[TowerTalk] Stub mast strengthening

[K8RI]

On 4/16/2013 9:04 AM, Bob K6UJ wrote:
> Steve,
>
> The sleeve would definitely add strength.  The lateral force from the wind load on an antenna mounted on the mast puts the most stress
> at the bottom of the mast, think of a 16 foot lever arm.   I would find out the yield strength of your aluminum mast and do a
> check of the maximum antenna load you should use.  Aluminum has a much lower yield strength than a steel mast so you need to be careful.
> There are calculator programs available to help you figure out the load rating of various mast materials.

There are many alloys of widely varying strength from both a flexibility 
ans yield strength.  The most common, 6061T6 is neither the strongest, 
nor cheapest.

I use a lot of the 6061T6, but not in antennas. A 2" diameter piece with 
0.25" wall, 24' long is heavy and when used as a gin pole displays a 
surprising amount of flexibility.

73

Roger
>
>
> Bob
> K6UJ
>
> On Apr 16, 2013, at 8:31 AM, GW4BLE wrote:
>
>> I have a question concerning 'sleeving' (can't think of a better way to describe it) -  I have a 16' x 2.5" OD thick-wall aluminium tube that will be used as a stub mast, would inserting 6' x 2" OD thick-wall aluminium  tube into the bottom of the tube add to its' 'strength' in any way or would it just add unnecessary weight?
>> Sliding it in makes quite a snug fit, but not exactly 'tight'
>>
>> Steve
>> GW4BLE
>>
>> Sent from my iPhone 4S
>>
>>
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