Tunnel Hulls, what's the pros and cons?:

[TPC]

Jas Bordsmnjm is sporting a tunnel on his Stoker.

I've notice them at the boat show on several performance lines over the years and was wondering what are the plusses and minus of them?

Will it bone you on your insurance as well?

 

[Tom Brown]

Many people hold that tunnels are more efficient. I don't share that view entirely but understand where it comes from and acknowledge that it generally holds some water.

Many of the smaller v-hulls pack air also and at 100+ mph, the hull to water contact is approaching zero with a number of different hull styles. As the boats get heavier, tunnels have more of an advantage here.

The real advantage to the tunnel is their inherent stability. Often called 'training wheels', small tunnels can fly at 100+ mph with little fear of rolling. The main fear with a tunnel is blowing over backwards. This can happen for a number of reasons. Anything that causes an increase in hull pitch is a potential blow over threat if the speed is significant.

Tunnel owners often run stern lifting props, such as low rake cleavers, to hold the stern of the boat in the air. The bow will hold itself up once it has enough speed to fly as the body of the hull forms a wing. If you're running along really fast and get out of the throttle quickly, the stern will fall causing the boat to take on increased pitch and possibly blow over backwards. It's tough to learn not to get out of the throttle too quickly when something scares you and it could be a potentially deadly mistake.

Still, tunnel hulls are the best thing going for low drag and very high speed. V-hulls can certainly blow over backwards too.

If you want to do 145 mph in a 20' boat, you have to have a tunnel. It also helps to have balls of steel and a death wish.

 

[OCMerrill]

Our current Lavey is my first tunnel hull boat. After nearly 5 years with it here is what I have noticed.

More speed with Less HP
Turn flatter and nearly on rails (fun)
Faster you go better the ride - Pack some air
Very easy to trailer. We can be on in two min's. Like tracks to guide you right up.


Down side

Slower speeds and rough water suck. Mid day Sat. on parker we don't even bother. Lakes...not this hull.
Our Lavey is very bow down at speeds. We have to pay attention to boat wakes to avoid stuffing the nose. Because of the quirk I will not let just anyone drive.

This is partly because we have a stern drive in a OD design hull and it is harder to PU the nose without packing some air. Heavy to far forward.

With Alum heads and a mild cam on a stock SBC merc mag I can reach 72 mph. I can also run 3 days on 40 gallons of gas and that is driving it.

Would I buy another...Only as a second boat.

 

[BadBlown572]

Tunnel hulls are great for a lot of things. It allows the air to get under the boat and the boat to get up on top of the water versus plow through the water. The pros are that they are much faster, power for power, than a typical V-bottom. Depending on the tunnel hull, they can also run better in moderate chop.

A Mod VP (like a Stoker, Baker, Sleek) etc. is a combination of a V-bottom and a tunnel hull. Typically the center pod is lower than the outside sponsons. This allows them to turn very well. A "Cat" typically has the center sponson up higher than the outside sponsons. Cats typically do not like to turn nearly as well as a V bottom or a Mod VP.

The trade offs are insurance, and that they are not nearly as forgiving as a V bottom. As soon as an insurance company hears that it is a tunnel hull, the premium doubles or tripples (typically). Another trade off is that in REAL big water, cats or tunnels don't like to plow through it.

 

[OCMerrill]

Many people hold that tunnels are more efficient. I don't share that view entirely but understand where it comes from and acknowledge that it generally holds some water.

Many of the smaller v-hulls pack air also and at 100+ mph, the hull to water contact is approaching zero with a number of different hull styles. As the boats get heavier, tunnels have more of an advantage here.

The real advantage to the tunnel is their inherent stability. Often called 'training wheels', small tunnels can fly at 100+ mph with little fear of rolling. The main fear with a tunnel is blowing over backwards. This can happen for a number of reasons. Anything that causes an increase in hull pitch is a potential blow over threat if the speed is significant.

Tunnel owners often run stern lifting props, such as low rake cleavers, to hold the stern of the boat in the air. The bow will hold itself up once it has enough speed to fly as the body of the hull forms a wing. If you're running along really fast and get out of the throttle quickly, the stern will fall causing the boat to take on increased pitch and possibly blow over backwards. It's tough to learn not to get out of the throttle too quickly when something scares you and it could be a potentially deadly mistake.

Still, tunnel hulls are the best thing going for low drag and very high speed. V-hulls can certainly blow over backwards too.

If you want to do 145 mph in a 20' boat, you have to have a tunnel. It also helps to have balls of steel and a death wish.

Yep. That is it right there. Nice post.


What can Brown do for you...just about everything.

 

[TPC]

Yep. That is it right there. Nice post.


What can Brown do for you...just about everything.

Yeah, great takes.
We're in school in this thread.

 

[OCMerrill]

Yeah, great takes.
We're in school in this thread.

Your trying to spend some money? Now you want a vette for the water LOL!


Danny described the Mod VP nicely. Ours is a Mod VP. I failed to mention that above. Not may mfgs to chose from with this hull type of boat.