Neck-Shimming and Ski Jumps: The Latest Research

Ok. So, the word ‘research’ might be over-stating things as I’m mostly forgetful and don’t remember to check and photograph this stuff every time I encounter it.

However…

In the last few days, I’ve had three different Strats through the workshop, each of which have had to have fretwork to address ‘ski jumps’ at the end their necks. I forgot to photograph the first of these until it was all strung up and ready but — because these three came in succession — I remembered to document the others. Sometimes it's good when these weird three-things-at-the-same-time coincidences happen.

First a recap (and, as this isn’t the first time I’ve written about this, I’ve included some links at the end.

I’ve seen ski jump deformations on poorly shimmed instruments often enough to strongly recommend full-pocket shims.

What’s a guitar neck ski jump?

If you picture an actual ski jump, you’ve got a long, mostly straight, portion and a short kick-up at the end. Picture your guitar neck like that.

What happens is the last few frets kick up. This means you can get a lot of fret buzz and note-choking, especially as you go past the octave.

End-of neck ski jump deformation

It’s important to note that these frets are not raising out of their slots or coming loose. The portion of neck where they're installed has deformed and raised in relation to the rest of the neck.

What causes a ski jump?

Well, this can happen on any guitar. It’s not necessarily limited to bolt-on necks, although it’s definitely more common on those instruments.

And, in my experience, poor neck shimming practice can make this problem much more likely.

Now we have to recap on shimming.

We shim a guitar to change the angle it attaches to the body and adjust that angle. The most likely reason for this is to address a problem where the bridge saddles are bottomed-out but the action is still too high. Shimming the neck and changing the angle makes a better action possible. Shimming can also be done to address problems on Fender’s offset guitar bridges. We can raise the bridge to give the strings a better break angle over it while not having to suffer the super-high action that would ordinarily happen if we moved the bridge up.

What’s the problem with shimming necks?

Many players — and too many repairers — will shim a neck by popping a short piece of card or thin wood in the neck pocket, under the very end of the neck.

No! Bad!

The common (and wrong!) way to shim a guitar or bass neck

Many used to decry this ‘short shim’ practice for reasons of tone. That air-space between neck and body doesn’t make for the best coupling and that certainly has the potential to impact an instrument’s tone.

However, I’m on the ski jump bandwagon here. Bringing things back to where we started, I believe strongly that poor shimming contributes greatly to the chances of a ski jump happening.

I’ve talked about this before and will again. I’ve seen people discuss my shimming posts in forums where some have called them bullshit and I’m ok with that. I’m still going to keep pushing this because, in my experience, shimming a neck with a short shim at the end is likely to cause deformation over time.

Really.

I know it sounds nuts to think that that piece of card under the end of the neck could deform that hunk of maple above it but I’ve become more and more convinced that it can.

A while back, I published a photo showing the portion of neck that sits in the pocket. It had been shimmed, it had a ski jump that needed fret-work, and it had a deformation on the bottom matching the ski jump at the top.

Like I said, I (stupidly) forget to check and photograph every guitar that comes through the workshop with this problem but I’ve checked two in the last couple of days. Photos below.

Neck heel deformation found on shimmed guitar (1)

Neck heel deformation found on shimmed guitar (2) - Microtilt used on this instrument

Both necks had ski jumps. Both needed a fret level to try compensate for the (now) higher frets at that end of the neck. Both had been shimmed — one with cardboard and one using Fender’s Micro-Tilt mechanism.

And both have deformations at the bottom of the heel.

Neck shimming causes deformation: Proven?

No. Two sparrows do not make a summer.

These aren’t the only sparrows I’ve seen though. I will try get better at documenting things when this happens and I might try an experiment too.

However, I’m convinced enough that I will keep warning against shimming the lazy/easy way, with a bit of card at the end of the neck pocket.

The right way to shim a neck

Full-pocket, tapered shims.

A wedge-shaped bit of wood that fills all of the surface of the neck pocket. That’s the way to do it.

You can make one (if you’re patient and vaguely masochistic) or you can buy Stew Mac’s ready made shims. They’re available in 0.25º, 0.5º, and 1º tapers and you can get them for guitar, bass, and as ‘blanks’ for odd shaped necks. Most of the time, the 0.25º will the the trick. I’ve had people tell me they think these are expensive for a thin bit of wood but I have a feeling those people have never made their own shim. 😉 They’re certainly cheaper than the time it would take me to make one. Also, these shims are a hell of a lot cheaper than the fret level or refret they can help prevent.

Please go get one if you need to shim. Please don't stick a piece of card under the end of the neck. Please don’t use Fender’s oh-so-handy Micro Tilt shimming/adjustment mechanism. Buy a full-pocket, tapered shim.

Will this mean your guitar will never ever develop a ski jump? Nope. But it will drastically reduce the chances of that happening.

Who wouldn’t want that?

Filed under ‘Stuff That Annoys Gerry: Shims and Ski Jumps’

LINKS

How to shim a bolt-on neck

The perils of bad neck shims

Neck shimming made easy

Offset Fenders: Curing Buzzes and Rattles