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8 string acoustic


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Time to get the new year off to a sensible start an dve back into acoustic buiding. Most of of the builds on here eems to be electric, so not 100% sure this best suited here. I'll ramble on if you guys don't mind and would also appreciate somone shouting at me about any glaring boo boo's.

I'd fogotten how many jigs and templates this takes. First off was a mold. 3x 18mm sheets thick. I also managed to get a set of binding cauls and a form wide enough to set up some sort of simplified fox bende if hand bending turns out to be the hernia I remember it being. really need more parcatice.

Second was a binding channel routing jig. Its really just a box sliding on a pair of draw runners. The idea being that the router remains vertical despite the doming of the top and back.

Now I've started to cut wood in anger I'll build the remaining jigs as I go along I think.

This one is going to be a nylon strung 8. low b, high a, and yes I'm totally  aware that this will be an abomination in the eyes of the classical guys.

The plan is rosewood back /sides, spruce top. limba neck. solid bindings and a lattice braced back. We'll see how that changes........ I really like the idea of a slotted head with peghed tuners.  Scale lengths 650 / 625mm.

Let the madness commence.

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I've got the back bracing together and radiused the backs dome of 15'. Its looking a bit chunky here, but when glued, will be thinned down a lot. I figured that it would be a bit easier to attach to the back as one unit. The back strip once cut to accept the braces will act like a guide(?) to stop any creep.

The neck blocks almost done. Yes bolt holes. Apologies. The fretboard support is raked up at 3 degrees to allow for the dome of the top and neck angle. I've left final shaping of the curved section till I've got the top braced and the soundhole cut, so there's a bit of wood to play with there. the whole underside will be nicely bevelled off as it will be viewable through the offset soundhole.

Tools now pretty much down until the top and back hit the ranch.

Thanks for reading

Matt

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Thanks Pan. This build is starting to give me the heebie jeebies already.

Today I made a bent stick. This neck is pretty much made up of left overs, but I think I would have laminated anyway. Hot diggity dang this thing is wide. Seeing on paper is one thing, but having it sitting infront of you is something else altogether.

I've ended up with limba with a thick piece of maple running down the middle to the scarf. No fancy laminations - if this one turns out nice, I'll think about that on the next one. This time around I managed to leave myself enough meat for a volute, though wings will need to go onto the headstock before much further ado. The plan was for a 12 fret acoustic and miraculously I think i'm smack on target - famous last words. Thickness is penciled in for 20mm at nut and 25mm at 9th. This will no doubt change though.
 

New favorite tool?  An old Stanley 5 1/2, - a beast when sharp and cutting in anger. Makes me quite curious about how much better the high end planes are.

 

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  • 5 weeks later...

Hello gents.

Not much to report from the coal face. Real life seems to have reared its ugly head again.

I've now joined the top and back using the ghetto clamping cauls pictured, the bench vice and a couple of sheets of glass to stop things sticking together. It worked suprisingly well, which is a relief because I don't think theres enough space in the shed for any more jigs and things. Back was thinned to c. 2.1mm, top is c. 2.7 in the middle and 2mm around the edges. The top doesnt look anything special, but is really nice and stiff. Thicknessing the back was a real P.I.T.A. but I got there with the 5 1/2 and a cabinet scraper.

On  the back the middle strip is on together with the lattice. First time with the home made go bar deck. I'm totally sold on this way of clamping. Once dry I went at the lattice with a small plane to rough shape. I'm going to come back to this to refine.

 

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I've roughed out the headstock and drilled holes for the tuner pegs. Annoyingly a few of them were quite out of true. ho hum. The cutouts were hogged out with the drill press, then cut with a 1 inch chisel and a bit of brute force. I'm yet to chamfer the ends.

The top, which is now nice and rubbery, has had the bracing pattern traced onto it after a frustrating game of find the join. In truth, Im finding excuses not to start thicknessing the sides.....

Thanks for reading chaps.

 

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So I feel like I've done quite alot to this, but in actual fact, not so much.

The sides were jointed along one edgeto act a a reference and thicknessed  from 5 mm to 2mm by plane and scraper. Then they were bent (read as scorched) manually on a bending iron - Im now thinking of building a fox bender - waist first, then upper and lower bouts.

Once the smell of burning wood disspated, the sides were fitted to the mold and cut to length. There is a gap at the butt end, but this will be taken out by the butt strip and slight cupping primarily on the lower bought. Nothing that cant be corrected. 

Once happy with the fit the blocks were glued in, the neck block being 10 mm off the lower edge of the side. G clamps for this, not quick grips. used an absurd amount of pressure for this. To get the angles for the back and top the sides were planed down and the front by 13 and 7 mm respectively. The correct radius was then added to the sides by sanding in radius dishes, 25 feet for the top and 15 for the back.

Next is linings, I was going to go with solid linings, but laziness has made be buy mahogany kerfing.

Thanks for reading

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  • 2 weeks later...

Kind of you to say Scott, though there's been a lot of swearing and head scratching to get to this point. 

The linings went on yesterday. I ditched the idea of solid linings in favour of kerfed. Lifes too short.... I glued them on with about 1mm over the ribs edge and once set sanded on the discs. Some areas needed a bit of encouragement to sit properly, hence the draconian clamping.

Today I sorted out the rib supports. nibbled out whole blocks whereth support lies and glued accross the face of the ribs. Perhaps not the usual way, but I wanted to see if some of the cupping from bending could be taken out. It seems to have worked somewhat and suprisingly looks OK too. Another trip to the dishs and the tops and bottoms are nicely radiused.

Apart from that not a lot to show. I've bought some back and side sets for future projects so mch of the mornings been spent cutting spacers.....

Cheers

Matt

 

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@Prostheta Yeah replaced the chrome thingy, though the bearing's a bit big for the housing, so when it gets to that point I'm going to have to replace I think. Also kicking myself for not building a sled for the box at the same time. It bugs me a bit that I'll have to take time out mid build to get that together.

@Jdogg Cheers mate. Hoping it comes together alright. The main reason I upload these things is that it forces me to work a bit cleaner.......

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Hi Andy

I started out at 2.5mm, but this set seemed quite stiff and quite frankly there were a few concerning cracks that I didn't want to exert too much force on so I think we ended up at about 2.2-2.3 (didn't really take a measurement). I think this leaves just about enough for a gentle scrape and sand once the box is joined, but I'm guessing the cupping is a function of the thickness (thinness). I like them lightweight....

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Cupping might well be related to the amount of curvature in the growth rings....I'm not 100% sure since acoustics and thin wood bending are not my chosen fields. I've done a fair amount of cold bent lamination for mildly-bowed arms (sofa, armchair, etc.) but never really seen any cupping outside of what you'd expect from any thin piece. I'd have suspected that the bending might force the wood to be flatter across the grain since it doesn't readily bend in longitudinal and tangential/radial simultaneously. Again, I'm sort of divining blindly.....

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Me too. I'd love to know more about to how wood reacts to this and that - I know the info's out there, but for some reason I'm just to damn slow to seek it out :D. From the reading I have done, there does seem to be a lot of snake oil and shamanism about in the world of acoustic guitars....

I've cut and radiused bracing - spruce. No big deal, but the grain is nice and tight and nicely perpendicular to the top.

I've also cut a hole. A big hole. A big hole using a ghetto rigged jig. - board with a drill bit in. stick with a hole and a razor bade glued to the other end. It worked, but never ever again. I also got a bit blasé about the grain direction and ended up tearing the middle section on the right. Not so much to cry over, just enough to get annoyed about.

No rosette for this one - they look just a bit chintzy for me. May be looking at binding with ebony though.

Now here's the question. I've half a mind to glue in the two bars (guess you'd call them harmonic bars) to the sides before gluing the top. It would make fitting things around the neck block, and  in this design, the setting of he neck angle easier. Everything should drop fit as the bars could be radiused with the dishes once glued to the ribs, but if a bit of a push is needed, the go deck could be used to provide clamping pressure all over. I think this is the way to go, but will ponder over a cup of tea.

 

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OK long cup of tea later and this is the plan of attack.

thin and shape the extension of the neck block - I was waiting until the soundhole was cut before doing this.

Shape  and glue the long strut.

Shape and glue the short strut.

Radius all on the dish

Plane the neck block to set neck angle.

Don't see why this wouldn't work and it should make fitting the soundhole reinforcement and struts to the neck block easier methinks. Famous last words.

 

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7 hours ago, 103801061982 said:

Hi Andy

I started out at 2.5mm, but this set seemed quite stiff and quite frankly there were a few concerning cracks that I didn't want to exert too much force on so I think we ended up at about 2.2-2.3 (didn't really take a measurement). I think this leaves just about enough for a gentle scrape and sand once the box is joined, but I'm guessing the cupping is a function of the thickness (thinness). I like them lightweight....

The couple of acoustics I've done have aimed at a finished back and sides thickness of 1.9mm, (quite - I think we can assume that is best termed 'nominal' ;).).  I have to say that both are substantially rigid structures (one is Walnut and one is London Plane) although I was nervous for the first one that it might not be.

You are right that anything much above 2mm is very difficult to bend.

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2 hours ago, 103801061982 said:

OK long cup of tea later and this is the plan of attack.

thin and shape the extension of the neck block - I was waiting until the soundhole was cut before doing this.

Shape  and glue the long strut.

Shape and glue the short strut.

Radius all on the dish

Plane the neck block to set neck angle.

Don't see why this wouldn't work and it should make fitting the soundhole reinforcement and struts to the neck block easier methinks. Famous last words.

 

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I'm not sure I can contribute here.  I've never come across a neck block extension.  In 'conventional' builds, any bar attached to the top would contribute to transferring the vibrations to areas of the top that will vibrate harmonically with each of the played notes and so the joint with the top would be the critical one.  Hence normally all components would be glued to the top and scalloped/ shaped first.  

These two struts, however, appear to be more to do with strength.  I'm intrigued, therefore, how the rigid neck block extension, and attached struts, will affect the vibration of the top.  Fascinating stuff...

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Right ho,so that went OK.

Andy, after shaping and when the neck angle is dialled in, the extension wont be all that thick at all - I'm hoping...... The struts are mostly structural really but I've read various wiff waff about bars like this helping to transfer energy from the neck. I don't know nearly half enough to make a decision on whether that's valid.

I did a quick test with the top, and everything is playing nicely at this point. Starting to get quite interested in this one...

Originally the plan was to use threaded inserts in the neck to receive a couple of bolts through the neck block. Nah. I took one look at the inserts I ordered and decided I didn't like the thought of sinking holes that bit into what will be quite a small lump of wood. They would also give hardly any wiggle room. Cross dowel bolts are the new flavour of the week. 8mm holes in the block. M6 bolts.  Dowels held in 10mm holes sunk into the neck from top and bottom. Righty tighty.

Ponder time again.

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Flavours of the month. Seen a lot of those. As far as these bars and connecting rods go, I'll remain unconvinced until somebody demonstrates repeatable and verifiable improvements. If we built instruments off all of the anecdotal information out there, we'd have things thrown together from all manner of craziness. All that, and some people simply miss the fundamental 90% of basic work whilst tone chasing for a few percent of that last ten, you know? Same as "tonewood". Good wood is good wood. Brazilian Rosewood can be found as crap too.

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