I agree hull speed
for a displacement
boat this length is 8.5 knots, but it shouldn't take 60 hp to get there in a 5 tonne boat 8 ft wide.
I must be developing a lot of drag somewhere because of the extra weight in the stern.
I am trying to do something different and so far i am not succeeding, OK.
At the moment (in boating
design) the only way of going faster, is by using a Planeing hull
at a minimum of 50hp per tonne or two(or three) narrow hulls (the 16-1 rule) which is used in commercial catamaran
ferries but is not suitable for craft in the 40-50 ft range.
I built 5 prototypes developing this triangular hull
with a very narrow angle of entry and a flat wide stern. It worked in the prototypes and I have to sort out why it doesn't work at the moment.
It shouldn't take 60 hp to get there in a 5 tonne boat 8 ft wide.?????
I had a 25 ft Catalina
boat 2.5 ton and with a 10 hp Honda
we easily got a displacement
speed 6-7 knots.
What causes a displacement boat at 40 ft lwl to only do 8.5 knots is the development of a bow wave at that speed which forces the bow of the boat to lift
and the stern drops(going uphill)
Well my boat is NOT doing that. There is no sign of a bow wave at 8.5 knots.
I have a rudder
made but it is not installed yet.
I appreciate any comments or advise because if I can get this right and be able to get 15 kots (say) out of a 40 ft hull with reasonably low power
it will be a significant achievement for a cruising boat.
If I thought that 60 hp was needed to get 8.5 knots in a 40 ft narrow displacement boat I would accept the fact. However at this point I feel that there are many questions unanswered.