Sandable primer for below water line

[Bob Perkins]

Hi Everyone,

I'm probably over thinking this problem...

I'm currently sanding out the bottom of my boat (epoxy coated..).

What I'd like to do is put down a sandable primer, long board it - fill the low spots - final fair it - then finish with bottom paint before flipping the hull.

Can someone recommend a primer that will be ok below the waterline?

I called Interlux - they recommended Interprotect 2000. I've used it before and it really is not a sandable primer.

Any suggestions?

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Regards,
Bob Perkins

My out of date site is at:
http://robert.perkins.home.comcast.net/

My Current project is at:
http://www.imagestation.com/album/?id=4291051329
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[Buddy]

Interlux 400/414 is what I use. It is sandable, but not really quite a high build product. For that, I believe Pettit makes two epoxy products- one hard and one high build sandable. The mid range Interlux 400/414 is what I like.

[imported_Dutch]

why do you say the interprotect is not sandable? ive sanded it plenty of times

[warthog5]

Awlgrip 545.

[Bob Perkins]

Dutch,

Well - I suppose interprotect is sandable - but if I remember correctly - it goes from a gummy sandable to a hard as a rock sandable.

A *standard* sandable primer is a bit easier to work with. I'm thinking back to auto body shop in school ... you sprayed down - long boarded to show the low spots - filled - repeat. Until you got the surface you wanted.

I'll look at the others that were suggested - thanks!

[bottompaint]

Go with the 2000. It sands smooth. It smooths to the same degree with 220 grit as with 320 grit. Seriously, you can paint over the 220 sanded 2000 and it will look like you've painted over gelcoat. Not only that, but you can use 3M premium filler on it and overcoat the 3M with 2000. The interlux labeled "Barrier Coat" product is NOT of the same quality....and I have had the experience of it peeling after 5 years.....small areas that flaked ect.

[Bob Perkins]

hmmm.. You guys are convincing me to give it a shot... smile.gif

[imported_Dutch]

make sure you mix the correct ratio- 3 to 1 I think- get some reliable measureing devices, and the proper induction time is very important to begin the cross linking properly. and dont wait a week to sand it

[JimConlin]

Bob-
I've been using a fair amount of Interlux 404/414. It's fairly sandable, but having a lot of solvent, it's certainly not 'high-build'. At least it provides a uniform color so you can see the surface better.
I mostly mix a quart at a time, 'cause i'm not confident that i'd achieve any precision in a partial quart batch. Both components are very viscous.

A mixed batch will keep for a day or two in the fridge. Cover with foil. Polyethylene won't trap the (nasty) vapors.

I've been considering a few experiments with this stuff:

Can I bulk it up with microspheres and get something that builds a little better, or would backing off on the solvent do it?

I've been told that the solvent(Interlux 2333N) is compounded to be slow to evaporate. It also smells awful and costs five times the cost of acetone or... Seems to me taht the argument against thinned epoxy (think sponge) is the same regardless of the solvent used. One of these days i'll try something else and see what happens.

Unless you go first.
(Thanks again for the help in June)
Jim

[ 10-09-2004, 10:41 PM: Message edited by: JimConlin ]

[Bill Perkins]

Ruell Parker writes of adding talc to a 2 part paint ,making his own hi build primer .Has anyone tried that ? I've put a bit over a gallon of the 400/414 on my boat and had no problem with batches as small as 8 oz.( plus 2 oz. brushing thinner ) . Seemed just like the bigger batches I made .

I put on 2 coats a day of the fast drying paint.I was heading out of town , and wanted to finish ,hoping for a chemical bond between coats . It's hardened up well , but six months later I sanded some off and could still smell the thinner . Maybe I entrapped a small but not catastrophic amount ? Has anyone else sanded the paint months after application and whiffed the solvent ? I guess I should back off to 20% thinner when my shop's cool, and/or give it 24 hours to dry .

[ 10-10-2004, 12:35 PM: Message edited by: Bill Perkins ]

[imported_Dutch]

i think id stick with manufacturers recommendations

[JimConlin]

Yes, the thinner is there many months later.

[Wild Wassa]

Originally posted by Bob Perkins:
"What I'd like to do is put down a sandable primer, long board it - fill the low spots - final fair it - then finish with bottom paint before flipping the hull."

You have already put a sandable primer on the hull ... epoxy. Primer means 'first'.

Warren.

[ 10-10-2004, 09:54 PM: Message edited by: Wild Wassa ]

[Bob Perkins]

Hey Jim,

You have the right idea - I want to use the primer not necessarily for high build (although that would be helpfull) I just need it for contrast so when I long board the bottom and final fair - I can identify the low spots.

It sounds like the 2000 and the 400/414 are the two top choices - BoatUS had the 2000, so I think I'll give it a try this week..

I thought I had used the Interlux 2000 on my sailboat - but I may have used the barriercoat stuff - which was a real pain to work with - I'm hoping this is better. (Thanks Bottompaint)

Thanks for all the help everyone - You are a great information resource!

Regards,
Bob

[Bob Perkins]

Mike,

Thanks for the suggestion - The current bottom coating is a very fair surface. I have already sanded/faired as much as I can at this point with a 6" ROS. There are minor low spots around that I would like to eliminate.

I have not sanded through the glass anywhere (but have gotten close here and there).

I do have big drywall tools to use - I'll give it a shot this week and see how it goes.

Sounds like a good plan.

Thanks,
Bob

ps. I freely admit I'm overdoing it - it is sort of a practice session too. Part of the process for me is learning a new skill and how to make a really smooth surface. The pro's do it all the time to keels and molds for glass boats where there are increadibly fair.. Even faired planked hulls get real smooth. Playing around with the bottom is advantagous because in the end - it won't matter if it is a little off and it will be under water.

I vacuum bagged not because I had to - but because I wanted to learn how to do it... Same sorta thing. smile.gif

[Stiletto]

When fairing curved surfaces on a hull repair on my boat, I found an old straight backed saw blade useful to conform to the curves . It may be helpful in your case.

[JimConlin]

I'll sometimes use a notched trowel to lay on some noodles and longboard the noodles to a fair surface before filling the furrows. The noodles sand very quickly.