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[danielcardona]

Hello everyone


 I started a thread in this forum (beginners section) of my Dumas Star30 build, So far i Think it's going Ok but soon enough I need to choose a winch servo for it.


I have a dilemma with these two:


Hitec HS-765HB


Hitec HS-815BB


Which one should be enough for my star30?


Regards
Daniel

[xrad]

Either one will work. For 5$ difference get the BB. It has almost x2 amount of torque.  I use one of the original gearboxes in my S30...works fine, don't know the torque.  I use a 5cell 6v 1200mah 'hump' nimh pack. 

[roycv]

Hi there are some high powered standard size servos now that will easily do the job and they are cheaper as well.
Roy

[danielcardona]

Hi there are some high powered standard size servos now that will easily do the job and they are cheaper as well.


Roy

You mean I can use any high torque servo that I can find? I always thought that servos dedicated to sails have more throw compared for example to a standard one used on model aeroplanes.

[roycv]

Hi No problem as long as you are using an arm for the sails.  Just construct an extension arm and attach it to a servo top and screw it on.  You will have 90 degrees movement which can sometimes be extended.
That is what I do for small yachts.
regards Roy

[xrad]

regular servos (90 degree) have less throw than 'winch' type servos. Depending on  your Tx, you can adjust up to 150% of throw in each direction on a standard servo, which may be enough with arm attached.  For a winch servo, you would have to reduce throw to maybe say 25% to get 180 degrees of arm tip motion. The winch servos use a different potentiometer output to determine position, in other words, they can do (0 to 6.3) x 360 degrees (depending on model of servo and Tx setting). But not all Tx's can do this.  I use a Spektrum Dx6e which does NOT have a spring return lever on the 'throttle' stick (up down left side) which is used for winch control, thereby 'holding' the winch at correct spot. And it has easy adjustability 0-150% servo travel.

I just set up a turnigy 14kg 'winch' servo to do 6+ turns for a large sailboat(xrad's ec12). Tx set at 150% travel for servo.  If i set it at 75% throw, it will do 3 turns, etc...
https://hobbyking.com/en_us/turnigytm-tgy-6114md-digital-sail-winch-servo-drum-type.html

Or you can modify a standard digital servo by adjusting the resistors for the pot:
https://learn.adafruit.com/modifying-servos-for-continuous-rotation/overview

Basically,  the PWM Rx 1-2msec signal tells the servo where it needs to be, and the potentiometer in the servo keeps it there. You fool the servo by altering the pot signal.

[danielcardona]

so standard servos have 90 deg of travel, winch servos (drum) have 360 and sail servos (those with a very long output arm) have 180 deg. Am i correct? thanks for the link to modify a standard digital servo, a very interesting read.

[xrad]

Standard: 90 degree


Winch: (0-360 degrees) x 1-6+ turns  = 0 to ~ 2160 or more degrees (varies by model/manufacturer/settings)


'Arm' servo = varies by manufacturer , could be 90, 140, 180...etc

[roycv]

Hi just to clarify using a standard servo as a sail arm winch.  I fit the arm on so that it is extended in line with the sail sheeting when the sails are fully extended. 
This stops an unexpected gust of wind pulling the servo arm against the gears etc. 
I find 90 degree movement fine, the pull on the sheets can be doubled by fixing a pulley sheeve on the servo arm.
In an old yacht I have built when the standard servos were less powerful I have 2 servos, one for the main and one for the jib.  The servos work together from a Y lead connected into a single receiver socket.  The main and the jib should go in and out in parallel.  This means that the sheet connection to the jib boom and the main boom should be of equal distance from the pivot point or gooseneck fitting.
Most operators have the sails on the left hand stick, pushing it away from you is 'sails out' and pulling it towards you is 'sails in'.
Hope this helps,
regards Roy

[danielcardona]

Hi just to clarify using a standard servo as a sail arm winch.  I fit the arm on so that it is extended in line with the sail sheeting when the sails are fully extended. 
This stops an unexpected gust of wind pulling the servo arm against the gears etc. 
I find 90 degree movement fine, the pull on the sheets can be doubled by fixing a pulley sheeve on the servo arm.
In an old yacht I have built when the standard servos were less powerful I have 2 servos, one for the main and one for the jib.  The servos work together from a Y lead connected into a single receiver socket.  The main and the jib should go in and out in parallel.  This means that the sheet connection to the jib boom and the main boom should be of equal distance from the pivot point or gooseneck fitting.
Most operators have the sails on the left hand stick, pushing it away from you is 'sails out' and pulling it towards you is 'sails in'.
Hope this helps,
regards Roy

Hi Roy, thanks for chime in. The pulley sheeve that you were refering to, is it a kinda of mechanical advantage? Would love to see some photo's or drawings explaining that. Many times I see photo of builds showing the radio installation inside a sailboat and its fascinating how many builders come up with different ideas. Seems everyone have there personal setup. I myself if I didn't had any instruction photo's what to do in build I really dont know were to start . Probably I would just copy my dragon force RG65 boat setup.


Regards
Daniel

[roycv]

Hello Daniel, I think the best thing is to read through this explanation.

http://www.explainthatstuff.com/pulleys.html

If you have a problem perhaps send me a PM.
kind regards Roy

[danielcardona]

Hello again everyone

 
Today after a months wait for my servo to arrive it finally ended. It took so long because I ordered it just before the christmas holidays and the postage takes quite a while to arrive because of that.


The servo is a HS-815BB, i was a little bit shocked when i opened the parcel, and part of it its my fault because i didn’t read the spec regarding the dimensions of this thing...it huge!.


Another thing that again took me by surprise is the note left into it’s packing, saying that it needs at least a 1200mah battery and consumes 800ma unloaded.. so..how many batteries i need to put to sail this thing. I’m sure at least two or so it says the note in the packing but if its so a power hungry servo, what duration i’m expecting using a 2000mah eneloop battery pack?


Maybe i might get a smaller servo , the 765bb perhaps?

[roycv]

Hi in reply2 I suggested a standard size high power servo at no more than £5, 

I am fitting out an Aeronaut Bella which is a similar size to the one you are making, with this 90 degree servo.  You can get a 180 dgree standard Hi power servo if you look on ebay as well. 5kgrms / cm will do the job
You can also buy a cheap stand alone BEC so that you can run the RC from the large battery.
regards Roy

[danielcardona]

yep you did roy, always listen to the professionals  , i will see if i use this one or buy a cheap one as you sad. well the servo suggested by dumas is even bigger, so i may try to use it as i don't have any idea were to use it instead.


Have fun building the Bella! Aeronaut make so very cool kits and very good quality ones.


here's mine below

[roycv]

Thanks for the picture on Bella, have you sailed her?  Is she tender in a good wind?
regards Roy

[danielcardona]

Thanks for the picture on Bella, have you sailed her?  Is she tender in a good wind?
regards Roy

no i didn't sailed her yet, she still needs servo's, rigging and a good coat of varnish. 

[roycv]

Hi danial, if you see David Abbott please pass on my regards, hope you get to sail her soon'
Roy