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Old 26-07-2013, 16:38   #16
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Re: Maintaining Fibreglass - 2004 Cat

If you get wax deep into the gel coat and then chose to paint in a few years, how painful is removal? I've painted a few boats, but never one that had been waxed recently.
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Old 26-07-2013, 16:48   #17
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pirate Re: Maintaining Fibreglass - 2004 Cat

I've found the cutting paste used for cutting back the paint on cars very good... slap blobs on the hull (in sections) and attack with a buffer... wash off residue and wax
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Old 26-07-2013, 21:11   #18
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Re: Maintaining Fibreglass - 2004 Cat

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Originally Posted by colemj View Post
I can't imagine what gelcoat dry sanded with 180 grit looks like. Even dry sanding with 600 must leave it a mess of scratches. Wet sanding with 1000 can make pretty fast work out of moderately oxidized gelcoat. I don't think dry sanding would work at all.

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I dry sand with a random orbit sander up to 8000 grit (yes you read that right). Works great, just requires the right equipment. Wet sanding at very fine grits is only necessary if the product in question is not fully cured and hence slightly gummy. Dry sanding with the DA is much faster and cleaner than wet sanding. A dry guide coat can be a big time saver.
Couldn't agree more with your assesment of grits though. I often start with 800 myself. Anything coarser takes too long to polish out.
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Old 26-07-2013, 22:36   #19
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Re: Maintaining Fibreglass - 2004 Cat

WOW! 8000 grit. Why not just silver it if you want a mirror. :whistles:

I use to fab and install polished stone for some pretty high end homes. Even then I didn't go beyond 2400 grit paper and jeweler's rouge.

PSA: For those who do wet sand don't be 'that guy' and use electrical hand tools. And pay attention to that water you're standing in. Be watchful that some chucklehead didn't drop his electrical cord nearby.
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Old 26-07-2013, 23:16   #20
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Re: Maintaining Fibreglass - 2004 Cat

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Originally Posted by Richard5 View Post
WOW! 8000 grit. Why not just silver it if you want a mirror. :whistles:

I use to fab and install polished stone for some pretty high end homes. Even then I didn't go beyond 2400 grit paper and jeweler's rouge.

PSA: For those who do wet sand don't be 'that guy' and use electrical hand tools. And pay attention to that water you're standing in. Be watchful that some chucklehead didn't drop his electrical cord nearby.


Oh, I agree, not much call for anything past 2000 (Corian). Just mention it to demonstrate how high you can go dry sanding.


Festool 492372 S4000 Grit, Platin 2 Abrasives, Pack of 15 - Amazon.com


This is what I'd recommend starting with on oxidized gel. A box will do your hull twice over (unless your boat is huge).



http://www.amazon.com/3M-260L-Stikit...000+grit+discs


If you're a pro and you do paint blends you start stepping up to stuff like Trizact.


http://www.amazon.com/3M-Trizact-Fin...psa+attachment
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Old 26-07-2013, 23:30   #21
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Quote:
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WOW! 8000 grit. Why not just silver it if you want a mirror. :whistles:

I use to fab and install polished stone for some pretty high end homes. Even then I didn't go beyond 2400 grit paper and jeweler's rouge.

PSA: For those who do wet sand don't be 'that guy' and use electrical hand tools. And pay attention to that water you're standing in. Be watchful that some chucklehead didn't drop his electrical cord nearby.

Interesting, when I was a granite counter top installer we did exposed edges to 5 or 8k and a buff. Dry usually, no rouge.

Gel coat 800, 1000, imperial compound then finesse it(if going the extra step)
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Old 27-07-2013, 00:33   #22
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Re: Maintaining Fibreglass - 2004 Cat

Most all fab work was wet. The only thing that was dry was using Alpha pads. I don't rightly recall all the different grits but they sure were fine. Maybe they were 5000 grit or more. I had a standing order with vendors and as the man wearing all the hats I found it convenient to not have to stop to place material orders.
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Old 27-07-2013, 02:19   #23
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Re: Maintaining Fibreglass - 2004 Cat

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I never sand gelco if I am going for the aesthetics. Soap/Wash/Wash it down very, very well, let it dry then apply plain car wax (without rubbing compounds) and buff. Then apply more wax and buff again. Then look.

If at this stage your gelco looks dull, only now it is the time to consider a more radical method.

I have never found any superior wax but I found that some apply better than others. I prefer gel/thick over liquid. Avoid working in sun/heat too - the wax will dry instantly rather than soak into the gelco. Early mornig / late evening best time IMHO.

I wax/buff by hand, but if you have big/flat areas on a bigger boat, go with a power tool.

b.
thank you for your help so many different opinions but at least I think going the easy option first is a good one so thank you
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Old 27-07-2013, 03:21   #24
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Re: Maintaining Fibreglass - 2004 Cat

I would do a test piece first, start with the rubbing compound and a polish and see what that looks like. The odds are that it will look ok, but that if Gelcoat too stuffed the shine will not hold.

Not the greatest of experiance with this sort of stuff (never been that fussy!), but have done a bit of experimenting over the years on bits and bobs....seems that pretty much all cutting compounds do the same job (and have the same limitations), whether marine or auto (and even Brasso!)....comes a time when you need something that abrades more. One of the "Tricks" is to make sure you know how deep the gelcoat is!
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Old 27-07-2013, 08:32   #25
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Re: Maintaining Fibreglass - 2004 Cat

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Originally Posted by minaret View Post
I dry sand with a random orbit sander up to 8000 grit (yes you read that right). Works great, just requires the right equipment. Wet sanding at very fine grits is only necessary if the product in question is not fully cured and hence slightly gummy. Dry sanding with the DA is much faster and cleaner than wet sanding. A dry guide coat can be a big time saver.
Couldn't agree more with your assesment of grits though. I often start with 800 myself. Anything coarser takes too long to polish out.
I was only considering hand sanding with a dry block, since I was comparing it to wet sanding. My experience is that hand sanding dry gums up the paper too fast and makes slow work.

I agree that a RO would work fine, but would not recommend this to someone who has never worked on gelcoat before.

Mark
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Old 27-07-2013, 09:11   #26
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Re: Maintaining Fibreglass - 2004 Cat

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Originally Posted by colemj View Post
I was only considering hand sanding with a dry block, since I was comparing it to wet sanding. My experience is that hand sanding dry gums up the paper too fast and makes slow work.

I agree that a RO would work fine, but would not recommend this to someone who has never worked on gelcoat before.

Mark


I certainly would recommend DA sanding to the novice, particularly when combined with a dry guide coat. Ten times as fast (or more), and gives better results. I have taught laborers who couldn't read to do this, the average sailor who has learned to navigate should be able to handle this no problem.
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