Hi Nick,

the head is actualy a fairly common place for moulded blades to fail from what I have seen. Cracking in the head has happened on some rudders from a few different builders on Mossies and Taipans that I have seen and heard of for many years. With both the older style rectangular rudders in alloy boxes and the newer shapes in carbon boxes and now alloy ones also.

My only guess is the way they are put together in the head, as splitting on the join is usualy the first sign. The ones I have seen appear to just be bogged together with no flange, so the glass just butt joins.