prop tweaking

[Guest_AMPBA 237]

could any one give me some info on geting the best from props and if some one couls also give me some details on how to build a pitch gauge using a dial gauge need to further my knowledge in pusuit of more speed

 

[apache5056]

Working with props is a black art and there is no real set standard. Most modifacations are custom to each boat and it's setup.

The best explaination I've ever found on RC props is at a gas site (I'm sure there's some glow info on the www as well though), Shark Racing. Scroll down slightly to "Drive Train".

The idea on props is about the same between gas and glow.

 

[Doubledog]

http://rcboat.com/prop.htm

http://www.rcprops.com/rcprops/index.html

 

[JNoice]

Go to ABC prop website

http://www.abcprops.com

Select cup in the header,They have an interesting article on prop cupping

 

[Guest_AMPBA 237]

thanks for the little bit of info guys i do appreciate all that i can get a hold of and yes your right in what you say it's a black art i have always said that myself h34r:

 

[jaso]

So, after looking at the info at the ABC site, is it fair to say that using cupping to increase performance you are in fact removing some pitch and limiting the slip of the prop? And also to go with this you should unload the prop some by removing some material or spooning the edges of the blades.

I know this is probably generalising but I'm trying to come to grips with learning to mod props and it would be helpful to have peoples thoughts and ideas to steer in the right direction? :blink:

 

[apache5056]

First rule of thumb, one change at a time. Adding some cup is the easiest and generally first thing to do. I recommend taking a desent prop, add some cup until it's hard to get or will not get on the pipe, then start back cutting it until it runs again. Then check to see if your speed and handling has increased.

(I would rather give up some speed to have a better handling boat. To finish first, you have to finish first)

The best way to see what'll happen, take some stock props to the pond with a pair of cupping pliers and start tweakin'.

Once you get to where you'd like to be, then take the numbers off the prop(s) and copy them over to a final one. Let me add to this, just because you've copied the pitch, rake, and cup numbers from one to another does not guarentee it'll be identical in the way it runs. It should be close, just not identical.

 

[shoboat]

Wayne,

Why would you keep backcutting the prop after you have all the cup that you

can pull? I think the trailing edge is the KEY to the propellers performance. I

find backcutting hurts you in the corners,and doesn't give you the BITE that

you need to perform well. Just a few observations from 16 years of testing

propellers.

Thanks,

Mark Sholund B)

 

[jaso]

Mark, so would you agree that once you have cupped the trailing edge that the best way to unload the prop again is to remove some of the toe( the part of the prop with the least pitch) ??

 

[shoboat]

Jason,

That is what I would do if it was me. We call the toe the tongue of the prop.

Thanks,

Mark Sholund

 

[apache5056]

One mans junk is anothers treasure.

This is why prop modifacation is a black art. I have not tested props for 16 years and I also admit that I am a newbie with props (2 years new). I'm sure Mark has forgotten more than I currently know. I would recommend taking his advice over mine.

 

[shoboat]

Hey Wayne,

I just want to know if you think backcutting works for a faster lap time? I

know when you backcut you can keep the RPM's up in the corner,but if you

check out your lap times,I think you will find out that it really does slow you

down a little bit. It can be deceiving though because your boat sounds faster,

but the lap times tell the truth. Also, too much cup will slow you down through

the turns to. It is a fine line for speed and acceleration from corner to corner.

It takes a lot of testing to get the right setup,that is why you need so many

different propeller combinations in your box. Believe me Wayne after 16 years

I am still learning a lot about propellers.

Thanks,

Mark Sholund

 

[Mike T.]

Here's a rundown on how to make a pitch gauge.

http://www.shark-racing.com/Ingles/Tecnica...doheliceing.htm

If you have any questions, e-mail me - I wrote the article.

There's something in the archives of MODELGASBOATS.com on how to make the prop mold (some folks would call it a prop duplicator).

 

[Guest_AMPBA 237]

thanks mike its just the ticket i wanted now all i ve got to do is fire up the mill and lathe many thanks guys its all very helpful and many others would appreciate gaining this knowledge as well there is a lot more to learn as 25 yrs dont mean much realy as you never stop learning about it.

 

[Mike T.]

One other thing - Did you find the tiny link at the bottom that takes you to the pitch conversion tables? Gotta have them.

 

[Guest_AMPBA 237]

left no stone un turned found all availiable info so far

 

[Chris Wood]

instead of back cutting the whole blade try a barr cut. a notch cut from the trailing edge to the hub, that way you still keep some of the trailing edge pitch.

just a thought.

 

[Joe]

Here is the link to make a prop duplicator.

http://www.modelgasboats.com/Home/Archives.../prop_mold.html

Joe Grace

 

[apache5056]

From some SAW testing on gas boats, we've found a 'V' type barrcut seemed to work and work real good. However, you have to keep in mind the props we tested on were the newer ABC line. The H-30 series (H-3016, H-3018, etc...). These props have a very large blade area to begin with which gave us a lot to work with.

We also found dramaticly cutting back the tongue area freed the engine which inturn keep the cornering speed up if not increased in. Especially when coming off bouys 3 and 6. It seemed to give the boat a sling-shot effect.

The down side to this story, the blades had a tendency to throw at high RPM's.

[This is/was a modified H-3018]

 

[Terry Keeley]

Looks like you need to heat treat them