Trimming Propellers

NEW222 Wed May 19, 2021 8:38 pm

Hi all. So I was just wondering about trimming propellers and how to properly do it. I do have a couple of 6" propellers that have little nicks/chips out of the tips that I was wanting to cut down to say a 5" propeller. If you have done this, what have you used or done? More off an experiment and for fun, but will probably run these propellers, especially when I am teaching others in case of, well, you know... Smile

Thank you.

DanMc Wed May 19, 2021 11:15 pm

For larger props, I have a tool that is made by Jim Lee out of Topeka, Kansas that has a center mandrel and a scribe that adjusts through it. Set the scribe to the radius and mark both blades. I don't know how feasible it would be to make a tool like that for small props. I would find a piece of tubing or rod that is a nice fit into the center hole. Then just measure with a good ruler out to where you want to cut it off at, or make a mark to sand it down to. Then of course, re balance it .
Type at you later,
Dan McEntee

balogh Thu May 20, 2021 1:02 am

One prop trimming expert here is Brad aka 1/2A Nut who trims 5-ish props to 4+ ones and manages to crank TeeDee049...051 speeds to near 30k. No brainer but I think immaculate balancing after trimming is crucial to maintaining vibe free performance. I had some second hand crankcases on TeeDees that came with excessive radial wobble that made engine start almost impossible due to poor sealing along the shaft. Unbalanced props will eat the crankcase bore quick, visible by greyish goo oozing around the shaft end from the prop drive plate gap..

944_Jim Thu May 20, 2021 1:15 am

Hi Chancy,
First thing first...go Bruins! I saw the FB post with your team emblem (Oilers, if I remember right).
A friend and I snuck into the old Boston Garden during the last OT period of play between the Oilers and Bruins...the one that went into triple-overtime, and advanced the Oilers (ISTR 1993...I moved south in '94). We got into the balcony section right over/behind the B's goalie, sat down, remarked about the patches of melting ice, and watched the Oilers put the puck in the B's net! This had to be the shortest hockey game I watched live, especially since we missed all the regulation, and first 2+ OT periods.

Anyway, what Mr. Dan says is best...especially if you want to build up a tool chest and fly bigger models.

I heard for our little ones that nail clippers (not scissors) do a great job of trimming prop blades down. Get the bigger toe nail clippers to cut the prop blades, and balance the prop. There was a thread several weeks ago discussing variiuos ways to balance them. There were a few DIY tools for the job being discussed.

Take care!

gkamysz Thu May 20, 2021 9:17 am

I put a rod (which fits the shaft hole of the prop nicely) vertically in a piece of wood. Clamp that to the disc sander table and trim that way. If doing this with an APC, make sure you understand how their prop holes are made.

1/2A Nut Sat May 22, 2021 11:50 am

I like using tape to establish the shape of the first blade and
transfer to the second blade. I choose back cut for speed,
reshape the trailing edge to taper following the airfoil to
recover a thin trailing edge.

andrew Sat May 22, 2021 3:16 pm

The magnetic balancer shown in pic 2 above is the best I've used. With 1/2A props being relatively small and lightweight, anything mechanical usually has too much friction to effectively balance my props.