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[W1MOW]

Have you run any of these ideas through your local building department? Due to the close proximity to your neighbors, I would ask them before doing anything.

You mentioned placing the base of the mast/rotor ontop of your patio cover, what is it made of?

Gary P.E. W1MOW

My neighbors are cool with my antennas. I've had various antennas for 20 years. The patio cover uses three 4X4 vertical supports with a
 4X8 truss connecting them at the top and sixteen 2X6 rafters fastened to the side of the house and the other ends fastened to the truss. The top is an array of 2X2s  with 2" spacing. It is a sturdy structure.

While it's great that you neighbors don't mind your antennas. If one should come down and damage your neighbor's property, without the proper due diligence you could find yourself on the wrong side of both your insurance company and the city. A little now could save major headaches down the road.

Be smart and do it the right way.

Gary P.E.  W1MOW

[AA7IS]

same amount of mast above the thrust bearing as below it.

[W3LFR]

Have you run any of these ideas through your local building department? Due to the close proximity to your neighbors, I would ask them before doing anything.

You mentioned placing the base of the mast/rotor ontop of your patio cover, what is it made of?

Gary P.E. W1MOW

My neighbors are cool with my antennas. I've had various antennas for 20 years. The patio cover uses three 4X4 vertical supports with a
 4X8 truss connecting them at the top and sixteen 2X6 rafters fastened to the side of the house and the other ends fastened to the truss. The top is an array of 2X2s  with 2" spacing. It is a sturdy structure.

While it's great that you neighbors don't mind your antennas. If one should come down and damage your neighbor's property, without the proper due diligence you could find yourself on the wrong side of both your insurance company and the city. A little now could save major headaches down the road.

Be smart and do it the right way.

Gary P.E.  W1MOW

Absolutely! That's another reason I wouldn't mount it alongside the walkway between houses. If it came down, there's a fence to stop it, but why take chances.

[K6BRN]

Regarding mast material - for a long (10 feet or more) unguyed/unsupported, heavily end loaded rotating mast section:  Avoid aluminum tubing, regardless of its tensile strength or wall thickness.

The issue is stiffness.  Aluminum is many times more flexible than steel and is prone to aeroelastic flutter when the mast is long and  top-loaded.  Flutter manifests as a gyrating bend in the mast that rotates around it's axis.  Essentially, at a certain set of (even modest) wind speeds the mast can whip around in an ever widening circle at the top, potentially destroying itself and/or the antenna.  Hard to predict, better to be safe.  Happens in some installs and not others.

Steel is a much better choice.  And if high tensile strength steel is not used (HTS steel is very stiff and is by far the best choice) and common galvanized water pipe is chosen instead, it can be strengthened/stiffened by insertion of a second, smaller diameter galvanized steel pipe inside the first, using wrappings of duct tape to form "donut" spacers every 12 to 14 inches - and then securing its position using a bolt driven through both pipes.  The inner pipe does not even have to be the same length as the outer, but it should at least extend down half of the unguyed/unsupported mast section.  This serves not just to strengthen the mast, but as a bending motion damper during strong wind gusts, which is what usually destroys a mast.   A "Hammy Hambone" solution, but it does work - up to a point.

Regarding building the mount into a wooden structure - be aware that a long mast "working" back and forth in the wind can and will over time loosen and pull nails and even decking screws free.  The structure must be well bolted together at all points, using (many) at least 1/4 inch bolts and broad flat washers on both sides.  Even then, the mount will need to be periodically inspected and checked for bolt loosening/wood compression and splitting.  A wooden mount has to look very "overbuilt" to safely stand up over time and MUST be periodically inspected.

Some thoughts from actual experience...

Brian - K6BRN

[KH6AQ]

Mast ideas

Plan 'B'.... use sched 80 Galvanized water pipe.  BTW, tensile strength does not enter into the equation, only the yield strength.

Another option would be to use 2.875" OD galvanized water pipe, in either sched 40 or sched 80.  In sched 80, it's .276" wall thickness.

Bending moment =  yield strength X section modulus of the pipe / tubing.   Bigger diameter + thinner wall has a lot bigger section modulus  vs  smaller OD and a thicker wall.

EG: 3.00" CM tubing with a .25" wall  has a much bigger section modulus   vs a 2.00" OD CM tube, with a .375" wall. IF both have the same yield strength, the 3" tubing wins  hands down.  But both weigh the same, and cost the same. 

Water pipe is typ 35-36 ksi yield strength.   CM is typ 105-120 ksi yield strength, but only if heat treated. Un heat treated CM is only 70 ksi yield strength.   Aluminum is typ 39/40 ksi yield strength.  (6063-T832 / 6061-T6/T8).   Galvanized DOM tubing is yet another option..and is typ 75-87 ksi.

As you can see, the stronger alloys are a helluva lot stronger vs  35/36 ksi water pipe.   Another option is galvanized fence post material.... which comes in as high as 52 ksi yield strength..and as big as 2.875"  OD.  KM1H has been using the galvanized 52 ksi fence post for masts for a looong time. They are cost effective.

The issue with aluminum is.... it flexs  3  X as much as steel.  (Modulus of elasticity is triple that of steel).

Your issue will be  2 x fold.  How much will it bend above..and below the bearing ?  It's a fulcrum at that point.

James, thank you for your sage advice and great information. I used 2" schedule 40 water pipe because it is the largest that the Yaesu rotator will accept. I did not know the details of galvanized fence post and will consider it in the future. I'm looking to upgrade my 2" water pipe plus aluminum mast. The modulus of elasticity is demonstrated with my mast where the steel does not bend while the aluminum sections above does. It holds a Hexbeam 20' above the house support.

[VR2AX]

Some thoughts from actual experience...

Brian - K6BRN

Brian is correct. 40+ years ago I bought a house. Turned out my next door neighbour was a ham (trees + poor initial survey but other story). He had a 40 feet (2x20) mast (lattice) attached (bracketed) to his wind facing property elevation (bricks not wood). It's not the max winds but the constant onshore winds over time. It broke his house. Forget modelling and supposed strenghts. Just move the thing away.  And declare to insurers to the extent required wherever you are. You don't want to be asking the question 'who are good insurance coverage lawyers'. The win rate for insurance coverage claims is what makes profit for insurance companies.

[W3LFR]

Thanks all for the useful comments. My takeaway is not to use an aluminum mast, instead use thick wall water pipe and to limit the mast height to around 10 feet above the thrust bearing, and either mount the antenna very close to the rotator or mount it near the ground. with the TB attached to the house  I'll contact my contractor friend in case he has any other suggestions.

[KH6AQ]

My Hexbeam mast:

21' x 2" schedule 40 water pipe, 45 kpsi yield strength (Home Depot)
6' x 2" x 0.120" wall 6063-T832 aluminum tubing, 39 kpi (DX Engineering)
6' x 2.125" x 0.058" wall 6063-T832 aluminum tubing, 39 kpi (DX Engineering)

The water pipe is supported by the house via a nesting receptacle at 14' above GND
The 2.000" aluminum extends 1' into the water pipe and has thin aluminum shims (Home Depot)
The 2.125" aluminum telescopes over the 2.000" aluminum by 1'

Total mast length is 31'
Total antenna height is 33' because the base is mounted on a tilt-over arrangement 1' above ground plus the rotator and short mast.

In a ~55mph gust the top bends approximately 18 inches which I don't see as excessive. The mast tilts up/down using a hand winch. The mast nests in a wooden structure which is secured to one of the eves in the N-S direction. To the west it is secured by the mount. To the east it is held by the winch cable. No holes are drilled in the house; everything is secured using clamped wood.

Calculated wind survival is a 66 mph wind gust