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matjay 01-30-2012 07:52 PM

Shark 24 Keel
 
Just got my first boat, an old shark 24! In addition to this being my first boat, its also my first restoration...Unfortunately the keel is in need of some TLC.

Essentially I have one week to get the bottom all squared up before she's water-bound again.

From the research I've done it seems to me the best approach is to sandblast the keel white, then immediately apply a base layer of epoxy. Any recommendations as to what to use for the base layer? Is something like WEST systems alright, or is a zinc enriched epoxy necessary?

Moving on to a filler, again is WEST ok? and how many coats is recommended?

Many people claim to use a notched squeegee or trowel to apply the epoxy, and then fill in between the created lines? is this necessary?

Any information would be greatly appreciated!

Faster 01-30-2012 07:59 PM

Blasting to white and immediately sealing with epoxy is the way to go, and should do fine. This time of year it'll be a challenge unless you're indoors.

Once sealed, you can use any filling/fairing compound that's epoxy compatible, but look for something easier to sand and fair. How badly pitted is the keel? How much filler thickness are you likely to need?

Great little starter boat, btw, it was our first too... (30 years ago next month!!)

SloopJonB 01-31-2012 02:25 AM

Quote:

Originally Posted by matjay (Post 824144)
From the research I've done it seems to me the best approach is to sandblast the keel white, then immediately apply a base layer of epoxy. Any recommendations as to what to use for the base layer? Is something like WEST systems alright, or is a zinc enriched epoxy necessary?

Sandblasting is correct - any grinding method will not clean ALL the pitted areas fully and future failures will start there. Just use regular epoxy resin as a seal coat - nothing fancy, just get it on right after blasting and a solvent wipe. You can't even leave this step overnight. West is only more expensive - 4 times as much as the industrial no-name resin I use. Stone fabricators - counter tops etc. use a lot of epoxy - check around and you'll save $hundreds.

Quote:

Moving on to a filler, again is WEST ok? and how many coats is recommended?
Again, West only costs more. Get a cement bag of industrial talc for about $20. It makes the most beautifully sanding filler you have ever experienced. Mix it to peanut butter consistency with epoxy and you probably won't even have any pinholes to fill after sanding.

Quote:

Many people claim to use a notched squeegee or trowel to apply the epoxy, and then fill in between the created lines? is this necessary?
This makes it MUCH easier to get an even coat. Unless you're an experienced plasterer, using a plain trowel will give you a very uneven thickness. You do NOT want to sand through to metal, ever, or you will have to start over there. You want a reasonably thick finished coat - 1/8" min. is my preference - in order to ensure the metal stays buried.

Get an autobody longboard sander - they look kind of like an old smoothing plane, about 18" long and take pre-cut strips of sandpaper. This will help you fair up your keel - mine ended up looking like it had been templated.

I finished mine off with 3 coats of epoxy resin and 3 coats of Interprotect (there was still discussion as to the best sealer at that time). Now I'd just use Interprotect for all coats.

matjay 01-31-2012 04:27 PM

thank you kindly for the info!

unfortunately I have yet to see the keel myself as the boat is still in the water. this is second hand info, although i have no reason to discredit it.

Will temperature really have that great an effect? And I've heard Talc has moisture retention properties, any truth to this?

After sandblasting is one priming coat of epoxy sufficient on the keel, and then i can move onto filling?

Quote:

I finished mine off with 3 coats of epoxy resin and 3 coats of Interprotect (there was still discussion as to the best sealer at that time). Now I'd just use Interprotect for all coats.
How much dry time is necessary between coats in your experience?

SloopJonB 01-31-2012 05:14 PM

Quote:

Originally Posted by matjay (Post 824645)
Will temperature really have that great an effect? And I've heard Talc has moisture retention properties, any truth to this?

Temperature spec's from the manufacturer should be followed - they vary. There are epoxies that are specially formulated for cold or damp or even underwater applications. They are generally VERY expensive though. I have found you're generally O/K down to about 50 with a fast hardener although it will slow down a bunch.

Talc does have moisture retention properties. This can be a very minor, occasional problem when using polyester body filler and especially with auto body primer over bare metal, if left unpainted - that's where the reputation came from. When mixed with epoxy I've never heard of it. I was given the process by an old time boatbuilder and boatyard owner - it's always worked superbly for me. Don't forget, worst possible case, even if it acted like a sponge, you'll still have the epoxy resin coating under it and several coats of barrier coat over it.

Quote:

After sandblasting is one priming coat of epoxy sufficient on the keel, and then i can move onto filling?
Yes, strictly speaking it's not a primer coat, it's a sealer coat - you get it on fast to seal the bright, unoxidized metal from the air to prevent any oxidation which would degrade the bond of the coatings.

Quote:

How much dry time is necessary between coats in your experience?
Until it's hard enough to not gum up sandpaper - varies depending on the catalyst, air temp etc. Sometimes the starting area is cured enough by the time you've finished the end. - It's very easy, you'll see. If you've ever patched or mudded drywall you'll have no problem - very similar process.


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