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Thread: setback vs top end speed
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11-23-2017, 08:40 PM #1
setback vs top end speed
does anyone have experience or testing results of setback in relation to top end (mainly pad vee...more so hydrostreams but any comments accepted)
im not concerned with handling....strictly top end. i also know each boat and setup is completely different just wondering if theres a general consensus.
for example if you take a boat with 5" setback that runs 100mph ....and add or subtract setback...which one would likely give you more topend. testing and setting each position = prop shaft to optimal height.
ive always heard "small lite boat/big power you dont need any setback" but i see these boats running 6"+ and performing well quite often.
completely different boat but i know some stv guys running top end with motor mounted on trans.
is the only true answer test and test some more and find out?81' HYDROSTREAM VECTOR / slightly Modified 200
before and after:http://www.screamandfly.com/showthre...inished!/page3
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11-24-2017, 12:27 PM #2
subscribed.
1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
1988 BAJA Sunsport 186, 96 225 Pro Max
79 12' Auminum, 95 Merc 9.9
RIP Stu
"So many idiots, so few bullets"
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11-24-2017, 01:06 PM #3Screaming And Flying!
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There is at least one Vector that was running 100+ with 10'' of setback. Ran real high, but flat. On you tube? I have had 10'' on my V-King and it seemed to make the boat do much the same as the Vector did. In essence it gives the lower unit more leverage to lift the hull and let it fly. Keep it level and you are ok, but trim it too much and that is amplified by the additional leverage of the lower and can be a problem. I settled with a 5''hyd plate and still am happy with that. With a light boat, setback really effects the cg as well.
Here's a Viking going 102 I believe it has a big set back...https://www.youtube.com/watch?v=YBKpxJivB5MLast edited by XstreamVking; 11-24-2017 at 01:25 PM.
83 V-King, 96 Mariner, 200 hp ff block 2.5 w/a 28p choppa
We gotta clean this liberal mess up, VOTE TRUMP TO MAGA!
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11-24-2017, 01:13 PM #4Member
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texasvector I don't know about pad v boat @ 100 but have experienced how the setback lifts and carries the boat with very little trim on slower pad vees . Lift + less trim = speed . The stv has a lot of setback in the hull if you look at where the transom is past the pad . Dave you got nothing ? Maybe Whipper will jump in .
1978 21' Campion Skeena 235 Mercruiser
2007 21' Keelowcraft Challenger 350 SBC
1991 19' STV Pro Comp ski 2.4 Bp EFI
1991 18' Lee Craft Tunnel 2.4 Bp carb
12' Valco Honda 10
the honda runs
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11-24-2017, 01:32 PM #5
Have not played much with setback, BAJA has no pad. Jim Russell's TBDP now has a V Hull program as well, put base line for BAJA in it and very accurate with changing engine height. Worked bang on with Cougar, as long as you get the base parameters bang on the program is super accurate. Saves a lot of manual labour with the program.
Dave1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
1988 BAJA Sunsport 186, 96 225 Pro Max
79 12' Auminum, 95 Merc 9.9
RIP Stu
"So many idiots, so few bullets"
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Jimboat thanked for this post
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11-24-2017, 09:07 PM #6
May not help much because neither boat described ran 100, but both ran mid to high 80's. Both had a small gas tank in the bow.
1- 15' Checkmate with a 2.4 200 run a 1" manual jack plate needed more + trim to get some air under it. No windshield
2- 16' Checkmate with a 12" bracket and a powerlift jackplate. 2.4 200 7 pedal carb. Also no windshield.
Ran similar numbers but was more stable and needed very little trim to air out some. Also had the tank in the bow. I Know both rigs fighting the weight in the bow.
I liked driving the 16' over the 15' any day, and was a tad faster and easier to drive. Same I6 28" chopper on both.James H. W2F a V-King... Want 2 Fly a V-King
Dedicated Site for Hydrostreams >> http://hydrostreamforums.com/
My Project 1979 V-King restore >> http://hydrostreamforums.com/viewtopic.php?f=9&t=2761
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11-24-2017, 10:02 PM #75000 RPM
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I gained speed using more setback on my 20' charger while using less trim. I have a 10" setback on it now and with a 5" needed to trim way high with a huge roostertail to get it up on the pad. Now i run about neutral trim and go faster.
I guess it depends on the boat and weight, power ect. I cant see a smaller boat like a stream needing much setback to get the nose up and fly properly. But larger boats then mine seem to run even more then i do to get em up. So id guess the answer is totally boat specific. If you need to trim way up to get your boat to fly, try more setback. If you already fly with neutral trim, i cant see more being of any benefit. Just my opinion
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Jimboat liked this post
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11-24-2017, 10:37 PM #881' HYDROSTREAM VECTOR / slightly Modified 200
before and after:http://www.screamandfly.com/showthre...inished!/page3
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11-24-2017, 11:03 PM #91980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
1988 BAJA Sunsport 186, 96 225 Pro Max
79 12' Auminum, 95 Merc 9.9
RIP Stu
"So many idiots, so few bullets"
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Jimboat liked this post
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11-25-2017, 01:08 AM #10
different everything dave...motor, gear case, speed and prop.....i know makes it hard to compare but I swapped everything when I went 15"
bow does ride hide when I'm wot now...i can fly it flat at 98.....takes nerves and 2 bumps to get the trip mark
and yes ..height was adjusted but prolly ended up around same place ....dead nuts with pad....mine doesn't like motor height....i start blowing out much above padLast edited by texasvector; 11-25-2017 at 01:11 AM.
81' HYDROSTREAM VECTOR / slightly Modified 200
before and after:http://www.screamandfly.com/showthre...inished!/page3
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Dave Strong liked this post
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11-25-2017, 11:15 AM #11
Funny how no 2 boats ever like the exact same set up.
Dave1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
1988 BAJA Sunsport 186, 96 225 Pro Max
79 12' Auminum, 95 Merc 9.9
RIP Stu
"So many idiots, so few bullets"
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texasvector, Jimboat liked this post
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11-27-2017, 01:33 PM #12Member
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Texasvector in the last pic with bow running that high with negative trim was wondering if you could move your bat. and or fuel an inch or two forward and get the motor neutral . Got to have some balls to fly those pad v's that fast
1978 21' Campion Skeena 235 Mercruiser
2007 21' Keelowcraft Challenger 350 SBC
1991 19' STV Pro Comp ski 2.4 Bp EFI
1991 18' Lee Craft Tunnel 2.4 Bp carb
12' Valco Honda 10
the honda runs
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11-27-2017, 02:05 PM #135000 RPM
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TEXAS VECTOR, what prop are you running in those pics with the extra setback? did you ever try a cleaver with more setback? i would think that is the hot setup
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11-27-2017, 05:46 PM #14
Wow every boat,set up,motor set back ,prop , ,cog,driver weight, motor height very diff even on the same boat.Just had the same dis with my bud on this today just don"t make sense but its true no two boats run the same with the same set up ?? Goofy but you can get close and then your on your own to tweak it out.Good luck and keep us informed on the say suptle changes you do to get it optimal.
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11-27-2017, 06:28 PM #15Screaming And Flying!
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Very small differences in the bottom shape make one boat different from another. My boat after blueprinting is a whole different animal from what it was stock.
83 V-King, 96 Mariner, 200 hp ff block 2.5 w/a 28p choppa
We gotta clean this liberal mess up, VOTE TRUMP TO MAGA!
Rebuild thread:
http://www.screamandfly.com/showthre...-it&highlight=
http://www.screamandfly.com/showthre...cs.&highlight=
Videos
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texasvector liked this post
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