How Much Do I Need to Sand?

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Ibrew2be
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How Much Do I Need to Sand?

Post by Ibrew2be » Fri Jun 06, 2014 2:25 pm

I am doing the planking of my boat in Okoume plywood. My plan is to finish the exterior with stain above the water line. I haven't exactly decided on the stain color, but it will likely be in the mahogany family.

When I fabricated the butt joint on the side planking, there was inevitably some squeeze out of epoxy past the area of the joint itself. I have sanded the excess cured material off, but am left with the wood having darkened where exposed to epoxy. My question is this: how much of this darkening of wood do I need to sand away? Do I need to remove every last vestige of it? Or will it suffice to sanded to the point where the epoxy mark is fairly faint but still noticeable? The image below gives you an idea of how things currently look.

Would appreciate any perspective others have to offer.

Barry
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41 Starboard but joint.JPG
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billy c
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Re: How Much Do I Need to Sand?

Post by billy c » Fri Jun 06, 2014 3:38 pm

wetting it out with water or denatured alcohol will reveal the color of the surface as if it had a finish on it. usually the plywood face is pretty thin so be real careful in the removal of the epoxy. i would use a cabinet scraper instead of sandpaper as it will give you more control and less chance of going thru.
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Andy Garrett
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Re: How Much Do I Need to Sand?

Post by Andy Garrett » Sat Jun 07, 2014 7:12 pm

The basic rule of sanding anything is: When you think you're done, you're not.

That said, plywood is a different animal especially if you want a bright finish. Go easy and use fine grits only.
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Re: How Much Do I Need to Sand?

Post by Andy Garrett » Sat Jun 07, 2014 7:14 pm

To better answer your question about the dark spots:

Don't worry about it. When you encapsulate with or without glassing it, all of the wood will darken to match those 'pre-encaspulated' areas.
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Ibrew2be
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Re: How Much Do I Need to Sand?

Post by Ibrew2be » Sun Jun 08, 2014 11:48 am

Billy and Andy, thanks for the perspective. Very helpful.

Barry
Barry Shantz

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BruceDow
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Re: How Much Do I Need to Sand?

Post by BruceDow » Sun Jun 08, 2014 6:13 pm

As Andy says... if you encapsulate right over the epoxy, it will all blend in. But if you want to stain, you probably need to get all that surface epoxy off so that the stain can absorb evenly.

One thing that you can always do when you are wondering how finishes will react is to create a small "test piece" off the boat.

Butt a couple of pieces of plywood, and let some epoxy seep through just like in your picture.

Then, test with your next step to see what you get.


I am on the record as wishing I never used stain. Other than problems with it absorbing evenly, I had problems where I sanded through it, leaving light spots that needed to be touched up. Those are very difficult to get right. If the wood and epoxy were natural colour, more epoxy would have been an invisible repair.
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Ibrew2be
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Re: How Much Do I Need to Sand?

Post by Ibrew2be » Mon Jun 09, 2014 6:38 pm

Bruce, thanks for the suggestion. I like the idea of doing an actual test first to see just how much of the residual epoxy mark I need to remove in order for it not to show through the stain. That's what I will do.

Barry
Barry Shantz

Imp built and launched. Thinking hard about Boat 2.0

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