What grit sandpaper to prepare swim platform for Cetol

[Mainer]

I want to refinish my A27 swim platform and need advice on preparation.

After initial oxalic prep on what was a "natural" swim platform, I put 3 coats of Cetol "Natural Teak" on my swim platform a few years ago. It has been peeling up, especially this past summer and I'm ready to redo it.

I have an excellent Festool random orbital sander and need advice on the best grit of sandpaper for the job of preparing the surface without sanding too much teak away.

Would appreciate suggestions.

Thanks in advance,

Dick Jones

[Bob Noodat]

Just to be contrarian I would say leave your very fine orbital sander in the tool closet.

Personally I prefer steel wool. Buy 3 grades, say #3, #0 and #00 and use them sequentially. No damage, it follows contours, and the whole process is remarkably quick and much less aggressive.

Orbital and belt sanders have their uses of course: use them on things you really don't care that much about.

[motthediesel]

I wouldn’t use steel wool. While it does leave a fine finish on the wood, it also leaves tiny bits of steel behind that will discolor the surface. Bronze wool is available, and it’s tiny residue bits will not oxidize in the presence of water.

[nebulatech]

Prepping raw wood for coatings is typically done with 120 or 150. I had some customers who would sand to 220, but its not optimal.

As far as not sanding too much teak away, you will end up needing to sand the wood down until it is even and fresh looking. It doesn't matter if you use finer grit paper; it just takes longer. Every time you strip the teak to bare wood, you're going to loose a good bit. That being said, 80 grit is too coarse and will possibly leave swirl marks. (though your festool is an awesome sander, so maybe not)

In order to preserve as much teak as possible going forward, it must be properly protected. The best finish system is 2 coats of 2 part epoxy with a uv resistant gloss topcoat. I prefer automotive 2 part urethane, but even a good varnish can work for a while. What makes the clearcoating peel on teak isn't the coating itself failing, but rather UV degradation of the underlying substrate (the teak).

2 part urethane over epoxy can last 10 years on teak. I don't know how varnish holds up on epoxy, but DesertAlbin might be able to chip in. I believe awlgrip has a 2 part clearcoat. The downside of 2 part urethane is the isocyanates. Definitely need a good cartridge mask, even when mixing it.

For West Systems, its the 207 special clear hardener. West System isn't the only epoxy. I've been meaning to call Raka in FL. They have some interesting UV resistant stuff, and its very reasonably priced. I'm considering Raka for my upcoming brightwork.

[SkipD]

I’ve been a happy Cetol user for many years for all exterior teak, except for the swim platform. Considering the size, exposure and use, I’ve used teak oil which has been applied beginning, middle and end of season. Takes 10 mins with no prep work for each application.
Initially the platform had been Cetol, maybe varnish, and was peeling etc. To get it down to a smooth, ready state took some soy based stripper, followed by light 80 grit spot sanding and then 120 grit.

[Bob Noodat]

I wouldn’t use steel wool. While it does leave a fine finish on the wood, it also leaves tiny bits of steel behind that will discolor the surface.

Then you haven't used a fine enough finishing grade, and not done a final wipe with alcohol or acetone. My refinished teak looks beautiful, and feels fantastic. I see those orbital sander jobs all the time: there is an irresistible urge to chase every defect deeper, ending up with an undulating surface, plus the whirligigs you invariably find, caused by rogue particles.

But each to his own.

[nebulatech]

I’ve been a happy Cetol user for many years for all exterior teak, except for the swim platform. Considering the size, exposure and use, I’ve used teak oil which has been applied beginning, middle and end of season. Takes 10 mins with no prep work for each application.
Initially the platform had been Cetol, maybe varnish, and was peeling etc. To get it down to a smooth, ready state took some soy based stripper, followed by light 80 grit spot sanding and then 120 grit.

Teak oil can be a great option for large surfaces like decks. It just requires frequent recurring maintenance, but in my opinion, it looks beautiful.

[Mainer]

Gentlemen,

Thank you very much for your responses. They gave me hope that this time I could have a better, longer result. Here's where I now am:

I started with #3 steel wool and found it really great for all the places where wood is joined to wood and edges need prep,, but really tiring on the total flat surface. There I couldn't pass up the Festool and using 120 grit I carefully sanded all the flat surfaces, and after a substantial amount of cautious work the entire raw swim platform looks very nice.

Next I'm going to follow Bob's advice and do an acetone wipe, followed by Nebulatech's suggestion to buy and apply a 2 part epoxy, followed by a hardener.

Again many thanks to all for your seasoned suggestions.

Dick

[nebulatech]

Dick, good luck!
download/file.php?id=22519

This link is for the West Systems guide which I posted previously in another thread. There is a section on doing clear coatings on brightwork. (pages 96-101) If you have any questions, feel free to PM me and I'll send my phone number. I'm no expert with fiberglass, but I have plenty of experience finishing wood, including several jobs using epoxy.

[tribologist]

Im no fan of hard film coatings on wood thats wet..peeling suck.. but it makes sense its the wood that degradez We applied Le Tonkionois from tarsmell.com and it thins out but its not peeling. We put two layers on last year and that was a bit thin so I just slobbered on a new coat. I think im going to put on a few more coats. It looked really nice last year but i let it degrade a bit to far before recoat.

[Nancy]

I was very happy with Cetol on the swim platform of our Trojan F32.

I used a belt sander to get it down to bare wood (click on photo to see correct orientation):

swim platform 2-103005.JPG

In subsequent years, I spot-sanded as necessary and cleaned with 3M Scotchbrite.

transom-060606-1600.JPG

[srcody617]

I’m thinking about this operation as well.
My swim platform is currently off the boat and is not in the critical path.
But I was doing some other epoxy work and wanted to experiment.
I sanded with an 80-grit paper just enough to get smooth.
I followed on a small patch with Total Boat Penetrating Epoxy, two-part, 2:1 mix. This epoxy runs like water, and soaks in very effectively to seal the wood.
I have not decided what to do next; I don’t want the platform to be slippery.
Maybe there’s a nonskid varnish, or an additive.
Someday I’ll learn how to insert photos here and keep you informed.

[tribologist]

Nancy, thanks looks great! I used Cetol in our whaler and it was much more "orangy". Over time that thinned but did not peel either. I think they are comparable in maintainabilty. One are supposed to scuff Cetol and reapply a coat each year if I remember right.

[Nancy]

Thanks, tri. This was original Cetol since the other colors hadn't been developed yet. Maybe it was wood I used it on that made it seem less orange than it sometimes does. The newer Cetol Light is a much safer color IMO.