Came across this web site some time ago and thought it might be of some use to calculate your required servo torque.
http://www.joliebrisemodels.co.uk/tenth/servo.html#calcwind
Obviously, the results given are only sheet loads and do not take into consideration any frictional loses in the system, but at least its a starting point.
Regards,
Row
Thank you Row, very usefull !
ClaudioD
Hi Claudio, very cool … particularly with wet sheeting working on 90 degree turns, this idea will help reduce drag considerably (CAP bearing pulley) but need to careful that it is not too over-engineered.
Cheers Alan
Hi Alan
was just an idea, while waiting my band saws, and it turn out that it is feasable also with the simple vire fixation and is strong enought to carry the load.
Certanly the advantage of a pulley reducing the friction is not very much energy save compared to the 90° bent tube !
Today I’m working around the idea of installing a genoa, but the few schematic circuits found are very complex, any help in this direction ?
I’m preparing a deck mock up to install one of the circuits found in order to understand as it work !
Have you seen as is working the genoa in this model ? : http://www.youtube.com/watch?v=05945XVmzeI
Cheers
ClaudioD
Claudio, The Sprinta is a very nice quarter tonner and looking at the video sails beautifully with Genoa at all points of the wind, can only guess it uses dedicated servo with some sort of spring device to move the genoa so quickly when going about. (see genoa sheeting tension)
Also like the main traveller, wonder if you can adjustable it while on the water, that would be a dream :rolleyes:
I have send e-mail off to the manufactuer to see if they can provide any further information.
Cheers Alan
Hi Alan -
if you get a reply, and if not too much trouble - would you mind posting information here? This boat (and the RUBIN) are two that have interested me for some time. They sail nice, and look like a “real” boat when on the water. Much appreciated of any information you find/get. Thank you Dick
I would like to knows myself, but I’m pretty sure that the answer will be : buy one Sprinta RC ! ~ 750 €
It is written that the genoa is controlled by servo computer, what that mean ?
Meanwhile I draw up a circuit for that purpose. It requires of course 2 winches
I do not know if I made some mistake with all these wirings !! let me knows if you have comments !
The winch 2 simply move the “ring” from right to left.
The tighten /ease off is carried out classically by the Winch 1
Since all the drawings togheter where rather messy, I just separated the functions with the relative drawings.
In the drawing 3 the ease off the Jib is controlled by the winch 1 as well the Main.
Increasing the lenght of the blue line impose the move of the winch2 toward the bow.
If necessary, the weight balance could consider the relative position of the two winches as far can be done inside the hull.
Actually the set up is referred to the CD 43" and this may give the idea of the circuits lenghts.
ClaudioD
PS :
I wonder if with the appropriated dimensions of the two drums, one could use the same command to drive both winches.
actually as reported in the drawings :
Winch 1 travel sheet for 310mm going to main and Jib
Winch 2 travel sheet to move from right to left for 510mm
I am planning a similar setup on my J boat when it gets built. I figure a 280 winch for which side and a 380 to control sheeting.
Possible sail plan with genoa !
ClaudioD
It’s a holiday here in Germany so won’t get response until Monday but will feed-back what they have, Dick their site is here http://www.ramoser.de/home_d/sprinta_rc_d/sprinta_rc_d.html in German, if you look under handler, there is a list of dealers including 2 in the U.S Dick, but suspect they maybe only flight boys as the company makes props.
Company is near Munich (approx 3 hrs) and thinking of making run, if there is possibility to test sail & if it works as well as it looks, I can feel my credit card getting excited:p
Keep you posted on feed-back. Cheers Alan
The rudimentary mock up is working as expected !
Need some adjustments & refinements once in the hull.
1 - The best position of the pulleys and fairlead.
2 - The servos position seems OK
3 - Tubing are needed to separate and guide the sheeting circuits.
4 - The rig can pass from a normal jib/boom setting to a genoa one without modifications .
Cheers
ClaudioD
Hi Claudio, with your set-up having the ring transfer sides (tacking) with winch do would be as fast as we see in the video ? the word you picked on earlier “servo computer” seems to be the solution the Sprinta has used …and there must be a spring involved, trying to get my head out the traditional thinkingl box is the hardest part.
Found another video …and this one shows sailing in heavy air and the main is reefed !!! :long:
The meausurements in terms of speed are not very encouraging !
The distance to pass from one side to the other is equal to 49cm (19.3")
The GWS S125 6T servo requires, for 49cm, 8" at 4.8V and 6" at 6.0V >> too slow if compared to the Sprinta RC that take only 3" as measured in the filming !
I checked the Eurgle 10y 3.5turns, limided to 37cm (14.5"), requires 4" at 4.8V and 3" at 6.0V. unfortunately is not sufficient to cover the full travel from left to right in this particular project.
Another element is the overall weight of the system that shall not be too high.
Actually the two winches + the rudder servo + Rx + 6.0V Bat = 210g
I need to find another solution unless the Sprinta RC Manufacturer would like to sell only the servo ectronics so far can be adjusted for various boat dimensions.
Waiting Alan findings !!
Hi Alan
just crossing our messages.
Probably a continuos rotation servo , assuming the most speedy one are around 0.18sec/60° , therefore with a drum dia of 38mm and for 49cm long sheeting it requires some 4.1turns and it will take 4.4 sec. Still above the Sprinta RC model !!
A continuos rotation need “end stops” switches on the power lines
ClaufdioD
You could probably use a big arm winch(Hitec-815) to get the speed. I would think that for swapping the ring from side to side you wouldn’t need that much power. You might have to go to a digital to get the holding power though. I’m wondering if the “servo computer” is refering to channel mixing in the radio. I don’t have any specific ideas but it seems to me that channel mixing could be used here.
I’m not totally convinced that you should use a single servo for the sheeting. Since the camber and twist of the genoa are controlled with a combination of “ring” position and sheet length you might find a position where you couldn’t get the jib and main shape to match. Not having any real sailing experience, I might not be totally clear on positioning of stuff for various point of sail.
I’m going to follow this with great interest. I’m sure I will build something with muiliple channels sometime.
Another thing I’m wondering is how they get that much righting in a model with no bulb.
Don
Hi Don,
I was thinking about an arm servo, but it does’nt work for this application unless my brain does’nt work either !
I started to make a simpler circuit and using the Eurgle servo . It requires 3 sec for 3.5 turns and 37cm sheet lenght.
Almost all pulleys are removed !
I’m not yet sure that it will work properly.
The drum should be almost hermetic to avoid loosing the sheets since some slack will be better .
I’m still trying a better solution !
Cheers
Claudio
Claudio -
maybe something like this where (depending on initial sheet winding) as drums rotate, one lets out the sheet while the other retracts it. Could replace a standard servo with a higher speed, reversible electric motor for faster revolutions.
There is also a German made double drum ( each side of motor) with step-down drums - but was very expensive as I recall. Will see if I have a saved photo some where.
Dick
Hi Dick
I appreciate.
The servos used are also double drum, the point is that for the 43-900 model the ones I consider are reasonably adequate, so far 37cm travel are obtained .
Of course I have to try first on my mockup.
For larger models the lenght of the external “Ring traveler” will increase and the servo shall be different like the RMG 's. or similar.
Another subject is that une side of the sheet is ‘pulled’ and do not present problems, as instead is the sheet that is ‘pushed’ and some device need to be developped in order to collect the loose part of the sheet.
Cheers
ClaudioD
Ouch my head hurts :hypnotize… spend half the day jumping around German forums looking for information on the Sprinta.
Firstly there is only one winch used & servo for the rudder, winch servo drum is 80-90 mm anyway pictures paints 1,000 words, Claudio you will work it out pretty quickly so I won’t waste time trying to explain …look at these first http://picasaweb.google.com/ahcling/SprintaRC02?authkey=Gv1sRgCLiT-YfBu5nRHQ#
So that’s all the inside running gear, finally found video explaning how it works but sorry it’s in German, if you follow the graphics this is what you need to know to understand the system:
Green = Genoa guidance circuit
Red = Main sheeting
Yellow = Genoa sheeting
Blue = Brake line, which also used for main sheet control
There is a pulley forward below deck (blue line with V) and as the boat tacks, this pulley pulls down (acting like a brake) and brings the Genoa to the centre-line of the deck, and then the brake lets off and pulls the Genoa in on the opposite side of the deck.
Here’s the hard part, both the Main and Genoa work off the same winch, but when the Genoa changes sides the Main sheeting does not move (clever little cookies)
Hope it helps…Cheers Alan
I see the winch and two servos. There is the rudder servo on the port side of the winch. It has a pushrod. There is another servo on the starboard side of the winch that has a line that goes off somewhere???
Don