Gelcoat repair questions

[WiskyDan]

So I'm going to be doing some black gelcoat repair (a few scratches) this weekend with the Spectrum paste. I've got a pretty good idea of how to approach the gelcoat repair and have all of the necessary grits but I've got a couple questions for those that have done this before:

Wet sanding by hand or with a machine?

I have a 3" hand sanding kit with all of the necessary grits but I've seen mention of using a small buffer with a 3" sanding disc as well. I've wet sanded my boat by hand before and it worked OK but would it be an easier/faster process with a machine or are the risks of over-correcting too high?

Cutting compound or cutting compound with polish?

I've been trying to decide if I should go with a buffing compound or a two-in-one that compounds and polishes in the same step. Options that I'm looking at:

• 3M Perfect-It Heavy Gelcoat Heavy Cutting Compound (wool pad) followed by 3M Finesse-It II (foam pad) and finally 3M Perfect-It Wax (foam pad). I used the 3M Perfect-It Gelcoat Medium Cutting Compound + Wax last year and it didn't seem to cut very well so I figured I would try the heavy cutting compound this time around and finish it off with the Finesse-It II and wax.
• Meguiar's M6732 Marine One-Step Compound (wool pad) followed by the 3M Perfect-It Wax (foam pad). The M6732 sounds like it is more aggressive than the 3M Perfect-It Gelcoat Medium Cutting Compound + Wax so maybe I will get better results. Can I get away with a wool pad and then jumping directly to a foam pad with wax or am I gonna have the hologram effect from the wool pad?
• 3M Perfect-It Gelcoat Compound + Polish (wool pad) followed by the 3M Perfect-It Wax (foam pad). This two-in-one appears to be more aggressive than the 3M Perfect-It Gelcoat Medium Cutting Compound + Wax option and I'm guessing it's on par with the Meguiar'sM6732. Can I get away with a wool pad and then jumping directly to a foam pad with wax or am I gonna have the hologram effect from the wool pad?
• Menzerna Heavy Cut 400 (wool pad) followed by the 3M Perfect-It Wax (foam pad). The Menzerna doesn't advertise as a two-in-one but it does say that it leaves a high gloss finish. I'm thinking I may need to use the Finesse-It II before waxing. Can I get away with a wool pad and then jumping directly to a foam pad with wax or am I gonna have the hologram effect from the wool pad?

As I'm typing this it appears that I may have to use something in between the cutting compound step and the wax step (3m Finesse-It II) with a little bot more of an aggressive foam pad. Maybe use a foam pad for the first step like some of the more aggressive 3M offerings?

Once the season sends I plan on compounding, polishing, and then sealing with Rejex - this project is just to take care of the aftermath of the gelcoat repair and blend it in with the surrounding surface. I already own the 3M Perfect-It Gelcoat Medium Cutting Compound + Wax, 3M Finesse-It II, and finally 3M Perfect-It Wax which is why I'm sticking with the wax as the final step.

Thanks in advance for any feedback.

 

[Gap22]

I fixed all my issues this weekend. In my mind's eye I thought my biggest issue was going to need the Spectrum, so I got it, but when I went to get my boat from storage, I realized my being pissed off about it blew it up in my head. Ended up wet sanding by hand with a block. Didn't take too long really. Then used Meguiars all in one. Looks new. I would be scared to use a machine to sand, but that's just me.

Long story short, I decided to use the least aggressive method first, knowing I could step it up if need be, and it worked.

My boat is black btw

 

[WiskyDan]

Thanks for the reply.

So you repaired with Spectrum paste, wet sanded, and then used Meguiar's One-Step (M6732) and it was good to go?

 

[Gap22]

No, when I re-inspected my boat (it doesn't stay at my house) I realized I had over reacted, and the damage wasn't bad enough to require paste, so even though I had it, I didn't use it.

 

[WiskyDan]

Gotcha, thank you.

My scratches are a bit too deep to wet sand and buff but I'm glad that worked for you.

 

[Acard7]

I would wet sand by hand, that’s what I did with mine. Take your time! The spectrum white matched my boat perfectly.

 

[Dixemon]

How big is the area? if it is smaller than 10x10" i would say wet sand by hand, then mechanically cut and buff. A tecnique i have use in the past doing composite repairs and such is to use some metal flashing/ducting tape. Use this to outline the repair area, Careful its SHARP, this way as you are sanding you don't go out of your repair area. Before you know it you will be buffing out 2'x2' if you dont. Im no pro, but i will list out what i have used in the past that has worked for me.

-Dry (100/ 200 / 300) Wet 600/ 800/1000 /1500 with wood block or without, depending on flat spots or curves of boat. theres some nice foam sanding blocks out there. Such as the ones Dura-Block automotive finishing blocks. If you dont need to remove a lot of material start with a higher grit.
-3m Perfect-it Gelcoat Medium cutting compound + wax .on wool buffing pad( wetting with sprayer frequently)
-3M finess it II Glaze on wool pad, then switch to foam pad and hit it again.
- Wax of your preference.

You could easily use 3M's entire gelcoat repair line of products, they have step by step instructions on doing it.
Good luck

 

[tdonoughue]

For most true 'scratches', I would block sand (do not hand sand without the block--if it is curved, get a curved piece of wood to use and try to match the contour), then use the buffer for the compound and then polish. I don't know that anyone other than a pro will probably know/realize the difference between the products you list out--all look good and are well-reputed.

I tried to tape off on my first scratch repair. Taped too small of an area and wound up with nice squares that I had to buff out... Now I usually skip the taping but pay close attention and take my time sanding so I don't expand my area of repair. So, reasonable minds may differ on that.

Overall, I would recommend: don't overthink it, really. Once you do the first scratch, you are going to come back telling us all how easy it was (and hopefully outlining what you did to add to the body of knowledge).

 

[WiskyDan]

Thanks for all of the tips - I usually over think things and this appears to be no different.

I have three scratches to fix - ranging from five to eight inches long. All three are deep enough that they are through the gel coat but nothing crazy. One is pretty shallow so I think I will have to make that one a little deeper for the new gelcoat to be able to adhere to it from what I read on the Spectrum website.

I was planning on taping off the scratches with a couple of layers of masking tape based on some tips I’ve seen in other threads but will take it off once I get done rough sanding the new gelcoat.

Still kicking around which compound to use - a two-in-one or separate compound and polish.

Thanks again for the feedback.

 

[tdonoughue]

To widen: I recommend a Dremel tool with a cone-shaped bit. Worked wonders for me and you can adjust the speed to keep control.

Personally I prefer the separate compound and polish, just for more control. But not so strongly that I would not use the other... For what that is worth.

Oh, and we like pics.

 

[WiskyDan]

I’m gonna go with a separate compound/polish/wax process as recommended on the 3M website:

1- 3M Perfect-It Heavy Gelcoat Heavy Cutting Compound (wool pad)
2- 3M Finesse-It II (foam pad)
3- 3M Perfect-It Wax (foam pad)

I’ll take notes and some photos along the way.

 

[Dixemon]

I think youve got it covered there, whats the heavy cut? Like 1000 compond grit. You know if you mess up a little, you can go right back and fix your mistakes. Its forgiving.

 

[WiskyDan]

The heavy cut removes 800 grit and finer scratches.

 

[marcham]

Clean the scratch and remove all waxes/oils before applying gelcoat.

I usually go a little extra thick with the gelcoat, say 1/2 mm. Press it into the void scraping in 2 directions, to avoid air bubbles. I then wet sand with 800, 1500 then 2000 grid. Use lots of water and a small wood sanding block. I then use a polish /glaze and finish with wax (Rejex). Pay attention to catalyst ratios, it varies based on temperature.