For some while now, I have been getting an annoying string buzz from one of the sympathetic strings, so I decided that now was the time to make a new bridge.

I used the previous one I made as a rough template, but raised the centre ‘D’ a little and ensured it was completely flat across the bottom so the sympathetic strings would not move to the side. I cut small grooves for them and lined up the top profile and cut matching string notches along the top. The wood is Tasmanian blackwood – I thought I’d see what difference a harder wood would make.

The sound is more crisp and slightly thinner, but still warm. As the bridge plays in better I shall have a better idea of the sound. And yes the annoying string buzz has now gone!

Hardanger fiddle bridge

Cheers
Jerry

The sides glued up well, and progress continues – after removing the clamps I gave the sides a quick clean-up with sandpaper to remove glue squeeze-out. Titebond liquid hide glue is great to work with, allowing some slip time to get everything lined up ok, but then once it starts to bind it holds well and dries within a few hours.

The mandolin is now starting to look like an instrument, but it is still fairly rough around the edges. The binding provides a decorative border, but also provides additional strength and protection for the joints. I have been quite worried about the gluing process, because hide glue has a use-by date, and I was half-way through before I read the bottle and found it was out of date by six months. Apparently Titebond put a 12 month use-by date on, but liquid hide glue can last 12-18 months. Perhaps I was lucky this time. But if any components fail I will be buying a new bottle forthwith. I could use the hide granules, but that would involve messy use of double boilers and rushing to use it before it cools etc. The liquid glue is very easy to use, is versatile at room temperature and works well.

Anyhow, I had bought some inlay banding strips at the 2008 Canberra Timber and Working With Wood show with a view to their potential for instrument bindings. The banding strips are about 1.5mm thick and about 6mm wide and 1.2metres long. They are easy to use, being flexible enough to do each of the bouts without steam bending, and thin enough to cut easily with a sharp knife.

You’ll have to wait to see how it looks, as they are still taped in position after gluing, but the early indications are good :-)

mandolin bindings

mandolin bindings

The next pictures won’t look much different as I still have to add the bindings for the back/bout interface!

The small round piece of blackwood in the foreground will become the back button, concealing the two pins that help to locate the neck – but more on that tomorrow.

I basically have the back bindings, fitting the fingerboard and some finishing work on the head before fitting it up ready to play – so not long now!

Cheers
Jerry

Yesterday I made bent the bouts or sides into shape and clamped them in place so they would retain their shape ready for gluing.

I realised I would need more luthier clamps so I decided to make some more. They are easy and cheap to make. In my case, the ones I made for the violin project were too small for the mandolin which has a deeper body.

Making luthier clamps
I bought two lengths of 3/16-inch threaded rod and packs of washers, nyloc nuts and wing nuts for that size. I already had some 3/4-inch dowel.

I cut the threaded rod with a hacksaw into 12 equal lengths of 100mm (4 inches), cleaned up the cut ends with a file and threaded on a nyloc nut – just enough to bring the thread flush with the nut. The nylon inner coating will hold it in place as the fixed end.

Then I drilled a 3/16-inch hole in the end of the dowel to the full depth of the drill. It doesn’t have to be precisely centred but it helps to be reasonably vertical.

luthier clamps

I then ‘salami’ sliced the dowel into half-inch or 1.5 cm lengths. I then re-drilled the next batch and so on until I had 24 dowels.

luthier clamps

I then took the threaded rods and slipped on a washer, then dowel, then dowel then washer and finally wing nut to make the completed clamp. The dowels will not damage the instrument and will gently draw the top and back plates together against the bouts.

luthier clamps

And here is the instrument glued up and clamped in all directions – a woodworker can never have too many clamps!

luthier clamps

I also made a maker’s label and attached it where it would be visible through the sound hole.

maker's label

What you won’t see is the hidden wish on the underside of the top plate – that will only ever be seen by a future repairer or someone with a dentist’s mirror ;-)

Cheers
Jerry

And so to bending the sides. You will recall I made a luthier’s bending iron from a piece of water pipe and a heat gun, well here it is in action bending the sides, or bouts of the mandolin.

The first bend was the upper bout for the top quadrant to the right of the neck – this would be the least conspicuous if I made a mistake.

I ensured the bending iron was at the right heat – so water misted onto it boiled immediately

luthier's bending iron

I had the bouts soaking in a tub of water for about 20 minutes. They had been thinned to just under 2mm with the wasp sander mounted on my drill stand. They probably needed to be a little thinner still – more like 1.0-1.5mm thick for easier bending.

Once the iron was hot enough I donned leather welding gloves – so my fingers wouldn’t get burnt if I made a mistake – and picked up the bout and the metal bending sheet that I had made earlier. The bending sheet provides support to the fibres of the timber and helps to hold the steam in the wood. I’ll explain in a moment how I made the backing strap.

luthier's bending iron
I gently worked the timber, springing it slightly and pressing with a wrapping motion against the bending iron. You can feel it reach the right temperature and the point at which it wants to bend. Don’t rush this because – as I found – if you try to go too hard too quickly you will snap the timber and have to start over. It’s best to have a test piece or two so you can practice first on a non-critical component. Here is another view of the process.

luthier's bending iron

Within about two hours I had all the bouts shaped and clamped to the body so they would dry and retain their shape. Blackwood is notorious for springing back to its original (flat) shape. I left it overnight to cool.

The bending iron worked well. I would get it really hot on the 600C setting then when it reaches operating temperature I dialed it back to 300C to maintain heat without stressing the heat gun too much.

Making the bending strap
The strap is quite simple to make. you need an empty steel food tin (washed carefully) with the top and base removed. I cut it open with tin snips/shears. Next I took two small size tent pegs and bent them in a vise into a triangle – these will form the handles so you are not dealing with a sharp tin amidst the heat! I folded the ends of the tin can around the tent peg on the side where the two ends meet, and hammered it so it made a good round shape around the tent peg, leaving about a centimetre (say half an inch) and drilled three holes and joined it with three pop-rivets. Complete the other end and voila – you have a luthier special tool bending iron backing strap!

luthier bending strap

Tomorrow is glue-up time!

Cheers
Jerry

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