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Xerophobic
Joined: 23 Jun 2005 Posts: 970 Location: Calgary Alberta, Canada
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Posted: Sat Jul 16, 2005 5:46 pm Post subject: Time to get serious, rigging questions.... |
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So I've run the boat for a month or so now and Im slowely getting familiar with the hull and all that goes with the alum thing. Now I want to work on you guessed it, speed!
I am currently running my backup motor (78 Van 460) but dropped off my 'good motor' to the engine builder today and should have it back in a week or so It should be close to 500HP and was turning my AA at a hair under 5K in the old boat. No more hypereutectic pistons for me, I learned!
I have some plans but want to see what people think and maybe speak to people running BBFX boats as thats what I think I'll be closest to. Who's running them?
Currently have Berk AA impellor and Im certain this is too big. I want to start cutting it down to the A range and get my revs into the mid 5K range(I'd assume not go higher at the moment), has anyone done this? I know basically whats involved but want to be able to tell a local machinist exactly what to do.
I'm running a berk trim and stock nozzle(locked full up). I want to try a sheetmetal one and work on a very basic trim to get out of the hole. What sizes would be the best to start with in terms of nozzle length, exit size and exit angle? I'm really hoping I can fabricate these myself so I can try a bunch of different ones. I already have dual cable steering in the boat.
I am going to try to weight the boat soon too. Does anyone know what weight a BBFX boat is showing? I thought I'd be real heavy but the 4 buckets aren't heavy at all and I have no cage so I may not be that far out. I am running iron heads but for now thats all the budget allows.
Cheers
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_________________ T-53 , why go up and down when you wanna go round and round???? |
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Fritz
Joined: 29 Jun 2005 Posts: 20 Location: Christchurch, New Zealand
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Posted: Sun Jul 17, 2005 9:34 pm Post subject: |
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Hi Rampager I'm running a long nozzle on my eagle I'll take some photos and get some measurements for you over the next couple of days. I'm running an estimated 450HP that is turning a "B' cut at 5400RPM at a touch over 80MPH if that's any help to you. The change from the standard AT nozzle to the long nozzle gave me an extra 3MPH
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Snikwah
Joined: 23 Jun 2005 Posts: 10 Location: Auckland
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Posted: Sun Jul 17, 2005 10:02 pm Post subject: |
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What is the theory behind the longer nozzle making the boat go faster?
Is it due to the extra leverage lifting the bow out of the water and therefore reducing hull drag? Or is it something else.
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Fritz
Joined: 29 Jun 2005 Posts: 20 Location: Christchurch, New Zealand
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Posted: Wed Jul 20, 2005 1:49 pm Post subject: |
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that has a bit to do with it, due to the extra length you can use that to trim. Also with the extra length and the shape of the nozzle with the smaller outlet the water gets pressurised going through the nozzle giving more thrust.
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SouthIdahoGary
Joined: 15 Jun 2005 Posts: 295 Location: Wilder, ID, USA
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Posted: Wed Jul 20, 2005 2:32 pm Post subject: |
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Snikwah wrote: | What is the theory behind the longer nozzle making the boat go faster?
Is it due to the extra leverage lifting the bow out of the water and therefore reducing hull drag? Or is it something else. |
Some of the "theory" also has to do with the nozzle also being a droop snoot design. Only way more efficient than the cast designs being sold by the manufacturers. Also tougher....
Drops the thrust line.
_________________ "faster, Faster, FASTER until the thrill of speed overcomes the fear of DEATH"#163 "Tuff-n'-Nuff" |
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Xerophobic
Joined: 23 Jun 2005 Posts: 970 Location: Calgary Alberta, Canada
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Posted: Wed Jul 20, 2005 5:25 pm Post subject: |
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I had always heard that the main advantage was leverage to help carry the bow. I have also been noticing the nozzles aren't usually true 'cones' and thats what Gary is getting at. I had planned to make the lower wall of the nozzle come off the flange at 90 degree's so the upper wall is angled down, if that makes sense.
I'd still like some dimensions form anyone running one.
Cheers
_________________ T-53 , why go up and down when you wanna go round and round???? |
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G-force
Joined: 05 Jul 2005 Posts: 105 Location: no-po, OREGON
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Posted: Wed Jul 20, 2005 6:05 pm Post subject: |
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i think the trick is that the cone bends at the end, not that making cones in heavy steel isnt tough enough but if you look close they are kicked upwith a smooth and calculated radius. good luck, i cant wait to see if you reconsider making several after you make one!
also have you seen the trick launch control scoops some guys are running now off the end of the nozzle? i am going to try and integrate one into the reverse gate i am also trying to inegrate. this is a tough one for my pea brain to figure.
does anyone with a launch control scoop have the ability to use it under power at speed? would this bury the nose like a diverter, also would it trim the roost to acceptable tubing levels?
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Xerophobic
Joined: 23 Jun 2005 Posts: 970 Location: Calgary Alberta, Canada
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Posted: Wed Jul 20, 2005 6:37 pm Post subject: |
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I don't think that part of the cone is "bent". I'm pretty sure anyone fabricating one would put a joint where the nozzle kicks back up. Can you look closely is it just a weld joint grinded smooth inside and out? Thats certainly how I had intended to do it and Im not sure there is really any other way. I'm sure the first few I make won't be pretty but at least I can get the hang of it so trying a new style/size is just some hours in the shop and not a ton of cash
I haven't seen the scoops you mean but can sorta envision them. I had fully intended to make something to help holeshot and Im sure that it would be similar to what you mean. I'd have to have that for pleasureboating. I'm also curious if we're on the same wavelength in making it drop farther to give extreme trim and maybe almost a neutral or reverse action. Not sure thats possible with the same device tho
Got anymore pics? The more the better
Cheers
_________________ T-53 , why go up and down when you wanna go round and round???? |
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G-force
Joined: 05 Jul 2005 Posts: 105 Location: no-po, OREGON
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Posted: Wed Jul 20, 2005 7:11 pm Post subject: |
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heres my reverse gate i am trying, never used it yet. i was thinking that since it has a flat spot on the bottom, that i might be able to integrate a scoop deal there for trim/launch control but not sure if that would work. otherwise i have no idea how to have both on separate systems without being giant bulky mechanics.
also if it was rigged as described in the first scenario i am not sure if i would be able to use reverse at speed as the trim scoop would possibly drag in the water and prevent my spindly arms from forcing it down? thi smay be dangerous anyway, but i wanted to try it just for kicks. i guess i will try reverse first and then see about a trim after.
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G-force
Joined: 05 Jul 2005 Posts: 105 Location: no-po, OREGON
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Posted: Wed Jul 20, 2005 7:13 pm Post subject: |
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i hope mr provost doesnt mind me posting this, but his boat is simply the most badass machine i have seen so i cant help it.
look at the bottom edge of the droop, it has a curve to it that isnt just a welded flange. this is the trick i am wondering how they and you will do it.
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Xerophobic
Joined: 23 Jun 2005 Posts: 970 Location: Calgary Alberta, Canada
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Posted: Wed Jul 20, 2005 8:46 pm Post subject: |
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I am on a monitor thats kinda messed up and dark so I can't see the curve in detail till tomorrow.
Does it look like there is a curved peice of tube welded to the cone? I can't imagine(or belive) anyone could/would attempt to bend the actual cone. If the exit size of the nozzle is determined before that stage maybe its just a mandrel bent tube to give a nice transition??? Just guessing here. Im at somewhat of a disadvantage out here as there are none of these parts around to look at!
Grrrrrr, who can give mwe a job out west? My life would be alot easier!
Cheers
(more pics please hehe)
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SouthIdahoGary
Joined: 15 Jun 2005 Posts: 295 Location: Wilder, ID, USA
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Posted: Wed Jul 20, 2005 9:55 pm Post subject: |
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I am going to try and get you some photos posted here. Close ups of "stuff". Note tile pattern in some backgrounds. Tiles are 3". Will post three pics at a time. Keep looking.....I think you can sorta see the weld areas and the other shading that may help with being able to visualize.
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_________________ "faster, Faster, FASTER until the thrill of speed overcomes the fear of DEATH"#163 "Tuff-n'-Nuff" |
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SouthIdahoGary
Joined: 15 Jun 2005 Posts: 295 Location: Wilder, ID, USA
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Posted: Wed Jul 20, 2005 9:57 pm Post subject: |
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3 more
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_________________ "faster, Faster, FASTER until the thrill of speed overcomes the fear of DEATH"#163 "Tuff-n'-Nuff" |
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SouthIdahoGary
Joined: 15 Jun 2005 Posts: 295 Location: Wilder, ID, USA
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Posted: Wed Jul 20, 2005 9:59 pm Post subject: |
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and 3 more
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_________________ "faster, Faster, FASTER until the thrill of speed overcomes the fear of DEATH"#163 "Tuff-n'-Nuff" |
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SouthIdahoGary
Joined: 15 Jun 2005 Posts: 295 Location: Wilder, ID, USA
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Posted: Wed Jul 20, 2005 10:01 pm Post subject: |
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and the fourth set of three
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_________________ "faster, Faster, FASTER until the thrill of speed overcomes the fear of DEATH"#163 "Tuff-n'-Nuff" |
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