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Old 04-03-2017, 10:12 AM
Pammie Pammie is offline
Join Date: Dec 2015
Rep: 10 Posts: 4
Location: Eindhoven, Netherlands
F28 cat pitchpole resistance

I designed a F28 cat and would like to hear your opinions about it.

It should be able to comply with ISO12217 stability cat A. Base is a Nacra Infusion like design as these are known for resistance to pitchpoling. I scaled it to 8,5 meter (length and width). Width is then 0,77 m. Height was extended to 1 meter height above waterline. Further I decreased rocker line as Nacra is ideally sailed on one hull and a ocean racing cat is not. (BcB = 4,8 m)

Stability calculations showed it was about 20% short of minimum requirements (which is cat B). Therefore I extended the hull width to 1 meter with special attention to the waterline width (about 0,7 m). Wetted area is 5,8 m2.
This was just enough to match cat A pitchpole stability.

But... I'm not quite happy with the hullform. Semicirculair line is quite some distance above waterline, and wetted area could be smaller (4,7 m2 for semicirculaire tube with pointy ends?) Further decrease rockerline? (at what cost?)

Some hints would be appreciated.
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F28 cat pitchpole resistance-f28vs4.3.jpg  F28 cat pitchpole resistance-f28vs4.31.jpg  F28 cat pitchpole resistance-f28vs4.32.jpg  

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