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Heres one for you engineer type fellers

C

cont520

Well-known member
What is better for a race aspect a short blade on a longer hub or a long blade on a shorter hub and why?Speaking power shifts / Sench. ect.
 
An engineer will tell you which ever one produces peak thrust will be the best for you! I know how they think I spent ten years with them working on and solving mechanical problems.
 
520, a long story short is that the hub produces NO thrust ...... zero, zip, zilch, nada.
The more blade (prop, air screw, fan) that you can find and turn the better off you'll be. But given a choice, go for diameter every time.

Big diameters bite big air. JMO

olf
 
This I know ,but I was thinking the furthur away the blades start from the crank the less amount of torque roll is produced I was seeing if anyone else has tryed this I have and was wondering if I was just wishing this was true :D
 
I don't think a 76 will hold one of the good Cads. I think 79 or 80 minimum. Crow can elaborate on that. I suppose width plays a role, but they may not make em wide enough. May do fine on a Levitator, but add 100 ft lbs and you may drive through it. One thing I can say bout the Levitator, from what they claim, you can't hurt it. It's probably the power vs. Longevity thing I guess. Same reason a Fuel motor does good to make 1320 ft. not 1320 hours.
 
I beg to differ on the 76" the question was based on a powershift or sensenich assuming it is a 3 blade wide it will hold the engine up to about 1200hp with the proper gear ratio. Lakeland hillrace Art Malone and I with his Nitro Charger 400ci 85% Nitro small block used a 78" 10 blade and also a 3 blade. Engine dynoed just under 1500hp, three blade 76"will hold it. I believe Waterthunder, Bobby Fleckenger and a few others use the same size.
 
Jay that depends on the ratio. By the #`s potter has posted a 76 3 blade with a 2.68 on his motors won`t hold it back. I have a punny buick 455 and a 78 inch wide 3 blade prop and when I put the 2.68 on it it would not hold it back till I had so much pitch in it I was just slapping air,and his motors make mine look like a scooter motor :lol:
 
this is where the warp drive comes in handy small diameter,then add a blade,add a blade and so forth.but just has that con of adjustment.them blades are quite the beeatch.
 
Allot of it depends on max engine rpm I would think, because I'm sure everyone is all over the place when it comes to that. I mean, if one guy has 1200hp @ 9200 and runs a 2.38 vs. same motor w/2.68 I would think it would make a big difference on which motor could be choked down easier, but what if the guy with the 2.38 only turned his motor 8300 and still made 1200hp?

CRAP
I have confused myself :?
 
I beg to differ on the 76" the question was based on a powershift or sensenich assuming it is a 3 blade wide it will hold the engine up to about 1200hp WITH THE PROPER GEAR RATIO. I think we need more specifics...
 
Just to clarify what I stated a hull that rolls on it's side has increased it's drag coefficient and also must displace more water but on the hill it only increases drag. So a prop that rolls bad on the hill will not slow the boat down near as much as it would the same hull in the water! In other words in a hill race run the largest diameter prop you can with out sacrificing too much snap! In the water doing this would slow your boat way down in 400ft! You will be watching those shorter prop boats leave you while your just plowing water! I know this because I have seen it from both ends!
 
Yeah that is right but my ? Which would perform better in a 400' race a long hub or a short hub with the same total length of blades. Lets say the long hub has a 68" blade and the short has a regular blade signature series but both props equaling 72" in length . We are now talking about hub spacing whether it is better to have blades closer to the crank or further
 
Dang it 520, me and you think alot like. I was just thinking the same thing a few weeks back. My 2 cents- I would think to keep the weight close to the center. A long hub will keep the weight closer to the center, keeping the blades shorter, making the prop more snappy and authoritive. Just my 2 cents

Thunder- I was also wondering about the length of a prop for hill racing, longer is better huh. I was thinking maybe short prop but more blades. Their I go thinking again
 
Hub weight or prop weight is no where near as crucial as what the prop diameter is or how much air the prop moves. The weight of the prop is not what is rolling the boat the prop weight is very mute compared to what the blade does and how much air it moves. Here is a dumb dumb analogy take a big heavy prop add a ton of pitch it will roll a boat on the side then take that same exact boat and remove all pitch it will no longer roll not even the slightest so that pretty much proves prop weight is not the major factor in what rolls a boat!
 
The big difference i think would be in the difference in the fact that what ever blade you run some depending on witch have solid tips in them for cut down and if you run the longer hub with the majority of the solid tip cut off will that snap harder than longer blade more tip and less hub.
 
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