Prediction

[snowdog-2112]

setup change-part 1

Imagine that you have the perfect tunnel hull setup and are considering changing propellors to one that is 3mm less diameter but .5 inch more pitch. What do you think will happen with the setup AS IT CURRENTLY IS?

As tempted as many of you are, PLEASE don't read into this. Just answer the question as it is written. Part 2 is coming a bit later.

Snowdog

 

[Bob Kensill]

I'm going to read in to this just to start a bench mark. First I will assume that this perfect set up you are talking about is a boat that runs fast and turns well too. Second I will assume that the prop that is on it is a good all-around prop,not just a SAW prop. If you could pull the original prop then the smaller diameter prop,with more pitch, would let the engine unload easier,meaning more acceleration, and a little more speed,but maybe not an attainable speed by the end of the straight away. I would say that you might see the same lap times,but you might have a small advantage out of the turns.

 

[izitbrokeyet?]

loaded question detected

please refrain from answering until you have more details

this has been a service of the Loaded Question Detection Network (L.D. for short)

 

[shoboat]

Bryan,

The setup will have to change as the propeller efficiency will change a lot

with the different depths. 3 mm is a lot to change and so is a half inch of

pitch or cup. The motor will unwind more,but the speed may not change

much until the motor is lowered in the water more to pick up propeller

efficiency. The pitch or cup added could also load the motor less unless

you adjust the motor ride height. I would recommend a much smaller

change in the propeller diameter first and then I would cup or pitch to

the powerband of the motor. Your question does not have enough setup

information that would be critical to answer your question better. I'm sure

you will tell us that you change from a 40mm prop to a 37mm prop and you

had a big change,right? There are a few schools of thought on the depths of

propellers,some like a bigger blade run higher,and others like a smaller blade

run lower. I like the smaller blade run lower myself,I think you get much better

handling with a smaller diameter propeller with more pitch for the speed.

Thanks For the Brainteaser,

Mark Sholund

Oh Yeah when is part two?

 

[rippinwater]

Imagine that you have the perfect tunnel hull setup and are considering changing propellors with the setup AS IT CURRENTLY IS?

Snowdog

You will, no longer, have the perfect tunnel hull setup....

 

[nitrotoys]

I thought i had a good idea, untill i read the answers and now just confused.

I will wait for part 2.

 

[MarkScott]

and now just confused.

I'm always that way...

Mark..

OB Nut Racing: Now where did I leave that tool?? :blink: :unsure:

:lol: :lol:

 

[GTR]

Hi Guys

Not meaning to be a wet blanket but there is no such thing as the perfect tunnel set-up. There are to many other variables like temperature, humidity, wind speed and direction, other boats on the water etc. etc. etc.

Sorry about that but are you suggesting you had the perfect set-up? You didn't mention if the change from one size prop to another was a change in blade form or number of blades or what - hey this questions got such a big hole in it I can drive my truck through it. :lol:

I eagerly await your next instalment. :blink:

 

[snowdog-2112]

All,

Using the best baseline I had to compare performance (Namba district 8) The Villain was flying nice, had great R's with a clean, crisp sound and not hopping which I recently resolved. Figuring the setup was SWEET I changed props with the characteristics described but upon launch the flex shaft broke and I left the prop collet wrench at home :angry: so I never got to see the change.

I realize that a K&B SS may not have the power to turn the bigger pitch well but given where I am now, my efforts are for learning as there is very little opportunity for racing here.

Just wanted to see what your opinions were on what would have happened!

This is not part 2, I was going to get that from the answers you all gave.

GTR - You are a wet blanket! :lol:

Nitrotoys - it would be nice to hear what you have to say.

Rippinwater - Duh!

Shoboat - TMI...TMI.

krpnova - good post, that's the idea of what I was looking for.

Snowdog

 

[shoboat]

Hey Bryan,

Get a new shaft in the motor and give us your part two results :lol: .

Once you lower the motor you will see what TMI is all about :lol: .

Keep on testing, and keep us posted, so we can help you, if you need it?

Thanks,

Mark Sholund

P.S. Too Much Information (TMI) you must be 17 Bryan,that is what my

daughter tells me all the time :lol: :lol: :lol: .

 

[snowdog-2112]

Ok gang, PART 2.

Here is the deal. I was running a Grimmy 1440 and the engine was winding out real nice yesterday and the boat was flying great as previously mentioned. Today, got to run the boat with an X640 cut down to 37mm and here's what happened.

The engine never built up enough rrr's to lean out. I had the remote needle at max lean and the darn thing kept running where it would lean out around 90 with a 1440. It appeared to run more slowly but the boat would hold the turn nicely with a "blip" on the throttle. Punch it 1/2 way through the turn and it torque jumped real quick. I brought it in, raised the engine slightly and tossed it back out. The only noticeable change afterwards was a bit more hopping which makes sense.

So, IMHO going to a smaller diameter/more pitch prop on an SS will not give you a speed increase...only a headache (which I have right now) <_<

Any questions?

Snowdog :huh:

 

[user 115]

Did you get radar readings on what each prop was running?

 

[shoboat]

Bryan,

Now try to put the propeller deeper in the water and see what happens?

I think you have a little too much pitch if it wants to torque roll in the

corners. A little back-cut on the X-640 works well also. I believe Gene

can help you out with those X-640's. It is also one of Kevin's favorites

also. I think the 1440's will be the propeller to beat very soon.

Thanks, Keep Testing,

Mark Sholund

Props-4-U

 

[Slideblues]

SS and Villain..... Mike Z 1440 set .150 sponson bottoms to shaft centerline.... HARD to beat.

X640...... I believe JD liked that one dia reduced with a CMB Greenhead

Me....... Well Im a crazy sum beach..... but my fav so far the 1640 backcut and dia at 39mm.... piped and aired out to the max......Dont try with out ADULT supervision :lol:

 

[snowdog-2112]

I don't have access to a radar or GPS to test these. I sure wish I did. HEY! that gives me an idea. Can anyone recommend a GPS that will fit well in a Villain?

I know that the "ear and eye" method is not accurate for determining speed but I know that the engine was not winding out as it should. Therefore it was not making maximum efficiency. I have a couple more props to test but I will wait until my new boat is done before running those. Perhaps I'll have a GPS unit at that time as well.

I have a very nice CMB .21 TT coming back to me once the "doctor" is done repairing it and I plan to run the X640 on it with a boat designed for mod engines. Can you say "balls to wall"?

Gene, Love your humor man!

Snowdog

 

[MarkScott]

Bryan,

I got a Garmin Etrex GPS off of flee bay.. Not bad, it was under $100.. Weight is six ounce & 4"h x 2"w.

Check it out..

Flee Bay Garmin GPS Sale

Mark..

 

[duc]

You can use my GPS (Etrex) anytime Bryan. It wil fit. Would be nice to someone break my Dutch (European??) record <_<

 

[rippinwater]

Today, got to run the boat with an X640 cut down to 37mm and here's what happened.
The engine never built up enough rrr's to lean out. I had the remote needle at max lean and the darn thing kept running where it would lean out around 90 with a 1440. It appeared to run more slowly but the boat would hold the turn nicely with a "blip" on the throttle. Punch it 1/2 way through the turn and it torque jumped real quick. I brought it in, raised the engine slightly and tossed it back out. The only noticeable change afterwards was a bit more hopping which makes sense.

So, IMHO going to a smaller diameter/more pitch prop on an SS will not give you a speed increase...only a headache (which I have right now) <_<

Snowdog :huh:

"Told Ya So"....lol :lol:

 

[rippinwater]

No seriously, the x640 needs a healthy chunk taken out of the trailing edge. The one I run on my 3.5ss is cut down 3mm from the back of the hub, returning to original height 3mm from the tip of the blade. I also thin the trailing edge until it is very sharp. With this prop I get excellent acceleration, high rpm, and (yes) high speeds. I dont know what it will do to your handling because my boat is scratch built and is a whole different animal than a Villian. You're just going to have to test...test...test....good luck