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Ash's acoustic rabbit hole


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Some modest progress this evening. Glue up went well on the top so I got that sanded down a bit and cut out, still way over thickness but I'll worry about that later. It's occurred to me that the 80 grit roll of paper that the drum sander is currently armed with is really not ideal for acoustic building, the scratches it leaves require a lot of work to sand out, it's more like the equivalent of 40 grit hand sanding. So I've ordered a roll of 120 for final sanding. 

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Gave the inside of the sides a good sand and made some side braces which are now in. They're 5mm wide by 3.5mm deep and I've rounded them off, I went for 4 on the lower bout then 2 on the arm bevel side thinking that lump of limba is adding a lot of stability so they're probably not necessary passed the waist.

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I also carved the underside of the arm bevel. Very awkward to get to especially when the grain is working against you. I used a 20mm chisel bevel side down to do as much as it would reach, then thumb plane and finished up with a concave min scraper.IMG_0361.thumb.jpg.bac6de479c47dee3daf68c20bc67caec.jpg

Then got to work on rosette making! Carrying with the theme of using up those offcuts. I cut the last figured piece of limba out, marked some angles and cut it out on the band saw, which left me with the worlds tallest rough sawn trapeze inlay.

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Knowing what I know about my hand planing skills, I opted to sand the saw marks out, I'll just end up putting a twist in it with a plane. Didn't bother sanding top or bottom as its only the sides that will be kept.

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Then I cut it into slices on the bandsaw with the fence and cross cut sled, neither of which are very good on this saw.

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I had a diagonal pencil line across the back so that I could pile them back up in the right order

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Then I laid them out, flipping every other one so that each piece is bookmatched with the previous one (smug), then numbered them.

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I decided at this point that it was just a bit on the small side, I must have got my angles just a bit too tight and reduced the diameter slightly, so I glued them all up with a slither of bog oak veneer in between which should increase overall diameter by a couple of mm, I'll no doubt have to add a veneer around the edge of it anyway if my hole isn't bang on. Used superglue and accelerator. The band saw blade left a bit of fuzz so I did give all the edges a quick sand with 240 as I went.

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And now it's ready to be cut out. I kept the pieces on the thick side because the end grain is quite delicate, hopefully it survives the rest of the process. If I do this again, I'll glue it up on a backer to help maintain structural integrity. I'll also make the wedge taller so I've got more material to play with - I want the rosette to be fairly thin anyway but I don't have a huge amount of figuring choice.

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And a glam shot.

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I have to pinch myself that this is the second one!

What final thickness are you planning for the top?  For decent European Spruce, I usually aim for about 3mm, giving a decent compromise between strength and resonance.

I'm intrigued with the side braces...are they on the plan?  I confess I've never fitted them on any of mine.  No great shakes either way - the sides don't affect the sound and they won't weigh much. :)

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7 hours ago, Andyjr1515 said:

I have to pinch myself that this is the second one!

What final thickness are you planning for the top?  For decent European Spruce, I usually aim for about 3mm, giving a decent compromise between strength and resonance.

I'm intrigued with the side braces...are they on the plan?  I confess I've never fitted them on any of mine.  No great shakes either way - the sides don't affect the sound and they won't weigh much. :)

Probably a bit silly cracking this far on with number 2 before I've even finished number one, I know. 

The Grelier plans I have state 2.8mm for the top, But I was going by "flex" and at 2.8mm there just wast any, the top was really stiff, so I went down to around 2.1 - 2.2 although I've had to scrape the top quite a bit ti get my superglue mess out so there is a possibility that it might be too thin 😱  I'm hoping the hardwood braces and the fact that I tied more braces into the sides will work in my favour.

I haven't decided how thick to go on this one yet, I'm not in a position to get it down to thicknessed until my 120 grit paper arrives for the sander anyway. 

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7 hours ago, Andyjr1515 said:

I'm intrigued with the side braces...are they on the plan?  I confess I've never fitted them on any of mine.  No great shakes either way - the sides don't affect the sound and they won't weigh much.

Ah I missed part of your post. There is no mention of side braces, but I thicknessed my sides down to 2mm and there is a lot of fluf, burn marks and 80 grit scrates from the sander I still need to scrape off so small braces are there as a bit of caution. I don't know if the will contribute to "tone" at all

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Well it's cut out and inlayed, the veneer I used was a real pain to get in, paper thin and just wanted to fold over. Came out ok though apart for a little bit of tearout in the upper left corner on the outside, I'm hoping that bringing the whole lot down a hair or two will sort that out before I thickness from the back. Will keep it as is until Ive got some 120 grit.

It's all quite subtle but the bookmatching is definitely visible

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I was hoping to be getting back on with the other one but I made the mistake of ordering my binding from stewmac on Labour weekend (or whatever that is called) so it's only  just been dispatched. Can't do anymore on this one until my bracing material arrives from Spain, so I guess it's time for 🍺  instead

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the 120 grit roll for the sander showed up today so I got that setup and tidied up the rosette. The top is now sanded to 2.5mm I had to reduce it down quite a bit to tidy up the tearout. But was was pretty stiff anyway so I think it wanted to be around that thickness. I shall have to be careful what sanding I do and try and protect it as much as I can throughout the rest of the build. 120 grit has left it night and smooth though.

In hindsight, the the black veneers between the segments didn't really do much, I think I would have been better off doing something like maple/bog oak/maple. Never mind.

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I decided I would go with walnut for the binding. Easier to bend than ebony but still fairly dark. And I have a spare set of walnut sides, So I thicknessed one of them down to 2.3mm, plained up both edges and started cutting binding strips from outside in. I used a marking gauge to mark out 6.5mm strips. As it's so thin the marking gauge would almost get through it but I just went over the groove a few times with a scalpel from either side and it cut up quite cleanly. Cut 6 strips but I think I should be able to get at least 16 from each side if need be. I shall use the same material to make the veneer that will cover the arm bevel so hopefully it should all blend in nicely. 

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9 hours ago, ADFinlayson said:

In hindsight, the the black veneers between the segments didn't really do much, I think I would have been better off doing something like maple/bog oak/maple.

In my opinion they work well! They match with the darker grain of the segments and hide any insignificant imperfections in the bookmatches, yet they keep the rosette solid. Pale veneers would cut the rosette into pieces like a cake which might require additional rings both inside and outside to make the segments look like decorations instead of separate blocks. And it ties nicely with the fretboard! Also, any finish will most likely make it livelier.

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I’m with biz on this one. Love the subtle veneer. I think maple would have outshone the subtle grain of the rosette. This thread is inspiring as I am in the market for a new acoustic……… dangerous! Probably would go with a kit for the first time around. And definitely have to finish the current build before I take on anything else

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21 hours ago, Charlie H 72 said:

I’m with biz on this one. Love the subtle veneer. I think maple would have outshone the subtle grain of the rosette. This thread is inspiring as I am in the market for a new acoustic……… dangerous! Probably would go with a kit for the first time around. And definitely have to finish the current build before I take on anything else

Thanks Charlie I'm sure something like the stewmac kit where the sides and binding are pre bent would be a good starting point and certainly put off some of the jig making!

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Speaking of jigs. I got fed up with Macgyvering sometihng on the workmate every time I wanted to join thin pieces so I've just made a plate joining jig similar to the LMI one, only a lot cheaper! I've found carve tops are fairly easy to clamp up due to thickness and lack of flex, acoustic backs and tops want to bend all over the place so need plenty of support and a flat surface to do the glue up on. 

I used a load of the cherry wood framing stock my neighbour gave me in the spring, Once I'd planed off the lip, it was about 50mm x 20mm by varying lengths. There are two vertical braces 80mm apart so I can see the centre seam on both sides  of the glue joint then 3 horizontal braces that the rope is tied round. Not sure what the exact name for the join type is but it's essentially the same as an X brace for a soundboard and there are 6 of them so it took a little while by hand. I didn't follow any specific dimensions for this other than the largest and smallest tops from my stash and making it work with both. 

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I tried it out with a 5mm ebony set, you may see the top isn't jointed, I was just testing it out but the bits that did make contact were clamped up nice and tight. I made the wedges out of the same stock, 50mm tapering town to zero. The double wedge at the bottom is way superior to just a single wedge so I think I'll cut a couple more.

Got some braided rope which I tied and looped at one end and wrapped fairly tightly diagonally across and around each of the horizontal braces, then pushed the wedges in to pull it all together. The rope pulls the two pieces together and and the wedges tighten the rope and provide the downforce to keep the workpiece flat against the jig. 

IMG_0448.thumb.jpg.7145019c047e6653c67acf336df8ba64.jpg

Then on the back you can clearly see the joint too.

IMG_0449.thumb.jpg.8e822dad821be31fe0b032a762b3b359.jpg

Feeling a bit smug, I thought I'd try it out for real and see how thick a workpiece it could manage. so this is a 16mm maple top that I jointed and glued up.

IMG_0456.thumb.jpg.a3b03d5c03d719e062b65b45fbbd3765.jpg

Another thing I noticed about this clamping method is there isn't really any slipping when tightening it up. Before the wedges go in, it's still just about loose enough to manipulate the joint, but when the wedges are pressed in, it doesn't really cause it to slip about - I guess this is because down pressure is being applying equality with pulling the joint together. It's a cool way to clamp, no wonder it's been used for hundreds of years! 

IMG_0455.thumb.jpg.2f2791a04f9dd2801309702578ded5cb.jpg

One last thing that I found quite cool, and a happy accident. The X and Y braces that make up the frame are not glued they're just a friction fit and the orientation of the joinery means that the rope holds them together, yet if need be I could take it all apart and stash it. HOWEVER my workshop is normally a mess and I'll end up losing bits of it so I think I'll glue them up.

 

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12 minutes ago, ADFinlayson said:

Speaking of jigs. I got fed up with Macgyvering sometihng on the workmate every time I wanted to join thin pieces so I've just made a plate joining jig similar to the LMI one, only a lot cheaper! I've found carve tops are fairly easy to clamp up due to thickness and lack of flex, acoustic backs and tops want to bend all over the place so need plenty of support and a flat surface to do the glue up on. 

I used a load of the cherry wood framing stock my neighbour gave me in the spring, Once I'd planed off the lip, it was about 50mm x 20mm by varying lengths. There are two vertical braces 80mm apart so I can see the centre seam on both sides  of the glue joint then 3 horizontal braces that the rope is tied round. Not sure what the exact name for the join type is but it's essentially the same as an X brace for a soundboard and there are 6 of them so it took a little while by hand. I didn't follow any specific dimensions for this other than the largest and smallest tops from my stash and making it work with both. 

IMG_0452-1.thumb.jpg.06c1de69fe88ea3e161d55bafc88dcc5.jpg

I tried it out with a 5mm ebony set, you may see the top isn't jointed, I was just testing it out but the bits that did make contact were clamped up nice and tight. I made the wedges out of the same stock, 50mm tapering town to zero. The double wedge at the bottom is way superior to just a single wedge so I think I'll cut a couple more.

Got some braided rope which I tied and looped at one end and wrapped fairly tightly diagonally across and around each of the horizontal braces, then pushed the wedges in to pull it all together. The rope pulls the two pieces together and and the wedges tighten the rope and provide the downforce to keep the workpiece flat against the jig. 

IMG_0448.thumb.jpg.7145019c047e6653c67acf336df8ba64.jpg

Then on the back you can clearly see the joint too.

IMG_0449.thumb.jpg.8e822dad821be31fe0b032a762b3b359.jpg

Feeling a bit smug, I thought I'd try it out for real and see how thick a workpiece it could manage. so this is a 16mm maple top that I jointed and glued up.

IMG_0456.thumb.jpg.a3b03d5c03d719e062b65b45fbbd3765.jpg

Another thing I noticed about this clamping method is there isn't really any slipping when tightening it up. Before the wedges go in, it's still just about loose enough to manipulate the joint, but when the wedges are pressed in, it doesn't really cause it to slip about - I guess this is because down pressure is being applying equality with pulling the joint together. It's a cool way to clamp, no wonder it's been used for hundreds of years! 

IMG_0455.thumb.jpg.2f2791a04f9dd2801309702578ded5cb.jpg

One last thing that I found quite cool, and a happy accident. The X and Y braces that make up the frame are not glued they're just a friction fit and the orientation of the joinery means that the rope holds them together, yet if need be I could take it all apart and stash it. HOWEVER my workshop is normally a mess and I'll end up losing bits of it so I think I'll glue them up.

 

i don't want to send the wrong impression or anything (I'm spoken for) but a............. "noice jig"!

I mean that in the most plutonic way possible.  some good looking tops there too.  rawk on.

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9 hours ago, Crusader said:

I've always said building an accoustic is way over my head and seeing your work on this has not changed my point of view, nice work!

Based on my limited experience of acoustic building and what I've seen of your builds, an acoustic is totally not out of your depth. But if it is, there is always @Andyjr1515 to step in and point you in the right direction like he has for me :) Besides, these two might still implode yet, they're far from finished 😆

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;)

5 hours ago, ADFinlayson said:

Speaking of jigs. I got fed up with Macgyvering sometihng on the workmate every time I wanted to join thin pieces so I've just made a plate joining jig similar to the LMI one, only a lot cheaper! I've found carve tops are fairly easy to clamp up due to thickness and lack of flex, acoustic backs and tops want to bend all over the place so need plenty of support and a flat surface to do the glue up on. 

I used a load of the cherry wood framing stock my neighbour gave me in the spring, Once I'd planed off the lip, it was about 50mm x 20mm by varying lengths. There are two vertical braces 80mm apart so I can see the centre seam on both sides  of the glue joint then 3 horizontal braces that the rope is tied round. Not sure what the exact name for the join type is but it's essentially the same as an X brace for a soundboard and there are 6 of them so it took a little while by hand. I didn't follow any specific dimensions for this other than the largest and smallest tops from my stash and making it work with both. 

IMG_0452-1.thumb.jpg.06c1de69fe88ea3e161d55bafc88dcc5.jpg

I tried it out with a 5mm ebony set, you may see the top isn't jointed, I was just testing it out but the bits that did make contact were clamped up nice and tight. I made the wedges out of the same stock, 50mm tapering town to zero. The double wedge at the bottom is way superior to just a single wedge so I think I'll cut a couple more.

Got some braided rope which I tied and looped at one end and wrapped fairly tightly diagonally across and around each of the horizontal braces, then pushed the wedges in to pull it all together. The rope pulls the two pieces together and and the wedges tighten the rope and provide the downforce to keep the workpiece flat against the jig. 

IMG_0448.thumb.jpg.7145019c047e6653c67acf336df8ba64.jpg

Then on the back you can clearly see the joint too.

IMG_0449.thumb.jpg.8e822dad821be31fe0b032a762b3b359.jpg

Feeling a bit smug, I thought I'd try it out for real and see how thick a workpiece it could manage. so this is a 16mm maple top that I jointed and glued up.

IMG_0456.thumb.jpg.a3b03d5c03d719e062b65b45fbbd3765.jpg

Another thing I noticed about this clamping method is there isn't really any slipping when tightening it up. Before the wedges go in, it's still just about loose enough to manipulate the joint, but when the wedges are pressed in, it doesn't really cause it to slip about - I guess this is because down pressure is being applying equality with pulling the joint together. It's a cool way to clamp, no wonder it's been used for hundreds of years! 

IMG_0455.thumb.jpg.2f2791a04f9dd2801309702578ded5cb.jpg

One last thing that I found quite cool, and a happy accident. The X and Y braces that make up the frame are not glued they're just a friction fit and the orientation of the joinery means that the rope holds them together, yet if need be I could take it all apart and stash it. HOWEVER my workshop is normally a mess and I'll end up losing bits of it so I think I'll glue them up.

 

Nice jig.  Consider the idea stolen :)

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  • ADFinlayson changed the title to Ash's acoustic rabbit hole

I've renamed the thread as it was no longer appropriate to the situation I've found myself in. 

I've started working on building a Fox "ish" style bending machine this afternoon... Starting with the form. I needs to be min 6" wide to accommodate a 6" wide ceramic heat blanket that I've just ordered from ebay and side bending straps (6" wide 0.0012 / 0.3mm spring steel) that I've ordered from Rall online - I couldn't find generic spring steel that was thin enough unfortunately. 

It's mostly constructed out of chipboard because I recently got myself some standing desk legs for my home office and this chipboard made up the original legs for my desk, this saved me a job taking it to the tip and also saved me remortgaging to be able to buy enough ply or mdf.

I still need to add one more lamination but it's a slow process. I made the first one by routing around half of my body template, then I used a rebate bit to make it 2.5mm smaller! to account for the sides and spring steel. roughed out a load more (borrowed my dad's jigsaw because the desk parts won't fit on the band saw), then glued and screwed on one laminate, then routed it to final shape, rinse and repeat. 

At this point I'm hoping the 2.5mm reduction is enough smaller for the bent sides to fit perfectly in the outer mold otherwise I'm going to have a pig of a time reducing it further - it is currently beautifully square.

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I've started working on a template for the centre press block thingy. I wondered if it might be a bit too narrow so I got a second opinion from a classical builder friend who suggested I make it wider to help spread the load which will help to reduce cracking - he has the LMI version but said he's made a couple of his own forms for it, so I'll be back to the drawing board on that tomorrow. I've got one more piece of desk left so that should be plenty to do my last for lamination and laminate a load of pieces for the centre press block thingy.

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I've ordered a 18" press screw, I suspect that is longer than necessary but the only other option (at a reasonable price) was 9"  and I'd rather it be on the long side than too short - there needs to be enough clearance to get the bent sides out of the machine afterwards.

The next part to build will be the frame, but more on that later!

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Well I got the last lamination on the mold, I ended up flush trimming the last couple with the plunge router from above, this thing has acquired quite a bit of mass and harder to slide around so I was getting concerned about pushing against the little makita trimmer in my makeshift router table.

I made the template for the centre press block thingy bigger. It's now 120mm wide giving me a bit more contact area at the waist. I made it out of lams of waste 9mm ply that I had, glueing and screwing then flush trimming one at a time. I used up the 9mm because holding this little block of wood up to the router table was fairly scary and I didn't want to try taking too much in a single pass with my fingers that close to the bit. Highly tedious though with 17 pieces!

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The centre strip that I inlayed is an ebony offcut from a fretboard, it will serve as an alignment rod to make sure it is screwed down square during the bending process. I was about to route the channel for it and realised there is a (albeit small) possibility that I might hit one of the many screws that are in that block, decided that I'd rather ruin a chisel than risk hitting one of those screws with a router bit. so I used a 6mm chisel to hog out most of it, then the mini router plane to tidy it up - I got that very recently, it works amazingly well if you need to make a truss rod channel a hair deeper. Fortunately no hand tools were harmed in the making of this channel.

You can see in the close up pick below that it looks like the centre section doesn't fit properly, that's because the shape is 4mm larger than the inner mold to account for the width of the side, the two pieces of spring steel and the heat blanket, hopefully that's going to work out.

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Next thing will be the frame but I think I'm going to wait until the heat blanket and press screw have arrived so I can be sure on dimensions.. 

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Had a wood delivery the other day, including my spruce bracing stock, African ebony fretboards, head plates and bridge blanks, also a couple of more tops, a german spruce and a sitka spruce. None of the above is particularly expensive wood. e.g the tops were around £15 each, bridge blanks £2 a go, head plates £2.80  and fret boards £8.50. But all good quality for the price, no defects, I've used a few of their fretboards now and can't fault them so highly recommend Maderas Barber for acoustic stuff, their electric tops and body blanks are a bit of a rip off IMO.

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The brace wood was nice and dry so after the better part of a week I started cutting some of it up to make my braces for the limba build. When I cut the lap joint for the x brace this time, I followed the Driftwood guitars method - marked them out against the template aligned them together in the vice and cut them both at the same time. The resulted joint was much better than the last - fitted together perfectly with no play and lined up with the template perfectly,

Also cut up one of the face plates to make the bridge reinforcement. Cut to 2.5mm then radiused on the deck. Got that glued in at the same time as the x brace.

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My stewmac order hasn't arrived yet so I'm still waiting on the extra ebony binding which is holding up the walnut build. 

 

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