Why no intake fins or rudders on sprint boats ?

[manuel]

I noticed that the tightest turning boats, the jet sprints, have no intake fins or rudders, why dat be ?, I saw Scott, Hamilton and Doen pumps and none of them have them, Guru's, please explain why this works for them,
Manuel

[Rampager]

How long you think one would stay on the boat!? lol
The jet blast gives the turning force, not any rudder. The trick is to design the bottom of the boat to stick in the corners and not in the straights! Not an easy task.....
(sprint boats I've seen have alot of lift strakes and they are looong)

[canuck1]

The odd one does have a fin, right in front of the intake.

[Aluminum Squirt]

I'm no guru, but my hull was originally designed to be a sprint hull and its got strakes(not even sure that's the right word???), 8 actually (4 per side) that go from transom all the way forward well past any area that could be called a running surface. When I've got it running well, it runs pretty dry (nothing like a tunnel, but pretty good for a V with limited HP, back off the throttle a touch and it settles down enough for those strakes to make it handle like a slot car. With the way I drive, a fin wouldn't last one run :) . I've always thought that blueprinting my hull would be worth some MPH because the strakes are welded on periodically and you can see that the hull has flexed due to some heat issues during the welding. I'd love to flip it and work the bondo, but I'd probably scrape it all off on the first sand bar. Now if I can find somebody that wants to donate a ZZ4, maybe I'll be racing this season-Aluminum Squirt

[canuck1]

Squirt
the fin on my 13' was only an inch high so it survived a few years over the gravel

[1Bahnerjet]

is Tin lighter than Fibreglass, does the lite weight aid in Turning. lite all the way around, shorter lenght, sm. block power. just tryin' to think of reasons they turn so FREAKIN" Fast :idea:

[berk]

is Tin lighter than Fibreglass, does the lite weight aid in Turning. lite all the way around, shorter lenght, sm. block power. just tryin' to think of reasons they turn so FREAKIN" Fast :idea:
because if they didnt theyd be up the bank, and then to the bank.

[canuck1]

is Tin lighter than Fibreglass, does the lite weight aid in Turning. lite all the way around, shorter lenght, sm. block power. just tryin' to think of reasons they turn so FREAKIN" Fast :idea:
It is all bottom design and a rigid hull. My 13' was quicker my 15' is faster, both turn the same, less weight and a more rigid hull is faster with less power.
Ask Bottom Feeder he runs a 496 in his 13'

[bottom feeder]

I am no guru So here is guess
Manuel, You are right on. Most sprint boats have no rudders or intake fins. Some add a vary small fin for better high speed tracking. Here is a pick of the one in my ride plate it is .375 inch tall and 3.5 inches long and made a world of diferance in straight line manners
http://www2.***boat.com/image_center/data/520/1501cav_rudd-med.JPG
Side shot of plate
http://www2.***boat.com/image_center/data/520/1501cav_plt_lft-med.JPG
The intake fins are removed as it induces cavitation in the turns. In a real tight high G load turn much of the pump loading is done by a side motion rather than frontal as in drag and most fast lake boats. When the intake fins are present it blocks all side loading ability along with a host of other problems.
As per the norm I fully expect to be harmmered on this but?
In my mind they serve no usefull function and should be removed on any true high performance/ race boat. They serve as a tracking aid for straight line performance. This is and should allways be a function of hull design in my eyes. The pump is to push the hull not make it track staight.
As Rampager said these hulls have alot of strakes. Most are 3 full length and one short per side. (as to not track air down to the intake area) They are not lifting stakes if you generate lift the boat simply skips in the turn and bang your on the outside looking in. The strakes are to force the hull to bite or move more water in the turns. The more strakes the more water that must be moved for the boat to slide. Less slide means harder turns.
On another note most are a delta V bottom with the delta pad installed at a slightly differant angle than the keel line. Up at the transom. This is what Aluminum Squrit and Canuck1 made mention of. This is done to free the boat up in the straights. The hull rocks back on the delta pad and no strakes are in the water. When you lift on the throttle it drops the front of the pad in and wets the strakes you then add throttle and turn, further driving the nose in.
Weight. Lighter is faster. The lighter boat must displace less water for the same grip.
My hull with the all steel BBC and AT pump would not be competitive aginst the same hull with the same HP with a aluminum SBC and axil flow pump on the race course. In a drag race I will hand it to them. The mixed flow pumps cavitate and do not accelerate near the axil flow. The mixed flow do however out MPH the axil flow by a large margin.
On the glass/aluminum Glass is about .069 LB/in3 aluminum is .0975 LB/in3 so the glass is lighter. You won the battle but lost the war :D the aluminum hulls are lighter due to the construction. My hull for example is as follows, bottom .156 thick, gunnels .09, transom .09, deck .06. stringers .125 strakes .125. all of these are uniform thickness. the stringers are a sort of C channel
http://www2.***boat.com/image_center/data/500/1501tork_link-med.JPG
with a aluminum hull there is no wood, no varing thickness, no chop gun fill, and no 5 oz here 20 oz here. While yes you may get a purpose built glass 20' 6" hull under Eagles tunnel at 535 LB with intake. question is the glass hull of the same weight a more rigid base to start from? This is the off the shelf light weight hull from them. I know you can order it lighter if required. But then agin I have seen the advantage that aluminum has.
ok lets have it now :D