gelcoat instructional

Yes mostly to bondo. Actually used thickened empoxy mostly. Used bondo as a final skim coat as it is easier to use. If you go bondo, you need a good mechanical bond so the surface must be roughed up well.

The video showed how to fill a scratch through the gelcoat only. In this scenario, no filler or bondo is needed and just gelcoat can be used. I agree, by using the putty to fill the void, then there is no room left for the gel and mostly likely you will sand through it when trying to level during sanding.

Yes, a tracer is a light coat of spray paint (I use black enamel) that shows when you have removed all sanding marks from the previous grit of paper used. It also shows low spots or voids. I trace between each grit of paper. After sanding with 400, I stop using a tracer.

Another important thing to do when filling scratches is to open up the scratch with either course paper or a dremel tool. What I mean by open is to make the scratch a pronounced "V" shape. The "V" gives the new gelcoat a longer edge to bond with. Sort of like butt joining wood...you would cut a 22.5 or 45 degree bevel to give a larger glueing surface for a better bond.

I watched the video and very glad I did not see that when I repaired by boat. IMHO (slightly experienced), that video makes it harder than it needs to be. If the scatch is simply in the gelcoat, why go to the trouble of using gelcoat putty and then gelcoat. Just use gelcoat. Fill the scratch with gelcoat cover with clear packign tape so the surface cures (something neglected in the video) and then start the graduated sanding process. The video also left out information on tracers. How in the world can you know how your sanding is progressing without a tracer????? UGH!

Thanks for the tip. That is my next project.