Good info on the RMG John, is it right that the RMG also has built voltage reducer (BEC) so you can run lower voltage rudders servos off the 7.2 volt circuit, required to run a RMG ?
Yes. Works great.
John
some new pics
ClaudioD
Yes basically when you run a RMG you only need one battery pack to power everything as the power from the battery pack is then sent to the Rx and rudder servo. Today we were training in 17-25 knots of wind, B rig condition for our IOM and I use my little 1000mah 7.4v lipo at 59gr and I sailed pretty much continually for 3 hours no problem with still plenty left in the battery pack.
As for the mould my mirror doesn’t even look that shiny !!! that should make some fantastic hulls !
Hi,
I appreciate the ‘publicity’ for the RMG, but some of the parameters like : speed too high, weight to high and costs too high, are not compatibles, for the time being, with the Esterel project.
About the ‘shiny’ it is very funny, if may happen that at the end I will use 800# sanding paper to add some roughness to the wet area !!!
ClaudioD
Claudio,
Would it not make more sense to abrade the finished hull below the waterline rather than the mold. I’m thinking in terms of a satisfactory release from the mold - while 800 grit is still pretty fine does it not make it more difficult to achieve a thorough wax coating?
Regards,
Row
PS. Just re-read your post & think I misinterpreted what you’re saying about adding roughness. I initially thought you were advocating the roughening up of the mold below the dwl: obviously (now) that’s not so.
…Note to self - read the xxxxxx post before replying!! (especially when under the influence of intoxicating liquids)
Hi Row, of course the 800# sand paper will be for the hull although not sure yet !
ABOUT SAILS !
After some pm exchanges with Alan and AC120 sail plan, I started analyzing more closely the sails design approach for Esterel.
Fractioned rig are commonly used on our models.
From books, the aspect ratio is the paramount parameter to increase sail efficiency and VMG performances. Higher is, better is, but!
The high aspect ratio does produce also a higher CE point that will reduce the lateral stability.
As usual a compromise is needed!
The Jib luff is generally dimensioned to the 8/10 of the Main Luff.
I would consider a 7/8 for Esterel.
Just to quantify this point:
the nominal Rig 1 Main Luff will be 1750mm
the nominal Rig 2 Main Luff will be 1600mm
For the Rig 2, as example, with the 8/10 option, the Jib Luff will be : 1600 x 0.8 = 1280mm
With the 7/8 option, the Jib Luff will be : 1600/8 x 7 = 1400mm
It is expected a better performance with the 7/8 Jib.
No longer Luff considered above 7/8 !
The mast shall be tailored as consequence. The CE position is considered too.
About the surface ratio between Main and Jib, the following considerations are taken:
-The Jib is providing most of the sail power.
-The Jib, out of the two sails, do not suffer mast turbulences because working on “clean air” and because of that there is the interest to increase the surface as much as possible compared with the Main.
- Most of the Rules are limiting that choice.
- Genoa is not considered, therefore only the forward triangle is used.
- The AC120 Rules call for a Jib surface of max. 55% of Main surface and personally I consider it a reasonable value.
…
Jib shape, my choice will be thus 55% of Main and a Luff at 7/8 for Rig 1 as above drawing.
- The Jib leech will be as close as possible to the mast and probably with a small roach.
- I will keep the Jib as close as possible to the deck.
Some more next post ,
ClaudioD
ABOUT SAILS
When close hauled the sail shape is rather flat within the selected draft between 8 and 12% of the cord.
This shape is not anymore valid for running or reaching, where the sail should have more draft.
The problem is more visible with the Main.
One way to get more draft is to introduce a Boom pivot offset.
The basic effects of the offset is visible in this drawing :
…
The blue profile is the normal employed for the Main in both conditions where there is a small offset due to the boom anchoring point and Wang. This show a small amount of draft increase when the boom is open to ~80°, while the red ones are function of the amount of offset.
In the drawing the offset are for 1, 2, and 3 cm.
This is obtained with a specific jig see picture below.
The Main Boom offset shall offer better performances when running or reaching
ClaudioD
I have a slightly different opinion on the foresail size… A big jib may not give you better performance.
If you have a large jib, you have a long jib luff coupled to a bigger surface area, you can suffer from more from headstay sag, which will hurt your upwind progress if your looking for good VMG.
Maybe food for thought?
Jim
I am guessing that you are intending to stay away from using a genoa because of the complications of sheeting it?
I have seen genoa & mainsail sheeting done with one winch, but it is messy, simpler and better with two in my opinion (one winch for genoa loop, one winch for mainsail sheet).
A second winch means more weight I suppose, that is clearly very important in your design from previous discussions.
However, two smaller winches could perhaps offer some advantages over just one large winch???
Hi pen,
probably you miss something and this is the sail area. The film is showing how a single winch got troubles to pull 5200cm Main sail under 18kt.
ClaudioD
Hi Jim,
you may have a point, but, as I mention, the mast should be designed accordingly.
Is also true that the big jib may suffer to close the wind and therefore this intrinsic weaknesses may suggest a different sailing tactic to reach the buoy.
With the 7/8 option, I’m also considering the use of a more rigid stay with the addition of a hollow carbon tube.
If the tests prove to be negatives, I will consider lower aspect ratio for the jib surface.
Cheers
ClaudioD
Good point, but you can also lower the aspect by having a longer foot for same surface area to resolve sag, that maybe would affect head sail efficiency but would increase power by lowering the height of the headsail (and CE) … but is that what we want from a Jib … POWER ? or am I missing something here ?
Alan
Actually I have jumped ahead of myself in above post, only because I’m of the opinion you need more than one set of sails to cover range of wind conditions.
It make sense to me that, if the boat has increased heavy displacement for higher wind speeds then it needs more power from its sails, so they need to be fuller. The fuller the sails the larger the jib to maintain pointing, whereas, a boat adjusted to lighter displacement for low wind speeds can do with less camber in the sails and so will point higher, and so does not need such a large jib.
Yes Alan !
The large jib may not allow to point up, but making SPEED Yes.
Cheers
ClaudioD
Alan,
Of course, as on real world, the models too need various sail setup/rigs
Nevertheless I’m not sure to have understood, you mean : strong wind = fuller sails
For me is just the contrary independently from displacement or I miss something !
Cheers
ClaudioD
Based upon the fact that the wind force at 1.6mt from water is not very different from the one at 1.45mt, the depicted short mast configuration should cope with a wider wind range. The only change is the Jib dimensioning for the same surface.
Which of the two setting will be better in close hauled conditions, aside the fact that the CE moved down by 2cm ?
…
ClaudioD
PS : added the CE data
What I meaning was with increasing wind speed and reduction of sail area changes the ratio of displacement to sail area (see attached chart)
Here my thinking was that maybe ? it is better to increase Jib area ratio in higher winds, to have fuller Jib to get more power needed to drive increased displacement ratio …ala M-Class !?
Alan
P.S I take the above plan with 500 mm Jib foot 
Alan,
this point was discussed with the Class M chart and indeed the fore triangle is proportionality bigger with the wind increase, but this do not mean to be ‘fuller’ at the contrary the jib draft is rather low !
The power/lift produced by the jib in this case is function of the wind speed and surface.
Taller jib will offer better performances then the shorter one in spite of higher CE and potential stay sagging !
I should find some class M pictures with 25kn !
Cheers
ClaudioD
I did not found a picture but I found an interesting and nice film with Walicki interview :
http://youtu.be/WcGtuhvh0Uc
In this film is clear the wind strength as well the flat jib with a Rig type C
ClaudioD
PS: others video with strong wind and sail adjustments
http://youtu.be/rDony7tDCgg - Marblehead
http://youtu.be/wj5tPSI1AA8 - IOM