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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