Power Predictor
A 12m mast made using two 6m aluminium scaffolding poles.
Watch the video:- http://www.youtube.com/watch?v=MF5rmF_0zYw
Disclaimer: This mast was erected on 4th October 2010, so experience is limited.
Two 6m aluminium scaffolding poles (1.7kg/m)
One joining piece to connect the two tubes end to end,
One 4m steel pole (4.4kg/m)
One clamp to attach it at 90 degrees to the aluminium pole.
Total cost £60 from http://www.stlscaffolds.co.uk/
140m of 10mm polyester rope £20
3 large stakes and 3 small stakes £20
1.
A model was made using canes and string to prove the concept.
2.
Aluminium poles were chosen -otherwise the mast would have been too heavy to lift.
3.
A steel pole was used as the erecting lever, and its extra weight helped as a counterbalance.
4.
Measure 12m diameter circle and marked stake positions at 120 degrees with one in the
prevailing windward direction.
5.
The three main stakes were driven into the ground at about 60 degrees to resist the tension.
Wind
Direction
Colin Townend
Teal Ltd
07825 702020
[email protected]
6.
The site was checked for levelness so that all the rope lengths could be the same.
7.
It was decided to tie one guy near the top of base pole, and 1/3 up the top pole so any single
rope failure might be survived.
8.
With the pole laid on the ground and a mark made 6m from its base to represent the stakes,
the ropes were knotted to the mast and extended to the 6m mark in the ground.
9.
A Rolling or Stopper Hitch or stopper hitch was chosen.
http://www.tpub.com/content/armyengineer/en0562a/en0562a0171.htm
http://www.proknot.com/html/rolling_hitch.html
Stopper hitch
http://www.tpub.com/content/administration/14067/css/14067_61.htm
Colin Townend
Teal Ltd
07825 702020
[email protected]
10. A tape marker was wrapped round each rope at the mark and then an extra 1.2m was added
(for tying to the stake later) and the ropes cut.
11. The leeward side guy ropes were tied to the stakes using the tape markers to make them all
the correct length.
12. Using a right-angle scaffolding clamp, the steel pole was fixed to the base of the mast.
13. The windward guys were temporarily tied to the lever arm together with a pulling rope.
14. Two small stakes on the windward side of the mast were used to guy the lever arm and keep
it upright during pulling. (they would over-tighten on the leeward side).
15. The base of the mast was tied to an anchor stake to stop it being dragged when the lever was
pulled.
16. A trial lift was made with only the bottom aluminium pole on its own. That allowed me to
confirm that the bottom pole guy ropes were tied to the stakes at the correct length.
17. The top pole was then reattached with the clamp and the whole mast assembly was lifted
18. As the mast was pulled up into the wind, the slight cross-wing pushed the mast to one side
tightening the guys and stabilising the pole.
19. Without that helping wind there would be a danger of the poles hinging in the middle.
20. Some helpers could make sure the guys were tight as the poles rose up, but more people
mean more potential for injury. Perhaps making sure the wind is in the right direction is the
key?
21. Once erected the guys were transferred from the lever arm to the windward stake, and all
tensions were adjusted to straighten the mast.
22. Watch the video:- http://www.youtube.com/watch?v=MF5rmF_0zYw
23. The mast was erected on the 4th October 2010, so there is not much experience of its
durability yet, but it is still standing four months later and has recorded 16.5m/s (37mph)
winds. Since that figure is averaged over 10 seconds, it must have seen higher gusts.
24. I have single-handedly raised and lowered the mast a couple of times to rectify water ingress
in the electrical connections, and am now more confident that it is quite stable when lifted
into the wind.
Colin Townend
Teal Ltd
07825 702020
[email protected]
25. The clove hitches securing the guy ropes to the ground stakes are checked weekly and have
needed tightening only once – after a gale.
Jan 2011.
Colin Townend
Teal Ltd
07825 702020
[email protected]