Cleaver question

[mobil1]

Hi all,

I run an f4 tunnel with yamaha 70ces,
Prop is a merc thru hub cleaver.
What would be the effect if i run an over hub propellor?

[mobil1]

I quess more slip on take off but what on high speed?
Will it give also a higher % of slip or no effect at all?

[Ron Hill]

Where do you live? It sounds like you are interest in learning about props. I can write a book or three about props. Sometimes it is better to know "WHAT TIME IT IS", rather than know how the clock works. If you happen to be near Southern California, come a stay a week or two, I will show and teach you about props. There really are a thousand factors about props. You have some good questions, but not sure your answers a very good. Most of my knowledge is from experience, very little has come from books.

[Fastjeff57]

Ron:

If you ever do write a book on props--which you are certainly qualified to do--I'll by a couple of copies--one for each eye.

Jeff

[omcstratos]

Ron:

If you ever do write a book on props--which you are certainly qualified to do--I'll by a couple of copies--one for each eye.

Jeff

Same, I'll buy the whole series

[mobil1]

Hi Ron,

To bad we are several 1000miles apart :-) .
Visited you last year, and i will keep you to your promis to try the mexican food ;-) .
At least, did my boss contacted you about those gearcases?

That is the beauty of props, you can read as much as you like.
At the end you will need to try to see if it works.
And what works on 1 boat, is crap on another one...
Here is where experience pays off. And that you hlave.

Are you willing to share your thoughts about running an over hub cleaver on a tunnelhull, with a shaft and gearcase designd for an thru hub prop?

[Ron Hill]

Hi Ron,

To bad we are several 1000miles apart :-) .
Visited you last year, and i will keep you to your promis to try the mexican food ;-) .
At least, did my boss contacted you about those gearcases?

That is the beauty of props, you can read as much as you like.
At the end you will need to try to see if it works.
And what works on 1 boat, is crap on another one...
Here is where experience pays off. And that you hlave.

Are you willing to share your thoughts about running an over hub cleaver on a tunnelhull, with a shaft and gearcase designd for an thru hub prop? Well, we are getting ready for the Parker 336 Enduro.....I favor the slip on hubs, but I'm not driving the 30 boat. The 44 Mirage (RED) will have a slip on hub, as I am the Crew Chief on that boat. As you can see from my inventory of 80 HP and under props, most tend to be thru hubs. But my over the hubs are new.

[mobil1]

Did you already sold some over hub props, and did the owners tell you how it went?
Slip on hub, means hub you can easly change?

[champ20B]

Hi all,

I run an f4 tunnel with yamaha 70ces,
Prop is a merc thru hub cleaver.
What would be the effect if i run an over hub propellor?

Well, as much of a "KUNG-FU" mystery as props are made out to be, I use the K.I.S.S method. That means (Keep It a Simple Solution).
I don't know what the optimum RPM is for your engine, but if your really serious on racing one like you have, get it dynoed to see, if you haven't already. If your prop is pitched so as to load your engine such that it runs at the proper RPM, at W.O.T, you are on the right track just to start. Take whatever pitch of propeller that is and determine the theoretical travel by RPM.
-First , take engine RPM and divide by gear ratio. ex.( 6500rpm/2.09) if you have a 2.09:1 ratio.
- Take that answer and multiply by 60. You will get inches of travel per hour.
-Divide that by twelve for feet per hour.
- Take that and divide by 5280 for miles per hour.
- After you get this answer, multiply it by (.80) then by (.90). These will give you a realistic range to go for. For a race boat, 90% efficiency is might be a realistic figure, but I would research on tunnel hulls for that alone if it were me. That would be the most valuable info to have in this case. Find what efficiency tunnels are running at and you will be able to determine a good prop for your set up every time. As far as thru-prop vs. conventional race prop, depends strictly on the gear case design. One prop alone is as good as the other. Only the gear case designs are the limiting factor beyond propeller hub type. If you want a smaller hub, a more streamlined foot/case would be the feasable aim with that. That would depend on the rules for your class though. Finally, If your rig is running within a fraction of the record for the class as is, you are on the money. In fact that would be a way to see what efficiency these rigs run at. Take the optimum RPM the engines are running and calculate by their record speeds. There you have it!

[Fastjeff57]

That's "simple"!

Jeff

[Roflhat]

sure KISS is "Keep it simple, stupid!"

[champ20B]

Hi all,

I run an f4 tunnel with yamaha 70ces,
Prop is a merc thru hub cleaver.
What would be the effect if i run an over hub propellor?

Hi Mobile-1!
I should have read your question more carefully! I confused all the tech stuff with what you were really trying to find out about. I apologize for that. Anyway, for a definite "two cents" on this, My suggestion is to stay with a thru-hub prop. It is just as good on the thru-hub exhaust type gearcase. There are these types of props produced, of which can be run partially submerged for less drag, that describes what your presently running. I don't know what is allowed on this class of boat, for whichever race organization they are run in. But a nose cone is a good addition if it doesn't already have such a design. There will not be any advantage to a ("above water" exhaust type) prop on your rig unless you have a slim "full race" design gearcase with a "above-water outlet" midsection/tower. If you can switch over to such components as these, legally, only a bit less drag would be the advantage. If this is just a go-fast lake boat for you, Don't just spend on a straight cleaver prop. Go all the way with a midsection and gearcase as well, if such are available for your engine. Make it go just as fast as you can!!