Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 03-03-2013, 13:56   #16
Senior Cruiser
44'cruisingcat's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 6,176
Images: 69
Re: Optimum Dagger Board Use

Originally Posted by MidLandOne View Post
Regarding using one board or two I am just throwing this in the pot from a consideration of the foils point of view - there may be other things going on.

The drag from a foil increases as the square of the lift from the foil so one is (remember, just considering the foils) often better off to spread the lift over two foils rather than just one. That is two foils giving the same lift as one have half the drag, all else being equal.

Hence, for mono hulls, why it is good to spread the lift between a spade rudder and the fin keel, and is a reason why there have been a lot of goes at trying multiple foils under monos eg as has been tried on IACC boats. That last is an example of other things going on because other performance advantages (eg manoeuvrability) have been lost that out weigh any decrease in drag. Monos generally (not always) have the disadvantage that the foils are in line so to give the full advantage they have to be far enough apart for the foils to be outside of the turbulence of the forwards ones (not possible), a disadvantage cats do not have with their dagger boards.

So, just with that limited view I would have thought that in the case that one fully dropped dagger board gave the lift needed then one is better off to use the two boards only part dropped enough to give the same total lift but much less drag.

I wonder if anyone can comment as to how much that fits real life and what else might be going on?
Roger Shuttleworth has done tank testing, and has found one larger board to be superior to two smaller ones.

You can get the same lift, with just over half the drag.

For racing boats, which will fly a hull regularly, you obviously need two boards.

44'cruisingcat is offline   Reply With Quote

dagger boards

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not 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 Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Fender board fender for a 2X6 board wadanoli Anchoring & Mooring 8 25-10-2015 10:14
Dagger Boards --- I don't quite get it Limpet Multihull Sailboats 55 04-03-2013 18:12
dagger rudders tallboy Multihull Sailboats 4 27-11-2008 09:53
Dagger board dilemma West Coast Cat Multihull Sailboats 8 07-03-2008 13:51
New to the board Islandmike Meets & Greets 2 06-03-2005 15:50

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 23:28.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.