refinishing gelcoat

Discussion in 'Fiberglass and Composite Boat Building' started by nevilleh, May 29, 2009.

  1. nevilleh
    Joined: Sep 2008
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    Location: scotland

    nevilleh Junior Member

    Guys,

    Im really tearing my hair out with this one.

    We have just popped a new boat out of a fairly rough mould.

    It was my intention to have the guys take the whole thing back with P1000 wet paper and then buff up.

    So we used P1000, then P1200 then P1500 (by hand)

    We then put on (by machine) an abrasive rubbing compound called Farecla Profile 100 which advertises that it will take away from 800 - 1000 grit. Then after that Farecla G3 to get the gloss finish before waxing.

    Well we wheel the thing out side and we can still see the damn marks that we have made with the P1000 - P1500.

    I really cant believe it, ive never had this problem before.

    Would anyone reccomend taking it up to P2000 before going on with the rubbing compound?

    Im really pulling my hair out with this as its taking us hours !

    Thanks in advance guys.

    Neville
    Scotland
     
  2. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    sanding scratches

    I can believe it,

    I have sanded and buffed quite a bit of gelcoat, and most definetly it has happened to me.

    Couple things, I don't think the compounds work as well as advertised when they say they remove p800 or p1000 scratches, maybee if you do it a couple times and are really good with the buffer.

    Other thing I see is that you have to make sure you have completely resanded your 1000 with the 1200 and rinsed and wiped all the old abrasives of the hull, use a lot of water to irragate/rinse the gelcoat while sanding.

    I don't think I would wetsand 2000 right away, take a really good look at some different areas and determine what kind of scratches you have, they could even be from your buffing pad, and the compound dried up on you while buffing.

    I have chased scratches and it can be very frustrating, step back and refine your process on a smaller area, then repeat over the whole area.
     
  3. nevilleh
    Joined: Sep 2008
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    Location: scotland

    nevilleh Junior Member

    Thanks for your reply. I am going to get the guys to do another trial probably using 1000 - 1200 - 1500 - 2000 and then the paste. The paste is the most abrasive I have ever seen so I am really surprised it isnt taking it out.

    I really pester the guys to make sure they change the water frequently so it shouldnt be that - they used to be quite bad for using dirty water / dirt on the paper, hopefully they are aware now.

    I was wondering about using a scotchbrite type plastic pad instead of the 2000 grit, im not sure which to use. As you say trial and error on a small patch first.


    Thanks for your input.

    Neville
     
  4. nevilleh
    Joined: Sep 2008
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    Location: scotland

    nevilleh Junior Member

    I think also the issue may be the colour. It is a dark crimson red / maroon.

    We are at present rubbing down by hand (with the exception of the rubbing compound), the way we have always done it but I am now considering using machine for sanding.

    The main reason for doing it by hand is that with a machine the gelcoat can be rubbed away & damaged quite easily.

    My guys are laminators, and very good at laminating. outside of that they are not very good at gelcoat repairs, fitting out etc.
     
  5. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    I'd love to be able to give you a set method of getting it to look perfect, but there are so many variables involved its very tough to do.

    I've seen gel coat that is far harder than you can ever imagine, there can also be issues with the sand paper, like the grit size not being in spec, or being soft. The buffing pad can also affect what the finish looks like, so changing to a different brand or batch of each product may help.

    Try an area with a DA sander and see how it turns out, sometimes it makes a big difference.

    I did a patch and repair class for a group of fabricators and we had the rep from Farecla come in and demonstrate exactly how to use their products. He did a great job and most of the companies that attended now use their products.
     
  6. AroMarine
    Joined: Jul 2005
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    Location: Atlantic City NJ

    AroMarine Junior Member

    It is possible that your guys have passed over areas without a complete sanding. Are you using penciling or layout dye etc to ensure complete coverage?
     
  7. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    compounds

    With a very aggressive compound you should be able to sand only to 1200 and remove your scratches.

    Generally you want to start with a white twisted wool pad like a 3m supper buff, since it is a dark color and probably will show every thing then a follow up with a "yellow" 3m super buff and a polishing compound like 3m finess it 2.

    Even if you guys can get really good coverage and sand down to p2000 on your initiall sand, you will probably still have to do a finishing polish with a soft pad a light compound or polish to remove your swirls.
     
  8. Jimbo1490
    Joined: Jun 2005
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    Location: Orlando, FL

    Jimbo1490 Senior Member

    Superbuff Rules!

    Tip of the day:

    Don't use the 3M superbuff adapters. They make great paper weights and are also useful for stabilizing teetering workbenches. Instead, simply buy a standard 5/8-11 nut and thread it onto the spindle of the buffer, then install the Superbuff pad. You will be rewarded with a substantially shorter height tool which is far less prone to chatter and easier to use one-handed.

    Jimbo
     

  9. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    buff

    Jimbo

    that is a good tip on the spindle nut VS the adapter

    thanks
     
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