Merge pull request #492 from teyrana/fix_387_offaxis_cp

[fixes #387] Fixes one source of off-axis CP error
openrocket · Dec 8, 2018 · 5e3d801 · 5e3d801
2 parents 4bd3e4f + 51418e3
commit 5e3d801
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Showing 2 changed files with 12 additions and 6 deletions.
diff --git a/core/src/net/sf/openrocket/aerodynamics/BarrowmanCalculator.java b/core/src/net/sf/openrocket/aerodynamics/BarrowmanCalculator.java
@@ -202,15 +202,20 @@ private AerodynamicForces calculateAssemblyNonAxialForces(  final RocketComponen
 			AerodynamicForces componentForces = new AerodynamicForces().zero();
 			calcObj.calculateNonaxialForces(conditions, componentForces, warnings);
 
-			Coordinate x_cp_comp = componentForces.getCP();
-			Coordinate x_cp_weighted = x_cp_comp.setWeight(x_cp_comp.weight);
-			Coordinate x_cp_absolute = component.toAbsolute(x_cp_weighted)[0];
-			componentForces.setCP(x_cp_absolute);
+			Coordinate cp_comp = componentForces.getCP();
+
+			Coordinate cp_weighted = cp_comp.setWeight(cp_comp.weight);
+			Coordinate cp_absolute = component.toAbsolute(cp_weighted)[0];
+			if(1 < component.getInstanceCount()) {
+				cp_absolute = cp_absolute.setY(0.);
+			}
+
+			componentForces.setCP(cp_absolute);
 			double CN_instanced = componentForces.getCN();
 			componentForces.setCm(CN_instanced * componentForces.getCP().x / conditions.getRefLength());
 
-//			if( 0.0001 < Math.abs(0 - componentForces.getCNa())){
-//				System.err.println(String.format("%s....Component.CNa: %g   @ CPx: %g", indent, componentForces.getCNa(), componentForces.getCP().x));
+//			if( 0.0001 < Math.abs(componentForces.getCNa())){
+//				System.err.println(String.format("%s....Component.CNa: %g   @ CP: %g, %g", indent, componentForces.getCNa(), componentForces.getCP().x, componentForces.getCP().y));
 //			}
 
 			assemblyForces.merge(componentForces);

diff --git a/core/test/net/sf/openrocket/aerodynamics/BarrowmanCalculatorTest.java b/core/test/net/sf/openrocket/aerodynamics/BarrowmanCalculatorTest.java
@@ -86,6 +86,7 @@ public void testCPSimpleDry() {
 
 		assertEquals(" Estes Alpha III CNa value is incorrect:", exp_cna, cp_calc.weight, EPSILON);
 		assertEquals(" Estes Alpha III cp x value is incorrect:", exp_cpx, cp_calc.x, EPSILON);
+		assertEquals(" Estes Alpha III cp x value is incorrect:", 0.0, cp_calc.y, EPSILON);
 	}
 
 	@Test