iDRY Vacuum Kilns

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kiln fans

Started by hackberry jake, April 15, 2014, 11:15:38 PM

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WDH

Nope, no slab or other weight.  I have had minimal problems so far.  I don't think that weight relieves tension in the wood. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

YellowHammer

I don't use additional weights, either.  About the only thing I do, and is one of the advantageous of the pallet method, is to reverse the order that I stack the pallets in the kiln opposite of when I'm air drying them and use their weight to my advantage.  In other words, the top pallets of lumber in the air drying area go on the bottom of the stack in the kiln. If there is any cup, that helps flattens them.  I think the best way to keep lumber flat is lots of stickers, drying and sawing technique.

YH

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

thecfarm

hackberry jake,going to cut the boat dock styrofoam blocks on the sawmill?? Seem like they are about a feet thick??
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

hackberry jake

Quote from: thecfarm on April 18, 2014, 09:46:24 AM
hackberry jake,going to cut the boat dock styrofoam blocks on the sawmill?? Seem like they are about a feet thick??
it sure is cheap insulation. Im kind of worried about the mess though.
https://www.facebook.com/TripleTreeWoodworks

EZ Boardwalk Jr. With 20hp Honda, 25' of track, and homemade setworks. 32x18 sawshed. 24x40 insulated shop. 30hp kubota with fel. 1978 Massey ferguson 230.

OneWithWood

Thanks for all the information.  You all have giving me some things to ponder. 
One With Wood
LT40HDG25, Woodmizer DH4000 Kiln

pineywoods

Quote from: hackberry jake on April 18, 2014, 10:46:12 AM
Quote from: thecfarm on April 18, 2014, 09:46:24 AM
hackberry jake,going to cut the boat dock styrofoam blocks on the sawmill?? Seem like they are about a feet thick??
it sure is cheap insulation. Im kind of worried about the mess though.

Jake, the way to cut that foam is with a hot wire. Piece of nichrome wire (heat element out of a defunct clothes drier). Stretch the wire taunt and hook a battery charger to the ends. The wire needs to be just barely red hot. I like to use a flexible piece of wood with the wire strung like the string on an archery bow. Leaves a nice smooth finish on the cut. Yer right, cutting foam blocks on the sawmill gonna be messy..
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
100k bd ft club.Charter member of The Grumpy old Men

kelLOGg

I found box fan bearings did not hold up to the heat so I use attic fans in a frame

As for weight on top, I use ratchet straps.
Bob
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

GeneWengert-WoodDoc

For fairly wet lumber (above 40% MC roughly), if the fans are providing 500 fpm velocity (about 10 mph), the wood will dry twice as fast as if the velocity is 300 fpm...at the same RH and temperature.  However, this higher air flow at 500 fpm will require more than 4 times more electricity than at 200 fpm.  On the other hand, faster air flow is also going to mean more uniform air flow, which can be helpful.

At around 30% MC and lower, air flow rates have no appreciable affect on the drying rate...what is taking time is the rate at which the water molecule can move from the within the piece to the surface...this rate is controlled by RH and temperature.  So, small fans will be adequate and will save money if the lumber is air dried before going into he kiln.

Here is a formula that can be helpful:

cfm = (air velocity in feet per minute) x (sticker thickness in inches /12) x (length of lumber in feet) x number of sticker openings (or number of layers of lumber + 1)

For good drying of wetter wood, a target velocity of 250 fpm is good, although for white woods like maple, 500 fpm will mean whiter in color.

Rearranging the formula

velocity through the load in fpm = (cfm from the fan) / [(sticker thickness / 12) x (length) x (number of sticker openings)]

For example, assume two fans at 850 fpm, 3/4" sticker openings, 20 layers, and one 12' lumber bundle.  Then, if there are no leaks of air, these fans will provide about
1700/[(.75/12)*12*21] = 108 fpm velocity air flow

--------------

Fan efficiency is an interesting topic.  With the same motor, you can get various amount of cdm from a fan.  Certainly, tight bearings can reduce air flow, but the clearance between the tip of the blade and the housing or shroud is critical...the bigger the gap, the more inefficient the fan (fewer cfm for the same hp).  Also, if the shroud itself is curved gently (so it looks like the throat of a carburetor if you are old enough to remember them), you can get perhaps 20% more air cfm.  Without the curve, the air generates eddies that result in wasted fan power.

Does blade diameter matter?  Once you are over about 20", diameter, there is no benefit in going large from an efficiency standpoint--that is, the relationship between motor hp and cfm is a constant.  However, large means you can add more power (large motor) and get more cfm, as the tips are moving so much faster.  With larger fans, the higher power means heftier frame and shafts.  Large fans also mean fewer motors, switches, wiring, etc.

Fan bearings are expensive.  That is why some fans cost more than the $20 box fans.  Box fans do not have bearings, but have bushings that tend to wear faster, as well as a weaker frame.  The motors also have less ability to withstand high RH conditions.

The most expensive fans will have blades that have adjustable pitch (using a wrench, etc.).  So, one adjusts the pitch prior to starting a kiln, to give the desired velocity without over-taxing the motor.  A large kiln should have an ammeter on each motor so that current draw can be measured and compared to the rating of the motor.  Note:  When starting a kiln with cold air, the current draw will be higher because the air is more dense.  On the other hand, velocity will be higher too.

Bottom line is that you basically get what you pay for, so all you need to do is decide what fpm or cfm you need and how big is your pocket book.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Larry

I used a old belt driven furnace squirrel cage fan.  No idea of the cfm or fpm other than a lot.  When I first built the kiln I experimented a bit with air flow using smoke and tissue paper to see what was happening.  I also varied the speed by changing out pulleys.  Had plenty of power with a ¾ hp motor.  Used an ammeter to see the effects of different size pulleys.  A motor with a light load doesn't use near as much juice as one loaded to its full load current rating.

The results of testing found if air flow was too low my bottom layers were drying at a slower rate than the top layers.  Tweaked the fan until drying was nearly even from top to bottom.

It's interesting that these solar kilns will dry wood to without any fans at all...just takes forever.  One fall I put a fresh load of lumber in the kiln but didn't turn on the fan because winter drying is slow.  Few months later I checked the load and was surpised to find it was actually drying.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Escavader

Our kilns have 4 giant 48 to 54 inch fans ,it's hard to keep  your hat on  :Dgood air flow in drying pine is important to avoid coffee stain
Alan Bickford
Hammond lumber company/Yates American A20 planer with dbl profilers Newman feed table multiple saw trimmer destacker automatic stacking machine Baker resaw MS log corner machine  4 large capacity Nyles dehumidification kilns JCB 8000 lb forklifts woodmizer lt 15 and mp100 and blower

GeneWengert-WoodDoc

One way to make a solar kiln work without fans is to bring in the outside air at a low point in the rear and have the bottom baffled so that the incoming air must go through the load.  Then, when the air in the front is heated, it will rise, so put a vent neat the top at the rear.  This hot air will rise and top out the vent and pull fresh outside air into the load.  It will be similar to air drying, but perhaps faster as there will be added velocity in some cases..  Plus, not all the air will exit the kiln, but some will recirculate a few times.  Overall, the air speed is slow, meaning slow drying, but it will dry the lumber.  Eventually, when the lumber is getting quite dry, the vents can be nearly closed which will build up heat in the dryer and thereby lower the RH and create lower final MCs, but again, it will take a while for this to happen without fans.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

hackberry jake

I originally planned on using two layers of 2x4 stud walls for the chamber construction (along with 1" blue or pink 4x8 wrap). I was goint to stagger the two bys so they didnt line up and fill inbetween with the boat dock foam. I am pondering using the 1x8s instead though. It would save money because I wouldnt have to buy 2x4s and it would give me about an inch more depth (full 8"). It would also be less cutting of foam and less assembly time. Any reason I cant use 1x8s as studs? Other than it will be a little harder to hit with a screw when im putting my plywood on...
https://www.facebook.com/TripleTreeWoodworks

EZ Boardwalk Jr. With 20hp Honda, 25' of track, and homemade setworks. 32x18 sawshed. 24x40 insulated shop. 30hp kubota with fel. 1978 Massey ferguson 230.

WDH

Should be fine with a good R-value.  A well insulated kiln is a more efficient kiln. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

caveman

https://www.sullivansupply.com/cart/ia/p-502-sullivans-24-turbo-fan.aspx
I have located a couple of fans similar to the one listed on the link above and I am curious if one of these would be enough to adequately move air through the kiln we are building if we construct the plenum and ducts to distribute the air.  The inside of the kiln chamber is about 20' long x 6' wide and 5' high on the short side and about 9' on the high side.  I do not mind using two but these things really push some air and I do not want to over do it.  I would appreciate suggestions from those who have already built solar heated kilns.  The search for the proper fans has stalled this project for several weeks.
Thanks,
Caveman
Caveman

WDH

You can buy 3 of the mechatronics fans that come in the Nyle L53 for the price of that one fan.  The mechatronic fans produce 850 CFM each. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

caveman

Thanks, WDH, for the lead on the fans.  I have located some of the fans like the ones on the link that I can get for free from a barn that I helped to tear down.  I do not mind buying new equipment but we try to spend sawmill money on the mill and kiln project and we are running low on sawmill dollars.  There are four of them available.  Two need blades but two are in good working order now.  I just did not know if they are compatible with our kiln or if they would be overkill.   These draw 4 amps and have 1/2 hp motors.
Caveman
Caveman

LorenB

Quote from: hackberry jake on April 17, 2014, 11:53:39 PM
No weight on the top of the stack in the kiln? I read someones post (dont remember who) where they poured a reinforced concrete slab that they pick up with the tractor and set it on the top of the load. I liked that idea.

My kiln is still under construction (has been for a few years now) but I'm slowly making progress.  A while back someone (may have been Don Lewis) told me about the possibility of using a waterbed mattress as weight.  You don't fill it until it's on the lumber and drain it before you tear the load apart. 

Sounds like a good idea to me, but I don't know how much a waterbed mattress will cost.  Probably cheaper than concrete though. 

-- Loren
Loren
Baker 3667D portable sawmill, Cook's edger, Logrite arches & peaveys.  Husky 272XP chainsaw & two Echos.

PC-Urban-Sawyer

Quote from: LorenB on July 06, 2014, 09:47:43 PM
Quote from: hackberry jake on April 17, 2014, 11:53:39 PM
No weight on the top of the stack in the kiln? I read someones post (dont remember who) where they poured a reinforced concrete slab that they pick up with the tractor and set it on the top of the load. I liked that idea.

My kiln is still under construction (has been for a few years now) but I'm slowly making progress.  A while back someone (may have been Don Lewis) told me about the possibility of using a waterbed mattress as weight.  You don't fill it until it's on the lumber and drain it before you tear the load apart. 

Sounds like a good idea to me, but I don't know how much a waterbed mattress will cost.  Probably cheaper than concrete though. 

-- Loren

Here's one (http://www.amazon.com/InnoMax-Sanctuary-Free-Waterbed-Mattress/dp/B00ARV4MZG/ref=sr_1_1?ie=UTF8&qid=1404826532&sr=8-1&keywords=waterbed+mattress for $50...


jueston

caveman, when i read your post, this is what i thought you meant....  :D

Quote
We are running low on sawmill dollars, There are four of them available. 



LorenB

Loren
Baker 3667D portable sawmill, Cook's edger, Logrite arches & peaveys.  Husky 272XP chainsaw & two Echos.

bedway

I have my kiln in the build stage and am thinking ahead as to temperature and humidity sensors. Ill have the kiln located just outside the shop and want to be able to view readings inside my shop. I don't want to mortgage my house to get these units but neither do I want el cheapo. Input please?

Larry

I have a Radio Shack indoor/outdoor weather station.  It has a wireless sensor.  The problem with any of these units is they won't read much if any over 120 degrees.  My unit has been working perfect for a couple of years and is fairly accurate.  I compared humidity/temperature readings to both the local National Weather Service and TV station.  I'm using my unit as a weather station and the outdoor sensor is on a covered porch so I don't know how it would stand up to humidity in a kiln.  I also don't know if the wireless unit will go through both a kiln wall and a shop wall. 

My unit is discontinued but I think virtually the same as this one.

http://www.radioshack.com/product/index.jsp?productId=23147756

I have a much older RS unit with a wired sensor that I did use in my kiln for over 10 years with no problems.  Its an antique as these things go, so no links to it.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

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