[TowerTalk] Tower Leg Maintenance

[K8RI]

On 12/6/2011 11:54 PM, Mickey Baker wrote:
> You're right, Roger, even today, steel tubular engine mounts on 
> airplanes are typically treated with linseed oil on the inside after 
> welding and a nice epoxy or powder coat is applied to the outside.
And when restored they still use it in the rag and tube fuselages.
>
> ALUMINUM airplanes are treated with great, modern chemicals such as 
> Corrosion-X or BoeShield, ACF-50 and the like.
>
They used plain old LPS-2 on my Bo.  Never do it in cold weather because 
when it warms up the thing will drip for weeks.
They did mine in the middle of summer and let it set out in the hot sun 
for a few days.  You could see the plane's outline on the ramp.

> I'm not so sure that coating galvanized steel with anything but more 
> zinc is a good idea.
>
Agreed.

> If you've had a tower up for a while, odds are that there are critters 
> living in the open tubes, at least on an itinerant basis. When they 
> move on or expire, they leave behind nests, prey, poop, and their own 
> carcasses.
A while back I picked up a couple of 38' *cheap* aluminum towers that 
definitely needed some TLC and a bit of welding.
When I started the leg cleaning I noticed a couple kernels of corn. I 
managed to get over a quart of corn kernels out of that one tower.
It also had a split in one leg just a few feet down from the top.  Thy 
had the "pointy tops" and the legs were just squashed flat and welded to 
the top braces and guide.
Spider webs had prevented water from draining so it froze and split the 
one leg.  I might have a photo of that around here some where. Those 
towers used the backwards joints where the smaller diameter leg fit down 
into the larger at each junction.

> Then, along comes the tower owner and pours a concoction in the tower 
> leg, forever bonding this detritus in close contact with the inside of 
> the tower leg, making (you'll have to admit) some sort of anomaly on 
> the inside galvanized area of this leg, sealing and perhaps putting 
> some sort of corrosive substance (lizard urine, bird droppings?) in 
> close contact with structural steel with no hope of ever being ablated 
> away by the natural and intended oxidation of zinc.

Remember many of these towers like the old American Steel had no 
galvanizing.

>
> Maybe it is just my imagination, but I've never seen a service 
> bulletin advising that this is a recommended procedure for towers.
>
Properly done it shouldn't hurt and would probably extend the life of 
the tower, but it's not something to do to a tower that been up a few 
years and is still standings.
Look at what they have to go through to redo that "Rag and Tube" 
aircraft fuselage before they put and rust preventive in those tubes.
> I have, however seen advisories for corrosion treatment and even x-ray 
> examination of steel in aircraft!
>
There's also that little gadget I mentioned for measuring metal 
thickness and it works for metal that's even under several layers of paint.
These look like, or similar too what we used 
http://www.olympus-ims.com/en/applications/measuring-metal-thickness-paint/  
I don't know what they cost.
But they look pretty handy for checking tower legs for corrosion.

73

Roger (K8RI)
> Is anyone x-ray'ing tower legs yet?
>
> 73,