Keep it rough?

Thinking ahead.

Working on a stripper using hardwood and plan to finish bright. My woodworking background suggests the need to get the wood surface darn near perfect before glassing lest every scratch and swirl become forever illuminated with the application of epoxy. An article on this site advises sanding through 220 grit, and I might be tempted to go even further.

BUT. I just noticed an item on the Guillemot site that warned against sanding beyond 80 grit. It said too polished a surface might compromise the ability of the glass layer to make a good mechanical bond with the wood.

I don't think I'd worry about this I I wasn't using cherry, but well- I am. Any thoughts on this?



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RE: Keep it rough?

Epoxy will soak into and bond with smooth wood if the grain is still receptive.  "Polish"   is not necessarily 220 grit.  However if you sand with 220, 150, 100, 80 or any other  grit and don't change the worn out or clogged paper you will "burnish" and/or "burn-in" the wood and close the grain to epoxy saturation.

The "mechanical" bond is the epoxy soaking into the wood grain. If the glass fibers make a mechanical bond the wood must REALLY be rough. ... ;-)

RE: Keep it rough?

 Having worked with lots of Cherry over many years I would concur with Grumpy. It is a medium denstiy wood that accept most finishes and adhesives very well. I would not hesitate to sand to 220 for a finished surface but would not go beyond 100 for a bonding surface.  Use a good quality random orbiting sander and change paper often.

RE: Keep it rough? - a question


i wanted to ask a bit about doing a stripper in cherry?  are you doing the whole boat in that wood?

one of the advantages of a cedar strip built boat is its light weight......cherry is about 100 to 150% heavier than cedar.......could end up with quite a heavy/unweildy craft depending on the project.

typical strip built sea kayak using 1/4 inch cedar is around 40 lbs......if done all in cherry.....could get you 80 lbs plus.

anyway....just thought i would ask....i have cherry furniture.....but not sure other than accents...if it would have the other properties (weight, flexibility, resiliency to impact) you want in a boat.



RE: Keep it rough?


Yes, if I'm making a mechanical bond with the glass itself I'll definitely sand more!


I'm confusing what you are saying in addition to Grumpy's comment. I took his comment to mean "don't worry about sanding to 220, worry about burnishing the wood." In other words, if I'm scrupulous about changing paper I should still get a good bond even if I sand to 220. But you said you wouldn't go beyond 100 for a bonding surface. You seem to be in agreement with Grumpy so there must be something I'm not picking up on. Could you please clarify?


You're right to be sceptical of the cherry- it's admittedly a bit of a fools errand. But I'm using thinner strips, so while I'm sure it'll be heavier than it could be, I'm hoping it won't be too bad. This is a sentimental boat (Wood Duckling) for my kids to use in this too brief window of time before they outgrow it. Which could be any minute now, given my grocery bill. I milled the wood from trees taken from my grandmother's property- another layer of sentiment. If it sees one good summer, I'm happy. It's definitely an experiment, though given how fun it isn't to work with in this way I'm not sure I'll ever try it again.

Thanks, all.


RE: Keep it rough?

Hello Patrick,

Sorry for the confusion. . . Hope my answers below clear it up a bit. 

"In other words, if I'm scrupulous about changing paper I should still get a good bond even if I sand to 220." Correct - if you are applying to a finished surface for asthetics.

"But you said you wouldn't go beyond 100 for a bonding surface."  What I meant and should have been more clear is that if you are bonding two pieces of your cherry together I would not go beyond sanding with 100 to both bonding faces or edges.  

But you said you wouldn't go beyond 100 for a bonding surface.The picture below is a poor example but one I had handy showing a cedar planked hull . Hypothetically if these were Cherry and not Cedar, and had I bonded them together I would recommend not sanding the face grain of the bonded surfaces beyond 100. However, when the hull is constructed and expoxy finish is added you could sand to 220 on the finished surfaces before coating. Since Cherry is a medium density wood and will obsorb the epoxy well and have a bright finish after varnish. 



RE: Keep it rough?

Thanks for the clarification, RMB- that really puts my mind at ease. Having a (hobbyist) woodworking background definitely makes construction easier, but it also puts some interesting "what ifs" in my head that are way out of my realm of experience.

Thanks to this cold snap I hope to have time to finish stripping soon. When the heck do guys in the tropics have time to build new boats?!

Thanks again,


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