finnishing sanding

ok I've sanded through 800grit, is it really nessesary to go to 1000 and up? Its smooth as a baby's but right now? One other delema, I have this one area that is every so slightly indented and it stretches for about 3in. You can't even notice it by touch but as soon as you prime it it sticks out like a sore thumb in the right light. Now I've tried to bring this area up 3 times with bondo and it just doesn't seem to want to level out, any suggestions? Its really frusterating I've spent too many hrs not to have this look perfect and this one spot is gonna make me flip!!ahhh!! any help would be apreciated! thanksgo custom or go home!!

Well my friend, welcome to the world of custom glass. The truth is, this is the down side to fiberglassing and paintwork, it's an exacting science and is time consuming. The finish sanding and pre paint prep is as you have discovered the most important step, and can make or trash the appearence of the job, no matter how much time you spend sanding to get it right. To level that low spot, go get yourself a tube of 3M or Evercoat glazing putty and lay it in over that low spot, leaving a noticable over fill of the area.Use a NEW/CLEAN filler applicator. You will need that to level the area properly. once the putty sets up(30 mins or less@70F)Wet sand that area with your 800 with THE FLAT OF YOUR PALM, NOT WITH YOUR FINGERS. If you have a rubber sanding block or pad, use that behind the sandpaper. With keeping the area well moistened, lightly sand that area until you have it almost level. Leave a little high to allow for additional finish sanding. Take the entire piece to 1200 to get it right for paint. Keep in mind, go EASY on the sanding pressure as you go up,and use the FLATTEST force behind the sandpaper as possible for the contour of the surface, if its not totally flat use a flexible pad or block. Keep your paper/surface wet and your paper clean. The rest is all feel. Use a black spray can primer as a guide coat and lightly dust the area you filled to check yourself between the 1000 and 12000 sanding. This will show you any high/low spots you may need to hit with the putty before you go to gun. I'd like to see pics of what your doing, please post some when completed if you can, and I hope this helps you. All the Best!elrock-SS

what i would do is take a lot (a lot) of bondo use a rubber glove and just plop a load on untill its over how much it should stick out. Let it dry. Scrape off and shape the mound with a razor then sand lightly where its needed then go on with blending it in with higher and higher grit paper untill it matches the rest of the box. If you do do this make sure to ruff the dip up good with some 60-80 grit paper so the bondo sticks well.dream it, build it, fiberglass it

Hi, just a little insight to this issue. I paint cars for a living and fishing with 1200 grit is a little over board. The way I do it is once you have your glass and putty all finished is you spray your encloser with a good highbuild primer. Give it 3-4 good coats. Spray your highbuild witha  guide coat. Strat by sanding with 320grit to break the orage peel down then step up to 400grit. Once you have it nice and straight then finish it with either 600 or 800 grit. The sand marks are light enough that anything will fill it. On cars I fish with 400grit for color and clear and 800 on just where I have to clear.

hbk, My place here is not to refute the skill of a tradesman who does bodywork for a living, but rather pass on the technique that will give you the results that will meet and surpass your expectations once you lay finish on your labor of love. On car audio pieces, which tend to stick out like sore thumbs good or bad, and I have had both in my 23yrs, 15 of which have been exclusive to doing fiberglass intagration in high end system installs of 35-100k. I have been laying and molding glass in just about any shape and form from molded dashes to complete interior panel regesignes, both painted,flocked,and covered in vinyls and carbon fiber. I personally strive to be a perfectionist, and have had to be because of what I was doing, and the dollars involved. My work has to look better than the exterior of the vehicle, and I had to do it without the time to do wet sanding and buffing afterwards, or reworking. Theres nothing worse to face after all that time spent. As I mentioned before, glass is a time consuming medium to use, and only get's easier to work with over time and frequency in working with it. If you want to insure the absence of the "walnut shell" look, consider what I am sharing.    So, I will tell you that the difference between 1000 and 1200 sanded on molded glass is noticable, and worth the extra step and time. Not to impune a fellow pro's technique, but I choose to leave no regrets on the back side to contend with. Bottom Line: Its really about what YOU want to achieve. My reccomendation was based on the best possible outcome, outside of laying the finish coat and clear properly. Again, I just do it a little differently. If you are interested in seeing the benefits of some finished product, I'd be happy to send you some pics of some jobs that "overkill" took to national and world championships. Its not about me tooting my horn about my way being better than anyone elses, with Masters like Dave Rivera and Joe Gross out there taking fiberglass to the outer rim, I'll humbly be in school the rest of my days!! I just respect the hard work you have put into what you have created thus far. You obviously have the burn and passion to create a unique and eye catching piece to have even committed to using fiberglass yourself. I just want to encourage the best outcome, so you will continue to do more with it, and not be dissatisfied with the results. After all, it is not at all cheap to go this route, am I right?! High build primers and spray polyesters are great and I use both, but also very costly if you are not doing production work. Elbow grease, patience, and technique are in most cases Much cheaper, and yes I use them equally as much, and in place of the other if and where I can. Done right, there is NOTHING more gratifying, and I know others will agree. elrock-SS

you know i agree with elrock. i would to, use 1000-1200 grit sandpaper. if you really want your set up to look nice for paint then i would to, go that extra mile to get all the imperfections. xTimx

I agree, if your going to spend HOURS on the project why not spend 1 extra one on the sandingdream it, build it, fiberglass it