Fan Deck


Whatever fans you choose to use for your kiln, you will need a place to put them. The fan deck is what supports the fans and helps to separate the heated dry air heading into the lumber stack from the moist somewhat cooler air exiting the lumber stack. Fan decks are one of those areas that aren't covered in much detail in most of the plans you find, so you're left to your own imagination and design skills. The fan deck for my solar kiln started off as an overly complex, way too heavy monstrosity of boxes made of studs and plywood. After completing the first segment of the original fan deck I realized it was just too heavy for the 2x4 rafters to support well. Especially when fans still needed to be installed and the baffle would be hung from the fan deck.

Back to the drawing board where I found simple is better. Had I built the kiln floor with 3/4" plywood as I should have, I would have had the offcuts that would work perfectly for the fan decks. I didn't, so I had to go buy a full sheet of treated 3/4" plywood to use. I built the fan deck in three segments; one for each fan. A benefit of building each one separately was that it made it much easier for a single person to install. Each segment is simply a piece of the plywood with a hole cut in it for the fan. Each plywood segment is held in place by screwing it to studs hung from the rafters.

There was nothing scientific about where the fan deck was located. It is approximately where the back edge of the lumber stack will be. I have assumed a four foot wide stack with approximately equal spacing front and back. The determination of the exact fan deck location was driven by where the closest stud was in the end walls. With the end wall studs located, I nailed the outermost fan deck supports directly to the walls.

REMINDER - Don't feel compelled to size the fan deck supports so they come all the way to the bottom of the fan deck. They need to end a couple inches above the bottom of the fan deck to leave room for the attachment of the baffle.

One of the three plywood fan deck segments cut to fit my fans Intermediate supports and outer support in the distance The other intermediate supports and outer support

With the outermost supports in place, the intermediate supports were located based on the plywood being attached to the back of the outer supports and front of the inner supports and screwed in place. Why the alternating positions? I'm not sure. I thought it would cleaner from the front if the inner supports were behind the fan deck. Fewer shadows to be cast but I doubt that would make any difference at all since the supports casting the shadows would also be soaking up the sun. I like it, looks pretty, and that's good enough for me. And yes, I did chamfer the back of the intermediate supports in the hope that I wouldn't slice open my forehead while loading the kiln.

Closeup view of a couple intermediate supports One of the fan deck segments viewed from the back of the kiln Another fan deck segment viewed from the back of the kiln

Each of the three plywood segments was then screwed to all of the supports.

LESSON LEARNED - don't get too anxious to see something completed and skip over the obvious time saving steps. Painting the fan deck supports before installing them would've saved me a cramped neck from trying to make sure the very tops of the supports were completely painted so everything would look nice from the sun's point of view.

Front side view of one of the fan deck segments Middle fan deck segment viewed from the back Middle fan deck segment viewed from the front 

From the front you can clearly see a large gap between each rafter and above the fan deck. Not a lot of air flow there but it wouldn't hurt to fill that gap as much as possible. Some gap fillers were cut from some of the leftover 1/2" plywood and screwed to the fan deck. A couple vertical pieces were also installed between each of the segments to fill those small gaps and to tie the whole fan deck structure together.

Great big ol air gaps above the fan deck- pretend you don't see the fan already installed Gap fillers installed Vertical pieces cover the gaps and tie together two adjacent segments
 
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