Sides out of alignment

[Maniscalco]

I'm a new member and this is my first post so please forgive my naivete. If this is already covered, please point me to the post(s).

I've built five or six ukuleles from scratch with good to better than average results and am graduating to a Martin OM copy. Sides are bent and contoured correctly and the back was braced to 15 degrees and the match up of the sides and back went pretty smooth. Everything measured out correctly. But...I'm having issues.

As I was gluing the back to the sides. I noticed that the neck block (where it is glued to the back) was at an angle and not resting on the back except at the rim. So, at the rim, it was spot on but moving away from the rim an increasing gap grew to about 3mm. When I joined the sides, I cut off the extra material (there was a lot of it) on the neck block and I cut it square. I think this must have been a error. Should the block have been cut at an angle to accommodate back?

Next issue - which is probably connected to the first. Now that the back is glued to the sides, the upper bout is about a half inch wider at the top when measured against the back (I've only glued the back on at this point.) I can pull it together some but not the entire half inch. You should know that I'm using a legitimate Martin OM form in this process but could not use it in gluing the back to the sides because of limited use of my right arm at the moment - as I am recovering from shoulder surgery.

My concern is that by pulling the neck block back towards the body I have effectively caused the upper bout to spread - which will also lead to a myriad of other issues if not corrected. Fortunately I used hide glue so I can take it apart. Any sage advice you guys have would be greatly appreciated before I get too far.

Thanks for listening!

[H165]

Should the block have been cut at an angle to accommodate back?

Yes. The correct angle runs through a straight line from side-edge to side-edge when a straight-edge is laid across the upper bout side edges. You are seeing the gap created by cutting the block at about 90 degrees.

There are a few problems I understand, but I'll comment on something else altogether: Most amateur builds are assembled top-down.

It is easier to get all the odd back profiles and angles correctly assembled when you first create the box structure with everything at about 90 degrees. Depending on your decisions about top radii, this angle varies a tiny bit, but it does not require dealing with all the compound curves on the back, and the side profiles, before the sides are rigidly held by the much simpler top-to-side joint.

[Maniscalco]

Thank you for the answer and advice. Both make a lot of sense in retrospect. Fortunately I have an extra neck block to work with. I think relieving the hard 90 degree angle on the neck block will also allow the top corners of the upper bout to relax to a more uniform layout.

I truly appreciate the help!

[phavriluk]

This is an occasion where too many cooks can be in the kitchen, a tower of Babel possibility. So I'm not going to offer any specific comments about what OP ought to do next.

BUT...sounds like OP was building his guitar body without the help of some kind of mold, an invitation to chaos.

Very little of building ukuleles migrates successfully to guitar construction. I encourage OP to get hold of a book on guitar building and read it eight or ten times. We all did that.

Seldom is it possible to execute step B unless step A was executed well, there's no compensation. Starting over might be the wisest thing to do.

Last week a friend of mine observed he knew trouble was coming when he saw me building a guitar with a dial caliper. Precision and wood don't easily work together in the same sentence.

[redir]

I'm guessing that the first thing you did was build a hoop? That is to say that you bent the sides and then glued on the head and tail block? If so then that method as mentioned above almost certainly requires using a mold. It is definitely not required to use a mold to build a guitar though and in fact one of the most popular books on building, Cumpiano and Natelson's, builds top down on an open work board.

If you have already glued the back on then you may be able to create a wedge and force it in there where the neck block 'airspace' is. But if you think that the rest of the problems you have will drive you crazy then just go ahead and remove the back now while you can. Then all you have to do is glue an extension block to the head block and then cut it on the proper angle.

This is how I do it for reference.
https://www.tiktok.com/@piusone/vide...81200673441285

[Maniscalco]

Thanks again for the advice - and the video. I do have a Martin mold and used it to line everything up and marking placements. I used it for making the "hoop" but I could not use it for the final gluing of the back to the sides due to weight as I only have partial use of my right arm. The glue up was precise based on the markings I made.

Tonight I unglued the block from the back and saw immediate improvement in the setup. Everything lines up as it should now. I'll either add the wedge as suggested or start with a new block.

Thanks again for all the help.

[redir]

One thing to point out, never rush building a guitar. Maybe wait till you arm heals up

[phavriluk]

About rushing, I have a ten PM rule: stop work. Don't start anything that will go past that time.

And: Don't start jobs with a deadline. Nobody's getting paid.