Hold my beer - I'm gonna try try something...

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On 1/9/2010 11:03 AM, FrozenNorth wrote:

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.
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Morris Dovey
DeSoto Solar
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On 1/09/10 1:55 PM, Morris Dovey wrote:

Not sure about the painting or colours available, but how about some of the flat roofing type products (most are probably black I suspect, but there may be options).
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Froz...


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The flashing that roofers use comes in colours and seems to last a long time.
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 fine. Just how important is the shipping weight? Isn't size the driver in the shipping costs more so than a couple of extra pounds?
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On 1/09/10 2:43 PM, Robatoy wrote:

Even a vinyl or aluminum siding product may be worth considering, I am just thinking of products already designed to be outside anyway.
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On 1/9/2010 1:43 PM, Robatoy wrote:

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...
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Morris Dovey wrote:

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 is iffy.
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 wood edges.
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On 1/9/2010 11:44 AM, dadiOH wrote:

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 when needed.
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Morris Dovey wrote:

May have lasted much longer, don't know, 20 years was the length of time I had the stuff before selling.
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Morris, this would seem to be a natural place to use one of the artificial lumbers - Azek, etc. Here is a list of manufacturers: http://www.deckspecialists.com/composite_deckmaterials.htm
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"Morris Dovey" wrote

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 properties.
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 tricky part.
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. :)
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On 1/9/2010 1:11 PM, Lee Michaels wrote:

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. :)
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On 1/10/2010 9:04 AM, Morris Dovey wrote:

And that's exactly what good builders look for, as you are, materials that obviate that necessity. In the case of house trim, I use Hardi type products exclusively.
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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. Lyndell
http://www.decra.com /

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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 through it.
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.
WayneJ
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wrote:

'k, I'm intruiged. Can I ask what the use of these boxes is?
-Zz
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On 1/9/2010 2:59 PM, Zz Yzx wrote:

Solar heating panels. They mount in the sunny side of a structure to keep it warm. Photos at
http://www.iedu.com/DeSoto/SC_Madison /
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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.
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On 1/9/2010 3:44 PM, whit3rd wrote:

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 a pro.

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.
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Morris Dovey wrote:

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 various alloys.
Too bad you can't hot dip galvanize your frames :)
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dadiOH
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On 1/10/2010 8:04 AM, dadiOH wrote:

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")
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