UV Resistant AND Waterproof

The US government is using polyurea on bridges and pilings. The US military is also using polyurethane and polyurea for underwater structure waterproofing. POR-15 is a US Army/Navy standard, even though it's just a rebadged Raptor product (polyurethane). I've done some industry testing with these products and they do hold up well, given their quirks.

Calling the technical department of any of these companies, will not yield much more than the standard recommendation of using only their prescribed procedures, products and liability motivated exceptions. I've talked to most of them and have repeatedly found I knew more about their products then they did, unless you can talk them into speaking with one of the chemists. Most don't know what their products are, what it's cure agent, vehicle or activator might be, etc.

 

Wow, guys! This is really quite frustrating. At this point, I'm not sure what coating to apply to the rudder.

Are these assumptions correct:
- Topsides paints are not suitable below the waterline.
- Bottom paints are not suitable above the waterline.
- Gelcoat may not adhere to the epoxy/glass cover on the rudder.

I'm really stuck and I would like to get this project out of the shop.

What do you recommend?

 

I find this really strange saying topside paint won't work under water. Every boat afloat that is painted, uses what is classed as a topside paint for it's hull and is normally what coats the hull before anti fouling is put on.
For any hull before painting the key is preparing the hull, rubbing down to remove any wax or other contaminant, putting on a primer then painting.
The same would apply to a rudder or Keel.

 

FAO PAR.

Hello Paul,

This may interest you. At the Seawork Exhibition in Southampton in June, the Fujifilm Duplex antifouling system will make its debut in the UK, promoted by TUDOR STREAMLINE SURFACES LTD.

"The Smart Surfaces Duplex silicone fouling release coating was developed by the US Navy and is now manufactured by part of the giant Fujifilm Corporation which brings its reputation and technical expertise to this demanding market. Duplex was devised to cut biocide and heavy metal pollution in US ports and it has been in use successfully with the US Navy for over ten years".

http://www.seawork.com/news101

I searched the Forum for any previous mention about the product & this thread is the most recent to mention anti fouling coatings in general terms, so rather than start a new thread, here are a few links.

https://www.smartsurfaces.co.uk/technology/

https://www.youtube.com/watch?v=RWLTD79w_bY

https://www.youtube.com/watch?v=8sh8erFQiGo

https://www.youtube.com/watch?v=PRc26DwgFGo

I'd be interested in your opinion. The increased speed claim looks very attractive.

All the best,

Perry

 

I think the jury is still out on these silicon coatings, but we'll see. A lot of companies, especially DuPont, has been working on them for years, but it's a difficult set of problems to solve.

 

The rudder got 5 coats of gelcoat, brushed and rolled. It's been wet-sanded to a shine with #400 and #600 grit. So far, it looks pretty darn good.

Gelcoat should work above and below the waterline. That's the original finish on the 40-year old boat.

To summarize, the original wood slab was covered in 3 layers of glass and epoxy, 2 coats of epoxy with barrier additive (powdered aluminum), and 5 coats of gelcoat. Internet sites about hull repair suggest that if it was a topsides repair it would now be ready now for paint. And then a weekender would apply a coat or 2 of wax to keep the project looking amazing.

If a pre-schooler was to ask: "Grandpa, why don't you just make the boat out of wax?", I'm not sure I would have an intelligent answer.