Bad tip for faster bottom jobs

Actually, Bondo is what I used because I had some around. It seems to have worked fine. However Formula 27 would have been the better filler to use. If I do the job again, I'll use Formula 27.

The basic order of operations was 1) rough sand, 2) apply glass to build up surface 3) rough sand to fair in edges only and lightly scuff the surface of the glass 4) apply filler to fill in the glass weave and eges 5) fair in filler smooth 6) apply gelcoat 7) sand up to 600 grit wet & dry.

Be sure to wipe with acetone prior to applying the glass, filler, or gelcoat. And don't touch the surfaces with your bare hands after you've done the acetone wipe.

sm

Thanks. I've got bondo already so I'll use it. Do you use waxed or unwaxed gel coat? What the difference btw

See where you used waxed gel coat after looking back. Still don't know the difference though

Wax gelcoat is used for the final coat. If you do multiple coats, you need to sand and wash with acetone between coats.

Waxless remains tacky and subsequent coats can be applied on top without prep work. That last coat will need to contain wax or a curing agent(I forget the name) in order to cure hard and dry.

_________________
Marc...
1978 Hobie 16 Keoke, sail# 36 84

I don't know how well Bondo stick to fiberglass resin and how well gelcoat stick to Bondo. Might want to research that.

_________________
Marc...
1978 Hobie 16 Keoke, sail# 36 84

The bondo has held up fine thus far (about 4 months on the beach). No issues with bonding to fiberglass or gelcoat. As I said, if I were to do this job again, I'd use Formula 27, but the bondo seems to have worked fine.

It doesn't really make a difference whether you use waxed or unwaxed gelcoat as long as you understand that with waxed gelcoat, you need to sand between coats. With unwaxed gelcoat, you need to add the surfacing agent (liquid wax) prior to doing any sanding. The sufacing agent is added similarly to the MEKP (catylest) - you measure out the amount you need and just mix it in to the resin.

sm

After 6 years, I have some conclusions to draw on my study. It works well enough for bottom jobs.

Background:
6 years ago I did a bottom job on my H16. Rather than mixing up multiple small batches of polyester resin, I mixed up a single large batch of cold (40F) resin in an ice bath. I then applied some of the resin and some glass to the hulls, and warmed it back up using a heat gun. At 70-80F surface temps (air temp was a bit lower, hence the heat gun) the resin set up in 20-30 min. The resin in the pot was still ice cold, and therefore uncured, so I scooped out some more and kept going on the repair.

Results:
Since then I have sailed the boat hard, occasionally into things, and the repair has held up well. As such, I am going to call this one a success. So, yes you can mix up only one pot of resin to apply multiple cured layers.


Word of caution: humidity is a (censored), don't get your resin so cold that water is condensing into the mixing bowl.

This concludes my 6 year study on being lazy with polyester resin. Happy Sailing.
~Joe