|May 12, 2009, 03:27 PM|
Design Details for R/C Square Rigger Operating Systems
Starting a new thread to pick up discussion and sharing of ideas for designing and building prototypical operating components and systems of R/C square riggers or similar scale sailing vessels. The general idea is that the many discussions of the above type of technical detail that is posted in various other threads (eg Sloop or War Constellation, Square Rigger Kit -18 Gun Brig-of-War, A 4-masted Barque, Tops'l Sloop Providence Build, etc) could be posted in a "tech thread" and linked from the other threads. All the existing stuff could stay where it is, but as re-discussed, maybe those threads could be referenced through a link posted in this new thread.
Some examples of topics for this thread:
- how to make operating scale blocks
- how to rig yards for maximum rotation
- servo specifications and detail of setups
- controlling slack in braces
- servo activated steeering tackle
- crossover jib mechanisms
- approaches for quick reefing of sail
- observations on tacking, etc vs sail set-up
- control electronics, Tx programming, etc
Hope this makes sense.
A note - Please post threads with a title that has the key thread topic clearly indicated to help searchability.Thanks.
|May 12, 2009, 03:45 PM|
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.
|May 12, 2009, 05:02 PM|
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
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, 07:34 PM|
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.
|May 12, 2009, 07:49 PM|
A reader's digest of building ideas from the pond sailer Pamir
Diagrams & photos from my two Pamir threads. Of course, I am proud of the whole discussion; many modeler's chimed in with valuable ideas and suggestions, and you'll need to read the whole thing to get the benefit of all the shared wisdom. But for quick reference, here are some specific posts.
Boyle's 1930's free sailing square-rigger design diagrams & tips. Very valuable introduction to model square-riggers, I thought:
Now, my picks from the 2 threads, concentrating on photos of design details.
"Discussion - A 4-masted barque pond sailer"
Post #1 photos of rigging details as free sailing barque (prior to RC-ing her)
Post#10 photos of RC bracing via parallelogram method
Post#11 adding fore&aft sheets to the yard brace servo (diagram)
Post#23 Maneuvers - tacking with sternboard, wearing short around, & boxhaul diagrams (from Harland's book "Seamanship in the Age of sail)
Post#36 Sport Bec solution to battery low voltage problems during strong winds
Post#69-74 Spiral bracing theory and design photos;additional verbage in subsequent posts, too.
"Discussion - A 4-masted barque, Part 2"
Post#2 rigging diagram of the overlapping jibs
Post#11 hull dimensions and construction materials
Post#29 some text about the yard cranes made from brass screweyes
Post#31 Pamir sailplan url
Post#36 Craigtx's square-rigger photos on launch. Very nice 3 masted vessel made using Boyle's sailplan.
Post#52 real Pamir photos url's
Post#60 text describing model Pamir braces
Post#64 photos of model braces and sheets
Post#78 photos of the Pamir's course jackstays
Post#81 photos of a more elegant jackstay design by DanL
Post#117 Jarvis Brace Winch url's
Post#128 photo of rudder extention
Post#153 photo of home-made servo saver on rudder
Post#161 heavy weather sailing Spring 2009 under reduced sail
Videos of the barque sailing and maneuvering are scattered throughout the 2 threads, with varying url's. One multiple videos url is:
|May 14, 2009, 10:41 PM|
Philosophy for the beginner square-rigger skipper
For the modeler enthralled by the idea of sailing his own square-rigger, the requirements can range from simple (my ships) to complex works of art (DanL's brig, to name one). Any level of scale detail is possible, and running rigging can be as complex and as near-authentic as you wish to make it, or simple and workable. Expense is up to your pocketbook and goals; I started with a $45 model and have worked up to a $200 model. Scratch building, at a simple level, is cheap and fast. I am more interested in sailing operations than in scale detail (though I revere the master modelers who build museum-quality square-riggers). The modeling literature makes RC square-riggers sound pretty esoteric and difficult, but my experience would refute that.
Free-sailing square-rigger models (no RC) are a good place to start, I think. These ships can be a lot of fun to sail, if you have the right pond. The only requirement is that you have a way to get to the ship: either by walking around the pond to pick her up when she beaches on the shore, or, even better, by using a rowboat or kayak to grab her (for sail adjustments) while she's at sea. It's also nice to have a pond free of shoreside trees; trees will distort the wind, making voyage paths harder to predict, and generally increasing the frustration level. New subdivisions often have ponds whose landscaping has not yet grown to the size to affect the wind. Since sailboats are silent, there is less neighborhood opposition to sailing them than to operating noisy, glowplug-engine powered speedboats. I've never had anybody complain about my sailboats; actually almost everyone, adult to kid, finds them fascinating. If you don't have the right pond, or a rowboat, you can still sail if you attach a fishing line to the craft. I've done that when sailing at limited-shore-access ponds. For voyages less than 50' offshore, the fish line & reel method will suffice. You can, of course, sail as far off shore as you have line on the reel, but the line drag will affect the ship the more she has to haul.
Free-sailers are cheaper and faster to build than RC (needing as little as a week), getting you out on the water fast. They will teach you more about balancing the forces of wind and wave than an RC ship. Balancing these forces is a necessary skill for all square-rigger sailors, both model and full-size.
My first square-rigger model was a 16" free-sailer schooner converted into a free-sailer brigantine. I replaced the foremast with a new one flying squaresails. I patterned the new spars and sails on a diagram in Howard Chapelle's "The History of American Sailing Ships"; many libraries will have this book. Masts and yards were simple dowels, sails were cut from Tyvek and glued to the yards. I added a deep fin keel which I could adjust (fore and aft) to position the center of lateral resistance (CLR). After placing simple braces on the lowest yard, I was ready to go :-).
The schooner/brigantine has no rudder, which forced me to learn about using sails to steer. Differential sheeting of foremast squares and mainmast fore&aft sails allowed me to steer, and I could adjust the sails and keel to enable the ship to sail upwind. Additional lessons included addition/subtraction of sails to match them with wind velocity.
Seaworthy Small Ships Schooner kit "The Coaster":
Brigantine photos and description:
My next square-rigger was built using ideas from Boyle. Pamir was, initially, a free-sailing, 4-masted barque of about 36" hull length. I had lots of fun applying differential sheeting lessons I'd learned on the smaller brigantine to the larger craft.
Then, to replicate real square-rigger sailing maneuvers (tacks and wears), I added RC to the braces, and then RC to the rudder. As I gained experience, the Pamir's bracing was extended aloft to refine control of upper yards. All servos were left exposed on deck, so adjustment and fine-tuning was easy compared to RC gear buried below deck.
For your first RC square-rigger, I'd recommend leaving the servos exposed; you will, unless following plans of a proven-design RC ship, be experimenting with your running rigging, and that will be facilitated by exposing your RC gear. Pamir is 3 years old, and the servos have been splashed lots of times, but they keep on working. The RC receiver needs water protection, but the servos can stand the splash. With planning, and a big enough deck hatch, you may even be able to move the servos below deck after the system is working to your satisfaction.
Pamir is a great sailing craft. She was quick to build (a requirement for me), and easy to adjust or modify. She is not a detailed, museum-style model, but she looks fine offshore and handles very well.
For anyone new to square-rigger sailing, a great book explaining the intricacies of square-rigger maneuvers is John Harland's "Seamanship in the Age of Sail." It can be picked up for around $40 (used) to $50 (new) from Amazon. Harland is a modern historian who has examined the historic sailing methods and historic textbooks, and has put together a compilation with superb illustrations.
|May 20, 2009, 11:41 AM|
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:
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.
|May 21, 2009, 10:47 PM|
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.
|Jun 05, 2009, 03:29 PM|
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
|Jun 05, 2009, 10:57 PM|
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.
|Jun 06, 2009, 01:50 AM|
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"
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.
|Jun 08, 2009, 02:55 AM|
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, 10:20 AM|
Sheeting Overlapping Jib to Yardarm
Jib sheeting and no-effort way to increase yard swing: Some ideas & methods at end of Post#16
|Jul 09, 2009, 11:28 PM|
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.)
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