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.
3 thoughts on “Cello Week 3 – The Ribs”
Looking fantastic David cant wait to hear it played
Thanks Brian – only another 200 hours to go!