“Tubeless” video how to- motor mount rubber band Helicopter and AirBrake recover method

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neil_w

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That was extremely clear, and I never ever would have guessed how that all worked until you made this video. So thanks.

The whole contraption is really quite clever. Do you have a count of how many of these you've made? It seems like you've been through a lot of design iterations.
 

BABAR

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Probably 75-100. They are satisfying and entertaining. I think I found my "niche" or at least one.
 

Rktman

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Thanks, since I'm a "show me" vs a "tell me" guy so this video explains a book's worth.
 

Gus

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Hi, very clever model, great explanatory video.
Are the blade hinges simply at 90 degrees or do they have an angle of incidence to them?
Blades did not seem to have airfoil to them. Was that just for this demo model or is that how you make all of them?
What do you think the advantage is of a tubeless design?
Do you have any flight videos?

Again, thanks for sharing the unique design.

Steve
 

mbeels

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Very clever! And nice video.

I wonder, are the band displacers necessary? I see what they do, but I'd also guess that the ejection charge would sufficiently pressurize the inside volume of the rocket and kick the rotors out to get that started. But they're also rotor stops, so might as well use them for displacers. (unless it is your tube-stops).
 

kuririn

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Very ingenious, sir.
Any problems with scorching of the blades on your flights?
 

BABAR

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Hi, very clever model, great explanatory video.
Are the blade hinges simply at 90 degrees or do they have an angle of incidence to them?
Blades did not seem to have airfoil to them. Was that just for this demo model or is that how you make all of them?
What do you think the advantage is of a tubeless design?
Do you have any flight videos?

Again, thanks for sharing the unique design.

Steve
Thanks!

I put 5-10 degrees NOSEWARD dihedral on the rotor stops forward edge, meaning the hinge rotates past 90 degrees, so 95 to 100 degrees from launch position. This is so that, with or without motor retention, the rocket post deployment orients nose UP. My first choppers were the opposite, with hinges rotating LESS THAN 90 degrees, these were all without motor retention, and descent was nose DOWN. Which still works. I went with nose up for two reasons.
First, my nose pyramids (equivalent of nose cones on other rockets) are paper, and they get scrunched after a number of nose tip first landings.)
But second, no matter which way nose is oriented, when rocket touches the ground the rotors are flexed TOWARD the ground. BUT, if it hits nose DOWN, that flexion is in the same direction as the rubber band tension. The combination of landing stress AND the band tension frequently broke the blades. On the other hand, if the nose is UP, the band is pulling the rotor UP, but gravity is pulling it DOWN. so the bands actually act like shock absorbers and the rotors don’t break.

No airfoiling.
ALL of my Helis and Airbrakes are flat planar blades or rotors or brakes or whatever you want to call them.
Occasionally I will round the FINS on the forward and lateral and trailing edges relative to launch/boost phase, but sometimes I just leave them flat. But the rotors or blades are just flat balsa pieces.
four reasons
1. I am lazy and airfoiling is a lot of work.
2. These are sport rockets. I fly in a local park. I just want my rocket to come back down safely and look cool, preferably WITHIN the park and not some neighboring yard or street. so i don’t need them to be any more efficient.
3. There is a trade off with airfoiling EXTERNAL BLADE helis like these (as opposed to what seems to be the major current competition chopper, with blades held inside a cylindrical standard rocket tube on boost and pushed out into the airstream at apogee. My flat blades when folded in deployment make close to a perfect square. It has corners, but otherwise is a pretty simple exterior. If I airfoiled the blades, it would be difficult to get them to form such and even external contour and I would expect more drag on boost.
4. Even though flat blades are inefficient, most of my birds have FAR much more rotor surface area than most other helicopters out there. If fact, I came up with the AirBrake concept when one of Helis didn’t spin, just came down flat and smooth and nice as you please. In most cases, in fact, even with ZERO pitch, because at deployment all the fins are on the “same” side of the rotors, either counterclockwise or clockwise, they still rotate. The challenge in fact has been to come out with a design that DOESN’T rotate.

Advantage of tubeless design? Once I decided I didn’t have the patience or skills for competition, and I don’t have any issues with motor eject, a tubeless design is a natural. If I don’t need a tube, it is just extra weight, both during boost and during recovery. Not a LOT of extra weight, and I have some more RSO correct models that can retain the motors, although they don’t all use tubes.

Flight videos
Do a TRF search under BABAR

Gyskelion
whopper flopper chopper
Sundancer
DareDevil
Dandylion Seed
swirly
Twirly

And thanks again for your kind words and interest!
 

BABAR

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Very ingenious, sir.
Any problems with scorching of the blades on your flights?
Yup. That’s what the Mylar tape on the inside is for.
 

BABAR

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Very clever! And nice video.

I wonder, are the band displacers necessary? I see what they do, but I'd also guess that the ejection charge would sufficiently pressurize the inside volume of the rocket and kick the rotors out to get that started. But they're also rotor stops, so might as well use them for displacers. (unless it is your tube-stops).
Since most of my designs incorporate rotor stops, and some of my original designs just had the bands lay flat, sometimes opening and sometime not, I found the dual use of the rotor stops to displace the direction of pull greatly increases the reliability of deployment. A plus (for me:)) is that it kind of adds a cool factor, like the rigging of a ship. Probably also costs a bit in extra drag, but again since these are not for competition, no biggie.

Going “tubeless” does have an additional cost, the ejection charge is forward, not outward. So without a tube, and without the band displacers, there is essentially zero opening force when the posterior retention bands release, because the pull bands are “pulling” forward, not outward. If the rocket still has forward momentum (and it almost always does, motor ejection almost always first slightly before or after apogee), the aerodynamic force will keep the rotors CLOSED. This happened with one of my Spyder video camera rockets even WITH BAND dispacers, epic boost flight, perfect motor and ballistic recovery, all onboard video. Really sad.
 

BABAR

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Hi, very clever model, great explanatory video.
Are the blade hinges simply at 90 degrees or do they have an angle of incidence to them?
Blades did not seem to have airfoil to them. Was that just for this demo model or is that how you make all of them?
What do you think the advantage is of a tubeless design?
Do you have any flight videos?

Again, thanks for sharing the unique design.

Steve
On you first question, I may have misunderstood.

All my rocket I put in some up or down dihedral to “force” the rocket to come down nose up or down (currently I prefer Up.)

On my Helis, I cut the hinge at least 5 degrees pitch down, to force a spin, and usually try to set it so the blades rotate with the fins on the Trail edge (so fin edge of rotor is Up.)

Once in a while I screw it up, and the rotors rotate with fin side forward. I like @kuririn ‘s style of Avant-Garde. But spinning with fins forward just looks too weird, even for me🤪
 
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