• Creator
Topic
• #83150
Jacob Ernst
Participant

If I want to compare a 25ft boat with comfort ratio 30, with a 50tf boat with comfor ratio 30. I Would belive the 50ft to be more comfortable, but is there a way to do the math?

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• Author
Replies
• #83156

Hello jme, The the comfort ratio equation is: D ÷ (.65 x (.7 LWL + .3 LOA) x Beam↑1.33), where displacement is expressed in pounds, and length is expressed in feet.

This equation is designed as an indication of how quickly a boat will react to waves. There are not a lot of 50 footers with a CR as low as 30 and not a lot of 25 footers with a CR as high as 30, although both exist.

If you want, use refine search on Sailboatdata.com to find them. You can also try using the Compare tool on the site to see up to three boats at once. In Compare, use refine search to narrow your results, then Sort by LOA and finally select the boats to compare.

Hope this helps.

#83427
Jacob Ernst
Participant

Hi again

I`m sorry to bother You again, but I have to ask- Ex. a Falmouth cutter 22 with CR 33.83 vs Jeanneau 51 with CR 26.48, the Falmouth is in reel life, actually much better in rough seas than the more than 2x bigger Jeanneau? Not that I woulden`t believe it…
I just thought that there would be a `divide with ...% of the difference in ...` or something…

Best Regards
Jacob, Denmark

#83428

Hi Jacob, No bother at all. The CR is really meant to compare boats of similar type and size (we should be clearer on that and will update the definition on our website). We don’t believe there are many people who will go on an ocean cruise in a Falmouth Cutter 22. But, if speed of motion is important, with a CR of 33.83, the 22 would be a nice boat to sail on a choppy day.

#83429
Jacob Ernst
Participant

Ok, thank You!
And, You`ll never know- a Danish retired school teacher, circum navigated the globe twice, first in a Lynaes 18, and then in a Leasure 23. Both build for cruising a pond…
(Svend Billesboelle was his name)

#83430
Jacob Ernst
Participant

Sorry, there ia one last question…
I`m tryng to find the CR on a Parant 25 (not yet on Your list), and got stock in the formula above... I`m not sure what the `arrow-up` is. Is it like in power math?

#83458

Yes, that is correct. Beam to the 1.33 power.

#83471
Jacob Ernst
Participant

Hi

Thank You, once again!

And sorry that I keep getting back, but could You perhaps allso give me the formula for calculating the S.A./Disp, Bal./Disp, Disp./Len and Capsize S.F ?
(I’m still working on the Parant 25 data)

Best Regards-

Jacob

#83482

Here’s a good article which should help you some: https://www.sailmagazine.com/boats/comparing-design-ratios.
The CSF is the maximum beam divided by the cube root of the displacement in cubic feet; B/Displ ↑.333. The displacement in cubic feet can be found by dividing the displacement in pounds by 64.

#84520
Jacob Ernst
Participant

Hi again

Would it be possible to ‘bribe’ You, to help me to make the complete PARANT 25 data?
I’m not good at math, and I struggle with metric vs imperial!

I can mail You the numbers…

Best Regards

Jacob, Denmark

#84521

Sure. Please reach out to me at: contact@sailboatdata.com.

Bruce

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