white fiberglass sheets from Home Depot?

Glass applied with epoxy was meant. Sorry for the sloppy formulation.

Regards
Richard

 

Oh really, I thought I could either do epoxy OR fiberglass and resin. But the epoxy was prefered singe the fiberglass resin won't be 100% water resistant and the fiberglass adds a lot to the weight.

Is the fiberglass just for extra strength and rigidity?

 

No, no, no..............

do not mix that up!

Epoxy IS resin! And in this case used with fiberglass to stiffen the ply panel and add abrasion resistance. It is absolutely watertight. And yes it adds weight. But that is commonly calculated within the designers weight estimations.

Unfortunately in the US the term "fiberglass resin" or even "fiberglass Epoxy" is falsely used for polyester resins. These are NOT watertight and are NOT to be used on wooden surface! They just do not stick well on wood. (although there are many amateurs here contradicting on that issue, but it is not their money to waste, and they do not have sufficient experience)

Regards
Richard

 

OK, gotcha. Thanks for the clarification.

And I've seen a few debates for and against poly resin, but if Ive learned anything in this lifetime it's to heed the advice of those who know more than I do.

I think I'll go ahead and use the luan and fiberglass with epoxy.

 

Well done.


Not to show up, but to let you know what I am doing:

http://www.boatdesign.net/gallery/showgallery.php/cat/500/ppuser/11121

have your own conclusions........

Richard

 

Wow. There's not a body of water withing 500 miles of me that that thing would fit in.

 

I've built a lot of boats with luan and epoxy. I never use poly resin. That said, tons of boats have been successfully built that way including at least one that made Sail's list of the most important sailboats of the 20th century. But home depot luan is a step down, and you want all the help you can get, sheathing with glass and epoxy will often get you a lifetime of use. I am into 20 years on some of my luan boats. Getting plywood with exterior (black) adhesive is the best idea, you have to look at what is available locally. Doug fir exterior grade is very good stuff if you can find it in decent quality. I have some of that in my older boats and it holds up great, but requires the full fiberglass treatment.

The thing about discount store wood, is the stuff varies a lot, you can get some lifts that are good others that are bad. You have to be your own grader, since the wood isn't certified under any standard that would be meaningful for our use. I've seen a pallet of some stuff, and gone home to draw up a list, returned to the store to a new pallet full of voids etc.. Just recently I came across some luan that was ballance plies! three plies in this case, each one 33% of the overall thickness, mostly no voids. But it turns out to have pretty minimal glue, and it certainly isn't waterproof, what a pity. I am using it in a project, and I expect to pass the boat on to my children.

 

From my experience you will need a good epoxy barrier coat/primer. Many of the marine epoxy producers have one, as well as marine coatings manufacturers. The barrier coat has silica that forms tight plates that helps limit water passing into and through the material covering the fiberglass (gel coat (polyester), vinylester or epoxy. The barrier coats are two part epoxy paints and act as a primer too. Thickness counts here...be generous and make a good barrier. Reme,ber that fiberglass is not waterproof and uncured resin will react with water...osmotically pulls it right in...hence osmotic blisters and pits in older gelcoat. Good work takes time...shortcuts get you short cut.

 

Sorry that is poor advice.

First:
Polyester, Vinylester are laminating resins for GRP structures only! They are absolutely and with no exemption, prohibited in wooden boat building. period

Epoxy and poly (or Vinylester) don´t mix, regardless what some may tell you!

Gelcoat is a nonsense on a wooden surface, neither does it stick on wood, nor does it make any good. And on top of a Epoxy / Glass sheating it does not stick. Then, it is polyester, therefore FORBIDDEN, it would (if it would stick) weaken the surface, nothing else.

Blister does not happen with Epoxy, Osmosis is unknown (although the oxymoron is used often for blister) on any boat. The chemical process though, is not the topic here.

A coat of neat Epoxy on the ply, followed by a layer of glass fabric (not mat), laminated with epoxy, is the proven and long lasting method.
That has to be covered with another two coats of neat Epoxy, then painted or varnished for UV protection and a smoother surface.

Uncured epoxy does not happen when the mixing ratio and temperatures are roughly right.
Water ingress in Epoxy is not possible, cured Ep is watertight forever. (poly is never)

All the miracle coats are not worth talking on such a simple S&G project, and bear the risk, that you screw up the entire structure.

Just do it as they all recommend on the well known homebuilder sites:

EP - glass/Ep - Ep - paint, et voila.

Regards
Richard

 

I'll do just that. I'll keep you posted when I start this project since I'm sure you guys will catch a few mistakes that I'm bound to make.

 

I was also told on here to make sure to use oil based exterior paint over the top, but I've read other places to use other types of paint. What will be the best bet?

 

Almost all paints do well with Epoxy. The cheap exterior housepaint is a well proven choice for example.
No matter alkyd or oil based, cheap is good.

 

I would agree that it is poor advice if you were just putting the epoxy barrier on the wood...my fault for not beeing clear....the epoxy barrier would be put over the fiberglass. The barrier coat is not a bad idea over as you will most likely have uncured resin. Getting 100% cure is hard when it is a DIY project...moisture, temperature control are hard to do when its in your garage. Epox is not always water tight...physical voids, and uncured resin are sure to be there unless under strictly controled conditions. But you know what they say...free advice is worth what you pay for it....from me or anyone else.

 

The barrier over the glass (glass/Epoxy to be precise) is as bad advice as the former. It is not only superfluous, it can weaken the bond of the following coats.

Your statements about watertightness and non hardening Epoxy shows, there is little to no experience with the material, you can provide.

If this:

would be true,
a entire branch would have been gone already. No Glen-L, Selway Fisher or Bateau would have survived.
Even I would have been bancrupt since 30 years or so, because I do not have a better control over the conditions than the average homebuilder.

It is very hard to get a Epoxy mix so far from being good to prevent curing. Poly or Vinylester is easy to screw up by slightly wrong mixing ratios, but epoxy is very forgiving.

Even the complete novice will produce a void free, completely cured and smooth surface with Epoxy when he just follows the recommendations of the supplier (either resin or boat kit/plan).

A completely cured Ep coat IS watertight. And for exactly that reason it is used as a barrier coat on blister repairs on polyester hulls! period

Your "barrier coat" is a joke! A Epoxy coating to make Epoxy watertight....

You are right on free advice.
Unfortunately you did not advise, you drivelled, far off topic.

Richard

 

memelnick..you might want to consult Westsystem.com to learn more about epoxy and yachtpaint.com as these are resourses for sound information from know professional and experts without ad hominem rhetoric.