Why do Cats act Like dolphins?

[Charley]

who knows the REAL reason......whats the porpoise?? I stated my purely hypothetical reason..... how about the REAL reason??anyone?

[Havasu Hangin']

I could tell ya...but I'd have to kill ya.
So what's new, Charley?

[Charley]

Oh ya know
Family,work,war and Pulling my hair out waiting to get in the sun :D how about you mr tugboat?

[Havasu Hangin']

Charley:
how about you mr tugboat? Mr. Tugboat and I still aren't on speaking terms...although that may change next week- I think I found a new outdrive.
BTW, I always thought cats porpoise because of an unbalanced lift situation- there is enough air being forced in the tunnel to lift, but not enough to hold it, so the air releases, and the cycle starts all over again.
If you get going fast enough, the air packs the front of the tunnel with enough pressure to prevent it from releasing.
Of course I could be wrong...
I heard a rumor that you want to run in the Spring Heatwave....better get some seat time!

[Donnie]

I think its the beer rolling to and fro in the cooler that upsets the balance of the boat :D eek!

[blown23vee]

Hey Donnie! That trip to Larry's just wasn't the
same without you snoring in the back seat!

[Havasu Hangin']

Donnie:
I think its the beer rolling to and fro in the cooler that upsets the balance of the boat...Sounds good to me...Charley- let me know if you need help fixing that porpoise problem! http://www.handykult.de/plaudersmilies.de/beerchug.gif
[ April 06, 2003, 10:06 AM: Message edited by: Havasu Hangin' ]

[Phat_Kat]

I've been pissed about that on my tunnel and looked up some areodynamic studies and kinda figured it out. It's because the air that's intentionally being trapped is fighting bow weight making them constantly hop. This is where trim tabs are handy. Apparently motor trim often makes things worse so you should run tabs(that's just what I was told). That's the general price cat owners pay when they get cats. So I hope that helped you question.

[Donnie]

blown23vee:
Hey Donnie! That trip to Larry's just wasn't the
same without you snoring in the back seat! I don't know if I have ever made it down there and back without snoring...It has to be that 3 hour pit stop at HOOTERS eek!
That boat of yours is looking bad ass..can't wait to see it on the water :D

[Skaterfast]

Havasu Hangin is right.My 24' tunnel at 40mph will not release any air all the way through the tunnel.My boat is not a true tunnel until about 55mph.It takes around 60mph for air to exhaust all the way through the tunnel.My 24' will porpose 55 to 73 mph.When I hit 75 or so then there is enough air pressure entering the tunnel to keep the boat up and on top of the water.

[Keith E. Sayre]

I believe that you'll find that the "true" tunnels porpoise worse than the others. The Talon 25 bottom is one of the few that doesn't
porpoise at all. but if you look at the bottom, it is no where near to being a true tunnel. In
fact the center sponson is deeper than the outside 2 sponsons. It seems to me that the
higher the center sponson is, the worse the
porpoise at low speeds. Other boats that are
rumored to have the same bottom are the Conquest,
26' Howard, American Offshore, Eliminator Fundeck,
Magic cat and deckboat and Firehawk.
My buddy Rich Tomlinson in Utah has a 31' American Offshore and it'll porpoise like crazy
until about 75 mph then it goes away. Then if
you want to cruise at 60--buzz it up to 75 then
slow down to 60 and it won't porpoise. Go
figure that one out!
While I'm not an engineer, the above posts sound like credible explanations to me. It all comes down to lift versus gravity. At some angle on the bow, every boat will become too heavy and gravity will bring it down. We fight that gravity with trim, horsepower, propellers and in this case the lift created by the trapping of air which creates air pressure on the bottom of the boat.
The use of trim tabs can be helpful but will slow you down. But if you're a recreational boater,
that'll keep mom happy and we all know how important that is!
Those are my thoughts on the subject.
Keith Sayre
Conquest Boats
Lake Havsasu City, AZ
928-680-1400

[FASTERDAMITT]

Quoted by Keith.
(The Talon 25 bottom is one of the few that doesn't
porpoise at all. but if you look at the bottom, it is no where near to being a true tunnel. In
fact the center sponson is deeper than the outside 2 sponsons. It seems to me that the
higher the center sponson is, the worse the
porpoise at low speeds. Other boats that are
rumored to have the same bottom are the Conquest,
26' Howard, American Offshore, Eliminator Fundeck,
Magic cat and deckboat and Firehawk.)
Keith,
Close but it is a tunnel not a true "cat" just like everything out there (almost)! And no I DO NOT porpoise. Another thing I like is the re-entry is smooth after being a little airborn. I've had boats in the past that would slap hard when landing ass heavy.

[Skullinator]

Talon's Simply The Best. :) :) :) :)

[Dave C]

Mine only hops at low speeds with too much trim up. If I lower the trim, then it goes away at low speeds and I don't have to hit the throttle. Other than that, it doesn't hop.
2000 Cougar 22MTR. It has a relatively small center pod but it has steps and reliefs. However, don't ask me what that means!

[Robbie Racer]

My Carrera 257 is a little different in that if I keep the trim way down it won't porpoise (or go very fast either) but if I bring the trim up half way on the Blue Water scale it will start porpoising at around 75 or so. I have to give it lots of power and MORE trim (7-8) on the scale, then it goes away (unless I bring the trim back down, then it starts the porpoise again). Then take last Sunday at Elsinore where we were testing the new motor. It was fairly choppy from the other boats out there and my boat didn't porpoise one time in any of the maybe half dozen runs that I made. Weird stuff indeed.

[Sandbar Mike]

:D wink
http://www.***boat.com/image_center/data/522/1Talon_Side_View-thumb.JPG

[XLGPP]

That's the general price cat owners pay when they get cats. Shoulda bought a Cougar... and yes Keith it is a " TRUE " tunnel. I dont understand the physics or aerodynamics of it, But Cougar has found a way to build a hull that doesnt porpoise at any speed, with the exception like listed above. (the very low speed with the drive out too far).
ps... Im still offering free rides to any non-believers

[Dave C]

My old 21 ft Eliminator Daytona, did not hop either. However, that was a very light boat with a jet. It was full tunnel too.
Also that had a lot of hp (800) in relation to the lower weight than, say a bigger boat 26-30 ft.
Which really means that it has less cooler space than its bigger brother and therefore less cooler-slosh!

[Charley]

The 21 daytona is actually not a true tunnel... it is actually a deep center pod.... the center pod is the same depth as the outer sponsons

[Robbie Racer]

On my 19' Daytona jet the center pod was actually a little deeper than the outside sponsons. At max speed it would ride on the center pod/ride plate and the outside sponsons would be completely out of the water. Now that was fun. :D

[Infomaniac]

XLGPP:
[QUOTE]
ps... Im still offering free rides to any non-believers Me too.

[Dave C]

The 21 had a center pod that started small and tapered down until it was even with the outer pods at the transom. It was pretty damn stable.
Who made a true tunnel? (with no center pod?)

[MOPAR2YA]

Dave C:
The 21 had a center pod that started small and tapered down until it was even with the outer pods at the transom. It was pretty damn stable.
Who made a true tunnel? (with no center pod?) Are you refering to "catamaran"? wink
Skater to name one.
[ April 08, 2003, 11:20 PM: Message edited by: MOPAR2YA ]

[MOPAR2YA]

[ April 08, 2003, 11:19 PM: Message edited by: MOPAR2YA ]

[FASTERDAMITT]

Greg, you drinkin again?

[Reaper1]

XLGPP
[QB] [QUOTE] That's the general price cat owners pay when they get cats. Shoulda bought a Cougar... and yes Keith it is a " TRUE " tunnel.
XLGPP, Correct me if I'm wrong here but your boat has a center pod and therefore is not a true tunnel, unless Cougar built you a special prototype or something.

[XLGPP]

XLGPP, Correct me if I'm wrong here but your boat has a center pod and therefore is not a true tunnel, unless Cougar built you a special prototype or something. you are wrong indeed sir. 27MTR, no special prototype. I had the 1st one built and to my knowledge, they havent changed anything since they built it.