That happened here as well with our shelters, during our recent round of
snowstorms. Most of our shelters were OK but one with multiple purlins
collapsed for that very reason. Anything that can reduce proper
runoff and allow a pool to form, whether it's purlins or support struts or
whatever, will dramatically increase the amount of weight on the roof at any
given time. One way to avoid that is to have the plastic film stretched
really tight over the frame. But if the film stretches and pockets form,
such that water keeps pooling there, that's the kiss of death. We may
have been able to avoid our collapse by replacing the film earlier, but alas
we didn't. Ahh, the benefits of 20/20 hindsight.
Kathryn Kerby
frogchorusfarm.com
Snohomish, WA
Ruminations - essays on the farming life at
frogchorusfarm.com/weblog.html
In a message dated 2/18/2012 1:40:25 P.M. Pacific Standard Time,
lists AT rhomestead.com writes:
Etienne, check with Johnnys about your multiple purlins. I was at
a
presentation by them and they had tunnel failure with multiple purlins,
not
with one center purlin. The rain/snow sagged the plastic enough
that it
collected above the side purlins, causing collapse.
Beth
Spaugh
Rehoboth Homestead, Peru NY
http://rhomestead.com
http://www.facebook.com/rhomestead
"How we eat determines,
to a considerable extent, how the world is used." -
Wendell
Berry
"Without power over our food, any notion of democracy is
empty." - Frances
Moore Lappe
-----Original
Message-----
From:
market-farming-bounces AT lists.ibiblio.org
[mailto:market-farming-bounces AT lists.ibiblio.org]
On Behalf Of Etienne Goyer
Sent: Saturday, February 18, 2012 12:38
PM
To: market Farming
Subject: [Market-farming] For those who have
built tunnels using
Johnny'shoops bender
Hello everyone,
I
bought Johnny's "Quick Hoops" high tunnel bender. Their instruction
manual is really good, and I like their design. I am planning on
building two 100' tunnels this spring. I have two questions for
those
who have built similar tunnels.
First, Johnny's tunnel are
7' high in the middle, which I find is a
little low for trellised
crop. I would prefer something closer to 10'
high. I am
thinking that, instead of cutting the 6' post in half, I
would use the
full 6' length of the post, leaving 4' sticking out of the
ground
(instead of 1'). I This would make a kind of straight "side
wall"
4' high, on which the bows would rest. This would obviously cost
twice as much in post, but I think it is a fair trade off. Have
someone
done something similar, and if yes, is the structure
sound?
Secondly, how wide have you set the bows? The example in
the manual as
a bow every 4'. I am planning on using three purlins
(one in the
center, and two to attach the trellises to), so I am
thinking the
structure will be quite solid indeed. I am thinking
of having one every
6' instead. Would that be enough? My
only worry is water accumulating
on the plastic above the
purlins.
Beside, what was your experience? Any tips to
share?
Thanks!
--
Etienne Goyer - Le Jardin du
Village
http://lejardinduvillage.wordpress.com
"Changer le monde,
une betterave à la
fois"
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