Pros and cons of a center pod on a tunnel

[Two K's]

I asked this guestion a while ago on OSO. So now now I'll ask here cause it seems that there are more tunnels with center pods on this website than on OSO. What are the pros and cons of a center pod on a tunnel? How are they in rough water? Thanks, Keith

[Bre]

A center pod will have very different results depending on the tunnel hull design, and on the configuration of the pod itself. Pods are designed in all different configurations ..... above the outboard sponsons or below.... shallow deadrise or steep vee. The performance results will depend on the combined design features of the pod and the overall hull configuration.
Without some sort of center pod you would not be able to run a single I/O. That is why you can only run O/B's on the smaller skaters.
In our experiences... a true tunnel... no center pod is a cadilac compared to ours which has a center pod.

[Bre]

Oh.... also the true tunnel we were in was 10 feet bigger than ours LOL.... I am sure that makes a difference.

[Two K's]

Thanks for input Bre. I also think that a center pod helps save the drive from being beat to death. One boat built over here on the east coast[Cobra terminator] that is a true tunnel but isn't as deep as others are mostly set up with single i/o with good results. Usualy 750hp puts them in the low 90's I owned one but mine was a twin set up. their is only two that I know of with twins the rest were single or o/bs These were 30' boats. A real nice boat but real cramped for space, under 8' wide and thats the only reason why I sold it. I want more room for passengers.Which do you think is better for rough water shallow pad or deep pad?

[Daytona19]

A center pod will have very different results depending on the tunnel hull design, and on the configuration of the pod itself. Pods are designed in all different configurations ..... above the outboard sponsons or below.... shallow deadrise or steep vee. The performance results will depend on the combined design features of the pod and the overall hull configuration.
Without some sort of center pod you would not be able to run a single I/O. That is why you can only run O/B's on the smaller skaters.
In our experiences... a true tunnel... no center pod is a cadilac compared to ours which has a center pod.
This statement is true, I have a Daytona 19ft with NO center pod and it rides awesome and is a very DRY ride compared to a center pod design.

[Bre]

Thanks for input Bre. I also think that a center pod helps save the drive from being beat to death. One boat built over here on the east coast[Cobra terminator] that is a true tunnel but isn't as deep as others are mostly set up with single i/o with good results. Usualy 750hp puts them in the low 90's I owned one but mine was a twin set up. their is only two that I know of with twins the rest were single or o/bs These were 30' boats. A real nice boat but real cramped for space, under 8' wide and thats the only reason why I sold it. I want more room for passengers.Which do you think is better for rough water shallow pad or deep pad?
I would have to say that I think shallow would. But don't quote me on it... I have never riden in a boat with a deep one.

[XtrmWakeborder]

con: Having a center pod will get you made fun of by the D row boys
pro: You will fit in with the DCB guys
:argue:

[Keith E. Sayre]

Here at Conquest Boats, you might say that we use a bottom similar to the
Talon bottom. That means that the center sponson is actually a few inches
deeper in the water than the outside two sponsons. Admittedly, the center
sponson will help you "feel" bumps in the water that a true tunnel may have
simply gone over and a true tunnel will be more efficient at speed since it has less drag than a boat like ours with a deep center sponson. But everything
else I can think of about a deep center sponson is smart.
For example, our 28 deckboat planes without the driver losing sight of the
water ahead of him. Most cats plane very slowly. As a matter of fact, if you
read the tests in last Octobers Hot Boat magazine, our 28' Top Cat deckboat with a stock 425 hp 496HO was the fastest boat they tested from zero to
60 mph. Much faster acceleration means you can pull skiers and wakeboarders etc. The center sponson being very deep also allows us to slow our boat down to 19 mph without losing plane. A cat without it would
never be able to go that slow without sinking back into the water. Our boat
can do that with any engine package that we sell with NO trim tabs and NO
dual prop drives. As a matter of fact, if you put a big elephant eared prop on
about 4" smaller in pitch, I think you could get it to crawl at 15 mph on plane.
PORPOISING---almost all cats porpoise from 30 to 50 or 55 mph??? Our doesn't. As a matter of fact, you can't make it porpoise even if you try.
One of our competitors in town that bought their bottom mold from us has
apparently moved his "X" dimension up a bit in an attempt to get more top end speed and now has to sell his boats with trim tabs. We don't use them
ever and it never porpoises. TURNING and LEANING the wrong way. Our boat
never hooks and never turns violently and never leans "out" or the wrong way
in a turn. Most cats do all of those things. Our boat turns harder than any boat that I've ever been in except my Schiada. And it feels just like a v-bottom and it leans the right direction!
In the final analysis, I think that it's fair to say that a true tunnel will go faster than one with a deep center sponson and will probably feel smoother
in chop, but the "deep" center sponson cats do almost everything else better.
Just my two cents worth.
Keith Sayre
Conquest Boats

[gmocnik]

kieth..
why does a deeper center pod (ie. conquest bottom) not porpoise. i understand the dynamics between hydraulic lift and aerodynamic lift at the 50-70 mph range. varying x dimensions, prop rake (bow lift vs. stern lift) and the boats basic hull design all impact the boats tendency to porpoise at certain speed.
it seems to me that a true cat (i.e. skater, etc.) tends to porpoise more than a tunnel. my single step 25 daytona jumps around at exactly 61 mph and goes away at 74 mph. i have had to cheat and use tabs..still hops a bit and i am trying some other things next season to stop it.. it really does drive you nuts when these things jump around....
just curious as to your theory regarding the deeper center pod..
thanks
gary

[Charley]

ideal "compression" is a good thing :D
and thats all I'm gonna say about that

[Havasu Hangin']

ideal "compression" is a good thing :D
and thats all I'm gonna say about that
Yes. And a centerpod probably creates a more consistant compression (lift).
and thats all I'm gonna say about that
:D

[Two K's]

XtrmWakeborder,I know what you mean. I mentioned my interest in buying a tunnel with a pod on OSO forum and got a little beat up. :squiggle: I said that I wanted to go to a single engine with a pod because I think you get a better cabin and they beat me up some more :confused: :D Keith, thanks for so much info. I am willing to give up some speed for room and I do want to stay with a tunnel but I also use my boats in big water [long island bays, atlantic ocean on good days and hudson river] so I have to look at ones with a good angle on sponsons?

[Towndrunk]

The center sponson also has a quicker hole shot than the true tunnel but the true tunnel will be faster on top. At least this is true in OB racing.
TD

[Thunderbutt]

Keith, as you know, I bought the Warlock deckboat. Having never ridden in a tunnel boat with a center pod I have no judgement. How would you compair the Warlock with the Conquest in turning,planing & speed. With the trim set right I haven't notice any porpoising. This boat runs right at 60 mph,of which I'm going to change this winter.
Jim

[welk2party]

I think Froggystlye would have some good answers on this subject.

[Keith E. Sayre]

In response to gmocniks question about why---I really can't explain it at least not in writing and have it make any sense. I had Steve Donohue from
Merc explain it once. He's the smartest guy in the world when it comes to
bottoms and water dynamics and all that technical stuff. He made it sound so simple but it's not. Sorry I can't help you with that one.
Thunderbutt--how's the Warlock doing? Hope that all is well. I really can't
say. That Warlock boat is huge. Call me at the office at 928-680-1400 and I'll give you the guys cell number that you bought the Warlock from. He now has a new Conquest with a 525 in it. He would be best qualified to answer
that one. Good luck!
Towndrunk, Havasu Hangin and CharleyP: Yes, Yes and Yes!
Keith Sayre
Conquest Boats

[Havasu Hangin']

In response to gmocniks question about why---I really can't explain it at least not in writing and have it make any sense.
I'll take a guess, Keith.
Is it because a true tunnel has a tougher time finding a balance between lift (fron air pressure) and weight?
And because a centerpod uses the water to lift, which is more stable?
I think most people call a hop "porpoise". Perhaps it really is not a porpoise...it's just that the air has not packed enough to carry the nose?
Alright...I lied. :messedup:

[Blingette]

Let's just leave it at this... East coast----West coast. :wink:

[phebus]

To take this design issue a little further, why do some cats have a notch at the transom, while others do not? It seems like the one's with a notch work better with tabs, but that would seem to negate the notch.
I have read that the bottoms without a notch get on plane quicker, and hold a plane at a lower speed. Also. it seems the longer running surface would help in the rough stuff, so guess would be that the notch helps with water flow to the drive.
Anyone?????????

[TimeToBurn]

First off, the deeper the tunnel the more air entrapment which provides the boat with more lift, reducing the amount of friction... giving the boat more speed.
However, this reduces the level of control and stability of the boat. The boat will have a tendancy to skip across the water moving side to side, actually beginning to favor one or the other sponson, causing the boat to drift sideways, instead of riding in a smooth, srtaight line. In the end this could be dangerous.
The issue with the center sponson... it might decresase your maximum potiential speed. Some say it don't. However, the boat will have more control, gving a straighter ride, and more versatility in steering. The boat will be able to turn faster and sharper. Lastly, it will plan at a lower speed. Where as if you don't have a center sponson it might take a lot more speed to get the same lift.
The point being, it is important to understand the quality of the manufactor and design of hull. What is it you want to accomplish due to the type of water and ride? For example, narrow channel or river... tight turning, faster speeds out of the hole.

[Huckleberry]

At top end aren't MOST center pods out of , or nearly out of the water anyway. How much spped do you really give up in exchange for the added stability? Seems like a fair trade off to me.

[Havasu Hangin']

At top end aren't MOST center pods out of , or nearly out of the water anyway. How much spped do you really give up in exchange for the added stability?
Not when you land on them...

[Two K's]

Time to Burn, My tunnel boat did have a tendency to roll side to side at about 60 mph. the slightest turn ot the wheel in the opposite direction would help stop it. Any faster would cure the problem , but it was an uneasy feeling.I thought that it was because the boat was a twin engine setup and the boat was designed for a single engine. The boat was about 7'9" wide. Full open the boat handled great but I think if the boat was a single it wouldn't of had that problem. I also think that with the loss of weight from the other big block would have let the tunnel work better and maybe speed loss wouldn't be to drastic. I was going to change it to a single this winter but sold it instead to a guy who is also going to change it to a single [I got to keep one engine drive setup] So now I'm trying to get another tunnel that has alot of room and a cabin and I think center pod tunnels give you a more accessable cabin which I need because weather here in new york changes fast and a cabin keeps my family out there on the water longer Thank's all for so much info.

[Thunderballs]

Bre- Good point! It's nice to have something to mount the gimbal to on a I/O.
If we go back to the beginning: Eliminator, Sleek, and others here in CA. built these first boats as jet's. The center tunnel had to be deeper than the outer sponsons to keep the pump loaded. Same thing is true for the 21 Daytona, Jr. Exective, and others. As the pump fell from grace and the boats got bigger the center sponson began to rise. Today the center sponson really allows mounting of the stern drive on single engine aplications. It also lends additional strength against twisting, the vertical sides acting like stringers. On a different note, the amount of air that a cat "pac's" has to do more with the size of the opening and the width and depth of the tunnel. Mod V.P. boats used to have a center. Now if you look at pic's of formula 1 they are almost true cats, running outboards. You don't have to have a center sponson for i/o's, I drove a 22 Skater with a single 225 outboard.
The bottom of the Conquest deck is a copy of the 25 Talon. When the first 26ft AO (copy of the Talon) hit Havasu, the bottom was a hit with Conquest and here's why. The deeper center pod carries a full keel. The boat thinks it's a "V" bottom with training wheels. It leans into the turn instead of out like a true cat. Because of the added static bouyancy of the center pod, you can load it up with people and gear without the boat sinking deeper in the water than a two sponson cat. Because of the added lift of the center pod the boats carries more weight at a higher speed than without. Add to that the air pack at speed helping to lift the hull and increase speed and it was a no brainer! That's why Magic, Commander, and others use the same bottom. The reason that AO, Firehawk, Howard, and Magic use the bottom on their pleasure cat is simple. IT TURNS! The deeper center sponson alows the boat to turn without the usual outside lean and nasty hook thats possible with the "true cat". It won't be as fast as a true cat but it handles sooo much better!! But let's give credit where it due. Gary Armington and his dad at Talon! By the way, the 377 is available from Hustler with or without the center sponson! :rollside:

[Charley]

First off, the deeper the tunnel the more air entrapment which provides the boat with more lift, reducing the amount of friction... giving the boat more speed.
Sorry TTB, I have to disagree... I think to get lift you need the mouth of the boat to gather more air and shovel it out the smaller exit ... It's effectively a wing and it creates Compression.... thats what lifts a boat out of the water not a deeper tunnel ....tunnel's depth means nothing without a properly designed mouth to gather more air and a "successful ratio" of mouth to exit... You really dont want to much lift or too little.... good manners is key in a ride as sketchy as a tunnelboat!! Too much mouth and too small of an exit can make a boat stern lift and ass walk, even drive the nose down .... Some of you may even be able to think of a good example of such a mixture ;)
No offense meant TTB.... just my opinion

[HTM-NY]

Did you sell your boat to a guy up on the St. Lawrence river near Massena, N.Y.?

[RiverOtter]

XtrmWakeborder,I know what you mean. I mentioned my interest in buying a tunnel with a pod on OSO forum and got a little beat up. :squiggle: I said that I wanted to go to a single engine with a pod because I think you get a better cabin and they beat me up some more :confused: :D Keith, thanks for so much info. I am willing to give up some speed for room and I do want to stay with a tunnel but I also use my boats in big water [long island bays, atlantic ocean on good days and hudson river] so I have to look at ones with a good angle on sponsons?
Whatever you do... Never, (let me repeat) NEVER ask about a windsheild. It will get ugly... :squiggle: :D

[TimeToBurn]

Sorry TTB, I have to disagree... I think to get lift you need the mouth of the boat to gather more air and shovel it out the smaller exit ... It's effectively a wing and it creates Compression.... thats what lifts a boat out of the water not a deeper tunnel ....tunnel's depth means nothing without a properly designed mouth to gather more air and a "successful ratio" of mouth to exit... You really dont want to much lift or too little.... good manners is key in a ride as sketchy as a tunnelboat!! Too much mouth and too small of an exit can make a boat stern lift and ass walk, even drive the nose down .... Some of you may even be able to think of a good example of such a mixture ;)
No offense meant TTB.... just my opinion
Sorry Charley... (in my opinion) with all due respect... don't get the tunnel and sponson confused. I said a deeper tunnel! Nothing to do with a sponson set up. For example, a Skater, MTI, Callan, Nor-tech are tunnels. DCB, Eliminator, Ultra, Commander, are cats(center sponson for the most part). My point was to point out their styles for rides. CATs and TUNNELs have very destictive features that impact the way in which they ride the water. In a Tunnel, it is always going to lean or skip into the outside sponson on a corner. However, a well design CAT will pivot or stay flat in a corner. For example, a 30 Daytona ran 152 MPH at the Bridge to Bridge run in Sacramento (which is a narrow course, with a tight turn).. the center sponson gave the boat better cornering ability to not loose speed while cornering.
Rock NO ROLL!

[Two K's]

HTM-NY' Yes I think that was where he came from. A Nice guy. The boats name was look up. Im interested in knowing how it performs as a single when it's done. Boy that boat was built strong Totally cored. It didn't shake or rattel in the rough stuff. If I didn't need more room I would have kept it and did the conversion myself. We have a couple more of them around here on the island that have built up single engines that are in the mid 90's and they are not super charged. That tunnel has a true tunnel. tunnel got smaller at the stern and wasn't deep like skaters though. I liked that boat alot That boat company [cobra boats in new jersy] now mostly builds center console fishing cats. Maybe someone can enlighten me on something I heard about tunnels with shallow pod. I was told once that when they are up and going and the center pod is out of the water. When it does occasionally enter the water it feels like someone is tapping on brakes. Is this true or not true. I have never been in a tunnel with a pod. If tunnels with a pod are better handling over a true tunnel than maybe the insurance companys should know this and give better rates on them :D :D :D

[Two K's]

RiverOtter, No windsheild!! :idea: OK, how about a radar arch :sqeyes: :D

[HTM-NY]

The guy has the whole boat stripped, the old hole's filled and the engine sitting in the center. It'll be all new when he gets done.
As far as the center pod issue I agree with what was posted earlier. The center pod will give you a bumpier ride at slower speeds and the rougher stuff. I know I can slow down to about 15 mph and stay on plane. I'm not sure if this has anything to do with the center pod but my HTM(w/center pod) turns on a dime and leans slightly into the turn.

[Two K's]

Thanks HTM-NY for info on my cobra and info on center pods. Thats great to hear he has done that much already. That boat will do very well as a single. I would love to see when it's done.

[RiverOtter]

RiverOtter, No windsheild!! :idea: OK, how about a radar arch :sqeyes: :D
Now you're talkin. With a whole bunch of crap on top of it :D

[TOBTEK]

http://www.***boat.com/image_center/data/500/1352000_MACH_26_2.JPG
center pod's RULE :notam:

[Thunderballs]

Hey guy's,
If the center pod of your "CAT" is higher than the outer sponsons when the boat is on plane than you are driving a true "CAT". Only when the center pod is even with or deeper than the outer sponsons, can you call it a "modified cat". Thats why the AO/Talon turns so well. The center pod protects the inside sponson from "seeing" the on-rushing water and the keel acts as a rudder keeping the boat from hooking. :squiggle: