SailNet Community - View Single Post - Boat Buying By The Numbers
View Single Post
  #22  
Old 07-11-2013
JulieMor's Avatar
JulieMor JulieMor is offline
Senior Member
 
Join Date: Sep 2011
Posts: 853
Thanks: 47
Thanked 16 Times in 16 Posts
Rep Power: 4
JulieMor is on a distinguished road
Re: Boat Buying By The Numbers

Quote:
Originally Posted by ctl411 View Post
Your numbers look high on these, you may have the math wrong???
You're probably right.

When I built the spreadsheet, I compared the numbers the spreadsheet was generating (based on formulas taken from Brewer's primer) to the numbers GoSail was generating and they were right there. So I thought they were good. Yesterday my SO found a post on a naval architect's forum that had motion comfort calculated for about 500-600 boats. Their numbers were much lower than what GoSail or I had.

I rechecked the formulas.

I used CR=Displacement in pounds/.65 x (.7 LWL + .3 LOA) x B1.333.

The NA forum used MCR = Disp / (2/3*((7/10 * LWL)+(1/3 *LOA))*Beam4/3 )

They are almost identical except Brewer calls it Comfort Ratio (CR) and the NA called it Motion Comfort (MCR).

I'll recheck the math Excel is doing. Maybe GoSail did the same thing I did and that's why the similar numbers. But I'm deferring to the NA for his numbers being correct.

Update: I forgot a pair of parenthesis in the Excel formula.

Last edited by JulieMor; 07-11-2013 at 10:25 AM.
Reply With Quote Share with Facebook