more on glass repair

Wonderful stuff, especially for Royalex repairs and for sticking dissimilar stuff together.

PC7 will NOT wet out cloth - I suppose that an open basketweave roving could have PC7 smooshed into it, but the thick mixture would bond to the fibers rather than saturating them.


“epoxy resin”?
So, are PC7 and the like straight “epoxy” (best used for filler/adhesive for structural repairs), while the thinner stuff for wetting-out cloth are “epoxy resins” (must be used with fabrics or other strength-giving additives)?

It seems the word “epoxy” is frequently used for a variety of different products. I’m sure there are many different epoxies, but I also suspect that the term is often used wrongly (as I was recently corrected for calling a urethane adhesive an epoxy).


PC7 - Label Says “Epoxy Putty”

so . . .
So “epoxy putty” and “epoxy resin” are different things for different applications, even though many users may just use the word “epoxy” without clarifying the distinction? (and may or may not be thinking of other resin-catalysts or 2-part adhesives)


Chemist needed

– Last Updated: Jul-16-05 8:40 AM EST –

I haven't dug out my "boat building" books that I have to see what seperates by definition and or chemistry of an epoxy resin vs. an epoxy an epoxy putty. Or for that matter what seperates a two part polyester from a two part epoxy. If my memory serves me well it has something to how the molecular chains are formed and the different properties they have from each other. I have used both and outside of the fact that the resin is in a liquid molasses state and the putty is in a peanutbutter like state when you use them, I will leave it to a chemist to explain the differences. The putty can not be used on the cloth as it won't penetrate and soak into the fabric which is necessary to create a reliable lamination/bond. I use the putty to fill holes, gouges, chips or to adhere a small object. The liquid resin for laminating and bonding the cloths. The only cloth I have heard that epoxy doesn't work well with is chopped mat (short loose individual fibers that are lightly bonded to each other in a random arrangement) Polyester resins will work with chopped mat. Your cheaper built boats (both power and paddle) will often be built with polyester resins and chopped mat cloth. Those materials are much cheaper, require less labor to lay them up and tend to be much heavier and are more brittle in terms of flexing and impact. Positive side is they are easier and cheaper to repair

Surf boards
I haven’t actually used this technique on any of my own boats yet, but see no reason at all why it wouldn’t work. If I am not mistaken this is basically how some surfboards have gotten their graphic images built into the final product.

for an “epoxy” tip?
Thanks TR,

What would you use for fiberglassing a paddle blade - polyester resin, or is epoxy resin always better?

And, to add an “epoxy tip” - would you use an epoxy resin or an epoxy putty. And, with or without some cloth pieces, silica, carbon powder, etc.?


Here you go…
Chemical term describing an oxygen atom bound to two linked carbon atoms Generally, any cyclic ether, but commonly applied to a 3-membered ring; specifically, a three-membered ring is an oxirane, a four-membered ring is an oxetane, a five-membered ring is an oxolane, and a six membered ring is an oxane; oxiranes are commonly produced from peracids acting on alkenes. Epoxys are important chemical intermediates, and the basis of epoxy resins (polymers) formed from epoxy monomers.

Shoulda said so sooner!
I just sent some old shirts off to Goodwill or some such.

Yes, I 've used the putty to fill in dings in a glass boat. It worked. Seemed to take awhile to cure. No, it won’t fill in glass cloth. It has a off white color. Sort of match the hull bottom but not quite.

I recently used West epoxy and 2 hour hardener with filler to modify a waveski. This cured pretty fast and seems to provide a harder and shinier surface than the putty but it has a weird flesh color (the filler) and had to be painted over.


Just Actually Finished Patching A
stress crack on my carbon fiber paddle. Used West Epoxy over 6 oz s glass. Use the fast harder because the epoxy tends to run a bit before hardening. Or, make sure to use just enough to soak the glass, let it dry, lightly sand and then do another think layer of epoxy.

The light filler used with the Epoxy is just that. It’s for fairing and does not provide much structure integrity. Very easy to sand down and smooth. I used this to fill in the voids of the waveski foam, sand down and prep for putting on layers of glass. The silica is heavier stuff and is used to fill and provide a structural stronger bond than light filler. I believe it’s application for something like a fillet for where two surfaces meet at an angle. The silica filler can smooth the angle, make a strong bond and than a layer of glass can be added on top. I have the silica but have not had an opportunity to use it.

If you’re repairing a badly cracked paddle, you can open the crack, epoxy and glass one side, let dry, go back and fill in the crack with just enough glass and epoxy to created thickness. I think here, the silica filler may also be possibly used. And, then layer more glass over the filled crack over into the surrounding area and epoxy. A more finished surface requires you to go back and lightly sand everything and then a thin coat of epoxy again.


If only faring foam prior to glassing
save some time ( watch and life) and $$$ and use drywall mud … fills fast , super smooth and can be ‘faired’ using a sponge. This stuff will bond fine and will not attack anything… not the best for structural but great as above for fairing. Otherwise West 410 is great.

Beware the Print cloths … resin sponges. Resin absorption = 5.7oz. 18 X 18 cloth ++ and really do nothing for strength… increase impact strength though… up to 50/ 50 poly cotton o.k. Sorry to be a killjoy. If using it anyway babysit it 'till resin kicks in because it can creep easier than glass. Cut a little shorter than project as it gets ‘larger’ once saturated.

Print cloths question

– Last Updated: Jul-16-05 10:02 AM EST –

If one were to resin in a print cloth for decorative purpose only, would the swelling of the cloth still be an issue if it were an all synthetic material? Something like rayon or nylon for example. I am well aware it would offer nothing structually, but wondered if the swelling of the fabric might have more to do with what the fabric is. If it is something like a 50/50 mix of poly-cotton I could see the cotton side swelling up though. I've always thought it would be wild to do a whole deck or hull this way and wondered if it could be pulled off without running into a string of nightmares.

The Drywall Mud trick works great as I have made some simple molds out of foam then mud and faired them. Covered that in shrinkwrap and glassed over that. Glass/resin doesn't stick to the shrink wrap so pops off when cured. I use the shrinkwrap they sell at Home Depot to tape over windows and shrink to make a poor man's storm window for those of us in the NE. When molding a custom seat for a boat with this technique I once tried polyurethaning a pariscraft mold then waxing that with a Carruba based wax as a release agent, but the glass/resin stuck to it badly. Pariscraft (they use to use it for cast on broken bones and can still be purchased at Craft Shops)is also easy to work with and great for shaping and making one use only molds. In retrospect I should have layed Saran Wrap over the mold then glassed it and that would have made it pop off without issue.

Follow Sing’s directions

– Last Updated: Jul-16-05 9:02 AM EST –

My suggestion would be epoxy resin. I also cracked a paddle and repaired it in an almost identical way. The only other other thing I did was to lightly sand the area where you are going to glass first, then wipe it with a rag that has a little acetone in it to prep the area you are going to glass. I wouldn't wipe it with soap and water as that might leave a film that could interfere with a good bond. Any others have knowledge or suggestions on how to prep an existing glassed surface that you are about to glass over?

Out of curiosity what is the chemical configuration of Polyester or Vinylester resins and what makes the epoxy configuration generally thought of as the superior one.

Yes, yes and yes
You can patch from the inside, but I usually patch from both sides. After grinding out the damaged glass (ALL of it) and feathering the edges from the outside, I’ll lay in a layer or two of glass on the inside to create a form for the rest of the patch. Next, I layer glass on the outside to match the original hull glass thickness. I use epoxy exclusively for repairs.

Gelcoat WILL adhere to epoxy well IF the epoxy is FULLY cured. I accellerate the cure by using heat lamps to warm the patched area to 100-120 degrees F or so. Elevated temps cut cure times dramatically and increase the strength of the epoxy. I’ve found that I can apply gelcoat successfully the day after patching if I heat the patched area. Before applying gelcoat, the patch must be cleaned (I prefer lacquer thinner for this) and sanded with 80-100 grit sandpaper to provide a better mechanical bond.

Marine paints will work fine over epoxy. Interlux Britesides is sort of the standard for use on wood/glass kayaks and will work fine on fiberglass boats.

PC7 for hull chips
PC7 is available at a lot of local hardware stores and I have seen it in three colors, black, grey and white. I have used it to fill chips in some of my hulls. Since many hulls are white I found it a close enough match to the gell coat to use and just leave it like that unless you are trying restore it back to a manufactures’ appearance.

Yarnellboat … epoxy tip.

Have to scroll way down .

Not the best thing because…

– Last Updated: Jul-16-05 3:03 PM EST –

The cloth itself will not really uptake the resin and for one thing might not go 'clear'. Second and more importantly the these type of cloths will act as interlaminar release plys..... meaning they will delam the first hard hit or even if you just put a little weight on them ( rack straps ). The 50 /50 is about the practical max to go with synthetics. But even this should be for cosmetics unless on a over foam where it will not be so much of a problem. We did a couple boats with cloth decks AND hulls.

Trmoraine .... next time you make something like that .... you could use PVA sprayed on to use as a release..... for plaster type stuff you would have to build up a couple coats because it is so porous.

It's the styrene in the ester resins that breaks down the binder in mat .... can use Epoxy if you 'had' to but why bother.

Decorative paddles question

– Last Updated: Jul-16-05 4:48 PM EST –

How are some companies (I think Swift is doing it) are putting designs on their paddle faces? Are they putting a fabric like layer with the graphics down first, then glassing over that and allowing the translucence of wetted out glass to allow you to see the design? Or is that a special decal like pattern that works with the glassing process that is being used?

Sounds like if you are going to use a fabric for decorative reasons only, it should be made with a fabric that will absorb resin to prevent delamination possibilities.