Tee Bee

I just ordered some 6x3 and 4.2x4 APC props in hopes of using them on my .049s. I see that Tim Wiltse uses the 4.2x4 on his Skyline series of engines and have one of those on order. When I got them, I saw that the shaft holes in the hubs are too big for .049 engine shafts. The 4.2x4 looks like it's at least 1/4" diameter and the 6x3 are 3/16" diameter. How are folks adapting these props for .049 use? Custom made bushings or is there another common, easy trick? Thanks.

eroc144

My Feedback: (1)

Simplest way I've found is to use a 1/8" length of fuel line as an insert. Slips right over the screw and snugs things right up.

EG

rc2007

To this day I can't figure out why apc makes the holes too big on their .049 props...make no sense. Master airscrew makes them perfect.

Tim Wiltse-RCU

Tee Bee,

The old fuel line trick works well. No worries though as your Stage 3 will come with one APC prop adaptor! It works with the APC 6x3 and if you flip it around works with the 4.2x4.

Later,
Tim

Jim Thomerson

Kustom Kraftmanship sold brass tube adaptors. Don't think they are still available. Fuel line works also.

Andrew

APC uses a continuous strand glass reinforcement -- the large hole is necessary in the production process. MA also builds glass reinforced props, but the strand length is shorter. The difference is similar to building laid up fiberglass boat hulls or car bodies vs. using a chopper gun to spray chopped glass strands and epoxy.

APC's process produces a much stiffer propellor -- it doesn't depitch in the air and has little flex, but is more prone to breakage on landing. MA GRP props will depitch slightly, but are less likely to break on landing due to being more flexible.

During extensive testing, I've found I'm capable of breaking any prop currently in production.[:'(]

combatpigg

My Feedback: (3)

I never understood the reason completely, but the manufacturing process is why the hole is so large. The question is why can't they furnish adapters that actually fit the most likely engines that those props will get used on?

dennis

My Feedback: (90)

Jim,
Campbells Custom Kits had been selling nicely made brass bushings for the APC props. Several to a package for a reasonable price. I picked mine up on the bay where he sells under the tag lil red riding hood. Don't know if he still has any but if anyone needs them it might be worth looking into.
Dennis

Tee Bee

Thanks for the info, everyone! Looking forward to the new motor, Tim.

Raymond LeFlyr

My Feedback: (2)

I too use those nice brass bushings from Campbells.

Hey Tim, would you bring some of yours on the 29th to sell please. Do you have props, engines, and all your other goodies too? Wouldja huh?

MJD

My Feedback: (1)

The recess molded in the rear of an APC prop is accurately centered, as it is formed in the mold which would have been CNC cut. Because of the long fibre reinforcement molding a small center hole is very problematic. The old "you don't get something for nothing" problem. They chose to make rigid long fibre reinforced props and deal with the through hole in a post machining operation as I understand it. The through holes are drilled after molding, and this is why they are sometimes horribly inaccurate. I found this out after calling APC to ask why they looked so inaccurate - they actually admitted the through drilling procedure was prone to inaccuracies, although I see no reason why their fixturing could not be improved.. production "efficiency" I suppose.

IMHO you should almost never use the through hole to index your prop to the prop bolt/shaft. Yeah, many of them look bang on, but I have many props in my collection where you can see the eccentricity from 6 feet away after three beers. APC advised, and I agree, that the smart way to center the props with a bushing that fits snugly in the molded recess in the rear of the hub. Problem is, you have to make them yourself or rely on an aftermarket manufacturer to set you up.

Sure, for many sport uses they are accurate enough, gosh-knows thousands are used daily in that manner. But on a small, high revving light weight 1/2A or so engine proper centering is paramount.

My two bits.

MJD