A tunnel is a pocket or cut in the center of the hull that runs back to the transom and lower unit. Water is forced in to the tunnel allowing the boat to run shallower and get up in shallower water. It's designed for bay boats that run shallow. Any type of bay boat can have a tunnel.

 

A catamaran is hull is made by creating 2 sponsons (a side hull of sorts), one on each side of the boat. This creates a gap the entire length of the boat, where the tunnel is just at the very back. Some manufactures just cut a section of the V out the entire length of the boat thereby creating the to sponsons.

If a catamaran is done correctly it traps air under the hull and the boat rides softer on the compressed air caught in the center between the sponsons. If done correctly it can handle anything you can throw at it and cushion the ride. If done in correctly, then what you have is a flat bottom boat with 2 side keels and it can make it rougher.

A catamaran generally compresses the water on hole shot and lifts the boat faster than a tunnel hull.

Both generally allow you to run shallower than an ordinary V hull and allow you to get on plane shallower as well.

There are a couple of catamaran hulls that area awesome that I recommend not in any order.
1. The Desperado 22 made in Victoria by Bernies Boats and Motors. Awesome boat, rides more like a 24' boat in 2-3 chop, and still runs in 6 inches. Impressed every time i'm in this boat.

2. Dargel Kat... 23 and 25 Big Boat and can take the rough stuff and the shallow stuff

3. SCB... fastest catamaran PERIOD.. very stable at high speeds... runs shallow.. the 25 wide body and recon models supposedly take the rough stuff pretty well. Other can speak to that...awesome boats in a class of their own... actually all the ones I am mentioning are in a class of their own.

4. Technically a multi hull boat the Shallowsport X3 is awesome. Same... handles the rough and the skinny.

 

I don't mean to highjack your thread bud, but is it true that the Shoalwater 21 Cats draft shallower than the SCB Recons? I guess it could be because the SCB Recons are heavier than the Shoalwater Cats in that they traditionally have heavier motors and more batteries than the the Shoalwater Cats. Does anyone know if there is any truth to that? I have a 2014 Shoalwater 21 Cat and it is a great boat! I have ran it in 5-6 inches of water, it drafts 7-8 inches of water, got up in 10-12 inches of water, and it handles the rough water very well.

I LOVE the SCB Recon and would love to own one some day but I would also want it to be able to draft 7-8 inches and get up in 12 inches or less. Does anyone know about the hole shot and draft of an SCB Recon?

 

Does anyone know about the hole shot and draft of an SCB Recon?

 

There are 2 types of cat hulls. Off shore models and shallow water Bay models. The bay models will run very shallow and take rougher water better than A lot of tunnels.

Shallow or rough water performance is a countiuos spectrum. Big heavy deep v boats run best in rough while flat bottom tunnels run best in shallow. In between you gain one but lose the other. It's a compromise for what works best for you.

Tells us your fishing style and location normally run and we can give you a better idea of what kind of boat to check out.

 

Ok. I am starting to understand a little. I will mainly be fishing freshwater lakes but I also go down to Galveston and East Bay from time to time. I have got into the skinny stuff before in a friends boat but I generally fish reefs and other structures in the deeper bay waters (4-6 feet)

 

Unless you will run in shallow areas every once in awhile then you probably don't need a tunnel or a shallow cat. For me I could never make it without a flat bottom type tunnel like shallow sports or the shallow running cats. But I can not run big Bay areas in windy conditions either. It's a trade off. A cat handles chop much better And is a great shallow water boat.

If you may run. A lot of big open water with some shallow areas the v hull with Tunnel will most likely be your best choice. Something like a blue wave or gulf Coast or Kenner will suit you. there are several tunnel v hulls.

If you never run in less than 2 feet and don't cross any shoals or sand bars then a standard hull will work better. A tunnel will usually rob efficiency and speed.

 

I see a few different descriptions in this thread! Here's my take:

Cats
Shallow-water catamaran - These are the cats mostly talked about in this forum. They are not "true" catamarans, but more like full tunnels on steroids, or an oversized tunnel built into a monohull-type boat. They run very shallow on plane, and have a decent ride in the chop, but they will draft more than a similar monohull when at rest.

True catamaran - These are boats that are comprised of two separate hulls (and often an engine on each hull). They are displacement, or semi-displacement, vessels that can typically draft four feet or more. These cats can offer a comfortable ride in bigger waves and often found offshore. You'll see a lot of these in the South Pacific.

Tunnels
Full-tunnel - these are somewhat similar to the shallow-water cats described above, but also describe the full-tunnel race boats - those little boats that are designed to go over 100mph and do nothing else. Those boats effectively use the ram air lift in the tunnel to help with lessening draft and getting more speed (I really don't think the air lift provides a significant benefit below 50mph or so).

Short or mid-tunnel (sometimes called marsh tunnels) - these are the tunnels common to the flats boats discussed on this forum. They usually stretch across the rear third or half of the boat and receive no air ingestion from the bow. Some of the tunnels may be shorter, maybe one-quarter the length of the boat or less, but I don't think they perform as well. It takes a lot of science and good engineering to make a good tunnel, and I think there remains plenty of room for improvement in this area.

Pocket tunnel - these are really short tunnels found on a few bay boats. I'm not really sure what their advantage is...maybe getting the engine a little shallower when putting around, but their design seems inefficient for good water feed to the prop when on plane. In some cases, they may act like a stepped boat hull to allow the engine to run a little higher, but still an inefficient water feed in my mind.