diff --git a/core/src/net/sf/openrocket/masscalc/MassCalculator.java b/core/src/net/sf/openrocket/masscalc/MassCalculator.java
index a27561c90..44e726fcb 100644
--- a/core/src/net/sf/openrocket/masscalc/MassCalculator.java
+++ b/core/src/net/sf/openrocket/masscalc/MassCalculator.java
@@ -318,10 +318,13 @@ public class MassCalculator implements Monitorable {
 			
 			childrenData  = childrenData.add( childData );
 		}
-		assemblyData = assemblyData.add( childrenData);
+		
+
 		
 		// if instanced, adjust children's data too. 
-		if ( 1 < component.getInstanceCount() ){
+		if( 1 == component.getInstanceCount() ){
+			assemblyData = assemblyData.add( childrenData );
+		}else if( 0 < component.getChildCount()){
 			final double curIxx = childrenData.getIxx(); // MOI about x-axis
 			final double curIyy = childrenData.getIyy(); // MOI about y axis
 			final double curIzz = childrenData.getIzz(); // MOI about z axis
@@ -337,8 +340,8 @@ public class MassCalculator implements Monitorable {
 				//    and add to the total
 				instAccumData = instAccumData.add( instanceData);
 			}
-			
-			assemblyData = instAccumData;
+
+			assemblyData = assemblyData.add( instAccumData );
 		}
 		
 		
diff --git a/core/src/net/sf/openrocket/rocketcomponent/Clusterable.java b/core/src/net/sf/openrocket/rocketcomponent/Clusterable.java
index 86ec92622..8051fc13e 100644
--- a/core/src/net/sf/openrocket/rocketcomponent/Clusterable.java
+++ b/core/src/net/sf/openrocket/rocketcomponent/Clusterable.java
@@ -4,6 +4,10 @@ import net.sf.openrocket.util.ChangeSource;
 
 public interface Clusterable extends ChangeSource, Instanceable {
 
+	@Deprecated
+	// redundant with Instanceable#getInstanceCount()
+	public int getClusterCount();
+	
 	public ClusterConfiguration getClusterConfiguration();
 	
 	public void setClusterConfiguration(ClusterConfiguration cluster);
diff --git a/core/src/net/sf/openrocket/rocketcomponent/RingComponent.java b/core/src/net/sf/openrocket/rocketcomponent/RingComponent.java
index f91811aa8..bbf6b08ad 100644
--- a/core/src/net/sf/openrocket/rocketcomponent/RingComponent.java
+++ b/core/src/net/sf/openrocket/rocketcomponent/RingComponent.java
@@ -162,16 +162,6 @@ public abstract class RingComponent extends StructuralComponent implements Coaxi
 		fireComponentChangeEvent(ComponentChangeEvent.MASS_CHANGE);
 	}
 	
-	
-	/**
-	 * Return the number of times the component is multiplied.
-	 */
-	public int getClusterCount() {
-		if (this instanceof Clusterable)
-			return ((Clusterable) this).getClusterConfiguration().getClusterCount();
-		return 1;
-	}
-
 	@Override
 	public Collection<Coordinate> getComponentBounds() {
 		List<Coordinate> bounds = new ArrayList<Coordinate>();
@@ -180,17 +170,29 @@ public abstract class RingComponent extends StructuralComponent implements Coaxi
 		return bounds;
 	}
 	
-	
-
 	@Override
 	public Coordinate getComponentCG() {
-		return new Coordinate(length / 2, 0, 0, getComponentMass());
+		Coordinate cg = Coordinate.ZERO;
+		int instanceCount = getInstanceCount();
+		double instanceMass = ringMass(getOuterRadius(), getInnerRadius(), getLength(),
+				getMaterial().getDensity());
+
+		if (1 == instanceCount ) {
+			cg = new Coordinate( length/2, 0, 0, instanceMass );
+		}else{
+			Coordinate offsets[] = getInstanceOffsets();
+			for( Coordinate c : offsets) {
+				cg = cg.average(c);
+			}
+			cg.add( length/2, 0, 0);
+		}
+		return cg;
 	}
 	
 	@Override
 	public double getComponentMass() {
 		return ringMass(getOuterRadius(), getInnerRadius(), getLength(),
-				getMaterial().getDensity()) * getClusterCount();
+				getMaterial().getDensity()) * getInstanceCount();
 	}