1. Making a Tarhu Cone

Tarhu cone design has gone through several different phases. From 1995 until 2004 large and small tarhus all shared the one design concept. From 2004 until 2016 large and small tarhus diverged, with two different designs being employed. In 2016 a new design developed, using a low-stiffness curved cone which produced good results in tarhus of all sizes.

At the present time (early 2018) the proportions being used between height:width in all cones is 1:7. In the example used in the photographs below, the cone is 27mm high and 189mm wide (it is a tarhui cone, same size body as a nak tarhu).

This article outlines one method of making a curved cone of the new design. It uses very thin strips of western red cedar (0.7mm) which are bent to shape using dry heat. The individual cone segments are glued together using tightbond glue. The joints between the segments are unreinforced butt joints.

Two moulds are needed: a mould which is used to accurately trim the bent cone-segments to the desired angle; a turned mould which is used to assemble the trimmed segments into a cone shape.

A template of the desired cone shape is used to set out the moulds.

 1. The assembly mould has been turned on a lathe then marked out in 12 segments of 30 degrees each.

1. The assembly mould has been turned on a lathe then marked out in 12 segments of 30 degrees each.

 2. A block of cherrywood has been marked out with a 30 degree wedge

2. A block of cherrywood has been marked out with a 30 degree wedge

 3. The wedge has been cut out using a bandsaw

3. The wedge has been cut out using a bandsaw

 4. The wedge is planed flat, making sure it is an accurate 30 degrees

4. The wedge is planed flat, making sure it is an accurate 30 degrees

 5. The offcuts are kept so that........

5. The offcuts are kept so that........

 6. One of the off-cuts can be taped back on to the wedge so that the wedge centreline is parallel to the bandsaw table

6. One of the off-cuts can be taped back on to the wedge so that the wedge centreline is parallel to the bandsaw table

 7. The cone profile is traced onto the wedge from the template

7. The cone profile is traced onto the wedge from the template

 8. The wedge is ready to cut exactly along the drawn line (careful - no clean up of the bandsaw cut)

8. The wedge is ready to cut exactly along the drawn line (careful - no clean up of the bandsaw cut)

 9. A piece of cardboard is clamped between the 2 sections of the trimming mould and the shape is traced.

9. A piece of cardboard is clamped between the 2 sections of the trimming mould and the shape is traced.

 10. Assembly mould, trimming mould and rib template

10. Assembly mould, trimming mould and rib template

 11. A block of quarter-sawn western red cedar is sawn into strips 1.0mm thick

11. A block of quarter-sawn western red cedar is sawn into strips 1.0mm thick

 12. Each strip is long enough for 2 ribs, so 6 strips are needed.

12. Each strip is long enough for 2 ribs, so 6 strips are needed.

 13. An adjustable drum sander is used to thickness all of the strips

13. An adjustable drum sander is used to thickness all of the strips

 14. All strips are thicknessed to 0.7mm

14. All strips are thicknessed to 0.7mm

 15. The strips have been cut to length and marked out with the rib template

15. The strips have been cut to length and marked out with the rib template

 16. The 12 rib-blanks have been taped together then cut on a bandsaw. Cut about 1mm outside the line

16. The 12 rib-blanks have been taped together then cut on a bandsaw. Cut about 1mm outside the line

 17. All ribs cut out and ready for bending

17. All ribs cut out and ready for bending

 18. A simple bending iron using a piece of iron pipe and a gas burner

18. A simple bending iron using a piece of iron pipe and a gas burner

 19. Each rib is pushed against the pipe until the desired curve is reached

19. Each rib is pushed against the pipe until the desired curve is reached

 20. All ribs bent ready for trimming

20. All ribs bent ready for trimming

 21. Each rib is squeezed between the two halves of the trimming mould

21. Each rib is squeezed between the two halves of the trimming mould

 22. The rib is trimmed by holding a small plane against the bottom half of the mould 

22. The rib is trimmed by holding a small plane against the bottom half of the mould 

 23. The rib is now flush with the bottom section. Note that the width of the upper section of the mould has been trimmed around 2mm so that it doesn't interfere with the trimming

23. The rib is now flush with the bottom section. Note that the width of the upper section of the mould has been trimmed around 2mm so that it doesn't interfere with the trimming

 24. The trimmed ribs can now be assembled. Masking tape is used to hold them together

24. The trimmed ribs can now be assembled. Masking tape is used to hold them together

 25. Half way!

25. Half way!

 26. All ribs assembled. The last rib usually has to be fitted individually. It is better to leave it untrimmed in case more width is needed

26. All ribs assembled. The last rib usually has to be fitted individually. It is better to leave it untrimmed in case more width is needed

 27. The tape has been removed and the cone lightly sanded. A 16mm disc of western red cedar has been glued onto the apex of the cone. Cone plus disc weighs 15gms

27. The tape has been removed and the cone lightly sanded. A 16mm disc of western red cedar has been glued onto the apex of the cone. Cone plus disc weighs 15gms

 28. A cone stabiliser has been glued onto the edge of the cone. The stabiliser is made from 13mm pine plywood

28. A cone stabiliser has been glued onto the edge of the cone. The stabiliser is made from 13mm pine plywood

 29. The finished cone has been stained black ready for mounting in the instrument

29. The finished cone has been stained black ready for mounting in the instrument

Peter Biffintarh