Genoa on IACC 120

Other America's Cup Boats
21

Hi to all
Excuse me for the late comment, but I think that could be more polite well knowing the history before writing: any photos could speak more than write words

Urca AC/10 ITA 34 winner of selection for AC10 cup 2007 with the boom for jib
http://www.progetto-urca.com/urca/CA07/valencia_2007/piccole/01.JPG

Luna Rossa AC/10 ITA 25 winner of AC10 cup 2007 with genoa
http://www.progetto-urca.com/urca/CA07/AC10_2007/grandi/1_resize.jpeg

Urca AC/10 ITA 34 winner of AC10 cup 2008 with genoa
http://www.progetto-urca.com/urca/CA07/AC10_2008/Coppa08/grandi/14.JPG

http://www.progetto-urca.com/urca/CA07/AC10_2008/Coppa08/grandi/17.JPG

for other information could see
http://www.progetto-urca.com/urca/CA07/AC10_2008/Coppa08/index.htm
http://www.progetto-urca.com/urca/CA07/AC10_2007/index.htm

If anyone need see more images about mine genoa system, could see directly on mine site at this link http://www.progetto-urca.com/urca/ the images taken in Hobby Model Expo of Verona 2011 at this direct link
http://www.progetto-urca.com/urca/Eventi/modelexpo2011/URCA_vasca/index.htm

The genoa is controlled by 3 winch:
Nr. 1 that turn from one side to the other the genoa; it is not proportional and controlled by micro-switch for the end travel.
Autocontructed: 80 kg force of traction, 3.0 second to travel the 90 cm needed from one side to the other

Nr. 2 for the precision proportional trim for the fine regulation of sheeting (Special RMG 380 customized)

Nr. 3 for the genoa leech tension working with a barber positioned on the rail of sheeting point

Naturally for tacking is sufficient to utilize only nr1 winch controlled by the right transmitter stick: due to internal mechanic the regulation is completely symmetric on both boat’s side.

Electronic programmable mix allow to release a little the trimmer (2) and the barber (3) during movements left/ight and during opening regulation to allow best sheeting angle.

any closest details
http://www.progetto-urca.com/urca/Eventi/modelexpo2011/URCA_vasca/piccole/URCA%20MODELEXPO%20VASCA%200130.JPG

My complete genoa system on AC/10 weight less than 450 grams with a medium sheeting speed under charge of 350 mm/sec and a power of 80 Kg of traction

Bye

P.s. a similar system utilizing nr 2 (+1 optionally 1) digital arm servo (quite 150 grams totally) could be well used on one AC120 boat without problems. Anyway a normal jib boom could work well for competition use. My AC/10 didn’t gain nothig by utilizing genoa. The only advantage is during cicling utilizing genoa to improve quick and controlled movements of the boat

22

Welcome ClaudioV,

It’s an honour to have you join us :slight_smile: albeit this topic was started over 1 year ago by myself I have been searching for Genoa ideas ever since, as you see earlier in this thread I had found your wonderful AC 10’s which I marvel over (read dripple) however had not opportunity to persue more about AC 10, until we met only recently in Italian forum.

As you have probarly read from ClaudioD threat we recently discovered the Sprinta RC which is made in Germany by Ramoser Technik and it captured my imigination having only one RMG winch for Genoa and main sheet control. I’m buying one boat to experince and learn more about Genoas on RC sailing boats.

Had the pleasure of looking at the boat first hand only yesterday and was very impressed with their simple solution which is used in 120 cm yacht. Once have I can get some clear time in the next few days need to clear some build projects off my bench ;), I will come back with more quetions if you don’t mind, as I would really like to trial al Genoa on 120.

Cheers Alan

23

I move this message from the ClaudioD thread to this one.

(Don Asked this question about the commands of the Sprinta RC sail winch.)

This is the first setup I used. But it’s not intuitive, because you have very little movement to adjust the hauling and it’s inverted depending on the tack. Not very easy with the left hand while sailing with others!

For my second configuration, I hacked a very cheap Chinese radio set by adding an inverter to reverse the left stick pot and two resistors, in order to have the full stick movement for each tack.

In other words, if we say that, originally, when the left stick is up, the value is 100, the center is 0, and the down position is -100, the role of the inverter, when it is in the right hand position, is to give values of 0…100 for the full stick movement, and when switched to left, to give the values 0…-100. The modification was easy, as shown in this photo:

But it was not fully satisfactory, because the thumb must leave the stick when I activate the inverter.

And it remained the problem of the main sail loosing when tacking windward as the synchronisation with the trim servo is all but not easy to do.

Finally, I use a sophisticated cheap Chinese radio set, allowing customised firmware (*) and I do all the stuff using the mixers and setting logical switches and channels.

(*) (yes, that exists: for me, a radio set, with one transmitter and one 8CH receiver, sold GBP 52.34, VAT included, is cheap ! Your mileage may vary. Note that to be able to use a customised firmware, a programmer is needed, it’s sold 15€ and five leads must be soldered in the transmitter.)

My final configuration is as follows: I disconnect the main sheet from the ring and connect it to a servo winch (in my case a Hitec, as I don’t need speed, only couple) replacing the trim servo; the right stick commands the rudder, the left stick up and down commands together the genoa’s winch (half movement, as with the above solution) and the full movement of the main sail’s winch, the left and right movement of the left stick commands the tacking. An additional knob allows to trim the main sail.

In the following video of the transmitter simulator, look at the half bottom: CH1 commands the rudder, CH2 commands the genoa’s winch and CH3 commands the main sail’s winch.

//youtu.be/PEBIJrIf4oc

24

Hi Claudio

With this statement were you comparing Genoa vs Radial Jib boom ? where both systems have their luffs always on the boats centre line.

Most AC 120 have Jib pivot (@ 20-25% of boom chord) meaning the Jib luff is offset to Centre line at all points of the wind.

Do you think there would any gains changing from Pivot Jib to … Genoa or Radial jib boom ? this has always been the basis of my thinking :rolleyes:

Cheers Alan

25

Hi Alan,
Thanks, you are very gentle… but an honor is too much… :cool:
From my point of view is not properly an honor discovering in this topic insinuation about me and my boats… especially because it isn’t the first time so I was a little bit disappointed and I replied with facts to the insinuation because if someone is too much gentle someone other… :nonono:.

Anyway, because of I worked hard for 2 year about genoa, mechanics and its shape troubles, I’d like to give you any suggestion to make a good project for your AC120 with the best possible efficiency and performance.

Sprinta has got a simple solution for genoa movement but, if I’ve understood well the system, the main sail is always coupled with genoa and you’d only regulate the fine trimming with the third servo.
The solution proposed by me and also utilized by jpparisy with a second winch for mainsail from my point of view could work better, especially on AC120.
See also

In this way ,the acceleration after tack could be quicker and the control of the boat using rudder + main sail continuously (like on “true” boat) could give more realism and more performance in close hauled or when you want to gybe or to bear away quickly or rounding the mark releasing main sail when is needed.

On my first boat, an AC120 of 2002, I didn’t realize a genoa but I put a servo arm to control the sheeting point on the mainsheet post that allow to release quite 45 degree of the mainsail. This boat, realized from a project that I buy but not so good, isn’t very well equilibrated and also has got an hull + the various center that make the boat not stable especially in close hauled (it is luffing continuously with more than 30 degree of heel)
With the third servo, releasing a little the main sail only during gusts, the boat is very well actively equilibrated and gains a lot of performances.

After establishing the main servos scheme, the second very important thing is the stiffening of the rig.
With a boomed jib, if the mast has got a little bit of lateral flexion there are quite non changes in the shape of the jib. With the genoa sheeted downwind on the bridge, if the mast goes downwind, the genoa leech will loose the tension and the genoa loose the correct shape opening the leech.
So, during gusts, you’ll loose the “power” of genoa and the boat start luffing: absolutely no good!!! To avoid this problem could be necessary to verify the mast flexion and eventually study and realize a new shroud system by testing the rig deformation under charge

The third important thing is connected to the second: in a normal boomed jib, the efforts on sheet are little because the shape is quite completely maintained by the boom, by the tension of forestay on the fore part of boom and by the reaction on the topping lift in the aft part of the boom;
Practically the sheet regulates only the boom angle.
With the Genoa, the sheeting system have to cope with quite all the effort on the sail except the tension of forestay: so it is mandatory avoiding any elasticity in sheeting system because, in AC120, 2-3 mm on sheeting point position are more than sufficient to loose completely the shape of genoa and the problems generates are the same of previous…

The fourth important thing is to study a system on the bridge similar to real rails/barbers in way of allow the control of the genoa shape. This regulation system is permitted on AC120 but could only be pre-set on land (1 servo for Genoa + 1 for mainsail + 1 for rudder: no more radio channel allowed).

For starting I think that could be sufficient:cool:
Bye

26

From the point of view “the Jib luff is offset to Centre line at all points of the wind” I think, from my experience, that quite nothing could change in close hauled.

I think that could change something in downwind sailing.
If you go straight downwind you’ll gain a little bit of sails exposed surface but with a normal boomed jib if you go with the pivot more than 20% in fore direction, you’ll loose the stability in jib shape… I think that you loose more than you’d gain.

With a boom like Walicky system there is no problem and the jib maintains its shape if well installed and setted up on the boat.
With “mine” system that you’ll see on my Urca for Record (http://www.progetto-urca.com/urca/Record/index.htm) or in my new AC120 project see from http://www.baronerosso.it/forum/navimodellismo-vela/203203-studi-per-sviluppi-ed-ottimizzazioni-per-la-classe-ac120-9.html#post2478653 the boom pivot is aft to the forestay so, when you open the boom, the sail become automatically more “round” that is better for downwind sailing and the correct set up of boom pivot rotating angles allow to change the jib shape. My systems are fixed in the hull during construction and need a lot of precision in “manufacturing” to well working.

From my point of view, if you want to have more realism and less problems than with a genoa, this one could be the way.
Bye