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harraik 05-22-2011 09:13 AM

Prepping topsides for Interlux Perfection
I am getting ready to paint my topsides, which have been neglected for a long time. As a result, I have a huge buildup of old unknown paint and I need to get it back to bare fiberglass before priming and painting. I am working on a borrowed trailer and the boat needs to go back in the water at the beginning of next month, so I have a little bit of a time crunch.

I first started working away at the old paint with an orbital sander and 80 grit, which I saw recommended somewhere, but it was unbelievably slow--like a week straight of sanding slow--and I definitely don't have the time. So I went to my 4.5" angle grinder with the sanding attachment and a 50-grit disk, which is the least abrasive that I could find. That is making much quicker work of the job, but it is leaving me with a bit of an uneven result. I am stopping as soon as I get through to the fiberglass, but I am working in vertical pulls and creating low spots all the way along as I go.

Should I go back over with the orbital and try to smooth it out? Should I expect to fix this with fairing compound? If so, is that going to be a reasonable task if the whole topsides needs fairing? Should I be concerned that I am weakening the hull? How smooth do the topsides need to be to get a good result? Thoughts about going forward (I am only about a 1/4 of the way done)?

Finding limited resources on the topic, and the process of extensive fairing...

To add a little bit of perspective, this is on a 70's Coronado 25--I want to do a great job, but it isn't that dream boat that I will have forever.


capecodda 05-22-2011 10:06 AM

some experience: done by "professionals"
I had a "professional" awlgrip job go bad when a boat yard used a rotary sander. When they painted, the surface looked like a fun house mirror, with periodicity of ripples about the side of the sander disk.

The correction for this involved using a product called "high build" and long boarding the boat (sanding with sand paper on 6 foot long boards) to get the surface fair. To insure it was fair they used a blue dye that would show the low spots when they long boarded. They kept applying high build and long boarding until it was even. The end result was a mirror finish with very little distortion. Watching this process, it was hard work and time consuming for even a big crew.

You may not be as picky as we were (having gone from a faired topsides rippled topsides did not make us happy) so this may not apply, and this was done "professionally" so your results might be better :) . We are not experts, just victims.;)

Siamese 05-22-2011 10:29 AM

I'm not seeing a happy outcome here. The paint will only amplify the imperfections. You didn't mention what you're doing in the non-skid areas. At least there you can get away with more, and make up for it with the right product applied to those areas. If you've lost fairness in the areas where there is no non-skid, you'll probably either have to find a way to put your boat on stands and extend your time or simply accept a diminished outcome.

harraik 05-22-2011 11:43 AM

Thanks for the advice

So Capecodda, that was an orbital sander that they used or a grinder with sanding attachment? If you are suggesting that an orbital sander isn't acceptable either, what would you suggest?

Saimese: right now I am just working on the topsides--between the rubrail and the antifouling paint.

I am going to try and work out another method to tackling the rest of the boat, let you know what I come up with.

Antibes 05-22-2011 12:13 PM

Try using interlux's stripper to remove the heavy paint. It will reduce a lot of hours. I prepped my hull using 80 grit with an orbital for the heavy sanding.I would stay away from grinder with the coarse paper. The rolled and tipped perfection and it came out professional

harraik 05-22-2011 12:29 PM

Thanks Antibes, that is kind of the direction I was thinking of heading at this point. Did that stripper take it all the way down to glass? I would assume that even if it didn't, anything that the stripper can't take care of will provide a proper bond for the paint, right?

Antibes 05-22-2011 01:11 PM

It took it down to where the wet sanding using a 5"orbital with 80 grit got it clean

capecodda 05-22-2011 01:31 PM


I believe it was a Dual Action (DA) (which I guess is the same as orbital) sander. It was pneumatic, and used by the the yard guys.

Also, remember I was fussy, but I started with a very fair surface, and worn out paint, ended up with a rippled surface, and new paint, plus it wasn't a low bidder situation. Hope your situation turns out well.

harraik 05-22-2011 01:54 PM

Thanks guys, I'll see what I can do.

hellosailor 05-22-2011 03:17 PM

It might be worth looking into media blasting, either getting a rig or having someone come out to do it. Unlike grinders, it should not be able to eat into the glass itself, so there's less chance of damage.

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