30-12-2003, 03:05 PM
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Advice sought on large hoophouse
(Frank Miles) wrote in message ...
PVC works well for smaller units, but I think (guess) that this is too big for
snow. Even wind can be tough, though IMHE putting guy lines between the hoops
can make a world of difference -- there's just too much tension in the
plastic to depend on attaching to the perimeter of the material, even if the
tension is distributed by tape over a relatively broad periferal area.
In my present tunnels (each over a 4 ft bed) I have hoops, and I have
a central beam.
You didn't say anything about where you live (e.g. frequency/magnitude
of snowfalls) nor how much spacing you might have between hoops. My guess
is -- if there's a chance of having 6" or more of wet snow, it will probably
be more stress than any reasonable PVC system could withstand.
I live in Michigan. My experience is that snow will happily slide down
a hoophouse unless there is a sag. But I concur, it is probably too
much.
I know that the poly, properly clamped, will not get loose no matter
the wind (poly clamps bought at Territorial Seeds).
Might you get a warm sunny day? It's incredible how much heat you can
build up in one of these. Doors might be enough if you could supplement
with a fan. How big might these trap doors be?
Maybe 4.5 ft by 7 ft, if I have to go in with the cart full of manure.
I have already calculated that there is not enough heat storage in a
wall of water drums. The heat input is probably 50-100 W/m2 in the
winter, and the heat sink is the soil. Not clear how fast it can
absorb heat and probably depends on it being moist.I know from
experience that mulch and hoophouse is a deadly combo (plants fry, or
freeze, or both), which is a problem because all mulch must completely
decompose within the growing season (that means only leaves or
cardboard).
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What about cutting the 40x40 into two 40x20's, and make 2 hoop-houses?
(Long, not wide). If the snow isn't too heavy, there might be a chance...
That is probably what I will do. The hoophouses will still be 6ft
high. By placing them side-to-side I can take care of half the
watering, since the water will pool in the middle, evaporate, condense
on the poly, and drip all over. It certainly works for my current
tunnels. One can even consider a sunken hoophouse (I have sandy soil,
and sunken will help with the wind), with a sloping floor so as to
redistribute the water.
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