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Posted by schooner on September 28, 2006, 1:05 pm
 
I think the best you could do is overlap it and caulk/silicon/poprivet the
two sheets together.



Posted by Jeff on September 28, 2006, 1:58 pm
 
Darrylv wrote:

   Mike in NZ's idea to use 2' wide. He has extensive experience
building collectors and you can search archives for design
recommendations from him.

   Reasons he gives:

1) Easier to manhandle 2' panels.

2) 2' wide has less thermal expansion contraction, you will need to
allow expansion along the length but not worry so much about the width.
Remember these things undergo tremendous temperature variations.

3) You wont have to brace either the cover or the back if you are only
going 2'. (Also less warping problem) That is a big point!

You build as may panels as you want and simply connect them side by side
by connecting the manifolds.

   Your call, but I'm sold on the 2' idea. Any time you can alleviate
three problems, I'm on it. It makes for a lighter, cheaper yet more
robust package.

   Jeff


Posted by Gary on September 28, 2006, 2:50 pm
 Darrylv wrote:

SunTuf is made in 4 ft wide, but I've not seen it my area.

I made 4 ft panels by overlapping one corrugation, sealing with a small bead of
silicone, and backing it up with a 3/4 by 3/4 wood strip which and a few screws
(with the EPDM washers).
I found that the panels also need support in the horizontal direction to prevent
warping as they heat up.  As long as the panels are steeply tilted, the supports
don't have to be very big -- I used more 3/4 by 3/4 wood.  I spaced the
horizontal supports at 3 ft intervals. This keeps the panels dead flat, and is
working fine.  This sounds like a lot of work when you write it down, but in
practice it takes very little time.  Just be sure to gang cut all the slots for
the intermediate supports in the verticals before you put them up.

I guess I am doubtful on whether using 2 ft panels would eliminate the need for
light horizontal support strips to control thermal buckling -- everything I've
built with the SunTuf makes me think you would still need some horizontal
(light) supports to control the bucking.  Jeff -- have you actually seen the 2
ft wide panels without support work and stay flat?

This may be one advantage of the multiwall polycarbonate -- less intermediate
support.  On my new collector, I am using 4X12 sheets of 8mm twinwall.  I'm
supporting it on all edges, and then including horizontal supports at the 1/3
points.  I am using half inch EMT conduit with a bead of silicone on the top for
the intermediate supports -- this appears to be straighter and cheaper than wood
supports.  But, it will have to go through a winter before I know how well this
actually works out.




--


Gary

www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects









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Posted by Darrylv on September 28, 2006, 8:14 pm
 

2x8 sheets are $5 CAN (approx $0 USD) at home depot. I tried locating
urethane foil backed insulation. No one seems to stock it around here.
I can special order a 4x8 sheet for $5 or so CAN.

Is is resonable to use 2 layers of the suntuf for a very cold climate?
Perhaps a design where the second glazing could be removed for warmer
months?

-darryl


Posted by Solar Flare on September 28, 2006, 11:28 pm
 I thnk you are confusing the Home Depot stuff with SunTuf
polycarbonate. They sell cheaper compounds with flyers beside them
bragging about the better stuff. Careful.



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