Loggers Preferences were based on yarding distance, topography (uphill or downhill), and ease of harvest.  Clearcuts generally have the fewest hang-ups and the highest payloads.  Light thinnings typically incur more hang-ups and lighter turn weights.  Logging utility values used to produce the numbers in the table were extracted from “Setting Design Evaluation Incorporating Pacific Northwest Loggers’ Preference” by Dean Rae Berg, Independent Forest Contractor, and Peter Schiess, Professor of Forest Engineering, University of Washington.  The utility values did not reflect loggers perceptions regarding full/partial suspension or varying thinning densities.  Further surveys need to be completed to get a more accurate picture of true preferences on these issues.  Variable density as well as uniform density should also be addressed.

Given these tables of preferences, each profile can be analyzed and the optimal prescription applied for the varying conditions.  The minimum distance for any prescription should be 300 feet as a rule.  Washington State Administrative Code Chapter 296-54 states that cutters must be at least two tree-heights apart.  (The site trees for the area were found to be approximately 150 feet.)  A minimum distance of 300 feet would allow one cutter to cut a specific prescription while another cutter may safely work on a different prescription.

Some of the assumptions that I made when compiling the tables:

n        No harvest beyond leave areas 500+ feet from the landing

n        Loggers prefer leave trees toward the tail ends of the unit

n        Loggers prefer heavier thins to lighter ones (higher payloads)

n        32’ logs were assumed.  Tree length would cause more problems in partial suspension areas

n        Thinning densities were arbitrarily assigned to give a range of possible prescriptions and are subject to change to fit specific managerial objectives.

n        The cut-off between side-hill and either uphill or downhill has not been defined and at this point is a judgment call of the engineer or manager

 

Table 30.  Loggers Preference Matrix.  See assumptions and definitions at bottom of table.

Uphill Cable Yarding - Loggers Preference
RMD		leave	20-30	30-50		50-70		70-100
<500	fly	2	1	1		1		1
	drag	2	2	2		1		1
500-1000	fly	2	2	2		1		1
	drag	2	5	4		3		2
1000+	fly	1	4	3		3		2
	drag	1	5	4		3		3
Downhill Cable Yarding - Loggers Preference
RMD		leave	20-30		30-50	50-70		70-100
<500	fly	3	2		2	2		2
	drag	3	4		3	3		2
500-1000	fly	3	3		3	2		2
	drag	2	4		4	3		3
1000+	fly	1	5		5	4		4
	drag	1	5		5	5		4
Uphill-Sidehill Cable Yarding - Loggers Preference
RMD		leave	20-30		30-50	50-70		70-100
<500	fly	2	1		1	1		1
	drag	4	3		2	2		1
500-1000	fly	2	3		2	1		1
	drag	2	5		5	3		2
1000+	fly	1	4		3	3		3
	drag	1	5		5	4		3
		leave	20-30		30-50	50-70		70-100
<500	fly	3	2		2	2		2
	drag	3	4		4	3		2
500-1000	fly	3	3		3	2		2
	drag	1	4		4	3		3
1000+	fly	1	5		5	4		4
	drag	1	5		5	5		4
Assumptions
Values are based on loggers preferences for
distance, topography(Uphill, downhill), and
ease of harvest.  Clearcut being the easiest with
the fewest hangups and lighter thins being the
most difficult
Loggers prefer to harvest higher volumes
the worst uphill is better than the best downhill
Assuming 32' logs
Note:  Tree length will make
dragging less favorable
Assuming no harvest beyond leave areas out 500+ feet
Good   Bad
1 ------>  5
Definitions
1= Paydirt!
2= Not my ideal but I'll do it for a beer
3= At least a 6 pack
4= Damn Engineers
5= I'd rather be watching Oprah!

  

 

Objectives:

1.      Harvest volumes for each prescriptions:

a.      No action

b.      Uniform thin to RD 40 or 40% change from original RD

c.      Light variable density thin (see DNR Procedures)

                                                               i.      10% skip, 10% gap, 30% to 33 RD, 50% to 45 RD

d.      Heavy variable density thin (see DNR Procedures)

                                                               i.      10% skip, 10% gap, 30% to 23 RD, 50% to 33 RD

e.      Experimental light variable density thin (see Big Country proposal- Richard Bigley)

                                                               i.      10% skip, 10% gap, 40% to 30 RD, 40% to 45 RD

f.        Experimental heavy variable density thin (“”)

                                                               i.      10% skip, 10% gap, 40% to 25 RD, 40% to 35 RD

2.      Average Tree Size (in board feet) of cut trees for each prescription.

3.      Average Log Size (in board feet) of cut trees for each prescription.

4.      QMD of tail tree rigging for each prescription.

 

Assumptions:

1.      Harvest volumes:

a.      SDI used to approximate RD.  Regression of SDI to RD resulted in equation: SDI=-2.453+5.880RD

b.      Most stands for uniform thin limited by 40% change from original RD.

c.      Weighted average used to determine all values from light and heavy variable density thins after each stand treated to a single SDI.  Weights based on DNR Procedures for skips, gaps, light, and heavy thinnings.

d.      See Procedure 14-006-080

2.      Average tree size determined by dividing total volume by the number of trees removed that accounted for some portion of the total volume (8” DBH or greater, because LMS volumes were SV6).

3.      Average log size determined by weighted average:

a.      (vol/log)(exp. factor)₁+…+(vol/log)(exp. factor)_n

Sum(expansion factors)

b.      Volumes from LMS were SV6, so bucking parameters were 16 ft. logs, 6” small end diameter, 1’ stump height, 1” trim.

4.      Tail tree rigging QMD determined by largest 50 trees (based on 30 x 30 ft. spacing) per acre including DF, WH, RC, SS.  QMD of DF and all other species determined separately.  QMD for other species reduced by 2” to account for reduced strength compared to DF.  Weighted average of DF and other species QMD’s (based on trees per acre) then used to determine QMD for stand.

 

 

  Now that the profiles are digitized into LoggerPC a payload analysis needs to be performed on them to ensure that suitable payloads can feasibly be achieved.  The ideal yarding situation is full suspension with a standing skyline and tailhold at stump level.  Therefore, this scenario is checked first.  If payloads meet or exceed the anticipated maximum payloads for clearcut conditions the analysis is done.  If not, changes need to be made until the design payload or the max possible payload is reached. 

Once you have LoggerPC open, click the profile pull down menu and choose open to bring up the profiles that were saved when they were digitized.  Select the one you want to analyze and click ok.  Next, click the yarder pull down button and choose the yarder and carriage you want to use for your analysis.  Lastly, click on Goto Analysis and the analysis window comes up.  In this window set the tailhold where you want it and the desired height.  The yarding limit may or may not be the full distance to the tailhold; the limits can be set by changing the terrain points to give the true yarding limits.  Now choose the type of yarding system you want to use (start with standing).  When you click on one of the types you will have the option to watch or run the analysis and also to change the payload and line length.  Set the payload to the desired amount and try to run the analysis.  If the payload is not possible an error message will come up and you will have to make some changes.  If the payload is possible it will run, but LoggerPC does not check to see if the skyline tension is within the SWL, so you will need to know what the SWL is for the line size that you are using.   Increasing the line length will reduce tension and decreasing line length will increase tension.

 If you have tried standing skyline, full suspension and are not able to get the desired payloads, the first change to make in LoggerPC is to try raising the tailhold height to get the necessary deflection for full suspension.  Try raising the tailhold height to 30 feet and check for clearance and payload.  Next try 40 feet, and finally 50 feet.  If the desired payload is still not met the next adjustment to make is to switch from full suspension to partial suspension and drop the tailhold height back down to two feet (stump height).  Again, adjust the tailhold height up incrementally from two feet to 30, 40, and then 50 feet.  If none of these adjustments work, the next option is to go to a multispan system.

A multispan system will ask for locations for intermediate supports and heights.  By looking at the profile, try to locate the terrain point with the worst deflection and place the intermediate support there.  The minimum and starting height should be 30 feet.  Run the analysis on the multispan system and see what kind of payloads can be generated.  If they are not what you need try moving the intermediate support around to different terrain points to see if you get better results at different locations.  When you find the location that provides the highest payload and if it is still not adequate then increase the height of the intermediate support to 40 feet and run the analysis again.  If not enough try 50 feet.  For practical rigging purposes do not exceed 50 feet rigging height for intermediate supports or tailholds.  If the desired payloads are still not met add an additional intermediate support where the deflection is poorest and repeat the process above until design payloads are met. 

The last method to try is live skyline.  It will produce the highest payloads of the three methods but is inadequate for most thinnings.  Live skyline works well for clearcuts or heavy partial cuts.  If live skyline must be used try to get full suspension.  Use a series of lifts if necessary to gain the best deflection.