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eddiemac
eddiemac's picture

" . . . do you think it would make sense to . . ."  

Scott, that's a question above my pay grade.  You sound like a pioneer and need better advice than mine.  Check out:  www.woodweb.com/cgi-bin/forums/sawdry.pl

ScottS
ScottS's picture

 Eddimac what can you tell me about the roof sheets you chose to use?

eddiemac
eddiemac's picture

I used a brand called Tuftex and got it at Home Depot.  It is some kind of plastic (polycarbonate comes to mind), light weight and subject to cracking if you screw it down too tight or don't drill oversize holes for the screws (it expands and contracts slightly to move with changes in temp).  You can use regular roofing screws, but they sell companion screws.  I think it is UV-treated, which anything you use needs to be to stand up to the sun.  They recommend it not be applied directly to a dark surface  -   you have to use foam seals/spacers, which you need to do anyway around the edges to seal in the heat.  (It just occurred to me that the places where I have cracks were where I applied directly over black foam weatherstripping).  People with hail damage report being able to repair it by attaching small pieces of the same material over the cracks using PVC glue.

Scott, have you researched solar kilns on the Forestry Forum?  Check out Pineywood's kiln there.  He reports achieving high temps in his kiln.

www.forestryforum.com/board/index.php/board,8.0.html

Post Oakie
Post Oakie's picture

The rule of thumb is 1 sq ft of collector area per 10 bd ft of lumber capacity.  As long as you have good air circulation, you should be in good shape.  Powder post beetles is only one of the little critters you need to kill.  The Walnut Twig Beetle is another.  It has the capacity to wipe out walnut as a species.  Several states (including Pennsylvania, I believe) have a quarantine on shipping out walnut logs.  Then there are pine beetles, Emerald Ash Borer, and possibly even termites.  Point is, no matter what species of wood you are drying, you should bring the wood to at least 135 degrees and keep it there long enough to kill any bugs in the wood.  You should also keep kiln records so that you can document the process.  You should be able to show that your wood is not responsible if someone has an infestation.

eddiemac
eddiemac's picture

Thanks for setting me straight.  I get into trouble when I ad-lib; and thus the value of a forum, where second opinions can tidy things up.  But, is there actual information on temperatures at which each bug can be killed or are we playing it safe, or is one bug just like another in vulnerability to heat?

Post Oakie
Post Oakie's picture

As far as I know, heat will get rid of all the bugs.  Here is what the International Standards for Phytosanitary measures has to say for international shipping containers:

"When using conventional heat chamber technology, the fundamental requirement is to achieve a minimum temperature of 56 °C [133 °F] for a minimum duration of 30 continuous minutes throughout the entire profile of the wood (including its core)."

That's good enough for me.

Baron
Baron's picture

I believe I've read that it also gets rid of all disease pathogens at that temp. I read somewhere that 160 is necessary for some varieties to set resin. Is there anything to support this as far as anyone knows?

Baron
Baron's picture

I believe I've read that it also gets rid of all disease pathogens at that temp. I read somewhere that 160 is necessary for some varieties to set resin. Is there anything to support this as far as anyone knows?

Post Oakie
Post Oakie's picture

Here's what Nyle (manufacturer of dehumidification kilns) has to say:

 

"When softwoods are dried, pitch sets at the final temperature of the drying cycle. For

example, if the last step of drying is 120F (approx. 50C), then the lumber has to be get above

that temperature again before the pitch starts to run. Some high-speed sanding equipment

used by major furniture manufacturers heats the wood to 160°F, so these manufacturers

require pitch set to that temperature to avoid wasting sanding belts. If the pitch must be set, it

can be done by heating the lumber at the end of the drying cycle to the necessary

temperature. This can be done even if the dehumidifier is not rated to operate at that

temperature, because during pitch setting you are not removing water with the dehumidifier,

you’re just applying heat."

 

That was from their web site  http://www.nyle.com/downloads/KilnDrying.pdf . Very good source of info.

 

Baron
Baron's picture

Yes. That is probly where I read it. On another site guys with home built kilns reported their fan blades breaking and diodes burning at 160. 

Post Oakie
Post Oakie's picture

You could always remove the fans.  That temp is only required at the end of the cycle when the wood is dry, and you don't need the fans at that point.  In any case, they don't need to be running.

ScottS
ScottS's picture

What a wealth of information. I'm gonna have to rethink this one.

Baron
Baron's picture

It would scare me to leave the fans off. 

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