hull with tunnel

[Jasper_ghost]

I just found a pic of a Penn Yan hull with a tunnel. This 33ft hull should have a max speed of 28knot. But what is the advantage of this tunnel. Lower planning speed or better stability? or maybe better fuel efficiency...

[Fanie]

Shorter turn radius at speed, less choppy ride maybe

[Gilbert]

My guess is that the hull was intended for two motors with the props in the tunnels and someone put a single motor in instead. The virtue of the tunnels with twin motors would have been shallow draft, which it certainly doesn't have with a single.

[tom28571]

What Gilbert said. The tunnels were for shallow draft originally. It would be better if the tunnels were filled in now.

[Jasper_ghost]

Thanks. I was just thinking if the tunnel horisontal ared had the same function as a delta pad but with lift seperated from center to give better stability.

Another Q.
This 33ft boat weigth approx 6000kg/13000 pound.
What will be the most economic speed (engine is a Volvo Penta 370hp TAMD63 diesel). Any good guidelines for how to calculate a fuel consumption vs speed.

[FAST FRED]

What will be the most economic speed (engine is a Volvo Penta 370hp TAMD63 diesel).

High idle , 800 rpm or so is best for range.

After that you are traiding speed for distance.

Next "best " is usually just above plaining speed , but it will cost at least 3 to 5X as much per mile in fuel.

FF

[Village_Idiot]

With regard to the tunnels:

Tunnels are basically good for shallow draft only. If you do not need shallow draft, avoid the tunnels as they generally hurt all-around performance, except in the rare case of high-performance racing tunnels. With a tunnel, you lose speed, agility and reverse thrust.


With regard to the tunnels, especially on planing boats:

Tunnel boats, especially pocket tunnels, can be a huge pain to set up correctly. Once they are dialed in, they are a thing of beauty with regards to their focused performance potential (being able to run in extremely shallow water). There are 20-foot-plus, 2000-pound-plus tunnel hull boats out there with motors up to 200hp and beyond that can run in less than ten inches of water, some in quite a bit less.