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Old Feb 21, 2007, 08:06 AM
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Build Log

My first attemt at DIY AP platform build - Jumbo-Stick


This is my very first attempt at building a model and I'm trying to create something between a SlowStick and a EZ*-like glider. I don't like SlowStick's inability to fly in any moderate wind so I decided to make wings with increased aspect ratio by enlarging the wing span while shortening the wing chord so the wing looks more like a glider. I didn't use the dihedral (SlowStick) nor folded wingtips (EasyStar) so I don't know what kind of roll stability can I expect as well as how will it perform in a stall/spin situation.

The wing is cut of styrofoam, strengthened with two balsa sticks and covered with foil. Two carbon-fiber tubes are built in each wing, they hold a short piece of thick steel wire which serves as a wing joint. Each wing is 1m long which gives total of 2m wingspan.

I planned to build stabilizers from depron but I visited a styrofoam factory and they gave us a piece (1m x 0.5m) of very strong and thin (10mm) styrofoam so that was used. Rudder and elevator are made of 3mm balsa ply.

Fuselage is made from light aluminium profile which has been perforated at the rear end to make it even lighter.

It has been test-flown (thrown) without the battery, motor and all the other electronics. We used a piece of wood instead to roughly balance it at estimated CG. It seems to glide very well and acts preety stable (what a pleasant surprise!).

It weights arround 900 grams now and expected weight with motor, esc, radio, batteries, servos and camera with it's mount is arround 1500 grams. Seems a lot, my preliminary calculations tells me it will take roughly 150 Watts of thrust power for this thing to fly. Will definitely use LiPos, don't know about which motor / prop to use yet.

It reminds of SlowStick but is significantly larger, so I choosed to name it "Jumbo-Stick".

I will keep you informed on my progress here and let you know if it flies. I'll document my success/failure here. Comments and suggestions are welcome.

NOTICE:
This is highly experimental craft. It has not been flight-tested and it is not prooven to be airworthy. If you are a total begginer (like I am) looking at making your own model using this as an example is probably a bad idea, there are many prooven better models out there.
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Old Feb 21, 2007, 04:46 PM
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Holy cow! You could use that for a hang glider! Can't wait to see it fly. Be sure to take some ground video. Nice build job! Your talents keep growing!
Got a question, why the slight curve downward on the wing? Will it flex up with wieght to straight? Just wondering. Usually they have some dihedral.
Old Feb 21, 2007, 05:47 PM
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That is not a slight curve downward. Wings are mounted straight inline each other but they flex a bit downward under their own weight. Not only does it straight up in flight but it flexes a bit upwards so there is a kind of slight dihedral on the main wing once this thing gets airborne. Wings flex only as much as foil lets them and they are reinforced with balsa to keep them from braking in half in case of overstress. Reinforced wings gives us a better performance envelope.

I sure will make a ground video of it's maiden flight and I'll post it here. Let's hope it flies
Old Feb 21, 2007, 06:22 PM
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It'll fly! Everything I have made has flown, even if one or two flew straight down, but it flew! LOL!
Old Feb 22, 2007, 05:33 AM
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He! He! LOL!

Straight down you say - let's hope this bird of ours doesn't meet a similar fate

This is a little bit offtopic but I just wanted to share it with you all. It's a video of my first steps in AP, greatly inspired by what I've seen here on RCgroups. It includes some photos of my very first EZ* build from RTF kit, some test-flights and one of my first onboard aerial videos. The music was borrowed from one of first AP/AV clips I've seen here. It was originally used in tnavressdog's "Remote Flight".

The video can be found here:
A dream come true (4 min 10 sec)
Old Feb 22, 2007, 08:21 AM
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They all fly but some only briefly.
Old Feb 22, 2007, 10:22 AM
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Hey Nesquik, in your video, (BTW, it's very good) at the 1 minute and 30 second area it shows, right after you take off, a sink hole or something like it. Is that what that is or an ancient small meteor crator? I sure enjoy your country side and all your videos.
Old Feb 22, 2007, 04:49 PM
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It is just a typical terrain configuration in this area. That wasn't a sink hole nor a small meteor crator.

I'll make a better video soon, this was just an test version but I released it on youtube since I can't find the time to make a final version lately.

I'm trying to mount a removable landing gear on my EZ* these days. Experimenting with a tail dragger configuration I found out that it is very non responsive on the ground, it wants to turn right with a full throttle. Perhaps the best solution would be to link a tail wheel with the rudder so I can have more control while taxiing/takeoff/landing. Any of you EZ pilots have some experience with that?
Old Feb 22, 2007, 05:28 PM
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Take a look at this! You might enjoy these mods.
https://www.rcgroups.com/forums/show...&postcount=140
Old Feb 23, 2007, 12:42 AM
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Quote:
Originally Posted by quailbird
Take a look at this! You might enjoy these mods.
https://www.rcgroups.com/forums/show...&postcount=140
I saw a Snoopy action figure sweeping with a tootbrush.
Old Mar 14, 2007, 11:11 AM
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Jumbo stick has been test flown at total weight of 2000 grams. It is powered by Jamara 600-class Venti motor (7.2V) and 7-cell 3300 mAh NiMh battery. At first we tried it out with APC 9x4,5 prop but it was underpowered and unable to fly. Then we replaced the prop with Graupner 8x4 and heureka - IT FLIES!!!

2000 grams is a lot and it climbs slow but we made new lighter wings (at the same size). After we replaced steel wires with carbon-fiber tube for a wing joint I discovered that the joint is very strong and it doesn't allow the wing to go in slight "V" (dihedral) under model's own weight. Flying wing that big without any dihedral and ailerons is very tricky. Once the plane banks too much it can be very difficult to return to level flight. I had a nasty crash while fighting it to regain control.

We redesigned the wing and added folded wingtips to improve roll stability and now it is very flyable. It's total weight has been reduced to arround 1600 grams while it's wingspan and aspect ratio remains. It flyes very nice and it's easy to control. It handles wind well, better than my EZ*! We are building a new extra-light styrofoam fuselage and hope to bring total weight down to arround 1200-1300 grams without a camera. Since I've flown it at 2000 grams total weight this seems promising - I think we've build ourselves a heavy lifter.

Jumbo-Stick is operational, I'll post some videos soon.
Old Jan 19, 2009, 12:09 AM
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Nice plane you got there! Keep up the good work.


God bless,
http://www.spurgeon.org/sermons/0174.htm
Old Jan 19, 2009, 12:52 AM
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In your video I like your Canadian t-shirt! O-Canada!

- Jeff
Old Jan 19, 2009, 11:12 AM
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Good looking plane! Now show us some of your great videos!


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