The backstay chainplate of the '84 Ericson 381 was cracked. Missed by surveyor, because when a boat's transom extends past the slip, it's impossible to see without a dinghy--and when hauled out, a ladder is required.
This hefty piece of stainless is 2" x 13" and almost half an inch thick. I believe the crack was caused by a very small deviation in the true pull of the backstay.
The ruler photo shows the relation of the crack to the lateral bend induced by subtle misalignment.
This piece may have gone another 30 years without incident, but nobody in his right mind could sleep knowing it was there.
The piece is easy to have fabricated--but what caused the crack?
My theory is that the factory installed it with no margin for error or to permit natural alignment.
The holes for the bolts were drilled such that the bolts cut threads in the fiberglass of the transom before entering a stainless backing plate, split washer and nut.
Removal required unscrewing. They couldn't be hammered out. They were threaded in.
This seems like extra strength but I think it's an error. Such tight holes fix in place a chainplate set by eye--how else would you do it?--that must align with a point 60 feet away of uncertain location (i.e., the top of the mast).
On reinstallation of the new chainplate, I plan to over-drill the transom holes slightly, so the plate can align naturally.
Counter arguments invited.
This hefty piece of stainless is 2" x 13" and almost half an inch thick. I believe the crack was caused by a very small deviation in the true pull of the backstay.
The ruler photo shows the relation of the crack to the lateral bend induced by subtle misalignment.
This piece may have gone another 30 years without incident, but nobody in his right mind could sleep knowing it was there.
The piece is easy to have fabricated--but what caused the crack?
My theory is that the factory installed it with no margin for error or to permit natural alignment.
The holes for the bolts were drilled such that the bolts cut threads in the fiberglass of the transom before entering a stainless backing plate, split washer and nut.
Removal required unscrewing. They couldn't be hammered out. They were threaded in.
This seems like extra strength but I think it's an error. Such tight holes fix in place a chainplate set by eye--how else would you do it?--that must align with a point 60 feet away of uncertain location (i.e., the top of the mast).
On reinstallation of the new chainplate, I plan to over-drill the transom holes slightly, so the plate can align naturally.
Counter arguments invited.
Last edited: