The Physics of Railmeat - Page 2 - SailNet Community
Reply
 
LinkBack Thread Tools
post #11 of 51 Old 12-16-2010 Thread Starter
Last Man Standing
 
smackdaddy's Avatar
 
Join Date: Aug 2008
Posts: 14,566
Thanks: 153
Thanked 149 Times in 142 Posts
Rep Power: 10
     
Okay, but....next stupid question...this technique essentially means you're counteracting the forces on the sails...correct? Couldn't you gain that same advantage (flattening the boat) with trim?

I can definitely see the need on smaller boats...but it just seems like a miniscule counteraction force on a big boat.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

S/V Dawn Treader - 1989 Hunter Legend 40
smackdaddy is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #12 of 51 Old 12-16-2010
NON member
 
AE28's Avatar
 
Join Date: Jun 2008
Posts: 546
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
 
smack...
Bump your Rep Power and give you another little green box and you go techie on us???
AE28 is offline  
Quote Quick Reply Share with Facebook
post #13 of 51 Old 12-16-2010
Special Delivery
 
speciald's Avatar
 
Join Date: Mar 2007
Location: live on boat
Posts: 661
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 9
 
Send a message via Skype™ to speciald
I guess it depends on the boat. My current boat's keel weighs more than my C&C 37+ did. The boat doesn't move reguarless of where the crew sit. I went out to watch the boats in the St. Barth's Bucket race last year (must be 100+ feet to enter) and those megayachts had crew on the rail - maybe because it made for better photos.
speciald is offline  
Quote Quick Reply Share with Facebook
post #14 of 51 Old 12-16-2010 Thread Starter
Last Man Standing
 
smackdaddy's Avatar
 
Join Date: Aug 2008
Posts: 14,566
Thanks: 153
Thanked 149 Times in 142 Posts
Rep Power: 10
     
I'm just trying to get AdamLein to throw down some equations! That dude has the mathematical goods.

I'm convinced there's more to the story here - and I think speciald is right that it's more about the photo than the physics.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

S/V Dawn Treader - 1989 Hunter Legend 40
smackdaddy is offline  
Quote Quick Reply Share with Facebook
post #15 of 51 Old 12-16-2010
Senior Member
 
AdamLein's Avatar
 
Join Date: Nov 2007
Location: SF Bay area
Posts: 1,923
Thanks: 6
Thanked 6 Times in 5 Posts
Rep Power: 8
 
Later, smack, I'm at work right now and I can only get so distracted by sailing before I feel like I'm not doing right by my company

s/v Laelia - 1978 Pearson 365 ketch
s/v Essorant - 1972 Catalina 27
AdamLein is offline  
Quote Quick Reply Share with Facebook
post #16 of 51 Old 12-16-2010
Senior Member
 
pdqaltair's Avatar
 
Join Date: Nov 2008
Location: Deale, MD
Posts: 2,600
Thanks: 1
Thanked 53 Times in 53 Posts
Rep Power: 7
 
Ofcourse, meat resting on a windward bunk would do the same with less windage.

And of course, this is minor compared to small boats. On my first cat we carried two on the trapeeze, on hiking racks. The "rail meat" represented almost 80% of the righting moment. Failure of the rail meat to offset the forces involved were fun.

(when asked how he reached the starting holds on a difficult rock climbing problem that clearly favored taller climbers - he was perhaps 5'5")

"Well, I just climb up to them."

by Joe Brown, English rock climber




To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
pdqaltair is offline  
Quote Quick Reply Share with Facebook
post #17 of 51 Old 12-16-2010
Senior Member
 
jackdale's Avatar
 
Join Date: Dec 2008
Location: Calgary, AB, Canada
Posts: 9,041
Thanks: 27
Thanked 59 Times in 56 Posts
Rep Power: 7
 
Quote:
Originally Posted by smackdaddy View Post
Okay, but....next stupid question...this technique essentially means you're counteracting the forces on the sails...correct? Couldn't you gain that same advantage (flattening the boat) with trim?

I can definitely see the need on smaller boats...but it just seems like a miniscule counteraction force on a big boat.


Weather helm is also a function of heel angle. Flattening the boat with railmeat to the optimum heel angle will reduce weather helm when going to weather, without reducing sail area.

When racers do reduce sail area they generally reduce the foresail first rather than reefing the main. That also reduces heel angle and weather helm.

Downwind the boat should be flat.

__________________
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
jackdale is offline  
Quote Quick Reply Share with Facebook
post #18 of 51 Old 12-16-2010
Senior Member
 
Join Date: May 2002
Posts: 2,723
Thanks: 6
Thanked 32 Times in 30 Posts
Rep Power: 14
 
Quote:
Originally Posted by smackdaddy View Post
Okay, but....next stupid question...this technique essentially means you're counteracting the forces on the sails...correct? Couldn't you gain that same advantage (flattening the boat) with trim?

I can definitely see the need on smaller boats...but it just seems like a miniscule counteraction force on a big boat.
You can reduce heeling by trimming the sails, or by reducing sail area, but both of those methods reduces the amount of power being generated by the sails. The racer's preference is to keep the sails as powerful as possible, while maximizing the efficiency of the hull and keel. When you use rail meat to flatten the boat, you're improving the efficiency of the hull shape without reducing the power of the sails.

Rail meat accomplishes the same purpose on big boats as on smaller boats. It just takes more bodies on bigger boats. If the boat is heeling excessively when I'm racing, I'll put as many people on the rail as are available, even though they might not be enough. Every little bit helps.

If you have flattened the sails as much as possible, and put all your crew on the rail, and the boat is still heeling too much, then you have to start thinking about reducing sail area.
Sailormon6 is online now  
Quote Quick Reply Share with Facebook
post #19 of 51 Old 12-16-2010
Senior Member
 
Sabreman's Avatar
 
Join Date: Sep 2006
Location: Yeocomico River, VA
Posts: 1,643
Thanks: 3
Thanked 18 Times in 15 Posts
Rep Power: 10
   
No offense to anyone, but all the answers are speculative and not quantitative. Sitting on the rail is really doesn't give you much advantage on a large vessel BUT where else should people be? On a properly run boat, people should not be all over the place.... just like on a football field, or basketball court. People have positions and should be there unless they need to be somewhere else. Since the weight has the potential to help, crew and gear should be positioned to keep the boat as flat as possible, if that is how the boat sails best. Like all the other answers, this is speculation without empirical evidence which I'd be really interested in seeing.

On small boats, I see the advantage to keeping the boat heeled in light air - to keep the boom in one place and to keep it from flopping back and forth. Ignoring the mechanics of keeping the boom in place, without exception, everyone that I've asked has not had an answer why the boat should be heeled. It makes no sense, less sail area is exposed to the wind when it's needed most. I'd really like to see a real answer to this since it's puzzled me for years.

On the same note, I question the radical elimination of gear to save weight. I once had crew get on me for carrying 20 gallons of water on an overnight race. One gal of water weighs 8.3 lbs. Then I looked at the guts on my crew......... Hmmmmmmm

Sabre 38 "Victoria"
Sabreman is offline  
Quote Quick Reply Share with Facebook
post #20 of 51 Old 12-16-2010
Senior Member
 
JKCatalina310's Avatar
 
Join Date: Nov 2010
Location: Randolph, MA
Posts: 164
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 5
 
There are other ways to flatten the boat then the use of rail meat. One of our friends at the marina has a real sweat racing boat. It's a 30' open with running back stays, full roach main and little to no comforts (doesn't even carry a cooler big enough for more then a six pack). But the boat moves, one day we were making 5.5-6 knots in 7-8 knots of breeze. Just don't take it out in over 12 knots of breeze with out 3-4 people that know what they are doing.

That boat has built in ballast tanks on the under side of the rails that can be filled for short handed sailing. There is a valve system that, with a pull of a line, will gravity dump the water from one tank to the other. It is tricky though. You have to be very quick and precise with tacking or you could knock yourself down and put the rail in the water.

Real fun to sail on that boat for an afternoon, but I'll take our cruiser for the long haul.

“Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.” -Mark Twain
JKCatalina310 is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Minimlist sail physics sccid General Discussion (sailing related) 4 10-25-2009 01:30 PM
Mast and rigging physics question DjY887 General Discussion (sailing related) 1 06-29-2009 01:37 PM
Physics of the random overhand sneuman General Discussion (sailing related) 6 03-12-2005 02:20 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome