Sailboat Ratios

[barnakiel]

Sailboatdata


website gives some of the ratios, for the listed hulls. Their database is very ample.


https://sailboatdata.com/



Cheers,

barnakiel

[Jeff H]

Originally Posted by Don C L

I too find that amazing. Know of any videos and/or GZ curves for those boats offhand? Is this due to the deep keels with bulbs making them so unstable when inverted?

There used to be a great video that explained some of this but I do not see it on Youtube.

It really is a mix of things:
-They are very deep draft with bulbs at the end of the keel.
- They often have moveable ballast which pulls them off dead center
helping them right.
- They have pretty high cabin structures and freeboard intended to destablize them in the inverted position
-They have extremely lightweight carbon fiver rigs, sometimes (maybe most times) with sealed chambers in them.
-under Open Class rules they literally have to invert the full size boat and have it right itself.

There used to be a great video that explained some of this but I do not see it on Youtube. Here are a couple videos:

https://www.youtube.com/watch?v=tJ8dHP9NhFI

https://www.youtube.com/watch?v=53BN1CwedwY

http://www.thedailysail.com/offshore...ion-test-video

The IMOCA 60's are tested without their rigs since the rigs often contain flotation intended chambers to prevent full inversion so righting without the rig is a worst case.

I have not seen a graph of this, but have had discussion with people who design these boats and the Volvo 65's about this issue.

Jeff

Originally Posted by barnakiel

Sailboatdata
website gives some of the ratios, for the listed hulls. Their database is very ample.
Cheers,
barnakiel

SailboatData is a wonderful resource, and does include some of the data to evaluate the sailing characteristics such as Bal/D, SA/D and D/L. But there are no simple ratios or indexes that provide useful information about stability or motion comfort. The CE standards include a module on STIX which is a complex set of formulas that evaluate the overall stability and likelihood of down flooding. Those numbers are sometimes published for new boats in European magazines but are rarely available to us mere mortals or for older designs.

Jeff

[GordMay]

"OceanPlanet" inversion test

https://www.youtube.com/watch?v=LZcwoQoNVak

"Gust Buster" - 180° inversion test on a Class 40

https://www.youtube.com/watch?v=4gC1lPI_lJk

[Don C L]

yeah I see the bulb does the trick, but now I want to see it done with the mast up, a jib and reefed main up. One thing I noticed in those videos is that sinking the bow would help it spin faster. If they had a bow compartment they could flood, I bet that would help too. (This is a phenomenon easily observed in whitewater or surf kayaking.)