking up then the entire width of the boat bears down on it unlike a conventional stem and keel touching the beach first. I don't know if your tunnel hull would be the same but a unit of heavier cloth on the bow might be a sound idea if you're going to tangle with oyster shells.

I've been using carpenter's chalk to tint epoxy, and it seems to make it harder as well. An additive like that or powdered graphite (sold as a dry lubricant) might help to both fill the weave and protect your project.

_________________
-Brian

"Do or do not. There is no try."
- Yoda

I dont see a problem with putting more then 1 layer of glass on the bottom. Or you could put extra strips just on the areas you think might need extra protection such as along the keel.

I'm wondering if a person could wet out two layers of glass at once?

You mean two dry layers?

Or one after the other?

That's what they do when they laminate up a fiberglass hull,one after the other.

_________________
Boat building can best be defined as an endless series of
tragedies obscured by the occasional miracle, followed by a good bottle of beer.

Don't Dream Your Life, Live Your Dream

lay two layers of cloth on the boat at once and then wet them both out together

Might work but I'm not crazy about the idea. I think I would want a full weave fill on the first layer before putting more on. If both layers were put on at the same time it seems that you would run the risk of having dry areas between the two layers. Glass can be pretty abrasive on itself so it wouldn't take too long to wear through. It might also be more difficult to see clarity on a good wet-out to avoid air bubbles and dry spots. As a true amature...I wouldn't do it.

I'm sure one of the glass experts here will have an opinion on this one.

_________________
Bill

I told my wife we needed a three-car garage for my projects...she told me to ask her for permission next time before I buy a house.
http://www.unitybuild.net