Tunnel/Stinger 75...15% slip seems too much

[marchettih2o]

Question:

I have a light tunnel with a slightly modified 50 cu in stinger. I am running a 11 3/4" X 23" cleaver 3 blade. I am only getting 72 mph gps at 7200 rpm's..this calculates out to roughly 15% slip. I am surprised the slip is that high. Is my issue the small diameter I have? A good 12-12 1/2 X 23 is hard to come by it would seem. Any thoughts??? Thanks.

[John Schubert T*A*R*T]

Question:

I have a light tunnel with a slightly modified 50 cu in stinger. I am running a 11 3/4" X 23" cleaver 3 blade. I am only getting 72 mph gps at 7200 rpm's..this calculates out to roughly 15% slip. I am surprised the slip is that high. Is my issue the small diameter I have? A good 12-12 1/2 X 23 is hard to come by it would seem. Any thoughts??? Thanks.

George,

Personally, for your set up 7200 RPM's a bit high. If you were running it with a short tower on a hydro withe the right prop, 7200 would be OK. But wou definitely need to bring the RPM's down. You can try larger diameter, but same approximate diameter & a bit more pitch would have similar results.

John

[88workcar]

Are you running the nitro gearcase or the big one? That would change things a lot.

[Mark75H]

The slip factor number may also be an indication that the marked pitch is not accurate

If the boat runs the same slip factor with every prop, I'd say the slip factor is accurate. If it varies, I'd suspect the inaccuracy in the marked pitch esp if just one prop varies.


What slip factor do you get with other props?

[Billsboats]

Which case would benefit him the small one or the larger one? what r the ratios?

[Fast Fred]

:cool:

[850cc racer]

we run a nitro, 1.86-1 gears. on a 13ft mono 12x23 @6500rpm thats 75mph.

the larger box is 2.4-1

smaller box is better. you can put 2.4-1 gears in the nitro :eek:

[88workcar]

The slip factor number may also be an indication that the marked pitch is not accurate

If the boat runs the same slip factor with every prop, I'd say the slip factor is accurate. If it varies, I'd suspect the inaccuracy in the marked pitch esp if just one prop varies.


What slip factor do you get with other props?
I agree, I have a prop that is stamped 26p, on the slip charts it is really a 27p


Which case would benefit him the small one or the larger one? what r the ratios?

I don't know, it would change the gear ratio that he is multiplying by is why I asked.

[sharpeye Mike]

I second that, what would be the best slip ratio for a cleaver?

[88workcar]

People tell me that my slip is wrong, don't know, don't care 6900rpm 26p 77- 78 mph. 2.0gear

[sharpeye Mike]

I know what you mean, 23" p, 5600 rpm, 59.5 rpm, 1.86 to 1 gearcase, If my calc. is right that works out to about zero, no.....Impossible, if so, can you Imagine when I put real power behind this wheel? Nah that can't be right.

[Billsboats]

What motor and boat?

[Mark75H]

I know what you mean, 23" p, 5600 rpm, 59.5 rpm, 1.86 to 1 gearcase, If my calc. is right that works out to about zero, no.....Impossible, if so, can you Imagine when I put real power behind this wheel? Nah that can't be right.

Exactly right ... an example where if the speed and rpm factors are correct, the marked pitch must be wrong. At least when it goes this way you can be certain; and you can also make an educated guess on what the correct pitch of the prop really is as well.

[sharpeye Mike]

What motor and boat?

15"' 75 hp Johnson on a 13' Delta. This is a fresh motor, 15 hours or so.

[850cc racer]

i have two props identical, 23 long tube cleavers. only difference one has been thinned one hasnt, the thinned prop does 75mph all day long.

the thick one was only good for 73.2 :confused:

[marchettih2o]

The 76 stinger I have has of course, the nitro. The prop is correct as the builder is reknown. I feel I need more diameter. But those props are few and far between, just look at all the postings on this website for 12-12 1/2 X 23-24" props folks are trying to hunt down. Not and easy task since they are still running them in classes.
I would love to try a 12X24 13 spline if there is one out there on a shelf collecting dust. 7200 is about all I want to go, even thouigh it is nothing for this engine after the rebuild.

[Mark75H]

No, it doesn't automatically mean the prop pitch is correct. Even if I made the prop myself, I'd say it still doesn't work as marked/hammered.

[Popa Sam]

[QUOTE=marchettih2o;116752] But those props are few and far between, just look at all the postings on this website for 12-12 1/2 X 23-24" props folks are trying to hunt down. Not and easy task since they are still running them in classes.
I would love to try a 12X24 13 spline QUOTE]

There are plenty of these props available. I own many of them. The problem is nobody that I've responded to wanted to but a prop. They all wanted to try a prop or get information.

Jeff Titus, and others, builds them new on a regular basis for the SST60 racers.

[marchettih2o]

Sounds Great! Please email me what you have in the 12 - 12 1/2 X 24" catagory...three blade solid hub cleaver. Photos would be nice as well
You can get me Sam, at ggusta@tx.rr.com..thanks, george in Texas

[88workcar]

They just had a 23p on ebay, buy it now for 150.00. I have the guy saved if you want it, it went off unsold two days ago.

[marchettih2o]

That would be nice...thanks...PM me please..gg