Advice for polishing out scratch in gelcoat?

[gumpus]

My Merlin II is 20 years old this year so I decided to give her a thorough tune-up.

I often forget to tap into the expertise on this site before I do something so as I got started today I thought I'd ask for advice from anyone else that has done this. Specifically - did you go up to 1500 grit and then use a polishing compound? Which polishing compound? Any hints would be appreciated.

 

[deerfly]

Its not inexpensive but I've consistently had very good results with 3m products. I use the perfect-it line of polishes on all my boats and vehicles. The light cut gel-coat formula should buff out 1200-1500 level finish.

https://www.3m.com/3M/en_US/company...tting-Polish-Wax/?N=5002385+3291239710&rt=rud

https://www.3m.com/3M/en_US/company...rasive-Disc-260L/?N=5002385+3293241177&rt=rud
https://www.3m.com/3M/en_US/company...-Original-Series/?N=5002385+3293193949&rt=rud
https://www.3m.com/3M/en_US/company...ft-Interface-Pad/?N=5002385+3293241850&rt=rud

I wet sanded my northwind to 2000 using 3m 6" hook-it disc's with a 3/4 soft interface on a 3m ra orbital sander before polishing.
Can't see actual detail from the attached pic's but it polishes out to a mirror finish. These pics are before it was waxed, but I use 3m wax too

https://www.3m.com/3M/en_US/company...rmance-Paste-Wax/?N=5002385+3293194142&rt=rud

I'm sure you can use other less expensive systems and get great results too, but I've been using 3m systems for many years on boats and cars and couldn't give you much in the way of specifics on the other stuff. Just do a good job sanding, checking carefully before moving on to the lighter grits and make sure your buffing pads are very clean. Take your time and don't run the polisher too fast either.

 

[gumpus]

Thank you for taking the time to educate me deerfly. I didn't know that some of those products even existed. I have a Makita sander but need to figure out if I need a polisher.

In addition to 20 years of scratches the boat also has my first ugly gelcoat repair after I casually ran over a stick that turned out to be submerged concrete. Then as I was putting away the snowblower for the season it rubbed against the boat and I thought the squeaking noise was the plastic shroud of the snowblower against the boat but it turned out to be the sharp edge of a stamped bracket scraping the boat.

I do plan to take my time and I'll share more pics later this season.

Fortunately I spent almost a week refinishing all the wood trim right before I ran over the concrete so that part is done.

 

[Jim Dodd]

That is the problem with Gel coat ! A little scratch, and it stands out like a Sore Thumb !

Colored hulls like Red really stand out !

I question that your hull is gel coated ? At least not colored.

Beings your hull is black (Carbon) I might tape off the bottom, up to the 3 or 4" waterline, Mix up some Epoxy, adding Powdered Graphite, and roll on a coat !

I used to do this to strip canoes, that were destined for rocky rivers ! It does help ! Just don't leave it bottom side up in the hot Summer Sun, for a long time. I've seen it bubble.

You might entertain the thought of having a Auto Body shop spay on a Clear coat finish, if you are set on keeping it look original ?

Good luck !

Jim

 

[gumpus]

Thanks Jim. I never thought about ADDING gelcoat but that makes sense as another good option. My Merlin II does have a nice thick gelcoat so I plan to try sanding and polishing first. I'm not actually worried about ugly scratches, I just want to give the boat some love. I estimate I've had this boat out well over 1000 times. I agree that some colors show scratches too much and that's why my two Swifts are Champagne and in general I lean towards white or sand colored canoes. One good thing about ugly scratches is that they get you better prices on used boats...I bought two Bells with minor scratches for less than they were worth. Just FYI one trick I've heard for black/gold Bells with scratches in their clear gelcoat is to just wipe on black Kiwi shoe polish and then wipe off. I've never tried it since once you get past the first scratch they don't bother me.

 

[gumpus]

Just FYI Jim here's a pic of the impact point where I hit a concrete block and a couple of pieces of the gelcoat popped out.

​​​​​​​

 

[Jim Dodd]

OUCH !

At the very least, I'd break off the loose stuff, sand (not into the cloth), and recoat with epoxy. I'd be real temped to lay in a small patch, and feather it after the epoxy set, sand and varnish ! It would all depend on your feeling about appearances !

I'd shy away from any Wax !, As it might inhibit any resin from sticking later on !

Jim

 

[alsg]

Beings your hull is black (Carbon) I might tape off the bottom, up to the 3 or 4" waterline, Mix up some Epoxy, adding Powdered Graphite, and roll on a coat !

I used to do this to strip canoes, that were destined for rocky rivers ! It does help ! Just don't leave it bottom side up in the hot Summer Sun, for a long time. I've seen it bubble.

You might entertain the thought of having a Auto Body shop spay on a Clear coat finish, if you are set on keeping it look original ?

Good luck !

Jim

Do the all-black carbon-fiber canoes have problems with bubbling epoxy when left in the sun? If no, It is hard for me to understand why the epoxy on a graphite-infused black bottom would bubble in the sun.

 

[Jim Dodd]

OK. I should elaborate !

A good friend built a Cedar strip Tandem. The bottom was scared up pretty bad, so he opted to coat the Football area with a epoxy and graphite mixed in ! We have done this several times ! It does reduce the amount of scratches !

Anyway, He had left the canoe( with a graphited bottom) on top of his van, while it sat outside in the hot Summer Sun, for a month. Bubbles (large bubbles) developed in the Graphite coating.

This had nothing to do with a Carbon fiber canoe !

If you have a Factory canoe, with a graphited bottom? On the safe side ! I'd avoid leaving it bottom side up in full Summer Sun !

Jim

 

[gumpus]

OUCH
At the very least, I'd break off the loose stuff, sand (not into the cloth), and recoat with epoxy. I'd be real temped to lay in a small patch, and feather it after the epoxy set, sand and varnish ! It would all depend on your feeling about appearances !

I'd shy away from any Wax !, As it might inhibit any resin from sticking later on !

Jim

Based on the force of the impact and the hideous sounds I expect my boat to start taking on water so I think it's a testament to the strength and resilience of the black/gold lay-up.

I ended up taping off the two damaged areas (three holes total) and just filled them with clear gelcoat after some quick surface prep.

 

[BWCA66]

Are you sure there is a clear gel coat on your canoe? There is a difference between clear gel coat and a skin coat, can't imagine this has the added weight of clear gel coat. Just my thoughts.

 

[gumpus]

I used to be 100% sure but you and Jim have me down to 98%. I may ask my dealer since I may see him this coming weekend. I have a Northstar Polaris with skin coat and it looks like a skincoat. I may try to find an old Bell catalog...but check out the pic of the holes...if it's a skin coat it's about 1 mm thick! And for sure it adds weight...my Merlin has always been way over it's advertised weight of 36 pounds...it's closer to my Polaris tandem. In my experience lots of older Bells are around 4 pounds over advertised weight.