Wood

[wcndave]

Got some cherry, pear and plum wood from a neighbour, and it was very very wet indeed.

It's been sitting there for a month, and now I need to do something with it.

I was thinking about a controlled split by cutting lengthwise halfway through, however 1) the pieces are not straight, 2) I am not sure with small pieces like this I will get halfway and 3) I am not sure how safe it is to chainsaw rip cut.

Any thoughts or different techniques? This stuff is going to split like mad at some point!

Thanks

Dave

 

[Jelly]

Seal the ends (I use liquid latex, or roofing bitumen), then de-bark it, get it up on something to give good airflow and leave to season out of the sun as you would sawn and stickered boards; I've got some oak about a foot in diameter where I've done that, the m/c is down to 35% from 140% in about a year (measured using an oven and balance on a thin section off the end of the log).

 

[Random Orbital Bob]

You can certainly rip cut logs with a chainsaw as long as they're held securely. You will need a well sharpened blade mind. You'll want to remove the pith with the splitting action because that's what causes the most shrinkage stress. Then as the other advice was....still wax the end grain and get them into some air flow and under cover. The rough rule of thumb for air drying is 1 year per inch of thickness but that's density (species) dependant of course. It does give a rough guide to the scale though.

As sure as eggs they'll split badly if left alone without any processing.

 

[Phil Pascoe]

Jelly - surely a m/c of 100% would be water? How did you get 140%?

 

[Sgian Dubh]

Jelly - surely a m/c of 100% would be water? How did you get 140%?

Within the outer skin of a log there can be more air space than wood tissue, which may be filled with water, therefore you can get MC levels of 100%+. Certain wood species can record an MC up to 400%, eg, balsa wood. Slainte.

 

[JakeS]

more air space than wood tissue

Presumably the distinction is that it's measuring what percentage of water there is compared to the amount of wood, rather than an MC measurement being a percentage of how much of the total volume is water?

 

[Sgian Dubh]

more air space than wood tissue

Presumably the distinction is that it's measuring what percentage of water there is compared to the amount of wood, rather than an MC measurement being a percentage of how much of the total volume is water?

Something like that. I think I would rephrase what you've said thus: within the shell that the piece of wood occupies it's defining the amount of water there is compared to the amount of wood, expressed as a percentage.

For example, if you take a block of wood that occupies a space of one square foot, and within that square foot space the voids amount to three quarters of the volume then the wood fibres only occupy one quarter of it.

To calculate the moisture content of wood you need to know the following information:
• Initial wet weight of the sample, (WW)
• Oven dry weight, (ODW)
The sum to calculate the moisture content percentage is below, where WW is Wet Weight of the sample, and ODW stands for the wood sample’s Oven Dry Weight:
MC% = ((WW – ODW) / ODW) X 100

For example,

• Wet Weight = 247 grammes
• Oven Dry Weight = 183 grammes
Calculate, ((247 – 183)/183) X 100 = 34.97%MC, or 35% to the nearest half a percent.

It's important to understand what the formula above calculates: it uses the weight of completely dry wood as the base weight and figures how much extra weight is the result of the water in it, and what percentage this water forms over the dry wood base weight. Slainte.

 

[Jelly]

Jelly - surely a m/c of 100% would be water? How did you get 140%?

As Richard has already comprehensively explained, the m/c measures the amount of water relative to the amount of dry solids.

So 100% m/c is a log which contains the same weight in water as it does timber, 50% m/c would be half the weight in water as there is in wood and so on; calculating the percentage by mass of water would be misleading, as the mass would decrease as the water content did.

As demonstrated by this chart, m/c to water content is a linear relationship, where as % by mass water to water content is logarithmic... whilst that doesn't count against it from any statistical point of view, the simpler relationship makes the m/c values easier to interpret consistently in your head.
(blue is % m/c, red is % by mass)

(the data i used for the graph is here it's just made up to illustrate the point.)

 

[thomvic]

Forget the geeky measurements above. "a thin section off the end of the log" is unlikely to be representative of the whole anyway. Seal the ends to help reduce splitting - it is unlikely you will completely prevent it with fruit wood - weigh each log and label it. Stack in a dry airy place for a few months or years if your logs are large. Weigh again and calculate the weight loss. Then weigh regularly - say monthly. When the weight loss between weighings ceases or at least becomes very small you have got the moisture content as low as you will need it.

Richard

 

[Shrubby]

Dave
I always seal the ends with old gloss paint - usually a horrific retina searing colour from a bygone era
Bark the stuff with a drawknife or axe
Matt

 

[wcndave]

Thanks guys. Under cover outdoors or indoors? At the moment it is in a barn.

Not sure what paint I have, probably some old water based wall paint, would that do.

Rip chain sawing top the pith in a twisted log seems to much trouble.

Given I will use for turning, is there any benefit in simply cutting them down the middle?

Thanks for suggestions so far!

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[wcndave]

De-barking with draw knife proving difficult where there are knots and stubby branches and where there are concave parts to the trunk. What's the purpose for removing bark? If to let the water out the sides then I guess 90% is ok. If it's because removing later is harder once sap dries then I will probably leave and only remove with bandsaw from the few good pieces I actually use...

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