At first,   two runners were designed arcoss a 2.4 meters' sprue; this keel product lateral bending over 3 millimeters result from liquid iron's cooling velocity.

Additionally, the stress which come from several runners between two keels made this bending more unpredictable.

Then, we remove all small runners; only two sprues left for each keel casting(see picture), casting temperature was arised. Finally keel casting lateral bending problem was sloved.