Last October (last October!!!!!!!!!!!!), when I said I planned to make the derrick functional on the Caldercraft puffer I'm building, Martin said he had hoped to do the same for Jan's "Highlander". He asked me how I planned to do it.
Herewith a progress report (if it can be called progress after all this time!).
There have been many periods of doing other things and several of giving up!
Step one was to make a mock-up to check feasibility - prior to purchasing FLJ's P44 devices to overcome the servo dead-band problem. I then spent an inordinant amount of time making the pulley blocks:
I naively thought that maintaining gentle tension on the lines for lateral boom movement would be simple! The current, elasticated, solution seems extemely crude - but how do you maintain even tension over a relatively long range of thread movement?
The final problem is finding suitable thread. So far, I have tried five. The ones that look best are not flexible enough to run freely through the blocks. The thin ones are too hairy.
There is great danger of a tangle occurring, out of sight, below deck. The winch will be a bit fiddly to remove.
The weight hanging on the boom is 4.5g so a slug of lead, weighing about 10g, inserted in the end, should ensure reliable operation.
I have completely given up trying to maintain tension on the secondary single line - it will just have to flap around in the breeze! (How was this used in real life?)
The project looks feasible - but only just!
Martin made the right decision!
Mike