 | How high should I make my curtain on a hoop house structure? |
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We normally recommend 6’ high, unless the Top Clasp would be
so far up the slope of the roof that it would hinder snow sliding off in
winter. You are paying by the Lineal Foot, not the height, except for the length of
the guidepipe. You do not have to open the curtain to the max, but
it is useful to have the ability to open 6’ high in the summer, and clean
the house out thru the sidewalls. With 6’ high openings your inside
temperature can usually be within 1 degree of the outside temperature on a
17’ wide house; within 2 degrees on a 24’ wide house; and within 3 degrees
on a 30’ wide house. (Temperatures in the peak will be higher, but the air
will mix a bit for another couple feet of height.) |
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| How high CAN I make my curtains? |
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We recommend up to 8’ high. We have had customers go 9’
and 10’ and even had a customer go 12’ high, BUT WE DO NOT RECOMMEND those
heights. Do so only at your own risk, and always use proper wind control
methods. As curtains roll higher, the potential for wrinkles increases.
Wrinkles cause uneven rolling action. When a wrinkle does occur, it triples
the thickness of the material at that location, so 12 mils of poly becomes
36 mils. If wrinkles occur evenly throughout the length, it often
works out, but if they only occur at 1 or 2 spots, the curtain will roll
much faster there. On very tall gutter connect
type structures with 12’ or higher sidewalls, consider 1 upper curtain
over a lower curtain. |
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| Why does natural ventilation cool a structure
better than fans and intake shutters? |
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Research has shown that there is ALMOST NO TIME at which a
minimum 1 MPH breeze is not blowing. Usually a 2 MPH to 3 MPH breeze is
occurring. If the entire side of your greenhouse is open, in 17 seconds the
air will breeze across a 24’ wide house; or 21 seconds for 30’ wide. At 3
MPH, the air will go across that same 24’ house in less than 6 seconds. It
takes a lot of shutters and fans to pull air 96’ down the length of the
structure to achieve the same result. And, by the time the air gets to the
far end, it will have considerably warmed. On many summer days, shutters and
fans will run 12 hours (sometimes 24 hours) a day to TRY to continue cooling. A normal hoophouse
might run 2 fans using 16 to 18 amps of power running continuously. In contrast,
Roll-Up sides, 6’ high, will require running 2 small motors, about 3
amps each, for only about 10 minutes throughout the entire day.
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| Will
natural ventilation result in higher insect and disease problems inside
the greenhouse? |
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A few years ago, Oregon University conducted extensive tests
thinking they would find this to be true. In fact, the reverse results were
obtained. Leaf & stem movement does more to control plant insects than all
of the sprays we use. Every opening in a greenhouse lets the first insects
in, as well as them coming in with
greenhouse personnel. But when the leaves and stems do not move much on
the plants, the insects multiply RAPIDLY, undeterred. Shutters & fans
generate leaf movement at the intake end and near the fan end, but not
in the rest of the house. Adding HAF assists in leaf movement. But
natural ventilation provides much more extensive air flow and leave &
stem movement than fans. You get less insect build-up, less disease,
shorter internode spacing, and tougher plants. You will use less
insecticides, less disease controls and less growth retardants. |
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| What motor should I use to
open my curtain(s)? |
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See the motor chart below for general rules. We created a spread sheet
chart that determines what sized motor will fulfill your needs. If you are
unsure of which motor to use, call us with the necessary info below and we
can determine what motor is best by: weight of roll-bar(s) ______,
roll-bar diameter ______, weight of covering ______, length ______, height
______, fabric thickness ______, threshold weight (on Curtain Wall
Systems)______. |
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NOTE: Tube motors have a long and narrow profile for curtains that must
get close to the ground, but are only single direction output. Gear box
motors can be 2 directional output, allowing 220’ runs in each direction for
440’ total. |
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Motor Capacity Chart |
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Natural Ventilation System Motor
Capacity Chart assumes: |
Standard style
ROLL-UP SYSTEMS Ht of curtain in feet |
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Motor |
Torque |
4' |
5' |
6' |
7' |
8' |
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A single bar roll-up system
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2"
Side-Clasp
Roll-Bar or 1.315" swaged pipe with Roll-Bar Cap.
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Curtain
material of 2 layers of poly or 9.5 oz per sq. yd.
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*** indicates length of roll-bar
lag to be considered
***you might have to increase
Roll-Pipe size for such lengths. |
TM2/33
TM2/40
TM3/60
TM3/80
TM3/100 |
33NM
40NM
60NM
80NM
100NM |
152
172
***300
***400
***440 |
124
160
252
***340
***420 |
112
144
232
***312
***392 |
104
136
196
***260
***328 |
96
120
180
240
***300 |
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To figure what motor will best work for your system,
follow these simple steps by first choosing what type of curtain system you
have Top Chart: Regular Roll-up
Bottom Chart: Curtain Wall Systems
THEN...
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1. In the
brown shading, find the height of the curtain opening
2. Drop down
that column until you reach a number that meets or exceeds the linear length
of your curtain |
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Curtain Wall Motor Capacity Chart assumes: |
CURTAIN WALL
Double Bar SYSTEM Ht of curtain in feet |
|
Motor |
Torque |
8' |
9' |
10' |
11' |
12' |
| A double bar (Mid Height Drive Bar) roll-up system. |
| Our Side-Clasp Roll-Bar or 1.315" swaged pipe w/our
Roll-Bar Cap. |
| Curtain material of 2 layers of poly or 9.5 oz per sq.
yd. |
| Chain threshold in bottom (adds .5# per LF) |
|
GBM40 GBM50 TM3/60 TM3/80
TM3/100 |
40NM 50NM 60NM 80NM 100NM |
76
100
120
164
208 |
72
92
112
152
192 |
68
88
108
144
184 |
64
80
100
136
168 |
60
76
92
128
164 |
