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Winter 2019 Build Off - the EUV

#81
Pegbox basically done, save for shaping the volute and general cleanup sanding.

EUV_0284.jpg


Drilling the tuner holes was a bit of a pain, as the bushings are actually somewhere between 5/8” and 11/16”, and I don’t have anything in between. Rather than drilling the larger size and having a loose fit, I drilled the smaller size and opened the holes up a bit from there. I used a small round file for the first one, which was time-consuming and approximate. I fiddled with a few other methods, then figured out how to wrap some 60 grit sandpaper around my 5/8” Forstner bit, which gave much better results much more quickly. :thumbsup:

Decision time: truss rod or no? I’m 98% leaning towards no rod, for several reasons: Acoustic double basses don’t use them, and the maple neck is quite dense and hard, and the combined thickness of the maple neck and ebony fingerboard is going to be considerable. Frankly I can’t imagine this bending much at all. But I’m ready to glue the fingerboard down, as early as tomorrow, so I thought I’d solicit a few last-minute opinions from the collective mind. What say you?
 
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#83
ctmullins said:
Pegbox basically done, save for shaping the volute and general cleanup sanding.

View attachment 3329114

Drilling the tuner holes was a bit of a pain, as the bushings are actually somewhere between 5/8” and 11/16”, and I don’t have anything in between. Rather than drilling the larger size and having a loose fit, I drilled the smaller size and opened the holes up a bit from there. I used a small round file for the first one, which was time-consuming and approximate. I fiddled with a few other methods, then figured out how to wrap some 60 grit sandpaper around my 5/8” Forstner bit, which gave much better results much more quickly. :thumbsup:

Decision time: truss rod or no? I’m 98% leaning towards no rod, for several reasons: Acoustic double basses don’t use them, and the maple neck is quite dense and hard, and the combined thickness of the maple neck and ebony fingerboard is going to be considerable. Frankly I can’t imagine this bending much at all. But I’m ready to glue the fingerboard down, as early as tomorrow, so I thought I’d solicit a few last-minute opinions from the collective mind. What say you?
Click to expand...

I didn't use a tr in my cello/bass - after all, uprights don't have them.
 
#88
I wouldn't think of it as "cf instead of truss rod" because it strikes me that they solve different problems. CF would help with stiffness. I don't think stiffness is going to be an issue with the neck so thick in cross section. To me, the advantage of a truss rod is in adjustability, in case the neck moves with changing conditions. More stiffness would prevent the movement to an extent, but if a long piece of flatsawn maple wants to be a slightly different shape, I don't think a ribbon of carbon is going to stop it.

Personally, on a neck this long, I would put a truss rod in it. But I'm not an experienced instrument maker. The fact that upright double basses don't have truss rods has me curious about how they deal with movement. Do people just adjust the bridge and/or retune? And "deal" with the slightly different action? Do the necks really not move - because of the lamination to the thick fingerboard and/or laminations in the neck itself?
 
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#90
Dadagoboi said:
Ya feelin' lucky?:)
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I am, actually, and that's probably the problem here. I'm old enough to be well acquainted with Mr Murphy and his wife Prudence. Those of you advocating for a rod "just in case" are being sensible.

On the other hand, I'll be ticked if I install a rod and wind up not needing it...
 
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#92
I was a little worried that 2 cf rods + a TR would be TOO stiff. But it hasn’t been the case. Both necks built that way seem easily adjustable, and they stay where you set them. I don’t really know which of the elements, including the maple itself, is most important, or a combination of all of it.
 
#93
Jon Clegg said:
I'd vote for cheap insurance. BTW did you get any of the CF TOW from last year? A CF TOW strap under a maple plug might be a good compromise. @T_Bone_TL , any thoughts?
Click to expand...

I think the only entrants from last year that didn't get CF were ones out of the USA with super-expensive postage, so @ctmullins should have 10 meters of so of 24K TOW somewhere. I'd put some TOW in, being a firm subscriber to the church of Murphy; I doubt I'd bother with a TR, since the CF should make it extra-stable along with the normal stability of the thick-section URB type neck, and the "normal" way to make relief adjustments on a URB is shaving the fingerboard, so if you need to adjust, you do that, but from a point of "belt and suspenders" neck stability.

But I AM the monk at the airport handing out bouquets of pretty shiny black CF flowers ;-)
 
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#94
T_Bone_TL said:
@ctmullins should have 10 meters of so of 24K TOW somewhere.
Click to expand...

17 meters, yes, thanks! I didn't even know what it was when I got it, having not paid attention to that thread last year. But it's safely tucked away, and perhaps this is the build for it...

I'd put some TOW in, being a firm subscriber to the church of Murphy; I doubt I'd bother with a TR, since the CF should make it extra-stable along with the normal stability of the thick-section URB type neck, and the "normal" way to make relief adjustments on a URB is shaving the fingerboard, so if you need to adjust, you do that, but from a point of "belt and suspenders" neck stability.
Click to expand...

There's the voice of reason again! :thumbsup: Guess I'll have to go spend an hour reading through that thread and figuring out if it's something I want to embark on.

But I AM the monk at the airport handing out bouquets of pretty shiny black CF flowers ;-)
Click to expand...

Knew I'd seen you somewhere!
 
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#95
Okay, now I'm seriously considering the CF TOW. Can anybody give me the kindergarten "for Dummies" answer to what kind of epoxy I need? Preferably something that can be locally sourced, perhaps from one of the US "big box" home stores?

I skimmed some of last year's threads, and I saw West Systems recommended, but they have forty different combinations of ingredients. :dead::(:help::nailbiting:
 
#96
The trick with cf tow is getting a good carbon:resin ratio and getting good adhesion of the carbon to your substrate. Basically, as the composite is flexed, the bond and the extra resin deform to take up slack until the carbon comes under load. Resin is not very stiff at all, so until the carbon comes into play, it'll probably be weaker than a solid wood neck. If you have a lot of resin and/or a poor substrate bond, the result is that the carbon won't do much or anything until the neck is deformed beyond the degree of movement we care about - the neck may be able to move a significant amount without the carbon even coming into play. We don't care what the neck does when it's deflected half an inch under load, we just want to stop the first few hundredths of an inch of movement, which means we need to ensure good utilization.

I know others have discussed technique elsewhere but if I were to use tow in a neck, I would route a deep channel to get it near the back of the neck, then lay in the tow and epoxy, and then immediately clamp a filler strip of maple into the channel, with the strip tall enough that it stood proud of the neck surface - this way, you can ensure clamp pressure is compacting the carbon and forcing extra resin out and ensuring good adhesion. Then you can plane the maple flush with the neck surface or cut a truss rod channel into it.
 
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#97
You won't find good epoxy at big box stores. A boat store is probably a better bet if you live near a body of water.

For west systems products, I would use 105 resin with 205 or 206 hardener. Probably 205 since this is a small project.

There are other brands that are cheaper and just as suitable, but west systems has the brand name reputation. I've used 8 or 10 gallons of us composites.com's house brand and would not hesitate to use it for this.

Read up, practice on scrap, watch some videos if you're not used to composites. Make sure you are measuring accurately and mixing well (without introducing too much air). It's not hard work but it is a bit different than working with other materials.
 
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#98
Another note on technique. I would lay the tow on a long sheet of wax paper and wet it out with epoxy using a squeegee or plastic scraper. This way you can control the amount of resin that ends up in the neck a little better vs glooping it directly into the channel. Squeegee from one end to the other to ensure it is wet and not over saturated then lift it into the channel and work it to the bottom using the same squeegee. Then clamp as described above.
 
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#99
In West Systems, your best bet as a small-time user MAY be to get the smallest containers of 207 hardener and 105 resin, which are most easily consumer-available at West Marine boat stores.

Why? Reputedly, and by at least one published report I've found, the stuff does NOT go bad while you await your next project. It costs more at the time you buy it than the 205 or 206 hardeners, but you save money when you don't have to throw it away.

Don't bother buying the pumps, they dispense too much for most small jobs. I use a couple of "oral dosing syringes" from the Vet (don't take a needle, not restricted) as my precision measuring devices, and keep them in separate yogurt tubs for the hardener and resin. Eventually the rubber gets weird and I need a new one. You can also dispense by weight with a precision scale (postal, for example.) Bruuuuce scoops with kitchen measuring spoons. There are many methods. I also make use of epoxy applicator syringes at times, which do take a (blunt) needle and are also not restricted (they are glue applicators, not medical devices) as I use them in fiber optic connector work, so I have them around - but they are quite small (3ml or just over half a teaspoon) and more used for getting mixed epoxy into small spaces than as mix measuring devices.

I use a different brand of epoxy from the Crazy Eddie of epoxy (progressive epoxy polymers - their website is insaaaane, in the "hard to navigate and look at without eyes bleeding" manner), but it's also a "no-blush" product (which 207 is, and 205/6 are not) and my personal stock is still working fine and not pink more than a decade out. The published report regarding West 207 was also more than a decade from buying it.

If you are not opposed to the look of a skunk stripe, a shallow back-opening channel and skunk stripe strip to cover it is a good way to get fiber where it needs to be without having to do deep channels.
 
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#100
Great info, thanks!

What about doing a skunk stripe on the back, filled with TOW and epoxy, but without the wood strip on top? With clear epoxy, it might look interesting. Would that compromise functionality or practicality though?
 

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