Defying gravity

While on the subject of the apparently impossible, here’s another teasing puzzle that woodworkers can make to annoy their friends. It consists of 3 pieces: a cylinder, a symmetrical double cone and an inclined plane.

Surprisingly, placed together like this, there is no movement in either cylinder or cone. Wouldn’t you expect them to roll down the inclined plane?

The cylinder does, of course, roll down the plane but to take the photograph, I’ve used a ruler as a chock to prevent this happening.

The cone, on the other hand, has an inexplicable tendency to roll up hill. Once again, I’ve used a ruler as a chock to prevent it doing so.

These still photographs don’t really convey the anti-gravity properties of the double cone. For a more convincing demonstration, have a look at this video on YouTube.

Or, in case the link doesn’t work, paste this url into your browser: http://www.youtube.com/finelystrung#p/a/u/0/g7dCCskRMUg

Impossible objects

As you can see, I’m working on a cello at the moment. But I’ve written about cello making before and, rather than repeat myself, I thought that I’d show a few wooden constructions that have amused me recently.

First, an old favourite – but one that people who don’t know the secret find seriously puzzling – the captive screw. There a trick to its manufacture, of course, and, if you can’t work out how it’s done, this YouTube video explains.

Rather more sophisticated is this apparently impossible double dovetail. There’s no trick here and the joint comes apart with ease. It’s just that the geometry of the joinery isn’t what one assumes it to be at first sight. The joint is occasionally useful. Roy Underhill describes an application in his book, The Woodwright’s Guide (ISBN978-0-8078-5914-8), where it’s employed to join the front legs to the top of a work bench.

The triple dovetail below is an ingenious puzzle that I found in Edwin Wyatt’s book, Wonders in Wood (ISBN 0-941936-40-6). Wyatt says that it was invented by someone called A B Cutler and published in a magazine, Industrial Arts and Vocational Education in 1930. It has no practical application as far as I know. The geometry of the joint is a variation on that of the double dovetail but it’s rather harder to make. Again, despite all appearances, the two pieces come apart easily – as you can see if you compare the positions of the ebony dots in the two photographs.

In a future post, I’ll show some photographs of the joints pulled apart.

Making rosettes for a classical guitar (4)

All that remains at this stage is to cut the inner and outer circles to make the annulus of the rosette. I start by drilling a hole in the centre of the work piece…

… and then use a Dremmel mounted in a shop-made jig to cut the circles. (More details of the jig are available in the ‘Tools and Jigs’ section of this site.)

Here are the two rosettes that I’ve talked about in early posts in this series cut out.

And here are a few more. Going clockwise from top left, they’re made of English yew, laburnum, spalted beech, spalted crab apple and mulberry burr.

It’s probably best to leave them attached to their base until you’re ready to install them on the soundboard but, as you can see from the two rosettes at the bottom, I don’t always heed my own advice.

Making rosettes for a classical guitar (3)

The rosette below is made from laburnum, arranged to show the striking contrast between the light coloured sapwood and the dark heartwood. It’s rather more complicated to make than the spalted beech rosette shown in the previous post and a fair degree of accuracy is needed throughout.

The starting point is a small piece of laburnum. This one has been air drying for a couple of years and I reckon that it should be pretty stable by now. I’ve scraped off the wax that covered the endgrain while it was drying.

The first step is to decide how many individual sector shaped pieces to use to complete the circle. I’m planning to use 20 for this rosette, which means that the sides of the billet must be planed to converge at an angle of 18°. That’s hard to manage on the bench top and it’s worth making a cradle to hold the wood while you plane it to size and shape. Go slowly and carefully because it’s important not only that the angle is right but that there’s no taper along the length of the piece. In addition, the width must be right so that the line between the sap wood and the heart wood ends up where you want it to be in the finished rosette.

Having planed the wood to a near perfect prism, it’s sliced on the bandsaw.

The pieces are numbered as they come off, so that they can be put together again in consecutive order.

Here the rosette is being assembled ‘dry’.

It may be necessary to make some fine adjustments with a shooting board and a block plane.

Here, the first piece is being glued and clamped into position on its plywood base. The base has been marked out in pencil to aid positioning of the individual pieces.

As the pieces are glued into place, the rosette nears completion.

Cleaned up and levelled with a finely set block plane.

Making rosettes for a classical guitar (2)

One of the rosettes is going to be a replica of the one used for the zebrano guitar that I made last year from this remarkable lump of spalted beech.

I used a bandsaw to cut 2 thin (3mm) slices …

… and trimmed and book matched them to create a symmetrical pattern.

A card with a rosette shaped cut out helps give an idea of what the finished rosette will look like.

I use veneer tape to keep the two pieces in registration while they are glued to the base that I described in the previous post.

Clamping up.

Out of the press and ready to be planed flat and cut into shape. The veneer tape comes off easily if a little hot water is brushed on.

The next post will be about the construction of a different sort of rosette.

Making rosettes for a classical guitar (1)

Last July I wrote a couple of posts about making a guitar rosette from spalted beech. But I missed the opportunity to photograph some of the details of its construction and, since I’ve been making some similar rosettes recently, I thought it might be useful if I had a second attempt at explaining the method.

For reasons that I’ve discussed before, I like the visual effect of rosettes made by inlaying wood with contrasting colours or a striking figure and often use this technique when making guitars.

These rosettes are made from at least 2, and usually many more, individual pieces and I’ve found that it’s much easier to assemble them accurately on a base of thin birch plywood (0.4mm or 0.6mm thick*) than it is to inlay them directly on the soundboard. Because the plywood is so thin, it too needs a stable base during the assembly process. But, of course, it must be possible to remove this base when assembly is complete. I start with a square of 6mm MDF, a similarly sized sheet of clean paper and the square of  plywood that will be the permanent base of the rosette.

One surface of the square of MDF is given a thin coat of hot hide glue.

The sheet of paper is then smoothed down…

…before adding a second coat of glue…

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and the layer of plywood.

The whole thing is then clamped up in a nipping press and left to dry overnight.

If you don’t have a press, a flat board and a weight work just as well.

The point of the paper and the hot hide glue is that, after it has been assembled, the rosette is easy to detach from the MDF base. In another post, I’ll show the next stages of the process.

*This sort of plywood is used by model makers and, at least in the UK, is easily available from the sort of shops that supply materials for people who build model aeroplanes.

Last instrument of the decade

Below are a couple of photographs of my last instrument of the noughties, a copy of a violin made by Guarneri del Gesù in 1742. It’s very slightly smaller than the original with a body stop of 190mm, and a string length of 320mm. I think it’s going to be a powerful instrument but it will be a few weeks before it gets a proper trial because the violinist for whom I made it recently broke her right arm – unpleasant enough for anyone, but doubly unfortunate for a string player.

Dovetail marker

Another useful aid to cutting dovetails is a dovetail marker. Several different designs are available to buy but I like this shop-made one best. Once again, it comes from Robert Wearing’s book, The Resourceful Woodworker (ISBN 0 7134 8006 8), and is fairly easily made from a sheet of brass 1 to 2 mm thick. Its advantage over the type that Lie-Nielsen and Veritas make is that you only have to set out the centre position of the pins on the edge of the board. The triangular ‘window’ of the marker then lets you see exactly where you’re marking out the joint. It works equally well whether you prefer to cut the pins or the tails first – an argument that I don’t intend to get into.

I suppose purists who like to use a steeper slope for dovetails in softwood would need two markers, one at a 1 in 6 slope and one at 1 in 8. I confess that I never bother about this, cutting all dovetails at 1 in 8, regardless of what sort of wood I’m working with.




Dovetail vice

I’ve been making a few small wooden boxes to give as Christmas presents. They don’t really have much practical function, except as a place to keep pencils or stamps or other odds and ends, but they’re fun to make and people seem to like them. Part of the pleasure of constructing them comes from the small scale of the project. It’s a day’s work rather than a month for a guitar or a violin. And they allow you use up scraps of wood that were too nice to burn but that are too small to make much else out of. They also provide an opportunity to show off a bit, which brings me to the reason for writing this post.

Even people who know nothing about woodwork and cabinetry have heard about dovetails and recognise them as an emblem of craftsmanship in wood. So that’s the method of construction you should use if you want your skill to be noticed.

If you’re going to cut dovetails, it’s much easier if you’ve got a proper vice. Because of the position of the screw and slide bars in most bench vices, it’s only possible to grip the edge of the board that you’re dovetailing. A dovetailing vice, on the other hand, grips the whole work piece, preventing it vibrating and aiding accurate sawing. They are especially valuable for wide boards but they’re good for smaller pieces too. The idea came from Robert Wearing’s book, The Resourceful Woodworker, (ISBN 0 7134 8006 8). He uses threaded metal bars to provide the clamping force but I cannibalised the wooden handscrews from an old clamp that I picked up in a second hand tool shop. The vice is simply cramped to the top of the bench when needed.

I left the screws much longer than necessary for any dovetailing so that the vice would open wide enough to accommodate the body of a guitar when working on the tail stripe.

And, should you be wondering how the boxes turned out, here are a few photographs:


Tartini Adagio

A few weeks ago, I dropped in on the Tartini ensemble during a rehearsal in St Mary’s  church, Penzance. They were preparing for a concert of music by Dietrich Buxtehude and Jan Adam Reincken. And a very interesting and exciting concert it turned out to be:  music by two composers whose work is heard less often than it deserves to be, with brilliant performances on period instruments by the ensemble.

Here’s a photograph taken during the rehearsal.

It was also the first outing for the baroque violin that I wrote about a couple of posts ago.  After the rehearsal, Pamela Rosenfeld played this adagio by Tartini on it, accompanied by Nigel Wicken on a chamber organ.

Tartini adagio

Patrick Gale’s cello

Patrick Gale, who commissioned the baroque cello that I completed earlier this year, spoke  about why music was important to him in a recent broadcast on  BBC Radio 3.  If you missed his  brief and amusing  talk,  you can listen to it  here for the next few days.

Pamela’s violin

Back in May, I wrote about making a baroque violin, a loose copy of the Charles IX violin of 1564 by Andrea Amati, now in the Ashmolean Museum, Oxford. After it was completed, and while still in the white, it went off for a short trial by the violinist who had commissioned it and, having been approved, came back to be varnished. Varnishing is now finished and the fiddle has been set up again just in time for its new owner, Pamela Rosenfeld, to play it in the Buxtehude festival in Cornwall later this month.

Below are a few photographs of the completed instrument.

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Playing the zebrano guitar

The zebrano guitar has now been collected by its new owner, Dave Crispin. He played it for a while before taking it away, and allowed me to capture a few minutes on a pocket recorder. The recording isn’t very good, I’m afraid, because the microphone is positioned much too far away from the instrument, but Dave has promised to come back for another session after he has had a chance to get used to  his new guitar and when I have worked out a better recording system. In the meantime, here’s a taste of the sound it makes.

Either click on the blue labels to download them to your own media player, or simply start the audio player in the bar.

Dave trying out his guitar for the first time

Dave improvising on the new guitar – with a bit of help from Jamie in the background

Capo for lap steel guitar

A while ago, friend bought himself a lap steel guitar – the sort with a hollow neck, square in section – but became frustrated because he couldn’t find a capo that would fit it. He couldn’t use the usual type of capo, of course, because the hollow neck of the guitar was too thick and too fragile to allow the clamp to work and because the strings were too high over the fingerboard. So I made him this device, which is easy to fit and adjust and works well.

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In case anyone else has a similar problem, I thought it might be worth explaining how it’s made. You’ll need a scrap of hardwood roughly 2.5 x 1 x 3/8 inches in size; a piece of bone or ebony to make the inverted nut; some cork or leather to damp the strings on the headstock side of the capo; a 2.5 inch length of round bar in brass or steel of 1/4 inch diameter; a short length of threaded rod of 1/8 inch diameter; and a small piece of wood or metal or plastic to make a knob with which to turn the threaded rod. You’ll also require a matching tap to cut a thread in the hole of the brass bar.

The photographs below should make the construction clear, so I’m not going to give details. If you have any queries, please email me at info@finelystrung.com. The only thing to watch out for is that the threaded rod that pulls the bar against the underside of the strings shouldn’t be too long or it may damage the fingerboard.

To fit the capo, loosen the screw holding the metal bar – but not so far that the bar becomes detached. Hold the capo with its long axis parallel to the strings and insert the bar between the two middle strings. Then rotate both the capo and the bar through 90 degrees, making sure that the nut side of the capo is orientated to face the bridge. Slide the capo to the desired position and screw it up just tightly enough to produce a clear sound from all the strings.

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Zebrano guitar

The guitar that I have been writing about in my last few posts is now, more or less, completed. It’s finished with French polish, which will benefit from a final burnishing in a couple of weeks time when it has got fully hard. But I couldn’t wait any longer to string it up and hear how it sounds. The back and ribs are zebrano and the soundboard is European spruce. The binding is Rio rosewood and maple, and the soundhole rosette and headstock veneer are spalted beech. I’m pleased with how it has worked out, though perhaps I got carried away when it came to the rosette, which might have been more elegant if the diameter had been a little less. Below are a few photographs of the completed instrument.

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