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Kamov Ka52
Kamov Ka52 body on Hirobo XRB

This is the first prototype of a Kamov Ka-52 Alligator body I made to fit the Hirobo XRB tethered helicopter. This one is made from vacuum formed 20 thou High Impact Polystyrene, with balsa wings and tailfins. The final all-up weight in this configuration was 191g, that is the same as tethered XRB with a training gear fitted.

This first prototype used the existing landing skids, rather than the more accurate wheeled gear. This was to simplify the mounting process, and reduce the number of variables.

More Photos

Front View (88KB)

Rear quarter view (154KB)

Prototype wheels (16k)

It Flies !! (16k)

 

 

The Maiden Flight

The maiden flight was interesting! The heli needs lots of trim with this body, the tail throws the balance way off, and without a battery pack to adjust the balance I had to resort to sub-trim. I also kept it low to the ground (to reduce damage if I lost control) but this made it very skittish in ground-effect. Once I got some confidence with it and got some height, the heli started to settle down. Yaw was very variable, and sideways cyclic was slow. However once I got the nose down it was clear that the fuselage, wings and fin were doing their job and gave a nice weather-vane effect. There is a photo above to prove that it did fly.

Second Prototype

The next step was to start work on the landing gear. The KA-52 has a semi-retracting gear, which folds backwards into recesses in the body. I modified the plugs to have simple recesses and built a wire undercarriage from bend piano-wire. The rear section was going to be mounted on the back of the XRB main motor unit, while the front wheels mount below a tongue extending forward from the motor unit. Above is a photo showing how this arrangement looked from the outside (using a scrap body shell). A retract servo was not fitted at this stage. I think it looked promising.

Conclusion

After a few more flights it became clear that the wide body (compared to the rotor-span) combined with the large wing area were catching the down-draft and causing a lot of turbulence. This was especially noticeable near the ground, but also made yaw more difficult.

Other folks have tried similar bodies (KA-50) on the XRB and reported similar handling problems, so I decided that it was probably not worth pursuing this design. But it has given me some valuable experience and a few other ideas.

 

Last Updated: 22-June-2006