Hobie Cat Forums

I'm thinking about a bottom job on my H16 this fall. I've seen a great deal of debate about resin type for repairs here.

It looks to me like the West System products are ideal for the DIY guy, but I've seen several post recommending polyester resin instead of epoxy. So my question to those of you that have done this...

What product works the best? Epoxy or Polyester? What brand(s)? Did you use fillers or just glass cloth?

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Garrett

94' H16 - 100403

Polyester, that's what the boat is made off.

Epoxy stick to polyester, but gelcoat (polyester) gets an amine blush when put on epoxy.

So best stick with what the boat is made of.

I did use filler on mine, I put West 404 in the polyester resin to make a putty. Then put gelcoat on top of the finished repair.

There is a Hotline article about bottom repair, but don't remember which edition. It's a good read.

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

Ummm . . . no.

Epoxy will develop an amine blush on the surface when it cures - how much depends on temperature and humidity (more humid = more blush).

The epoxy's amine blush must be removed (soap & water, light sanding) before coating with any polyester product, like gel coat.

Epoxy develops a much stronger chemical bond than polyester; it will stick to almost anything without much surface profile (roughness).

Polyester resin needs a rough surface (80 grit) to develop a good, strong bond.

For bottom jobs, polyester (or vinylester) resin is the material of choice. Epoxy does not have good UV resistance and will yellow badly when exposed to the sun.

You will need...

Polyester resin with MEKP hardener
1" to 2" wide fiberglass tape
Formula 27 filler
Glass microballoons (thickener)
Gelcoat if you want it to look nice.
Various grades of sand paper (80 grit to 1000 grit wet/dry) and a sanding block.
1" wide disposable brushes or rollers
Plastic spreader
Quality scissors
Acetone
Mixing cups and sticks
Latex gloves
Masking tape
Paper towels

All of these supplies can be purchased through uscomposites.com, fiberglasssupply.com, jamestowndistributors.com, West Marine, and/or your local hardware store.

I would not use epoxy for the reasons previously listed and also because its more expensive than polyester and really unnecessary for a bottom job.

sm

I guess I got that wrong. So if I understand correctly, if you don't remove the amine blush, the gelcoat won't adhere properly. Correct?

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

Correct.

Great info!

One more question. My boat has some white mystery filler on the bottom. I have no idea what it is, but it's been used to build up the bottom as some point. If that was epoxy resin will it interfere with the polyester resin?

Do I need to be concerned with this stuff or just sand and cover?

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Garrett

94' H16 - 100403

You're probably OK - just make sure you scuff it well with 80 grit before applying polyester.

I have a 16 that i also need to do a bottom job on and have done lots of research on repairs. I realize that the pontoons where originally made from polyester and have researched amine blush. epoxy has a much stronger chemical chain than polyester and realize that it is more expensive, but feel that it would make for a far stronger repair in the end. I plan on re gel coating the whole lower area and don't mind the sanding and cleaning of the epoxy before gel coating.

Am i wrong in my thinking of a stronger repair with epoxy? I would love to hear feedback from any one that has done an epoxy repair and their outcome

Thanks

I used both, and found little difference in wearability on the beach. Use poly if you want to gelcoat over-just a little easier.

I liked using PVA sprayed over the gelcoat instead of surfacing wax, but you have to do it at just the right stage to get the best results. I had a shop with a good air conditioning system that I could quickly cool the building down to 65 for layup and shoot, and then turn it up higher for cure. I've found doing fiberglass work to be a pain without the benefit of the HVAC. For first time, I'd say use the surfacing wax. It won't buff out quick as easily or as glossy as using PVA, but you don't have to baby sit the kick.

This might be helpful:
http://bertram31.com/proj/tips/re-gelcoating.htm

Keep things simple- use polyester. The strength of the bond is largely dependent on surface prep. Be meticulous about sanding and cleaning the repair surface and you will be fine. The keels of the hulls do not see a lot of load, just a lot of wear, so using the highest strengh materials is overkill and a waste of money. If you plan to usr gelcoat then that's yet another reason to use polyester.

sm

Bottom successfully completed. Not as hard as I imagined.

My Rookie advice...
Mix up a few samples of resin and make sure you get it right before you begin. If your boat is in the sun it will get hard faster than you think. My first try i used too much hardener and the resin set before I fully saturated the glass strips. After two hours of sanding out the air pockets I created, I got to start all over again.

Now on to Gel-coat!

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Garrett

94' H16 - 100403

Good job on completing your repair. For future posters looking for information on this topic, I offer this bit of advice.




I would STRONGLY suggest that you grind all of it out. If it's marinetex, it has the potential to cause you a ton of heartache when you apply a layer of gel.

Formula 27 is a good polyester filler that won't react badly to other polyester products (gelcoat).

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Sail Revolution
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Yep, I wasn't too sure what it was so I got rid of about 90% of it. The remaining bits were covered up by the resin and glass. The little left behind didn't appear to cause any problems. Nothing was exposed when the Gelcoat went on.

I sprayed the Gelcoat yesterday but haven't had a chance to finish sanding it. How do you make the it glossy? 600 grit paper leaves it kind of dull.

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Garrett

94' H16 - 100403

Go to an auto parts store and get at least 800 grit. I got 1000 grit and it really speeds the final polish.

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Eric Weller
2006 F18 Capricorn
1980 H16
Keep the pointy side up!