Q: I would love an opinion on strings for my 1936 Martin D-18. Medium-gauge strings sound greatest, however generally I fear concerning the neck! Will mediums put an excessive amount of strain on it over time? If I do use mediums, wouldn’t it be good to loosen them some when not taking part in the instrument? —Dave, by way of e-mail

A: Congratulations—a 1936 D-18 is sort of an instrument! Martin data point out that solely 258 of those guitars have been constructed that 12 months, and plenty of haven’t survived. Your guitar options the forward-shifted X sample that has turn out to be legendary. For all these causes, it’s gratifying to listen to that you just take its care severely, as too many of those historic guitars have gone to early graves.

Earlier than we get to the string gauge query, let’s take a fast have a look at how string pressure normally impacts a flattop guitar—bending the neck and distorting or “bellying” the highest. Each may end up in excessive motion, so it’s necessary to know which is which when evaluating a classic instrument. They require totally different methods to appropriate, and might have totally different implications for the long-term well being of the instrument.

A bowed neck is straightforward to diagnose. Cease a string on the first fret together with your fretting hand, and use your different hand to cease the identical string on the 14th fret. This positions the tensioned string as a straight-line reference, which can be utilized to find out neck curvature. Have a look at the seventh- and eighth-fret positions to see how a lot area there may be between the fret tops and the underside of the string. For many taking part in types, a niche someplace across the thickness of a enterprise card is right. If the neck has a major ahead bend, a reliable luthier can use quite a lot of methods to straighten it out, together with heating or refretting with larger-tang fretwire. 

With a contemporary guitar, dialing within the correct neck reduction requires not more than a easy truss-rod adjustment. Your D-18 has a nonadjustable, T-shaped metal stiffening bar within the neck, which most classic Martin specialists agree is powerful sufficient to assist string pressure over the long run. If there have been a specific weak spot in your guitar’s neck, it could almost certainly have already got bowed by now.

Bellied tops are frequent in outdated flattops, and should not essentially an indication of weak spot—most guitars which can be constructed calmly sufficient to be highly effective and responsive will exhibit a point of bellying, particularly after 80 years! Nevertheless, a bellied high can generally point out bigger points, akin to free braces, which may result in cracks, wrinkles within the high, and different existential threats, so correct analysis is necessary.

On a brand new instrument, it’s typical for the highest of the bridge (not the saddle, however the bridge itself) to be in airplane with the fret tops. So, in the event you lay a ruler on the frets, it ought to land proper on the floor of the bridge. Although this varies with particular makers and fashions, common top of the bridge is about 3/8 inches from the floor of the highest, with the saddle roughly 1/8 inch above that.

As the highest distorts over time, the bridge rises, and the motion goes up with it. The frequent treatment is to decrease the peak of the bridge saddle. This does get the motion again down once more, but it surely additionally impacts an necessary variable within the guitar’s response—the quantity of torque (rotational drive) the strings exert on the highest. A excessive saddle places larger torque on the highest, and every guitar has a super quantity that can maximize quantity and responsiveness. Reducing a saddle too far reduces this torque and might generally end in a lack of energy and sound high quality.

On older guitars with considerably bellied tops, it’s frequent to see bridges which were reduce decrease to steal a bit of additional clearance and additional decrease the saddle. It is a poor strategy for a lot of causes. It additional worsens the torque downside and likewise weakens the bridge, which is a vital structural assist element of the highest. In truth, shaving down a bridge—and thereby making it extra versatile—can enhance the chance of high distortion sooner or later.

Restoring a bellied guitar to correct playability is a job for a professional luthier, and normally entails a neck reset—removing of the neck utilizing steam, and re-cutting the joint to extend the neck angle, which repositions the fret floor into correct alignment. reset might be almost invisible and can normally protect and even enhance resale worth of a classic instrument, fairly than detracting from it. 

Bellied tops may also generally be flattened utilizing warmth and moisture, and this strategy has been confirmed profitable as a less-invasive various to a full reset. Restoration professional TJ Thompson’s efficient instruments and methods for fixing bellied tops with warmth and moisture are gaining reputation in restore retailers.

Returning to the string gauge query: for many producers, medium refers back to the set gauge of .013–.056. The general pressure on a mean medium set is round 185 lbs., in comparison with 160 for a lightweight set (sometimes .012–.054)—a distinction of about 14 %. By comparability, tuning your 13s all the way down to D (one entire step) lowers the strain to 145 lbs., or about 20 %. (Because of D’Addario’s stringtensionpro.com for supplying these numbers.) So, in the event you tune down between taking part in classes, mediums in D will put much less stress on the guitar than light-gauge strings at commonplace pitch. (That D-18 in all probability sounds nice tuned down a step, as properly!) One other good possibility can be a hybrid set of blended mild/medium gauges, which might preserve the strain decrease whereas nonetheless supplying you with the sound you’re after.

To additional reassure you: If the saddle has been lowered in your guitar within the final 80 years, and it seemingly has, then the torque on the highest may have been diminished, too, which lowers the danger. This can be why you like the sound of the medium-gauge strings—they might put a load on the highest that’s similar to what light-gauge strings would produce with a taller saddle.

To reply your different query, typically, I don’t assume it’s essential to tune down for storage, offered the guitar is structurally sound. Frequent speedy modifications of any type (humidity, temperature, or pressure) are greatest averted with classic devices. However in the event you do select to tune down, a whole-step drop needs to be greater than sufficient.

Every year we lose a couple of extra classic guitars to wreck, neglect, and dangerous restore work. We’re stewards of those devices, and with correct care, they’ll and may outlive us. It appears like your D-18 is in good fingers.

Martin Keith is a luthier, restore and restoration professional, and dealing musician primarily based in Woodstock, New York. martinkeithguitars.com 

This text initially appeared within the September/October 2019 difficulty of Acoustic Guitar journal.