# Instruments and Equipment > Videos, Pictures & Sound Files >  Jacobson Carbon Fiber Mandolin Prototype

## Marty Jacobson

Hello everyone. Here's a prototype carbon fiber mandolin I just finished. I think it came out great, considering I have no idea what I am doing when it comes to composites. There are some obvious flaws in this instrument, but I have learned the value of not worrying about aesthetics on a prototype.

I was concerned that it would feel cheap and plasticky, but once I got some varnish on it, it just felt like a mandolin. It sounds better than I had any right to expect it to sound.

The top is simple, with the reinforcement layers arranged so there is no need for bracing. The resulting top plate tapped and sounded a lot like a wood plate. 
It is loud and responsive in tone. I think it is one of the best mandolins I've made to date. 

The manufacturing process is surprisingly simple. There's a top and there's a back. You put 'em together. You get a mandolin. More luthiers should work with carbon fiber. It is a very inspiring material.

Will try to record a sound sample once the boys are in bed.

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billhay4, 

Charles E., 

choctaw61, 

citeog, 

dang, 

darrylicshon, 

Don Grieser, 

EdHanrahan, 

Gregory Tidwell, 

Jake Wildwood, 

Jesse Kinman, 

JEStanek, 

Jim Garber, 

Joey Anchors, 

John MacPhee, 

Matt Harris, 

mjb128wv, 

Northwest Steve, 

Paul Kotapish, 

Pete Jenner, 

rdfmando14, 

Rush Burkhardt, 

soliver, 

Steve-o, 

Tom Haywood, 

tom.gibson

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## Steve Sorensen

Wow!  Really attractive design.
Steve

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Marty Jacobson

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## Nathan Kellstadt

Very cool. It will be interesting to see where you, in particular, take this. 

Are zero-frets standard on your instruments, Marty?

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## Marty Jacobson

> Very cool. It will be interesting to see where you, in particular, take this. 
> 
> Are zero-frets standard on your instruments, Marty?


Thanks! Yes, zero frets are standard for me. If you think about it, a hand-cut nut slot is always going to be ever so slightly too high. The likelihood that you can actually cut a nut slot to within 25-30 microns to get optimal action is unlikely, you'll probably stop slightly high or, in the quest to get it optimal, cut it too low. With the zero fret, it's just there. Of course you lose the ability to experiment with magical nut materials which will make your mandolin sound better (sarcasm), but I think it's worth it to have guaranteed optimal action at the nut.

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Jake Wildwood, 

Jesse Kinman, 

JEStanek, 

mjb128wv, 

Nathan Kellstadt

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## Graham McDonald

Very tasty!. You coming to the GAL next month, and bringing that with you?

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## dan in va

i'm seriously wondering how an oval hole designed top would sound in CF.  Maybe it would bring some warmer overtones.  Good mandolins have come and gone and i've decided to keep only one, a Stanley A5s (not counting the O18T set up as a 4 string octave mandolin).  But there are 2 more i would like to have if they sounded good: a tater bug and carbon fiber oval hole.  Since there isn't much action on these last 2, the A5 may always be lonesome.

Marty, i hope you keep building with CF and refine an oval hole design.  Thanks for the post and pics.  Looking forward to the sound clip.

Nice tuning machines, too.

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## Skip Kelley

Marty, that is so cool!

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Marty Jacobson

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## Marty Jacobson

Graham, I will be in the Seattle/Tacoma area visiting Bill Hay during some of the conference. I hope we can get together at some point. I will have this with me. 

Dan, I will build more and I'm partial to oval-hole mandolins, so there will probably be some of those at some point.

Here are some sound samples. It has a lot of volume and doesn't break up when I was hitting it as hard as I could, it just keeps giving. Plenty of depth and sustain for more mellow pieces, too. 





A couple more are on my SoundCloud if you click through.

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Astro, 

Cary Fagan, 

ccravens, 

Don Grieser, 

Jesse Kinman, 

JEStanek, 

Jim Garber, 

Matt Harris, 

rdfmando14, 

Rush Burkhardt, 

soliver, 

Steve-o, 

tom.gibson

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## Tom Haywood

Wow! Outstanding sound, Marty.

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Marty Jacobson

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## Don Grieser

Very cool in every way. I want one! Outstanding work, Marty!

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Marty Jacobson

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## Ron McMillan

Superb work, Marty. I am certain that there is a market for quality CF mandolins. Best of luck with this new line.

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Marty Jacobson

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## multidon

Very interesting. What kind of fretboard? Ebony? I always wondered why makers who do carbon fiber don't do Richlite or some such. Looks like there's still wood in the headstock. Any way to eliminate that? Also, it would appear you subscribe to the theory that a carbon fiber neck doesn't need an adjustable truss rod. I'm not convinced.

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## Ted Eschliman

Fantastic!

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Marty Jacobson

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## Marty Jacobson

> Very interesting. What kind of fretboard? Ebony? I always wondered why makers who do carbon fiber don't do Richlite or some such. Looks like there's still wood in the headstock. Any way to eliminate that? Also, it would appear you subscribe to the theory that a carbon fiber neck doesn't need an adjustable truss rod. I'm not convinced.


Hi Don, the fretboard and tailpiece frame are industrial waterproof micarta, kind of like Richlite on steroids. It's commonly used as a knife handle material for extreme environments. The only problem I had working with it is that it is so tough, I should have cut wider fret slots, and ended up with a pretty extreme compression situation in the fretboard. So I'll cut .028" fret slots next time instead of the usual .023" I do for wood. 
There is wood in the headstock, I really like the way it looks and I will probably keep it as standard. I don't think it's a problem, since it's encapsulated in epoxy, kind of like a canoe paddle. But the wood could be acrylic stabilized in the future, or other materials like garolite or aluminum could be used if the customer desires.

The bridge is one of my normal wood bridges, which I used because I had some made up. I will probably engineer a super low mass aluminum and carbon fiber bridge for these in the future.
I'm also thinking of making an integral, epoxied-on bridge base which will really help to make this instrument low maintenance and tough.

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Astro

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## Tom Haywood

I'll jump in briefly to say I looked it over pretty thoroughly before the fret board was fretted and installed. I was immediately curious about the neck strength with no truss rod design. What was most impressive was that Marty experimented with different layering orientations of the material and came up with something that is extremely strong yet has some flexibility similar to wood. For the neck, the combination of this material pattern and the micarta fret board appeared to be far stronger than any solid neck I've seen. With very little weight. So, I'm curious now whether any relief resulted or how to build that in to it if any relief is necessary.

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rdfmando14

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## Steve Sorensen

Marty,

Thank you for posing such a range of tunes for the recordings.  Very impressive results right out of the gate!

Again, impressive!  Congratulations!

Steve

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## Jake Wildwood

Folks, we have a winner!!! It's hard to make CF shine.

I roll my eyes at CF instruments until I hear ones I like well enough. This thing sounds awesome and looks killer, too! I love new materials when they're used correctly. I hate to say it, but my standard guitar that's hauled to gigs is a lam-top Gibson from the '80s... for the reason that it sounds just fine and is stable as heck.

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Marty Jacobson, 

rdfmando14

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## Marty Jacobson

> Thank you for posing such a range of tunes for the recordings.  Very impressive results right out of the gate!


Yes, I definitely got lucky. I hoped to get a good starting point, but I didn't expect to get to this point without several more iterations. I will be posting the "recipe" for anyone who wants to do something similar, so they have a starting point as well.

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## Marty Jacobson

> I'll jump in briefly to say I looked it over pretty thoroughly before the fret board was fretted and installed. I was immediately curious about the neck strength with no truss rod design. What was most impressive was that Marty experimented with different layering orientations of the material and came up with something that is extremely strong yet has some flexibility similar to wood. For the neck, the combination of this material pattern and the micarta fret board appeared to be far stronger than any solid neck I've seen. With very little weight. So, I'm curious now whether any relief resulted or how to build that in to it if any relief is necessary.


Well Tom and Don, as to relief, I got 1mm action at the 12th fret on the E and 1.5mm action on the G without buzzing. I haven't measured the relief because I only care about relief if it's keeping me from getting the action I want. 99% of the time, I adjust truss rods because some instrument owner cluelessly mis-adjusted it thinking they would make things better.
This is without a doubt the stiffest neck I've ever made, and I think that is a good thing, especially in combination with its extremely low mass. Also, there's essentially no way you could break the headstock off of this.

Mmm... think of the possibilities for incorporating an ultra-low-mass "Tone Gard"...

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Tom Haywood

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## dang

So cool!  :Cool: 
And it still looks like a Jacobson, I like you could adapt the material to your style. 
Where's the plug in for the pickup?  :Wink:

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Marty Jacobson

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## soliver

Marty, this is SUPER cool!... it look beautiful and sounds awesome!

Hope I can see it in person sometime!

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Marty Jacobson

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## Astro

Beyond cool.

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Marty Jacobson

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## rdfmando14

I agree.  It's beautiful and sounds awesome!  Good job!  I'm so glad you showed it to Tom, Mark and me last weekend.  Nice to meet you too.  I'll be watching for more from you.

Robin

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Marty Jacobson

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## Dale Ludewig

I love it!

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Marty Jacobson

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## billhay4

Ah, Marty, you strike again. Can't wait to see this one.
Bill

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## Dave Greenspoon

Amazing. Great sounding instrument shown off nicely by some tasteful playing. Loved how the single note articulation sings so sweetly and the chops/double stops want to give a little growl. Any chance this is going to be doable at working-person prices? +1 on the pickup, fwiw.

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## Marty Jacobson

> Amazing. Great sounding instrument shown off nicely by some tasteful playing. Loved how the single note articulation sings so sweetly and the chops/double stops want to give a little growl. Any chance this is going to be doable at working-person prices? +1 on the pickup, fwiw.


I tried selling instruments for working-person prices, but the problem is I wasn't rich enough to keep doing it. Most working people I know have fancy new trucks, so I guess it's all about where you put your priorities.

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Ron McMillan

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## Dave Greenspoon

> I tried selling instruments for working-person prices, but the problem is I wasn't rich enough to keep doing it. Most working people I know have fancy new trucks, so I guess it's all about where you put your priorities.


Trust me, I totally understand how that plays out. All that said, you really came out with an amazing initial effort. Beautifully done, and incredible sounding. Oh well. Maybe one day CA or Rainsong will realize there is tens and tens of dollars to be made in this niche.

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Marty Jacobson

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## Ivan Kelsall

Hi Marty - Very well done indeed !!. I worked in CF composite design & manufacture for over 10 years in the aircraft industry & i know that CF can be a hard material to master - even for simple shapes. It seems that you've got it right first time - maybe a bit of fine tuning (in the manufacture) to eliminate any 'flaws' - terrific work,
                                                                                        Ivan :Wink:

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Marty Jacobson

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## bbcee

Marty, I echo all here - you've made a viable musical instrument from a tricky material (I'm thinking of the first generation of CF guitars-ugh).




> The manufacturing process is surprisingly simple. There's a top and there's a back. You put 'em together. You get a mandolin. More luthiers should work with carbon fiber.


I have little experience working with CF, and that wasn't good, as I had zero idea what I was doing. Splinters & dust everywhere! Do you see building something like this in the realm of possibility for us hobby builders? 

Will you be posting build logs on your site?

Really exciting to see this being done right!

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Marty Jacobson

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## J.Albert

I was wondering how it might sound, but it sounds like, well... a mandolin.   :Smile: 

If I hadn't known it was made out of carbon fiber, and had heard only the sound samples, I would have guessed it was just another "wooden" mandolin model, voiced a little differently...

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## Marty Jacobson

> I have little experience working with CF, and that wasn't good, as I had zero idea what I was doing. Splinters & dust everywhere! Do you see building something like this in the realm of possibility for us hobby builders? 
> 
> Will you be posting build logs on your site?
> 
> Really exciting to see this being done right!


Yes, I will be doing a full build log including moldmaking and "recipes" for duplicating my results. Not until September or October, though, with what I have going on currently. If you have any questions, feel free to ask.

I think working with carbon fiber is actually more accessible than woodworking, since you really don't need all the special bandsaws, chisels, joiners, planes, etc. which are necessary for woodworking (and the associated skills to use them). The only challenge is making the mold. I think if you had a CNC router and a nice flat 4'x8' table to work on, you could have a complete production carbon fiber guitar & mandolin making shop. Of course making the molds is something you could do by hand, and trimming the parts would be possible using just a cutoff wheel on a Dremel (in much the same way that a car is perfectly functional without power steering or air conditioning). But having a CNC machine to make the molds and then to precisely trim the infused parts makes it a dream to work with. It's precisely the kind of process I envisioned developing when starting lutherie - repeatable parts which are as easy to assemble as making sandwiches.

Of course you need to keep safety in mind - a lab coat, safety glasses, nitrile gloves, and a respirator are necessary for all operations where you are cutting or sanding carbon fiber, so it's also necessary when you are just hanging out in the space where you recently cut carbon fiber due to the dust swirling around in the room, whether you can see it or not. But I treat wood dust as hazardous anyway, so it's not that much of a change from what I ordinarily do.

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bbcee, 

darrylicshon

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## tom.gibson

Is there a significant difference in weight from your other mandolins?

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## dan in va

Now you've really gone and dunnit.  There are visions of CF tater bugs dancing in my head.

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## Ron McMillan

> Most working people I know have fancy new trucks, so I guess it's all about where you put your priorities.


Unless you can somehow get the banks to support you by offering five-year payment plans, competing with the truck dealerships is going to be an uphill struggle.

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Marty Jacobson

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## Ivan Kelsall

With the CF materials we used in the aircraft industry - CF cloth for 'wet lay-up' moulding or CF pre-preg.,the biggest problem was in drilling / cutting it. The stuff's hellishly abrasive & can blunt standard drills / cutting tools in minutes. Also,cut edge & the edges of  drilled holes 'feather' so they need sealing with resin to re-consolidate them. Care has to be taken not to apply too much force or  de-lamination can occur at the cut edges as well. 

   In the laying up process,air can get trapped between the layers causing 'voids' ,which over time can expand & cause serious  de-lamination. To prevent that,for smaller items,when using 'female' mould tools (where the lay-up is done inside the mould tool),we had rubber ''intensifier'' plugs made from liquid rubber,cast inside the mould tool. The CF was layed-up in the mould / the intensifier was placed inside it & pressure applied to it to consolidate the lay-up. This was usually done by placing the whole thing inside a plastic vacuum bag & pumping the air out while the lay-up cured,if it was 'cold cure' resin. Our pre-preg CF was usually 'hot-cure' material & required an oven,or in the case of very large items,an Autoclave.

  I don't know if anything like that is either practical or even affordable for CF mandolin production,but it's one way of avoiding 'voids' & the perils thereof,
                                    Ivan :Wink:

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## Marty Jacobson

Hi Ivan, I've been doing wet lay-up and vacuum bagging on female molds. When I did it properly using well designed molds, I didn't have any problems. I definitely need to do a mold-conforming reusable latex or silicone vacuum membrane (or "intensifier" as you put it) to get an acceptable final finish on my back/neck/headstock component, which is the only part on which I encountered issues.

PreciseBits makes a nice carbide burr tool, which when used in CNC, leaves a very clean cut on parallel or perpendicular surfaces. And they are quite cheap, only $3 apiece, so if I have to buy one for every mandolin I am fine with that. The benefit of working on mandolins are that they are nice and small, so the tool life issue isn't too much of a dealbreaker.

Interestingly, I just got this email from RobbJack about a drill tip geometry for working with CFRP:

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Ivan Kelsall

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## Glassweb

Very impressive... the playing, the design of the mandolin, the tone... you've solved the carbon-fiber mandolin puzzle old bean... congrats all the way around!

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Marty Jacobson

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## Marty Jacobson

> Very impressive... the playing, the design of the mandolin, the tone... you've solved the carbon-fiber mandolin puzzle old bean... congrats all the way around!


Still a long way to go, but thanks for the encouragement!

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## Ivan Kelsall

Hi Marty - It seems like you did a bit of homework before you began - well done,so many folk don't.

  Wet lay-up is the way to go in his instance. Pre-preg.is fine for large flat panels. Anything ''with shape'' & it's very messy & difficult to handle. Yank it about too much & the weave can start to get '-un-woven'. As long as the vac-bag goes down nice & evenly inside the female mould,that's fine.The danger is if it starts to wrinkle & causes wrinkles in the inner side of the lay-up. That's one reason why we began to use moulded Silicon rubber intensifier 'plugs'. Added expense but you get a spot on product.

   Our drills were made by a German company, ''Klenk'' (now part of another Co.- 'Ceratizit')* 100% solid carbide* & monstrously expensive,but for cutting high volumes of CF the only ones that would do it. Even then, they were used in rotation - some in use,others being sent back for re-sharpening. They were also 'glass hard'. Drop a 1/2" drill & it would shatter like glass - £150 down the drain !. They were placed back in their foam lined plastic containers after use,& the fitters would go for a long lie down in a dark room, :Grin: 
                           Ivan :Wink:

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## Marty Jacobson

Hi Ivan, yes we have that trouble in the college machine shop I manage. Students come in asking for a new cutter for a project and hand it back in destroyed because they let it slide it out if the collet onto the vise while they were unloading it. I basically just supply crappy HSS tooling and if they want to do actual quality work they can buy their own.

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Ivan Kelsall

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## Jeff Hildreth

Well done Marty, inspirational from a construction and tonal perspective.

Will you pursue this to a viable commercially available unit. ? I hope so.

I'm interested.

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## mandroid

Vacuum bagged the carbon layup at room temperature?

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## j. condino

Cool mandolin....glad you are the one dealing with the CF dust and splinters and not me!

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## Ivan Kelsall

From mandroid - _"Vacuum bagged the carbon layup at room temperature ? "_ Yes - CF can be used with either a cold cure resin or a hot cured resin. Typically, pre-preg. CF is hot cured in an oven (autoclave), which means that for simple shapes,which are also ''structurally simple'',wet lay-up using cold cure Epoxy resing is the most widely used. To warrant the purchase of an autoclave & indeed,pay for the electricity to power it,calls for a lot of expense,something you'd only do if you were into large volume production.

   Many components made from 'Glass fiber' are made by using glass cloth impregnated with wet epoxy resin,vac-bagged & allowed to cure at room temp.. The technique is equally applicable to dry CF materials used with wet resin,
                                                                                                                                    Ivan

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## dschonbrun

Nice job, Marty.

Did you wrap CF around a wood neck, or did you use another type of filler?

Thanks,
D

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## Marty Jacobson

The neck is entirely hollow except for the headstock, which has a maple plug and extends about a half inch past the nut. There is also no neck block, no bracing, and no linings. It's a monocoque construction.

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Dave Greenspoon

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## Ron McMillan

> The neck is entirely hollow except for the headstock, which has a maple plug and extends about a half inch past the nut. There is also no neck block, no bracing, and no linings. It's a monocoque construction.


That's interesting. I always assumed the neck on my Mix was solid. Probably not!

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## billhay4

Marty,
How is such a neck made? Is there a mold or form? IF so, how is it removed?
Thanks,
Bill

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## Marty Jacobson

Hi Bill, it's vacuum bagged onto a female mold. Pretty easy to do once you have a mold. The neck and back are all one piece. 



My process and mold geometry are not perfect here. As Ivan points out, a better process would be to use a form fitting silicone vacuum bag instead of the flat poly film which resulted in wrinkles in the vertical surfaces. But I wasn't sure the structure would even work so I just went ahead with the prototype.

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Ivan Kelsall

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## JEStanek

Wow. It looks and sounds great. I love the sound hole design.  Very aggressive looking that goes well with the CF material.

Jamie

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Marty Jacobson

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## Ivan Kelsall

Marty - You could make a 'sacrificial' lay-up _to your spec._inside the mould tool,& then cast a silicon rubber 'Intensifier plug' inside it. Simply make sure that the surface of the plug is as smooth as it can be. Using the plug,which will 'spread' under vac. pressure,will iron out any wrinkles - in fact,it ''should'' totally prevent any wrinkles occuring. Or - if you're only having any problems with either the body shell or neck,cast a plug for that section only,
                                                                                                                           Ivan

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jmkatcher

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## V70416

Nice work,Marty!

Always wanted a CF mandolin;esp. since I got a vey nice sounding Composite Acoustics guitar(Standard X) that I have owned for a decade
or so. Love it. No worries about leaving it in a hot car etc. Worry-free acoustic instrument.

Well,I do sorta worry about getting it refretted. There is zero organic material/no wood,in the CA guitar(AFAIK).

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## Pete Jenner

Good one Marty.

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Marty Jacobson

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## billhay4

I guess I am having difficulty seeing how this produces a hollow neck.
Bill

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## Marty Jacobson

> I guess I am having difficulty seeing how this produces a hollow neck.
> Bill


Think paper mache stuck to a balloon... But instead of paper and glue, it's fabric and epoxy and the bag pressing the fabric up to the mold.

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Ron McMillan

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## billhay4

Ah, got it. I think.
:-)
Bill

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## amowry

I got to see this mandolin in person when Marty stopped by the shop today. It sounds amazing! Marty's really on to something here.

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## Paul Kotapish

Very impressive! Beautiful design, great sound. Any initial thoughts about production, price point, etc.?

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Pete Braccio

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## Marty Jacobson

Thanks Andrew! I gotta say it looked pretty janky compared to your work, haha.

Paul, I have more R&D to do on this but will be producing more this year. Price point will be $3-4k, most likely.

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Paul Kotapish

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## billhay4

I played this instrument last night. Very nice sound. Marty is working out the bugs in production in his head and I can guarantee it will be beautifully produced. He is as precise as anyone I've ever know except, possibly, Andrew.
I play one of Marty's wood instruments and have yet to find a flaw in it.
Bill

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## CES

That's great to hear, Marty! I'm very interested, and have no doubt you'll get them "right" before you unleash them!

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## j. condino

I was hoping to get in a test drive at the Guild of American Luthier's convention, but  never saw you.....

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## billhay4

Marty didn't make the convention. We took his kids and wife to Mt. St. Helens instead. He was on a tight schedule and only had Wednesday available.
For what it's worth, Mt. St. Helens was great.
Marty is wending his way back to Georgia now. He may have even gone crazy now with three boys, 10, 8 and 6, on a month long drive across country.
You'll know if he went crazy if his next build is a CF banjo.
Bill

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## Jim Garber

> But there are 2 more i would like to have if they sounded good: a tater bug and carbon fiber oval hole.


How about a carbon fiber tater bug with an oval hole? Now you are talking.  :Smile:

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## Don Grieser

Here you go, Jim. http://avastrings.com/neapolitan/

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## Marty Jacobson

> Here you go, Jim. http://avastrings.com/neapolitan/


Very cool, but an even smaller market (and hence ROI) than American-style mandolins.

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Jim Garber

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## j. condino

Bada$$!!!! Darth Vader meets the Godfather; tech that my great grandfather would approve of!

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Jim Garber

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## Jim Garber

> Here you go, Jim. http://avastrings.com/neapolitan/


Yikes. ~$3700 is a bit more than I want to pay. Then again, I don't really want to pay. I have a few excellent bowlbacks. I can't play them in the bathtub but you can't have everything.

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## Bill McCall

> ..........I can't play them in the bathtub but you can't have everything.


You could once

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Jim Garber

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## Dave Bradford

If you would like to hear some fine mandolin playing, check out my first bands version of this song.  (Journeybear is on mando and I’m playing the fiddle part on this one.):  https://youtu.be/VGjKD5p5NX8

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## Jim Garber

Oops! I may have derailed this thread with "Singing in the Bathtub." Now I will have to put in my order with Marty for my CF mandolin. Marty, can you make me a CF bathtub to go with it?

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## Marty Jacobson

Why do you need a CF bathtub, Jim? Just keep it at 45% RH and you're fine with your current wooden one.

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OneChordTrick

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## Jim Garber

You are right. The Florentine bathtub I inherited from Grandpa would do just fine, although those points stick into me at times. Grandma always preferred the three-point.

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