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Author Topic: cheap gothic arch solar kiln  (Read 2358 times)

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Offline grouch

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cheap gothic arch solar kiln
« on: April 30, 2017, 01:07:10 pm »
The title is more flowery than the contraption. I'm hoping this thing will reach that magic 133F/30 minutes mark that WDH and others on here have mentioned, but if it fails, it will at least be temporary shelter for my growing lumber stack.

I was so tickled to be able to saw lumber for myself that I've neglected what it takes to dry and process it. Time to try to pay that piper, now. This time I'm going to be a little smarter about a project and post it while it's unfinished in order to hopefully reap the benefits of some of the experience, knowledge and creativity amongst folks on here.

First here's a link somebody posted on here somewhere and it bears repeating:
Forest Products Laboratory Wood Handbook (509 page PDF) Chapter 20, I think, is the one about the 133F for 30 minutes standard.

Ok here's the proof of concept (hey, it's still standing), a boat "house" I built to keep the snow and leaves out of my son's bass boat:


If I put something like that up with black plastic as a sort of inner wall and clear plastic on the outside, it should heat up in the sun. A gap in the black plastic at the ridge and one at the floor should turn that into a plenum and convection should provide circulation. Win, lose or draw, I'm trying it.

Here are my highly technical blueprints:


Ok, so maybe not so highly technical but at least no engineers were harmed in their making.

Here's the progress so far:
1-1/4 (nominal trade size) EMT arches:


1-1/4 EMT is close enough to actual 1-1/2 inch O.D. to fit nicely in one set of dies that come with the harbor freight tubing roller. I just drew 9ft-6in radius arcs on the garage floor and rolled the EMT until it matched.

Spent yesterday welding connectors I had previously cut and fishmouthed, in spite of wire feed issues, wind issues, operator wardrobe issues, heat and humidity issues, and carpenter bee issues.

Using a magnet and a little c-clamp for a jig:



Some T's tacked:


A pile of T's tacked:


Using a complex alignment device to start tacking the crosses:


Bunch of crosses tacked:


Before going any further, I should point out that me and MIG (MIG and I?) are barely on speaking terms. Toss in pipe-like and thin and it's a downright adversarial relationship.

Oh, and the wardrobe issue. Ever been welding and suddenly get reminded that *you're wearing sneakers not workboots, dummy!* Globules of molten steel are hot stuff. This is why you don't throw away the old welding gloves, so you don't have to take time out for a change:


All connectors (over-) welded up:


I am not suffering from an infestation of mutant mud daubers; this is just my artistic impression of MIG welding:


(And that's probably the best bead in the bunch).

That's how it stands so far.

Offline Gearbox

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Re: cheap gothic arch solar kiln
« Reply #1 on: April 30, 2017, 01:43:43 pm »
For covering you can get used billboard tarps . The ones I get are 14 X 48   $ 50.00 . I get 3 or 4 years covering wood piles . Google used billboard tarps . They have a envelope to slip in a 1x2 and then  strap it down . They come with a white or black back .
A bunch of chainsaws a BT6870 processer and not near enough time

Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #2 on: April 30, 2017, 02:05:00 pm »
Thanks Gearbox! I'd never heard of those before.

Offline Gtodoug

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Re: cheap gothic arch solar kiln
« Reply #3 on: April 30, 2017, 02:46:01 pm »
If you have a local billboard company just ask them if you can have few for free, especially if you tell them what you are doing.  We have gotten four or five for free that way.  They are usually just concerned that you don't tarnish the image of the company who's advertisement you might get.
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Offline Darrel

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Re: cheap gothic arch solar kiln
« Reply #4 on: May 01, 2017, 12:12:33 am »
I'll be watching this to see how it turns out.
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The winds of change are blowing at hurricane force and I don't like it but good shall come even though I see not how.

Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #5 on: May 01, 2017, 06:59:30 pm »
I'll be watching this to see how it turns out.

You like slow motion train wrecks, eh?


Cold and gusty winds today but I did a little site prep.

South side of the same old barn that currently houses my sawmill:


I do not like this stuff at all:


But I do like this young feller:

Have to try to avoid hurting that.

After some mowing and picking up some scrap wood:

(What? You were expecting grading, gravel and concrete?)

This stuff is still there. I want it to die by slow cooking.


Preliminary site prep done! Black plastic stapled to the barn (hence the compressor and generator) with a few concrete blocks to hold it in place. The wind rolled the blocks over by this afternoon so I'll be putting a few battens on the barn before the arches.



I need to cut some 4x4s for a base for a stack of lumber. Don't trust my felling abilities in gusty winds like today, so I just caught up on some mowing the rest of the day.

Offline Darrel

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Re: cheap gothic arch solar kiln
« Reply #6 on: May 01, 2017, 08:56:16 pm »
As long as my train of thought is involved in the slow motion train wreck, we'll be fine!

 :D :D :D :D :D
1992 LT40HD

The winds of change are blowing at hurricane force and I don't like it but good shall come even though I see not how.

Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #7 on: May 03, 2017, 10:35:08 pm »
Yesterday was a bust. Went walking through the woods scouting for likely trees from which to make a good base for drying lumber. Found a couple...

An oak, dead and standing near the base of a pond dam:


It's about 17 inches DBH.


Just down the hill about 30 ft, the top of a tulip poplar:


And the tree it came from:


That's about 19 inches DBH.

Both in this picture, the oak is partially obscured behind greenery to the right of that bleached looking tall stump:


Both tops (sweet gum obscuring the broken top of the poplar):


Angle showing a crook at about 8.5 ft up the poplar:


Even with the crook, I think those two would provide suitable lumber to frame up a base. The poplar looks to have a good 10 ft log above the crook. It would be a bear to get them up that steep slope.

By the time I got back to the house to eat breakfast and catch up on the Forum, the wind was gusting 30 mph. I'm not a lumberjack. When the tops of trees are randomly dancing around, I don't cut trees.

Don't think I should delay any longer, so, time for plan B...

Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #8 on: May 03, 2017, 10:54:29 pm »
Here's plan B:



That's what Lowe's calls "whitewood". It's from my store-bought cache of lumber earmarked for my garage extensions. Now this thing has bought EMT, bought plastic, and bought lumber. Should have left "cheap" out of the title.

Heckuva lumber truck:


Might not look it, but that's level in both directions:


Close enough:


It's sitting on concrete blocks and various bricks and treated 2x stuff at the 4 corners, only. I'm not worried about frost heaving but I do think it will need supports at mid-span for each 2x6.

I'm only going to try to get up half of the thing. Rain is supposed to roll back in tonight and hang on for a while.

Oh, by the way, if you have mud dauber wasps, a tire valve cap frustrates 'em when they try to take over your air tools:


I had a choice: use 1/4-20 x 2 inch carriage bolts on hand, or spend half the day going to and from a town to get suitable hex head bolts. Carriage bolts went in the ridge connectors.
Doesn't take up much room like this:


Easy way to get the 3 arches to cooperate:


Welders like to believe that their work holds the world together. The rest of us know it's Duck tape and baling twine:


Roll it over...


Set it on the wood:


Add some stop blocks to the wood frame, and add the girts to the arches:


I think it will sit there without attaching it to the wood frame, as long as I leave off the plastic. Don't want it becoming a strange parasail.


Have to wait and see what the weather does now.




Offline Darrel

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Re: cheap gothic arch solar kiln
« Reply #9 on: May 03, 2017, 11:21:45 pm »
That's gonna be one nice green house I mean kiln!  Lookin good 8)
1992 LT40HD

The winds of change are blowing at hurricane force and I don't like it but good shall come even though I see not how.

Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #10 on: May 03, 2017, 11:39:06 pm »
Oops! I was so caught up in making sure to get the pics in order I left out a bunch of details.

The arches were assembled on the porch. They like to twirl around if you don't put them on a flat surface while drilling and bolting them to the ridge connectors. Simple jig: two wood blocks screwed to the porch right against the house siding, spaced 9 ft. 6 in. apart. (Don't tell my wife they're there). I used a couple of retainer wall blocks to hold the conduit flat.

Holes were drilled by just eyeballing about 3/4 in. from the end of the connector; step drill bit in my impact driver made the initial hole, 1/4 inch twist drill bit in a cordless drill pushed through to the other side. 1/4-20 x 2 carriage bolts, 1 per leg, tightened until the end of the bolt was flush or 1 thread protruding. Actual O.D. of 1-1/2 (nominal trade size) EMT is 1.740 +/- .005. (All connectors are made from 1-1/2 EMT, the rest of the arches, ridge, girts are 1-1/4 EMT).

The two rim joists are 2x6 x 10 ft. Regular joists are 2x6 x 9 ft. 3 in. at 24 inches on center. All crowns up. Shot with 3-1/4 x 0.131 (16d short) coated nails via pneumatic nailer (where were those when I was building my house and garage?!), 3 per end per joist.

Ridge pole is 10 ft EMT (minus whatever they short ya). Girts are 57-3/4 inches. If I was putting up the whole 20 ft structure at once, only the end girts would be that length and all others would be 58-1/2.

Other than the bolted ridge connectors, the only things holding that structure together right now are Duck tape and gravity.

Let me know if I've left other stuff out.

Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #11 on: May 03, 2017, 11:40:12 pm »
That's gonna be one nice green house I mean kiln!  Lookin good 8)

Thanks! That's why I have it *behind* the barn. If she sees it, it will be filled with cacti and weird green stuff.

Offline ChugiakTinkerer

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Re: cheap gothic arch solar kiln
« Reply #12 on: May 04, 2017, 02:19:40 pm »
I like this, and see a way to make use of it at my place.  I have the tarp from a "portable garage" that collapsed from snow weight.  I can rebuild the frame using EMT ala grouch.  Is the ridge angle around 120 degrees?
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Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #13 on: May 04, 2017, 06:49:54 pm »
Somewhere up there is a photo of my working sketches. I drew the arch out full size on my garage floor before ever making the first one. The ridge angle is exactly 118 degrees, based on that.

There's quite a bit of wiggle room; 1-1/4 EMT has an O.D. of 1.510 inches and 1-1/2 EMT has an I.D. of 1.610 inches. I cut the connector legs about 5-7/8 inches long but they could be shorter and still work well.

[Edit to add:]
I used a 1-3/4 inch hole saw in a milling machine to cut the fishmouth joints for welding. No pilot bit in the hole saw, several teeth missing (prior use in a drill press but poorly clamped part).

Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #14 on: May 09, 2017, 10:48:49 pm »
Malfunctions, disruptions and interruptions make for a fine day. Probably should've stopped after the 2nd broken drill bit, but I never claimed to have good sense.

Got the frame blocked up including an oak 4x4 running under the middle, resting on 3 concrete blocks. Each 2x6 now only has to carry a 5 ft span.

Started putting some 1/2 inch x 1-1/2 inch oak strips on the arches to have a place to staple plastic. That's where all the frustration came in. Only got 3 up this afternoon, using some coarse thread 1 inch drywall screws I had on hand.



Clamps and twine pulled the oak up to the EMT for drilling and screwing.




That shadow of that cedar tree starts touching the frame at about 3 pm and has it covered by about 4 pm. Might affect how much heat this thing can absorb in a day.

At least there was something nearby to perfume the air (besides the red oak in use):


May have to revise my original plan for stapling plastic on the bottom of the floor joists. That could let too much air get back to the heating side without passing through the lumber stack first. I'm mostly guessing at everything in this experiment anyway, though.

Offline ChugiakTinkerer

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Re: cheap gothic arch solar kiln
« Reply #15 on: May 10, 2017, 01:46:25 am »
Sounds like you're maybe like the eagle in the video that was posted in a POSTONLT40HD thread.

http://www.forestryforum.com/board/index.php/topic,96078.msg1482455.html#msg1482455

Sometimes a fella gets an idea, jumps in with both feet, and just has to ride it out to its conclusion.
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Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #16 on: May 10, 2017, 07:15:26 am »
That eagle must've been real hungry or in need of glasses.

Don't think I've had that rough a ride, yet. The day's still young though.

 ;D

Offline Jemclimber

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Re: cheap gothic arch solar kiln
« Reply #17 on: May 10, 2017, 11:03:40 am »
Very nice project!! How much of a hassle was it to bend the pipe?

 Can you explain your thought process of stapling the plastic to the bottom instead of the topside. It seems like it would pull on the staples and tear more easily on the bottom versus the top.  I'm curious.
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Offline pineywoods

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Re: cheap gothic arch solar kiln
« Reply #18 on: May 10, 2017, 11:12:53 am »
Jem, I think he's using 2 layers of plastic, clear on top and black on the underside. 2 inch gap between. I use a similar system on my kiln, except the underside is black metal roofing.  Works well..
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Offline grouch

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Re: cheap gothic arch solar kiln
« Reply #19 on: May 10, 2017, 05:27:05 pm »
Very nice project!! How much of a hassle was it to bend the pipe?

It's thin wall conduit -- 1-1/4 trade size (1.510 inch actual O.D.), 0.065 inch wall thickness. I used the HF tubing roller which comes with a set of 1-1/2 inch dies that fit this size conduit closely enough to work. It takes rolling 'em back and forth through the roller multiple times, but is not hard work.

Quote
Can you explain your thought process of stapling the plastic to the bottom instead of the topside. It seems like it would pull on the staples and tear more easily on the bottom versus the top.  I'm curious.

This:
Jem, I think he's using 2 layers of plastic, clear on top and black on the underside. 2 inch gap between. I use a similar system on my kiln, except the underside is black metal roofing.  Works well..

Except in my case it's 1/2 inch wood + 1-1/2 inch tubing + 1/2 inch wood, so a 2-1/2 inch gap. Plus or minus the waviness I cut into the wood. :)

Maybe I'll get lucky and the curvature of the wall will help with efficiency of gathering heat.

Storms are headed this way. Stuff keeps interfering with my playing.