Filler for small holes and scratches.

[Slackwater]

What is the best filler for small holes and scratches to use before painting?

I have some small scratches from rocks and one or two small puncture holes may have gone slightly into the canvas.

I have seen posts mentioning using Bondo spot putty, Epoxy and custom made fillers.

I have some West Systems epoxy and high density filler that I was considering using for the small holes but I wasn't sure if this would be the right filler for the scratches.

Thanks for any advice.

 

[Greg Nolan]

I have used both Bondo spot putty and epoxy for such small pre-painting repairs. Either will do the job,but the spot putty is much easier to work with. Epoxy will cure harder than existing paint, and so is difficult to sand fair to the surrounding paint -- you pretty much have to get the repair smooth and fair when applying.

When dry, spot putty is about the same hardness as paint, or a tiny bit softer, so is readily sanded smooth and fair. It drys very fast, much faster than most epoxy cures. A deep scratch or hole might require more than one application, but even then, it will probably be ready to paint faster than epoxy. It cleans up easily with lacquer thinner or acetone; it's one-part -- no mixing, no adding fillers. Regular Bondo used for filling dents in auto body work (a 2-part polyester compound) is apparently not waterproof enough to deal with extended submersions, but I have had no such problems with the spot putty. It's cheap -- $5 or less for a small tube, and about $10 for a one-pound tube -- and is available in most auto supply stores or from Amazon.

Having used both, I would go with the spot putty next time I have such a job. My 2 cents . . .

Greg

 

[Todd Bradshaw]

Epoxy filler is composed of some sort of powder mixed with just enough epoxy resin to stick it together. Its sandability and hardness is much more a matter of which filler it contains than the epoxy itself. Using your existing WEST epoxy, you can either make a fill which is very easy to sand down smooth, or one that is quite difficult to sand, especially without tearing up the surrounding area or leaving a high spot. Their high density filler will make one that is very strong, but not at all easy to sand. Their other fillers (407 or 410) sand much easier and would work quite well. The 410 is the lightest and softest, but suggested for use on surfaces that will be painted light colors (heat problems under dark paint colors). The 407 microballoon filler is a better choice under dark paint and won't give you those problems.

In either case (or with just about any filler) you want to use enough filler powder in your mixture so that a test sample on scrap will hold its shape throughout the entire hardening process, rather than sag out after a few minutes into a pool of goo. This requires a ratio with a fairly high amount of the powder and a rather small amount of resin. Test it before using it on the boat.

Bondo can work, but it really isn't very high quality stuff and epoxy-based fillers are generally much better in the long run due to lack of eventual shrinkage, much better resistance to water and much better adhesion. The best pre-made filler product of the sort that I know of is Interlux Watertight. It's two cans of paste that you mix together a dab of this one and a dab of that one and apply it. It's pretty foolproof, epoxy-based and it sands and feathers out beautifully (better than anything I have been able to mix myself). It is not cheap, so a can would be an investment, but if you're going to be needing it once in a while, it is probably worth owning. My last can lasted at least a decade and was still usable when I finally was running out.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=4148