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Author: Subject: Removing scratch from gel coat
Bigboystoys

posted on 9/1/18 at 08:59 AM Reply With Quote
Removing scratch from gel coat

Morning all, I have a small scratch on my dax rush gel coat im keen to remove, I have tried t cut scratch remover but it's a little too deep, what's the best method after this??

Many thanks

Sam

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joneh

posted on 9/1/18 at 09:31 AM Reply With Quote
My Grandad used to repair gel coat on busses by mixing a little gel coat with hardener and then using cellotape as the mould.
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jossey

posted on 9/1/18 at 10:07 AM Reply With Quote
Above method works but best if it's on the top not sides.





Thanks



David Johnson

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russbost

posted on 9/1/18 at 10:27 AM Reply With Quote
Providing it hasn't broken thro the gel into the sub surface then you can simply flat it out & polish. Start with something like 600 or even 400 grit wet & dry, use wet with some wash up liquid in the water as a lube, & once the scratch is barely visible work down the grades to 1200 & 1500 then polish using a coarse abrasive, Farecla G6 springs to mind, but can never remember which is coarser, G3 or G6. Finally T cut & polish, it should be invisible.

If it's broken thro the gel then repair as previous comments & then flat back & polish to get an almost perfect finish, unless you are lucky enough to get a perfect colour match you will probably still see it if you know where to look, but still much less obvious than a scratch





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Charlie_Zetec

posted on 9/1/18 at 11:45 AM Reply With Quote
As above, but I wouldn't use T-Cut on gelcoat; sometimes the ammonia content can affect colour finish. There are other specialist products (Farecla has already been quoted), but Meguiars also do a GRP-based range aimed at RV's and marine industry.

Remember that the gelcoat is the UV surface finish, and the equivalent of paint on a car - once cut back/down or removed, you can't easily put it back on! If you're going to cut it back, just remember to put a coat of suitable wax or similar back on to slow down the UV degredation rate and maintain colour/appearance.

If the scratch has burst through the gelcoat to the glass/resin backing, you might need to consider having it professionally filled - speak to your local GRP specialist or marine repair engineer, who (if they're any good) should be able to get a good colour match and fill/smooth it in and make it look good again. But be prepared to pay for it. You can try it yourself if you're feeling brave, but I've seen plenty "give it a go" after watching a YouTube video and end up ruining panels by taking too much off or getting surface burn from the use of polishing machines.





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nick205

posted on 9/1/18 at 11:57 AM Reply With Quote
Which panel is the scratch on - could it be cheaper/easier to get a new panel?
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Bigboystoys

posted on 9/1/18 at 12:25 PM Reply With Quote
Thanks for replies, unfortunately Nick it's on the main tub, it's hardly noticeable as it's down next to the right silencer bolt but I know its there and just wouldn't mind having a go at removing.
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jps

posted on 9/1/18 at 02:52 PM Reply With Quote
Sorry to hijack - but are the methods described basically the same for repairing hairline cracks in the gel coat too?

I'm assuming you'd perhaps grind out the hairline crack slightly to open it up enough to receive some material, then fill back as though it were 'just a deep scratch'

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Charlie_Zetec

posted on 9/1/18 at 03:16 PM Reply With Quote
quote:
Originally posted by jps
Sorry to hijack - but are the methods described basically the same for repairing hairline cracks in the gel coat too?

I'm assuming you'd perhaps grind out the hairline crack slightly to open it up enough to receive some material, then fill back as though it were 'just a deep scratch'


Depends on what you'd call "hairline cracks" - gelcoat is prone to spider cracks, often caused by either stress, flexing, or impact. Without resolving the underlying issue, these will quickly re-appear. But in principle, yes, the gelcoat filling after opening up the crack line is the easiest fix. After that, dry sand, wet sand, and then wax. Always wipe the area after opening with a cleaner such as acetone before in-filling, and check there's no moisture in between layers that will cause the material to fail to stick (research Osmosis).





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jps

posted on 9/1/18 at 03:32 PM Reply With Quote
quote:
Originally posted by Charlie_Zetec
quote:
Originally posted by jps
Sorry to hijack - but are the methods described basically the same for repairing hairline cracks in the gel coat too?

I'm assuming you'd perhaps grind out the hairline crack slightly to open it up enough to receive some material, then fill back as though it were 'just a deep scratch'


Depends on what you'd call "hairline cracks" - gelcoat is prone to spider cracks, often caused by either stress, flexing, or impact. Without resolving the underlying issue, these will quickly re-appear. But in principle, yes, the gelcoat filling after opening up the crack line is the easiest fix. After that, dry sand, wet sand, and then wax. Always wipe the area after opening with a cleaner such as acetone before in-filling, and check there's no moisture in between layers that will cause the material to fail to stick (research Osmosis).


Cheers - yes my situation is basicaly that, in dry fitting my GRP side panels (before I trimmed them up properly) I did force them more than I should have - and introduced some hairline cracks in the places where I was effectively 'stretching' the panels too much. The underlying stresses on the panels are now sorted - and they'll be rivetted/bonded firm to finalise positioning them - but I would like to sort the minor cracks for cosmetic reasons when I get to it.

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Irony

posted on 9/1/18 at 03:44 PM Reply With Quote
Some good info on here. You will have to judge how deep it is and experiment. I have had reasonable luck is just using Salvo Autosol on gelcoat scratches myself.

That is a lovely rush in your avatar by the way. Shame they went under.

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ash_hammond

posted on 9/1/18 at 04:49 PM Reply With Quote
Following







.: www.mac1motorsports.co.uk | www.m1moc.com :.

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russbost

posted on 9/1/18 at 06:05 PM Reply With Quote
A crack is a whole different ball game to a scratch in that you have an underlying structural defect in the gel & possibly the matt under it. If it's very slight then just opening the top of the crack into a tiny "V" then painting in some correct colour gel/hardener & flatting back might hold it, but if at all substantial then as said you need to open it up to the matt, grind/sand away the damage & then fill back up with matt/resin/gel as required.

Much more difficult to get a good repair without painting or flowcoating a substantial area

If you could wrap the area to create a colour scheme that was pleasing on the eye rather than looking like you are trying to hide something, that might show the crack as a small defect, depending on how bad the crack is, but would certainly mask it to a large extent unless it's really nasty - might be a cheaper/easier way to approach it?





Furore Formula Car - the only two seater modern Formula Car lookalike. I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours. http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1

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twybrow

posted on 9/1/18 at 08:48 PM Reply With Quote
Gelcoat is very forgiving stuff - far more so than paint. If the gelcoat is scratched, then rub down making sure you do not rub down into the substrate (gfrp) below it. If you do, you have a major headache on your hands to get a smooth finish. Once rubbed down to remove the scratch, polish with wet and dry (wet) and make your way up the grades, then polishing compound (I love Farecla products for this). If you use a polishing mop, make sure to do so wet, and do not work an area for long or you will build up heat and discolour the gelcoat.

If you have a crack, then you need to assess why, and how deep it goes. If the reason for the crack is not dealt with, it will crack again. If it is just that you dropped/bent a part, then then hopefully the underlying laminate substrate is sound, and you just need to repair the gelcoat. Start by drilling out the very end of the crack to ensure it does not spread. If you miss this part, the crack will reappear. Next, using a die grinder open up the crack to give a slight v shape. If you do not do this, again, the crack is likely to come back. Fill the crack with catalysed gelcoat, building it up in layers if needed (dont be tempted to try to fill a deep crack in one go, as it shrinks as it cures. Fill so the gelcoat is proud of the surface. Next, follow the same procedure as for the scratch above, ensuring you use a block or similar to get it all nice and flat. Work through the grades, then polish. You should be able to get a seamless blend (so long as your original gel is not too faded, and you are able to source the same colour gelcoat).

If you have to repair the fibreglass/substrate, then this is a bigger job which I have covered on another post somewhere (use search). In essence you need to gut.grind out all of the damage, and then construct a simple tool surface on the gelcoat side (plastic, melamine, tap etc can all be used). You then work from the substrate side, and apply gelcoat (having prepped the area by grinding the edges to a chamfer first). Then once the gelcoat is the right thickness, layup the grp (or whatever you are using) onto the back, ensuring an overlap not less than 1/2 as much again as the hole diameter. Once cured, remove your mouldiung surface from the gelcoat, and finish as above.

I have repaired brand new Sunseeker yachts where we have had to cut out half the side of the boat, using just such methods. It is very forgiving if you are able to get hold of some of the original gelcoat, and very easy to polish out minor scratches with not much more than wet and dry and some elbow grease.

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Bigboystoys

posted on 9/1/18 at 09:46 PM Reply With Quote
Thank you all for taking the time to write such detailed answers very grateful
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