I didn't take photo's just a lot of observation.
I was initially intriged by a 26ft telstar trimaran
that I owned some years ago. It had a relatively narrow main hull and would motor
at 10 knots with a 10 hp outboard
. Previously I had a 30 ft monohull
which motored at 6 knots with a 20 hp motor.
I put a 25 hp outboard on the Telstar to see what it would "do" and I got 15 knots. I then went and bought a 35 hp outboard and mounted it on the Telstar, however at 16 knots a bow wave started to form and we started climbing uphill . never got any more than 16 knots.
But it all made me think,why?
Nowdays it is well known particularly on commercial catamaran
ferries that a 16-1 length to beam produces NO bow wave. I went on one last week and we were doing 30 knots, no planning and no bow wave.
16-1 is not suitable for boats under 150 ft long.
I started experimenting with 15 ft plywood
prototypes, in all, I built five.
I found that if the angle of entry at the bow was small and you continued back (wedge shaped) with that same angle NO turbulence (eddys) was produced along the sides of the hull.
It is the friction or turbulence which produces the bow wave. I kept experimenting until I found the best angle of entry.
After that it was a case of making that concept
into a practical boat.
With my design the hull is immersed at all times. Particularly the bow. The stern has large trim tabs to keep the bow submersed most of the time.
The sides of the hull are also vertical, which reduces spray, the bow is longer than "normal" for increased buoyancy.
IT IS NOT THE INCREASED WETTED SURFACE THAT SLOWS DOWN "OVERLOADED" MULTIHULLS.
I have proved that in tests.
It is the wider beam of the immersed hull producing the increased turbulence associated with the formation of a bow wave at a lower speed
YES, increased wetted surface plays a part in this speed reduction but it is not the main factor.
It is easy to prove, because it is speed related.