|Nov 24, 2012, 11:21 PM|
Made some scale sketches of main course geometry and determined brace L's for 0 deg rotation, 45 deg and 50 deg (approx max rotation measured on Syren).
The sketches show the brace L's for each rotation. The actual measured brace L at 0 deg rotation is 25" for each brace (yard end to block). Fig 1 is a scale sketch and shows that dimension. Note that the yard is rotated on a 1.5" rod, with the rotation point on the face of the mast. As the yard is rotated to 45deg, total brace L is shown in Fig 2. And in Fig 3, at 50 deg rotation, brace L at 50deg compared to brace L at 0 rotation is 2.5" shorter (47.5" at 50deg vs 50" at 0deg). Since the physical brace L of course doesn't change, that difference is the slack in the non-hauling brace. To compensate, the servo needs to be moved half that distance, or 1.25", which agrees with the on-model measurement given in the last post.
This makes a sliding servo system very easy to design.
Note that the travel and slack for the topsail yard needs to be determined. The probable slight difference in the slack development of the course and topsl yard braces can be easily compensated for with bungee used for the brace pendants on the course braces ( a good idea anyway, given the bumps and forces always whacking on the yards...)
This 1.25" travel doesn't agree with the measurements previously reported from the floor mock-up (which was 4" of servo travel). Looking at those old results, the setup geometry was wrong. The braces were run to lateral blocks, creating two angular brace runs just before the servo drum, instead of a direct linear compensation path.
Anyway, given the agrrement between direct model measurements and the scale sketches, I'm pretty confident the servo compensation pull will only need to be 1.25"
I'll likely add another quarter to half inch to allow for all the "play" in the rigging.
Thoughts? Anyone come up with a different answer?
|Nov 25, 2012, 10:13 AM|
Forecourse brace info:
Ran the same paper excercise with Corel Draw for the forecourse braces.
Total pull length for 50 deg rotation is 10.1 inches and the slack at 50 deg rotation is 3.4" (requiring compensating servo travel of 1.7 inches).
Will confirm above with on-model measurements.
|Nov 25, 2012, 10:31 AM|
Syren Brace Arrangement
Here's teh current brace arrangement, side view (not a scale drawing - just a rough diagram). The brace locations were determined not by prototype location, but by what was practical to operate the model.
Note that the foremast servo is mounted aft and the mainmast servo is mounted forward.
After all the time since the build and a lot of sailing, I wonder why I ran brace B, for the foretopsl yard, at the upward angle. Maybe to clear the rotation of the main topsl yard. But I think I'll re-rig to have it run more horizontally as shown in the dotted line. Possible issue with the upward angle run is that it pulls the hauled yard end down. It also makes the pull length shorter (due to the 3D geometry of the pull direction vs plane of yard rotation) making it more of a mismatch to the pull distance and slack development of the forecourse.
With this re-build, I'll likley try to re-route brace set B to be more horizontal.
All this is paper excercise at this point. Anxious to get to the model and see if it all works....
|Nov 25, 2012, 02:30 PM|
This is fantastic information!
Thank you for taking the time to draw the diagrams and post them for the rest of us. Clear and easy to understand. (perfect for someone like myself) ha ha
all the best
|Nov 27, 2012, 10:59 AM|
Here's a concept for Syren's sliding servos. There is no way I can easily remove the original servo mounting blocks for a new servo chassis, so this design uses aluminum brackets mounted on the original blocks - should work well.
The servos will have delrin slider blocks screwed onto teh "ears". The blocks will have chamfered holes that slide over brass tubing rails. Drum flange outer diameters will be reduced to 2.625" and the brace alignment bracket will be fitted to the sliding servo.
Hope to build and test the forward servo (controls the mainmast yards) this week.
The driver servo will be mounted transversely to allow for travel of the main and foremast servos.
Any advice/ideas welcome.
|Nov 28, 2012, 01:52 PM|
Syren Rigging Info Source
Options for rigging the SC&H brig range from the basic kit design - functional, simple to set up, but non-prototypical, to much more prototypical rigging that is much more complex to set up for sailing.
I tried for somewhere in the middle, with a more prototypical approach to the braces.
An excellent source of info on rigging a cruizer class brig is the Petraeus book, but it's not readily available. Here's a link to an absolutely great set of full plans for a Syren model, from hull to rigging.
Chuck Passaro did a super job of research and documentation. Each chapter is available as a downloadable PDF. Don't miss this if you haven't already seen it.
|Nov 28, 2012, 06:29 PM|
Dan, over on the USS Constitution Museum blog, there is a 1st person account of a Marine, Henry B. Joslin, serving on USS Syren (he calls it Serinac, but Museum concludes it was actually Syren). Would this be your ship?
|Nov 28, 2012, 11:31 PM|
Seems likely, but I need to see the future installments. Thanks - this is great new info to me.
There is a fair history of the Syren available, but a lot of gaps. Built 1803 in Philadelphia, in the Mediterranean until 1806 for the Tripolitan War, laid up in Washington in 1807, refitted and dispatched to France in 1809. In the Caribbean - Belize, Cuba, then New Orleans thruout 1813. To Boston in 1814 and captured by the HMS Medway later in 1814. Lost after that.
Samuel Leech, a seaman aboard Syren, wrote a book about his experiences at sea. Links to that and to his description of the battle with the Medway below.
Keep me posted if you see anything else. Thanks!
|Nov 29, 2012, 10:21 AM|
Per a question on clarifying how Syren yards are controlled (sorry, no video - she's torn apart for re-fitting), attached are two diagrams. The first shows current rigging. The brace slack is controlled by bungees. The servo is solidly mounted. The foremast yard control is shown - mainmast is same.
Braces run from a 4-track servo drum, through line guides that keep the braces in their drum tracks, to pulleys built on a single chassis (as a cassette) mounted to the mast, then up through the deck alongside the mainmast.
The course braces then run through blocks tied under the main top and then out to blocks attached to a bungee brace pendant. Those pendants alone control all the slack in the course braces. Because I wanted the appearance of a doubled brace, which would require double the pull length on the brace, a dummy brace was added (the servo drum couldn't pull the length of the doubled brace). The dummy brace is a single length of bungee glued into the pendant block, run back to a block on the mast (between the two brace blocks) and out to the opposite pendant block. As the yard swings, the dummy section of brace "trolleys" back and forth, looking like operational doubled braces. The dummy brace is bungee (dyed tan) because the length needs to change as the yard is rotated.
The topsail yard tension is controlled by a piece of bungee loped behind the mast and tied to the two blocks at the mast. As the yard is rotated, the bungee stretches and also slides side-to-side (trolley action),effectively balancing port/stbd brace tension.
In the new setup (second diagram), brace slack is controlled primarily by servo travel kept under tension with springs. Shorter bungee pendants will still be used on the course yard as "shock absorbers". The topsail yard will not have the current "trolley" blocks - the blocks will be instead tied to the mast with very short lengths of bungee, just long enough to act as shock absorbers. This simplifies tension control rigging aloft, and makes for a bit more "solid" tension control.
|Nov 29, 2012, 12:50 PM|
Simulating Doubled Lines with Single Line Pull Length
Most servos, even with a looong arm or biiig drum diameter, can't pull enough line to duplicate doubled lines being pulled thru a block. The effect can be simulated a couple of ways. Line pull length is kept short, but appearance of doubled lines is maintained.
These examples were used for the Syren driver boom, the course yard braces and for the tiller rigging.
|Nov 30, 2012, 10:09 AM|
Yet another drawing - pretty close to the final construction. Trying to use readily available materials. Looking now for something convenient to use for the tube mounting brackets.
2" travel should be more than enough slack adjustment - will confirm with mock-up.
I favor bungee over springs. I don't know how to specify springs or how to get the right length, force, stretch ratio, etc. Bungee is easy - just add additional strands to get more tension, cut to desired length, etc. Very flexible and a big stretch ratio.
|Dec 02, 2012, 09:19 AM|
Sliding Servo Assembly
Some pics of the first new assembly. Will test before assembling second one.
Used bungee for tensioning, but will sub a spring when I find the correct size/tension.
Need to make up a new drum assembly and the line guide bracket. The bracket will be attached to the two forward servo mounting screws.
Total travel is up to 2". Slide is smooth - slider holes for 7/32" tubing are 1/4", chamfered both sides.
Note opening for servo cable.
Used 1.5" x 1.5" aluminum angle stock (1/16" thick) cut down to make brackets.
Tried to use common, readily available materials.
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