An acoustic for my nephew.

[Andyjr1515]

On 1/2/2022 at 1:50 PM, Dave Higham said:

When I started drawing up plans I found French luthier Christophe Grellier’s OM plan on his web site

My first acoustic build used this same plan 

 

[Dave Higham]

After that I carved and sanded the X-brace to its finished profile and started on the fan braces. All the front braces are let into the X-brace to form a solid framework. Here is one of the fan braces with its notch in the X.

And here it is in place. The sand paper stuck onto the yellow masking tape was used to sand the underside of the fan brace so that it made contact perfectly with the front and the bridge plate, but I forgot to photograph that too.

Here the left and right fan braces are being glued in place. They have had the tops profiled and the off-cuts from the tops are used as clamping cauls.

Here the centre fan brace is also being glued.

Three fan  braces glued.

All the braces fitted and ‘carved’. I haven’t a clue about carving and tuning braces so I just made them look nice. There’s no upper transverse brace as I think it won’t be necessary. The part of the fingerboard which extends over the body will be supported by a neck extension, so there’ll be a cut out in the top for that. I’ve reinforced that area of the top with a cross-grained spruce patch. I think that, together with the A-braces, should make it strong enough. If the box implodes I’ll be proved wrong.

[Bizman62]

6 hours ago, Dave Higham said:

Three fan  braces glued.

Ooh the sound hole in the center fan brace!

[ADFinlayson]

On 1/5/2022 at 3:43 PM, Andyjr1515 said:

My first acoustic build used this same plan 

 

Me three!

[Dave Higham]

17 hours ago, Bizman62 said:

Ooh the sound hole in the center fan brace!

As I said earlier, Stephen Sheriff very generously gave me a detailed drawing of his bracing system and very comprehensive notes on his construction process, so I'll quote him.

"I carve the center brace to "fly" over the bridge saddle area, to leave an open space for the installation of bridge-plate transducer pickup elements, or pickups such as the L.R. Baggs Lyric".

I didn't intend installing a pickup, but Steve's instructions were so detailed that I decided to follow them 'to the letter'.

[Andyjr1515]

That bracing is lovely!

[Bizman62]

3 hours ago, Dave Higham said:

"I carve the center brace to "fly" over the bridge saddle area, to leave an open space for the installation of bridge-plate transducer pickup elements, or pickups such as the L.R. Baggs Lyric".

And I thought it had something to do with allowing the bridge plate to vibrate. What a disappointment!

[Dave Higham]

The back and front were now ready to glue to the sides but, before doing that I had to make the access panel. The access panel isn’t really essential, but it means I can get my hand inside the guitar to adjust the yaw or pitch or whatever of the neck without taking the strings off. If I knew what I was doing, it would also enable me to get inside to fine tune the brace carving with the guitar strung up; but I don’t, so it won’t. I should also mention that this, again, isn’t my design; I borrowed it, with his permission, from another luthier, Kent Chasson.

 

This is the end graft. The different tiles and strips of veneer were assembled on a piece of 1mm ply and this has now been glued to a piece of maple to make the whole thing 5mm thick.

This, together with the birch ply disc we saw earlier and a piece of very old dark mahogany (because that’s what I had), also thicknessed to 5mm, will form the access panel.

I trimmed the maple flush with the tiles and glued a piece of white veneer on either side.

A 5mm hole was drilled through the end graft to locate it, and the mahogany cut into two pieces and the cut edges trimmed.

The mahogany pieces were band-sawn to an oversize circular shape and glued to the plywood disk. The tapered end graft isn’t glued in place yet. It’s positioned with a dowel pin through the hole and into the plywood disc.

Now the wedge is removed and the mahogany trimmed to the required diameter.

A piece of white veneer is glued to the outside of each mahogany segment.

The ends of the wedge are trimmed, the veneers are trimmed flush with the mahogany but the wedge still isn’t glued in place.

[Dave Higham]

Now I had to make a corresponding hole in the sides. To do this, I made another disc from MDF with a 5mm hole in the centre, and which fitted snugly into the hole in the tail block. This was dowelled to an MDF base. The end block was aligned with the dowel pin and fixed to the base with double sided tape.

The hole was then cut using the circle cutter and a ledge carefully cut to fit the circular mahogany panel.

The wedge was then fitted into the circular panel and the panel positioned in the hole. A line was scribed on either side of the wedge and a recess cut to accept the ends of the wedge.

The wedge is now finally glued into the panel and the panel fitted into the sides. The panel is almost flush with the sides in the centre but, as it is flat, it protrudes more at the outer edges. To trim this down flush with the sides, it will need to be held firmly in place.

[Andyjr1515]

On 1/11/2022 at 7:05 PM, Dave Higham said:

Now I had to make a corresponding hole in the sides. To do this, I made another disc from MDF with a 5mm hole in the centre, and which fitted snugly into the hole in the tail block. This was dowelled to an MDF base. The end block was aligned with the dowel pin and fixed to the base with double sided tape.

 

The hole was then cut using the circle cutter and a ledge carefully cut to fit the circular mahogany panel.

 

The wedge was then fitted into the circular panel and the panel positioned in the hole. A line was scribed on either side of the wedge and a recess cut to accept the ends of the wedge.

 

The wedge is now finally glued into the panel and the panel fitted into the sides. The panel is almost flush with the sides in the centre but, as it is flat, it protrudes more at the outer edges. To trim this down flush with the sides, it will need to be held firmly in place.

 

Good heavens!

[Dave Higham]

So now I need to make the bits that hold it in, starting with these two little maple blocks.

And this aluminium channel. You can see how it works from the drawing. You slide one end of the channel in, pivot the other end into place and slide it back to centralise it. The little blocks then stop it falling inside the body when you install the panel.

The blocks are glued in place.

One end of the channel inserted.

The other end swings in and the channel is centralised.

A small block of wood is glued into the channel to take a wood screw.

The panel is now held firmly in place by that big wood screw and can be planed down flush with the sides. The wood screw is temporary; it will be replaced by an end pin after finishing.

Now I can glue the back on.

[Bizman62]

So many details! That's exhaustively engineered, yet every detail serves a valid purpose. That'll be an acoustic on steroids!

[Gogzs]

I'll press "Thanks" from now on for your updates, because we're past the point of me liking this thread. I know I won't be building acoustics anytime soon, if ever, but the level of craftsmanship in this thread is truly inspiring. Thanks for that, can't wait to see the rest.

[Dave Higham]

Thanks for your comments Biz and Gogzs. I truly don't think of myself as a 'craftsman', perhaps because in the past I worked with some real ones (silversmiths). The boss was a reputed designer/silversmith who also taught at the Art College so he only invited the best of the apprentices who studied there to come and work for him. We called him 'Hawkeye' because, if there was the slightest blemish on a piece of work, he saw it! I suppose some of the attention to detail, etc., rubbed off on me.

[Dave Higham]

What happened next was that I glued the front on, routed for bindings and glued in bindings and purflings and during all that I completely forgot about taking photos.

I also have to confess that I chickened out on the arm-rest bevel, so I just installed faux tortoise binding without side purflings.

It didn’t look very nice.

My little 1/8” down-cut router cutter was knackered so there was rather a lot of chipping out in the binding rebate that I only noticed when I’d finished cutting it. But I was hoping that glue and sanding dust would disguise it. This curly Claro does seem to be rather brittle and chips easily.

The cold weather had set in (this was in January) so I‘d bought a humidifier which kept the workshop at about 40 to 45% RH. It worked fine for about a month, and then it gave up the ghost. I took it back to the shop where they said they’d have to send it away to be repaired and then we left for ten days to go to Venice for the Carnival. Of course, I should have turned the heating off in the workshop, but I forgot and when we got back I found the humidity down to about 20% and the top had a 5” crack in it. Oh, and a message from the shop to say that my humidifier was ready for collection.

I didn’t mention this before, but I’d already had a couple of problems with the rosette. One was that there was some slight tear-out of the spruce in the purfling channel. The other was that in spite of sealing with shellac, it would appear that some of the CA leached into the end grain of the spruce and discoloured it slightly. I think the problem was that the shellac I used is old and didn’t dry hard, but I decided it would have to do.

I now had a distinct feeling that something or someone was trying to tell me something. Like I shouldn’t have ‘made do’ with tear out in the rosette channel, CA staining the spruce, using plastic binding and avoiding the side purflings and chickening out on the arm-rest bevel and was now being told to try ‘making do’ with a cracked top! So with more than a little helpful advice from kind people on another forum, I routed the top off and started again; which is why some of the previous photos are of the first top and rosette and some are of the second.

Having decided that this time I should try to make a proper job of it, I made a new top and thought I really ought to have a go at the arm rest. By now, I’d gleaned some more information about how different people go about it and one thing I’d found is that some cut the armrest profile into the top and the side before assembling them. I couldn’t do that with the side as the lining was already glued to it, but I could do it to the new top, so after a bit of fiddling about drawing the profile in CAD, I cut the shape into the top and this is what it looked like.

[Dave Higham]

The last photo gives a false impression of what the armrest should look like as the shape includes the surplus which will be trimmed off after the top is glued on, as shown here. My intention was to try to achieve a smooth blend of the armrest into the body shape.

I then re-routed the binding rebate, slightly deeper than the first time. At this point the transition from armrest to body profile still isn’t smooth, but the purfling rebate has still to be cut.

I decided, this time around, to make wooden bindings using the off-cuts from the sides. The front bindings can be straight, but the back has such a wavy profile that I used the templates I made for the linings to make profiled back bindings. It wasn’t wasteful as the side off-cut already had that profile. It just needed smoothing out.

This time, I glued a single white side purfling veneer to the bindings before bending them. I used waterproof (exterior) PVA wood glue and it worked fine. The two bindings back-to-back (nearest the camera) are the straight ones for the top. The other two are the wavy back bindings which couldn’t be bent back to back but the purflings didn’t come unstuck even so. There was a little spring back, although there doesn’t seem to be in the photo. That’s because the bindings were stuck to the kraft paper and the paper stuck to the slat.

You can see the little green clips I spoke about earlier. There are 8 in all and they keep the inner slat in place while dismantling the rest, so the slat can’t straighten out and break the bindings.

Now I needed to cut the armrest profile into the side. I drew the curve I wanted and stuck it onto the side and very slowly and carefully cut it using a craft knife and chisels.

[Dave Higham]

I then cut the rebate for the top purfling and finally got a fairly smooth transition into the armrest. Not perfect, but not bad for a first attempt.

I stuck this off-cut from the top back where it came from while routing the purfling rebate, so that the ‘donut’ which rides on the top didn’t fall into the armrest area and ruin everything.

The top purfling was now glued in place. (Why don’t they make it long enough to go all the way round?)

 

[Dave Higham]

When I made the bindings I made an extra bit but not as deep as the rest which is glued in place here. This means that when I finally get to cutting the bevel I won’t have to cut right up to the purfling

The ends of this piece of binding will need to be pared down to be flush with the purfling before installing the ‘real’ binding.

Like so.

I actually did this by running the router round the binding ledge again, which nicely tapered off the ends.

Now I can install the ‘real’ binding. The height of the binding was reduced to about 2.5mm (0.1”) in the area of the armrest which made it a lot easier to push down to the side profile.

I let this piece of binding overlap the tail graft as I need it to be glued to the sides but not to the tail graft (or I won’t be able to get the access panel out).

Glued in the treble side top binding too.

I then set about cutting the bevel. I took most of it off with a spoke-shave, but didn’t trust myself to get an accurate 45° by hand without accidentally rounding off the corners so I made this rather cumbersome looking sanding thingy. It worked really well, doing most of the work with 80-grit abrasive and finishing off with 150-grit.

I finished up with a triangular section groove next to the top and side bindings so I glued two fillets in and sanded them off flush with the rest. You can just see where they are in this photo

I realise this is getting very long-winded (and perhaps boring), but the truth is I decided to make it as detailed as possible, mostly for my own benefit. Because I knew that the next time I made one I wouldn’t be able to remember half of how I did it the last time.

 

Edited January 23, 2022 by Dave Higham

[mattharris75]

Not longwinded or boring at all! Personally I've wanted to see a step by step of this technique for years, so thank you!

[Dave Higham]

2 hours ago, mattharris75 said:

Personally I've wanted to see a step by step of this technique for years, so thank you!

You're most welcome.

[Andyjr1515]

On 1/14/2022 at 11:13 AM, Gogzs said:

I know I won't be building acoustics anytime soon, if ever, but the level of craftsmanship in this thread is truly inspiring. Thanks for that, can't wait to see the rest.

Or paraphrasing @Gogzs comment above, "I do build acoustics, but the level of craftsmanship in this thread is truly inspiring.  Thanks for that, can't wait to see the rest."

 

[Andyjr1515]

On 1/18/2022 at 1:45 PM, Dave Higham said:

I routed the top off and started again

I think many of us have been there.  There are some things that can be hidden, incorporated or bypassed,  But there are some things that happen in my builds, that I know will just niggle at me if I don't fix it and so it is worth taking a couple of steps backward before a dozen more forwards...

On 1/18/2022 at 1:45 PM, Dave Higham said:

Having decided that this time I should try to make a proper job of it, I made a new top and thought I really ought to have a go at the arm rest

...but that takes a few pints of fortitude!  Presumably that meant all of the bracing work again?

 

[Dave Higham]

6 hours ago, Andyjr1515 said:

Presumably that meant all of the bracing work again?

Yep!

[Andyjr1515]

1 hour ago, Dave Higham said:

Yep!

Oh wow...  

[Gogzs]

Finally caught up on reading it all. Sorry to hear about the hardships you encountered, but I'm kinda glad it happened and you went all in with the arm bevel with the second top. Interesting read, I'll sound like an ass, but I love reading such stuff and learn from other peoples mistakes  Nice set up for the sanding block to get the bevel done. I assume the guitar is on a rotating stand or just fixed on a sled you were sliding freehand around?

All in all, impressive save, and work on the bevel. Godspeed for the rest!