Blades vs. Prerotators

[Brian Jackson]

Hello all.
I have a couple of questions I'm hoping to get answered at Mentone, but also would like to pose here. I'm about to begin a new GyroBee construction, but learning everything I can in the process to make this a quality build AND a safe ship. Thus, nothing is getting "modded" or altered from Ralph's stock plans.

I do however have a question that involves 2 components working collectively. I've read that the Dragon Wings are fantastic, lightweight blades, but will require a prerotator due to their difficulty to hand-start. As such, their weight savings and cost are offset by the necessity of a prerotator.

I've also read some great reviews from Ralph and others regarding the performance of the Vanek Sport Rotors which are heavier and more expensive, but are much easier to hand-start. Here the extra weight and cost are offset by not requiring a prerotator.

I'm sure opinions are as varied as the machines themselves. But since I'm ignorant of many of the design nuances that go into developing a safe, practical ultralight gyro, I value everyone's input.

Didn't Vanek at one point employ a very light "hand crank" prerotator mechanism on their Rotor Lightning model in the late 80's?

Respectfully,
Brian Jackson

[Ralph]

Brian,

Flying without a prerotator is only viable where the single biggest concern is shaving weight - usually a Part 103 issue. Most blades will hand-start (some easily, some requiring a more athletic push), at which point you work the blade speed up by taxing around until they are moving fast enough to start your takeoff run. This can be fine at a light-traffic strip where you will only occasionally have to deal with other aircraft. We hand-started for years when operating from a private grass strip (= almost no traffic), but even there we eventually worked up various approached to mechanical prerotation just to make life easier.

It can range from inconvenient to downright dangerous as the airport gets busier. There is nothing more frustrating, once you have the blades going, as:

(1) Getting stuck in a line of aircraft waiting to depart

(2) Having to hold, where blades speed will decay unless the wind is just right, in the run-up area while another aircraft comes floating in on a long, slow final.

You can get away with it at a gyro fly-in because everybody knows the problems, but airports will not cut you a lot of slack in the general aviation world. If you are going to operate from a typical municipal or county airport, you should have both a prerotator and a radio.

Prerotators do increase the complexity of the craft and its cost. The cost increase is pretty trivial compared to the entire aircraft and the gains in operating convenience and peace-of-mind are beyond price. Several systems have been devised around recoil mechanisms from Rotax engines and even hand-crank systems like the old Vancraft. These are a lot better than nothing and are particularly effective with blades that start easily. Electric systems tend to be a step up in terms of performance.

However, for putting the pedal to the metal and just flying, it is hard to beat an engine-driven system, be it Wunderlich (flex shaft), solid-shaft, or hydraulic. I think any gyro pilot should be able to manually spin up his/her blades, but unless you have a VERY specific need to save weight and are flying in a low-traffic environment, you really should think in terms of some kind of prerotator.

Ralph

[Brian Jackson]

Hello Mr. Taggart.

Thank you for the great insight. I've been leaning toward using a prerotator on your GyroBee design. I don't mind the added complexity because safety is paramount for all of the reasons you mentioned in your reply, and cost should not factor into any equation where safety is a variable.

My objective is to stay within the Part 103 weight limits. Thus with the inclusion of a prerotator of any variety, it would seem the choice of using Ernie Boyette's light but efficient Dragon Wings blades would be a logical one. The only other additions/mods to my stock Bee would be a small anvil (for my aerial horseshoeing work) and an antique printing press... :-)

I will be attending this year's Mentone PRA gathering on Friday. I would be most interested to see what other GyroBee builders are using on their machines successfully. If by chance you will be attending that day, it would be an honor to meet you. I'll be the guy with the funky looking camera rig.

Thank you again.

Respectfully,
Brian Jackson

[Ralph]

Brian,

Sorry, but I will be there on Saturday - lots of conflicting family stuff with both Don and myself on other days.

However, since you are just in Niles, get your buns up to the ASC KIMO nationals in Three Rivers over Labor Day weekend and we can compare notes.

Ralph

[Brian Jackson]

You got it! I'll be there.

[PW_Plack]

Brian,

The "armstrong" prerotator you mentioned was on the older Vancraft gyros built by Jim Vanek's father, Chuck, before he closed Vancraft. Jim's company, Sport Copter, builds machines with a similar shape to the partial cabin, but a totally different airframe and rotorhead design.

The old Vancraft Rotor Lightning had a Rotax 503, partial cabin, and hand-crank prerotator, and still came in 4 pounds under the part 103 limit, but the welded steel frame was lighter than Jim's newer bolted aluminum designs, in fact, unnervingly lightweight-looking if you're used to the newer stuff. The armstrong prerotator would spin the Vancraft blades to about 70 RRPM if you were in good physical condition, according the the old-timers nearby.

My understanding is that Ernie Boyette has modified the Dragon Wings slightly within the past couple of years to make them easier to hand-start. Perhaps Mike B. will pop in here to confirm.

You really need to get hooked up with John Landry, "gyropilot" here on the forum. He started with Part 103 intentions, and kept improving until he wound up with about the most decked-out 'Bee there is. He has radio, transponder, upgraded suspension, the works. He says the machine is down for the season for an engine rebuild, but I heard a rumor he's actually working out the center-of-gravity issues related to his addition of an aft lavatory on the 'Bee. ;)

[gyropilot]

He says the machine is down for the season for an engine rebuild, but I heard a rumor he's actually working out the center-of-gravity issues related to his addition of an aft lavatory on the 'Bee. ;)Damnit Paul... you weren't supposed to talk about that before the official unveiling next year!

John L.

[MikeBoyette]

Dragon Wings are hand startable, however it takes some finesse. Most people that have tried in the past use the brute stength method. This does not work well. The method we use is a more of a rhythm ( no pun intended)than strength. With a light wind and some patience it can be done. My question is why? A Prerotator should be standard equipment unless you are trying to stay part 103. Then I would suggest finding my Dad at a fly-in and have him show you how to hand start them.

[Dean_Dolph]

Brian, by now you are aware of the manual pre-rotator that was being demonstrated by Tim Blackwell at Mentone.

It was indicated that they hope to have all the bugs worked out in 6 months or so and available in one way or another to the gyro community within a year. While I have/use a digital camera occasionally I prefer prints so won't have my Mentone pictures back for a week or so but when I do I will post pictures for everone.

[Glenn D]

Brain,

When was the last time that You spoke to Dana @ Staree? He's just finished puting together an electric prerotator for his Gyro that he plans on distributung. The last time I spoke with him was at least three weeks, Give him a call, see what the weight is on it? I think he still wants to go part 103 with his Gyro, But I'm not that sure.

Glenn

I'll BE ordering my kit sometimes this December.