Tuesday, January 11, 2011

Mega Review: Art Applewhite Double Helix Monocopters

Art's Double Helix is new twist on the monocopter (pun intended)--it has two wings and flies on two motors. In fact, it's more or less two Helix Monocopters stuck end to end. Technically, it's not a monocopter but a bi-copter.  However, I will tag it like the single winged originals.  This post includes reviews of the 13mm, 18mm, and 24mm versions.

13mm Double Helix

Construction:
The parts list:

* Two 1/16" Basswood sheets
* One 24mm tube
* Two BT-5 motor mounts
* Two ¼" dowels
* ¼" launch lug

This build is exactly like that of the 13mm Helix Monocopter, there's just a little more of it. It only requires Elmer's Glue All and an X-Acto knife with a new #11 blade. Instead of repeating myself, I'll refer the reader to that review.



Finishing:
I have generally just been giving my monocopters a clear coat, but on this one I decided to paint one wing day-glo red and the opposing wing day-glo yellow. The body is still just clearcoated.





Flight/Recovery:
You form thrust rings with masking tape and friction fit the motors so they won't fall out. The motors should be oriented with their nozzles down. As with a Art's standard monocopters, you need a sturdy pad with a short ¼" rod (1" or so). Art provides plans for a suitable monocopter pad in the instructions. You will also need a clip-whip or a controller capable of firing two channels simultaneously since there is no way to twist those igniter wires together.

I flew the kit on two A3-4Ts ignited with a clip whip. It flew very nicely and went higher than its single-motored counterpart.

Unlike most of Art's monocopters, this model continues to spin until touchdown.


18mm Double Helix

Construction:
The parts list:

* 3/32" Basswood sheet
* 29mm tube
* Two BT-20 motor mounts
* ¼" launch lug



This build is similar to that of the 18mm Helix Monocopter so I also recommend the reader read that review. The build only requires Elmer's Glue All, and an X-Acto knife with a new #11 blade. Unlike the monocopter, you actually have to cut wood. One slab of basswood forms the two wings and balance beam. You also have to drill a hole in the beam so the lug can pass through it. This step is not that critical and you could just cut the hole with your X-Acto.

Finishing:
I have generally just been giving my monocopters a clear coat, but on this one I decided to paint one wing day-glo red and the opposing wing day-glo yellow. The body is still just clear coated.

Flight/Recovery:
You form thrust rings with masking tape and friction fit the motors so they won't fall out. The motors should be oriented with their nozzles down. As with a Art's standard monocopters, you need a sturdy pad with a short ¼" rod (1" or so). Art provides plans for a suitable monocopter pad in the instructions. You will also need a clip-whip or a launch controller capable of firing two motors reliably since there is no way to twist those igniter wires together.


I first flew this on two C6-5s, ignited using a clip-whip. Both motors fired, and the flight was fantastic. It was a really fast flight and was the highest of all my monocopter flights. Nice!

I wondered what would happen if just one motor ignited, so I loaded a new C6-3 in one mount and left the spent motor in the other. It flew just fine but with a lower altitude. And the motors are not even canted toward the CP/CG! This might be the safest cluster that I've flown.



24mm Double Helix



When I built the 24mm Double Helix, it was still in beta testing, so I never got around to submitting a review to EMRR.  Now that I'm lumping the Double Helicies together, it doesn't seem to worth my time to find the instructions to list the exact parts and document the simple construction steps.  The parts are the same as those listed for the smaller versions, except they are all bigger, and the build is identical to those of its smaller siblings.

Since this was beta build, the production model may vary (probably just in the length of components).  These changes could affect the flight profile.






Flight/Recovery:
I have flown the 24 DH three times on pairs of E9's.  The first flight was at NARAM-50.  After a wisecrack about mowing the lawn, the LCO pushed the button and the DH zoomed into the sky.  This was a really cool, high flight with ejection at apogee.   Ejection of one of two motors that is. One burned through so badly that it damaged the body and evidently the motor's ejection charge exited though the hole. The clay cap remained intact.  Nevertheless, it spun on the way down.

The 2nd flight at MDRA was cool, but it again experienced a double burn through. However, there was no additional damage. The spewing of propellant is actually pretty cool.

 The third flight was also at MDRA with a similar crowd reaction, flight, and aftermath.  This time
a lot of repair was necessary and the DH is semi-retired.


I'll re-emphasize that changes to the components could affect the spin rate and thus the 24mm Double Helix might not experience as bad a burn through as mine.