Sanding question

 I am working on my Shearwater Hybrid Sport and am currently at the stage where you sand the whole bottom of the kayak down after the 3 coats of epoxy. I have some air bubbles (sun exposure on one small section due to tent position) which I am ok with. After doing a 220 sand I now notice these little spots near the air bubbles. Anyone know what they are and if or how I get rid of them? They are about the size of a finish nail head. Here is a link to pictures... Kayak bottom

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RE: Sanding question

Hi Tempest170, 

i looked at your pictures and these imperfections are little air bubbles that got locked into your epoxy when you glassed and fill-coated the bottom.  this is pretty common on the first couple boats somebody takes some time to really develop the skill for a zero-bubble layup.

when you sand the epoxy to smooth it, these little bubbles get partially opened up and then the sanding dust collects inside them giving them a white appearance and what was once a "clear, hard-to-notice bubble" is now a white dot.

you can try to get rid of them by opening them up with a sharp nail head and then flushing the dust out with fresh water or denatured alcohol.  then after that, another skim coat of epoxy can fill them.

this can get rid of the most egregious of them...but they may be some minor imperfections remaining...and that's ok....these are not large according to your description.   

usually after sanding the three fill coats, you will do some of this bubble opening/cleaning work and then do a final pass of epoxy with a spreader to address these little imperfections to your satisfaction.  otherwise, this looks pretty good.

hope this helped.



RE: Sanding question

   Thanks H. This is definitely my first build and first time working with epoxy so all new experiences. I will do exactly as you mentioned. Followup question, after I do the skim coat of epoxy do I need to sand down again? I wasn't sure if the sanding was to remove imperfections or if it is needed to provide a bond for the varnish stage.

RE: Sanding question

you will do a final sand after the final skim coat (180 - to 220 grit is fine...whatever you have available).....but it should be relatively easy and light vs agressive sanding.  this will ensure that you have a good bond available for the varnish as well as provide that final smooth hull due to any minor imperfections introduced by a not totally perfectly applied skim coat. 

at some point the music stops...but it always ends with a sanded finish:)


RE: Sanding question

   Thanks for your guidance and prompt reply. Air bubbles are a pain but I'm sure everyone has their fair share to contend with.

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