The case against scroll "strengtheners"

[Philphool]

The sensible thing would be to simply route a line where the scroll is without going all the way through but nobody is going to buy that as an option
Too much like the lump scroll Gibsons.

Yep. I've advocated this plan for years. Threw it out to several luthiers, but no bites yet!

[dennador]

I am a first time mandolin builder, and what i am going to do is route a trench where the scroll breaks, and inlay one or two rectangular steel tubes from home depot, along with a healthy dose of 3200 psi epoxy. that might hold it all together.

[sunburst]

Could it be that the biscuit expanded more than the headstock, or that the headstock shrank
more than the biscuit and caused the original break?

It must have all fit together when originally built.

A drop because of the end pin pulling out was the direct cause of the break, but the different grain direction, and the shrinkage of the wood of the head stock is most likely the reason it wouldn't fit back together. Wood shrinks and swells measurably across the grain with changes in moisture content, but shrinks and swells so little in the direction of the grain as to be negligible. With that knowledge, it's hard not to assume that a cross-grain biscuit may have contributed to some scroll breaks, and it's hard not to assume that the biscuit in this one will not stress this glue joint when changes in relative humidity cause changes in the moisture content of the peghead.
The mandolin left here yesterday in the hands of it's owner who said he'll bring it back next time something hits the scroll hard enough to break it again.

[Ivan Kelsall]

Dennador - That won't work very well (IMHO). You'd simply be substituting a couple of pieces of metal for the wooden 'biscuit' placed under the front veneer.The main headstock material needs to be intact or you've already weakened it. Just glueing in 2 pieces of metal under the front veneer,still means that given a hard enough knock from front to back,the chances are that the glue & tubes would pop out through the top veneer in the same way the wooden biscuit did. Any reinforcing needs to be surrounded by the 'parent wood' of the headstock & that can only be done by routing a channel from the top,down into the headstock & then glueing in a strip of 'another' stronger material - or- drilling in from the side of the scroll, & putting in a piece of strong wooden dowel,or a tube or rod of a suitable material. The headstocks on my Mandolins are 5/8" thick for the Lebeda & a tad under for the Weber. That means that if i reinforced the headstock scroll with a pice of 3/16" dia.rod or tube inserted from the side,the reinforcing piece would be covered by 7/32" thickness of wood front & back,thus keeping much of the headstock's original strength,but now reinforced by 'whatever'. Easier said than done,unless you have the tooling for it,but better than burying the reinforcing under a veneer only 1/32" or so thick.- - again IMHO,
Ivan

[JEStanek]

Hey John, On the plus side, this design flaw (maybe even the inherent weakness of the headstick shape) can keep you in repairs and new shoes for a while! There will always be another scroll to fix.

Jamie

[oldwave maker]

Thanks for the clear pictures, John. My 'Earl the pearl Monroe' disturbed master model solves the strengthening problem by pre-breaking the headstock scroll and reattaching slightly out of line the cowboy way, with a vintage prewar rusty horseshoe nail and duct tape.

[sunburst]

Perfect! Did you clinch the horseshoe nail at the back of the peghead? If not, that would be a nice touch on the next one.

That's why I build 'em, Jamie... job security!

[MikeEdgerton]

I've never seen one of these where it was the strengthener that broke. Unless someone else has then I'd say the material that the strengthener is made out of isn't necessarily the issue, although I guess it could be.

[sunburst]

I've never seen one of these where it was the strengthener that broke. Unless someone else has then I'd say the material that the strengthener is made out of isn't necessarily the issue, although I guess it could be.

I've seen several broken "strengtheners". When that happens, we're faced with a jagged, cross-grain fracture that won't fit back together. I remember one with some kind of fiber-like biscuit, very much like those construction biscuits that people use for cabinets and such, with a "biscuit jointer". That was pretty nasty.

[MikeEdgerton]

Biscuits are compressed and made to expand with the moisture of the glue. I do have one of those that I use on cabinets and such. That would really suck.

[Bertram Henze]

This is really a Christmas topic...

[MikeEdgerton]

I think I got my first one as a Christmas gift many years ago.

[thistle3585]

My mandolin #6 should be coming back in sometime to have the scroll glued back on for the third time. There's no "strengthener" in there, so it will be pretty straight forward (again), and eventually it will probably collide with a guitar peghead on stage and get knocked off again. There's nothing I can do about that, but I can make it easier on myself when the time comes to glue it again.

John,
The third time? I think there needs to be some sort of intervention and/or counseling. Maybe that mandolin needs to go to a foster home until we know its safe to go back home.

[Spruce]

Maybe that mandolin needs to go to a foster home until we know its safe to go back home.

Or....
If Bill is so damn influential, just leave it off...
Right Pete? ;-)

[sunburst]

John,
The third time? I think there needs to be some sort of intervention and/or counseling. Maybe that mandolin needs to go to a foster home until we know its safe to go back home.

That mandolin gets some serious playing time. It has collided with other pegheads, mike stands, other stage obstacles so many times... it's just a matter of time when an instrument gets use that much.

[sunburst]

So, they don't always break at the scroll. It's just coincidence that this other F2 was in the shop at the same time as the one with the broken scroll, but since I made the decision to replace the headstock veneer I though some people might like to see what exactly it is we're talking about here. It's not often that these things see the light of day, after all.

[foldedpath]

Ya'll are missing the obvious solution for a strengthener. Just cut a matching slot in the broken pieces and insert a large triangular 2mm Blue Chip pick as your biscuit. Whatever that stuff is, it will be the last thing to break on the instrument!


New construction, just rout a shallow bed for a Blue Chip at the potential break line, and hide it under the veneer.

[Ivan Kelsall]

There's twice as much of the 'biscuit' glued to the part of the scroll that actually breaks. A hard knock on that part & the biscuit will pop out as it did on the one that John repaired,& a thin veneer isn't going to save it.The scroll will (probably) break at the joint & 'take the biscuit' with it.To me that lends a good deal of support for Rob Grant's idea of a thicker front veneer & a corresponding one on the back of the headstock. The grain of each veneer could be orientated so as to form a virtual
'cross-ply',
Ivan

[tree]

I'm going with either the Oldwave look, or the WSM pocketknife look. Both are pretty effective, to my eye. Maybe a little random hippie sanding also.

And, I've decided my New Year's resolutions for 2012 are 1) to try to have as much fun in my life as Bill Bussman, and 2) to learn as much as possible from John Hamlett's excellent photographs and posts.

[BradKlein]

I had no idea that the inlaid scroll strengthening disc had such a long history at Gibson!

[Rob Grant]

Here's what I do with that F style peghead "ear" to keep it from doing a Vincent van Gogh under a pretty heavy blow <g>...

This is the wife's F4 in the attached photo. This headstock scroll has copped a lot of abuse over the years and it's never parted company. On this instrument The top and back veneers are 2.5mm Australian ebony. On most instruments that I have an ebony fretboard I'll lay down 2.5mm Ebony on the peghead face with a 2.5mm slice of Cooktown Ironwood on the back. With a Cooktown Ironwood board I reverse the arrangement. This is a hell of a lot easier and possibly stronger then the Gibson "biscuit" method. Of course, the three-piece neck laminate (centre strip of red Cooktown Ironwood, just visible at the peghead point to the right) between the veneer slices is thinned accordingly to accept the tuner post's length.

[Ivan Kelsall]

Rob - Sometimes the most simple ideas get overlooked for more complex ones. Maybe it's just the 'tradition' to have a single front veneer on a Mandolin headstock,but i'd go with your idea of a substantial veneer front & back, & it looks great as well,something i'd opt for to 'save my scroll',
Ivan

[Rob Grant]

The main problem that most builders would have with my technique is the availiability of thicker "fancy" veneers. I think standard veneer sheets taken off an "exotic" peeler log are usually a little over a half a mm thick.

Oz has some pretty incredible hardwoods that are excellent for veneers, Some of the best are not far from my front door. My trusty 'ol '49 Kalamazoo Atlas bandsaw with a freshly sharpened blade can easily thin slice a hardwood flitch to any thickness I so desire.

[Fretbear]

Gibson did sometimes employ laminated front veneers of (dyed) black pearwood and holly and back overlays as well, the back one just as likely to hide the peghead glue joints as for any other reason. I am assuming they would have had to have been thicker and stronger like what Rob is using if they were to have effectively been of aid in preventing the occasional scroll-cracking.

[Dale Ludewig]

It would be a pain to do, but (depending on the finish color) if you were going to put some veneer on the backside also, the problem could probably be eliminated by half-lapping some material for the scroll. As is, it breaks off on the grain line. You'd have to laminate the back side because no one would want to see the joint work.