[TowerTalk] Cushcraft 40-2CD Repair

[Leeson]

I've used both drawn 6061-T6 and 6063-T832, the yield strength and other 
parameters are essentially the same. The yield strength for both is 
around 35-40k psi. Many other tempers of 6063 are not as strong.

See Table 3-1 Yield Strength of Aluminum and Steel Alloys, pg. 3-8, 
"Physical Design of Yagi Antennas." It shows both at 35,000 psi. A 
downloadable scan of my book is at
https://www.dropbox.com/s/hmhkeofz0igrg1e/Physical%20Design%20Of%20Yagi%20Antennas%20D%20B%20Leeson%20V2.pdf?dl=0

For another picture, see 
https://www.makeitfrom.com/material-properties/6061-T6-Aluminum/ and 
https://www.makeitfrom.com/material-properties/6063-T832-Aluminum/

You can always reinforce with inner tubing, see "Strengthening the 
Cushcraft 40-2CD," QST, Nov. 1991, pp. 36-42, 
https://k7vc.com/402cd.html See also Section 11.3.1 of Physical Design.

73 de Dave, W6NL/HC8L

On 8/12/24 1:58 PM, john at kk9a.com wrote:
> I am not a mechanical engineer or a metallurgist but I believe that the
> tensile strength and yield strength for 6061-T6 and 6063-T8 are nearly
> identical.  I used to buy 6061-T6 for all of my homebrew Yagis from Shapiro
> Metal Supply and certainly did not pay $60-$80 for 72" pieces.  Lately I use
> the 6063-T832 that DX Engineering sells.  I really would be surprised if
> Cushcraft used 6061-T6, their aluminum always seemed soft to me.
> 
> John KK9A
> 
> 
> Michael W1ECT wrote:
> 
> A couple of years ago we had a big ice storm here that damaged my
> Cushcraft 40-2CD (2-el "shorty-forty") antenna.  It's been sitting
> it in the basement for quite a while and I've finally gotten around
> to refurbishing it.
> 
> The worst damage was to the innermost element sections (4) which were
> badly bent and need to be replaced. I see that DXEngineering carries
> the appropriately sized tubing: 1.250" OD, .058" wall, and 72" length.
> 
> Their price is reasonable at $21 each but the alloy is 6063-T832 and I'm
> wondering if this will do the job.  I did some searching around the web
> for 6061 tubing and found the prices to be around $60-$80 each!
> 
> Mike - W1ECT  (b1 at xmlog.com)
> 
> 
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