: If you invert the 40-2CD support brace, it MAY not provide adequate
: support. When on top, all you deal with is tension. When on bottom, you
: have to consider buckling. Does anyone know if it will work that way as
: supplied by cushcraft? I'd be interested in a true engineering-type
: analysis, not just some anecdotal stories of how well it works.
after i had reenforced the boom on one of W5KFT's 40-2cds
i have to say that i agree with the following.
----------------------------
Dave Leeson - writes:
Pull-apart of Struts
The struts don't add any wind survival to the boom, but they make it
look better by removing droop. The struts are held together by hose clamps,
and the joints can be made stronger by pop-riveting. Because I had greatly
strengthened the boom and I used a short mast, I put the struts under
rather than over the boom. This turned out to be a lesson in strength of
columns under compression, which is different from the same piece under
tension; one has popped out and disappeared forever into the chapparal.
Dave Leeson, W6QHS
--
George Fremin III
Austin, Texas C.K.U.
WB5VZL
512/416-0140
geoiii@bga.com
>From k2mm@MasPar.COM (John Zapisek) Sun May 8 07:04:21 1994
From: k2mm@MasPar.COM (John Zapisek) (John Zapisek)
Subject: 40m Buckling Brace
Message-ID: <9405080604.AA26604@greylock.local>
Barry:
> If you invert the 40-2CD support brace, it MAY not provide adequate
> support. When on top, all you deal with is tension. When on bottom, you
> have to consider buckling. Does anyone know if it will work that way as
> supplied by cushcraft?
Steve/N4TQO and I tried it at Al/AG6D's. The supports did indeed buckle.
It happened at the ends of the support tubes which are flattened to make
the screw holes. We ended up putting it up the way it was designed.
> I'd be interested in a true engineering-type analysis, not just some
> anecdotal stories of how well it works.
Too bad. This anecdote is all you get. --John/K2MM
>From barry@w2up.wells.com (Barry Kutner) Sun May 8 13:09:38 1994
From: barry@w2up.wells.com (Barry Kutner) (Barry Kutner)
Subject: 40m Buckling Brace
Message-ID: <Ri8ZLc1w165w@w2up.wells.com>
k2mm@MasPar.COM (John Zapisek) writes:
> Barry:
>
> > If you invert the 40-2CD support brace, it MAY not provide adequate
> > support. When on top, all you deal with is tension. When on bottom, you
> > have to consider buckling. Does anyone know if it will work that way as
> > supplied by cushcraft?
>
> Steve/N4TQO and I tried it at Al/AG6D's. The supports did indeed buckle.
> It happened at the ends of the support tubes which are flattened to make
> the screw holes. We ended up putting it up the way it was designed.
>
> > I'd be interested in a true engineering-type analysis, not just some
> > anecdotal stories of how well it works.
>
> Too bad. This anecdote is all you get. --John/K2MM
Your anecdote is all that is necessary. What I meant is I didn't want to
hear "I/ve had it up 20 years and it's been fine."
Barry
Barry N. Kutner, W2UP Usenet/Internet: barry@w2up.wells.com
Newtown, PA Packet Radio: W2UP @ WB3JOE.#EPA.PA.USA.NA
Packet Cluster: W2UP >K2TW (FRC)
.......................................................................
|