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cutspar allows to create a notch top & bottom of two airfoils .dat files for spar caps. It makes sure that the features of the notches are synchronized in both .dat files so it can be correctly cut with a CNC hot-wire cutter.

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cutspar

Cutspar modifies a pair of .dat airfoil files to create the contoured notches required for applying spar caps on a wing panel foam core. The spar caps follow the curvature of the airfoil, that is, they're not necessarily flat pieces of precured carbon fiber. The software deals with synchronizing the features of the notches so it can be correctly cut on the CNC hot-wire cutter.

cutspar -I rootinput.dat -i tipinput.dat -O rootoutput.dat -o tipoutput.dat -C chord;efwd;eaft;ethk;ifwd;iaft;ithk -c chord;efwd;eaft;ethk;ifwd;iaft;ithk [-x] [-t roottwist;tiptwist[;pivotpoint] [-w wroot;wtip;wdia] [-m]

-I rootinput.dat : input airfoil file name at root of panel (airfoil .dat)

-i tipinput.dat : input airfoil file name at tip of panel (airfoil .dat)

-O rootoutput.dat : output airfoil file names for root

-o tipoutput.dat : output airfoil file names for tip

-x Exit and re-enter the leading edge. Allows the LE to cool down before cutting the other half of the airfoil.

-t roottwist;tiptwist[;pivotpoint] : Rotates the airfoil (washout) around a pivot point. Negative angle = LE down. pivotpoint is in percent from LE, and negative means to rotate at the intrados skin, positive at the extrados skin (default=-70).

-f : Add one point to close the airfoil

-d density : Densify the airfoil .dat such that there's a point every 'density' mm. In doubt, use -d 1.2 (default is to not densify)

-w wroot;wtip;wdia : Create a channel for the servo wires. wroot and wtip are distances from LE to center of channel. wdia is the channel diameter. This option works best with a channel positionned right behind the spar.

-m : Also create a pair of xxx-mold.dat files. These are the same as the root and tip files, but without the spar cut outs.\n");

-C specifications at root (see below for the mandatory 7 parameters)

-c specifications at tip

chord : chord of at this station (root or tip)

efwd : extrados spar forward edge

eaft : extrados spar aft edge

ethk : extrados spar thickness (notch depth)

ifwd : intrados spar forward edge

iaft : intrados spar aft edge

ithk : intrados spar thickness (notch depth)

efwd, eaft, ifwd and iaft are distances relative to the LE at their respective\nstation.

Example:

cutspar -I SynerJ-90.dat -i SynerJ-80.dat -C 221.5;31.62;81.62;2;32.62;82.62;2 -c 196.5;20.54;70.54;2;21.54;71.54;2 -O Mid2-root.dat -o Mid2-tip.dat -x -t -0.20;-0.35;-70 -f -d 1.2

The software will cope with spar of different widths, position or thickness at each panel ends, or even top & bottom, keeping the points in the .dat files correctly synchronized.

Using cutspar with GMFC

Using the .dat files created by cutspar on GMFC is a piece of cake. Just make sure to use the "complex" mode instead of the "wing" mode. This mode is preferred because in "wing" mode, GMFC makes some assumptions about the .dat file being stricly an airfoil, which is no longer true once cutspar creates creates notches on the surface.

However, using the "complex" mode has drawbacks : we loose very useful functions like the X-leading edge and points densification. Thankfully, cutspar supplements with similar functions.

To compile

Compiled on Windows 10 using Code::Blocks v17.12 http://www.codeblocks.org/ This POSIX compliant code should compile just as fine on Linux or Apple.

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cutspar allows to create a notch top & bottom of two airfoils .dat files for spar caps. It makes sure that the features of the notches are synchronized in both .dat files so it can be correctly cut with a CNC hot-wire cutter.

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