diff --git a/Aircraft-yasim/j3cub.xml b/Aircraft-yasim/j3cub.xml
index 76bd4e162..9cac67b4a 100644
--- a/Aircraft-yasim/j3cub.xml
+++ b/Aircraft-yasim/j3cub.xml
@@ -71,7 +71,7 @@ since it is what the weight-and-balance site above uses.
 </wing>
 
 <!-- FIXME: taper (used the C172 value) -->
-<hstab x="-4.87" y="0.05" z="-0.42" taper="0.5"
+<hstab x="-4.87" y="0.05" z="-0.42" taper="0.5" effectiveness="1.24"
        length="1.49" chord="1.13" sweep="0">
   <stall aoa="16" width="4" peak="1.5"/>
   <flap0 start="0" end="1" lift="1.7" drag="1.2"/>
@@ -82,10 +82,10 @@ since it is what the weight-and-balance site above uses.
 
 <!-- FIXME: taper (used the C172 value) -->
 <!-- rudder has to be able to counteract aileron drag -->
-<vstab x="-4.87" y="0" z="-0.65" taper="0.38"
+<vstab x="-4.87" y="0" z="-0.65" taper="0.38" effectiveness="1.24"
        length="1.31" chord="1.37" sweep="0">
   <stall aoa="16" width="4" peak="1.5"/>
-  <flap0 start="0" end="1" lift="1.5" drag="1.2"/>
+  <flap0 start="0" end="1" lift="1.5" drag="1.2" effectiveness="1.5"/>
   <control-input axis="/controls/rudder" control="FLAP0" invert="true"/>
   <control-input axis="/controls/rudder-trim" control="FLAP0" invert="true"/>
   <control-output control="FLAP0" prop="/surface-positions/rudder-pos-norm"