You’ve sanded thru the outer veneer layer, right? You haven’t gotten to the step where you’ll be adding a layer of fiberglass & epoxy?

If your plan had been to finish ‘bright’ there’s nothing you can do to remediate that skinned veneer. If painting is your plan you can fair out the void with epoxy & microbaloons paste, return surface to level of that of surrounding panel & get on with it.

Was there something causing that sanded-into panel to bulge a bit or twist? It’s easy enough to sand thru veneer that’s flat should one be distracted by something whilst sanding; a deformed panel gone unnoticed will announce itself PDQ once sanding begins, whether by hand or power-assisted.

Even for the skilled among us, it’s probably a good idea to leave sanding bare plywood to hand sanding. It’s just too fast & easy to go too far with power assist when veneer is on the order of 1mm / 0.040” thick or less. 

spclark asks a good question.

i would frame it a bit more simply as:  do you have a low spot you need to correct now or did you simply sand through the veneer? 

in a past stitch and glue, for example,  i didn't really have a low spot...but i did go through the veneer.  as soon as i noticed that i stopped and just completed the boat.  i have also had a project where i got startled while working with a sander and created a pretty clear divot in the hull that needed to be dealt with.

most of how you will address this depends on the 'look' you are going for and where the problem is.  so if its a bright finish you want, it's a bit more challenging and if you were going to paint the boat, there are a lot more simple options.  

tell us more or post some pictures and will try to make a recomendation as appropriate.

h

I agree that you should post some pictures to get good advice.

I've sanded through the first layer of veneer in a small area and have still been happy with a bright finish. (And the patterns of wood are such that no one ever seems to notice such small flaws.)

On my Sectional Shearwater Sport my hand saw wandered a bit while I was cutting it apart. I had to build up an area along the hull division several inches long and up to about 1/4" thick with wood/epoxy putty to put things right. And even so the bright finish came out well enough that no one notices the flaw.

John Harris has done some creative painting on occasion to conceal repairs of one sort or another. Most of a boat can be bright with interesting painted stripes or patterns that actually enhance the beauty of a boat.

I wouldn't give up on the bright finish too early if that's what you prefer. You can always paint parts (or all) of the boat later.

Well, the spot is on the bottom, right?  If you mean to varnish the whole business, bottom and all, maybe you could paint over the affected spot, and a matching spot on the opposite side, a little sigh reading: "Other Side Up", you think?  <;-)

.....Michael

Thanks for the comments.  I  love the “Other Side Up” idea!  :-)

I do indeed intend to varnish.  I haven’t changed my mind about that.  It is on the bottommost panel, so it won’t be very visible.

Pictures attached.

https://share.icloud.com/photos/0XZ9euSl91N3dxs8G7rAwpp7A#Home

https://share.icloud.com/photos/09wn-JKW3_-M0M3O14pQg-q4A#Home

Apply a graphite/epoxy bottom and no one will know what happened. It'll look as if you meant to do that all the way along AND will resist scratches better than varnish.

Have fun,

Laszlo

imho, 

if your objective is a bright finish and the pictures are what they are and are on the bottom panels, i would just continue on and try to be careful to avoid anymore 'sand throughs'.

i am in birch's camp (from experience) that you can have small sand- throughs and still complete a very successful varnished boat.  given that these are also on the bottom, you are just fine.   what i mean by very successful, is that nobody is going to notice and even you will likely forget these little imperfections over time.

at this phase is the construction, assuming you are staying with varnish,  there is nothing you can do to resolve a sand through absent cutting out a panel (or a section of panel) and grafting a new okoume panel in its place.  based on your pictures, i just wouldn't go there.  as i said above, in my opinion, this is very minor and and  i think you are doing fine.

to the extent that you want to try something other than varnish, that work doesn't happen until after your glassing work.  if you want to paint or  put on a graphite/epoxy bottom, that happens later.  so you are not losing anything by continuing.

h

   Here is one thing you could try: take some of those surplus scraps of plywood and intentionally create some sand-through areas similar to the one on your hull. Now mix up some tiny batches of wood flour / epoxy paste of various consistencies and thinly "paint" your test patches. You may find that you can conceal the flaw. Or not.

It's part of the learning curve and an honest mistake. Embrace it, look on it with fondness and move on...

   And if it's a small and shallow oops, you could take a scrap of plywood with similar grain, trim off the ~2mm veneer layer with a table saw, and glue the veneer side down onto the defect. Then, sand and scrape really really carefully until it's flush. 

   My rule is to do no additional harm. Form and function beats looks, especially hidden looks.  It would be better for a smooth low drag hull than a pretty one.  I build it to paddle it not look at it.

 A year or two of frequent use it will blend in with the other scars and refinish marks.

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If you want a preview it wet it with some denatured alcohol.