Sanding And Preping for GelCoat

[Fibertron]

ive got my boat flipped and am ready to start sanding, how far down do i need to sand for new gelcoat and what grits of sandpaper should i use? Also how should i clean the boat before sanding, is varsol ok? Thanks

Bryan

[Dean Dorsey]

Did mine last spring, I was told to prep sand with 220 to make sure a good bond was formed. In retrospect it think 280 grit would have been fine, just as long as you are consitant over the whole area. Good light and compressed air helps alot to maintain a clean working area to gauge your work. No need to go to deep just consistant with no shine left anywhere. For cleaning I think other than air I used mineral spirts, I think any mild solvent that does not soften the orighinal gel but will remove wax and any other contaminants is fine. Before you spray or roll the new Gel on use a few tack clothes on the surface. The real fun begins when you begin sanding your new gelcoat, be extremely careful as it is easy to go to deep and ruin your job I know! Allow a few days to dry, don't sand with anything rougher than 280 grit on the other end to start, but start with scotchbrite to get rid of the blush on top if you have any. That for me was the biggest pain in the ass . I used grits 280, 400, 600, 800, 1000. and 1500, then used a heavy cut buff to finish a cotton wheel on buffer worked better than a wool one for me. Probably over kill on grits but looks great. Labor of love but worth it when done. Good luck shoot me mail if I can be of any assistance. Dean

[Superdave]

I use 80 - 100 grit for prep. DO NOT USE A TACH CLOTH. It will inhibit the gel from sticking. Don't wipe with acetone or any other solvent before spraying for the same reason. This Duratec stuff is expensive, but saves soooo much time in the end.Duratec

[Dean Dorsey]

I won't say that dave's way is errored but have found and have been taught this. If you have a solid old gel surface you are working from 220 grit work fine for adhesion, if not or it has been cleared than other grits will accomplish the work faster. Different articles will recommend different starting grits for prep. Down side of coarse grit on prep is that is is tougher to get a good consistant surface unless you have to take it all the way to the glass or close. It is easy to create ridges and uneven surfaces than you won't see until you come back to sand the finish surface and buff, coarse grit will also create deeper grooves that will be very difficult to clean small particles of sanding dust from, which will affect adhesion and finish on the other end. If you decide to use a coarse grit, a thin coat of light colored easily removed guide coat that contrasts with your present color helps to see exactly where you have sanded, helps eliminate the ridges that can occur. This would hold true with the mulitple grits all the way to finish, pain but pays dividends. wipe on window paint at Wal-Mart works great (Auto Section). Regarding the solvent thing I have never had a problem as long as it does not soften the gel and does not leave residue so choose carefully, if you use contrasting guide coats for sanding you will need something to efficiently remove residue after each sanding coat. On Tack Cloth I thought the same as Dave due to the wax content of the cloth. Secret is to use it with an ever so light touch as to not transfer wax to the prepared surface. You will be amazed at the amount of stuff the cloth picks up even in a spray booth after you have done multiple cleanings, I think that this would be even more important if a coarse grit was used leaving deep grooves which is great for adhesion but not if sanding particles are left behind. Particles left behind will affect adhesion and help create pitting and tiny bumps that will need to be fixed at the end of your job, not what you want to see in the buffing process. Different ways to come to the same end. I have always had perfect results when following these procedures. Just my personal experience. Dean