[C320-list] Stability Index or Angle of Vanishing Stability

[Jack Brennan]

Hi Jeff:

A complicated question because these types of formulas are so general that they are only of limited usefulness.

However, there may be a way to tackle this. I’ve read repeatedly that the EU has given the Catalina 320 a CE certification of A, which is open ocean and the best you can get. I think rating the 320 as a long-distance cruiser is a bit of a stretch, but there you go.

The EU, which is renowned for creating blizzards of regulations, apparently has  a rating called a STIX to evaluate stability and seaworthiness in assigning these ratings. To get an A, you need at least a 32 and presumably a decent AVS in case you are knocked down.

A quick Internet search failed to uncover these EU regulations, but they must be out there somewhere. And, somewhere, there is a file with info on the 320 that earned it the A rating.

To inject some reality in this, the angle of vanishing stability is affected by all sorts of features – roller furling, davits, arches, solar panels, how much weight you’re carrying and where it is, whether you have the wing or full keel. It would be quite a project to get an accurate AVS.

The race sounds great. With the 320’s speed, you probably are looking at maybe five days. That should limit the risk from storms.

If I were you, I would spend some time reading the experts on storm tactics for light, beamy sailboats. Much of the traditional advice is for heavy, skinny boats. Following that advice got sailors of boats like ours in  the Fastnet and Hobart races in trouble.

Jack Brennan
Sonas, 1998 Catalina 320
Tierra Verde, Fl.







Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows

From: Jeff Smith<mailto:svsailmates512 at gmail.com>
Sent: Tuesday, December 13, 2022 2:19 PM
To: c320-list at lists.catalina320.com<mailto:c320-list at lists.catalina320.com>
Subject: [C320-list] Stability Index or Angle of Vanishing Stability

To all,

I am not sure if this will go through, as I no longer receive Association emails. If it does, though, I am interested to know if anyone has ever calculated a stability index (AVS) or had one calculated. I plan to enter Sailmates in the 2024 Newport - Bermuda race. However, the AVS must be at least 115 to qualify technically. I have found an equation and estimated some of the inputs, such as the “Draft of Canoe Body” and the “Total weight”. If anyone has a stability index, AVS, or good measurements for the draft of canoe body and total weight (which I assume is different than the stated displacement), either from Catalina or otherwise, please let me know. FYI - I have emailed Catalina but they currently do not have anything that is helpful, at least for the 1994. I asked about newer C320 boats but at the present time, they are unable to find anything.

Thanks in advance,
Jeff
#121, S/V Sailmates