Lumenier RB2205C-12 2400KV SKITZO Ceramic Bearing Motor
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Old Apr 17, 2007, 09:05 AM
romranger is offline
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Build Log

My First Foam Scratch-Build "Wisdom"


Wanted a primary trainer since I killed my slow stick (twice!) and didn't want to pay the price of a new one. I took ideas from two plans, the STC trainer (which is a "flattie") and the STS Seaplane (which has a full fuse). I have resisted going to foam because (to my way of thinking), they just don't look enough like a "real" airplane to satisfy my imagination. Well, I have been won over! The pics have construction notes attached to them. Here's the specs:
Wingspan 40in
Wing Area: 280 sq in
Wing Loading: 8.23 oz in sq
All Up Weight: 16oz
Fuse Length: 30in
Airfoil: Kinda clark-y ish
Chinese Turbotrix Motor, about 80 watts or so
Castle Creations 10 esc
Batt: either a kokam 2s1p 1250 or a common sense rc 3s1p 1250

Material is Elmers Art board that can be had locally at JoAnn's for $1.97 a sheet. When the paper backing is removed, the foam is about 4mm. Final design can be built with two sheets. Paint is "Painters Choice" sun yellow latex acrylic. My weight budget was ok, so I experiemented with using several coats. Decorations are a combination of full sheet printed stickers and inkjet decals and good old "sharpie" art. Since all high-wing cabin planes look like a Cub to me, I added the "Cub" sticker to the tail. I would have added an "almost Cub" sticker, but I'm not talented enough to draw one. Maiden flight will be when the winds in Euclid drop below 8mph or so.

Depending on the maiden performance, I may add two CF rod struts to help support the wing or a second wing that is open and creased (like the slow stick wing) for more lift.

What do you think guys? This is what happens when I get cooped up with high winds and no extra money!
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Old Apr 17, 2007, 10:06 AM
critterhunter is offline
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Good job! I've heard a lot of buzz about this plane in other forums.
Old Apr 17, 2007, 11:28 AM
romranger is offline
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Thanks, critterhunter! I did have to resize the STS fuse and wing to fit the 20x30 foamboard, but much props to the original designer, Charles Pirkey.

https://www.rcgroups.com/forums/showthread.php?t=372857
Old Apr 17, 2007, 02:34 PM
nubee 1 is offline
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Well Critterhunter This is somewhat like the one I'm playing with.
Still waiting on the new hot glue gun. These babys will fly in a pretty good breese as the video's show.

romranger
Which EMax motor is that? I have 2 differant KV ones 2822 & 2212
Thinking about the 2212 so I can use a smaller prop. Like the stronger wing. I built a set somewhat like yours that will go on "something". I used a 1/2" wide piece of FFF for a spar. Keep us posted how your "Cub" flies.
Old Apr 17, 2007, 03:47 PM
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It says CF2822. Static thrust of 11oz on 2cells and 18oz on three cells with eflite 11x4.7 prop and prop saver. I'm drawing a little over 7amps from the batt.
Old Apr 17, 2007, 08:00 PM
OhioPete is offline
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Looks nice, hope it flies well for you.
Old Apr 17, 2007, 08:23 PM
nubee 1 is offline
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romranger
I have a liteweight Slow stick I have an EMax on and just wondering what it will do. Guess its time to finish the wing and give it a try.

Ken
Old Apr 17, 2007, 08:25 PM
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i like the logo on the rudder!
Old Apr 17, 2007, 09:23 PM
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Nice! Looks like you've got a "helper" checking things out in the one picture
Old Apr 17, 2007, 10:25 PM
romranger is offline
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Yeah, that's my office manager, Cletus. This little black and white female cat follows me around the house just like a puppy! Interestingly enough, this was actually supposed to be my wife's cat. Go figure!!
Old Apr 19, 2007, 06:39 AM
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Wisdom did not fly well. The spreader bar on the landing gear broke on the first landing (should have soldered it instead of using thread and CA). Could not get the CG far enough forward for the kind of relaxing flight I want in a primary trainer due to the former and batt tray design. Strapped another battery outside on the nose using rubberbands and was able to trim it and flew down a battery. Adjusted computer endpoints to minimum and added lots of exponential and now flying ok, but winds came up quickly and had to quit. Wing is fine, but plane is now waaay too heavy for my purposes. Came home and did a rethink on the fuse. This is what I came up with: Coroplast from an old sign for tail feathers and a single hollow CF rod running fore and aft underneath the middle joiner. Rod end at tail with two 1/2 x 1/4 in balsa sticks, hollowed out and glued together around the rod. Stab mounts to top of resulting 1/2 x 1/2 square surface with the fin mounted on top of the stab. Moved fin forward to allow elevator to be one piece. Recut sides a full two inches shorter in height. Front of CF rod into 3/8 x 3/8 hardwood stick which will insert into a firewall sandwich made from the foam and two 1/32 in ply sheets. Upgraded motor to a eflite park 370. Preliminary balance looks good. Tail feathers are stable without using CF rods (and all that Gorilla glue). Will finish in a day or two.


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