hull with tunnel

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...

 

Shorter turn radius at speed, less choppy ride maybe

 

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.

 

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

 

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.

 

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

 

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.