Building aviolin

he previous article saw the preparation of the blocks prior to the fitting of the first set of ribs — those at the centre bout of

the violin. By now you should have something resembling photo 2; note that, as mentioned earlier, the outer curves of the corner blocks have not as yet been cut away.

TWe are now going to need a device for

bending the ribs. Photo 3 shows my ancient but trusty bending iron, and fig. 1 shows the essential dimensions for those who wish to build their own. I am at present trying to obtain a supply of the more essential tools, so anyone who needs advice, please write, enclosing an SAE for a price list of the tools currently available.

Before starting to bend wood, a set of clamping blocks are required. See fig. 2 for the shapes required. Note that the blocks for the centre bout must be made from some suitable hardwood — mine

Photo 2. Mould, with blocks ready to accept centre bout ribs

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are Beech — and they do not require aleather or cork sheet facing as the other blocks do.SteamingOnce the blocks have been made up, we are at last ready to begin. The general principle of rib-bending is to introduce steam to the area requiring bending, thento gradually induce the bend into the rib while continuing the steaming. The next step is to remove the steam, while holding the shape against the hot iron. This sets the bend, which should — if done correctly — maintain the shape required.

In practice, the curvature does tend toslacken off after a while, especially at the tighter curves of the corners, so it is advisable to glue the ribs in position as soon as they are bent.

I always find that the ribs retain their shape much better if the use of steam is kept to a minimum. It is often possible with a mildly figured wood to bend the ribs completely dry — at least, in the case of the convex areas of the upper and lower bouts — though it is probably wise to use steam at least for the first few times!

Initially, we are going to estimate where to make the first bend. This is going to be a tight bend, which will be cut in two, giving the beginnings of the centre bout bend, at the lower corner block, and the corner bend of the lower bout: x and y respectively on fig. 3.

Once we have this tight bend, it will not be too difficult — well, not impossible! — to continue the curve for the centre bout lower corner.

The reason for bending before cutting the rib pieces in two is that it’s very difficult to introduce a bend at the end of a strip. This way, there will be enough material to make the upper bend to the centre bout.

Where to bend?So where will the centre of the first bend be? Iestimate this by allowing about 5mm extra at the centre of the bottom block, then lightly bending the strip by hand around the mould to the corner block; I then give about another 10mm, marking a vertical line across the rib strip. It also helps to mark this position on the top edge of the rib strip, as the vertical line will of course be hidden by the iron while the piece is being bent.

Before bending, just check that you are leaving enough wood for the centre bout; there should be plenty with the average lengthof rib supplied.

Now we are ready to go — the boatshaped clamping blocks and G-clamps (opened out sufficiently) should be readily to hand, the glueshould be put on to the heat, and the bending iron should be switched on.

TemperatureThe temperature should be hot enough toturn a drop of water instantly to steam, butnot so hot that the drop dances about on thetop of the iron. If the water droplet just sitsand then boils up, a little more heat will berequired. Try it — you will see what I mean.

To be on the safe side, try holding a scrap of wood hard against the iron for about half a minute: if there is any sign of browning, then the iron is too hot. On my iron, I have the temperature control set half way, but you will have to experiment for yourself.

You will need a jar of clean water, and a strip of cotton sheeting for the steam: a little wider than the ribs, and about 200mm long. Don’t use synthetic or coloured fabric: melted-on fabric does not enhance the looks, and nor does a coloured pattern printed on to the finished ribs!

First of all, lay the rib on the bendingstrap, with the outer side facing you, andwith the line for the centre of the bend at themid position of the strap. Soak the fabric,gently squeezing out the surplus. Fold overto halve the length and double the thickness,and place over the area of rib to be bent.

Holding the strap firmly, and keeping everything level to avoid a twist developing, bring up to the hot iron, and let the steam penetrate for a few seconds before beginning to introduce the bend. It is important to maintain a strong tension to the strap — imagine a bullworker! — but do not pull the ribhard around the iron.

Gradually let the bend increase, and then pull around the tightest curve on the iron. If necessary, wet the cloth again.

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Photo 1. Finished ribs ready to be bent

In part 4 of his series, Dominic Excell looks at bending and fitting the

centre bout ribs to the blocks, and preparing for the upper and lower

bout ribs.

Photo 3. Bending iron and strap

Remove the cloth and repeat the above procedure dry, holding the curve finally for about 15 seconds. Make sure that both ends ofthe rib are in line with each other, otherwise the bend will not be vertical. Remove the rib from the iron. The curve should stay put, though it will slacken off a bit. If it springs out flat, you have used too much water, and you will have to hold the bend against the iron to dry it out while maintaining the shape. If the ribsnapped, there was not enough steam, too coolan iron or not enough support from the strap. Too much working on the iron also makes the wood brittle.

Once this first bend is set, cut along the marked line, which should be at the centre of the curve. Set the lower section aside for later use.

Hold the centre rib to the mould and see if the curve needs any further bending— adjust it if necessary. Make sure that the rib overhangs the point of the block by about 5mm, and estimate the position for the centre of the curve for the top corner. Mark this pointon the top of the rib, steam and bend as before— but keep the steam away from the first bend, as we don’t want it straightening out.

This will be trickier than before, because thefirst bend will get in the way, but have patience— you’ll get there!

Once the rib fits both corner blocks simultaneously, and follows the line of the mould, mark the outer extremities of the blocks onto the rib. Mark another line, parallel, but 4mm further out. Now trim back to this line, finishing by planing square. Check this by standing the mould on your base board.

Trimming and fitting The clamping block, having the angledfaces also square, should ensure an evenpressure of rib to corner blocks. If the rib fitswell at the top of the block — say — butthere’s a slight gap at the bottom, then theplane can be used to pare off a little from thetop end of the rib, ensuring an even fitoverall.

When you are satisfied, coat the mating surface of the blocks with hot glue (no, not the modern variety out of a glue gun!). Spring the rib in position, making sure you have the marked lines coinciding with the block ends and the ribs sitting right

Trying the rib against the mould

down on the board; now clamp up. Use the minimum pressure possible, so as not to bend the ends of the ribs back on themselves, though you must make sure that enough pressure is used to squeeze out the surplus glue.

For all gluing operations, make sure thatyou are in a warm, draught-freeenvironment. Once the glue is applied, bringtogether the surfaces to be glued straightaway. If necessary, have a dry run first, asspeed will be of the essence — though ofcourse there is no need to panic!

Now repeat the exercise for the other side. Remember to scrape away surplus glue as yougo along, as it helps to keep the work clean, and the glue is very brittle when it has dried. Leave the piece overnight to dry and to reach its maximum strength.

The next stage is to continue the marked outline from your template, so that it bisects the outer surface of the centre bout rib. See fig. 4. Use the compasses again to ensure symmetry, just as you did when marking the outline onto the corner blocks. Make sure that the curve maintains its direction right up to thepoint where the line crosses, and at that point mark a fine perpendicular line from the board. Check again with the compasses, and then chisel back to that line, so that the rib end is squared off and truly vertical. Now comes the exciting bit!

The exciting bit... We have to use the gouge, as on the centre bout face of the corner blocks, making sure everything is to the line, and vertical. This means that the centre rib finishes as a razor edge — see fig. 5.

It is vital that this face you are about to gouge remains concave right to the very end, and that you do not allow this rib end to become shortened at all. The point (sorry!) of this is that the join should be on the corner of the ends of the ribs, and is thus invisible. It is also stronger, as the surface area between thetips of the ribs is greater than it would be if the joint ran down the centre of the visible end. This is a tricky task, I won’t try and fool you into thinking otherwise, but every violin maker has to do it for the first time. Work carefully, be confident (but not overly so!), andabove all have a very sharp gouge (fig. 6).

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Outer curves of corner blocks marked out

Trimming the rib end — checking for vertical

It pays to work in the right sort of light.I try to arrange my schedule so that I do thisjob in the evening, in the dark except for asingle anglepoise lamp. I can arrange this sothat I light up the endgrain of the rib, so thatwhen this disappears, I know I have gone farenough.

I also find it easier to work horizontally. Idon’t mean that I am lying down, but that Ihold the work up against the side of the bench,and use the gouge in the horizontal plane. Ifind that this gives a good deal of control,especially in the final stages.

Next month, I will be showing you how to finish the ribs and to fit the linings. In the meantime, if you have managed to keep up with me, well done. Protect the razor edges over which you have taken so much care at allcosts!

If you would like to order any plans or a materials price list, or you wish to enquire about tuition, please write to Dominic Excell care of The Woodworker enclosing an SAE, please.

Close up of finished rib / corner block,ready to accept lower rib

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