When is epoxy a bad choice?

You can apply almost any paint on Epoxy! Due to the fact that it is opaque, it usually will protect the Ep from UV rays. Sufficient thickness of the layer assumed.
When you varnish, you are in another world! The varnish not only has to be UV resistant (that means nothing but the varnish itself gets not destroyed by UV), it has to be UV "protectant" !!! And at least three layers are required for a first time protection varnish over Epoxy!

Regards
Richard

 

Richard has it, most any paint will do a good job against UV. For your cabin roof I wouldn't bother with 2 part LPU, I'd just use a single part polyurethane. Insure you get enough paint on the surface (several coats of primer, several coats of top coat).

5 minute epoxies can be brittle, but this isn't indicative of them, some are also quite flexible. Other then tacking together a template or something, I can see no use for these epoxies.

 

Thanks for clearing that up for me...two coats of primer and two coats of a good polyurethane topcoat...that should be enuff then. I have used 5-minute epoxy for small jobs...I usually get the marine epoxy which is a tube of stuff with a white and black tube side by side.When mixed they are of course grey in color and do in fact seem very brittle...something that I need to check on now that I think of it because I used it for small drill-hole patch or two at waterline from an old depth transducer and when I mounted my new transducer. The other kind of 5-minute epoxy I have gotten once or twice is clearish stuff that smells really awful and I have wondered if it wasnt really epoxy but instead might be this vinylester resin that people talk about which I have not tried. Like I said..this stuff has an unmistakeable odor but it DOES seem alot less brittle than the black/white marine 5-minute epoxy...Anyways...thanks guys for the other info on painting epoxy...

 

Take care,

some of the stuff named "marine Epoxy" or similar, is nothing but polyester!

Make sure you use really Epoxy resin.

And let the 5 minute stuff where it belongs, in the hands of RC model builders!

Regards
Richard

 

Just paint it with an opaque coating and that will do the trick. There are UV stable epoxy resins, BTW. They are a relatively new thing, only about 20 years old. Look at any chatachoochie stone company website. They will advertise their CLEAR epoxy bonding/coating with a 10 or 20 year warranty. And of course that's outdoors For some reason, these have not become popular in the marine industry.

I hate to say it, but the marine epoxy industry is kind of a rip-off. Everybody has this idea that epoxy costs like 3X or 6X what poly resin costs. I've bought both by the drum, and it just isn't so, at least not at the drum price. It's only after some re-seller gets a hold of the stuff that the price goes through the roof. Back in 2001, I paid $1.66 a pound for Epon 828 by the drum. As it was sold by weight, the drums were normalized to 500 lbs. At it's density, 500 lbs yielded ~51.5 gallons of resin which cost me $830.00, for a cost of ~$16/gallon. Quality poly resin was about $12 a gallon back then by the drum. Even back then, West was about $70/gallon, and West is (allegedly) just 828 plus a modifier or two. The resins have all doubled in cost since then, but that's true for poly too. I remember thinking at the time that the Vinylesters made no sense at all because they cost as much or more than standard (EEW190) epoxy resin.

If you need a lot of resin, then you need to worry about cost. That's when you need to buy drums, and not from a 'formulator', but a distributor for the manufacturer. They will give you all the FREE data you need to pick out curing agent(s).

Jimbo

 

Neither polyester or epoxy last in sunlight, both has to be covered with ie paint. Over time the epoxy or polyester disintigrates and leaves the bare fiberglass.

Epoxy can bend a bit further than polyester, although I have yet to see a boat bend so far it will break.

The biggest difference is probably the application method. Polyesters cure fast above 15 deg C, epoxy 24 hours if you don't heat it up.

Epoxy bonds well to wood.

Epoxy is expensive compared to polyester.

If poor preparation, poor method, wrong application.

 

Jimbo,

How long have you used this Chattahoochie Stone company clear epoxy resin?..I know it's got a 20 year guarantee and I have surmised often that there must be some marine grade stuff out there somewhere that is being used at $35.00/gallon to glue flagstones in someone's driveway...or other industrial applications...the plumbers use a two-part to re-line pipes but it seems to be expensive for them too...not to be a skeptic but I'm trying to sort out the myths ..if you have some fairly documented anecdotal experience with this Chattahoochie stuff or the like please embellish upon this if you can....the severely budget-conscious and monetarily-challenged portion of this online forum would be hugely indebted to you (in a sense..were broke as I said)

 

I've never used chatahoochie stone bonding resin, but I've seen it in service on various buildings and been to the websites. Although it is clear, it seems to hold up just fine outdoors unpainted. The Shell website had a lot of tech data on the Epon 20XX series resins which are UV stable. This is the resin series that they use for this and also for durable outdoor tile grout. The UTS, e, viscosity were all in the 'normal' range of other liquid epoxy resins, but the stuff was just UV stable. I've never got a price quote; maybe its pricey.

Jimbo

 

Souljour,

I doubt any link or recommendation would help much. Jimbo was talking quantities for yards, not for homebuilders.
We are not even using barrels, we get the stuff in tank trucks.

Regards
Richard

 

A lot of posters to this forum (not necessarily this thread ) have embarked on a project to build a complete boat (and sometimes even the molds) from scratch. In that case a drum purchase makes perfect sense.

Jimbo

 

Nothing to complain!

And I am absolutely pro support of a homebuilder. Just wanted to make clear that those quotations are not available for the average builder.

Regards
Richard

 

Hmm..I just need a three or four gallons but trying to save where I can...if I was building a boat from ground up you could try and grease someone's palm or were friends with a large builder and get it by the pallet I guess...

 

A three gallon kit from Bateau.com will run about $150 plus shipping or you can run up to St. Pete and use FGCI. Buying in those quantities (55 gallon drums) are for folks doing some serious building. The last drum I bought was $900+ after tax, so how much epoxy do you really need.

 

I just ordered about a gallon and a half from US composites (1 gal resin and 48 oz hardener)..thought I'd start with a small order and go from there..I think it comes to about $71.00 with shipping included ..they ship in 48 hours supposedly in FLA since they have a West Palm warehouse....alot of greenbacks for a gallon and a half of goo but at least I'm avoiding the West marine a few blocks from here....it's a medium-fast hardener though with the weather we've been getting here in FLA lately and the forecast it may require some patience...FGCI..hmm..in St Pete? ....will check them out PAR....I will need say 2-3 gallons more for the coach roof and a bow hatch re-model...don't need much at all really but the rebel in me wants to find a non-marine source that is essentially marine grade that some of the guys in here building ground up and needing 40 gallons or a pallet or two of barrels could use to save money.

 

Bateau.com is out of Vero beach and one day delivery to you. Epoxy isn't an area you want to skimp on.

You'll want slow and extra slow hardener in Florida, not fast. In the winter you can use fast hardeners, but not that often. Fast hardeners don't permit you the setup time, which is important for a novice user, so work in small batches of 6 ounces or less, to prevent waste. I'd rather have to post cure or wait for the weather to warm up, then not have enough time to get things in place before the goo is smoking.