fretboard extension gap

[david miles]

Hello Forum.
I am about to start making two OM size acoustic guitars and there is one thing I am unclear about. When making the heel to body dovetail joint and setting the guitar neck down slightly below horizontal to get correct clearance at the lower bout bridge position, won't the fretboard extension be lifted clear of the body by a small amount? How do you overcome this problem?

David Miles.

[Fathand]

You have to measure the angle from the guitar top to the side at the neck joint. It is probably close to 91°, depending how much curve is in your top. You then make your neck heel to the same angle. If there is still a little gap you can glue a wedge to the bottom of your fretboard extension.

https://flic.kr/p/2n8PUpK

https://flic.kr/p/2n8PUzE
On a flat topped instrument like a uke or classical, it is likely to be more like 90° but you should still measure in case your build was less than perfect.

This is easier on a mortise and tenon joint.

[david miles]

Thanks Fathand. I had assumed that the soundboard would be flat at that point. I had forgotten that it would be slightly curved. I can stop worrying now!

[JonWint]

Martin bevels the neck block 91 degrees (top) and 5 degrees (back) for modern back arch. The top needs to be flat under the fretboard extension.

What plans are you following?

[Taylor Ham]

The way I've done it is this:

The top transverse brace has a 25 ft radius, and my rims are un radiused. The amount of induced arch above the soundhole is about right to meet the fingerboard extension, and I do some very light sanding in that area to make a tight fit. Usually all that's required is to flatten the area under the end of the fingerboard extension.

I include a support for the fingerboard extension like the Taylor NT neck.