I'd like smooth paintable surface (to at least not clash with house
siding) without penetrating fasteners. The wood, if kept painted, should
last more than 20 years; and I'd like for these things to last for at
least 50 years even if not maintained at all. I'd also like to keep
weight down to control shipping costs.
The flashing that roofers use comes in colours and seems to last a
That .002 SS foil would stick to wood with Wilsonart 3000. That type
of adhesive is just amazing. Weldbond is similar. Water based
technology has come a long way.
And as long as one side of the joint is porous, it will work just
Just how important is the shipping weight? Isn't size the driver in
the shipping costs more so than a couple of extra pounds?
The metal doesn't appear to be a large cost factor. I thought about
flashing, but my flashing choices here appear to be aluminum and copper.
Copper is expensive and changes appearance (which might be ok with some
customers, but not with others). Aluminum is a little better with
respect to appearance, but would perform poorly on a saltwater coast. I
chose stainless primarily because I want it to hold up well not only in
Des Moines and Sarnia, but also Edinburgh and Oslo...
...for a very long time.
*This* is a big part of what I was after. Thank you! I'll investigate.
It's probably not a major factor, but I still don't want to add any more
mass than necessary. Already I'm discovering that these things are
getting heavier every year...
You didn't say what kind of wood, what the boxes are for or how important
appearance is. I'm assuming plywood since laminating anything to solid wood
If appearance isn't terribly important - and if it were me - I'd laminate
the ply with fiberglass and polyester (not epoxy) resin, then paint it.
I've never done that where it snows but have many times in the
tropics...lots of sun, heat, salt from the ocean. It works well, had stuff
like that for 20+ years.
The potential problem with *any* lamination is DElamination...once water
gets between the two surfaces rot starts quickly. And how about the inside
of the boxes? At the very least, any laminate should be continuous over the
Plywood and manufactured sheet goods are a possibility - but right now
I'm working with SYP and poplar. If I can completely prevent moisture
from getting at the wood, then my materials choices widen substantially.
The boxes, of course, are solar heating panels. The front is glazed and
the back will be out of view (inside a south wall). The interior of the
box will be exposed to warm air at the same moisture level as the inside
of the structure - which isn't much of a concern. What I want to do is
protect that portion of the box edges that are exposed to the outdoors.
Appearance is important. I'd like 'em to look smooth, clean, and simple.
Paintable would be very nice, but probably isn't an absolute requirement.
Currently I apply a wipe-on coat of poly, sand lightly with #400, and
brush on a coat of white primer. The customer then applies a color coat
of their choosing - but beyond that point longevity depends entirely on
the customer keeping the exposed portion of the box painted, and I want
to remove that dependency.
Twenty years isn't long enough. I'd settle for 50 years, but a century
would be way more than twice as good. I'm determined to make these
things to outlast the customer's grandchildren if I can. :)
I'm not worried about the inside of the boxes at all - they tend to be
self-regulating and have good airflow.
I am concerned about the adhesive deteriorating over time (that's one of
the reasons I'm looking for advice here). One of the box's design points
is that all glue and sealant areas are already shielded from UV, and now
I'm wanting to provide 100% protection for the exposed (exterior) wood.
One of the things I like about the foil approach is that I can fold it
over the front edge of the box side so that the front edge of the box is
covered. I'm planning to use a closed-cell foam weather stripping
between that edge and the glazing, and a 1/8" aluminum trim angle over
the edge of the glazing to protect the weather stripping from UV and to
dress up the edge. By doing that, I should be able to prevent moisture
entry and make the glazing removable (it's not now) to allow cleaning
I can't imagine the adhesive holding up that well in these circumstances.
Particularly if it gets hot inside of that box. If you tired this, I would
have to get some kind of assurances from the manufacturer that it would be
suitable for this application.
What you need is some kind of coating over the outside.
Fiberglass comes to mind. I have seen fiberglass work well, but it
deteriorates over time. It would need to be refreshed from time to time.
I used to work for a solar heating company that made the parabolic heaters
for pools. We thermoformed everything. We got the metal coated mylar in
sheets from the plastic company. We then just heated up the thermoforming
machine and made up the parts. We were interested in its reflective
Since you need a protective covering, you wouldn't need the reflective
coating. Would something like this work? You could talk to the plastics
company guys. They are very knowledgable. It is easy to make a
thermoforming machine. You like to make things low cost knockoffs of
industrial machines anyway. <G> You can get plastics that last a million
years. Attaching the protective plastic cover to the wood would be the
And also, a spray on material could work as well. I know nothing about this.
I know that somebody suggested the truckliner stuff. Could you go to a
truckliner guy and have him spray the unit?
Is there some other kind of material/process that is sprayable? You might
look at heavy duty spraying eqipment and talk to those guys. They may be
able to give you some suggestions as to who talk to.
And you can always ask Lew for his epoxy suggestions. :)
Yup. The problem isn't really much different than house trim. If people
would keep it painted, it'd last for a really long time - the problem is
that they don't. That leaves me with the option of either blaming them
for failures or doing what I can to eliminate the possibility.
Metalized mylar works pretty well when new. The guys I've talked to
about using it in parabolic troughs have been unanimous about not
expecting it to last longer than two or three years. The polycarbonate
mirror I used looks lite it'll do better than that - but since I started
on this effort, I've been looking at mirror-polished s/s foil on a
plywood or Delrin substrate.
I've talked to local plastics distributors and haven't yet received any
encouraging news - and if I can arrive at a good bonding method, I think
a non-corroding meal surface would really be more sellable.
I've given some thought to thermoforming the panels and foam filling the
result, but I'm not very confident that they'd last much longer than
painted wood. Given that, I think I'd prefer to stick with wood.
There's a nearby outfit that manufactures a sprayable roof coating that
they claim is even better - but they didn't think it would last
appreciably longer than primer+housepaint on the panels.
I probably haven't done enough of this. So far I haven't heard of
anything that seemed worth the cost.
Already done - and I'd guess that if anyone could coax epoxy into doing
the job, it'd be Lew. :)
Morris have a look at this page. Definitely not smooth or paintable but
lasting .......... yes. 50 year warranty......life expected to last 100
years. Gottem on my house! They make flat sheets for for trimming aroung
chimney's and the like. Lots of color and pattern options. May not be what
you want but the longevity is in the range you require. Decra is not
cheap......you didn't mention price range.
Besides being expensive, 0.002 stainless foil is THIN. If the completed
box gets any significant rough handling you should expect one or more cuts
You mention exposure to salt, if the stainless foil is in contact with
salt water (or other source of chlorine ions) in the absence of oxygen it
will corrode fairly quickly. Foil 0.002" thick doesn't allow for much
corrosion. Salt water trapped between your box and another surface or even
a layer of saltwater mud can exclude oxygen to the degree required.
In terms of moisture and fungus attacking the wood, your structure
will need roof-like coverage; that means flashing in addition to
the foil/cement that protects the large flat surface. Stainless
steel will just be a kind of paint, with all the problems of paint
(nicks or cracks will grow into major flaws). Some ventilation
will be required, too, or the protected wood will never have
a chance to air-dry in case of accidental moisture.
Instead of looking at just the protect-flat-surface part of the
problem, you need to examine edge and corner and
overlap areas, and apply appropriate flashing there. It doesn't
seem to me this will be easy.
If dissimilar metals are nearby, and if they touch the stainless,
you can expect accelerated corrosion of the metal. Copper
and lead roof structures have lasted centuries, so
there's certainly hope for success.
Exactly so - during daylight hours there will be some continuous dry
airflow, becoming "huge" airflow during winter months. Over the past 7+
years I haven't seen any problems with painted panels, and expect that
behavior won't worsen with stainless steel "paint".
To the extent possible, this is already being done in the panel itself -
and I've made a point of making clear to customers that attention to
structure detail is one of the reasons to have installation performed by
Galvanic action is a concern, and I'm expecting s/s to behave reasonably
well in this regard. Lew has suggested silicon bronze instead of s/s,
and this will be one of the aspects I'll need to investigate further.
Note that there are numerous bronzes in addition to silicon...manganese,
aluminum, phosphorous, lead etc. I'm not suggesting silicon is not good,
merely advising and suggesting research into the characteristics of the
Too bad you can't hot dip galvanize your frames :)
Good suggestion, and that research is already underway...
Hmm. Lemme see - first dip in a concentrated copper sulphate solution,
then do a light copper plating (think baby shoes or tree leaves), then
plate gold over the copper - how's that?
(still a bit spendy for a "firnace")
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.