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149 posts
since 5/25/10

05/18/2017 21:54:34 View jamesinkster's Photo Albums Reply with Quote

I'm building a couple one-piece necks out of curly maple, which makes me nervous stability-wise. 

Typically I'd laminate two halves, but ... anyway.


I've seen solutions utilizing two pieces of carbon, on either side of a truss rod (namely, Ken LeVan's...). This is what I figured I'd do.

I've routed my truss slot, but now that I'm about to route slots for the carbon (adjacent to the truss, with about 1/8" of wood between the truss and the carbon) I'm nervous about how little wood I'll be leaving in the neck.

Truss rod is .25" wide. Each carbon fibre strip is .125" wide, plus two more .125" wood strips between them.

That means the entire assembly will be .75" wide.

The carbon fibre strips are .325" high, so .375" out from the centre we'll have carbon down .375" deep. That doesn't seem to leave a lot of meat if I need to do a V neck profile...


What if I routed my channel .5" wide and sandwiched carbon + truss + carbon. Would that work?

Additionally/alternately, how about just one carbon strip and a truss rod?


Input appreciated!

mike gregory

United States
45168 posts since 12/14/05

05/19/2017 04:38:38View mike gregory's MP3 Archive View mike gregory's Photo Albums View mike gregory's Blog Reply with Quote

Wish I could be of ANY help at all, but, I cobble together banjos & ukes from whatever junk is available, and the mathematics of wood ( or the math of ANYTHING) was never my strong suit.

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Banner Blue

United States
77 posts since 5/29/15

05/19/2017 04:46:37 Reply with Quote

The only person who would know with any certainty how to do this is someone who made bunches of necks with curly maple, assembled them  with varying combinations of truss rods and carbon fiber inserts (and none at all), then monitored them for 20+ years to see how they held up. 

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United States
154 posts since 11/3/16

05/19/2017 06:04:50 View heavy5's Photo Albums Reply with Quote

I've used various forms of carbon constructing giant scale RC planes and it is very effective when laminated with balsa , foam , fiberglass etc .One of the most important steps is how you adhere it to its mating surfaces IE a quality grade fiberglass .
That's where it gets expensive as aircraft grade​ fiber glass is not cheap . Lesser grades will over time become brittle .

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United States
2743 posts since 5/12/10

05/19/2017 08:50:43View OldPappy's MP3 Archive View OldPappy's Photo Albums View OldPappy's Blog Reply with Quote

I just put in the fiber rods, usually 2 of them 1/8" X 3/8". I cut the channels for these on the table saw with about 1/4" between them. I have a saw blade that I had the teeth set on so that it cuts the channel just wide enough for the rods to slip in with room to have good bonding with the expoxy.

Others disagree, but I see no need to adjust a neck that is right to start with and not likely to change.

I also do not like to cut a 1/4" channel in the neck that leaves it hollow, and weak all the way through the transition to the peghead. I much prefer having two carbon fiber rods extending into that weak area over hollowing it out and making it even weaker.   

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United States
2743 posts since 5/12/10

05/19/2017 08:52:03View OldPappy's MP3 Archive View OldPappy's Photo Albums View OldPappy's Blog Reply with Quote

Just finished a curly maple banjo last week, and have built several over the years. None have had any problem with twisting or bowing, and are solid as a rock.

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