Removing fine scratches from fenders on black gelcoat?

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Swg

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Well, if I knew then what I know now I wouldn't have bought a black boat, used fenders or even thought about sailing. Happily I was ignorant! The fenders have put very shallow scratches into the hull and I'd like to remove them. Whilst they would cover with tcut I want a proper solution which will last. I need clear and specific instruction on materials/ machine and process and if you can, where to buy. I live nr Edinburgh and as far as I know there is no local roaming boat polisher so it's down to me. Can anyone advise?
 
Wow, that could be a big ask! There is a risk that polishing will lessen the opacity of the black layer, so go carefully. I like to use Farecla polishing compound, either with a slow rotating polisher or by hand. To make it last, get yourself a fender blanket so the fenders roll against the blanket rather than the hull.

Rob.
 
The simple and safe method is to use a 300 grit sand paper and give the areas a light sand after cleaning it with a little Acetone to remove and old polish or way.

Give the area another wipe with Acetone after cleaning.

Get yourself some black flow coat and apply with an old credit card so the finish is just proud.

Let this cure for a few hours and sand back using wet and dry sand paper wrapped around a small flat block of timber.

Start with a 600 girt to remove the bulk, then a 1000 grit and finish with a 1500 grit.
Keeping the area wet at all times with fresh water not salt.

Then polish to match the rest of the hull.

Good luck and fair winds. :)
 
A quick fix would be to use that coloured car polish, Color Magic I think it's called, available in a range of different colours.
 
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we have a black boat also & when we got it both sides were as you describe I machine sanded the worst with a random orbital sander with 800 grade disks then machine polished with farecla g3 or g7 on a foam g mop with a 2000 rpm machine & then waxed with a marine wax the results were stunning

you can hand sand with a block with wet & dry if you dont have access to a suitable sander but its hard work

buy a decent polisher about £150 i think (i've had mine 10 years) & wouldnt be without it

with the exception of the marine wax all the equipment is available from automotive paint factors at much cheaper than the marine equivalent (dingbro,brown brothers etc)

unless the scratches are deep theres no need to fill with gelcoat as the origional is fairly thick, much thicker than the paint on a car

hope this helps
 
Swg said:
Well, if I knew then what I know now I wouldn't have bought a black boat, used fenders or even thought about sailing. Happily I was ignorant! The fenders have put very shallow scratches into the hull and I'd like to remove them. Whilst they would cover with tcut I want a proper solution which will last. I need clear and specific instruction on materials/ machine and process and if you can, where to buy. I live nr Edinburgh and as far as I know there is no local roaming boat polisher so it's down to me. Can anyone advise?
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You could just try some 1500 paper, then rub by hand with some compound, but it's a cats lick.

If you want to use machines and fancy shelling out then feel free, they do have big advantages, but unless your doing it every day save your cash, by hand is very simple and will only take a little while longer.
I guess a machine polisher would be very helpful and is a good investment for every boat owner, but a DA sander would be an overkill, unless of course you intend to keep on sanding scratches out and not address the problem of whats causing them.

I did some last week and just happened to take some photos.
With the shallow scratches in the pictures for example I did the sanding by hand, as it wasn't worth getting the DA out of the van and setting it all up for such a small area.

A rough guide:
First - cleaning. You need to take out all old polish, dirt (small grit particles) anything that may cause a problem. Several passes with acetone will suffice. Gloves, mask and eye protection.

Highlight the scratches by using a dry guide coat (important) this is simply a fine powder that gets into the scratches, you can buy white or black, it will show you the depth of the scratches, also it will show you how well you are doing at removing them and at what speed.
A bit of experience is needed to judge what grade of paper you need to start with, but as a rule of thumb and certainly for first timers - start with the finest first. When I say fine, I am talking of 2500 - 3000 grit, it will feel nearly as smooth as normal paper, but trust me it will work, it just may feel like it's taking forever!

Tip.. soak the paper in a warm (grit free) bucket of water for 20 mins or so, to make supple.
Wrap the paper around a flat smooth rubber block so you are working the area flat and smooth at the same speed all over, using fingers only on contours if you don't have shaped rubbers.

With a misting spray of water with a few drops of washing solution (to provide lubrication to the paper) work the paper back and fourth in same parallel lines, if you change grit, change direction of travel. This way you will see if you are removing the previous grade scratches (if you are using multiple papers).

Check to see if any of the scratches have been removed by re applying guide coat, to speed things up a bit move down to a more aggressive grade, perhaps 1500, then do the same, but be careful, common sense will tell you if you are going too deep, rather work the area for longer with a fine grade than go through into the fibreglass. If it starts to show up speckles of a different colour, it's way too late and you are almost through, you now need to add more gel coat. Start with 240 grit if you want, but you can kiss your gel coat goodbye.

Another reason for this cautious approach of 'finest first':
You will need to recover from any 'scratching' you invoke yourself with the papers. So if wanting to do the job in minutes and get to the bottom of the scratch depth, you rush it and you start with say 600 and work it to the point where the scratches have been removed, you then work progressively with higher grades to remove the 600's scratches, so then say 800, then a 1000. then 1200, 1500 possibly finishing with polishing (if you have a machine) if not you will need to continue with 2000 -3000. All of this will be risking the depth of your gel coat. There are some who will start with 600 say, remove the scratches and move directly onto polishing for a shine, this will only fill the 600's scratches not remove them, they will return in a few months and the reflection just won't have any clarity.
So start with the finest possible and work down to the depth of the scratches with this, when you have reached the depth of the scratches it will be very easy to recover from. The compromise will be time, with experience you could easily move to more aggressive grades before reaching the true depth of the scratches, start working up the grades to recovery and reach the full depth by the time you have moved onto polishing.

If you have got the above and have removed the scratches safely, you now should be looking at a matte finish that just needs polishing to restore the shine, any medium compound will work.

You can also use a 3M Sun Gun (bright light) in order to highlight even more shallower scratches that powder wont get into.

One method to stop it happening again (apart from keeping fenders clean of course) is to check them for sharp bits, some do have bits that are sharp enough to create scratches over time. A rub down with acetone can help smooth them a little, or if need be some sanding and polishing to the fender itself.

Where to buy all the above? 3M

Click pictures to enlarge.

Before sanding
View attachment 29016





After sanding, but before polishing.
View attachment 29015
 
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tudorsailor said:
So if my fenders have scratches, which grade of paper should I use to get rid of them?

TudorSailor
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It was regarding any sharp points on the fenders where formed, or nibs on the fender that can be smoothed down a little that I was speaking of.
Scratches on fenders, light ones, can be improved a little with acetone if the fender can handle it. In most cases it will clean out the scratch making it virtually invisible.
They are not going to cause the hull a problem as they are in the fender and not standing out of the surface causing scratches in the gel coat or paint finish.
 
Marine Reflections, thanks. Really good of you to take the time to be so descriptive. 'Looking forward' to the weekend!
 
Think ill do the scratches by hand, there atent many and it would be 'safer' but might any to invest in polisher. Could you recc. a polisher/ heads?
 
you dont need to spend that kind of money for occasional use check out this one http://www.ebay.co.uk/itm/Silverlin...ssories_Car_Care_Cleaning&hash=item230ad4f207

or ebay no 150505583111

you need to run about 2000rpm to prevent heat build up & heads are readily available we just use g mops which are available from good motor factors

I dont like velcro heads as the pads can whip off if you catch a cleat or something then potentialy doing damage with the backing pad
 
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