Originally Posted by leviterande
wowo, so the human powered boat is as fast as a 13 hp!!,
I think that the human powered is ultra efficient (1hp) because of using a hydrofoil. Also I think that the weight of the boat will be more like 200 kg
is there no other hull design that is more efficient than "plan hull" and less complex than hydrofoil?
thanx for the help
To do 20kts with a planing hull you need about 4kW with the best design and minimum weight for one person driving a water prop.
With an airboat you would need to swing a larger prop than you propose to get the best from the engine. The structure to support this also adds weight. There are stability issues as well because the thrust is generated a long way above the resistance.
Building to keep total weight under 200kg will take careful design. For safety reasons powered air props on boats are guarded. That adds weight and a little extra drag.
Decavitator was an optimised design for its intended purpose. If you want to go as fats as you can on water with 13HP then it will be faster than 20kts - maybe 40kts. However that will take considerable design effort and you will have a boat that is impractical for anything other than tearing down a straight course in good weather.
You could target 30kts with 13HP using thuoghtful design. It would be quite narrow. About 1.2m beam. So you need to keep the weight low. The deck would need to be aerodynamic to keep windage low. The faster you go the better efficiency from the relatively small air prop. A 2m prop will get 71%. If you use a shroud for the guard then the efficiency gain would offset the drag on the guard.
So it becomes a design challenge. Not something you throw together over the weekend. It becomes more specialised for just going fast for the installed power.