Balance, CE and CLR.....

Discussions on the characteristics of the EC12. Yes, it handles different than most R/C Sailboats

Moderators: Capt. Flak, bigfoot55, Chuck Luscomb

Balance, CE and CLR.....

Postby geeks2you » Wed Apr 14, 2010 9:20 pm

Sorry for the long post... this is driving me crazy.....

So I have talked to quite a few of you about the work I am doing on the overall helm balance of my boat and in reading the forums and helm balance posts all over the internet, I have come to a conclusion that I am totally missing something.

If you start with some basic calculations on CE and CLR (per posting here: http://www.myrc.org/Library/centeref.htm) it seems as though my boat should have a heavy lee helm. After marking my CLR (33 1/2" for those who care) on the boat and comparing it to the horizontal CE of the boat, my Horizontal CE is roughly 5 inches forward of my CLR measurements. The CE of the Main Sail alone is 1 inch in front of the CLR. The CE measurements were roughly taken with a perpendicular mast, with no rake, in my center mount hole (~25 1/4").

Moving the mast forward does seem to help the weather helm a little, but the math says that it should drive the helm to lee, which it should be lee helm already.

In talking to Gerry Cobley at Atlanta, we were trying to figure out if moving the jib boom up off the deck would effect the overall CE balance, but since moving the jib up moves the CE in a diagonal motion (up and toward the stern) it does not look mathematically like it would have an overall dramatic effect on the position of the sail plan CE position.

What am I missing here?

On a side note, make sure your Uppers are the same tension or looser than your lowers..... if not you can get "snap weather helm" when the wind gusts. In the event your lowers are lower in tension, the wind will drive the lateral mast bend to leeward in the mid-section of the mast, and hook the upper portion of the mast, causing an increase in drive and power to the main, throwing your boat up into the wind. I really just needed to say this somewhere so I don't forget. Thanks to Scott for pointing this one out.

Eric Olson
Atlanta Model Yacht Club
AtlMYC.org
geeks2you
 
Posts: 61
Joined: Sun Apr 19, 2009 1:37 pm

Postby greerdr » Wed Apr 14, 2010 11:07 pm

I submit that each of of these beautiful ladies have an intrinsic "soft spot".
I have built a few and trying to find that exact balance is very elusive. I'd suggest getting close to what feels right and get the boat on the pond.
The missed tack or mark is so much more important than a few inches of speed on any leg is huge.
Sail her-trust her-and come have some fun.
You have built in a TON of options with your jib,mast step,shrouds ,back-stay and vang;let the boat show what she wants!

R.C.Greer
greerdr
 
Posts: 670
Joined: Mon Sep 15, 2003 5:39 pm

Postby geeks2you » Thu Apr 15, 2010 12:57 am

Oh I sail her and enjoy every minute....

This is just the engineer in me trying to figure out how to make it go faster. I have begun sheeting out (what sometimes feels like too much) when a puff hits to try to keep the drive in the sails, but I know I can push it a little harder if I can get the helm balance closer.

Would camber position and twist drastically change the CE of the sail plan? Is there anything out there that can help to calculate the actual CE position other than the corner to mid-point measurement technique?

And I know this post is a little toward the nerdy side. Again, it is the engineer in me trying to just put some math to the feel of the boat.

Eric Olson
Atlanta Model Yacht Club
AtlMYC.org
geeks2you
 
Posts: 61
Joined: Sun Apr 19, 2009 1:37 pm

Postby greerdr » Thu Apr 15, 2010 9:11 pm

Have you read Bob Wells two books? They are a gold-mine of very well designed trials of exactly what you are asking.
Available on the site in the store,look for "optimising the EC-12"

R.C.Greer
greerdr
 
Posts: 670
Joined: Mon Sep 15, 2003 5:39 pm


Return to Sailing the EC12

Who is online

Users browsing this forum: No registered users and 1 guest

cron