Thread: How Not To Air Dry Timber

Geese Paul, looks like a pretty goo way to air dry mate, yer so the stickers are a little off in places, but like ya say that happens and v.hard to stop.

Only thing for me mate is no straps on the timber, you dont use them mate?

Originally Posted by Sigidi

Only thing for me mate is no straps on the timber, you dont use them mate?

Allan

I'm not a fan of straps as they pull the timbers together. This means that there are no vertical gaps in the stack: Only horizontal gaps. To my mind this further restricts the performance of the stack with regard to air circulation and consequently drying as all that moisture tends to remain within the stack. Inevitably the centre and lower boards are going to have higher moisture content than the upper and outside boards.

I believe it is very important to allow drainage down through the stack.

Commercial stacks are not strapped. Actually commercial stacks tend to go straight into a kiln! However, in the days when there was an air drying component the stacks were set out like mine.

The exception to that is drying slabs and there was a recent thread where somebody posted pictures of several stickered and strapped stacks of slabs. Looked very tidy.

The guaranteed way to get the stickers evenly positioned is to have a stacking frame (Nifty posted pictures of one some time back), but that also assumes a regular use of similar size timbers to warrant the effort.

My original plan was to errect an improvised solar kiln over the top of the stack to finish the drying process. I may still do that depending on the moisture content when I measure it. The kiln drying is another reason for maintaining vertical as well as horzontal gaps. When you think about it the requirements for air drying and kiln drying are the same (within a little). Kiln drying is just an accelerated version.

Regards
Paul

All very good points Paul, missed ya call a bit earlier mate, I'll try ring ya while I'm at the mill tomorrow

How does one measure moisture content?

Originally Posted by Fricasseekid

How does one measure moisture content?

There are a couple of ways.

One is by a moisture meter, which relies on electrical resistence.
The other is by weight before and after drying.

I use the moisture meter.

Regards
Paul

Originally Posted by Sigidi

All very good points Paul, missed ya call a bit earlier mate, I'll try ring ya while I'm at the mill tomorrow

No problem.

Regards
Paul

Hi there

Over the years of improving my racking techniques, I have ended up with fully welded steel subframes with moveable cross members. The subframe is a standard 1200 across x 4000 long, but can be lengthened with screw in extensions (using old drill pipe). The cross members are standard 1200, but can be changed for wider ones if racking large slabs. The spacing can also be adjusted depending on what timber is being racked. They only take about 10 minutes to set up and are perfectly flat. Of course you have to invest the time and money to make them initially, but if it means you recover more timber because it dries straighter, they pay for themselves over the years.

When I finish sticking out a rack of timber, I wrap the rack in one layer of hessian. This protects it fom the sun, reduces wind speed through the rack (if we get a 40 degree northerly blowing through) and I find it produces a very even moisture content throughout the entire rack. I then use a thick PVC tarp (old underground mining ventilation bag) to cap the pack.

Finally, I use a downgrade timber, like 100 x 100, to go across the top of the pack, then fencing wire and gripples to strap the pack down, with the wire going completely over the top timber cross members and under the subframe so the pack does not pull together horizontally . As the pack shrinks slightly then wire can be easily restrained. I'll post a few pics later.

Cheers
James

James

Sounds like just the job. I'll look forward, as I'm sure will others, to seeing the pix..

Regards
Paul

if the bottom gluts and top gluts stick out a bit past the pack, a length of fencing wire run round them and tied off with a stick twitch in the centre of each for tightening as the pack shrinks. No side pressure on timber.

I was thinking along the same lines as Al as far as a good looking stack, the misalignment of some sticks doesn't look like it has caused any drama to the boards as far as an unwanted curve goes, probably at 55 thick they will tolerate a bit of misalignment, for 1" may cause more probs,
the only thing I do different to what you have there is put a sticker on the (joist) for the first board to sit on, means I can add/adjust joists a little easier if needs be, not a huge thing but one of those little things that make up the whole.



Pete

Hi guys

A few pictures of some racks partly finished, but when I head out to the farm next I'll take a couple of detailed photo's. As Rustynail mentioned, the top gluts are about 1250 long, just hanging over the edge of the pack and clearing the rack sticks. The bottom subframe is welded at 1200 apart and the racked timber sits 25mm inside the rack edge, meaning there is no contact or pressure from the tie wire horizontally, only vertically.

The pipe I use is 70mm diameter with a 5mm wall thickness, extremely strong. I can rack up to 3m high of redgum boards without the rack even flexing. The rack is designed so that all load is transferred through the x-sections of the pipe, and no weld comes under shear load. This provides added safety while racking, as even if a weld breaks for some reason, the rack will not fall over. The pipe also has the benefit of being temite resistant, and easy to see if any are tracking over them. The termites are so bad at the farm a Dutch friend once lost the soles of his clogs just walking to the outside loo!

I also put a forklift spacer halfway up the rack so I cat split the rack easier at a later date to move into the shed. The racks are 300mm off the ground as we are also in a floodway, and the 2011 floods that hit Central Vic went right over the rack legs and subframe, but not the cross members and timber. Just lucky I suppose.

Boards are racked with 42 x 19 pine sticks. In bulk, they work out at about 10c per stick, and at this rate I figure it's not worth wearing out the mill and my legs. Slabs are racked with the natural edge trimmings from milling 40mm boards. I collect them all at the end of the day and cut them to length and put them the thicknesser at 38mm so every stick is exactly the same. This avoids actually cutting dedicated rack sticks, every miller's nightmare.

As you can see, my 3 year old site foreman with the pink beanie keeps a close eye on the racking, and is quick to point out if one rack stick is out of place. She is all over quality control and safety, making sure I take the appropriate meal break by supplying a loaded picnic basket!

Why is it that kids are attracted to piles of sawdust, I'll never know. It always starts with 'Dad, can I play in the sawdust?' and ends with 'Dad, I've got sawdust in my gumboots, can we go now?' Got to love 'em.

Cheers

James

Excellent job James.

More pix will be most welcome. Good to see that good help is available in your area.

Regards
paul

Here are a few pics of a finshed rack, with picture of the leg set-up and wider cross members. All racks are labelled with a cowtag, describing where and when the timber was milled, species, size and quality. It is very easy to forget a few years down the track. If anyone is interested I can get this heavy gauge pipe pretty cheap, and they are welcome to copy or improve the design of the rack.

Cheers
James

James

Those racks look really good. I like the small pieces of angle placed so welding the round pipe is easier. I have to resort to that as i don't have a mig welder (one day maybe).

BTW I noticed you have flat ground. Wonderful. Everything I have is on slopes.

One thing I should have mentioned regarding my stack is that my stickers are a little on the narrow side. The recommendations are that they should be between 16mm and 20mm thick and 30mm to 38mm wide. The thickness regulates the speed at which the timber dries with narrow stickers increasing the time and thick stickers reducing the time. My book does make reference to going up as far as 30mm thick for easy drying species, but also reducing fto less than 16mm for difficult timbers.

The width is to prevent the stickers "bitting" into the planks. However this, I feel, is more a problem for the commercial installations where there is much more weight involved with the increased height of the stacks. If the stickers are too wide there is a tendency to produce wet spots where they sit and consequent checking either side of the stickers. It is also more wasteful of material unncessarily. It is surprising how many stickers you need as those of you who have set up drying stacks will know.

Regards
Paul