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Old Oct 08, 2006, 07:05 AM
certified n00b
San Diego, CA
Joined Jul 2006
162 Posts
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LAR Cootie :>

I built a cootie today. Actually, I built about 4, but I got ONE to fly. I couldn't find the plans for it, so I used the LAR method. Here's the goods:

Wing: 12.5" x 7.5" (0.5mm carbon fiber and wee bit of foam)
Body: 6" (2.5mm RCFoam)
0.9g plantraco rx
90mah lipo
micro act
6mm 4.5ohm DD w/aero ace prop

AUW - somewhere between 5g and 10g. I still don't have a scale that does 1g increments but when I put it on the scale, it flashes 5, then 10, then 5 (repeat).
I'd guess about 8g total AUW.

I managed two laps in my living room before I crashed, does this make it a LRF? I haven't fixed the wing on the post yet, it's just a friction fit. If I take this outside, I may need to do something about that.

I may now be superstitious. The first few cooties I just put together and didn't decorate. This one got some high-quality sharpie designs and everything worked first time. Must be some magic in that sharpie.
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Old Oct 09, 2006, 05:27 AM
certified n00b
San Diego, CA
Joined Jul 2006
162 Posts
I played around with the cootie a bit today. After a few more test flights in the living room, I noticed the little bugger wanted to turn in the direction of the battery. I tried moving things around a bit, but I realized that my mounting method was flawed. I had to mount the rx+battery perpendicular to the frame to get the left/right balance straightened out. After a few more test flights, I was able to do left and right loops and managed a figure eight in the living room as well.

I'm not sure this profile fuse is going to do it for me. I really don't like having the connectors and wires just sticking out on the sides BEGGING to be yanked out :/ Maybe I could revisit putting the RX and lipo on the side of the fuse and use motor thrust to even it out? I'm also wondering if the plantraco RX+bahoma lipo just isn't the 'right' setup for this thing.

For kicks I put together a smaller version using the same wing and a 4mm DD with the piccoz prop on it. Without a rudder, I managed to get the plane to stay in the air and perform left-handed turns cause of the oversized lipo (90mah). Maybe with the smaller lipo the motor may be able to keep it aloft and climb?

-Jef
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Old Oct 09, 2006, 08:21 AM
charle
charlelombos's Avatar
Sydney, Australia
Joined Sep 2004
78 Posts
nocjef,

good 2 hear that you could do 2 laps . My cootie only does a gentle glide on full throttle! what is your angle of attack in degrees on the wing and does your motor pointing up or down slightly?
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Old Oct 09, 2006, 04:38 PM
certified n00b
San Diego, CA
Joined Jul 2006
162 Posts
I just pulled out the protractor and measured the AoA - 12degrees
I didn't measure this when I was building, I just looked at the pictures and the angle looked about right The motor I had to play with a bit. on the flying version, I have almost no left/right/up/down thrust at all. If there is any bias, it's probably pointing about 1/2degree of downthrust (motor + prop is point UP)

I'm still worried about yanking one of the connectors out with the way everything is setup. I'm not the best flyer and my models definately show that. I'd like to get this down to the 4mm DD so I could fly it in the house, but I'm sure my battery is just too heavy to make this practical right now.

I really need a proper place to fly inside. Still looking for some San Diegans that want to take over a gym

-Jef
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Old Oct 10, 2006, 08:01 AM
Registered User
Texas, Plano, USA
Joined Jan 2005
810 Posts
Bob selman carried the plans on CD if you want the official version.

at www.bsdmicrorc.com
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Old Oct 10, 2006, 10:59 PM
certified n00b
San Diego, CA
Joined Jul 2006
162 Posts
I checked bsdmicro, but I didn't see them listed. I'm pretty confident that I got it right since I got a few of them to fly around the living room. I don't dare test this one outside, in the wind, in a breeze, or even with a fan blowing. At about 8g, this thing would be a goner :

-Jef
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Old Oct 11, 2006, 12:00 AM
Plantraco's Avatar
Saskatoon, Canada
Joined Jan 2003
2,235 Posts
You can protect those wires on the fuselage if you tape the wire to the fuse with little squares of blenderm. You can also poke 2 4mm holes in the fuselage, and then wrap the wires between the holes before plugging into the receiver - it keeps them out of the way.
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Old Oct 11, 2006, 12:03 AM
certified n00b
San Diego, CA
Joined Jul 2006
162 Posts
When the RX was mounted flat on the fuse, I would use tape to hold the wires down and all was good. When I re-trimmed the model and moved the RX so it was perpendicular to the fus, the CONNECTORS were more likely to hang up on anything nearby.

I basically mounted the RX on a small piece of foam in a T fashion to get the weight of the battery into the middle of the fuse. The picture I posted was from the constant left-hand-turn version

-Jef

(ps. Am I ever getting my RX back from Plantraco customer service?)
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Old Oct 11, 2006, 12:36 AM
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Saskatoon, Canada
Joined Jan 2003
2,235 Posts
Quote:
Originally Posted by nocjef
When the RX was mounted flat on the fuse, I would use tape to hold the wires down and all was good. When I re-trimmed the model and moved the RX so it was perpendicular to the fus, the CONNECTORS were more likely to hang up on anything nearby.

I basically mounted the RX on a small piece of foam in a T fashion to get the weight of the battery into the middle of the fuse. The picture I posted was from the constant left-hand-turn version

-Jef

(ps. Am I ever getting my RX back from Plantraco customer service?)

I see. Sideways receiver eh? I guess that does put the weight in the middle. I am surprised that the weight on one side really affects that Cootie that much.

Regarding your RMA to Plantraco - better check customer service because I don't know who you are, or anything about your RMA. ie: I doubt you ordered with your RCGroups alias name right? We are busy with filling Carbon Butterfly orders - so maybe service is slower right now?
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Old Oct 11, 2006, 02:20 AM
certified n00b
San Diego, CA
Joined Jul 2006
162 Posts
The cootie really seems to want to be balanced on the L/R plain. AUW of the model was only about 8g. If everything is square and true with the ACT, pager, and wing, that would leave an extra 4g or so on one side of the fuse (that's close to 50% of the total weight hanging on one side of the plane!). Needless to say, this puts the model into a constant left-handed turn.

The proper plans seem to have a larger RX on one side and the lipo on the other side to balance out the model. Maybe I could find a way to do the same thing with the 0.9g rx by making a space for the bahoma magnets to connect through the fuse?

I'm still playing around with this. My hopes it to get the smaller 4mm DD setup working so I can use it as a LRF. I think I need to shed a bit of weight first, though.
If I switch to the 50mah full-river I have, maybe...

4mm pager 0.5g
RX 0.9g
50mah lipo+bahoma 1.8g
hingeACT 0.3g (with connector)
Body+wing ~ 2g

That's about 5g. Could be a bit too much for the 4mm DD. I could probably get the weight of the body down if I used a better covering material, smaller carbon fiber for the spar, and sand down the foam to 1mm or so and reduce the size. We'll see how things go, I'll be revisiting the small version over the next few days.

-Jef
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