Acoustic Guitar Construction

Hi, new member here.

I've got this Martin Style OM w/ a M&T joint in progress that's been held-up for a few years now & I'm hoping to get the top on & move forward till completion...as time permits. I was having trouble getting the neck angle correct due to some aggressive sanding at the neck block area when I radiused the top Consequently, the body's less deep (about 1/8") in that area. In fact, it's a bit less than spec all around the perimeter. I think I've got the angle within reason now & was hoping to get some input from those who know?

At front of the bridge, it reads between 5/16" & 3/8" off the top. Since the top is not glued-up yet, I can move the neck & neck block (to & fro) which creates various height readings (+/- 1/16"). However, this is what I've settled on for the final take before closing the box up. As long as I glue the top on where I have it now, I think it will be fine? I radius sanded the underside of the bridge so it mates to the top as well.



Question:In trying reduce the neck angle, I sanded the upper portion of the cheeks on the neck (which helped), but now have a slight gap on 1 side. The string alignment is good but I'm not sure how to go about straightening it out & getting a 'good tight fit' with no gaps once again, w/o messing the way the neck's set now?



The parts:


thanx,
rich

Welcome Rich!
I'm going to make a suggestion before anything else. Go to this website if you have not already, and read the "Success Kit Assembly Instructions". Read the whole thing and pay close attention to the neck set portion. There is a sane, clear and uncomplicated explanation of the 'why's' of your situation.
http://www.kennethmichaelguitars.com/kitmanual.html

In the meantime, I will leave it to Ken or another expert to Rx the situation and advise you. You will come out of this fine.

Hi Rich,

Welcome!

This is really pretty simple to get right. If you don't mind I need to understand what you have here. The sound -board is not attached at this time -- is that correct? You sanded some material off the neck heel so we need to know what angle you made it -- is the finger-board still loose as well? My opening comment "this is really pretty simple to get right" the caveat is that you need to understand that the surface of the neck plane and the sound-board at the finger-board extension form a "straight line" --- it is way premature to be taking the measurements in your photos -- when we get this right those measurements are automatic!! We'll be able to determine the current neck cheek angle with a little math. Please take a few minutes and read the following:

http://www.kennethmichaelguitars.com/neckangle.html
http://www.kennethmichaelguitars.com/ri ... angle.html

Here's the link to the article on the straight line principal:
http://www.kennethmichaelguitars.com/neckangle.html

kencierp wrote:This is really pretty simple to get right. If you don't mind I need to understand what you have here. The sound -board is not attached at this time -- is that correct? You sanded some material off the neck heel so we need to know what angle you made it -- is the finger-board still loose as well? My opening comment "this is really pretty simple to get right" the caveat is that you need to understand that the surface of the neck plane and the sound-board at the finger-board extension form a "straight line" --- it is way premature to be taking the measurements in your photos -- when we get this right those measurements are automatic!! We'll be able to determine the current neck cheek angle with a little math. Please take a few minutes and read the following:

Hi Ken, I've read your tutorials & have been to your site quite a few times in the past, but not of late (note: will review). A lot to absorb & very insightful & helpful. Let alone put into practice. Thx! I have pretty good understanding of what's going on geometrically. I've been working on & building electrics for about 15 years now, so I'm not totally in the dark. Acoustic's are whole new egg & the direction I wanted to go...You'd kinda say, I got sidetracked..

Right: the soundboard is not attached. The board is not glued down either. I am not sure what the angle is exactly after sanding. I started this build a few years ago (about 4). I do remember I got overly zealous w/ a 28' sanding dish & cut the depth at the neck block down some (maybe too much?). The body thickness at the neck block is 3.17" & 4.17" at tailblock w/ top in place. I sanded it in a 000/OM mold when I radiused the rims.

I don't have an accurate angle measuring tool, so I just went & used one of those carpenter's angle slide things & a protractor. I came up w/ a 2 degree angle at the block...guessing? Don't know how accurate that is...

Thx for a quik response,
Rich

Let get a good angle measurement of the neck heel -- place the neck on a flat surface, place a square along the cheek -- what's the height of the heel and the length of the gap between the square and the cheek?

As you may have concluded the idea that you can use a radius dish to establish the neck set angle can quickly cause problems. I am strongly suggest/recommending that you flat sand the top edge of the rim as out line in the instruction above -- don't be concerned about the overall height of the rim "it is a non-issue" And the contour of the sound-board bracing is also of no concern. Here's the mathematical difference flat sand vs 28' radius dish -- negligible at best.

Good thing it isn't a dove tail neck! You came to the right place to get this sorted out and Ken and Dave have already pointed you in the right direction.