Dual HS-785HB

[Jim Watwood]

I am curious. I have never seen a dual (one for jib one for main) drum winch setup discussed in these or any other forums. The HS-785HB has 183 oz of torque at 6 volts. That should be plenty.

Given that computer radios can link dual drum winches to move in tandem but still allow for independent control for trim purposes, is there a reason why the class hasn't seen more of this type of installation?

I am contemplating this type of installation for my boat.

[MichaelJ2K]

I use a 7.2 volt Whirlwind drum winch (no longer available) for both jib and main on a continuous loop system setup that works pretty good. Two drum winches can be done but you need to set up each servo with a method of maintaining sheet tension. Then there's the battery you will need with enough power to run two drum winches in unison. One drum winch and a servo to provide jib trim is all you need. If you wanted to use computer radio mixing, you might try two swing arm winch servos to operate the jib and main seperatly. Two drum winches may sound like a good idea but just remember the K.I.S.S. principle.

Mike Denest
EC12 #899

[Rick West]

When looking at a sheet line operating system there are several factors to consider and the last is cost. This is the heart of the EC12 and there have been many different driving units over the years. Today, the best that you can get is the RMG 280DL. Various models of RMG can be seen at regatta because of the changes Rob Guyatt makes in the ever quest to be current with design and technology. We have no data but it would be my guess that about 95% of the boats in the class use this winch.

You need about 16.5 inches of sheet line travel between the jib fairlead and a bow mounted pivot point. In addition to this you want fine resolution of movement over 20 degrees at close haul. The size and design of a drum for the winch is critical for this resolution. The most popular design is the spiral that allows fine movement at close haul and exponential speed when sheet to full out.

Whatever driver the system will have needs to have this resolution and sheet line travel. While a race is won by tactics and planning on the water, the ability to micro manage the sheets going to weather is imperative for full performance. A quarter of an inch of travel can be huge for the sail tuning set.

The size of the drum and the number of rotations in the servo need to be combined to achieve the above. Without R&D in the shop I do not see this Hitec servo getting the job done...maybe with a gearbox add on but I doubt it. I think it would be interesting to know what they designed this servo for.

...94

[Jim Watwood]

Thanks for your responses.

I use this winch on my Soling in a continuous feed setup for both the sheet and jib. It rotates 3.5 turns and has a drum that is 1.5 inches in diameter. It will move 4.75 inches of string with each turn for a total of 16.62 inches. It will turn 360 degrees in 1.4 seconds at 6 volts.

How does this compare to the RMG 280DL?


Picture and data can be seen here

http://www.servocity.com/html/hs-785hb_ ... tions.html

[Doug Wotring]

Specifications Updated - New 280 Motor & New performance measurements

These tables have been edited with data for the new 280 motor. The actual power increase over the previous 280 motor is about 20%. Most of this is in the form of speed. There is a small increase in torque.

Please do not compare these new specs directly with the previous numbers as it will give a false impression of the difference between the old and new motors. These new specs shown are based on more accurate measurements. If a direct comparison was made it would look like there has been a 100% power increase in the 280 motor. Whereas in fact the increase as stated above is only about 20%.

The 380 specs have also been redone and therefore it looks like this motor is more powerful as well. But in this case the same motor is still in use. It is only that more accurate specs are now displayed in the tables. Unlike the 280D and 280DL, there is no actual performance increase in the 380D and 380HD.

Mechanical Specifications (metric))
Mechanical Specifications (imperial)
Electrical Specifications
Performance Specifications: Based on 6 Volts regulated supply. Sheet speed, resolution and accuracy based on standard drums. 380D and 380HD - 32mm, 280D and 280DL - 26 mm. Actual performance will vary depending on battery capacity (mAh), type and condition of wiring, electrical connectors, switches and drum size used.

Mechanical Specifications (metric)
Specification 380D [380HD] 280D 280DL Unit
Maximum Output Power 14.3 10.7 10.7 Watts
No Load Speed 3.1 4.4 3.5 revs/sec
No Load Sheet Speed 312 359 286 mm/sec
Stall Torque 29.9 15.9 19.9 kg.cm
Standard Drum diam 32 26 26 mm
Max Revolutions 6 [9.6] 5 6 Revs
Max Travel (std drum) 610 [975] 405 490 mm
Resolution (std drum) 0.6 [1] 0.4 0.6 mm
Accuracy (std drum) +/- 1 [1.5] +/- 1 +/- 1 mm
Dimensions 79 x 54 x 60 74 x 54 x 59 74 x 54 x 59 mm
Weight 168 [175] 134 134 gm

Mechanical Specifications (imperial)
Specification 380D [380HD] 280D 280DL Unit
Maximum Output Power 19.2 14.4 14.4 mhp
No Load Speed 3.1 4.4 3.5 revs/sec
No Load Sheet Speed 12.3 14.1 11.3 inch/sec
Stall Torque 416 221 276 oz.in
Standard Drum diam 1.266 1.02 1.02 inch
Max Revolutions 6 [9.6] 5 6 Revs
Max Travel (std drum) 24.2 [38.7] 16 19.3 inch
Resolution (std drum) 0.024 [0.038] 0.016 0.02 inch
Accuracy (std drum) +/- 0.04 [0.06] +/- 0.04 +/- 0.04 inch
Dimensions 3.1 x 2.1 x 2.4 2.9 x 2.1 x 2.3 2.9 x 2.1 x 2.3 inch
Weight 5.9 [6.2] 4.7 4.7 ounce

Electrical Specifications
Specification 380D, 380HD 280D, 280DL Unit
Idle Current 23 23 mA
No Load Current 650 550 mA
Stall Current 18 12 Amps
Maximum Voltage 9 9 Volts
Minimum Voltage 3.8 3.8 Volts

[PaulP]

I have the HS-785 in one of my original boats. There is no comparison to the RMG280.

I heavy (20+ mph) winds, I have stalled the 785 trying to sheet in. It just doesn't have the guts needed for a competitive 12.

If you are just planning to build a day-sailer, something to play with, I'd say go with it. Try the two servo's, if you have them.

If you are doing it to save a buck, I guarantee you'll regret the decision. If you are shelling out $$, go for the RMG

Paul
ps: the RMG comes with the servo brake which will save your batteries on a heavy day wind. The 785 does not have this and when it stalls, it is like a dead short on the batteries. My boat with the 785 is real bad on using up the batteries on anything but a light air day

[Jim Watwood]

Paul,

Thanks for the reply.

Did you use a single HS-785 for both the main and the jib or did you use a single HS-785 on the main and a separate HS-785 on the jib?

If you used a single HS-785 for both the main and jib I can understand the servo stalling.

The use of two servos one for the jib and one for the main would give you 366oz of torque vs 276 for a single RMG. In terms of weight for the setup it would be a wash. 7 oz for a jib trim servo plus the RMG vs 7 oz for the two HS-785s. The complexity would change from a mechanical setup to a radio programming issue. Far easier, in my opinion, to let the radio handle mixing and trimming rather than a mechanical setup. But that is me coming from RC airplanes.

[PaulP]

Jim,
My set up was one servo - however I am still convinced an EC12 mainsail when overpowered by a gust, will stall the 785 used in a dual setup.

Another issue you will run into is servo travel. Depending on your radio, the 785 may have too much throw. Your transmitter may or may not be able to trim it out.

Bottom line, the 785 will work, but you'll find it won't work as well. Few if any are seen on the circuit.

Paul

[rv4pilot]

Hello! I have the answer to your question of separate servos for the main and jib. One of the best skippers on the east coast that placed well at the nationals uses dual servos with an Ace Nautical Commander radio. It has a rudder stick on the right and two verticle sticks on the left for separate main and jib control. I think this setup benefits him greatly when turning as he can either keep the jib sheeted in or out regardless of the main so the the jib helps to turn the boat using a lot less rudder deflection therefore less drag. These are two sail arm servos he has in his boat. The same setup can be easily done with a computer radio as turbojdub suggests. His setup has the two servos laying down flat on the ballast with the arms sticking up. Can anyone get the weight any lower in the boat than that? He also has a twitcher servo in there. A very simple setup that works fantastic for him. To us airplane people that sail, programming is always easier than doing it maechanically.I am not sure but I think he is using two HS-815's. I will ask him this weekend at the ec-12 races in Mansfield CT.

Is it time to sail yet?

[IanHB]

I had a two winch setup fitted in my EC12 back in the 1980`s and used it to some advantage for around 5-6 years.
It has the benefit on the reach of allowing the main to be eased whilst the jib does the driving, great in the heavy.
Slot variation and some downwind clever stuff as well. Possibly too much control to be useful in the heat of racing. Much practice needed.
The downside was getting it all to sheet in together as you rounded the bottom mark.
This in the days before computer radios so the jib was assigned to the flaps control on my six channel radio.
Now days I have a simple jib trim which allows the variation of the slot which gives me most of the control needed without the extra complication of two winches.
I would not try to talk you out of doing it but you need to have your act together to make it worthwhile, IMHO.

DO IT NOW, Before it`s to late

[s vernon]

turbojdub,

Did you note in the repsonses that the 785 is deadly slow compared with the RMG? 1.4 seconds per rev versus something like 3.5 revs per second. Big reason why we use RMG winches.

I would be amazed if anyone could use a couple of 815 arm winches on the EC12. Talk about stalling. But who knows? Maybe the one on the main is a 5995 arm winch or whatever that very strong Hitec is called. Maybe they are both 5995s.

I was just recently thinking of an RMG280DL on the main and a Futaba 5801 on the jib. The problem with that idea seems to be that both of those winches want to feed power to the receiver. I figure I might take a couple of my dead or almost dead winches and try to somehow wire them up for smoke testing. Probably a closed issue with me, but interesting to think about. I would be interested if anyone has any ideas how that might be wired up.

Scott

[Jim Watwood]

I am going to forge forward with the twin drum concept. I have acquired two of the RMG280L winches. Please don't tell the wife.

I have thought a little how I might program the set up. The radio I will be using is a JR9303 2.4 Ghz radio. This radio has two sliders in additon to the sticks. I will have the jib on one slider and the main on the other slider. The left stick will control both jib and main. This gives me independent sail control as well as one control for both main and jib.

Don't you just love computer radios.

[Doug Wotring]

To what benefit is this over a single winch and a jib trim

I have an ample ammount of jib trim to do whatever I need to do

Two RMG's although an interesting setup seems overkill not to mention the extra weight and battery draw above the ballast.

[Jim Watwood]

Benefits

Control of the main with affecting the jib trim.

Anotherwards, If you are hit with a gust ease the main, keep your course, let the jib continue to drive. With a convential setup you are easing off the jib and the main and potentially losing some speed. Or you are easing the main and jib and trying to compensate for the easing of the jib with the jib trim.

Weight of another RMG winch is an extra 3 ounces. If weight becomes a factor I intend on using LiPo battery backs. I may use them anyway. RMG winches can handle 9 volts.


So in conclusion, the control setup will be more like sailing my full size boat. A little finer control for a variety of conditions.

The risk is a more complex setup that will be more of a challenge to handle during the race.

[Winston]

A Brit friend, Martin Raishbrook, races "A" Class in the UK with a separate winch for jib and main. He has a Futaba 6EXA tranmitter modified to twin sticks. Thes sticks appear to function just like the old Nautical Commander, but the sticks are beautifully fitted into the left "circle" of the radio, instead of one, there are two sticks side by side. I asked Martin to comment on this setup and here is what he wrote:

Please see attachments of my 6EXA transmitter modified to twin sticks. This mod has been done to this tranny and my earlier Hitech one, it’s much easier if it has digital trims. I have been using a twin stick tranny for about 10 years now and wouldn’t go back. It’s particularly good on the beat when you can leave the jib driving and dump the main a bit when a gust comes along. Also at the end of the run you can sheet the jib in first to get it driving around the mark before you sheet in the main. Obviously you also have total control over the slot, handy on a reaching leg or the beat if the wind strengthens. Well that’s the idea anyway, can be a bit confusing in the heat of battle! Another plus point is less strain on each winch and you don’t have to use RMG’s. I use 2 Graupners on my A class (approx 1550 sq “ in total), you have to detach the red wire from one winch before it is plugged into the receiver and use a Y lead from the battery. If the sheeting arrangements are worked out carefully in an emergency you can easily connect both sheets to one winch if the other one fails, handy if you haven’t got time to change a winch! Please post any of this on the forum if you wish.