What the Neck ! ? Physics of neck tensions ?

Pentabass · #1 08-01-2008, 10:18 PM

What we have here, is the neck of an older Czech plywood bass, with some previous neck 'repair' - as it would seem a short-cut, if you permit the pun, probably to straighten, or change the angle of the neck.

The give away are the two screws straight through the fingerboard from the front. (There, that should not go anywhere!) Only when the strings were loosened, was it apparent that there is a little seam opening up, where I don't expect it. Would you believe it - no glue, only five screws...

I would like to understand why did this neck was able to take on the tension of the strings at all?

I guess I have to get out the old vector physics drawings, and calculate the tension that those screws were holding.

Why did it not all just come loose? Comments ?

Gearhead43 · #2 08-01-2008, 10:59 PM

It was held on by Mojo.

Andrew McGregor · #3 08-01-2008, 11:12 PM

I can believe it would hold... the screws are under tension, where they're strongest. Still not a good idea.

Jake deVilliers · #4 08-01-2008, 11:57 PM

Its the magic of the violin design. The tension pulls from the nut straight through to the saddle, pulling the heel into the neck block.

**Matthew Tucker** · #5 08-02-2008, 02:42 AM

EEEEEW that's an ugly repair job!

toman · #6 08-02-2008, 05:18 AM

And I thought some of the dowel jobs I've seen were ugly. Man...

Jake deVilliers · #7 08-02-2008, 01:47 PM

People in this part of the world are always putting giant screws into basses; it makes me crazy. I missed some awful ones before I got a digital camera but here's a recent 'victim'.

Two of those screws were a full 5" long.....

Pentabass · #8 08-02-2008, 04:45 PM

Quote:

Originally Posted by Jake deVilliers

People in this part of the world are always putting giant screws into basses; it makes me crazy. I missed some awful ones before I got a digital camera but here's a recent 'victim'.

Two of those screws were a full 5" long.....

Oh, those make mine look like little dwarfs.

I guess, the thinking goes like this: Bigger must be better?

Jake, when you say: "this part of the world" -- does that mean this is a regional phenomen, in your experience?

Jake deVilliers · #9 08-02-2008, 05:19 PM

Yeah, that bass had one 3" and two 5" screws. Bigger is definitely better!

I don't really know if its regional, I've not worked on instruments in a different part of the world, but I've seen several basses that came from Alberta with 'rustic' repairs.

I'd guess that its a rural thing, part of the farmer's 'fix-it' attitude. City dwellers had/have more options. In a way I admire their willingness to make it work - at least the bass was rendered playable once more.

If I was living in the middle of the prairies 50 years ago with no resources, I might have done something similar and you'd be being shocked at my rough and ready repair!

Bob Branstetter · #10 08-02-2008, 08:05 PM

It's certainly not a rural thing Jake and it happens today just like in the past. I've seen it all too often here in the city. Far too many people still look at a doublebass as a carpentry project if one gets broken. Get out the glue or epoxy, the drill and whatever else is laying around in the Garage. Fathers of young bass players are frequent offenders.

forester · #11 08-02-2008, 08:55 PM

pencil lines are a nice touch.

Pentabass · #12 08-02-2008, 09:17 PM

Quote:

Originally Posted by Jake deVilliers

I'd guess that its a rural thing, part of the farmer's 'fix-it' attitude. City dwellers had/have more options. In a way I admire their willingness to make it work - at least the bass was rendered playable once more.

If I was living in the middle of the prairies 50 years ago with no resources, I might have done something similar and you'd be being shocked at my rough and ready repair!

Lets pursue that image of 'fix-it' farmer in the middle of the prairies...
and explore our current options. A few 'space age solutions' might seem to present themselves.

After I have done my vector analysis, having come to the realization that I would like to see a little more than just these screws and nothing else to keep this 'decapitated neck' (shudder) in position, I present as solutions:

1. Steel cables. I have surplus, because Princess Auto sells 50 feet at a time, and I only need a short little bit for the tailpiece. What about a steel cable loop, lets say going through two of the current vertical screw holes, all the way through the bass to the other block near the endpin? I could tighten this loop, like the old saws, with an old soundpost, inside the bass! Anybody seen this intersting solution with a totally new set of buzz generation possiblities? Not to mention the effects on the sound. All string property spreadsheets might have to be redone, with this amazing modification in place.
In the simple version, there could be a single steel cable, from the scroll, to the tailpin, but at the back of the bass. A sure cure for any sagging neck. Playabitliy? Well, you know, people get used to many things, and a steel cable digging into your armpit is not the end of the world...

2. High tech fiber re-enforced epoxy resins. What about a neat little 'neck cloth' - a clothing piece, as it were, draped and epoxied to the top around the neck, covering an area bigger than the top block? Surely the sound implications would be minimal? Externally applied out of lovingly applied layers of S-glass, maybe even some carbon cloth? Here we could implement the 'dress your bass' concept, from a nice little lace collar all the way to the 'belt and suspenders' external fibre-glass re-enforcements. You like my "Lederhosen Bass"? I mean, the slapbass decorators seem to come out of the relative stereotype hotrod garages. Comon, there is a whole world of functional fibreglass braces, in the form of decorative clothing, out there!

3. Screw matching slide rails to the matching surfaces, and presto, we have a detachable neck. Practical for transport. Gives you lots of tuning experience. Maybe the neck was really meant to be off there? Again, have the possibilities of the impact of a detachable neck on tone really been examined in a double blind, randomized trial? Where is the evidence, I ask you?

I am running out of steam. Maybe the esteemed members of the this forum have some other suggestions. I am open for down to earth, practical solutions, as you see.

Even wooden dowels have some merit, I understand.

Jake deVilliers · #13 08-02-2008, 09:48 PM

Just epoxy it back together, then run some dowels in to join the two pieces of the heel back up and viola, you're playing again!

Two or three 3/8 or 1/2" maple/birch dowels where your 3 screws are now will help to provide mechanical resistance to any slippage, the epoxy (real 24 hour epoxy with no fillers) will do everything else.

Pentabass · #14 08-03-2008, 08:24 PM

And thank you, Jake, for encouraging the Right Way.

I tried hard, but hardly a smile could be drawn from the esteemed participants.

Jake deVilliers · #15 08-04-2008, 01:18 AM

Well, its not really The Right Way - The Right Way would be to carve a & fit a new neck.

Its more like The Expedient Way or The Good Enough Way but it will restore the bass to playability and that's the main thing, isn't it?

Bob Branstetter · #16 08-04-2008, 09:06 AM

Quote:

Originally Posted by Jake deVilliers

Well, its not really The Right Way - The Right Way would be to carve a & fit a new neck.

The Right Way would be a neck graft unless the scroll has been mutilated.

Pentabass · #17 08-04-2008, 09:12 AM

Quote:

Originally Posted by Jake deVilliers

Well, its not really The Right Way - The Right Way would be to carve a & fit a new neck.

Its more like The Expedient Way or The Good Enough Way but it will restore the bass to playability and that's the main thing, isn't it?

Thank you for thought provoking question, Jake!

Yes, is Playability the main thing or the ultimate goal for me?
In that case, why did I acquire a project bass, and not a completely fitted , ready to play instrument? (the ultimate shortcut to playability, as it were). And why did I have to poke around those expoxy covered screw holes?? The bass was playable, before I started to 'explore' the neck, after all.

I am starting to become unsure about Playability being my main goal, since it would appear that the only Right Way to reach that would be a complete rebuild of this bass, and any other way to reach that goal have the semblance of those Good Enough ShortCuts. It is although I will always have that lingering feeling of: it has not been done right, this bass is not 'Good'. And it could take the very real dangerous form of snapping necks and flying tailpieces.

Yes, I realize now that there is another goal, and that is that I want to understand the bass. I want to be able to fix and rebuild it, so that I know it has been done right.

Thank you again, Jake, for helping me to define clearer for myself what 'right' would mean - where is the 'good enough' point?

I have come to the right place, it would seem.

Jake deVilliers · #18 08-04-2008, 12:42 PM

"The Right Way would be a neck graft unless the scroll has been mutilated.

"

Thanks Bob, I was making an unwarranted assumption..... Would you just graft on a new heel?

Bob Branstetter · #19 08-04-2008, 01:13 PM

Quote:

Originally Posted by Jake deVilliers

"The Right Way would be a neck graft unless the scroll has been mutilated.

"
Thanks Bob, I was making an unwarranted assumption..... Would you just graft on a new heel?

No, I'm referring the traditional method of grafting a new neck (handle and heel) to the scroll. It's not quite as common on basses, but just about every violin from the classic Cremona period (Stradivarius, Guanerius, Amati, etc.) has had a new neck grafted to the original scroll at some time in the past. It's one of those procedures that separates the men from the boys in violin family luthiery.

Pentabass · #20 08-04-2008, 06:54 PM

Oh, yes, that I have seen on a violon and cello. The heel and the neck are replaced, but there is a nifty joint that sort of 'slides' into the tuning box / scroll area. You have to look closely at the back of the top of the neck. This was done when the lower tension, and lower angle of the Baroque violins/cellos, were changed by a higher bridge and steel/metal strings in place of gut. This needs an adjustment of the neck angle. The resulting stronger tone became popular, especially in the solo and orchestral environment, until the rediscovery of the baroque angles, for smaller ensemble work, so now you can refit your instrument to the original lower angles.

This begs the question: have any double bass players, those that love the gut, lowered their bridges and neck angle? Sure you would loose some volume, but what are these pickups and amps for anyway?