The Top

Having finally finished the back it is time to move onto the top.

First job was to glue the two book-matched halves together as on the back and then levelling the assembly and marking and cutting out the outline.

After building two profile templates (one longitudinal and one transversal at the centre line) I power planed down to the rough centreline thickness and started with the thumb plane.  I can’t believe how much easier the spruce is to work compared with the maple on the back. In just a couple of hours the shape is nearly there!

And then mark and cut the purfling slots before gluing in the purfling and cutting the channels.

 

 

 

 

 

 

Then shape the inside after drilling some guide holes.

Plate tuning of back and top is next before cutting f holes and fitting bass bar.

F-Holes

The f-holes were marked by pinning the plan to the back of the belly and pricking through with a knife before joining up the marks with a pencil and adjusting the shapes by eye.

The holes were then cut with undersized forstener bits and reamed out to the correct size (14mm and 18mm) with my peghole reamer and my endpin reamer.

F-holes then roughly cut out with a coping saw.

And then carved to size and matched using a very sharp knife and a scalpel. I undercut the holes so they were bigger on the inside than the outside.

Then I cut the vees and glued on the bass bar.

 

 

 

 

 

 

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The Back

I have 2 beautiful pieces of book matched maple to make up the back.

I started by getting my jack plane (from Axminster) into good working order.  This had never worked particularly  well and after closer inspection I realised why – the blade was slightly bowed and so the burr did not rub off properly.  Well after an hour or so of flattening against my diamond sharpening (stone?) I managed to get it flat and properly sharp and then joy, – producing cigarette paper thin shavings and both halves flat and true in no time.

I used the heat gun to warm everything up, made a new batch of glue and tried a rubbed joint – worked first time and no clamps!

Next was levelling the underside – boy is that maple tough but after about 3 hrs with the jack plane and a few blisters got it done.

Then clamped the ribs to the flat surface to mark out the outline and used a washer to mark the overhang before cutting out on the bandsaw and finishing off with the vertical spindle sander.

Next marked up the thickness of the edge – 5.5mm except for the corners (6mm) and the c-bouts (5mm) before starting all that chiseling! Boy, is that maple hard work!

Arching

I  built some thin plywood templates to help with the arching profile. There is a great article by Sergei Muratov that gives a good starting point for the arching curves.  I adapted these slightly to give an arch height of 25mm on the back.

I used a power plane to get a rough arch height and then a gouge, small plane, and thumb plane.

Purfling

Finally finished profiling the outside of the back – this is a long week!  For anyone actually reading this blog you will by now have realised that my weeks are “virtual”  this week started at the beginning of June and now July is nearly over!  This is the result of actually having to “work to live” and in a job that has me trotting round the globe regularly so this virtual week is so far 7 regular weeks long and have still to shape the inside of the back!

Now for the purfling –   I made up the purfling from a 1mm piece of sycamore sandwiched between two 0.5mm pieces of ebonised pear all glued up (hide glue of course) and clamped between 2 cauls.  Then sliced it up on the band saw into 3mm strips and after a bit of cleaning up with a plane all ready to go.

 

I managed to find a tool for marking the purfling groove on ebay but had to grind the blades down a bit to get them 2mm apart (the width of my purfling) and ground down a very small chisel (I had in my toolbox) to be slightly under 2mm.

 

 

 

 

 

 

Glued in purfling using a syringe to fill the pre-heated channel with hot hide glue, tap down with a mallet onto kitchen roll to stop it spraying everywhere and clean up with hot damp towel.

After gluing all the pieces of bent purfling having taken care to try and get  “bee sting” at the corners I dug out a channel over the purfling with a chisel and then faired the channel into the body with scrapers.

Inside

Now I turn the back over and marked out the desired thickness profile in pencil.

I built a simple rounded stop to put under the drillpress and then drilled holes (1mm over-thickness) all over the back to provide a guideline when hogging out. Then using a fearsome wood carving attachment to the angle grinder (from Axminster) which cuts through maple like butter, I rough hogged out the back to the bottom of the previously drilled holes.

Then it was back to the thumb plane and more blisters to take it down to final thickness prior plate tuning.

 

 

 

 

 

 

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Making the Blocks

Having finished the form the next step is to cut and glue the blocks for the top, bottom and wings.

I cut these from a piece of spruce, cut to length to fit the tapered ribs (120mm at bottom to 116mm at top), flattened the ends and started playing with hide glue for the first time.

Looked at the electrically heated glue pots available for an astronomic price (>£150) and then found a perfect alternative – mini deep fat fryer for £12 from Amazon (thermostatically controlled).  Filled with water – not oil of course – and did a quick experiment to find the setting that gives 135F and then full steam ahead (not literally) with the glue in a jamjar inside the fryer .  Anyway, works an absolute treat and had all 6 blocks glued to the centre layer of the form in no time.

Also  bought a heatgun from Screwfix for £10 for undoing things when I got it wrong and got to try it out immediately!

Next the blocks were marked with the desired profile and carved/filed down to size.

 

 

 

Preparing the ribs

I had some nicely figured maple rib blanks that came about 4mm thick so I started by thicknessing to about 2mm on the drum sander before bandsawing to width (with a few mm spare), scraping the outside to give a good smooth finish and then final thicknessing (the inside) on the sander to 1.5mm.

Then I used my bending iron to shape the C bouts after giving them a thorough dampening with a water spray.

Before gluing up needed to make sure the ribs had thoroughly dried out and shrunk back to their dry size in order to avoid any subsequent cracking.

Gluing the Ribs

This was not quite as easy as it looks – as soon as you put a clamp on they move!  Had to take a few goes at this with several clamps used to hold it in place before squeezing up the pre-shaped cauls.  Also worked much better when both surfaces were pre-sized with glue and pre-heated with a hot air gun.

 

 

 

 

 

 

I made up some cauls to hold the ribs against the form to stop things moving around while the ribs were being clamped up.

After levelling off the ribs I removed the top layer of the form to give room for fitting the linings.

 

 

 

 

 

 

The linings were cut from willow sanded down to 3mm thick and cut into 20mm widths on the bandsaw.  These bent really easily after spraying with water.  Mortices were cut into the corner blocks with a saw and then finished off with a small 2mm chisel and cleaned up with a knife.

I read on the internet how to make some very simple but effective clamps using rubber bands cut from an old bike wheel inner tube.

 

 

 

 

 

 

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Having completed my design it is now time to make up the form that will form the basis for the rib construction.

Having scoured the net to see how other people do it, I eventually plumped for a design based on a central plywood form with removable plywood panels on front and back to allow fitting of the linings.

I started by creating a template out of a piece of 6mm clear acrylic sheet by sticking a full size plan printout to it and band-sawing and then sanding  to the plan outline.

Then I used the  template to mark out a rough outline of the form on the central 18mm plywood and then routed back to the template.  I then used this template to mark and rout the two outer 12mm plywood elements of the form.

Next I cut out the centres of the plywood shapes to reduce weight and provide an anchor for clamping and then cut the notches for the corner posts and end posts.

To get the 120mm rib depth I glued some 1.5″ battens to both sides of the central plywood form and dowelled everything together to ensure alignment.

Finally a few coats of varnish after sanding the edges round to ensure easy removal from the assembled ribs.

 

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