We recently installed the brand-new Whirl Wind prop on our F1 project and took a few pictures along the way to show how we torque and safety the all-important captured prop bolts. You’ll find this same arrangement in most popular constant-speed props … bolts that have to be turned in sequence to draw the prop on to the hub. You work your way around—or in our case, with one person on each side, each person works three bolts. When all the bolts are snug and the prop flange is tight against the flywheel (which is hopefully tight against the crank flange), out comes the torque wrench.
Unfortunately, most torque wrenches don’t quite fit into the confined space with a simple crowfoot wrench head. But you can buy (or weld up) a short wrench that will mate with your torque wrench to get the bolts up to torque. If you put the elongated “crowfoot” at 90° to the torque wrench and aim for the center of the torque range, you’ll end up right on. Work your way around the bolts (count to six …) and you’re ready for safety wiring.
Murphy’s Law states that “anything that can go wrong, will”—and a corollary says that at least one (if not several) prop bolts will end up torqued such that the roll pin that accepts the safety wire will be pointed right at the body of the prop hub. Fortunately, Murphy never met the surgical forceps—use a curved-tip forceps to reach in and grab the end of the safety wire and you can pull it right out. With some careful planning, you can do all of your “twisting” on the “easy” side of the bolt. Note that we like to use Safe-T-Cables for this task (shown). It is a quick and easy system—if not a particularly cheap one. If you do this a lot, it’s worth it; if not, then classic safety wire can be used with the same forceps trick.
Something that was pointed out to me years ago by a prop shop is that any scratches or grooves worn into the hub by safety wire can be used as an excuse to scrap the hub at overhaul. Not one to take chances, I always run a piece of nylon tubing over the safety wire where it contacts the metal of the hub. Cheap insurance!
One of three finished safety wire jobs on this prop! Well, actually Safe-T-Cable … but however you secure the prop bolts, take your time, use the right tools, and do a good job.
Timely, Paul! Just hung the new prop on a certain RV-14 (re)build, as in, last weekend. Have been playing “who wants to go first” on safety wire. Thinking we will look into the Safe-T-Cables, which I had forgotten about.
When performing this aggravating task, I start with .020 wire to get a sense of how long/in what direction/etc… After one or more tries, I then graduate to .032 wire, which my Hartzell manual calls for. I am happy not to move on to .041 wire, which the FSDO required for my initial airworthiness inspection in spite of it not being called for in the factory manual.