Reducing Lift from a Prop

[Rick Doane]

Aside from bending the outer edge of the prop, what are other options that work for you?

Rick

 

[shoboat]

Rick,

What is wrong with bending the outer edge of the leading edge of the propeller?

You can backcut the trailing edge.

You can cup the trailing edge @.7radi

You can bend some tip pitch in the tips with a mandrel or a steel ball.

All of these will work with a little different ride characteristic.

I like to mix a few of these ideas together, they work well.

Tip: If you tip pitch and bend the outside of the leading edge together

you can increase the efficency of the propeller also.

Sharing some good information here fellas.

Have Fun Testing,

Mark Sholund

231.590.3023

 

[moparbarn]

i'm listening, thanx mark !

 

[dwilfong]

Thanks Mark for SPOON feeding us.

Any insight on props is much appreciated.

Going to try a H7 I have bin working on with the back cut you told me about with the new tips Incorporated tomorrow on my 21 rigger.

Had to give it 3.7 tip cup to just to hook it up with the back cut. Will see what the leading edge bend dose.

David

 

[Joe Warren]

Aside from bending the outer edge of the prop, what are other options that work for you?

Rick

Cut the trailing edge next to the hub... or leave it alone & raise the strut.

 

[Rick Doane]

Mark:

I use all of the items that you have mentioned. What I'm finding is that when I increase the pitch (full blade) of the prop, it really begins to lift the back of the boat and edge curl does not overcome the lift as well as tip cup does. Also, any changes to boat set up can drive you back to square one with what used to be killer props.

The 101's have so much punch, keeping the prop(s) hooked up is the issue. I have not been able to put enough pitch in our props to see exactly how much is too much. As you know, this process takes many hours of experimenting.

Joe:

I think you're right about cutting next to the hub. The next attempts will be just how much to remove and use in conjunction other bends as mentioned previously.

Rick

 

[dwilfong]

I did some testing with my 21 rigger yesterday and the edge cup with the tip cup hooked up real good. the rooster tail is nice and flat now and the eng runs smother which made the boat smoother. Found that you can use less tip cup 3.4 compared to 3.75 on the H7 and get the same speed. The back cut took the lift out of the prop.No hoping now.

the cup on the leading edge is more like a small curl that matches the tip cup. Did not change the whole blade just the very edge.

The progression is 2.4 lead, 2.7 middle, 3.4 last 10 deg only on the tip.

David

 

[Joe Warren]

Mark:

I use all of the items that you have mentioned. What I'm finding is that when I increase the pitch (full blade) of the prop, it really begins to lift the back of the boat and edge curl does not overcome the lift as well as tip cup does. Also, any changes to boat set up can drive you back to square one with what used to be killer props.

The 101's have so much punch, keeping the prop(s) hooked up is the issue. I have not been able to put enough pitch in our props to see exactly how much is too much. As you know, this process takes many hours of experimenting.

Joe:

I think you're right about cutting next to the hub. The next attempts will be just how much to remove and use in conjunction other bends as mentioned previously.

Rick

I barr cut ( Radius round cut) the trailing edge on the hydros to kill lift. This same mod on a mono kills too much lift. So I V cut the trailing edge on the mono`s. Unloads the prop & dont effect lift as much...... IF you BARR Cut take it easy. it effects lift quickly.......

 

[shoboat]

Rick,

I think you need to start working with bigger propellers.

Try some 1475's with the mods we have been talking about.

I just did some very custom 1667's with 6" of pitch in them ,

but I am not sure of the test results yet.

70 mm to 75 mm is the size that 101's should be running.

If you bend the tips down equally you will see a lot of results.

Keep Testing,

Mark Sholund

 

[Chris Wood]

Rick

I barr cut ( Radius round cut) the trailing edge on the hydros to kill lift. This same mod on a mono kills too much lift. So I V cut the trailing edge on the mono`s. Unloads the prop & dont effect lift as much...... IF you BARR Cut take it easy. it effects lift quickley.......

Joe,

have you broke any blades doing the V cut? i have seen and heard of a few others that have.

chris

 

[Rick Doane]

Mark:

I use all of the items that you have mentioned. What I'm finding is that when I increase the pitch (full blade) of the prop, it really begins to lift the back of the boat and edge curl does not overcome the lift as well as tip cup does. Also, any changes to boat set up can drive you back to square one with what used to be killer props.

The 101's have so much punch, keeping the prop(s) hooked up is the issue. I have not been able to put enough pitch in our props to see exactly how much is too much. As you know, this process takes many hours of experimenting.

Joe:

I think you're right about cutting next to the hub. The next attempts will be just how much to remove and use in conjunction other bends as mentioned previously.

Rick

I barr cut ( Radius round cut) the trailing edge on the hydros to kill lift. This same mod on a mono kills too much lift. So I V cut the trailing edge on the mono`s. Unloads the prop & dont effect lift as much...... IF you BARR Cut take it easy. it effects lift quickley.......

Joe:

I have not had to do the Barr cut yet. However, I think that is next in the progression of attempts. Tip cup has shown the best/quickest result but the cup has to be the same on both blades/props. Otherwise, the boat takes a dump. The acceleration is unbelivable. Hooked up better in the turns than anywhere.

R

 

[Rick Doane]

Rick,

I think you need to start working with bigger propellers.

Try some 1475's with the mods we have been talking about.

I just did some very custom 1667's with a lot more pitch in them,

but I am not sure of the test results yet.

70 mm to 75 mm is the size that 101's should be running.

Keep Testing,

Mark Sholund

Mark:

I have not been able to get any pitch to grab at 70 mm. Currently, we are running 64.6 mm. w/ 5.3" of full blade pitch. This is an average of the total stations I measure. Tip cup exceeds 7.0".

Rick

 

[Joe Warren]

Mark:

I use all of the items that you have mentioned. What I'm finding is that when I increase the pitch (full blade) of the prop, it really begins to lift the back of the boat and edge curl does not overcome the lift as well as tip cup does. Also, any changes to boat set up can drive you back to square one with what used to be killer props.

The 101's have so much punch, keeping the prop(s) hooked up is the issue. I have not been able to put enough pitch in our props to see exactly how much is too much. As you know, this process takes many hours of experimenting.

Joe:

I think you're right about cutting next to the hub. The next attempts will be just how much to remove and use in conjunction other bends as mentioned previously.

Rick

I barr cut ( Radius round cut) the trailing edge on the hydros to kill lift. This same mod on a mono kills too much lift. So I V cut the trailing edge on the mono`s. Unloads the prop & dont effect lift as much...... IF you BARR Cut take it easy. it effects lift quickley.......

Joe:

I have not had to do the Barr cut yet. However, I think that is next in the progression of attempts. Tip cup has shown the best/quickest result but the cup has to be the same on both blades/props. Otherwise, the boat takes a dump. The acceleration is unbelivable. Hooked up better in the turns than anywhere.

R

I Have worked a ton on My 60 Hydro porps with the mods you speak of.......

 

[Luca Gray]

How about just shorten your pipes and run more rpm's

in steed of massive dia propellers that will through the boat around.

just a thought.

cheers Luca

 

[shoboat]

Luca,

68 mm to 70 mm propellers are the right size for a 101 motor.

The RPM is great with the 101, but you can also benefit

with more tip speed on the back of the boat. If you have

the right amount of strut weight on the back of the boat

you will not keep blowing out the propeller.

Thanks,

Mark Sholund

 

[shoboat]

Chris,

The V-cut propellers should be hardened so they last a little longer.

With the trailing edge cut up so much and the power of a good 101 motor

you are going to flex and break some propellers with that kind of cut.

I have suggested to harden them to those that have bought them from me.

Some have had good success without the big v-cut recently.

Thanks,

Mark Sholund

 

[BigChuck]

Rick

The situtation as I see it is the tale of two motors. "Which one do you guys want?"

The motors in there current form/numbers are going to be more power than RPM. IF staying with a Power platform you will need to go places that you may not have considered prop wise. If going RPM you are already there. I have seen a set of FULL BLOWN 101's and they are REVVV . Oh an like Luca said...........Short pipes. Whlie running 90 motors this choice was not required. The RS 101 has changed that. If you think it has not, the question and the quest that most are on................Say otherwise.

Me..............FULL ON "TOP FUEL POWER"