Polyester/Core/Epoxy

I have not had any luck locating one.

 

For above the waterline spray up Awlgrip's 545 epoxy primer (also called USP545 in some places, like VectorLam's composite design software). Sprays nicely without too much orange peel, easy to sand and prep for final topside paints like an LPU from any brand after pulling from the mold. I prefer grey, but also available in white or clear. The grey goes on a little thicker and shows air bubbles better during the first glass layup. White may be best if you want a light colored hull or wheelhouse, as it doesn't take as much topside paint to hide at the end of the project.

For below the waterline, talk to your regional rep for Sherwin Williams (marine/industrial coatings division) or a rep for AmerCoat products. This isn't a walk in the store kind of thing, look on their websites for dealer phone numbers or regional industrial sales contact. Both offer a variety of underwater rated epoxy coatings. Many are applied on steel and aluminum commercial boats for permanent underwater use. Talk with the rep about your construction method and environmental conditions (ie, in mold not sprayed on a steel boat, temperature and humidity, some products come in standard and low temp versions, some are more moisture/humidity tolerant than others during application for times like painting a steel boat in the winter at 40F temps near dew point, other coatings are happier at 80F and drier conditions). Many of these products are used to barrier coat blistered hulls. Interprotect 2000E is somewhat like these coatings (it may even work in the mold? talk to the rep).

As a final option, there are "Tie Coat" type products but they are very finicky last I heard. After spraying gel coat, this stuff is sprayed before the fiberglass goes in. It likes the gel and styrene, but cures to a surface epoxy is happy to bond with. Is a form of skin coat also to reduce print through of the glass. Talk to your local Composites One sales team, or other major composites supplier. Tie coats are rarely stocked (chemical shelf life and all that), but can be ordered in within a few weeks in most cases.

With any of these make sure to follow the cure and recoat times. Don't get too eager or you'll trap solvent in and the coating will blister. Many are good to epoxy over up to 30 days or more without sanding, but some are not.

 

And don't mix resin systems. The poly will crack before the epoxy takes much load, and with the outer skin failed, the epoxy laminate will be overloaded and fail later. It sounds like you plan to vac bag? Maybe think about infusion instead of wet and bag? Not sure what part size, but 30% sounds like a lot of waste. You can order infusion specific epoxy that is very thin, and if you're post curing the slow hardener won't be an issue. Infusion can get complicated but might be worth the resin savings.

 

Infusion losses would be much lower. My losses are high to wetbagging.

Long term life in the water usually requires ablative paint so marine critters don't become part of the boat.

Explain typical season and location before talking bottom paints.

 

I definately want to get into infusion. I am absolutely new to it and am trying to find some good introductions. Any suggestions?

Thanks!

 

Infusion, pre-impregnated, post cure epoxy resins and all these similar systems are suitable for shipyards with very qualified people for building high tech race boats with exotic fibers, or very high quality yachts, or rather big composite boats (some tuna fishing boats, in the 170 feet range, are made in GRP sandwich using infusion). Or industrial serial fabrication.
For someone who was asking if he can mix epoxy and polyester in the same composite, or about paints, it's totally insane. These are complex techniques asking for expensive tooling and trained guys.
The cost of the investment and consumables of these techniques for ONE small yacht in GRP is stratospheric.
There is a rule: for a simple boat, use simple techniques. A well mastered simple technique is more efficient that a badly mastered complex technique.
Furthermore there is no gain on ONE small GRP boat ( I call small until 40 feet, the max that a single builder can hope to go until the end of the project in a decent time, often several years) to use these methods.
A well made hand layed GRP, sandwich or monolithic, is already a good material largely good enough for a cruising boat. Thousand of good strong boats hand been made by this methond. Cost is also a factor, beginners often forget that the bare hull in most of the cases is about 25 to 30 % of the total cost.
For a beginner learning how to make a good quality hand layed GRP is already a task. That asks for knowledge of the basic materials, glass and resin, and the methodology, to have some brains and a lot of perseverance.
Reading first several good books about boat building in GRP is an obligation. There are also excellent industrial manuals. That takes some time as the beginner has to understand perfectly. After that the beginner won't need to ask in forums, except for details, obscure points or for sources or for choices of materials.
The beginner will discover that GRP has its subtleties about the different qualities of resins, pre-accelerators, and catalysts, retraction. through print and other niceties. It's better to learn the bases first.

 

Infusion is the best way to do foam sandwich.

Is it easy? No.

Is hand layup of foam panels best? No, with exceptions. Easier? Yes, with exceptions.

Is infusion of a whole boat wise for an amateur? No.

The reality is wet bagging is rather difficult, but the final product far superior to hand laying.

Ilan, You could have responded with the main point. Education is key.

 

If you are looking for a 2k paint that is user (amateur) friendly then look at Quantum 99 from EMC.

I've painted two cats 37ft and 44ft respectively one sprayed one rolled and advised several others on their own painting projects.

This stuff is Awlgrip for the 21st century. Easy to apply, no need to be panic about temperature humidity (within reason) and the gloss level is amazing. Best of all it can be wet sanded and buffed if you have any issues or repairs to do down the line. They even sell it in a rattle can for repairs.

I stumbled over the stuff when I painted my Cat and the support I got from the company was amazing.

Hope this helps,

Richard

 

Many factors that determine how you build molds.
How many parts you want to pull is probably the biggest.
What materials you are processing is next.
There are good epoxy tooling gel coats, but there is no polyester gel coat that is epoxy comparable.
Don’t believe anyone who claims otherwise.
You can use epoxy primers such as 545 as an in mold coating, which will address pin holes, and give a good base for finishing.
If building a one off, don’t sweat the finish, just make sure the mold is the right shape. Avoid the impulse to build massive molds if it is just for a few parts.
You don’t need to use mat, you may get some print out depending on what resin you use. The UFO uses 7500 glass with no mat with Epovia infusion resin.
SHC