Sunday, December17, 2017 L-36.com

Jib Turning Block Calculator



This page relies on this math, a little trig, and a lot of programming.
by Allen Edwards
2/16/2008
Use at your own risk. It has been debugges but may stil have errors. The bright side is that it doesn't matter that much as you can adjust it when fitting it by putting the lines on and alighning it for a good lead angle. As of this date, I have checked all the sections with a variety of test cases.
Allen
Use this table to enter the locations of the three components of the jib sheet system. The X axis is aligned with the axis of the turning block in that the long axis of the physical block will end up pointing down the X axis. What I did was make measurements on deck, then rotate those measurements to align the block the way I wanted. There is a section at the bottom to make the rotation calculations. To get the sheet angle where you want it, you can play with the spacing from winch to turning block and the block height. Be sure to check the pad heights so they are not too low, or even under the deck, and not too high so you can't get bolts long enough.
X Y Z
Winch
Car
Turning Block
Input the diameter of the Shieve:

The equation of the plane is: -53.85 * X + 99.84 * Y + 571 * Z + -976.41 = 0
Sheet angle winch to turning block is: 5.85 degrees (Line on block is at -0.15, -1.65, 1.99)
Sheet angle car to turning block is: 2.51 degrees (Line on block is at -0.52, 1.57, 1.39)
Solve for a point on the plane:
X Y Z
5.83

Find lead in angle between a point on the plane and another point:
X Y Z
1.39
Angle between points is 1.05 degrees
Angle between poins on plane at these x,y locations is 4.29 degrees
Difference is 3.24 degrees
Some hard coded analysis here (Papoose only):
Angle to car1 (22, 11) = 3.78, -2.67
Angle to car2 (35, 11.5) = 2.51, -0
Angle to car3 (75, 11.5) = 1.21, 2.83
Angle to winch2 (39, -1.72) = 8.02, -2.61
Angle to winch3 (39, -5.28) = 7.99, -1.71
Use this to calculate pad edge lengths where lengths are normal to foot block and pad is aligned with X and Y axis
Enter the edge X and Y locations in the 4 edge entry areas. These numbers are relative to the center of the turning block, not absolute locations.
Enter plane to pad offset in center
1.43 0.71
2.18 1.46
washer wedge is at 11.2 degrees and tangent is 0.2
Enter a position on the face of the pad to get the thickness of the pad normal to the pad top.
Use this to calculate the length of a bolt, for example.
Note: X* and Y* are measured on the sloping surface of the pad, not the deck.
X* Y* Z*
0.92
height of pad at that point is 0.9
Enter a second position on the face of the pad to get the thickness of the pad normal to the pad top.
These numbers are relative to the center of the turning block, not absolute locations. Use this to calculate the length of a bolt, for example.
Note: X* and Y* are measured on the sloping surface of the pad, not the deck.
X* Y* Z*
2
height of pad at that point is 1.97
Rotate a coordinate system to align at another angle:
angle
X 36.33
Y 8.97

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Disclaimer:
The information on this web site has not been checked for accuracy. It is for entertainment purposes only and should be independently verified before using for any other reason. There are five sources. 1) Documents and manuals from a variety of sources. These have not been checked for accuracy and in many cases have not even been read by anyone associated with L-36.com. I have no idea of they are useful or accurate, I leave that to the reader. 2) Articles others have written and submitted. If you have questions on these, please contact the author. 3) Articles that represent my personal opinions. These are intended to promote thought and for entertainment. These are not intended to be fact, they are my opinions. 4) Small programs that generate result presented on a web page. Like any computer program, these may and in some cases do have errors. Almost all of these also make simplifying assumptions so they are not totally accurate even if there are no errors. Please verify all results. 5) Weather information is from numerious of sources and is presented automatically. It is not checked for accuracy either by anyone at L-36.com or by the source which is typically the US Government. See the NOAA web site for their disclaimer. Finally, tide and current data on this site is from 2007 and 2008 data bases, which may contain even older data. Changes in harbors due to building or dredging change tides and currents and for that reason many of the locations presented are no longer supported by newer data bases. For example, there is very little tidal current data in newer data bases so current data is likely wrong to some extent. This data is NOT FOR NAVIGATION. See the XTide disclaimer for details. In addition, tide and current are influenced by storms, river flow, and other factors beyond the ability of any predictive program.