Martin D25K "aging" and neck angle

[Rob Mercure]

Folks:

First off this is first post - I want to say that I love the orginal Frets page and feel that this forum is a great second offering from Mr. Ford.

I've got a 1979 Martin D25K - essentially a D18 with Koa sides and back- with the square unadjustable truss rod. In 2003 I had a very good - factory authorized - luthier/repairman reset the neck angle as it had lifted peghead up as Martins do after 15-20 years (I repair mucial electronics and and he and I worked for the same large chain of music stores so I was honored to watch him do it) which made my honey play as I expected. But last year sometime while I was ill and not playing for a while the "neck angle" seems to have changed again - but I feel this is too soon. When I examined the instrument closely though the problem didn't seem to be as much neck angle as the bridge bellying up a bit whild the soundhole area depressed a bit - playing felt exactly like the original neck problem. I really can't figure out what's going on with the instrument as all of the braces seem tight - it's almost like the table "softened" and that area.

Any suggestions as to repair - especially ones that are possible through the soundhole. I've actuall removed and reglued a guitar top before many years ago but I really have trouble working on this instrument since I'm so close to it but my finances are also bad now to farm out the work

Rob

[Jim Bancroft]

Rob,
I really know nothing about the Bridge Dr. but, I do know that most guitars can be repaired properly and made structurally sound to withstand string pull, without any added devices. Some guitars belly more than other, but that is not a problem. I basically examine the inside of the guitar to make sure all bracing is in good shape and glued. If that is fine, and you still have high action that can't be lowered with the saddle, because it is already as low as it can go, then I reset the neck. Possibly your neck wasn't set back quite far enough the first time.

So financially you can't afford the neck reset now. If that is the case, then try the bridge Dr. From what I understand they can easily be installed and removed without altering the guitar.
My ideas are, to leave a guitar as original and unaltered as possible. Yes, a guitar needs to be made playable, but I've found that they can always be repaired without such a devise as the Bridge Dr.
Anyway, best of luck with your decision and getting your guitar repaired.

Jim

[Jeffrey L. Suits]

" I really know nothing about the Bridge Dr."

Breedlove.

[Ned Knepp]

My brother used to have a very light weight Bourgeois that started developing a roll in the face as the bridge lifted. There were no loose braces, just a very responsive but light weight top. The roll wasn't great but it was also not static. We installed a JLD bridge doctor and were able to control are reverse the roll without effecting the volume or tone of the guitar in any way we could detect. It could be that it was louder but this guitar was already pretty loud to begin with and it's hard to tell if it really was or if subliminal suggestion made us think so. I can say that it was not less loud than before and the tone did not seem to change in any way.

The device is actually pretty light weight. I was actually surprised how light it was when I saw it. Obviously, it adds some mass but it seems to be offset somehow, perhaps by the support it gets from the tail block. I would like to point out that our intention was to control the roll of the bridge, not necessarily to flatten the top. The action had already been adjusted for some top bulgingl before my brother purchased the instrument (2nd hand) so our intent was to return it to this position. Of course the belly improved as the bridge return to a better position but we never tried to make the top as flat as "new" so I can't really speak for it's ability to flatten out a bulging top completely. It did prove to be very good at maintaining the bridge belly that was acceptable to us.

Another point to consider is that a bridge doctor CAN be fit without modifying the guitar but that means using the odd brass pins to replace the original bridge pins. Personally, I find this unacceptable because they add unneeded weight and are, IMHO, unsightly. The more elegant solution is to drill a single hole in the belly of the bridge for a screw then fill this with an inlay. It does modify the guitar but it is also lighter while being much nicer to look at. ( No one ever noticed the extra dot inlay in the bridge. ) If you want to remove it later you will retain a single round inlay dot or you can fill the hole with a matching wood plug. There used to be instructions for both installation methods on the JLD site.

All in all, it did exactly what we wanted and was fairly easy to install. I wouldn't hesitate to use one again.

Ned

[thefishinmusician]

I was given a bridge doctor years ago to try out, but I just could not understand the instalation instuctions....So it still sits...Have they made it clearer or am I dumb as a stump?

[Ned Knepp]

It helps a lot of you can see one installed. There are two different versions of this "tool" out there. One looks like the one in the online instructions. It's much more complex than the one we installed. Where the instructions use a block under the bridge and another under the saddle with a peg for alignment between them plus the adjustment rod which presses against the tail block, the unit we installed is simpler

This one is a single block of redwood or cedar, not sure which, that was about .75 inches thick. This has been cut in an "L" shape with the vertical part of the "L" left only about .25 inches wide while the bottom of the "L" is about the full width of the bridge and extends down another 2 inches or so from the horizontal cut. The online instruction show a device with two parts connected by the alignment pin and the adjustment screw for the adjustment mechanism.

Ours was a single block. The attachment to the bridge is handled but a solid plastic post that has what looks like a dry wall screw embedded into one end and is threaded on the other end for a flat head phillips screw that passed through the bridge of the guitar. The dry wall screw end of this plastic post screws into the block vertically, making it parallel with the thin vertical part of the block which fits under the saddle. The screw is long enough to hold this pin very firmly once the block is in position and there is a wooden dowel glued in the block to give some cross grain holding power.

The bottom of the block has a horizontal hole, running from the front edge of the device through the width to the back edge, which is fitted with a plastic liner. This is where the rod goes back to the tail block. The front of this hole has an inset Allen screw which is used to adjust the rod pressure on the tail block. It's actually an elegantly simple device. ( Personally, I think it a brilliant design. )

The important thing is making sure the top of the vertical leg of the "L" makes good contact and is well positioned under the saddle. You want every thing to fit squarely under the bridge with the pressure point under the saddle and the pivot point at the back of the bridge. It would be easy to get busy trying to keep the mounting hole out of the way of bridge pins and forget about this. There were three predrilled holes in the block for the plastic pin to screw into but it wouldn't be hard to drill your own pilot hole if you need to position it in another place. Just make sure you don't get it too close to the back edge of the block.

When you drill the hole in the bridge, remember that it should be vertical. The point is to bring the block up against the saddle and the back of the bridge squarely, then use the rod to lever the front of the bridge around the pivot point created with the plastic post at the back of the bridge. If you don't get the mounting hole fairly vertical, you will not create a good "square" pivot point and you probably won't have a good solid connection at the front of the bridge either.

We decided to make this hole and countersink it by hand rather than using a power tool. Good bits and a hand powered drill is less likely to produce tearout and it give us better control over the depth of the countersink so the inlay will fit better. BTW, our kit included the inlay.

This all sounds complex but it really isn't. If you can see one that has already been installed, it pretty clear how it works and how it fits. Even the more complex one shown in the instructions works in the same manner. Once we saw it in action it wasn't all that hard to figure out how to fit our simpler model. I keep saying "we" but it's really a one man job. We fussed with it and worried before we drilled a hole in the bridge because it was an expensive guitar but once we got past that, it wasn't nearly as traumatic as we feared. It's not too hard to get things right if you verify the positioning of the plastic post and the front of the block on TOP of the guitar before you start drilling holes.

One more thing. We probably took more time than we needed to in adjusting the rotation of the bridge. We only needed to rotate the bridge a little but we did it a bit at a time over a few weeks. That kind of time is a luxury a repair man may not have but we were afraid of putting undue strain on glue joints and such so we took it easy. I can't really say how quickly this can safely move a top back into shape. I suppose that would depend on the guitar but, in retrospect, we could have achieved that same results much faster than we did.

One more thing. Pauls comments about humidifying are good to keep in mind. It would probably be best to insure that the instrument properly humidified before doing this.

Ned

[Ned Knepp]

Now that I've posted all that, I found a site with a pretty good drawing of what I was trying to describe. It's a site advertising their repair work and selling bridge doctors but the drawing on the top left can be enlarged and this is the design I was talking about.
http://www.bluestarmusic.com/accessories-47/guitar-repair-48/jld-br...

It isn't detailed but it shows the simplicity of the one we installed.

Ned

[FRANK]

re humidify properly check the Martin Forum on how to go about this sounds dry

[Mike Kolb]

A customer had me convert his Breedlove nylon-string acoustic to a steel-string. In addition to metal tuning rollers (vs. plastic), a bridge conversion (from string-through to pins), and a reinforced bridge plate, I opted to install the Bridge Doctor as a little additional insurance.

It worked out just fine but -with all the other changes- it's hard to tell exactly what the JLD system did & didn't do. I can say that, even with the additional tension of steel strings, the guitar has remained stable for the last year. It sounds great and the customer's pleased, so that's what counts.

Insofar as the instructions go, they were just OK.... but their website offers an even better (well, OK, a different) set:
http://www.jldguitar.net/install/instructions.html

[Rob Mercure]

Folks,

Sorry I haven't been part of the discussion since I started the thread but I had forgotten the password I used - I am at a "foreign" computer - and could't log on. Since my last post I ordered a Bridge Doctor and installed it. While the printed directions are funky a quick review of them and of the website (which I printed) allowed me to install it in about 15 minutes. It was quite easy and the screw that attaches it to the bridge was of much better quality than a "dry wall" screw - but perhaps their quality changes from time to time. The device is so simple that once you've seen one you could make another in about 10 minutes with normal wood working tools. Anyhoo the device quickly straightened out the bridge and allowed my guitar to be playable again. whether it changed the sound or not I don't know as I had not played the guitar in a while due to illness (it was while I was ill and it was in the case for months that the symptom developed). One thing that would be helpful from the company - or perhaps from the crew here - is how to "optimally" adjust the device as you can't easily get an allen wrench in while the strings are on the guitar - sort of like adjusting the old Fender truss rods. While I'll probably leave it for a while as I'm still not recovered I can see that getting the best results are going to take some trail and error and this is why some tips/guidelines would be helpful.

Anyway as the thang is cheap I recommend it for those whose needs it best meets. In fact if I had one when my neck first went out I might have used it temporarily until I could get the reset done since it can just be stuck in a drawer and reused once one can put more time and effort into the repair. In fact this might be a good accessory for an acoustic musician on the road for emergency use if you don't have several guitars available.

Rob

[Ned Knepp]

Rob,
I wasn't inferring that the screws were cheap, I was simply referring to the type of screws involved. The plastic post on our's has an embedded screw that looks exactly like a 1 inch, zinc coated, headless drywall screw. This is what screws into the device, not the bridge. There is a stainless steelscrew that attaches the device to the bridge.

When we adjusted the device, we just loosened the strings enough to get to it and tightened the tension a bit. Like I said, we probably took to long but when the top was back where we wanted it, we just stopped making adjustments.

I'm a bit confused about how this could be used as a temporary patch for a neck reset. Doing a neck reset wouldn't control the twisting of the face of the guitar that a bridge doctor controls. I don't think a bridge doctor will keep a face from bulging from the string tension but it will keep it from rolling.

Ned

[Rob Mercure]

Ned, I've never seen a "headless" drywall screw - if you've ever hung drywall you know that you need as much "head" on the screw as possible (note: I hereby resist all my normal instincts to make bad puns here!) to hold the paper covering. But I'm not an expert on drywall screws.

Anyhoo, as best I know the neck reset on a Martin isn't to correct for any actual problem with the nect angel but a misalignment caused by the bridge bellying up - which is usually asymetrical with much of the same pivoting of the bridge with the back lifting and the front sinking. As least this was how my bridge on my Martin looked when it was reset and the reset fixed it. But perhaps there are other reset related issues that I'm not familiar with as the only actual reset situation I've been associated with was fixing my guitar - by an experienced repairman that I worked with - but I did look at many other instruments that he was in the process of fixing for other folks and most seemed to be similar to mine. Again my experiences are limited. But I'd still recommend it as a road tool along with all the wrenches and nut drivers and screw drivers and files and such you need (and since I do electronics: meters, and portable scopes and spare tubes, etc.,).
Rob

[Ned Knepp]

Yes, Rob, I have hung dry wall.

First of all, I was describing what I saw and, personally, I don't need to have the head attached to recognize the thread design used on dry wall screws. Perhaps you would call it something different but I see what looks just like a zinc coated dry wall screw with the head removed and that end inserted into one end of the plastic post included in the kit. That's what was in the one we installed and is in the spare I still have. ( I dug it out and checked.) Maybe JLD special ordered screws for this but it still looks like the threaded shaft of a dry wall screw to me.

As for using a Bridge Doctor as a temporary fix for a neck reset, I guess that I see them as different "fixes". JLD's system appears to be specifically designed to deal with bridge rotation which may not be the only reason for a neck reset and may not correct all of the "belly up" bulge that develops as an instrument ages. I agree that it would be a good thing to take on a road trip, I just don't see it as a temporary fix for a neck reset, I see it as a permanent fix for bridge rotation. I don't have a lot of trouble seeing where both could be needed.

I suppose it could work in the way you say but I don't understand why I would want to remove it and either pay for or do a harder repair. If the Bridge Doctor fixes the problem, I would just leave it.

Ned