Details of the "key-hole" attachment between the main-pole and axle frame are given in Figure 6.  This design enables the pole to be quickly inserted, then twisted and captured by the key trapped between the boards bolted onto the axle-frame.

Materials used are inexpensive and easy to obtain in a DIY Store: Overall budget of £25.

A length of 35mm diameter pine dowel, or heavy wooden curtain rail makes the main-pole.  The tie-struts can be made from two lengths of broom-stick with 3 inch vine-eyes inserted into the ends to take the butterfly-nut attachments.  The vine-eyes need to be fitted with care to avoid splitting the tie-strut ends.  It is best to fit a ferrule over the ends before drilling a pilot hole and screwing in the vine-eye.  A short length of 22mm copper tube makes an ideal ferrule.  See Figure 6 for detail.

This modification works well for me .... which is just as well as Diana scolded me when I was caught in the act of sawing off the top of the manufacturer's boat-bars!

If you adopt another modification be sure to keep a solid barrier between your boat tubes and the trolley wheels, or you will be back with punctures, this time caused by friction burns.

R. John Blake

Figure 5 - Details of keyhole attachment

Figure 6 - Details of vine-eye screwed into end of