Wet sanding/compounding gelcoat novice questions

[tmjb]

I am a novice to buffing and waxing (as will become apparent from my questions) so have read many tips and comments on this subject including, in particular Maine Sails 'Tips for a great buff wax'. Following the latter's detailed process I have purchased, I think, Maine's recommended equipment and products, and made a first tentative start to the process this weekend, this is on a 1981 hunter that I don't think has been buffed and waxed in a long time - it was standing unused on the hard from about '97 or before until last year.

My questions, and I apologize in advance if they have already been covered but I couldn't find them, relate primarily to the wet sanding process - which my gelcoat seams to need. Main Sail recommends using a kitchen sponge as a backer for the wet/dry paper. Are we talking about the thin (maybe 1/4") 4.5" x 2.7" sponges or something else? If so, is there a more efficient size of paper to use than a standard quarter sheet (seems a bit big for this sponge)? How do you know when to stop sanding (when you start to feel less friction?) and when to discard a sheet?

For both sanding and compounding, what do you do regarding applied pinstripes etc.? Do you need to mask or is it OK to go over them?

When compounding and buffing in areas such as the cockpit, given the recommendation to only use the pad on the machine flat on the surface, does this imply that much of these areas needs to be done by hand?

Thanks in advance for any and all input.

 

[Justin_NSA]

I have no experience with the wet sanding step, I started with the acid wash and went to applying the presta gelcoat compound. I went over my stripes with the compound/buffer and it improved their gloss. no visible damage. I wouldn't sand them though.
I hope you get some good feedback. "Sanding" sounds scary to me but it is proven to work when it's needed.

 

[tmjb]

Many thanks for the prompt reply Justin. Good to know re the stripes.

I too was Leary about the sanding but with the little that I've done so far, for my gelcoat at least, it seems to improve things greatly and I'm guessing saves a lot of time compounding without the sanding step. The compound is, after all, like fine liquid sandpaper.

Looking forward to getting feedback about it from those with experience of it.

 

[Siamese]

I've done a couple of boats using Maine's instructions. Excellent results.

Regarding the sponge, just use the regular kitchen sponge, maybe 3/4" thick? Gives you something to hang onto and gives the paper some backing reinforcement. Just cut your paper down to accommodate the sponge. Can't help you with when to discard a sheet. Keep dipping it in the water bucket. It's pretty much a matter of feel. Paper's not that expensive.

By the way, how about sharing with us which level of grit you're starting with and what grits and compounds you plan to use.

Can you clarify regarding "applied pinstripes"? Graphics can be:
1. gelcoat
2. vinyl
3. painted
Which do you have?

If vinyl, you could tape them off for the entire process, but I would recommend removing them and putting on new 3M vinyl striping when you're done. I've restriped a couple boats that way and the results are very good, but it takes considerable care to get them really straight. If you don't re-tape, it seems like you would have gone through a lot of work to still have it look like crap.

If they're gelcoat, Maine addresses that, but as I recall, you want to tape them off so they don't bleed into the surrounding areas as you sand and compound. When the surrounding areas are done, re-tape, and do the entire process on the graphics. You'll have no bleed, and nice shiny graphics.

If paint (which I haven't had to deal with), I'd remove it, YMMV. My philosophy is that if you're going to do the entire sand and compound process, you might as well go whole hog. Done right, and maintained subsequently, it's not something you'll do again for a long time. And, it's too much work to end up with diminished results.

I hope you're starting with the topsides and following up with the deck areas. Compared to the decks, the topsides are easy. Last spring I did the topsides on my Catalina 28, and throughout the summer, I worked on the deck while she was in the water. Obviously, all the sand and compound techniques apply, but you'll want to get smaller pads for your grinder/polisher. I think mine were around 4". I didn't do the deck all at once. I broke it up into sections:
1. side of cabin starboard
2. side of cabin port
3. cockpit backrest port
and etcetera.....
The deck work is a total pain in the butt. Not only are you working on small, hard to get at areas, you'll be dealing with a lot of deck fittings. No matter how careful you are, you'll be chewing up your pads as you encounter some of the hardware. Make sure you have extra pads on hand. On the plus side, people occasionally comment on my boat and ask if it's new. Yeah, it's fun to tell them she just turned twenty. But, whoopee, we always have to bear in mind that nobody really gives a sh#t what our boats look like.

If you go through the drudgery of doing the deck areas, make sure you're fastidious about it, and keep it waxed. It's not a job you want to do again soon or ever.

And, with regard to your question about using the polisher pad flat, yes it's relatively easy when you're doing the topsides, and can become difficult when working on the deck. As I mentioned, the smaller pads will help a lot. Also, and I hope Maine isn't listening, but once I became reasonably adept at using the grinder/polisher I didn't always use it flat. Anytime you use it on an angle, of course you risk burning your gelcoat. I've been either skillful enough or lucky enough to have never gotten a burn. On the one hand, I don't want to be the guy to tell you to use the tool in any way but flat, but in the real world, there were times when I did what I had to do.

Also, with regard to your followup comment about sanding before compounding to save time. There's more to it than that. No amount of compounding is going to make up for sanding if the surface is heavily oxidized. You'll get gloss, and it might look pretty good, but will never match the gloss obtained by doing the entire process (when appropriate). Starting with 1000 grit, when 600 would be more appropriate will likely lead to disappointment.

Short story. One of my buddies on my dock (has an Island Packet 42) saw me compounding the deck, and explained to me that once fiberglass has lost it's shine, there's no getting it back...all you can get is temporary results, bla bla bla. It struck me as a little rude for him to walk over and explain to me that I was on a fool's errand, but I took a moment to set him straight and suggested he look at what Maine has to say. We had to agree to disagree. He wasn't buying it. Until I had completed the job. He walked over one day, said my boat looked amazing, and humbly asked how I had managed to do it. Good for him, a lot of guys couldn't have admitted they were wrong.

 

[pateco]

Main Sail recommends using a kitchen sponge as a backer for the wet/dry paper. Are we talking about the thin (maybe 1/4") 4.5" x 2.7" sponges or something else? If so, is there a more efficient size of paper to use than a standard quarter sheet (seems a bit big for this sponge)? How do you know when to stop sanding (when you start to feel less friction?) and when to discard a sheet?

I used standard Scotchbright brand kitchen sponges from the supermarket. They last pretty well. I bought full sheet paper and cut it to fit the width of the sponge. Keep a bucket of Soapy water with you to clean and rewet the paper, and rinse your work area frequently with a hose to remove sanding dust/debris. As you sand, the resistance will become noticeably less when a particular grit of sandpaper has done its work, then you switch to the next finer grit. When the sheet gets worn, I found that the paper started breaking down and cracking/tearing well before the grit wore out. (different paper may get different results).

When compounding and buffing in areas such as the cockpit, given the recommendation to only use the pad on the machine flat on the surface, does this imply that much of these areas needs to be done by hand?

For the deck area, I found a small 3" high speed sander at a pawn shop, and bought a Velcro backing plate and wool pads to fit it. I used the large buffer for large areas, and the small one for tighter areas. you will still have to do some of it by hand depending on deck hardware spacing. Below is a picture of the tools I used.

I think I got pretty good results, but I learned a lot along the way, and may go back and redo the buffing stage to several of the early areas of the deck.

I am waiting till I haul out to do the hull, but I did try a test section. by hanging over the side.

My stripes were blue gel coat with multiple white/blue/silver vinyl stripes on top. The vinyl was cracked and bad so I am removing. however, I was quite pleased with how well the blue gel coat portion cam back. In the picture above, you can see how faded it was before.

 

[Benny17441]

Get a sponge that is a little firm and thick enough to have some cushion effect and for you to get a good grip. Cut the paper to size. I would use 1000 grit and replace the paper when it gets covered in the chalky compound. You are peeling away gelcoat so sand as light as you can while strong enough to remove the oxidized surface. Do not use power tools. The finished surface should be shiny. Use the wet-sand paper type in order to avoid paper breakup.

 

[tmjb]

Thank you all for the prompt and detailed input thus far.

With the little bit I've done so far I used P600, P800, P1000 wet/dry paper rinsed in water with a little dish soap in it as Maine suggests. The sponge that I used is like the 3m Scotchbrite that I think Pateco was referring to but without the Scotchbrite abrasive, just the sponge. I followed this with 3m compound hand applied thus far. I plan to use the recommended buffer and Presta compound on the topsides.

My pinstripes are original Hunter (the PO has patched them in a number of spots using a tape that he passed on to me). I would assume that their vinyl. How difficult are they to remove and what is the recommended technique?

I did start with what I am considering a test section in the cockpit, understanding that this is difficult because of access, detail etc. However, I did so because I did not have running water available to me last weekend (hopefully will this) and so had to use buckets and I wanted to try something and see how it went.

Pls keep that advice coming.

Thanks again.

 

[Charles Erwin]

As to the stripes use an 'eraser wheel.' It is a drill mounted rubber wheel that removes vinyl stripes better than anything. Obtainable on line or from your auto paint supplier.

You mention using '3M compound hand applied .' That sounds like you are doing this with your hand and a rag or similar. If that is what you are doing you will be disappointed. Compound needs to be used with a variable speed buffer and white wool pad in order to get any results. Remember you are trying to remove a 1000 scratch with this compound and that will not happen unless the compound is applied as I suggest. Probably better even to go to 1500 or 2000 before compounding because a 1000 scratch is pretty tough unless your compound is plenty aggressive.

 

[pateco]

My stripes were original from 1983, and very brittle. I tried multiple methods, to remove and clean, and this is what worked best for me.

A razor scraper with plastic blades

An old heat gun I had from working on RC airplanes.

Heat the vinyl until the adhesive gets soft in small sections and then scrape with plastic blade. DO NOT overheat, and DO NOT use metal razor which will scratch the gel coat. (I found the metal razor tip out the hard way).
Once a section of stripe is off, I used Turtle Wax Label and Sticker remover to remove the rest of the adhesive which was still stuck to the gel coat.

This stuff was Magic. I tried Goof Off, Goo Gone, and acetone as well, and this stuff was night and day superior. Some stubborn spots took a little scraping, but most of the adhesive wiped right off. The other products I tried barely touched it. It does leave a citrus smelling oily residue when complete, but that wiped off easily with acetone

I have since used this same method to remove the silicone around my ports when I re-bedded them. Again it was a great timesaver.

Have Fun.

 

[25yearslater]

If you are worried about burning with standard compounds I would suggest the Aquabuff 1000 and 2000. They are a diminishing grit water based compound. The odd thing about them is you need to use very high wheel speeds that would cause burning with other compounds. This is my 76 Oday.

 

[sailnoproblem]

I know some will disagree but use EZ-OFF oven cleaner, on the vinyl stripe. It works great.

 

[Crazy Dave Condon]

TM
as a retired boat dealer, we used a product called Finese It by 3 m which comes in a paste which is a fine compound best suited for gel coat used in the marine industry used by many. Get the paste not the liquid. Key is to using this, clean off the boat first and then use a buffer at low speed not over 1000 rpm going back and forth constsntly without it sitting in one place or you will burn th gel coat. Think of gel coat being a plastic paint and then you will understand a high speed buffer is not recommended. then wash off and wax. I would go into further detail but whapped my lefrt hand with a hammer yesterday while laying flooring in the basement.

 

[Ilanortho]

MEK from the paint department works well to take the residue off. Use a respirator.

 

[Ilanortho]

As to the stripes use an 'eraser wheel.' It is a drill mounted rubber wheel that removes vinyl stripes better than anything. Obtainable on line or from your auto paint supplier.

You mention using '3M compound hand applied .' That sounds like you are doing this with your hand and a rag or similar. If that is what you are doing you will be disappointed. Compound needs to be used with a variable speed buffer and white wool pad in order to get any results. Remember you are trying to remove a 1000 scratch with this compound and that will not happen unless the compound is applied as I suggest. Probably better even to go to 1500 or 2000 before compounding because a 1000 scratch is pretty tough unless your compound is plenty aggressive.

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I bought the 3M eraser wheel which cost a small fortune. It might work well for automotive small pinstripes, but on the multiple stripes on my Hunter it smeared the large amount of adhesive residue all over the hull regardless of speed it was run at.

 

[tmjb]

Thanks again for all the continued input. I much appreciate it.