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Old Dec 02, 2012, 09:49 AM
Paratrooper
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Eubank Kentucky
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This looks great--I always enjoy your "inventions" and this is certainly no exception.
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Old Dec 04, 2012, 02:21 PM
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United States, MN, Brainerd
Joined Oct 2004
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Sliding Servo Test Video

Pretty much confirmed the paper excercizes with a test mock-up of the forecourse geometry..
Mounted the sliding servo on a test base with a "yard" attached per the dimensions of the forecourse yard width and the onboard length of the braces.

Data:
- Transmitter: J&R 2.4GH 9ch. Channel set to +114% / -114% to get 4 full servo turns.
- Servo: HITech HS785HB, 6V nom., spec rotation = 3.5 turns, drum dia. = 1.53"
- Calculated brace pull per 2 rev's (2 stbd, 2 port) = 9.6"
- Actual brace pull per 2 revs = 10.75" (likely due to inreased dia. due to the "stacking" of brace line on the drum)
- Yard width, brace-to-brace = 24"
- Brace L, yard to drum, with yard squared = 32"
- Brace change in L, yard to drum, full rotation (64deg) = 10.75"
- Servo slide travel, squared yard to fully braced = 1.5" (slide has 2" travel max.)
- Tension: more than adequate retraction provided by 1/16" single strand of bungee on each side of servo.

See the clip for operation.
Rotation of 64deg was achieved. Onboard, due to shroud location, only a bit over 50deg rotation is possible. Having a bit of extra capacity in the hardware is probably a good thing, but the new drums will probably be a bit smaller in diameter than the current drums.
Servo setup did not have line guides installed.
Test did not factor in the vertical portion of the onboard brace run, but that should have little effect on yard rotation geometry.

Net assessment - worked very slick, smooth. No need for any bungee aloft, including the pendants. Very stable and repeatable positioniong.

Syren Brace Servo Test Setup (1 min 6 sec)
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Last edited by DanL; Dec 04, 2012 at 02:41 PM.
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Old Dec 04, 2012, 03:13 PM
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United States, MN, Brainerd
Joined Oct 2004
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Key new learnings on Syren re-fit...

Rigging line: I was very enthusiastic about rigging with the twisted nylon net twine that is commercially available - much easier than "spin-your-own".
The white twine, stained tan by the model builders at the Erie Maritime Museum, looked really great. But now I realize that it might be great on a static model, but not so great for actual working rigging on an RC model. During the servo testing, the nylon net twine definitely showed more stretch under tension than the line I made from Guttermann polyester thread. The other unsuspected problem was that the net twine easily snagged and abraded, leaving fuzzy, untwisted sections. And knots don't hold well compared to the polyester home made stuff. Soooo....I would recommend using either the braided, much "harder" surface nylon line as supplied by SC&H, twisting your own, or buying scale twisted line (available from a European supplier..need to check source). Notes on twisting your own - 1. need to make a ropewalk, 2. have about 30ft to lay it out, 3. need to use Gutterman polyester (not nylon or cotton!) thread (trust me...many tested, Guttermann the easiest to work with and by far the best finished line. Great color selection too. From JoAnne Fabric) 3. need patience - about 10-12ft of finished line is practical max, 4. need a LOT of thread, even for 1mm line (2-3mm line takes HUGE amount of thread) 5. must read references to understand hardening process - a very necessary final step in the process.
I'll be twisting new braces soon......

Transmitter:
If at all possible, use a nine channel if you are going to add any functions beyond the stock 4-function setup (rudder, foremast, mainmast, driver/headsails). I had a 7 channel, and with 8 functions on the Syren (rudder, driver, main, fore, headsail crossover, gun fire, port/stbd gun selection, external drive (used for club shows)) it was a headache. Had to choose port/stbd guns by maxing out the driver servo to trip a microswitch.
Now have a 9 channel and next step is to figure out new and better function mapping. There are two rotational levers, near top right and left sides of Tx, that I may use for yard rotation rather than the old approach of using the two sticks (both sticks needed to be fitted as non-centering with positioning ratchets). I'll post the new setup ideas for feedback soon.
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Old Dec 04, 2012, 03:44 PM
SCALE Sailor
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United States, MD, Severna Park
Joined Apr 2008
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Did you get any bowing in the yard?

That looks like a winning solution that doesn't require an engineering degree and a shop full of machines to implement.
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Old Dec 04, 2012, 04:46 PM
Square-rigger
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Klatovy, Czech Republic
Joined Mar 2004
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what jerry said ! Outstandin smmoth operation looks great ! i think combined with tube guides or pulleys for turn around corners it will work super.

Too bad i don`t have the space in Somers to change the layout accordingly!
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Old Dec 04, 2012, 09:31 PM
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What happens if you try to rotate the yard by hand, against the pull of the servo? Does it flex a little? A lot? Not at all?
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Old Dec 04, 2012, 10:04 PM
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Joined Oct 2004
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Jerry -
The test yard was an oak batten - pretty non-flexible. But the force on the yard, under the highest tension when it is squared, is not that strong. There are only two pieces of 1/16" bungee taking up the slack. I can push the servo back against the bungees with one finger. That's way less than would even come close to bending the yard.
Kotori -
I did try rotating the yard. It does flex just a little, even with pretty considerable effort. The flex is less than in the previous rig, which had bungee brace pendants and bungee on the blocks. It seemed like a pretty stiff rig. I checked side-to-side tension at various degrees of rotation, and it always seemed equally balanced.
Anxious to get it installed and tested on-board.
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Old Dec 05, 2012, 01:58 AM
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TBowman's Avatar
United States, CA, San Jose
Joined Aug 2012
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Hi Dan

Very nice. Great video of a very smooth action. Love it!

Will make my insert, servo-bracket with revised travel distance. Many thanks. I'm so glad you are revisiting Syren. : )

best regards
Tim
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Old Dec 05, 2012, 11:12 PM
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New Winch Servo Drums

Will be making new drums. The originals are still useable, but they were experimental - made with old CD's, sheet PVC, different glues, etc. They were not adjustable.
The new ones will be stacks of 1/16" thick ABS discs. They will not be glued together, but clamped together with 4 screws. That will allow changing the core discs if a diameter change is necessary to fine tune the length of brace pull between the top and course yard tracks on the drum.
The 4 screws also serve as tie-off points for the 4 braces.
A cheap adjustable hole saw is used to cut the discs at the exact diameters needed.
Sketch attached.
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Last edited by DanL; Dec 06, 2012 at 09:22 PM. Reason: updated drawing to "as-built"
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Old Dec 06, 2012, 09:09 PM
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Bozeman, Montana, United States
Joined Aug 2003
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This is all great, DanL!

btw, fly-cutters (your hole saw, in machining terms) are notorious for slinging the part across the shop if it's not clamped hard enough to the work table. So, be careful, wear eye protection.
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Old Dec 07, 2012, 07:54 AM
SCALE Sailor
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United States, MD, Severna Park
Joined Apr 2008
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Rotating the piece on a pin next to a band-saw or scroll-saw blade is less likely to mangle it - I've never had good luck with fly-cutters.
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Old Dec 07, 2012, 02:33 PM
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Joined Oct 2004
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Yeah, the fycutter is sloppy and potentially dangerous. But I don't have a scroll or bandsaw. I made the rough circles pretty easily since the material is soft and was only 1/16" thick (PVC).
I cut the discs slightly oversize, stacked the finished discs on a bolt against a backer, and trimmed to the final diameters on my little lathe. Ended up gluing the slabs togetehr. Pics of new drums attached.
Note that the servo disc buried in the stack was moved up one level to lower the lateral force on the servo shaft (See edited drawing in earlier post)
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Last edited by DanL; Dec 07, 2012 at 06:08 PM.
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Old Dec 07, 2012, 06:22 PM
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United States, MN, Brainerd
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Tx Update

Last sailed Syren with a Spektrum 7 channel. Had to select stbd/port guns by maxing out the driver to trip an onboard microswitch. Also, while handling the Tx/paddling chase boat/taking pics, the two main sticks used for yard rotation would get bumped. Or main yards/rudder on same stick was tricky.
So a major rethink of control layout for a JR 9 channel Tx is due.
Old 7ch plan pic attached, also new prelim 9 channel plan.
In the new 9ch plan, two small levers (see Tx pics) on the sides of the Tx will be replaced by larger rotary knobs and 330deg rotation pots (vs the 60 deg rotation of the current levers) One pic shows a test pot on an extension wire....
Anyway - yard rotation will be fingertip, have better precison with the full rotation, will be independent of other controls (eg not the same stick as rudder), and will not be easily bumped out of set position.
Also, since the Tx is used for many models, I didn't want to modify the right stick by adding a ratchet (that was necessary on the old 7 ch setup).
Will be interesting to think this thru and to see how it eventually works.
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Last edited by DanL; Dec 07, 2012 at 11:19 PM.
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Old Dec 08, 2012, 06:02 PM
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United States, IN, Indianapolis
Joined Nov 2010
257 Posts
Dan your improvements are making my teeth hurt. My "SC&H specs" servo setup is gonna look like a biplane made of wood and canvas compared to your spiffy P-51 Mustang lol
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Old Dec 09, 2012, 08:52 AM
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United States, MN, Brainerd
Joined Oct 2004
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Transmitter modification

Andrew,
The stock brace rigging setup is fine. Trying to mimic prototype braces is likely hardly worth the effort if fun sailing is the primary objective. But I get way to much into detail on things.....
Like this.....
To use the side lever controls on my JR 9 channel Tx for control of yard rotation, changes had to be made. The levers only rotated about 80 degrees and have a limited number of detents, not fine enough control for yard rotation. I measured the R values of the OEM potentiometer - see diagram. Seems the Tx "sees" a range of R from roughly about 500ohms to 4.5k ohms to give full range on the output to the servo. So I ordered replacement linear pots with 300 deg actual rotation, with an estimated 240 deg range of rotation to get a similar R range. Anxious to get the new pots and confirm the performance. The pots used in the Tx are cheapos. The mechanical rotation range is about 210 deg, but effective range to change R values is only about 80deg and pretty sloppy. The new pots are better quality. The new setup should give very repeatable, accurate and precise yard rotation control. Hoping for the best here....
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