Claudio …you’re a diamond 
you are the first person who clearly explains CLR/CE positioning that I understand, thank you !
Matthias all is clear now, thank you.
Gary, does that mean my epoxy has built-in suntan lotion now mate 
Dick, thanks for the tip on leaving hull on the plug, I like looking at it too :zbeer:
Cheers K1
Thanks K1
THE CLR :
It is probably the time also to adds some tricks to find important Centers, like the CB, CE, CLR :
This is the one I use, as many others in the world, to search for the CLR.
It is not a scientific method, no computer is needed, but for the modeler purposes is more than adeguate bearing in mind all the variables in the architectural design.
Ciao
Claudio
Claudia, I love the K.I.S.S principle (Keep It Simple for Stupid people) like me just for clarifaction, one just cuts a cardboard template of wet area of the hull only or should include complete hull profile ?
Further, what are the dimensions of the diagonal beam ?
Cheers K1
Only the Wet Area as depicted.
I do have in my Lab a fixed place where I hang my various cardboards any time I need.
Is the cardboard, attached with a needle, searching the equilibrium while the vertical line is already marked on the wall. I just simply kick the cardboard to let him oscillate until stops. At this moment I mark the correspondance with the vertical line.
Cheers
Claudio
This is the summary of the method described earlier.
It is not the only one of course, but for me is sufficient also beacause will be always necessary to “adiust” the mast step in order to establish the correct boat equilibrium as the Sail Plan/Wind may change. This nice activity is called “TUNING”
Finally, when all is constructed it remain to fix the Mast Step and the only “variable” that do not modify the hardware is the Lead. Is just a number or a percentage !!
It is important for the first boat to let a margin to modify the mast step position with the use of a slide plate of about 5/6cm long. Similar slide should be positioned near the bow in order to attach the jib boom . Trasverse plywood support is needed there and probably an anchorig rod to the hull bottom too. See AC33 pictures and drawings.
The above drawing reveals also others important informations as the distance of the trailing edge of the Rudder from the Stern that will help to find the position to drill the trunk hole and also similarly the distance of the trailing edge of the Fin from the Stern that will allows to fix the limits in order to perform the cuts for the Fin Box.
Cheers
Claudio
Hi guys…
Cheers Sailaddict, but we are merely the puppets for the master in Claudio
Great point Dick… have to remember that one, thanks.
Fantastic Claudio, you are a hell of a teacher my friend… thank you.
Have you started thinking about the deck K1? I have and I’m interested to see the info when its time…
Cheers
Goose
One last point on the various Centers, the Center of Buyancy - CB.
The Curve of Areas :
the COA is in my opinion the “Identy Card” of the boat.
3 informations can be extracted from this Curve :
In the drawing above can be seen that the sum of all immersed frame sections is equivalent to 422.01 cm² .
The distance of the frame from each other is 9.85cm
Therefore : 422.01 x 9.85 = 4156 cm3 or g. (1cm3 of water = 1g)
4156cm3 is the Displacement.
Taking the surface of the largest frame and multiplying it for the total LWL lenght we have :
70.72cm² x 98.5 cm = 6965cm3 this is the solid volume if the boat would have a constant section from stern to bow as the one of frame 6.
Comparing thus the two volumes we have :
4156 / 6965 = 0.596 this is the Prismatic Coeficient - PC
Large PC, above 0.58 accompanied with large displacement, will denote a boat with volumes distributed along the extremes, generally capabable of good performances with medium strong winds.
At the contrary a low PC of 053, will suggest that the volumes are concentrate at mid ship with fines water lines and capable to offer best performance with low winds and calm waters.
There are others considerations, but will be too long again.
Someone will start screaming ! another cardborad !!!
This is the simplest way to find the CB
Defining the “static” CB position it is of paramount importance.
All the static adjustments will be based on the CB.
The modeler will use the vertical line falling from the CB in order to fix the Bulb position to obtain a longitudinal equilibrium of the the Full Boat.
Most of the time is interesting to concentrate around the CB all the masses used for the RC equipments.
I Think is time to Stop booring peoples , sorry !!!
Cheers
Claudio
You are not even close to boring us Claudio… this is an amazing class in hydrodynamics and sailing theory… once again, thank you! :graduate:
At the risk of going off topic a little, it is doubtful you learnt all this in a hobby such as RC sailing, what did/do you do for a job? Design full size AC boats by any chance? Team French Spirit? K-Challenge?
Cheers
Goose
nothing about that, I was simply developping with my friends and let navigate things
above the clouds, much above !!!
Cheers
claudio
Winding up all the major dimensions
are here … 
Last remark to be considered is the one that concern de weight control against a construction Budget.
Budget gross extimation :
The tolal minimum weight permitted is …4500g
(this do not means that one should aim for more
the motor is always the same !!!)
The maximum weight permitted for the Fin+ Bulb is… 3000g
Remains for the rest of the construction…1500g
To the above shall be detracted for the rudder …75g
for the RC equipments (servos + Battery + Rx)…300g
for the Rig of 74dm²…300g
rest : 1500 - (75 + 300 + 300) = …825g
the 825 g is a confortable measure to make the Hull and the Deck including all accessories.
A good constructor may come to the End obliged to adds Ballasts to reach the 4500g and staying inside the Water Level marks.
Too heawy will sink too much !!!
Ciao
Claudio
Claudio :graduate: I have learnt more in 1 day from on boat balance than I have in 20 years of sailing … great lecture thank you !!!
I have been preparing for keel & rudder construction and need clarifaction on three points:
What are the dimensions for the diagonal beam ?
The Appendages shows the top of the keel fin to be 120 mm, however I measured (shadow # 5) from the bottom of the hull to the sheer line and it measures 128 mm.
Does this mean that the deck support for the top of the keel box & mast is 6-8mm thick ?
Attached illustration to help clarify the points
Cheers K1
Hi K1,
the diagonal beam are generally simple wood strip 6x6 , some time carbon tubes of about 4mm to 5mm diameters are excellents.
that’s means that the top of the Fin do not reach the top of the frame
Don’t forget that there is the Fin Box. Be carefull any way , the frame 5 is higher then the fin box being positioned a little forward.
ok for eyelet bolts
The thick plywood plate is not covering the fin box is only set above the mast support plate to acts as an orrizontal beam .
Probably I have to make a 3D
Cheers
Claudio
Hi Goose, getting my head around the making keel etc, for now, the only thing that caught my eye regarding the deck plan of the Italian AC 120’s is that some are using the main fairlead (and not Jib fairlead) meaning having both sheets run from one central point (better water proofing) and the Jib sheet feeds to a block on the shroud then to a loop on the deck then onto the Jib boom see attached picture … very K.I.S.S (read clever idea)
Plus I would like to have the bevel on the fore deck I touched on earlier.
Cheers K1
Another drawing fast made specially for K1, I hope with this to have added some more ints to explain the situation. One picture = 1000 words !
Cheers
Claudio
Sorry if I pick up this nice picture for the benefit of all viewers.
This is the 2008 Cup winner - the Shosholoza of Luca 71-5
Claudio
Claudio … your blood should be bottled, your a magician on your P.C thank you for thhe 1,000 word in 1 picture
Last night I went to bed following our discussion on various sail plans and came to the conclusion that I need to do a lot of trail and error to find the best set-up if I’m going to race with the Italians.
Here in Germany I have been unsuccessful in finding other R.C sailors hence it is impossible to have competitive bench marking … so I got up in the middle of the night determined to have two boats and made another hull.
Just now popped it off the mold … perfect @ 230 grams and now NZL 87 is born.
Cheers K1
:long:
K1 Only the infinity will stop you !
Ciao
Claudio
Yesterdays Court decision allows Alinghi to change design rules surrounding the defence that will govern AC33. Specifically racing rules 49 through 54 can now be removed.
Without racing rules 49-54, SNG (Alinghi club) will be breaking with the longstanding history and tradition in yacht racing that prohibited the use of non-manual power. For the first time in the Cup’s history, engines will be permitted to trim the sails, and computers can be used to control and steer the yachts.
This means the next AC 33 regatta could be sailed with Remote Controlled Yachts hang-on I’ve got a couple of those in the Garage some where !!!:p:p:p Hey Claudio come back !!! 
A sad day for the America’s Cup, if they really allow this to happen…
Another hearing has been set for August 10 to allow both sides to extensively argue competing interpretations.
Hi everybody, Probably a little OT :
romantically is difficult to accept this issue and I would suggest to change name and Stop calling “America Cup” and give to these competitions a name more close to “World Technology Sailing Race”
On the other hands and because, is a story evolution since ever between “rich people”, I’m not against the use of electromecanical devices to do the job that a man or several mens cannot do.
Moving a fin from Rx to Sx with 20 tons bulb should not be easy by hands in short time, etc.
Who remember that in 1913 Nicholson mounted the first winches on deck on Shamrock and the AC continued…?
Actually I understand that the sails are very heavy and difficult to hoist, so I will not call to the scandall if an electric motor will be used.
One day a famous yacht builder suggested to do some sort of America Cup with only 2 o 3 mates and a large board plenty of push buttons …Talking with friends I was immaging that an America Cup could be raced via a Radio Control as we do …don’t worry it will come one day…
Cheers
Claudio