No Gel coat

CBPayne

Been Around the Block
Ok I did three layers of fiberglass matt and one layer of the cosmetic fiberglass but forgot to add the wax aka the gel coat. The place I bought it from said it would always stay tacky if I didn't add it. In all these fiberglass seat write ups no one ever says anything about the gel goat. Im going to sand it anyways to get rid of some booboos but should I add another layer with the wax before I add the dolphin glaze? As of now it is about an quater inch thick. Im going to weigh it when I get done. Thanx
 
I am guessing that you used a poly or vinylester resin, correct? Those resins do not need gelcoat to cure, only the proper raio of MEKP and make sure it is mixed thoroughly.

If your fiberglass is 1/4" thick for your final product, you have made it decently thick. Most likely a lot thicker than it has to be. What is the process you used to make the part?
 
I used poly resin. I basically shaped blue insulation foam like I wanted covered it in latex paint. Then I cut my strips of fiberglass. I mixed 2% hardener with my resin and spread it on the mold then added the strips of fiberglass. The first time it worked the best cause it was about 75 to 80 outside and it was sunny. All the other times it took forever to dry because I started to late and the 2% was enough with out the sun and the added cooler temps.
 
Poly will gum up your sandpaper all day long. The only time I use it is when using tooling resin to make a mold. Otherwise, I still to epoxy resins. And with epoxy resins, you can apply it directly to your foam without it melting, FYI. A little late in the game to know that though.

You will have move success if you fill with some fiber reinforced Bondo, then sand...or plan on going through packs of sandpaper.
 
I'm pretty sure I can't get epoxy resin locally. I have orbital sander, but yea I know what you mean by gumming. Maybe I could get epoxy at place I bought the dolphin glazed. I'm going to use the dolphin glaze because I already have it and the guy at the paint shop said its flexible. I'll take your advice into consideration next time I do anything with fiberglass. Right now I dont have a lot of funds to buy nee products. I'm pretty sure I got ripped on the poly resin. I've read that the epoxy resin can be more expensive. I paid $80 for a paint can of this stuff.
 
I use US Composites resins for my plug making

http://uscomposites.com/epoxy.html

Ends up being about $160 for 3 gallons of total resin (2:1 mix) with shipping.
 
Poly is perfectly fine with what you are doing.

No need for epoxy. Especially with your part being so thick.
 
Another couple of nice things about epoxy:

*Resistant to most solvents, including gasoline
*Adds additional structure to the 'glass, so you can use less of it and have the same strength
*Doesn't stink to high heaven
 
Like I said no epoxy this time or for a while...Im trying my hardest to keep this build under 5k.
 
J-Rod10 said:
Poly is perfectly fine with what you are doing.

No need for epoxy. Especially with your part being so thick.

lol, I dis-concur...I avoid poly-vinylester whenever I can. It is heavier and more prone to cracking in my experience, especially if you are putting too much resin in your part.

(I know, I could talk all day about composites, too bad it is not my day job -- then I would probably not)
 
If you do your lay ups with an unwaxed laminating resin, oxygen in the air inhibits the outer surface - if your whole part is gummy, no matter how much you sand, then you might want to check your resin : MEKP ratio as that would indicate an undercatalyzed part.
An unwaxed resin system allows multiple lay ups without having to solvent wipe and sand between subsequent lay ups - great for larger projects or if you have to build a part in stages.
By the way, you can get waxed and unwaxed gelcoat (I use unwaxed).
To get the gummy outer surface to cure if it isn't undercatalyzed, wipe a coat of PVA (available from your fiberglass supplier) over it and let it dry overnight. PVA is water soluble, so it just washes off - or wet sand to keep the dust down and the PVA will wash off during sanding.
I guess you could give it a light coat of fast-drying paint like lacquer and sand the part but I've never tried it...
Regarding polyester versus vinylester versus epoxy, the stink of the ester-based resins is pretty bad; I wear an OSHA 2-stage respirator made to trap solvents, no matter what resin system I use (including epoxies) and try to dilute with added air - open a window in your shop occasionally. I also used to run 2 passive air scrubbers but never really found they worked all that great.
Each system has its pluses and minuses and keep in mind there is a big difference in resins from different manufacturers and even in the same family of resins.
Pick the appropriate resin for the job. I use iso-polyester for most of my lay ups for better fluid and environmental resistance, has less shrinkage, shows better mechanical strength and I believe a lot of the marine builders use it these days for the same reasons. I paint the inside surface of my parts because all resin systems are a little bit porous and most of my parts are on street bikes these days, so might as well make them last, right? The downside is the cost - about 25% more than a basic polyester.
I don't use vinylesters all that often due to expense, but they work great for fluild resistance, will work with carbon fiber and also offer significantly better mechanical values over a polyester system - the best ones (eg, Derakane) approach epoxy resins as regards their mechanical strengths.
Epoxies tend to be a little more difficult to use, have pretty high cost but offer great mechanical strength. I use them for the majority of my aircraft work and most repairs regardless of the part (better safe than sorry, right?). Just because you can't smell them (very much), don't think nothing comes off the lay up. You can get sensitized to epoxies by both inhalation and contact. Symptons of sensitization include difficulty breathing and puffy eyes, while contact sensitization results in dermatitis - which I'm getting over right now even though I wear good quality disposable gloves.
Epoxy sensitization got to be such a problem in the homebuilt kit plane industry, at least one manufacturer redesigned his product line so the parts could be bonded together with vinylester - no, you just can't switch willy-nilly.
IMHO, sounds like you're doing a lot of the right things, learning a lot and trying to build a few unique parts for your ride - kudos to you!
Just make certain you wear the correct personal protection regardless of the resin / part / whatever you're working with.
Regards,
Pat Cowan,
Vintage Motorcycle Fiberglass
 
Paco,

Paint actually works quite well for sealing off air. I hit all my parts with a quick coat of Krylon as soon as I finish laying them.

Though, personally, I don't lay glass without gel.


How large a quantity are you mixing your resin at a time? You've mentioned 2% a few times for MEKP mix, but, mixed in smaller quantities, such as a seat, most poly/viny ester resins tell you a precise amount of drops per ounce to mix. Sounds like it's not being mixed hot enough.
 
Now I've only bought two kinds of poly resin, one from WalMart and one from the boat shop. Neither one gave directions on how how many drops. Well when I did it with the WalMart fg, well it didn't work out. So I bought this other resin. I told the guy what I was having a problem with, so he said I wasn't wetting it out enough. So I would mix up about 18oz at a time and have 15min to work with it.
 
Hearing that poly resin is weak and weaker with more resin scares me. Because I added a lot of resin. So what I may do and wanted to do in the first place is to make a mold of my current seat for a future carbon fiber seat, but we dont have to get into that.
 
When I hand lay seats, I mix up 8 oz at a time, takes two cups on some seats, three on others.

I'd maybe mix a bit less resin than you are now, and take your time to make sure you've properly wet it out, and rolled it well. Seems like you'd be having to rush to get it done the way you're doing it. And don't leave a ton of excess resin on the part, mop it all up, that's what makes it brittle. When it's wet out properly, rolled well, and the proper amount of resin, poly is plenty strong enough for a seat. The very first seat I built myself, I've been jumping on and off of for three years now, no cracks, nothing.

Rolling it, very important by the way, very.

I've never used the Wal-Mart stuff though.

US Composites has some pretty reasonably priced resins. I personally, like FibreGlast. Off the top of my head, the poly I use, it's 13 drops per oz of resin, giving you approx 20 minutes to work.

Epoxy simply isn't necessary for what you're building, and would really be a waste of money.
 
To give you an idea of what it should look like after it cures. There are no globs of resin, and you can still feel the fibers, but they are not loose.


Once again, I stress, rolling it is important.


IMAG0150_zps983bbb70.jpg
 
What did you put your carbon fiber material on fiberglass or kevlar? I talk to one of the guys that works at the U.S. Composites about what I should do. He said I could use their surfboard poly resin to lay the carbon fiber on top of what I have now. He also told me that epoxy resin would warp in the sun especially with the black carbon fiber on top of it. He said that vinly resin is a high grade poly resin and that he wasn't sure but from the color I told him my was, amberish purple, that my resin was more than likely a vinly. Then he went ahead and stated I should use a wax in the last layer with the carbon fiber just to be on the safe side, but also where I could keep the carbon fiber showing and polish it aswell.
 
Seat on the left is all glass, with poly resin. The right is straight carbon and epoxy, needs to be sanded and clear coated.

If you are planning on doing carbon, epoxy is a must.
 
I disagree with the statement that epoxy must be used with carbon fiber.
The wet lay up seat for my baby tracker project (female mould) was done with carbon fiber and Derakane vinylester resin, then clear coated with Duracryl from a spray bomb. No problems.
I attended a composites seminar at Oshkosh (the big Experimental Aircraft Association fly-in) 6 or 7 years ago. The presenter was one of 3M's "glue gurus". He gave an elegant, yet quite easy to understand description of how and why vinylester and epoxy resins can be used with carbon fiber and why polyester resins should not be. I had it written down someplace, but can't find it - probably buried in an old file LOL.

A lot of the other comments are on the mark, regarding rolling (consolidating the plies, I like a stippling brush), removing excess resin from the layup before it cures, etc etc. I seldom use a roller myself - depends on the piece I'm building, but take great pains to remove any excess resin, usually with a brush.
I went online and saw a lot of information posted which seems to be more sales pitch and innuendo rather than solid comparitive analysis, so "caveat emptor" (buyer beware) regardless of the resin you finally decide on.
I also cast my vote for polyester for the fiberglass lay up you're attempting... and wonder if we (all) aren't making a bit of a mountain out of a molehill, here?
Pat.
 
Paco,

They make a few vinyl's, and poly's for Carbon, but, they don't have the same strength that epoxy does.

I guess I should have added "in my opinion," after the it's a must.


Curious question to the OP, why not make it simple and use a gelcoat?
 
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