diff --git a/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeCalc.java b/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeCalc.java
index 60117d808..a4cbc5d78 100644
--- a/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeCalc.java
+++ b/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeCalc.java
@@ -10,7 +10,9 @@ public abstract class TubeCalc extends RocketComponentCalc {
 
 	private final double diameter;
 	private final double length;
-	protected double refArea;
+	protected final double innerArea;
+	private final double totalArea;
+	private final double frontalArea;
 	
 	public TubeCalc(RocketComponent component) {
 		super(component);
@@ -19,27 +21,37 @@ public abstract class TubeCalc extends RocketComponentCalc {
 		
 		length = tube.getLength();
 		diameter = 2 * tube.getInnerRadius();
-		refArea = Math.PI * MathUtil.pow2(tube.getInnerRadius());
+		innerArea = Math.PI * MathUtil.pow2(tube.getInnerRadius());
+		totalArea = Math.PI * MathUtil.pow2(tube.getOuterRadius());
+		frontalArea = totalArea - innerArea;
 	}
 
 	@Override
 	public double calculatePressureCD(FlightConditions conditions,
 			double stagnationCD, double baseCD, WarningSet warnings) {
 
-		// calculation of pressure drop through pipe from "Atlas Copco Air Compendium", 1975,
-		// quoted as equation 14 in Carello, Ivanov, and Mazza, "Pressure drop in pipe
-		// lines for compressed air: comparison between experimental and theoretical analysis",
-		// Transactions on Engineering Sciences vol 18, ISSN 1743-35331998, 1998.
-
-		// Volume flow rate
-		final double Q = conditions.getVelocity() * refArea;
-
-		// pressure drop
-		final double deltap = 1.6 * Math.pow(Q, 1.85) * length /
-			(Math.pow(diameter, 5) * conditions.getAtmosphericConditions().getPressure());
+		// Need to check for tube inner area 0 in case of rockets using launch lugs with
+		// an inner radius of 0 to emulate rail buttons (or just weird rockets, of course)
+		final double deltap;
+		if (innerArea > MathUtil.EPSILON) {
+			// calculation of pressure drop through pipe from "Atlas Copco Air Compendium",
+			// 1975, quoted as equation 14 in Carello, Ivanov, and Mazza, "Pressure drop
+			// in pipe lines for compressed air: comparison between experimental and
+			// theoretical analysis", Transactions on Engineering Sciences vol 18,
+			// ISSN 1743-35331998, 1998.
 
+			// Volume flow rate
+			final double Q = conditions.getVelocity() * innerArea;
+			
+			// pressure drop
+			deltap = 1.6 * Math.pow(Q, 1.85) * length /
+				(Math.pow(diameter, 5) * conditions.getAtmosphericConditions().getPressure());
+		} else {
+			deltap = 0.0;
+		}
+		
 		// convert to CD and return
-		return deltap * refArea / conditions.getRefArea();
+		return (deltap * innerArea + stagnationCD * frontalArea) / conditions.getRefArea();
 	}
 
 }
diff --git a/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java b/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java
index b4e9524f1..3b0c50624 100644
--- a/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java
+++ b/core/src/net/sf/openrocket/aerodynamics/barrowman/TubeFinSetCalc.java
@@ -114,15 +114,15 @@ public class TubeFinSetCalc extends TubeCalc {
 		// area of disk passing through tube fin centers
 		final double tubeDiskArea = Math.PI * MathUtil.pow2(bodyRadius + tubes.getOuterRadius());
 
-		// half of combined area of tube fin interiors.  
-		final double tubeInnerArea = tubes.getFinCount() * Math.PI * MathUtil.pow2(tubes.getInnerRadius()) / 2.0;
+		// half of combined area of tube fin exteriors.  Deliberately using the outer radius here since we
+		// calculate pressure drag from the tube walls in TubeCalc
+		final double tubeOuterArea = tubes.getFinCount() * Math.PI * MathUtil.pow2(tubes.getOuterRadius()) / 2.0;
 
 		// body tube area
 		final double bodyTubeArea = Math.PI * MathUtil.pow2(bodyRadius);
 
 		// area of an interstice
-		intersticeArea = (tubeDiskArea - tubeInnerArea - bodyTubeArea) / tubes.getFinCount();
-		log.debug("interstice area " + intersticeArea);
+		intersticeArea = (tubeDiskArea - tubeOuterArea - bodyTubeArea) / tubes.getFinCount();
 		
 		thickness = fin.getThickness();
 		finCount = 3 * fin.getFinCount();