You don't want to hear this, but you're going to have to sand. Epoxy bonds to paint just fine. It's the paint to wood bond that's the problem. Paint is not meant to be glue. It'll get pulled right off the wood.

You need to make up your mind to either properly prepare the surface or to do without inwales. Attaching them without the cleanup will lead to them breaking off.

Sorry,

Laszlo

First of all, let me commend you on your choice for inwales.  I think after you're done, you'll be very happy with your decision.

Yes, I would try to mask off the paint below where the inwales will be attached.  Then I would carefully sand down to the epoxy layer.  This will provide the strongest bond possibly.  You'll want to do it right.  You'll also want similar masking in place when you epoxy the new parts in place.

Thanks for the responses.  I was afraid this might be the recommendation.  

So, I’m thinking I remove (sand?, plane?, scrape?) a band of the Brightsides paint all around the interior of the boat down to the epoxy layer - or to bare wood.  Then, I put on a coat or three of epoxy on the newly exposed band, and set about installing the spacer blocks.  Following that, I assume I would need to carefully repaint (three coats!) with Brightsides in between each spacer block up to the gunwhales.  In addition to sounding like what CLC would call a “goat rodeo” of a job, I’m wondering if the new paint would blend well into the existing interior paint that was rolled on and tipped?  Thoughts?  Is there a better way to go about this?  Would it be nuts to mask off the gunwhale where each spacer block will be affixed and rolling on the three coats of Brightsides?  I’d like to do this as efficiently as possible, but I’m mostly concerned with having it look right when I’m finished... Ugh.  As a new builder, I was aleady a bit intimidated by the inhale project...😕

Down to the epoxy is fine.

Yes, it'll be next to impossible to get a perfect match on the paint. So don't even try. Apply a slightly different, non-clashing color. Since it will be consistent everywhere under the inwales, it will show that you meant it to be that way. It can be as simple as mixing a little black with your current color to darken it up some.

Good luck,

Laszlo

   Variation on the question.  I am early in the process; still bare wood inside the hull.  I plan to do inwhales.

1] Would it be better to fix the spacers to the bare wood or to first coat the hull interior with unthickened epx, let it cure, then put on the spacers?

2] Whether attaching to bare wood or to epoxied wood, must the glue be epoxy plus Cellofill, or would unthickened epx work just as well to glue on the spacers?

Thanks

1. Paint it with some unthickened epoxy first so that the joint won't be epoxy-starved. Don't wait for it to cure. It's actually better if it doesn't cure beyond the tacky stage before you start gluing.

2. Any structural thickener will do - wood flour (my favorite), Cel-o-fill, etc - but you need to thicken the epoxy so it won't run out of the joint.

Have fun,

Laszlo

 For Wood,

     I fundamentally agree with Master Laszlo but have a suggestion that will save a bit of work.  It is important to keep in mind that the entire inwale structure will have to be coated with epoxy and sanded ready for varnish.  If you wait until after everything is glued together, it will be slow tedious work getting to the area between the hull and inwale.  What I did, was first coat and sand the entire interior of the hull prior to gluing on the spacer blocks.  After the blocks were glued on, I removed the clamps and coated/sanded the bottom, front and back of all the spacer blocks.  Before installing the inwale, I coated it's back side and sanded it ready for varnish.  Following this sequence eliminates having to try to coat/sand the small interior spaces between the inwale and hull.  Of course, you will have to get in there with a varnish brush.  As another tip, I used Epifanes Rapid Clear Varnish which does not have to be sanded between coats.

Gentlemen,

Thank you for the very useful tips.

I spelled inwale wrong.