Anyone have an opinion on using two or one part polyurethane paint for application on hulls above the waterline?

The original catamaran hull is manufactured from Nomex, a heat cured combination of honeycomb and pre-impregnated epoxy sheets. It never had a gel coat finish applied.

Now the original polyurethane finish is old and worn.

Is it better to use two or one part polyurethane on this hull, to bring it back to "Bristol"???

What are the advantages and disadvantages of both???

Any thoughts??

Tom

I would strongly recommend a two part finish. It is considerably harder and more resistant to chemicals, etc... I also noticed that the one part would wear much faster off the bottoms of the hulls from sliding cat tracks than the 2 part does. I would look at Interlux Perfection or I've also heard good things about the system 3 two part poly's. If you are going to go through all the trouble of sanding and prepping the surface, why skimp on the paint to be used? Perfection is about twice as much as the one part poly but I think the end result would be well worth it. Awl-Grip is also very good, but is a bit more difficult to use and about twice the price of perfection. Also, if you are going to spray, you need to make sure you have the right equipment and safety precautions (forced air respirator, etc...). Good Luck!

A two part system will give a more professional, longer lasting finish...depending on the product it can be much more abrasion resistant as well...the down side..
1) Cost…
2) Two part products like Awlgrip are harder to apply however some, like Imron, are quite easy in comparison.
3) Greater health risk in breathing vapors or absorption thru skin.
4) If your boat already has two part Polyurethane on it you may be able to "go over" it with either paint system...but next time you paint you will more than likely have to strip off all the one part paint if you decided to go 2 part the next time. Check to see what the old paint system is on the boat now, as most two part systems will lift old oil or one part poly finishes and cause a unbelievable mess.

One part is for the Amateur who is trying to fool himself into thinking that he can get an Awlgrip like finish at an economy price…this is definitely one area where you “get what you pay for”.

Regards,
Bob

What condition is the original paint in? Is the color consistent, no damage and just needs to be shined up? Or does it have nicks, scratches or is it in need of repair in places?

Awlgrip, Imron are two Polyurethanes I'm familar with and they are excellent as one stage or one part paints. Two stage normally means a base coat (color) and a top coat (Clear). Now if your boat is like the first part of my question(just needs to be shined up) then you could sand the boat with like 600 grit and have it clearcoated with Imron. Like new finish. Or if you want to do a little fairing and repairs refinish it with one stage awlgrip or Imron.

Find someone in your area that deals with or uses these paints and ask them. Many Automotive paint suppliers carry Imron. Look for one that has Dupont products. Ask them who uses it in the area and go talk to them. Don't confuse Poly-urethanes with urethanes. Two very different animals.

One-part anything is not a linked polymer- just dissolved solids.
Simple example--Is there any one part epoxy? No.

I used system 3 2 part water based polyurethane on a carbon mast. My recommendation IS NOT to use that. It comes off very very easily - it doesn't have nearly the abrasion resistance it claims.

I cannot comment on INTERLUX or AWLGRIP paints because I quit using them when I found I could buy IMRON cheaper from local commerical suppliers

System 3 is not as good as IMRON. It makes a great Aircraft, Bicycle, boat deck, etc paint. However it's not what you want to paint your daggerboard or hull bottom with

IMRON is available in several formulations including water based like System 3. The availablity and cost of various formulations in your area will depend on the local market. The auto/industrial oil based is almost always available and the cheapest. It's top of the line custom car paint. Very pretty and very durable. The water based will cost a little more and will be between oil based IMRON and System 3 in durability.

One thing to keep in mind. These things don't even look like normal paint. They almost all solids, very little liquid. So, stir, stir, stir,....

Bottom line- When I repaint my boat, I will spray water based IMRON

Aren't there epoxys that harden just by UV.

I painted my P19 with a one part interlux Brightsides and now wish I would have used gelcoat or two part instead. I did not have the forced air hood required for the two part paint application. One part paint may not have the abrasion resistance required and show wear spots in les than a year of use.

Yeah, there are UV curing epoxies, don't know if they are applied in paints yet though, only laminating resins.