Cutting the timber parts

It is best to have all the component parts of the pipes cut to size before assembly commences. The sides, fronts and centreboard pieces are cut from 4 mm. thick close-grained spruce, quarter sawn.  

Quarter sawn timber is best cut from a larger section using a circular saw in the manner shown in the diagram, so that the end-grain goes across the timber. This ensures that the wood is stable and will not warp or twist. Timber with tightly spaced grain without knots is best.  

Make up the various piece-parts         

The 4mm. thick sides are the width of twice the pipe depth plus 3 x 4 mm. The two fronts and the centreboard are cut from 4 mm thick timber to the width of the pipe. The foot piece and the blocks are cut to the same width from a single piece of hardwood stock, 10mm. thick, each block being slightly more than the depth of one pipe, plus 4mm. The foot piece is cut very slightly longer than the width of the double pipe and has a 10mm.hole drilled through it.

For the smallest pipe in the rank the hole is drilled halfway along its length. All the other pipes have a hole the same distance from one end as that in the smallest pipe. Thus, when the pipes are mounted in line, all the front faces of the rank will be in a straight line so that a single supporting strap can be fastened to each pipe.

German mouths or English mouths      German mouths have their top face sloping backwards from the pipe lips as in the diagram above. English mouths have the top face set square to the lips. I always make my double bourdons with German mouths as I fancy they have a somewhat richer sound with more partials, but English mouths would produce a perfectly acceptable tone. The blocks are cut from the 10mm. hardwood stock on the bandsaw, setting the angle guide square for English mouths or at 10 degrees for German mouths. The parallel fence is used as a gauge for the length of each piece in either case.

Double blocks – Jig for making them up    The centreboards are held standing on their edges by small wooden guide-blocks, hot-glued onto a melamine-faced board. The pipe blocks are then glued to the ends of the centreboards with PVA woodworking glue. The centreboard assemblies can afterwards be easily removed from the board without sticking.  

One of the pipe sides is laid flat and the front boards and foot piece are glued in position making sure the front pieces are at perfect right angles to the side. When the glue is set, the centreboard assembly is glued in position. The top point of each block should be exactly 30mm. from the base end of the pipe. This leaves a gap of 30mm. above each block, which will later be partially covered by the upper lip. Leave the pipe long enough for the glue to set.  

Glue second side on top and clamp Before the second side goes on top, paint the internal surfaces of the pipe with PVA glue thinned with a little water. Also paint the glue on the inner surface of the second side piece. Before this glue is dry, apply normal strength PVA glue to the edges of the fronts, centreboard assembly and foot piece, then press the second side into place. Then clamp the whole pipe body onto a flat board, wiping away any surplus glue from the exterior wood with a damp cloth. Leave each pipe for the glue to set and dry thoroughly.  

Trim all the exterior surfaces of the pipe by sanding any raised edges. The tips of the blocks and the foot piece should protrude slightly from each of the pipe-fronts. These should then be carefully ground level with the fronts using a disc sanding machine or a flat sandpaper board. The finished pipe body can then be given a first coat of varnish.  

Caps and gaskets Caps should be cut from hardwood. Each is 30mm high and cut to the overall width of the pipe. The top surface forming the upper lip has a 45-degree bevel on its outer edge. The cap is then placed on a sheet of thin cardboard to mark out the size of the gasket, which is cut with a craft knife. Cereal-packet cardboard is just about the right thickness The completed caps and gaskets are glued to the pipe body using Copydex. This is latex adhesive which forms a semi-permanent bond, but the caps can be easily removed if necessary. It sticks easily to the varnished surface of the pipe-body.  

Upper lips are made from similar hardwood to the caps. These are about 40mm. long and the same width as the blocks. They are bevelled to form a knife-edge. This edge should not be too sharp, but rounded slightly with sandpaper. It is most important to give a fine polished finish to the caps, blocks and upper lips to get the best possible sound from the pipes.  

The Stoppers are cut from 10mm. thick hardwood and trimmed to about 1mm. less than the internal dimensions of each pipe. A 6mm. hole is drilled through the centre and a short length of 6mm. dowel is glued in place. The edges of the stoppers are chamfered and rounded slightly before the small rectangle of chamois leather is glued, with Copydex - only to the bottom surface of the caps, not to the sides.

Round knobs, drilled to take the 6mm. dowel are glued on to finish the stoppers. I use the small turned-wooden polished beads recovered from those beaded car seat covers which seem to be no longer fashionable. 

Cutting and tuning If the dimensions of the pipes on the spreadsheet (below) have been adhered to, the pipes will all be rather longer than they need be to produce the desired note. The double pipes should be tuned one side at a time by covering the mouth of the opposite side. The upper lips should be temporarily held with an elastic band in the most favourable position to produce the best sound. The pipes can then be cut to length so that the stoppers are approximately 10mm. recessed into the top of the pipes. The upper lips are secured to the body of the pipe using Copydex. Pipes should always be voiced and tuned on the actual organ wind. Blowing by mouth is a useful test, but not accurate enough for anything but approximate tuning.  

Celeste versus Unda Maris If both sides of the double pipe are tuned exactly the same, they will sound the same note together, but rather louder than a single pipe. If one of the pipes is then tuned very slightly sharp, by pressing the stopper in a tiny amount, the pipe will then give a hollow, wavering note with an ethereal quality. This tuning is called Celeste, meaning “heavenly”. A distinct “beat” is heard, the speed of which depends on how much variation there is between the tuning of the pipes. A typical Celeste should have a beat of about half to a quarter of a second.

By tuning one of the pipes slightly flat, instead of sharp, the sound produced is called Unda Maris, meaning “Sea Waves”. Melody pipes are usually tuned Celeste. Unda Maris tuning is usually used for deeper Cello pipes in the accompaniment or the bass section of the organ.                                                    

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King Solomon double bourdon pipe dimensions:

LENGTH AT MIDDLE C = 28.00
WIDTH AT MIDDLE C    = 2.00
DEPTH AT MIDDLE C    =  2.60

WIDTH / CUT-UP RATIO  = 2.50
WIDTH DOUBLES AT 28.00 SEMITONES
CAP LENGTH  = 3.00
STOPPER LENGTH = 1.50