1)Planing ,Stepped Cats/ 2)new design cat

1)Anyone interested in the design theory behind Yves Parlier’s 60’ Open 60 cat with it’s stepped planing hulls and twin rigs should get the May 2004 issue of Seahorse for a detailed article pgs. 30-35.
Interestingly, they made extensive use of rc models(the largest: 2.4m–94"-7.8’) to refine the rig position as well as the daggerboard position. They also tested a 25’ sailing model.
It will be interesting to see if anyone builds a model cat for competition using the planing hull concept.One thing they don’t go into detail on but mention in passing is the idea of variable geometry being used to eliminate the low speed negative effects of the steps; this might help make the concept more appealing from an rc perspective.
2) Another interesting cat design on page 46 of the same Seahorse: designed for Lake racing in Europe this boat has a center “hull” that does’nt touch the water but that is designed to take the fore an aft loads. The asy pole is fixed to the bow of this “hull” and the stern is attached to the rear cross arm. For rc models it is a good looking way to incorporate a center nacelle for radio control gear instead of putting it all in the hulls…

Doug Lord
–High Technology Sailing/Racing

if you are interested in the new parlier’s boat this is the official site


and my first drawings

and sorry for my bad english!

Very Interesting! Are you going to use a variable geometry system to introduce the step or just not use a step?
I’d love to hear more details of your design!
I’ve done some study that seems to show that a tri of 18’ in length(16-18 beam) using a foil(with wand altitude control) on the daggerboard and one on the rudder with stepped planing hulls in place of a “normal” ama could be extremely fast.
The main hydrofoil would lift only in lower wind ranges and would hold the main hull DOWN in medium to higher wind ranges. The t-foil rudder would provide pitch stability combined with crew weight.Crew weight would provide a substantial portion of Righting Moment so the planing hulls would be quite small…Very much inspired by Parlier’s boat!
Let’s hear your idea’s!

Doug Lord
–High Technology Sailing/Racing

well it’s my first design and J decided to “copy” the Hydraplaneur of Parlier
the step is not on the drawings because it was more easy not to draw it !! and for the real cat, they put the step a the end…

J have found very interesting informations in the R/C hydroplanes techniques

J will be at the first ORMA grand prix of la trinit? sur mer to see more details of this fabulous new boat (qualified for the Transat too)

it will be fun to draw a trimaran, because j think it’s more stable than a cat !! if you have any idea or plans !! [:-bulb]
and j don’t know if the fact to bend (to bow??) the two masts if efficient for stability ???

anthony from france

I must admit to be obsessed with this boat! What program have you done your hull drawings in? Looks cool!

Luff 'em & leave 'em.

Anthony, I envy you getting to see that boat first hand! How do you think it will do against the ORMA tri’s?
I’m doing a lot of research as time permits on stepped hulls so if you find any good sites please post them. I’ve found boatdesign.net and am looking often. Also any books you find–please post.
Thanks for the pictures!
I’m really convinced that on a tri the combination of planing hulls where the amas are and a main hull with hydrofoils(negative lift at highest speed!) can lead to not only high speed in an 18’(5.49m) boat but also greater control.
My first X3 retractable hydrofoil is almost done and I may use it to experiment with planing hulls on a model though I do not have high hopes for success there but MAYBE!
Interested in your ideas and pictures!

Anthony, I don’t know if this is what you were refering to or not but the two masts on the hydraplaneur lean in toward the center in order to reduce the weight of the upper connecting beam according to Seahorse mag…

Doug Lord
–High Technology Sailing/Racing

j use the demo of naval designer and J make screen shot with a normal drawing program…


and lot of time…


How do you think it will do against the ORMA tri’s?

Parlier said that he don’t really know what happened against tri. On Grand Prix, the cat is not as good as tri against the wind and there is a lot of manoeuvre (??) to do, so ???
but he is very confident for the Transat !!

J hope you can understand me … it’s hard to find the technicals words

I’m doing a lot of research as time permits on stepped hulls so if you find any good sites please post them

very difficult to find informations
two directions : the plane
http://perso.wanadoo.fr/j.s/hydravions/index2.htmin french about float conception of hydroplane
and the motor boat
in russia !!!

and j have download all the photos j have found about Parlier’s cata Mediatis !!!

in yellow first model hulls for hydrodynamic tests)

Thanks again for the information and pictures! If I read the article in Seahorse correctly the hull shape of the final boat was close to the model on the left side of the picture; is that right?

Doug Lord
–High Technology Sailing/Racing

exactly ![:D]