The first Web page dealt with static tensions, and the second with jibstay sag and jib draft.  The final step is to calculate what happens to the jib leech as the wind increases.  The "Twist" worksheet of the spreadsheet uses formulas from the "Leech.xls" spreadsheet (see the Leech page) to calculate how much twist is introduced into the middle of the jib as the topping lift shortens.  First, the worksheet estimates the twist set into the jib from the gap given in the default rig parameters section, and estimates how much the topping lift has been shortened or "lifted" to get that.  The example shows a gap of 35 mm, a twist of 9.95 degrees, and the calculation that the topping lift was shortened 1.96 mm to achieve it.

Then, given the amount by which the jibstay has stretched, the worksheet calculates how much the aft end of the boom has lifted, and calculates the dynamic twist in the middle of the jib.  The aft end of the jib boom only lifts when the jib forces overcome the topping lift tension, so the spreadsheet suppresses any movement of the boom until the topping lift tension reaches zero.  In reality, as very small values of the topping lift tension are reached, the jib boom will move and the jib will twist off, so it isn't the "on/off" "light switch" that the spreadsheet supposes.

The various cells of the spreadsheet illustrated calculate a linear interpolation of the estimated twist, given upper and lower boundary estimates by lookup of the table in the worksheet.

In calculating the new twist of the jib, the spreadsheet notes that the sag of the jibstay has the effect of lessening twist.  That is, the jibstay sag "moves" the jib luff to leeward, decreasing twist.  The amount of this movement is deducted from the leech gap, and the new twist estimated.

The example illustrated shows the jibstay sag to have moved the jib luff about 8.17 mm to leeward, and the new twist in the middle of the jib is about 7.6 degrees, having started at about 9.95 degrees in the static condition.

The "JS sag" worksheet provides a button (labelled "Leech twist") to activate the macro which populates cells to show the leech twist as a function of wind speed.  The following graph shows the jib twist for a pivot offset of 72.5 mm in No.1 rig, with backstay and shroud settings as previously.  The graph illustrates that the topping lift "releases" at a wind speed of around 16 ft/s, and that thereafter the jib twist climbs -- the leech has bagged out.  Note that the calculations are for the middle of the jib, so the head of the jib has twisted off even more, probably about 30% or 40% more.  But note that, before the leech bagged out, the jib twist was systematically reducing as the jibstay sagged, down from around 10 degrees to around 7.5 degrees.  Hmmm...

The second graph shows the cumulative effect of increasing jib draft and decreasing leech twist upon the entry angle of the jib.  It estimates that, at very low wind speeds, the entry angle of the jib was about 26 degrees, being made up of about 16 degrees due to jib draft, and 10 degrees due to jib twist.  Remember we are talking about the middle of the jib here.  Then, at a wind speed of about 14 or 15 ft/sec -- top of A rig -- total entry angle is around 36 degrees, made up of about 30 degrees due to increased jib draft and 7 degrees of decreased jib twist.

The major use of the spreadsheet is to experiment with various tensions and pivot offsets, so as to retain the required jibstay sag while setting the point at which the topping lift will release and allow the jib leech to bag out in the gusts.

All of the graphs can be calculated at once by using the "Do all" button located on the "Tensions" worksheet, just below the rig parameters box.  The spreadsheet is most effectively used by setting the various rig parameters as needed, and then clicking the "Do all" button to see the results.  Good luck!