Can these puzzle joints be used?

[riverron]

I glued a set of side panels yesterday with thicken epoxy. While trying to put them together, they were very, very tight and did not want to seat right.
I got it the best I could and clamped/used weights. I sanded this morning and it looks like I have gone through the veneer in a couple of places trying to get smooth.
Will I be able to recover with these, or should I cut new and start over? You can definitely feel the low area and the only way I think you could repair would be with some type of fairing compound. One side is better than the other, so the better side could go on the outside and would be less noticeable.

Thoughts?

thanks
Ron

[craig]

You could use fairing compound to level everything off. Will this even be noticeable under fiberglass (both sides will be glassed)? Unless you are planning on a bright finish, there is no reason to re-cut these panels. Structurally it is fine.

- Craig

[craig]

I'm not able to comment on your blog because I don't have an account, but I wanted to say that you're probably sanding too much. You've said a few times that the random orbital will easily go through the epoxy. A huge revelation for me was realizing how much less sanding I needed to be doing. Yes, you want it to be smooth and a grey-ish color. But for those cleats or other small objects, or near ANY edge, a random orbital sander will eat through the epoxy instantly. Just make sure you coat it pretty smoothly to begin with and sand CAREFULLY by hand to rough-up the surface so it will accept paint. This is especially true on exterior surfaces that are varnished, such as the rub rails. It's easy to sand too far and then you'll get pealing varnish. You can see on my boat exactly where I went too far and were I didn't. As for sanding fiberglass: I ended up using 60 grit to get the worst stuff, then 120 across the whole thing. Again, you don't need to be absolutely 100% grey colored. There will be little shiny divots (extremely small ones) that seem to be fine, and indeed, you can see them in pictures of Pocketship #1. So don't sweat sanding literally everything and hurt yourself by sanding away all the fiberglass. Good luck!

Craig

[riverron]

You could use fairing compound to level everything off. Will this even be noticeable under fiberglass (both sides will be glassed)? Unless you are planning on a bright finish, there is no reason to re-cut these panels. Structurally it is fine.

- Craig

Both sides will definitely be glassed. I was more concerned with structure and noticing anything through the paint. After I posted this I did notice a couple of the blogs using fairing compound, so hopefully that will fix anything noticeable through the paint.

You are also right that I am sanding too much. I stated that in my blog. The part that gets me is "greyish color". You can get is smooth quickly, but getting the greyish color takes longer and that's where I get into trouble.

My new plan moving ahead is to give it a quick run over with 80 on the orbital sander and then switched to 120.
Any trouble areas I see, I am switching to the hand block and also using it around edges where I was running into issues.
I will also try not to worry about all the spots like you stated.

My problem with the puzzle joint was it did not want to go together good when glueing, therefore I had to sand to get it smooth. I did another one yesterday and sanded the little fingers slightly before and it turned out ok. I will do that on the remaining puzzle joints. Make sure they fit properly before putting the glue on them.

Thanks again for the advice! Always learning something new, which is fun!

[truenorth]

They'll be fine. You might want to lay them very flat and add some less thick epoxy - not fairing compound - to even it out. It won't be noticeable when you're done. How do I know? Because my puzzle joint connection skills were so bad I took the whole thing apart with a heat gun and redid it. The important thing is they need to be flat. So if you find yourself sanding down a big part of the finger to make it flush, that's OK. That means you'll probably have to add some filler to the reverse side. I think I actually left the outside part of the topsides completely unsanded with gobs of epoxy until just before I was putting the cockpit together.

Here's an example of the before and after (and by after, I mean after adding a small bit of runny epoxy to fill the gaps):

[John in CC]

I found that even when the joints are lined up really well that they don't curve with the same exact radius as the surrounding plywood. Mine had a very slight dip. I used a little fairing compound before the fiberglass. It probably didn't really make any difference because the dip was so small and would have been accounted for with the thickness and irregularity of the epoxy and fiberglass when it was applied and sanded out with a long sanding block. I found that micro balloons mixed with epoxy made a strong fairing compound, better than the green stuff. It worked well at the fiberglass layer seams that can be seen in the lower picture.

I'd suggest putting primer on the entire bottom (or any other area) and sand it off using a long block. The high and low spots will become very evident, then treat them accordingly.

[riverron]

Thanks everyone for all the different options. I inspected the one side panel again today and it really only has some minor dips. I think I will be able to resolve them with the fairing compound. The other side panel went together fine. I even started to fiberglass it tonight. Looks pretty good.

I am starting to learn that all my issues are not disasters and sometimes have many solutions to resolve.

thanks
Ron

[mark48]

Hi all,

I see many comments suggesting the use of "fairing compound" to fill depressions remaining around the puzzle joints after sanding. I also note that others have used these substances to assist in developing a "fair" curve on the surface of the hull. We're all aware that the finger joints are structurally important to hull integrity and that filling depressions resulting from miss-aligned puzzle joints and subsequent sanding is not simply a matter of developing a "fair" curve. When I had the same issue with finger joints following gluing and sanding, I was instructed by CLC to fill any depressions with thickened epoxy using colloidal silica for supreme strength, and then to sand smooth taking care not to remove more plywood.

Just a thought - some "fairing compounds" might not be as strong as you'd desire.

All the best,
Mark

[riverron]

Thanks for the insight Mark. I think Truenorth was saying the same thing. I wound up calling CLCBoats yesterday and telling them my situation. I my case they said I should be good. I say my case, since everyone's solution could be different and there is no one fix.

Thanks again for all the suggestions! That's what I like about this forum!