Distort Tab

The Distortion tab is used to modify the currently selected SAC curve using either the 1-Cp or Lackenby methods.

Use the Distort tab

1. Select the relevant method via the Radio button, the parameter to alter and enter its new value.

   For 1-Cp only the CB may be varied, for Lackenby the CB, LCB, parallel mid body aft (PBA) or parallel mid body forward (PBF) may be varied. LCB, PBA and PBF are measured as a distance (in current units) from the AP.

   If Lackenby is selected, then several options are enabled which control how the Sectional Area Curve is altered.

   • Fix Perpendiculars ensures that the sectional areas aft the perpendiculars will not be changed.

   • Fix Overhangs ensures that the sectional areas aft of the AP and forward of the FP are not changed.

   • Iterate to tol allows Lackenby distortion to be applied multiple time in order to iterate to the target parameter within a given tolerance.

2. Click the Calc button to perform the variation on the current SAC.

3. To transpose (modify) the curves once the SAC curve has been altered, select the required curves from the pulldown list.

4. To store the modified curves select the Accept check box and click the Trans button.

   If the Pre-connect checkbox is selected, then any patch boundary networks will be "connected" before the transposition, so that surfaces can be rebuilt after the transposition. If the design contains surfaces generated in the Patch and Curve Editor (PACE), then it is recommended that All curves are transposed and the design Pre-connected. After the transposition it is necessary to rebuild the surface using PACE. This should normally only involve opening the surface in PACE (select the surface name in the Lines View tree, click the r.m.b. and select Modify) and clicking the rebuild button, (F7).

   Important: Pre-connecting requires that patch boundary curves be fitted to points. Any curve which has been faired by modifying the control points (adjusting vertices, autofairing, etc) could cause the regeneration of surfaces to fail.

When finished the SAC curve is accepted as normal.