Was AVS a journalists passing fancy? (Are you there JJ?)

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Re: AVS - a few bits of interesting info

Part of the 1979 Fastnet Enquiry dealing with stability can be found here: http://www.co32.org/BOAT_SECTION/STORIES/FASTNET_STUFF/fastnet.htm

The Half Tonner (not sure, but I seem to remember that it was based on Grimalkin, on which their were a number of fatalities?) whose stability characteristics were so criticised by the Wolfson Report had an AVS of 117 degrees.

Here is its stability curve alongside the Contessa one: http://www.co32.org/BOAT_SECTION/STORIES/FASTNET_STUFF/intact.htm
 

AngusMcDoon

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>Of course, B&Q has an AVS of less than 90 deg...

Not necessarily so, because...

Trimaran floats have a buoyancy much greater than the boat's total displacement, usually about 180%. This means that at the point of capsize a tri is floating entirely on one float.

The main hull has the large majority of the boat's weight.

Masts are usually carbon fibre on modern tris, so light.

And the main reason, the beams are not in line instead making a shallow V.

So at 90 degrees the main hull is sticking out to one side of the current centre of buoyancy. Modern tri designs have an AVS slightly greater than 90 degrees, not far below that of the Catalina in question.
 

jamesjermain

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Re: No!

Hi! Nicho, and all.

I'll come clean and say, the GZ curve arrived from America very late - after I had written the article. I passed it straight on to the office and didn't spot how low the AVS was. Had I done so I would cerainly have mentioned it because it calls into question the boat's category A classification.

There is also a clash between this low AVS and a compaatively high STIX number which implies that she is stable, and resistant to capsize.

I currently have a call waiting to the designer asking for an explanation and will report on same when I hear back.

In the meantime, thanks for pointing this out.
 

jamesjermain

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Update

Subject to further investigation, it apears we were sent the wrong GZ curve. How or why this happened I don't know. AVS according to the designer is 114.3. Now I have to say that, while better, it is not particularly good. I am waiting for a copy of the correct GZ curve before saying more
 
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Re: Update

Does anyone know to what extent it is possible to vary the AVS by "creative accounting" techniques. I ask because I have seen widely varying AVS's quoted for the same class of boats in different contexts.

For example, are there any standards as to what kind of equipment the boat must have on board in calculating the test? Must it have for example, the boom attached? Any sails? Weight of rigging? etc. etc.

My guess is that manufacturers tend to go for the most optimistic possible manner of calculating the AVS, with a view to marketing, but are there any limits as to how far they can go?
 

ColdFusion

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Whether it's 105 or 114 degrees it's still completely unsuitable for crossing oceans, which is what the review in YM seemed to imply. Boat reviews are often a (significant?) factor in the purchasing decision so I don't think I'm being too harsh by saying it's downright irresponsible of YM (or any other publication for that matter) to publish such a misleading review.
 
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