Author Topic: Nose Cone  (Read 16635 times)

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Offline V153

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Re: Nose Cone
« Reply #20 on: August 16, 2010, 06:00:42 PM »
Yo Red. Been meanin' to ask. Did you saw the diffuser off that prop or did it come that way. Reason I ask is I believe Walt sawed one off a Raker, or something similar, and picked up 1/2 mph or so?
'81 C500_given away, bought back_75.1 mph
'81 Baja 15SS_140 Frankenrude_66.7 mph
'70 something SpeedCraft_(Allison 16R Clone)_69.0 mph
'79 CVZ19_given away
'71 V153_54.8 mph_wrecked


WALK TALL AND CARRY A BIG BILGE PUMP

Offline OleRed

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Re: Nose Cone
« Reply #21 on: August 16, 2010, 10:34:53 PM »
Yo Red. Been meanin' to ask. Did you saw the diffuser off that prop or did it come that way. Reason I ask is I believe Walt sawed one off a Raker, or something similar, and picked up 1/2 mph or so?

no ... the power tech props don't have that, and I never figured how it would benifit us anyway, with thru-hull exhaust, kinda like the "vent holes" in a prop, if ya got through hull exhaust,  there is no advantage..
1980 23ft Scimitar

Offline V153

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Re: Nose Cone
« Reply #22 on: August 21, 2010, 05:13:50 PM »
Yeah I agree a ventilated prop's gotta be pretty much useless on a thru-hull exhaust boat.

Wonder what's the purpose of a diffuser anyway. Looking at the one on my Lightspeed all's I can imagine it creating is drag?

Anybody know?

Wouldya believe I have less steering torque under hard acceleration with the small hub SRX prop than I do with the Lightspeed. And the SRX is 1/4" bigger & a degree taller? Hmm.

Oh well when I get the dang ding in my SRX fixed & get it back on the boat mebbe I'll have the boys saw the diffuser off the Lightspeed. I'm no engineer but I can't see how it could hurt?   
'81 C500_given away, bought back_75.1 mph
'81 Baja 15SS_140 Frankenrude_66.7 mph
'70 something SpeedCraft_(Allison 16R Clone)_69.0 mph
'79 CVZ19_given away
'71 V153_54.8 mph_wrecked


WALK TALL AND CARRY A BIG BILGE PUMP

Offline MarkS

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Re: Nose Cone
« Reply #23 on: August 21, 2010, 08:51:39 PM »
Quote
Anybody know?
I'm just guessing, but maybe it's to move a little more water out of the way to help scavenge the exhaust out of the hub?  I have always been told that two strokes are much more sensitive to back pressure, reduces power.

That's weird about the larger diameter prop having less torque steer, must have something to do with the hub size?  My 4 blade 19P is 12.5" dia and has almost no torque steer, but the 3 blade 19P 13" has a little.  (More if I trim up to the third hole!)

Sorry to ramble on guys, just keepin the light on till the troops get home...... ;)
Mark
1978 SSV-176

Offline intimidated

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Re: Nose Cone
« Reply #24 on: August 23, 2010, 08:52:16 PM »
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Yeah I agree a ventilated prop's gotta be pretty much useless on a thru-hull exhaust boat.

actually they do work with thru hulls.  i dont have an exhaust bellows so there is a path for air to be drawn in.  i've been playing with the vents in my laser on my intimidator.  with them wide open it was rediculous, similar to  a stall converter in a car.

it came out of the hole like a rocket with the tach pegged at 3k.  problem was that my cruise speed was increased a bunch too,  it would start to fall off plane at anything below about 2500.

I've got them plugged up now.

Offline OleRed

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Re: Nose Cone
« Reply #25 on: August 24, 2010, 09:27:03 AM »
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Yeah I agree a ventilated prop's gotta be pretty much useless on a thru-hull exhaust boat.

i dont have an exhaust bellows so there is a path for air to be drawn in.
I've got them plugged up now.

The exhaust bellows is still on my drive, but I did plug the vents in my prop when I was having so much trouble "blowing out" on take off, and  "grabbing air" on turns, after I raised the "X" dimention, just in the case that would have been a problem. I try'd 16 or 17 props before I got a good worker to go to the lab with, the PowerTech 14 1/4 X 23 worked the best, it has been to the lab 4 times, don't really know what the the pitch and rake is now, the vent plugs have since came out,  don't know when, but I didn't notice any difference in performance.

Is that your red Intimidator with the nitros ?  I was hoping to get to run along side with that boat, but there was so many boats to keep up with, my brain was on overload
« Last Edit: August 24, 2010, 09:32:54 AM by OleRed »
1980 23ft Scimitar

Offline intimidated

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Re: Nose Cone
« Reply #26 on: August 24, 2010, 11:46:18 AM »
thats good info.  wow, you've definitely spent some time figuring stuff out.  I'm just at the beginning stages with mine, and im running a stock 260 [for now]

No, that wasn't me.  i've got a blue '80 model.