Prop Tech 101/ a group effort.....

[Ian Inverarity]

I use a linisher (a belt sander attachment to a bench grinder) to trim and sharpen my props. I use the underside (unsupported side) of the belt to sharpen the props with 40 grit, finishing and sharpening then balancing with 100 grit. An old (blunt) 100 grit belt can be used to get a good finish before hand sanding with 400 wet/dry, using water.

Sharpening with the linisher can be tricky, and needs a bit of practice. Even after years of doing this I still occasionally ruin a perfectly good prop by over-sharpening a tip. But it enables me to get the leading edge thin and sharp.

The hand sanding is the most dangerous part for my fingers tho, particularly for 3 blade props. One slip and my finger goes into a leading edge, which is pretty sharp at this time.... So I am very careful! :

I use a Topflite magnetic balancer. The cones on the shaft are a little big to easily do 3/16" bore props, but are fine for 1/4". I dont go overboard chasing perfect balance tho, life is too short! I reach a point where I say "close enough"! ;D

A while ago there was some discussion on the rcboat.com listbot about jewelled balancers which are much more sensitive, but these sound like they create a lot more work!

Nitrocrazed racing: I have seen certain people use props so out of balance the strut bracket broke..... ;D

 

[Russell Bear]

Is it really that big of a deal to get the props with a mirror image? I understand the need to atleast smooth them out, but is all the polishing overkill? It seems to me that the blade thickness and the leading edge being sharp is much more important.

Thanks...

 

[Randy Rapedius]

High polishing your props is not only a waste of time, it also slows down your boat. Yes, they look pretty but there is too much slipage. Ask Andy Brown. 120+ MPH tells it all. I finished over 400 props last year. One of my props set the 21 hydro SAW record 99.9 MPH. Satin finish is the way to go.

List of importance.

1. Balance

2. sharpened and thinned blades

3. finish

Have fun ...................... Randy

 

[Russell Bear]

Thanks Randy.....

 

[Slideblues]

Looks like the jury is goin satin folks

Next up a few safety tips while workin on props,

Gene ;D

 

[_laxmasta2039]

satin huh...does this mean i should go back over TB's job with 400 grit [right now it's alot like the ones in the picks, just a little less polished] ? i've also got a p215 that came with the boat, made of berylium i think [whatever the silvery-colored metal that props are made of is] does this apply to them too?

safety tip- never hold the prop in your hand while working on it! get a small c-clamp, epoxy some rubber to the tips, and hold the prop that way.

Joe

 

[Slideblues]

Joe try it both ways, if its polished, try some 400 grit on it and run it again, thats the fun part, trying something out and seein how it works. Silver color is Stainless,

A quick note on safety from Mike T.

This post will give ya some ideas of the many different ways to mod props, opnions will be different on the ways and methods, just like any other sport.

Grab up some and get ta wackin, and have a little fun while your doin it.

Add a prop guard to your boat stand and ALWAYS if the engine is runnin STAY away from that spinnin little bugger ya just spent so much time on.

Gene ;D

 

[_laxmasta2039]

thanks Gene,

i'll do a little sanding on the really polished parts of the TB 215, the other one is used and already "satinized" by the water i also noticed that the one TB did is a little cupped and much better sharpened than the stainless one- if you ever need a prop and Tunnelbill has some for sale, get one!

Joe

 

[Ron Olson]

Thanks for the answers to my questions. We went through this briefly last year about the polish or not to polish. I like to have a nice looking prop hanging off my transom because an oxidized one just doesn't look good after putting so much work into an otherwise well detailed boat.

Randy or others, do you think that a satin or rough finish helps to aerate the prop to give it a little slip to get the revs up?

 

[Slideblues]

Had a clip up from last year but speeds have changed a bunch since then, I think Randy is on the right track with the satin finish, My results were each averaged for best run with each prop. Difference between the finishes was tenth's.

I used outboard tunnels, hydro results may differ.

Gene ;D

 

[_laxmasta2039]

okay,

i went back over TB's job armed with 400 grit wet-or-dry...felt like i was commiting a crime while doing it but when i finished it looked fine and it feels pretty good to be able to say i "modded" my own prop [hey, sanding it counts!! ]

Joe

 

[EatMyShortsRacing]

Ian,

Now you wouldnt be suggesting I had an unbalanced prop??? LOL

Well those X665s are pretty bad from the factory!!!!

EMS Racing

 

[Ian Inverarity]

Gee Craig,

I wasn't going to mention who it was, but now you have incriminated yourself! I am surpised that boat still has a transom.... ;D

You should have seen the 1967 I returned to place of purchase recently. The hole thru the hub was not even straight! :

Nitrocrazed racing: Never use an unbalanced X470/3 on a 3/16" shaft. Dont ask...

 

[EatMyShortsRacing]

Ian,

OK I have to ask about the 470/3

EMS Racing curiosity killed the cat... lucky I dont run cats anymore..

 

[Ian Inverarity]

Craig,

My first petrol mono (a Kingcraft of course) I bought a X470/3 off a friend who had already sharpened it. I assumed he had balanced it too, but that was not the case. I built the boat with a 3/16" stainless steel stub shaft, when I started it up I gave it some revs and there was a big bang and the motor stopped dead. The prop shaft had bent about 45 degrees and the prop hit the rudder bracket, bent the strut and folded one fo the prop blades stopping the motor. That would have been at about 14000 rpm, the shaft bent 45 degrees at 14000 rpm in less than 1 revolution. If it weren't for the rudder bracket the shaft would have bent until it snapped and the prop would have flown off....... Still scares me to think about how close that was.....

Nitrocrazed racing: I'm allergic to spinning props.

 

[waterbug]

Hey Guys,

Did anyone happen to notice that the prop section in RCBOAT.com has been DISCONTINUED !!!!

It contained exact degrees and specific dial indicator measurements for championship winning props !!! It had all of the 50 series props and gave measurements on the hughey gauge , it also had the mile- per- hour and rpms.

It also had the 40 series for 3.5's to make exact duplicates of his championship winning props.

DID ANY ONE HAPPEN TO DOWN LOAD THE SPREADSHEET ?????

If so can I get a copy??????

I had it on file but lost it!!!! I made a copy of the 50 series, but need the 3.5 40 series PLEASE !!!!!!!!

 

[Slideblues]

Say What?

Somebody give me a link to it.......

Gene ;D

Nevermind I found it, I will email Marty and see whats goin on....

 

[EatMyShortsRacing]

Hey that info would be handy..

if you guys find it please tell me...

EMS Racing

 

[Slideblues]

Marty just mailed me back, seems he lost the supplier for the prop duplicators that the chart referenced to.

Gene ;D

 

[waterbug]

There was a section on his winning props that he gave all the specks and they were on the hughey gauge ! I have the 50 series in my hand !!