Rg65 narrow deck

After the “Narrow Deck” design of the Class M Esterel-Ruby, I did the same for an RG65.
The anticipated drawing is here attached.
Due to the low displacement below 1000g, the construction requires good practice.
Two 1/2 masters are needed. Temporaly assembled during manual fairing.
The hull fbg lamination will be split into 2 halves and bonded along the centerline.


Aiming to reduce further the construction weight and introducing some looking style, I have modified, for those who like it, the transom with a continuous slope.
Printable shadows with PDF file on request.

Claudio…the master…

neat looking boat claudio…

Oh God! (=Claudio :smiley: ) Now I have to build a new hull!!! This looks impressive. It’s like the one I built (Esteler65h+rounded bottom), but narrower. Just some questions for you, Claudio:

  1. DSPL=894cm3 minus 400gr construction leaves only ~500gr for bulb, which seems a bit too little for me. In my opinion with a 600gr bulb RG65 boats sail better.
  2. This desing, and the Esterel65h have part of the bow submerged. Is this on purpose? In my mind the bow should rest a little bit over waterline to make turns easier…
  3. Your designs call for a 30cm draft. I am building using a 37-40cm draft. What is your reasoning on this?

I am in now way a designer, nor I understand the math behind hull design… These are just some thoughts… Anyway, I think a boat along these same liunes, designed for a DSPL of 1050gr would be perfect for me…

PD: what do you think of my version of your Esterel65h?

this design is aiming to reduce as much as possible the construction weights as such to dedicate more grams to the bulb.
This is why I initially introduced the narrow deck, now fews cm² more are removed from rear of the hull with a declined and rounded transom.

  1. the Total DSPL is 979cm3 (894 + appendix) - the expert modeler can make it for 300-350g and at fortiori with this design. 979 - 350 = 629g for the bulb
  2. Yes it is partially summersed in order to have a better penetration. With the bow above water, the LWL get shorter and the critical speed also. (theory)
  3. Yes 30cm Fin. More it is possible within the weight allocated to the Fin. Larger Fin = larger Wet area. 40cm is too much in my opinion, better to use lower mast with the same sail area of 2250cm².
    You version is in line with my thinking !

Hi Claudio
what is the CP measurement on the drawings?

It is marked on the drawings, see previous posts

I see cp under the graph on the left and on the list on the right.
Sorry please define “CP”

You may read that : http://www.sailboat-cruising.com/prismatic-coefficient.html

You may read that : http://www.sailboat-cruising.com/prismatic-coefficient.html
Further check the Curve of areas , all is there !!!

After presentation of the RG65 Narrow Deck, here a small variant playing with PC.

They look almost the same but they are not !

Often the right choice may help !

Here two hulls, one with Low Prismatic Coefficient adapted to low wind conditions and one with High Prismatic Coefficient for higher wind conditions.
Ideally when preparing for a race, would be profitable to dispose of one or the other before start, all the rest being the same. Of course smaller rig should be used when the wind force is increasing.


I didnt see this on the RG65.fr site can I add this to the new rg65USA site I am building ? Is the hull name “Narrow Deck”

Thanks for you work on this!


The original RG65 name is “ESTEREL”

The specific main characteristic of the Esterel project is the ‘Narrow Deck’ .

From now are available two basic plans, one with Low Prismatic Coefficient and one with High Prismatic Coefficient.

One could consider today as “ESTEREL LP” and “ESTEREL HP”

Are just coming out from my pen and are simple suggestions on how to play with PC !!

Not escluded minor DSPL changes and issue of shadow and Sail Plan sets

No restriction to publish them at the contrary !


Once being operative with a new lab, I will build both models to verify their performances.

This will allow to confirm the theory about !

While experimenting, it is also planned to use, as for the Delta Rig, a Dual-Jib Rig and see what happen !!

This configuration exist already with the Cruising Ship “Club Med” that uses also Radial booms.


HI Claudio:

The reason for using a number of short masts against one higher mast is to heel less, I think. But I would think having 2 airfoils is difficult to design. Think turbulence and the effect of one sail on the other.

In airplanes they discarded bi- and triplanes years ago! I understand having a narrow slot between main and jib is better than two separate sails. But the two-jib concept does not make use of this.

Can you please explain your rationale?


So two jibs in line (in a row) at one mast?

In my opinion bi and triplane wings are not used since airplanes nowdays are faster.
The wing Lift force is directly proportional to the Speed, a smaller wing surface produces the lifting force you need if the speed is there. Bi and tri plane can fly at low speed since their wings have large surfaces in total. Similar surface on a single wing could not be achieved due to mechanical limitations.
Modern engines increased the speed of airplanes with consequent reduction of wing surfaces !

The rationale behind the dual jib is due to the avoidance of the Mast turbulences and drag and therefore this setting should produces more lifting power with the same surface.

You should also ask the Club Med designers !!


I would like to experiment again the dual stay and dual jib with radial booms !
See image.
The central set is probably the heaviest and disregarded while the first to the left offer a much lower CE.
Would be nice to obtain a butterfly configuration when running !

That yellow example looks more likely to work. More sail area into a smaller geometry, and a slot you could work with!

Have you seen this?


Notice that I’m the first having introduced the Delta Rig (CD-CAT) in 2003 with a Class M.: http://www.rcsailing.net/forum1/showthread.php?5471-Delta-rig/page8
One example here on RG65, 16" almost without wind, the skipper is 8 years old : http://youtu.be/9lyWYXwoGUM?list=UU7laodmU4RCck0owTn2uXjA