Low Tide

Yacht Designer Tad Roberts' Web Log

Stability of Canadian OFSV

CBC has just published a story CoastGuard Ship Redesign, outlining the discovery of apparent instability in the initial design of our new OFSV’s (Offshore Fisheries Science Vessel), three of which Seapan has under contract and the first under construction.

This story seems like pot stirring coupled with the usual misinformation. These are large and immensely complex research vessels. A lot of people’s/departments requirements must be met, so the thing will evolve as time goes on. Research technology is changing as quickly as in other fields, the ship was designed 4-5 years ago now, and today we live in a different world. Ships remain useful as long as they can be adapted to current needs.

I really doubt the Robert Allan office would produce an unstable design, they’re not amateurs. Seaspan’s claim they had to increase length to improve stability makes little sense. Increasing the ship’s length will not change her transverse stability very much at all. Unless the extra length allowed other changes (lowering significant weights) that do improve stability. And extra length, even with the added displacement, will increase speed, not lower it. Likely the speed change is a contractual safeguard, don’t promise too much!

Ultimately this story is the reason there are multiple layers of design responsibility. It’s to catch the possible problems, in this case the system worked. I would expect that weights and stability will keep being updated as the ship’s are built.

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