0.125" wall is only 1/8", I'd be a little concerned about the strength.
You may look at taking the existing 0.125 wall tube and using it for the top
section by finding a 0.250 wall tube or greater on the lower section. An insert
I think would be required at the joint, say 2-3' into each section. You may
have to sleeve the lower section for a firmer fit at the joint.
From your description, it doesn't IMHO appear to be all that big.
Fred KC5YN
On Monday, March 19, 2018, 9:10:44 PM CDT, Shawn Donley <n3ae@comcast.net>
wrote:
My instincts tell me this is a bad idea, but perhaps others have done this
successfully. I currently have an OB9-5 HF yagi (spec 7.8 ft^2 projected area)
mounted one foot above the top of my tower. The mast is 2 inch OD steel DOM
with 5 ft inside the tower to the rotator and 7 ft above the tower. Can't find
the mast wall thickness at the moment but I think its 0.12 inches. Thrust
bearing is at the top of the tower. I'm considering adding a 40M rotary
dipole (3.4 ft^2) above the yagi. But I need to place it at least 10 ft above
the yagi to minimize coupling, plus I need 3 ft above the dipole for the dipole
truss bracket. That means I need 13 ft "more" mast. Is it possible to splice
an additional 13 ft of DOM onto the existing mast using a steel structural tube
inserted inside the mast pieces and bolted through the masts? If so, how long
should this joint tube be? The tower is a crank-up so I can work up there
comfortably with a man lift when it's cranked down.
tnx for your thoughts.
N3AE
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