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Posted by Solar Flare on October 5, 2006, 12:31 am
 
Use exterior grade sheeting. It contains waterproofing agents in the
glue and is much stronger against flexing and lighter in weight.
Oriented strand board.




Posted by Bob the Tomato on October 5, 2006, 3:31 am
 
I think that somewhere we lost something in translation.  :-)  MDF
stands for Medium Density Fiberboard.  It's used in cabinets and in
furniture.  It's basically very finely ground wood dust held together
with some kind of glue.  It's NOT an exterior grade product at all -
it will fall apart and return to its sawdust form if it stays wet.  If
it gets damp it will swell up and lose strength.

I think the material you are looking for - highway sign / billboard
material - is called MDO, Medium Density Overlay.  It's expensive.
It's a sandwich.  The meat of the sandwich is exterior or marine grade
plywood.  The bread (available in 1-side or 2-side) is a paperboard
impregnated with something to make it totally waterproof (phenolic?
resin?).  Anyhow it looks like a flat piece of brown kraft paper bag,
glued to an absolutely flat surface like tempered Masonite.

Hope this helps.
Bob the Tomato



wrote:



Posted by Jeff on October 5, 2006, 3:00 pm
 Bob the Tomato wrote:


Well, it's all a bit late now. I switched off plywood just before I
bought the materials, so 6 boxes wil be made of this. It's really the
copper and the glazing that cost money and they can be reused.

   Current plan is to buld the boxes with MDF, prime them with Zinsser
BIN and then Sherwin Williams house paint.

   The boxes will be off the roof an inch and the Suntuf will lap over
each side and the bottom so drips won't run into the seams. The top edge
will have a bit of plastic bent over the width of the box and attached
to the SunTuf. That leaves the holes/ slots in the box side where the
header pipes go through. Perhaps a slit funnel... and some silicone...

   It's used in cabinets and in


Posted by Jeff on October 6, 2006, 6:34 pm
 Mike wrote:

   Hi Mike,

   Question about brazing the headers to the risers.

   Can I just feed the riser into the header, or do I need to trim the
header so it matches the curve of the header? Eventually I'll have 18
boxes on the roof, so I'm thinking the 1" header is the way to go. I
really prefer the 3/4" price!

   Went out yesterday and bought Stay Brite #8 silver solder at the
recommendation of the Plumbing house. 15,000 psi vibration proof joints
is claimed. At least I'll be to use my MAPP torch...  Man, this stuff is
expensive!

   Glueing up the boxes today...

   Cheers,
JEff



Posted by Mike on October 6, 2006, 8:23 pm
 Glad you've finally started your project Jeff.

There is no need to trim the end of your risers to match the headers, its
just too much work. Make the hole in the headers so the tube pushes in with
a good fit, push them in about 3mm so when you apply the solder it will flow
into the joint and key on both sides, if they are in too far the water flow
will be restricted, not so much of a problem on a pumped system.

The hardest thing is aligning the grid of tubes evenly. I made a simple jig
from some wood that clamped the headers and risers before brazing. I use a
hard silver phosphor brazing rod 15% silver, but needs a hotter flame than a
mapp torch, requires an oxy-acetylene set. Your Stay Brite will be ok
though.

If you're eventually going to 18 boxes then probably 1'' headers would be
required.

Do make sure you pressure test them with compressed air and soapy water on
all the joints before mounting the absorber plates, damm difficult to fix
once everything is assembled then you find a leak. I have only done that
once....

Yes the copper tube is getting very expensive, but it will last a lifetime.
Its still cheaper to make your own than purchase commercial units which
would also have risen in price.

Cheers
Mike




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