Form class, good form bad form??? a question for foresters, or scalers...

[northmanlogging]

Right then been using my own calculations for a few years now, its international but gets me in the ball park for weight more than anything. But now I'm looking more at what I'm getting scaled to at the mills, and guestimating whats on the ground or standing before I start a job. Most (if not all) the local mills use scribner decimal c. My question is what form class should I use for my area, I mostly work in snohomish/skagit counties Warshington, and is exceedingly rare that i work above 2000' lots of Hemlock, Doug fir, alder and ceder. most everything else I look at as a bonus, or firewood. um thanks...:msp_unsure::msp_biggrin:

 

[madhatte]

This is gonna sound pretty vague and I apologize in advance for that.

Form class is a taper estimate expressed in a percentage. 100% would be a perfect cylinder with no taper at all from top to bottom. 0% would be a flush stump. Most trees will take one of two basic forms: conical or spreading. Generally, the log under the crown of the former will taper in a more regular fashion where the log under the latter will taper abruptly at each fork.

Scribner, Doyle, International etc are all log rules; that is, they are used to estimate the volume the log contains AFTER it has been milled. That is, they are equations that compare height/length and diameter, subtract bark diameter and saw kerf, and account for void spaces that are just plain waste. These log rules necessarily include taper in the equation, but it is a derived value. It's not directly measured.

The big difference, then, between form class and log rules is that form class is something a forester uses to estimate standing volume where log rules are something a scaler or sawyer uses to estimate down log volume.

 

[slowp]

You can come up with your own form class, to use in cruising by measuring the bark thickness on a lot of trees.

Get out them climbing spurs:smile2:and climb up to the height mentioned in the article Madhatte referred to. Measure the diameter outside the bark. Then, with a trusty hatchet, chop through the bark and measure how thick it is. I can't remember the equation but I think it is in that item also and can easily be found.

That's how I had to do it in the days of one computer in the office that was the size of a piano that had to go through Ft. Collins.

Or, you can visit a nearby logging operation and do the same thing with no climbing.

Here is a link to an excellent manual on log scaling.

http://www.ibsp.idaho.gov/IdahoLogScalingManual-2008 Edition (print).pdf

 

[northmanlogging]

so each site would have its own form class? And that would have to be an average over the whole site, therefore not really any basic numbers to go off... just dead reckoning... unless I wanted to climb a few trees before bidding a job...

 

[slowp]

so each site would have its own form class? And that would have to be an average over the whole site, therefore not really any basic numbers to go off... just dead reckoning... unless I wanted to climb a few trees before bidding a job...

Yes, but the Forest Service already has form classes for much of the acreage. These are used by pulling up old info that was gathered in prior cruises and exams in the area. There might already be info for your area, somewhere.

We got in trouble for climbing--no proper training-- so a couple of guys went out and fell a few trees to get bark thickness measures.

 

[floyd]

You could get a Relaskop to measure the tops. I bet they are real expensive now.

 

[OlympicYJ]

Almost 2 grand now... Almost as cheap to go with the full laser setup from atterbury...

 

[madhatte]

Relaskop is the preferred method for non-destructive measurement. You just have to make the assumption that the bark tapers at the same rate as the wood inside of it. This is acceptable for stand exams but not for generating site indices.

It's also worth noting that there are currently no growth models for ANY hardwoods in R6. There are tarif tables, and they're OK, and there are site indices, but I have found them to be woefully inadequate. Hardwood cruises, then, are pretty much guaranteed to be less accurate than their softwood counterparts.


Not only are new Relaskops crazy expensive, they're constructed more cheaply than old ones. The one I use has a 4-digit serial number and metal rings around the windows, and has held a tune for three years now. I will say that using Tygon for the brake material was a stroke of genius. It gets neither gummy nor brittle with age. When it eventually fails, it just breaks. No shoddy measurements as it declines.

 

[OlympicYJ]

That's def a plus having it just flat break and not gradually wear over time! Have ya played with the tru pulse lasers any? pretty neat.

Speaking of site index, it seems there is a problem nowadays with the site indexes themselves. Models aren't puking out reliable data. General thinking is that the improved seed stock has thrown the indexes out of whack. Makes for some interesting head scratching.

Wet side that is. At one of the outfits I worked for the harvest planner was twiggin to the problem and brought it up in some discussions.

 

[madhatte]

I used a 200B for years and I am using a 360R now. TruePulse is a solid tool.

The old static site index idea is currently discredited. It is being replaced gradually by a dynamic model that compares "relative height" and "relative diameter" as local percentages. Hit me up if you want to know more about it; I'm not sure how much is published, how much is grey papers, and how much is proprietary. I can say with some confidence that there is a sea change coming soon in how inventory numbers are handled.

 

[OlympicYJ]

I used a 200B for years and I am using a 360R now. TruePulse is a solid tool.

The old static site index idea is currently discredited. It is being replaced gradually by a dynamic model that compares "relative height" and "relative diameter" as local percentages. Hit me up if you want to know more about it; I'm not sure how much is published, how much is grey papers, and how much is proprietary. I can say with some confidence that there is a sea change coming soon in how inventory numbers are handled.

Whoa that is pretty interesting! I'll shoot ya a PM unless you wanted to start a thread. Definitely didn't hear anything about this 2yrs ago when that question was being asked. Wait I may know a bit that goes inline with this. Not exactly site index but the timber co in shelton are going away from fixed rotation ages to a max growth potential on a stand by stand basis. Stand max's out it's growth and starts to slow down, that's when it gets killed. I know there is a specific term for it but can't think of it atm.

 

[madhatte]

Yes, PM is best, don't want to step on any toes. I'll try to find out what is and isn't public knowledge. Might take a few phone calls.

 

[OlympicYJ]

Yes, PM is best, don't want to step on any toes. I'll try to find out what is and isn't public knowledge. Might take a few phone calls.

PM sent