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Thread: Why don't you see tunnel hulls on the v-8's

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    Default Why don't you see tunnel hulls on the v-8's

    JUST CURIOUS AS TO WHY YOU DON'T SEE THE TUNNEL HULLS ON THE V-8 POWERED JET BOATS. SEEMS LIKE A GOOD IDEA, KEEPS ROCKS OUT OF THE GRATES IN SKINNY WATER. SO, WHY NOT?

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    Default tunnels

    Peregrine built some bow pickers with tunnels for some of the Russians in the Copper River gillnet fishery. They gave twin 350 chevs with jets in them. But the jets aren't in the tunnel. They wouldn't work if the were. Too much cavitation. They are on the pontoons. They're fast, but personally, I don't like them. You lose flotation and because of that, you can't pack as big a load as with a full bottom boat. It also affects how your boat handles in big seas and breakers. You draw more water when standing still or idling also, than in a full hull.

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    Member Xerophobic's Avatar
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    As a general rule tunnels in jetboats cause cavitation under certain circumstances especially when cornering hard. In fact they are so tricky to design so they dont cavitate we do not install them on ANY of our boat models, V8 or SJ etc.

    In extreme shallow water the last thing you want is cavitation in a hard corner and in most circumstances a non tunnel boat with a well designed intake system will run as shallow as a boat with a tunnel. I guarantee you it will outturn one. Its a bit of a different situation with the OB scene but for inboards I would not recommend them

    Cheers
    Skinny water addict

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    Default Tunnels great for drag racing

    Back when I was younger and alot dumber (just a tiny bit) I raced alot of boats. Tunnel hulls with what was called a droop scoop were a very quick combo. World record when I was playing was around 150 in the quarter mile on top fuel. With a prop it was almost 100 mph faster. Baker boats made a great tunnel BUT.... As mentioned without that scoop cavitation and turning were severely hampered. Some of the Snake river guys tried the tunnels cause they were fast. The only way they'd perform was on the straight aways but the finger grate on the scoop didn't stop everything and rocks were regularly sucked up (tremendous bottom cleaner when the vacuum cleaner is powered by 800hp. Replacing a 3 stage every weekend is no fun. Thats my $.02 worth.

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    Quote Originally Posted by Tealer View Post
    Back when I was younger and alot dumber (just a tiny bit) I raced alot of boats. Tunnel hulls with what was called a droop scoop were a very quick combo. World record when I was playing was around 150 in the quarter mile on top fuel. With a prop it was almost 100 mph faster. Baker boats made a great tunnel BUT.... As mentioned without that scoop cavitation and turning were severely hampered. Some of the Snake river guys tried the tunnels cause they were fast. The only way they'd perform was on the straight aways but the finger grate on the scoop didn't stop everything and rocks were regularly sucked up (tremendous bottom cleaner when the vacuum cleaner is powered by 800hp. Replacing a 3 stage every weekend is no fun. Thats my $.02 worth.
    I dont think he meant tunnel's as in tunnel hulls. I think he meant the small tunnel alot of builders make in the bottom of a v bottom/delta boat to raise the pump and intake up from the keel of the boat.

    these are also very common on OB jet hulls

    Two totally different things

    Cheers
    Skinny water addict

  6. #6

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    Hey, thanx for the info! I am talking about the small tunnel intakes like on the phantoms,sjx's, maybe woolridges?, (sportjets). I heard t-jet denali's were having cavitation problems. I guess i don't understand the cornering and handling problems. The above mentioned boats are supposed to handle like they are on rails. Why would a v-8 be different?

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    Quote Originally Posted by pineridge View Post
    Hey, thanx for the info! I am talking about the small tunnel intakes like on the phantoms,sjx's, maybe woolridges?, (sportjets). I heard t-jet denali's were having cavitation problems. I guess i don't understand the cornering and handling problems. The above mentioned boats are supposed to handle like they are on rails. Why would a v-8 be different?

    For what its worth we did some extensive testing before we finalized the design of our Expedition jon style boat and concluded we did not want to put the boat out with a tunnel in it despite it seeming to be "all the rage" in the jon market right now. We simply could not get the boat to handle properly in corners with this design.

    We are also more active than any other manufacturer in the performance/sport boat market and we often find many consumers are unaware of jjust how well a jetboat "can" handle, which makes the handling topic very subjective. Anyone who's ridden in one of our Steptec bottomed sportboats would attest that comparatively no delta bottom boat handles "like on rails" (this includes even our delta's)

    Moral of the story is: drive as many boats as you can before purchasing one and make sure they allow you to put the boat into conditions you're likely to encounter and ask them to demonstrate hard cornering etc

    Cheers
    Skinny water addict

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    Quote Originally Posted by Xerophobic View Post
    For what its worth we did some extensive testing before we finalized the design of our Expedition jon style boat and concluded we did not want to put the boat out with a tunnel in it despite it seeming to be "all the rage" in the jon market right now. We simply could not get the boat to handle properly in corners with this design.

    We are also more active than any other manufacturer in the performance/sport boat market and we often find many consumers are unaware of jjust how well a jetboat "can" handle, which makes the handling topic very subjective. Anyone who's ridden in one of our Steptec bottomed sportboats would attest that comparatively no delta bottom boat handles "like on rails" (this includes even our delta's)

    Moral of the story is: drive as many boats as you can before purchasing one and make sure they allow you to put the boat into conditions you're likely to encounter and ask them to demonstrate hard cornering etc

    Cheers
    I am curious about the "steptec" bottom, I looked on your website and could not find any mention of it. Perhaps I missed it. Can you explain what it looks like, photos would be great. and how it works.
    Thanks

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    Steptecs are only available on Sport boats and they appear on all our Eagle models except the Expedition and 16 V Sport.

    Pictures of one can be seen here:

    http://www.outlaweagle.com/forum/viewtopic.php?t=1290

    The design utilizes 2 hull steps to break surface tension for higher speed and fuel efficiency and what I call a "hard chine" which bites in corners, and it bites hard!

    The trick to a design such as this is using the steps to aerate the water travelling across the bottom either side of the intake but ensuring the pump remains fed with clean water even in hard turns.

    The 17 Sport with this bottom will NOT spin out even at WOT, you can probably coax a 19 or 21 to spin out if you put enough speed/power to them but the spin would be a violent thing you wouldnt want to do twice.

    These boats turn like on rails
    Skinny water addict

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    Quote Originally Posted by Xerophobic View Post
    Steptecs are only available on Sport boats and they appear on all our Eagle models except the Expedition and 16 V Sport.

    Pictures of one can be seen here:

    http://www.outlaweagle.com/forum/viewtopic.php?t=1290

    The design utilizes 2 hull steps to break surface tension for higher speed and fuel efficiency and what I call a "hard chine" which bites in corners, and it bites hard!

    The trick to a design such as this is using the steps to aerate the water travelling across the bottom either side of the intake but ensuring the pump remains fed with clean water even in hard turns.

    The 17 Sport with this bottom will NOT spin out even at WOT, you can probably coax a 19 or 21 to spin out if you put enough speed/power to them but the spin would be a violent thing you wouldnt want to do twice.

    These boats turn like on rails
    Nice photos and a GREAT looking boat.! The 2 hull steps look like a lifting strake design? If I am looking at it right? Since they do not run full lenght of the hull, are they in the water when the boat is on step? I presume they stop short of the planning surface to allow air to escape? Do they affecting the handling when the boat is on step? or is the turning capabilities coming from the large reverse chine?
    Also quite a bit of deadrise to that hull.

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    Quote Originally Posted by Akgramps View Post
    Nice photos and a GREAT looking boat.! The 2 hull steps look like a lifting strake design? If I am looking at it right? Since they do not run full lenght of the hull, are they in the water when the boat is on step? I presume they stop short of the planning surface to allow air to escape? Do they affecting the handling when the boat is on step? or is the turning capabilities coming from the large reverse chine?
    Also quite a bit of deadrise to that hull.
    No the boat still has standard lifting strakes but they terminate at the first step. I think the best shot to show the actual steps are the picture labeled:

    00 097r.JPG

    The first picture on this page shows the chine design which allows the boat to turn so hard(this is a 19 footer)

    http://www.outlaweagle.com/forum/viewtopic.php?t=1792

    You have a good eye, Sports are all 20 degree's and the Sabre model is 16

    You have to keep speed up in shallow water but nothing turns like these boats

    Cheers
    Skinny water addict

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    Quote Originally Posted by Xerophobic View Post
    No the boat still has standard lifting strakes but they terminate at the first step. I think the best shot to show the actual steps are the picture labeled:

    00 097r.JPG

    The first picture on this page shows the chine design which allows the boat to turn so hard(this is a 19 footer)

    http://www.outlaweagle.com/forum/viewtopic.php?t=1792

    You have a good eye, Sports are all 20 degree's and the Sabre model is 16

    You have to keep speed up in shallow water but nothing turns like these boats

    Cheers
    Thats a BAD ***** looking boat, I can see the step in the hull now. That looks like a very complicated hull design..
    The chine is very aggresive and I can understand why it would grip the water and turn so well.
    Does the step in the hull create some low pressure and suck the back of the boat down?
    Great pictures.....I think I could be great friends with the BALD MAN

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    Quote Originally Posted by Akgramps View Post
    Thats a BAD ***** looking boat, I can see the step in the hull now. That looks like a very complicated hull design..
    The chine is very aggresive and I can understand why it would grip the water and turn so well.
    Does the step in the hull create some low pressure and suck the back of the boat down?
    Great pictures.....I think I could be great friends with the BALD MAN
    The bald man is one funny sumb$%@#! great guy too and has a nice welded window 19 Sport. He'd have something to say about how those steptecs handle for sure

    Here's his repaint after getting tboned on the Red Deer River haha

    http://www.outlaweagle.com/forum/vie...er=asc&start=0

    They did go thru several designs before getting one that worked well in the corners from what I understand. Set up right these boats air out very well.

    Skinny water addict

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    Default Not just complex and performance oriented... double tuff too!

    Quote Originally Posted by Akgramps View Post
    Thats a BAD ***** looking boat, I can see the step in the hull now. That looks like a very complicated hull design..
    The chine is very aggresive and I can understand why it would grip the water and turn so well.
    Does the step in the hull create some low pressure and suck the back of the boat down?
    Great pictures.....I think I could be great friends with the BALD MAN
    Outlaw builds some of the toughest bottoms on the market, I think the angles and structure of the step tech is a big part of that. We've brutalized ours and it's still perfect.

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