estimating timber volumes

[smojo]

I'm trying to finalise my FC thinning application and struggling with the timber volume section. They provide a guide chart which is pretty useless in my case. The chart quotes volumes for different tree heights with various "mid" diameters. Firstly how do you measure the mid height diameters without climbing ladders and secondly the ones I'm struggling with are long but narrow sycamore stems in a planted stand. Mostly about 12-15 cms at chest height but about 20m high. The chart doesn't quote figures for such tall but thin trees. Does anyone know a better way please. It's holding me back with my application now and I can't even guess as I have no reference to base it on.

[Dexter's Shed]

Does anyone know a better way please..

yeah, we didn't ask in the first place

[oldclaypaws]

The maths formula for volume of a cylinder is

volume = Pi x radius squared x height.

If you have a guess at the average radius (half the diameter) of the trees and do all the measurements in metres, its not too difficult.

Using your 15cms diameter x 20 m example,

volume of one tree = 3.141 (pi) x 0.075 (half of 15 cms, in metres) x 0.075 x 20

= 0.353 cu metres, or three of those trees makes 1 cu metre.

On the other hand, I think I prefer Dexters method.

[Rankinswood]

Use frustrum of cone modified by stem factor.

Rankinswood

[smojo]

Use frustrum of cone modified by stem factor.

err yeah, right thanks. Paws method sounds reasonable and I can understand it!

[oldclaypaws]

Calculating the butt volume of 'Rex', my veteran oak, yields a rather surprising number.

Butt height = at least 10 metres

Butt radius (half diameter) = 0.8 Metres.

Volume = 3.141 x 0.8 x 0.8 x 10

= 20.1 cubic metres !!

Better put a TPO on him, subsequent owners might do a quick value calculation and realise if he's good timber he's worth a bomb chopped. You'd lose a lot in felling and planking, but Hewins of Lopen sell their planked oak for £1400 per cu metre, that makes Rex tempting to someone to have a pop at. Fear not Rex, you're safe with us, I'd consider it sacrilege to even think of felling such a massive ancient living thing. Each of his upper boughs is as big as a large oak, so in total I reckon there's possibly 40 cu metres of wood there. (and a lot of prime habitat).

[andrewnoblewood]

Hi All,

Posted this yesterday in the felling licence exemption thread. Might be of some use to those of us without maths degrees or even O level or CSE maths for those of us ' matured' enough to remember them...

http://www.forestry.gov.uk/pdf/timbervolume.pdf/$FILE/timbervolume.pdf

[Rod Taylor]

My interpretation of the less than 10cm diameter for thinning carried over to the larger trees. The 15cm diameter trees although 20 metres high would be less than 10cm diameter above around 6 or 7 metres so would be discounted, and worked the volume out only for the length of trunk greater than 10cm diameter. Which basically means three times as many trees as OCP's calculation is within the limit. Is this a wooppps did it wrong moment ??
Have since received felling licences and found the Forestry Commission very approachable and helpful in getting these, which remove all worries about keeping a running total of the amount cut.

[oldclaypaws]

The 15cm diameter trees although 20 metres high would be less than 10cm diameter above around 6 or 7 metres so would be discounted

Nope. The exemption applies to trees which are within the permitted sizes at 1.3 metres from the ground, and the 15cm only applies to coppiced trees, for thinnings its 10cm and for all other trees 8cm.

[Mooresey]

What about estimating weight, say a square meter of oak?