Smoothing the hull for paint

I'm in the process of filling the weave of the fiberglass on my first kayak and was wondering if there are any tricks (other than sanding) to getting a fine finish for applying paint.  I build ship and boat models and have used high build primer for this purpose.  I've read that the talc in the high build primer causes problems with hulls that can get wet.  Any recommendations for a primer or other material that works well?

Also, can you use automotive putty (or other fast dry easy sand substace) for filling defects under paint or does it have to be thickened epoxy?


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RE: Smoothing the hull for paint achieve nice finish, consider sanding your hull by hand.  It does add a few hours to the job but you won't get the swirl marks common with ROS.  Once you're satisfied with the sanding, apply a coat of Interlux Pre-Kote primer then resand according to the directions.  The Pre-Kote will hide those small imperfections.  If you are using Interlux paint, make sure you follow the thinning directions.  I would thin all coats to achieve a super glossy finish.  Apply the paint with a yellow foam epoxy roller and tip with a good quality foam brush.  Sand between coats as per Interlux directions.  I've only painted with white (except for trim) so others may have suggestions for darker colours.

Good luck


RE: Smoothing the hull for paint

Hi Scott, have you checked out CLC's shop tips regarding finish?  For example:

I have used high-build primer over epoxy and under marine polyurethane topcoat, without issue.  I have also used some of the West System lightweight fillers (with System Three epoxy) for easy sanding imperfection filling.  The key is to experiment and practice on scrap pieces before committing an untried combination to your hull. 

RE: Smoothing the hull for paint

Thanks Chris and Ron for your comments!  I think the CLC shop tips is where I read about the high build primer issue.  Chris, what a great finish!


RE: Smoothing the hull for paint

I've also used Pre-Kote followed by interlux brightsides with no issues...but one of my friends did have an issue.... (the topcoat of brightsides bubbled up, and he had a real mess)... it turns out that the problem was that he had applied the primer in damp weather -- (we both live in the Pacific Northwest-- damp weather is our middle name)-- and by the time he got around to applying the topcoat the talc in the primer had absorbed moisture. So -- I think the caution here is to be aware of the ambient moisture levels (humidity, rain), and be prompt in sanding and painting!

Julie K.


RE: Smoothing the hull for paint

I've found that fill(er) is not needed to achieve a smooth, hard base to apply paint.  There should be enough resin that came with your kit (if you purchased a kit) to apply about four coats of resin over the glass, sanding lightly to smooth it out, between coats.  Be careful not to sand into the glass cloth.  At about the fourth coat of resin you should see a real smooth surface after the final sanding.  Then go ahead and paint or varnish.  I'm afraid of fillers for reasons mentioned above and because I don't think any of them are nearly as hard as cured resin.  Little dings become problem dents in many filled surfaces.  Also, resin will not shrink over time and cause crazing in your painted surface.  Good luck. 

RE: Smoothing the hull for paint

Another thought on filler vs resin.  You, or whoever you bequeath or sell the boat to, might someday wish to remove all that paint and re-expose the beautiful wood hull to be admired by all who pass.  I'll bet you, or they, would rather run into clear resin rather than hard to remove filler once the paint is gone. 

RE: Smoothing the hull for paint


Filling the weave, fairing and preparing for paint are actually 3 different steps. You can use a slurry of phenolic microballoons and epoxy to initially fill the weave. Next, a thicker mixture of the same to fair the hull. Finally, the high build primers to prepare a smooth surface for the paint.

The ballloon mixes have high compressive strengths, so they're every bit as tough as epoxy when it comes to dings. They're less resistant to abrasion, so they're easier to sand. With the balloons' hollow cores, they're lighter. So you end up with a cheaper, lighter and easier-to-sand surface. It ends up chemically inert, impervious to humidity and dimensionally stable. About the only downside is that ugly purple color, but if you're painting anyway, no one will ever see it (unless Jerry's scenario comes true).

Depending on which paint system you use, you can either go from the faired, sanded microballoon surface directly to the primer, or you may need to put on a final thin coat of unthickened epoxy and sand again.



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