U2boy Posted April 23, 2008 Report Share Posted April 23, 2008 Hi all! First time post. I could use a bit of advice, and I must apologize in advance for my terminology. I own a Martin DXM Dreadnought Acoustic, made of HPL. It recently took a nasty spill on a hard tile floor which has resulted in about half of the back of the guitar separating (split) from the body. Broken Martin I can't afford a professional repair at this time, so my plan is to simply glue it back into place so I can play it once again. I'm not overly concerned about it's appearance, I just want to make sure it's sturdy and prevent the rest of the back from separating. So I guess my main question is: Is there any specific type of glue that I should be using, or just good ol' plain wood glue? Any simple suggestions would be greatly appreciated. I'm def. not the mechanical type when it comes to instruments. ;] Thanks in advance! Quote Link to comment Share on other sites More sharing options...
jammy Posted April 23, 2008 Report Share Posted April 23, 2008 Easy fix that. Just apply the glue and clamp 'er up (That is provided the back goes back in to place with light pressure, leaving no gaps) Use titebond original. Quote Link to comment Share on other sites More sharing options...
fryovanni Posted April 23, 2008 Report Share Posted April 23, 2008 Easy fix that. Just apply the glue and clamp 'er up (That is provided the back goes back in to place with light pressure, leaving no gaps) Use titebond original. Jammy, What kind of glue does Martin use to attach the back to the rim originally? I am sure he could do an existing HHG with little prep, but Titebond over old glues is not usually a real solid bond. Maybe a bit of a prep would be good if he is going to use Titebond. Quote Link to comment Share on other sites More sharing options...
jammy Posted April 23, 2008 Report Share Posted April 23, 2008 Good question, well asked too With it being one of their lower end models I'm not convinced this will be a HHG construction. U2boy: As mentioned it could well be worth cleaning up the mating surfaces before the repair Quote Link to comment Share on other sites More sharing options...
GoodWood Posted April 23, 2008 Report Share Posted April 23, 2008 Good question, well asked too With it being one of their lower end models I'm not convinced this will be a HHG construction. U2boy: As mentioned it could well be worth cleaning up the mating surfaces before the repair Well, you should tell him how to clean the surfaces so they will have a better job of still matching when he glues it back. It looks like a "good" split, the glue joingt failed, not the wood. Im thinking warm water, heat, and some type of scraper to prep the surfaces? Also, dont over clamp it. Or over glue it. Quote Link to comment Share on other sites More sharing options...
fryovanni Posted April 24, 2008 Report Share Posted April 24, 2008 Im thinking warm water, heat, and some type of scraper to prep the surfaces? Not sure what finish Martin uses on this model, do you know? Sometimes water and heat will have negative effects on a finish. Quote Link to comment Share on other sites More sharing options...
U2boy Posted April 26, 2008 Author Report Share Posted April 26, 2008 thanks to everyone for the input! going to give it a whirl. my roomie is semi-decent with woodwork, so hopefully we won't screw it up too bad. Quote Link to comment Share on other sites More sharing options...
GoodWood Posted April 27, 2008 Report Share Posted April 27, 2008 It begs a question I had about using dishes, as this seems to input a bit of stress on the guitar. I was thinking the other night about molding backs and tops with heat, like you do the sides, so they dont have that tension built in. On the top that cant be a good thing. Quote Link to comment Share on other sites More sharing options...
Setch Posted April 27, 2008 Report Share Posted April 27, 2008 I suspect you're searching for a solution to a problem which doesn't exist - as evidenced by the countless millions of acoustic guitars with domed tops which are doing just fine. Besides, a top which is stressed so it wants to pull flat is probably no bad thing, given that it's being pulled on by strings trying to make it go the otherway... Quote Link to comment Share on other sites More sharing options...
fryovanni Posted April 27, 2008 Report Share Posted April 27, 2008 It begs a question I had about using dishes, as this seems to input a bit of stress on the guitar. I was thinking the other night about molding backs and tops with heat, like you do the sides, so they dont have that tension built in. On the top that cant be a good thing. The whole idea behind using dishes is to minimise focused stress. By that I mean at the joint itself, and matching the curvature of the shaped braced to the shape of the rim. If you used a flat soundboard, you would want to match the rim also. If you are talking about forcing the soundboard into a radiused shape vs using flat braces. Nothing wrong with either. However, the radius has advantages. If a top is flat, then becomes dryer than it was when assembled it will pull on the sides creating stress, with a radius it will flatten a bit. If a flat top becomes wetter than it was when assembled it will pop in or out(under string tension you would expect out), with a radius it just flexes a bit more(with the radius it was given). This movement is totally normal and will happen. Your top will experience this expansion and contraction creating stresses no matter what. A radiused top will also have more strength than a flat top, which seems to be nice. As Setch mentioned a soundboard will also face string tension, and rotating forces when strung up and tuned. Stress is what a soundboard is all about, there is no way to get away from that. You can just build it to deal with stresses as well as you can. As far as using heat to form a top. You could, but I doubt the top would be better suited to content with forces acting on it. Even if you left it unstrung it will face natural dimensional changes that will introduce the stresses you tried to relieve, and then it may or may not contend with them well. Also heating wood to a high enough temperature to allow bending does create a small loss of strength, repeated heating will significantly weaken wood. That would be a consideration. Just in case that brings to mind a question about "baking" tops. The level of heat is not high enough to break down the lignun(it is more of an overdrying process), and it seems that at least initially there is an increase in strength. Slightly overdrying a top during assembly may aslo have the benifit of reducing the chances the top will want to pull with as much force against the rim if it shrinks due to drying(tops like to split if that becomes drastic). That is just what my understanding is, for what it is worth. Rich Quote Link to comment Share on other sites More sharing options...
Mattia Posted April 30, 2008 Report Share Posted April 30, 2008 Also, let's put this into perspective: anyone who's ever pushed a thicknessed, unbraced top or back into dish will be able to tell you it takes a fairly minimal amount of pressure (one finger, a pinky will do, moderate pressure) to get the top to adhere. The tension on both back and top comes from the strings (torque on the neck block for the back, torque on the bridge for the top). That little bit of arching isn't 'stressin' much of anything, and for the top at least, what little stress there is is being more than counteracted by the strings. What doming does creates a bit of space for the top to contract (flatten) without cracking, as well as adding strength (thanks to the shape). Now, gluing arched tops to flat rims (as Huss and Dalton do for some of their models) introduces different stresses, and (apparently) changes the sound as well. Besides who says tension isn't good in a top? No tension = no sound. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.