3M Marine Gelcoat Restoration Instructions now state to DRY sand

[Canuck-Surfer]

Hey guys! I know I have another gelcoat thread going, but I wanted to start a new thread with the specific title I used above.

I've been doing tons of research to prep for my gelcoat restoration. Everyone on the interwebs seems to agree that 3M marine product and procedures are some of the best.

But in my research, I've discovered that 3M no longer recommends wet sanding...3M recommends not wet sanding but DRY sanding with their Purple P800 followed by wet sanding with their Trizact P1500. See their instructions here: http://multimedia.3m.com/mws/media/1...sional-sop.pdf

Everything I've read says to wet sand gelcoat, but 3M says otherwise. Thoughts?

Here is 3M's video on how to do it, they definitely are not wetsanding the first step: https://www.youtube.com/watch?v=mMrAKnD08uU

Equipment wise, I don't have an air compressor so I'm leaning towards the Shurhold DA 3100. They have a good video on the wet sanding process using their DA: Hot to wet sand your boat

What's funny is that in the video they use a combination of 3M 260L (Purple) and Mikra Microstar sanding discs for wet sanding. But if you look up the specs for both products, they ALL are clearly labeled for DRY sanding only.

So basically I'm confused. Its this just new sanding tech we need to embrace with no water?!! Has anyone fully used the current 3M process as documented?

[bturner]

How much of the boat are you sanding and how bad are the areas in question? The technique 3M is using looks to be a commercial process to me that would be used on something very large and by professionals. In my experience going with anything 800 grit is going to be very aggressive for correction or restoration. I've seen shops go this route on a restoration where the hull was completely re-shot with gel coat but not on boat that you're basically looking to restore existing gel coat. Hitting any edge or corner with 800 using a DA without extreme care is quickly going to give you flat spots or worse yet burn through.

Lastly DA's use a ton of air. My 6HP 30 gallon compressor can't keep up with mine for more than about 10 - 15 minutes at a crack so you know that this article has to be written for the commercial/professional shop. If that's you then have at it and let us know how you make out. For me I'll stick with what as worked the last 20 years.

[shag]

I have a friend that owns a Detail company here and they have been dry sanding for about 10 years. When I first saw it I was like, what? But he knows what he's doing and the boats look brand new when he finishes - and they stay that way for a good long while.