Neck Block Buttress, but How?

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Neck Block Buttress, but How?

Postby Randolph Rhett » Sun Feb 25, 2018 10:55 pm

I was hoping that some with experience building with the neck block (or tail block) supporting buttresses can share their experiences. I've tried on a couple of guitars, but always have a problem with figuring out how to anchor the carbon fiber rods to the guitar side.

Getting the angle from the top of the neck block to the bottom of the waist is complicated enough. Actually drilling the neck block to receive the rod at the correct angle has been VERY challenging. Then figuring out how to receive the rod at the bottom of the waist against a curving surface has me spending hours of trial and error fitting, cutting and re-cutting little pieces of wood, drilling and re-drilling holes to receive the rod, etc.

What shape or size piece is the rod inserted to? How do you fit the piece to the curvature of the sides? How do you test fit the length of the buttress rod? How do you glue/clamp it all together? Is there an efficient, simple, repeatable way fo doing this that I'm just too dense to see? I very much like what these buttresses to for me, but it is becoming a bottleneck in the production that introduces too many opportunities to mess up. I'd love to see what others have come up with.

Thanks!
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Re: Neck Block Buttress, but How?

Postby Barry Daniels » Mon Feb 26, 2018 2:25 am

Sorry you are having trouble with that. I've only made a few with flying buttresses but they seemed fairly easy with a few techniques and tools. The main tool is to have a long (like 12 or even 16" drill bit of the diameter that your carbon tube will be. So to find a match pick a common diameter for your rods like a 1/4". I buy 1/4" kite spars from Intothewind.com http://intothewind.com/avia-carbontubing-for-kites

My process was to shape a couple of support blocks of mahogany that are mostly curved freeform on my Shopsmith's 12" disk sander. The mahogany supports are about 1" cubed, maybe a bit more in one axis. The only closely fitted surface for the support is where the block fits the inside curve of the sides. This should be somewhere in front on or directly on the narrow part of the waist near the back. Also make a semi-flat face at is close to perpendicular to the desired path of the rod.

Glue the block to the side in an inset of the lining so that the support will also fit the back. Once dry get your long drill bit chucked up and take aim. Drill slowly and place tape over faces to prevent splintering during break though. First drill though the back of the support while aiming at the point on the headblock where you want the rod to enter. Drill through the support. With the drill bit in between the two supports, place a piece of tape on the end for the depth of to rod you want in the headblock. Now go ahead and drill into the headblock. The rod can be inserted through the aligned holes. Glue in place with CA. When cured saw the end of the rod off.

I hope it's obvious that this is to be done to the finished rim set before the top and back are glued on. I couldn't find a photo of a rim support but here is one of a laminated angle headblock that uses a similar drilled in place approach.
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Re: Neck Block Buttress, but How?

Postby Randolph Rhett » Mon Feb 26, 2018 10:01 pm

So Barry do I understand that you first glue the support block and head block to the rims without holes to receive the CF rod? Then, from the outside of the body you drill a through hole in the head block all the way to the support block already glued to the inside of the waist? That sounds a little scary, but very ingenious.
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Re: Neck Block Buttress, but How?

Postby Barry Daniels » Mon Feb 26, 2018 10:36 pm

I do this on the rim set before the top and back are attached. Glue the support block in place. Then I drill though the back of the support block all the way to the headblock. This eliminates having to line up two blocks with holes already drilled. Nothing scary about it. It's just a drill bit. You can get the long drill bit in the electrical section of Home Depot. I have found other uses for it.
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Re: Neck Block Buttress, but How?

Postby Randolph Rhett » Mon Feb 26, 2018 10:53 pm

I assumed that you were drilling through the head block where the neck would cover the hole in the rim. How do you disguise it when drilling through the waist?
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Re: Neck Block Buttress, but How?

Postby Bill Raymond » Tue Feb 27, 2018 12:50 am

Randolph, I believe Barry is saying that he drills through the support block at the waist towards the neck block, not through the side itself--the support block being glued to the inside of the side, a hole directed from the support block towards the neck block would not penetrate the side, and the hole in the neck block is a stopped hole, stopping short of penetrating the side.
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Re: Neck Block Buttress, but How?

Postby Randolph Rhett » Tue Feb 27, 2018 1:06 am

I’m sorry if I seem dense, but he said he glued the support block to the side first, and then with a long drill drills through the support block to the neck block. How can he start drilling from mid block OUT toward the neck? The only thing that makes sense is a through bore. But the backside of the support block is glued to the rim already. You would have to drill through that as well.

Am I misunderstanding and it is being done in two operations? First starting from inside the body drill the support block short of the side, then a second drilling from the inside drilling a hole into the head block? If so, how does one make sure the two holes are aligned? Just eyeballing it? If so, that is precisely where I am having trouble.

Or is it being done BEFORE the rims are glued to the neck block/support/both? If so, again how are they being aligned so that when glued to the rim they fall in the right place?

FWIW this is how I’ve done it on two guitars. I tried to carefully measure the angle (40° out from perpendicular and 12° down) and set up the drill press. But,of course, when working with wood nothing is that simple. Things shift or don’t bend EXACTLY like the plans. In the end I had to create some slop in the holes so the rod would line up properly. If the point is to add rigidity, there needs to be no slop. Just eyeballing it and hoping the two holes are colinear doesn’t work for me. My “eyeballs” aren’t that good.
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Re: Neck Block Buttress, but How?

Postby Bill Raymond » Tue Feb 27, 2018 8:35 pm

Since the support blocks are glued to the inside of the sides the hole is directed in an upward (towards the top) and inward (towards the center of the neck block) and thus can be drilled without touching the side provided the support block is located near the narrowest part of the waist of the guitar near the edge to which the back will be glued. Were it close to the wider part of the upper block or nearer the surface to which the top will be glued, then the hole might have to penetrate the side.
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Re: Neck Block Buttress, but How?

Postby Barry Daniels » Tue Feb 27, 2018 10:14 pm

This may help:

The face of the support block that the drill bit enters first is the one that will be latter attached to the top/back plate. Drill all the way through the support block while aiming the drill bit towards the headblock and then keep going all the way to the headblock.
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Re: Neck Block Buttress, but How?

Postby Randolph Rhett » Tue Feb 27, 2018 11:24 pm

Yes! Thank you. Now I understand.
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Re: Neck Block Buttress, but How?

Postby Barry Daniels » Wed Feb 28, 2018 11:37 am

The carbon fiber rod is installed in the same direction and beginning point as the drill bit.

By the way, my carbon fiber rods normally were inserted from near the back and angled up to near the top of the headblock. The support block was usually placed just in front of the narrowest part of the waist.
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