Brock KB2 - McCullough or Rotax?

[BrianInVa]

You can get a new standard Dominator frame kit (Rolling Chassis) from Dave for about $6k just add motor, prop and rotor blades....

Mine looks like it will weigh about 400 to 420lbs empty with a 503 and dragon wings....

PS. you should move the stab on the tail to the middle of the vertical surface....

I’m assuming the frame in the photos above is an Air Command? Like this:

PS. you should move the stab on the tail to the middle of the vertical surface....

Yes, definitely part of the plan. And I can use some of the hardware from the tail on this frame to accomplish that.

 

[GyroChuck]

Looks like a good deal. The rotor head alone used to go for $500. Seat tank another couple hundred.

That's not an Air Command.

 

[BrianInVa]

Looks like a good deal. The rotor head alone used to go for $500. Seat tank another couple hundred.

That's not an Air Command.

Oh ok. Any idea what it is?

Edit to add:

Butterfly Ultralight gyroplane?

 

[Doug Riley]

It looks like a hybrid of an Air Command Elite (the one with the Larry Neal high-rider mod), and an early Butterfly. Note the Butterfly logo on the instrument pod. Larry designed both, so no surprise that there's some cross-breeding between the brands.

The Butterfly and the Snobird both are Air Command derivatives.

Later Butterflies (or Butterflys?) were loaded with cool accessories, including a better tail than this lightly modded Air Command tail, G-force landing gear (this one looks purely rigid) and a powerful prerotator that Larry called the Metro-launch. This craft also has a belt redrive and what looks to be just a tiny electric prerotator.

 

[Kevin_Richey]

I just found a bit more modern frame on Marketplace.
The sellers father built it in his garage but never completed it. They had no idea of it’s worth, put a price of $1000 on the ad but said to make an offer.
I offered $500 and they accepted. So at a minimum I have an upgraded rotor with prerotator mount, an unused fuel seat tank and a decent motor mount for my 582. I might just use it instead of the Brock KB2 if it seems it would be a more stable design.

Great price, Brian!

 

[Aerofoam]

I’m assuming the frame in the photos above is an Air Command? Like this:
View attachment 1162211

Yes, definitely part of the plan. And I can use some of the hardware from the tail on this frame to accomplish that.

This one looks much better than the other one, I would put a tall tail on it, make sure everything else is ok, and call it good....

 

[BrianInVa]

cool accessories, including a better tail than this lightly modded Air Command tai

This one looks much better than the other one, I would put a tall tail on it, make sure everything else is ok, and call it good....

I picked up a tall tail off Marketplace on Thursday. With parts/ hardware from this Butterfly Ultralight tail, modifying my tall tall with a raised hs should be fairly simple.

 

[BrianInVa]

G-force landing gear (this one looks purely rigid)

I wonder how hard it would be to add some type of simple shock absorption to the landing gear on this one?


I had already bought 15” tall 6” wide tires and wheels with hydraulic brakes so those should go well with this frame.

 

[Vance]

I found as I gained flying experience my thoughts on what needed improvement and why changed.

As I teach people to fly I find that some learners may have a challenge with what might be considered a weakness in a particular design when others have no problem with that aspect of the aircraft.

Based on what I have learned I would be hesitant to change some aspect of a design until I had more flying experience and I would make an effort to change one thing at a time so that I could see how it affected me and my perception of how a particular design flies.

Many knowledgeable people have tried a tall vertical stabilizer/rudder with the horizontal stabilizer located in the propeller blast only to find they preferred a low horizontal stabilizer and a short rudder and vertical stabilizer.

I personally prefer a tall vertical stabilizer with a separate rudder and the horizontal stabilizer below the propeller blast and yet I love the way the American Ranger flies.

I learned to fly in a Sparrow Hawk but found I didn’t manage the change in the effect of the rudder and horizontal stabilizer well when I would reduce power to land.

It was less of a problem as I gained experience.

I like a near center line thrust gyroplane and yet a Magni M16 is one of my favorite gyroplanes to fly that has a thrust line close to a foot above the center of gravity.

A Magni M16 also has the horizontal stabilizer well below the propeller thrust line.

I have modified my aircraft (The Predator) carefully over the years and not every change resulted in an improvement.

Even seemingly small changes can make a big difference in how a gyroplane flies and responds to pilot inputs.

A gyroplane is a system that works together and in my opinion there is no prescription for a gyroplane that flies well for a particular pilot.

Everything in aviation is a compromise and there is value in understanding how the compromise affects the aircraft as a hole and how it responds to your inputs.

I am a flight instructor with experience in many different gyroplane and with many different pilots.

I am not an aeronautical engineer.

 

[Sv.grainne]

Some don't:

 

[BrianInVa]

I picked up the Butterfly gyro frame today. This thing is huge compared to my Brock, and far nicer than I anticipated.


An older neighbor came over right as I was getting ready to leave.

He said this was a fully functional gyro and his 70 year old neighbor used to fly it out of the field behind his house regularly. The neighbor apparently wasn’t mechanical or a tinkerer so he probably bought it completely assembled.

He said the owner passed away recently and while the house was vacant people broke in and stole everything. Including the engine, rotor, main landing gear wheels and tires, instrument cluster, all control cables, and even the seatbelts off the gyro.

His daughter didn’t want anything to do with her father’s estate and just wanted the gyro frame gone. She didn’t think it was worth anything since it was stripped so she took the first offer for cash I made. She didn’t even show up, just said it was in the garage at the address given and to transfer the funds .

Amazingly enough, a full size gyro frame will fit (sorta) in a Ford Crown Vic.

 

[Aerofoam]

I picked up the Butterfly gyro frame today. This thing is huge compared to my Brock, and far nicer than I anticipated.
View attachment 1162230

An older neighbor came over right as I was getting ready to leave.

He said this was a fully functional gyro and his 70 year old neighbor used to fly it out of the field behind his house regularly. The neighbor apparently wasn’t mechanical or a tinkerer so he probably bought it completely assembled.

He said the owner passed away recently and while the house was vacant people broke in and stole everything. Including the engine, rotor, main landing gear wheels and tires, instrument cluster, all control cables, and even the seatbelts off the gyro.

His daughter didn’t want anything to do with her father’s estate and just wanted the gyro frame gone. She didn’t think it was worth anything since it was stripped so she took the first offer for cash I made. She didn’t even show up, just said it was in the garage at the address given and to transfer the funds .

Amazingly enough, a full size gyro will fit (sorta) in a Ford Crown Vic.
View attachment 1162232View attachment 1162231

I have the same trailer that's in the background, except it is barely used and has a solar power system and AC.....

 

[BrianInVa]

Today I arranged an even trade - the Bensen rotor, rotor head, Mac prerotator and motor mount, and the flight controls off my Brock KB2, for a 24’ Dragon Wing rotor that has zero time on it.

And I found the type of prop I’ve been looking for on Barnstrormers, a Powerfin B type three blade 64” prop that came off a 582 in pusher configuration. I like the wider B type blade and was disappointed when I had heard Powerfin had gone out of business, as this was my original first choice for a prop. I think the lesser weight will be easier on my B gearbox than an equivalent sized Warp Drive prop too.

So I’ve got all the major components collected or being shipped now for this Butterfly build. Now I just have to get everything put together and looked over by someone who actually knows what the heck they’re doing.

 

[BrianInVa]

We assess rotor size by a figure called "disk loading." It's simply the gross weight of the gyro divided by the area of the rotor disk. This latter number equals rotor radius x rotor radius x 3.14. We'd like this number to be at or above 1.1. 1.25- 1.3 is a good compromise for small gyros.

Example: 600 lb. gross weight, 25-foot rotor. Rotor radius is 12.5 feet. 12.5 x 12.5 = 156.25. 156.25 x 3.14 = 491 sq. ft. rotor disk area.

Disk loading is 600/491 = 1.22 -- just about perfect. That plate on the gyro stating that the 22 ft. rotor can lift 600 lb. is optimistic!

Just an update - I brought home the Butterfly Ultralight model gyro frame this weekend. I’ll use the Rotax 582 I have now and I’m trading the Bensen rotor, Brock controls, and Mac prerotator and motor mount even up for a zero hour 24’ Dragon Wing rotor.

I figure total weight of this Butterfly Ultralight with heavier Rotax and larger Dragon Wing rotor will be closer to 280 to 300 pounds than its original part 103 weight. I’m 280 clothed with helmet etc.

So figure 580 / 453 = 1.28 disk load. This is a decent number then judging by your post?

 

[Doug Riley]

IIR, Ernie Boyette of Dragon Wings liked about 1.3 lb./sq. ft. Mike Boyette might remember more precisely than I do.

I ran the 28-foot DW's on my tandem Dominator at more like 1.1 when flying solo -- so there is some tolerance there.

There's some tradeoff between power loading and disk loading -- for a specified level of performance, higher disk loading requires lower power loading (i.e. more HP), and vice versa. "Performance" in this case means rate-of-climb. A good rate of climb is beneficial, not just for the thrill factor, but also as a safety measure.

Don't forget fuel weight when doing this math.

 

[BrianInVa]

IIR, Ernie Boyette of Dragon Wings liked about 1.3 lb./sq. ft. Mike Boyette might remember more precisely than I do.

I ran the 28-foot DW's on my tandem Dominator at more like 1.1 when flying solo -- so there is some tolerance there.

There's some tradeoff between power loading and disk loading -- for a specified level of performance, higher disk loading requires lower power loading (i.e. more HP), and vice versa. "Performance" in this case means rate-of-climb. A good rate of climb is beneficial, not just for the thrill factor, but also as a safety measure.

Don't forget fuel weight when doing this math.

Thanks. I’m hoping this stock 582 will be adequate to get started.

But if it needs rebuilt anyway prior to flying it, it might be worth the extra expense necessary that the rebuilder in Florida claims he can get up to 80hp out of one - reliably. Are there other Rotax rebuilders claiming similar results?

 

[Jazzenjohn]

The stock engine for the ultralight butterfly was an MZ 202. They aren't very easy to come by and the Rotax 582 is better. The napkin calculation of what is enough power is thrust in pounds being approximately half the all up takeoff weight or slightly more. I'm sure the 582 would easily be enough. Have you begun taking lessons yet? Taking lessons has an added benefit of being around gyro people and the chance to absorb information about what gyro might be the best fit for you.

 

[MikeBoyette]

Thanks. I’m hoping this stock 582 will be adequate to get started.

But if it needs rebuilt anyway prior to flying it, it might be worth the extra expense necessary that the rebuilder in Florida claims he can get up to 80hp out of one - reliably. Are there other Rotax rebuilders claiming similar results?

Stay away from that rebuilder. PM me for details. Vast experience myself.

 

[BrianInVa]

Have you begun taking lessons yet?

I’m still working on my sport pilot certificate locally. I should have it completed in a month or two. Then I’ll travel for gyro CFI time.

I did visit the Carolina Barnstormers a month ago and learned a lot and had a great visit with Barry and the gang down there. At that time I was still planning to modify the Brock KB2 I had picked up in September. I hope to get back down there once I have most of my Butterfly assembled. I’ve already exchanged texts with Barry and he said they recommended a couple upgrades including a tall tail and wider main landing gear and larger better lifting rotor than my Bensen rotor.

I still haven’t located any local gyro owners and the my flight school manager wasn’t aware of any here in northwest Virginia.

 

[BrianInVa]

Stay away from that rebuilder. PM me for details. Vast experience myself.

Ok thanks. PM sent.