Starting a new build and have a question, need some ideas

[Kevin Sjostrand]

Hi gang
I have not been around much lately, but I'm retiring in 3 MONTHS and should have much more time to spend in the shop to build guitars, so I hope to share my projects with you all again starting with my next one.

I am about to start a new guitar, an OM, probably a cutaway. This will be my 16th. Some of you know I have some of my guitars living in India; at this time there are 5 there. India is a very harsh environment for guitars, especially in the area mine reside due to high heat, and high humidity....and lots of moisture during monsoon season. All of the guitars have suffered to some degree. The very first guitar has been there over 10 years now and held up very well up until just recently, where it was left unattended for 6 months and not cared for, now it is experiencing ill affects. I built that dreadnaught heavy on purpose and it has held up the longest. So, all that said, I have an idea for my next guitar which at some point may also be taken to India. I'd like to try and build it to better withstand at least some of what might happen; changes to the top and neck especially.

There is a luthier in Goa, India, Karan of Bigfoot Guitars who has looked at a couple of my guitars there. He made at least one suggestion that I'd like to give a try. Martin has used (not sure if they still do) on some of their guitars, my understanding at least, a heel block inside the guitar that has an extension attached that supports the top under the fretboard extension. It seems like this extension could really aid in keeping the top from sinking here from the downward pressure and force of the fretboard extension.

John you are the Martin guy so I'm hoping you will chime in also. I have never built with a heel like this but think I should give it a try. So I guess my question is this.

Have any of my fellow builders used this type of heel block and, is there anything I need to know about the geometry that will change how my neck angle is set, or what if any other bracing will be needed on the top above the sound hole in this area? I am also considering trying a screw down fretboard extension incorporated in this process, which I also have not done before. I can probably figure all this out as I go once I get into the build, but sure would appreciate any input, especially if any of you guys have used this type of heel block extension, and a screwed down fretboard extension.

And then, the isssue of bridge forward rotation. All the guitars are doing this to some degree. Any ideas on some other bracing other than standard X bracing, Martin style that might combat this problem?

It would be great if these guitars could be kept when not in use in an enclosure with a means of controlling the humidity, but that is not practical for most of them. The newest guitar I just finished this year is now in India, and my son in law is going to keep it in its case and use silica packs to try and keep it dry, but I don't think it will be regulated. Hopefully it will help..

Thanks for your input, comments and advise. I appreciate any and all. I know lots of you guys have much experience and I value it all. Fifteen guitars has not by any means made me an expert. I feel like I've just broken the surface on becoming accomplished at this craft. Its going to feel good to get this next guitar going. It is for my oldest granddaughter who will be starting college here in the US next summer, so it will spend its first year here in California.
Thanks again guys.

Kevin

[tippie53]

Martins uses of the cantilever is there as a production tool it is cheaper to put that on the block than to fumble with the caul to glue on the extension. If you look at the design there is a very small gluing surface. I pull a lot of necks and most martins do have top cracks along the fret board.
this is from shrinkage differential of the spruce and rosewood or ebony. It doesn't stop neck resets. If you want to make the guitar stronger use the old style neck block that martin stopped using in 1939 make it about 1 9/16 thick.

[phavriluk]

Kevin, for my neck block installations I add a 3/4" thick, wider than the fingerboard, birch ply extension between the neck block and the transverse brace in front of the sound hole. These two bits are installed while the rim is in the mold before kerfing is added. This strongly limits the neck block's rotating.

[tippie53]

I have been doing this over 20 years
I have guitars over 20 yrs old I only had to reset 1 neck. since I went to the thicker block that helps but in the end you can expect a neck to rotate you can't stop it as that is part of what wood will do. I have seen buttresses I have seen Spanish foot so there is a trade off .
the neck block isn't the only thing that moves , the bridge rotates and the top rises. There is a balance and plan that . I also use a higher transverse brace. My brace is like the old martins of about just under 3/4 high and 5/16 thick.

If you do the cantalever you may only need 3/8 in thick you don't need as much as you may think

[banjopicks]

Martins uses of the cantilever is there as a production tool it is cheaper to put that on the block than to fumble with the caul to glue on the extension. If you look at the design there is a very small gluing surface. I pull a lot of necks and most martins do have top cracks along the fret board.
this is from shrinkage differential of the spruce and rosewood or ebony. It doesn't stop neck resets. If you want to make the guitar stronger use the old style neck block that martin stopped using in 1939 make it about 1 9/16 thick.

Do you have any photos of the cantilever you speak of?

[tippie53]

here are 2 pics You can see the cantilever this is only a clamping caul and has not real structure to the top.

[banjopicks]

Thanks for the pictures John. I still do get it though :-) I don't understand the shape of the neck block and it's purpose. As for the caul, I assume that stands up under the neck block extension and something needs to fit past the end of the block, hence the grove. I'll do some research, I can't expect you to do all my leg work.

[banjopicks]

Did my research and have no idea what the slots are for.

[Kevin Sjostrand]

John, so that extension for Martin is for clamping...as I now look at it, that makes total sense; for them, but for us guys of course, we just use a caul. Now, the idea of a spanish foot as used in Classicals is kind of what I was thinking.
More support under the fretboard to help keep it from sinking. I realize we are talking more weight, but isn't it true that that area of the soundboard really doesn't affect the vibrations and sound of the guitar, so having an extension there shouldn't be much of an issue there?

This will also aid in a way to screw down the fretboard.

So my heel blocks are around 1.5". Other than weight, would making it 2" deep help much in this area? I'm thinking the extension maybe 2" long, width of the fretboard, and 1/2" thick...basically a spanish foot. Screws up through into the fretboard into treaded inserts.
Comments?
And thanks guys for chiming in. I appreciate all thoughts and ideas.

Kevin

[tippie53]

the best thing I can say is make it the way you think and see what it does. No true discovery was made by staus quo thinking.