[UK-CONTEST] Stub mast

[johndunnington]

Hi Steve & John
Approx 5M x 65mm OD thick wall high-grade aluminium (can't recall precise
wall size but something like 6mm), inside this is sleeved a 5M x 48mm OD
again, with thick wall.

Snap Steve with one change I added a length outside the 65mm OD which runs
from the rotator clamp up through the head unit and extends to the position
at which the lower antenna is mounted. Of course you then need a really good
thrust bearing and a HD Head Unit to complement the EHD Tower which goes
with saying John.
We had to increase the hole sizes on the head unit seem to think it ended up
at 70mm OD tube with 74mm diam holes.holes for good clearance. You can get
very high quality grade tube but talk to the supplier about the requirement
only snag it is not cheap but you sleep better at night.

In my case to accommodate the 10m GB5HQ  stack I extend the whole 65mm OD
with another 5m length bit without the internal sleeve. In yesterdays (and
previous) 40+ MPH winds with just the Cushcraft X-7 on board mounted 3ft
above the head unit,  the extension (9m - 1m inside head) just stood there
and didn't even sway. Several times since the IARU  we have had 35+ MPH with
gusts at  up to ?? with the stack on board and no problems. Plan is to mount
the WARC 30-17-12 spider above the X-7 when I get it finished. I will then
guy the tower for more peace, and perhaps add a set of light ropes under the
WARC Beam more to take the strain during lifting than guying.


May interest you that at the coast we had an M2 4-ele wide spaced 20m and 4m
above that the 3-ele Lin Loaded 40m. The stub used there was a single 6m
length of  65mm OD 10mm wall steam pipe which after 10-years developed a 2-3
degree set. Out there it never stopped blowing and several times a year
severe gale or even storm force winds are encountered. You needed a forklift
to move that pipe and a good set of tower ropes

John G3LZQ