Bruno est une mine d'information à ce sujet, mais comme il est à l'autre de bout du monde...
Moi je suis très branché "virures"
On en a déjà un peu discuté.
En fait sous le terme de virures on parle de 2 choses différentes , les spray rails (déflecteurs) et les lifting strakes (virures sur l'arrières qui ont un effet dynamique), les secondes sont dans le prolongement des premières mais leurs rôles sont très différents.
http://www.aeromarineresearch.com/publications/PBR_feb2015.htmlsur les spray rail il y a des choses concrètes.
" 5) FEATURE: "Don't Spray! - Spray Rail Design for Performance Boats"
Many performance hull designs – on both tunnels and vee hulls - have functioning spray rails incorporated to reduce drag from exaggerated wetted surfaces. Some of the spray rails can be seen to do an excellent job of this, and others just don’t seem to perform their intended function very well at all.
Then there are Lifting strakes – these are different from spray rails in that, besides deflecting some water and spray from the hull, they are also intended to provide dynamic lift to help lift the hull higher out of the water. That is not the intention of spray rails, which are only designed to deflect spray - not to provide any dynamic lift. [More on lifting strakes another day.] Spray rails are also called ‘whisker spray deflectors”, and are shown to reduce hydrodynamic drag.
It is worth having a quick look at the technical keys to spray rail design that we have available to us – if we want to implement a spray rail function to our performance planing hull design, we may as well try to do it as efficiently as possible.
Whisker Spray Drag - The hydrodynamic drag of any design of planing hull includes mostly viscous (friction) drag and pressure drag components of the planing bottom surfaces. These drag components are mostly from the primary lifting area of the hull, aft of what’s called the “stagnation line”. There is also another type of drag in the “whisker spray region” which is located forward of the stagnation line. We know that for high-speed planing hulls, the whisker spray drag component can be as much as 15% of the total drag. So it is sometimes worth minimizing.
There are engineering methods that can calculate the contribution of whisker spray drag, but for our purposes today, it’s valuable to know that it’s a function of deadrise angle, trim angle, and speed. It’s also valuable to know that we can reduce its effect by properly designed and located Spray Rails.
Location of Spray Rails - E.P. Clement, well-known hydrodynamics expert, has shown that three relatively short, longitudinally staggered deflectors mounted on each side of the planing (bottom) surfaces will effectively deflect approximately 88% of the spray away from the bottom. The transverse locations of the spray strips are approximately 1/4, l/2, and 3/4 of the half beam outboard of the (center) keel. The longitudinal location is such that the aft ends of each strip extend somewhat aft of the stagnation line at each transverse location of the strips.
Since the spray location and orientation always depends on the speed and hull loading, the spray rails will function best at the speed that they’re designed for. So, the designer needs to decide where the best ‘compromise’ location of the spray deflectors will be at the high-speed range of operation. (The spray rail functionality will be different at different speeds of the hull – so location is a compromise, like most all decisions in performance powerboat design!)
The research shows that spray deflectors should be relatively short. If they are so long that they extend aft into the pressure (main hydrodynamic Lifting region) this extra length will have no effect on the spray but will add to the total drag of the hull.
Spray Rail Shape - Other engineering research (Muller-Graf) shows that the best spray rail shape is triangular cross-sectional shape. This ‘optimized’ shape includes a sharp outer edge, which is necessary to facilitate the separation of spray from the hull. Other design features of the spray rail include a bottom angle 8 degrees and a spray rail width 0.5% of the water line length (so an 18ft hull might have a spray deflector width of 1 inch)
So, there are some proven design guidelines for designing effective spray rails. It seems best to try to follow these engineering tips. For example, the spray deflector should not angle “down” – some think to ‘capture’ more water spray. Also, the recommended sharpness of the outer edge of the deflector is important. It has been shown that even a slight rounding of the edge may completely negate the effectiveness of the spray rail. Of course, this desired sharp edge can be tricky to achieve in a hull mould design with integral spray rails. I suppose we can simply add this design ‘compromise’ to all of the decisions that must be considered by designers and builders of "
Sur les lifting strakes ça a l'air beaucoup plus compliqué...Parfois elle ne sont même pas nécessaires quand le pad suffit si j'ai bien compris.
http://www.aeromarineresearch.com/En bas de la page il y a plusieurs articles sur les vee hull et vee pad hull.
Enfin...tout ça est très intéressant mais indigeste et très compliqué.
Il faut , si c'est ton projet , partir d'une carène connue , tu n'arriveras jamais à concevoir une carène performante.
Moi la question que je me pose ; est ce que c'est compliqué à partir d'un bateau existant sans tout démonter de faire un moule?
Sortie d'enfer ce matin , très grosses conditions!
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