The Broadway Bod Busters
The new C Speed prop by Bob Whitney. Ken Burdick photos.
New C Speed prop
By Ken Burdick
Yes Folks, it's true.
Longtime speed flyer Bob Whitney decided to up the ante a bit for C speed by designing and making a new prop for the event.
A bit of background might make things more interesting.
The C speed event is led in record by the Nelson .40 long stroke. The engine made its debut in the pylon events and was quickly accepted by most as the engine to use. As such, there has been more fiddling with this particular engine than the others available. Possibly the closest competitor might be the OPS .40. Props for this event are a little scarce because most of the speed usage for the mighty Nellie has been Formula .40 which is a standing start acceleration event, C speed is a top end only event. Because of this, the props for the two events have different requirements.
Richard Shannon currently holds the fastest C Speed times (plane pictured at right), somewhere around the 190+ mph range. The prop Shannon used was one he bought from Tim Gillott. When I asked Dick what size it was, he told me the pitch was greater than 8 inches."
I have had my best runs so far, using a 8 x 8 made by Steve Wilk of Dominator props. The best Louie and I can figure is that it was in the mid-180 mph range. The engine was wound up pretty tight so it stands to reason there is more engine left on the clock than the prop allowed us.
The prop pictured is an unfinished 8.5 x 8.5 and is the first pull from the mold. Made with lots of carbon fiber and the correct epoxy, this baby has promise. Finish work will be critical so the blades will be thinned a bit while keeping the all-important pitch profile under control as material is removed. The hub will be checked to ensure the prop does not tip and is at a right angle to the thrust washer of the engine. This can be tricky so a brief explanation may help.
Here at the BBB lab, we mount the prop on the engine, mount the engine on a solid fixture and then solidly mount a depth gauge so that as the prop is hand rotated, it just deflects the gauge when the blade comes around. If the prop is at an angle, it will deflect the gauge more on one blade than the other. A very small amount of material can then be removed from the hub to correct the angle the prop hub is tipped to. When all this is complete, both blades will be tracking closer to the same.
We are currently out of contests here in the Northwest, but the props will be finished, tested and ready for use by Spring of 2015. With a large diameter of 8.5 inches, there is lots of room for tweaking to your particular engine.
Let's hear from the Hippie!
Martin Higgs aka Fast Hippie has done some in-depth testing between the two Nelson .40s, long stroke vs. short stroke. While I do not have Marty's specs for you, he is now convinced that for the Formula 40 speed event, there may be an advantage in using the short stroke engine!!!!!....OMG, just when you think it's done and there is a go-to engine, something like this shows up. This is not to say that you can just pop in a shorty and win, the prop will change somewhat and this is where the Hippie shines. Meanwhile, the rest of us are still trying to get the most out of our Long Strokes, so we'll wait and see what Marty cranks out.
To get prices and availability for Bob Whitney's new prop contact him by e-mail.
This page was upated Oct. 31, 2014