View Full Version : dual jet cat
Was talking to someone about a dual jet on a 26' cat with about 800-1000 horse,was told it would accelerate from 0-60 in about 4 seconds and close to the same on top end as an out drive ,shooting for 100-105mph....any thoughts??? Cole
Havasu Hangin'
12-09-2002, 09:16 PM
Unless you went with something like this (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1871463358), on a single-engine (dual jet) tunnel, I would think that centerpod would have to be really low...
i'v seen that boat, but i think it would be more in the line of a 19 daytona, the center pod is low enough not to lose suction,you cant have the cut out back transom though,i guess the acceleration is neck snapping...0-60mph in 4 seconds in a 25'v-bottom,i would think a cat could be faster off the line,he says the "stock" dual jets would be 3-5mph slower than a comperable out drive on top end but he thinks he could find that or more in additional pump mods....i just cant imagine 0-60 in 4 seconds,thats faster than any production car that i can think of And not have to worry about things breaking...Cole
[ December 10, 2002, 07:16 AM: Message edited by: Cole ]
Havasu Hangin'
12-10-2002, 07:30 AM
IMHO (I'm not an expert)...to make the larger tunnels fast on the top end, you need more lift...a 19' Daytona needs alot less lift that a 25' Daytona...
Now if the centerpod is truely going to be that low (and need to be stuck to the water for thrust), I would think that it would drag more and lift less...
Accelerate? Yes. With enough HP and torque, you probably could make any 4,000 lb boat accelerate hard...
Big top end? I would think that trying to make that set up dance across the water would be a little tricky...
Just my unedumacated observations...
i dont think there would be an issue on lift with place diverters and droops...but the question on the center pod sticking to the water seems like it would drag and slow things down,and loosing suction on top end.most boats that i have seen tested in the magazines are 0-60mph in about12 seconds with an out drive on 25-28'cat,i would think if the acceleration was fast and the top end was about the same with simalar power and the reliableity was superior.... cry o man, this is too much for a tues morn!!!
Havasu Hangin'
12-10-2002, 10:19 AM
From what I've seen, the efficiency on the top end of a cat is what hurts them out of the hole.
By this, I mean that they are so efficient, that you can run a very high x-dimension and big prop, which sacrafices your holeshot. But hey, who wants to put 800HP in a 25' Daytona for holeshots?
As for lift, I'm not sure a droop and diverter will lift the same as a center tunnel...those bigger cats tend to have stern lift when the air packs the tunnel (which is why they are so fast). They tend to ride very high and level.
I don't know much about jets...but I would think stern lift would not be desired...
To your point, if the center pod has to be that low, is it really a big cat anymore? Or some kind of tri-hull?
My unedumacated 6 cents...
Well after talking further to the shop who would put the dual pump project together, i ran a few of the issues we had reguarding; lift,top end,hole shots,losing suction,fuel economy etc etc.
reguarding lift; i was told ,which i never knew that the bottoms of eliminator,talon,american offshore,rayson craft,dcb,boss cat(conquest)and a few others actually run on the"center" keel and use the out side sponsins more as balancers on top end runs,the effiency of the bottom and packing of air within the channels is where the lift is achieved.These hulls are some of the fastest out there.
reguarding hole shots;A cat, i was told will accelerate as hard or harder than a v-bottom,there is almost no bow rise with jets on 22-24'cats, and there is with stern drives.Dont forget that a jet will have a ride plate,helping even more on bow rise.I was told the boat will come out on plane almost flat.
reguarding top end;tests have been done on v-bottoms and have achieved almost the same in top end,dont forget this is a twin jet,twice the
"THRUST"as a single jet.the mods that could be done to make the jets more high performance is where he says the top end will be found,compared to the stock jets which they have been testing.Also dont forget about the out drive,do you know how much drag an out drive has!!!jets have none!!
reguarding losing suction by airing out
the boat;I was told, that wont be an issue there will be plenty of center keel still in the water even in 2-4'chop to keep the jets loaded,even if you get completly air born, theirs plenty of water in the jets and intake to not be an issue.
reguarding fuel economy;I was told it should be about the same as an out drive. Cole
Havasu Hangin'
12-12-2002, 04:07 PM
Cole:
i was told ,which i never knew that the bottoms of eliminator,talon,american offshore,rayson craft,dcb,boss cat(conquest)and a few others actually run on the"center" keel and use the out side sponsins more as balancers on top end runs,Here's a pic of the back of a DCB:
http://free.***boat.net/gallery/Hot_Boat_Happenings/Boat_Shows/DCB_new_26.JPG
The center pod is cignificantly higher than the outer sponsons...the propshaft is a little above the outer sponsons...I would think a jet intake needs to be alot lower than that...
I was told that some bottoms will not work,too high of a center keel and the notch in the back needs to be filled in order to work,its hard to tell just how much higher the center keel is than the outside sponsins with the notched back
transom in your photo,but doesnt the daytona,f-26 dcb and AO have about the same bottom?
Because i was told they know an AO would work!!
andy01
12-12-2002, 04:57 PM
Mr. HH I think you are very right, and I was thinking the same thing myself. The only boat I know of that has a lower center pod (and I don't know if it is even lower then the outers) is a Magic 28, they designed that into the bottom of the Cat so it would turn like a deep-v in slow turns.
Cole who ever told you that a Cat rides on the center is full of shit and doesn't know what they are talking about (espiecally a DCB)
Here's a pic to help ole HH out..........
BTW this a DCB cat...............
idea2
http://free.***boat.net/gallery/Reader_Rides/Stern_Drives/PICT0656.JPG
Andy
Well THAT picture couldn't be any clearer,thats been one of my big questions,i have always asumed cats ride on the out side sponsins,that photo looks like the center must be 4-6 inches higher,he clearer said some bottoms wont work maybe dcb is one of them.Maybe we can get a photo of an AO or talon or eliminator to see if its lower,i'll ask the shop tomorrow.Cole
Havasu Hangin'
12-12-2002, 06:04 PM
Well, The DCB is closer to the Daytona. and the AO bottom is the same as the old Talon (same mold)...and I was told that the Magic/Conquest bottom is the same.
Like Andy said, I think the center pod helps plant the boat in slow speed turns, but it becomes a drag liability at high speed, so it is higher than the outside sponsons. Like I mentioned earlier, the air packs the tunnel, causing stern lift...
That's why big cats can get away with props that have less stern lift- the design of the boat does it for them.
As cats get bigger, I've noticed the center pod gets smaller...maybe because with twins, you don't need to mount the engine and drive there.
I would bet $1 that the Talon/AO/Magic/Conquest center pod is also higher than the outside sponsons, but I've been wrong before.
Cole, maybe they are talking about a tunnel instead of a cat type hull. A tunnel hull I believe rides the way you described, more center sponson and balanced on the outside. A cat type hull will ride less on the inside and more on the outside, actually I believe a true cat has no center sponson or very little. I think the line gets a little blurred between a cat and tunnel , but there is a difference. The ride is quite different also, especially when turning, a tunnel will be more like on a rail and flatter than cat that leans a bit to the outside.I believe Stoker is a true tunnel and the Cheetah also, Cougar i'm not sure, I think it is an modified tunnel.
Of course I could be a noob and be completly wrong :D
Wayne
i am going to rayson craft this morning to look at the bottom molds,John at rayson said its a talon bottom,my boat is still in the bottom mold so i'll check it out.Interesting point about cats vs tunnel,learn somthing new every day sqsmile .
Cole
We'll i was just thinking eek! ,the shop who is putting this project together says the dual jets would bolt on to his 19 daytona with only having widen the center keel,there for,is the 19 really considered a tunnel and totally different from larger boats?? argue Cole
Havasu Hangin'
12-13-2002, 07:49 AM
Cole:
We'll i was just thinking eek! ,the shop who is putting this project together says the dual jets would bolt on to his 19 daytona with only having widen the center keel,there for,is the 19 really considered a tunnel and totally different from larger boats?? Yes.
That's what I meant about smaller vs larger cats. A 19' Daytona needs alot less lift than a 25' Daytona...so the two smaller tunnels are sufficient. Generally, as the cats get bigger, so do the tunnel(s), until there is no center pod at all...just one big tunnel to trap air.
By definition, a catameran rides on the two outer sponsons...a tunnel rides on the keel, but allows air to be trapped in those tunnels for lift.
IMUO (in my uneducated opinion), if you were to modify a bigger cat with a lower cener pod for a jet, you would be taking away alot of stern lift that it was designed with...
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