This thread is privately moderated by DanL, who may elect to delete unwanted replies.
May 12, 2009, 02:45 PM
Registered User
United States, MN, Brainerd
Joined Oct 2004
2,535 Posts
Servo Operated Steering Gear/Tiller

The rudder can be operated prototypically with a servo operating the tackle on the tiller.
The approach used on the SC&H brig Syren is shown below.
The deck block on each side is attached to a fairlead, minimizing the likelihood of any significant water infiltration.
A 4-inch piece of bungee cord is used on each side of the servo arm to act as a shock absorber and to control operating line tension.
The diagram shows the ship's wheel being operated with the tiller and rudder. The Syren wheel is not rigged to rotate.
When transporting, I unhook the tiller blocks from the eyes and hook them to elastic loops on the tiller for extra protection if the rudder gets bumped during handling.

# Images

View all Images in thread
 May 12, 2009, 04:02 PM SCALE Sailor United States, MD, Severna Park Joined Apr 2008 1,996 Posts Winch Drum Size Formula To determine what size drum your winch needs to pull a specific amount of length, such as for braces, use the formula below: L = Length of Pull required R = number of winch revolutions x 3.14 D = Drum Diameter D = L/R Examples: Need to pull 12" with a winch that makes 3.5 revolutions (1260°) D = 12 / (3.5 x 3.14 = 10.99) D = 1.1" Need to pull 2" with a winch that makes .5 revolutions (180°) D = 2 / (.5 x 3.14 = 1.57) D = 1.27"
 May 12, 2009, 06:34 PM Registered User United States, MN, Brainerd Joined Oct 2004 2,535 Posts winch drum pull, brace travel The preceding formula does accuarately give the brace pull length for a drum. Where the fun begins is determining how much pull you need. Line stretch, mechanical tolerances, angle of pull through complete travel (includes the complexity of both the horizontal and vertical angle components of the brace path), geometry changes under wind load, etc. are variables that determine brace pull required. And if one servo pulls more than one yard, the two (or more) different drum diameters on one compound drum need to be carefully determined given that each yard has a different length, differnt angles in the brace paths (and different angles again if yards are moved for reefed or furled sails.) Having a +/-4-turn winch servo and a programmable Tx (like a Spektrum) really help zero in on tuning the braces in the finished rig and under sailing conditions. I sized my drums for 20% more pull distance than I actually measured. I also left all the braces long and adjusted and trimmed them back as the rig settled in and the adjustments fine-tuned. Last edited by DanL; May 20, 2009 at 10:54 AM.
May 20, 2009, 10:41 AM
Registered User
United States, MN, Brainerd
Joined Oct 2004
2,535 Posts
Bilge Pump

I'm adding a water sensor and bilge pump after seeing the Syren get knocked down on two outings this year.
Here's a great bilge pump circuit:
http://www.mhsd.org/model/autopump.htm
Very cheap, reliable, compact. Pic shows how it looks in my tug. The whole circuit is in the wire bundle hot-glued to the coaming, arranged so the TIP120 can plug in to three connectors. The "pull-tab" is used to pull the TIP 120 to deactivate the pump when needed. The pump is from table-top fountain and puts out a lot of water - much more tha a windshield washer pump I think. It's also configured for bottom pickup unlike a washer pump that needs to be primed.
Any relatively large hull that can be knocked down in gusts probably should have a pump to at least allow some recovery time.

# Images

View all Images in thread
May 21, 2009, 09:47 PM
Registered User
United States, MN, Brainerd
Joined Oct 2004
2,535 Posts
Scale bowsie block

Sail sheets, halyards, etc. on a working R/C sailing model may need to be adjustable. A "bowsie-block" can be made that looks like a scale block but allows instant adjustment of line length.
The block is easy to thread if the line is inserted from the top of the block and then pushed thru the side hole with a thin rod or tool.
The 90 degree bends in the line path thru the block hold the line to the adjusted length.
Pics show details.

# Images

View all Images in thread
Last edited by DanL; May 22, 2009 at 06:31 AM.
Jun 05, 2009, 02:29 PM
SCALE Sailor
United States, MD, Severna Park
Joined Apr 2008
1,996 Posts
Modeling Calculators

Here's an MS Excel Spreadsheet that contains useful calculators for various boat modeling items, including:

Scale Standing & Running Rigging Sizes based on mast diameter; A scale to real conversion chart; the drum size calculator offered in a previous post; and a sail area calculator.

Some of these I found in various places, and some were added myself, and more will be added as I learn of them.

Download: Handy Boat Modeling Calculators & Conversions

# Images

View all Images in thread
 Jun 05, 2009, 09:57 PM Registered User Southern Calif Joined Dec 2005 2,294 Posts Thanks Jerry The spread sheet calculator will come in handy when I start the build on the Gertrude L Thebaud fishing schooner. I have been following your build with great interest. Ed
Jun 06, 2009, 12:50 AM
SCALE Sailor
United States, MD, Severna Park
Joined Apr 2008
1,996 Posts
Center of Effort of Sails

To find the Center of Effort (CE) of a triangle: Draw lines from the points of the triangle to the center of the opposite side (see attached image). Where the lines cross is the CE of the triangle.

To find the CE of a gaff headed sail, divide it into two triangles and find the CE of each triangle. Connect the two CEs with a line - the sail's CE is on that line.

Where on the line is determined with this: L1=L*A2/(A1+A2) where A1 & A2 are the areas of each triangle, L is the length of the line between their CEs. The result is the distance of the sail's CE from one of the others. It will be closer to the larger triangle on the line.

Here's Constellation's driver for an example:
b=19.5" h1=4.75" h2=12.5, L=5.833"
4.75*.5*19.5=46.313 (a1)
12.5*.5*19.5=121.875 (a2)
L1=5.833*121.875/(a1+a2=168.188)=4.23"

This is the same to find the CE between two sails, like a main and a jib on a Marconi rigged sloop.
With multiple sails, find the CE between two, then connect that CE with the CE of a third and find the combined CE using the above where a1 is the third sail and a2 is the first two sails combined into a total area.
For the forth sail, add up the first three against the forth, and so on.

# Images

View all Images in thread
 Jun 08, 2009, 01:55 AM SCALE Sailor United States, MD, Severna Park Joined Apr 2008 1,996 Posts I posted an updated version of the calculator spread sheet. The change came about when I was looking at rigging diameters and found the the spreadsheet calculated the mainstay as .0166 of the mainmast diameter when is should have been .166. In looking into this to find out what it should be I found a rule of thumb that the mainstay's circumference is 1/2 the largest diameter of the main mast. The corresponding diameter works out to .155. A site referring to rigging on the HMS Victory said her mainstay was nearly 6". A 36" mast * .5 / 3.14 = 5.733" diameter mainstay. The link to the spreadsheet is in post number 10 of this thread
 Jul 02, 2009, 09:20 AM Damp and Dizzy member Bozeman, Montana, United States Joined Aug 2003 3,685 Posts Sheeting Overlapping Jib to Yardarm Jib sheeting and no-effort way to increase yard swing: Some ideas & methods at end of Post#16 http://www.rcgroups.com/forums/showt...1071509&page=2
Jul 09, 2009, 10:28 PM
Registered User
United States, MN, Brainerd
Joined Oct 2004
2,535 Posts
Adjusting brace length with a drum servo setup

With the multi track, custom diameter drum servos used on the square rigger Syren, brace length adjustment is easy if done at the yardarms or pendants rather than trying to make the adjustments at the servo drum (that can be maddening).

First attach and wind excess length braces to the drum tracks. Then adjust brace length at the yardarms as the yard rotation is fine tuned over several sailing sessions.

The attachment methods shown show how single and double braces were set up on the Syren to simulate prototypical rigging apearance but still allow fine tuning of length.
(Note: the attachment point in the single brace example photo is not proper - brace was attached there just for the photo.)

# Images

View all Images in thread
Last edited by DanL; Jul 10, 2009 at 01:49 PM.
 Jul 10, 2009, 02:03 PM Registered User United States, MN, Brainerd Joined Oct 2004 2,535 Posts New Syren page Here's the new Syren home page. http://home.comcast.net/~dplewandowski/site/