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Aug 22, 2010, 12:16 PM
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Build Log

quick 'n dirty SEAGULL build


Some time ago, while i actually had to do loads of other stuff, i had an idea of how to make a simple bird-like steering tail for a model airplane. In order to make a tail move up and down aswell as rotate left and right, most ornithopters use elevon mixing, or just put one servo at the tailmount on top of another. I thought it should also be possible to convert the 'normal' back and forth servo-movement into a natural moving bird tail (without elevon mixing!).

i made a sketch, and then I couldn't help myself.. i had to build it.

I started with the mechanism itself. I am not a frequent model builder at all, but I love to do it. I had KYOSHO MINIUM gear inside an old broken gull-shaped plane i could use, and some scrap material..

once i put it toghether the mechanism seemed to work fine, so i wanted to see it fly! while working on it the propeller-feed-wire had broken of, and that was not something i could fix.. I decided to make it a sailplane, but i still really wanted to have that prop at least as an option. luckily I found somebody on the net who could fix it and put a plug in between! Then the body and the head were quickly cut from some pieces of styrofoam.

I glued two plugs underneath the wing, so it would fit and stick to the body.

the whole thing put toghther, and ready to go..!

a ground steering test...

..lookes like it should work..!

I had a maiden flight yesterday, and she was climbing fast! very unstable in the turns though, i think i have to finetune her a bit more. maybe the tail movement is to big, maybe the tail itself is too big, or maybe i'll add a small vertical stabiliser on the tail... that would be a shame though. any suggestions...?

I also ordered a small folding propeller, then some sanding, a modenst paintjob and then I'll have my very own mini electric sailplane / pet SEAGULL!

EDIT: in the mean time "quick 'n dirty" is no longer apliccable...
Last edited by Johannez; Aug 25, 2010 at 03:57 PM.
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Aug 22, 2010, 01:27 PM
Zen in the art of foam
djacob7's Avatar
Looking forward to the maiden!
Aug 22, 2010, 02:34 PM
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Crash & Burn's Avatar
how COOL !!!! Great thinking, Great use of things from around the house and Great workmanship. Congratulations on a neat project. Please keep us posted especially with a video.
Aug 22, 2010, 04:14 PM
if you see a weed, pick it
malakiblunt's Avatar
in the last picture its looking like a arctic tern

looking forward to seeing it fly
Aug 23, 2010, 03:56 AM
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Originally Posted by malakiblunt
in the last picture its looking like a arctic tern

looking forward to seeing it fly
..that's a beauty! I'll use it it as inspiration when doing the paintjob..thnx a lot!

still waiting for the folding prop to arrive. I ordered two different ones actually, and they were extremely cheap (4 euro's, incl shipping..!) so i hope they turn out to fit (and look like a beak) !
Aug 23, 2010, 10:38 AM
There's magic in those wings !
khaled_abobakr's Avatar
Hi Johannez

really nice project ... as for the instability in turns ... I suggest making the tail in a V shape but facing upright .. not inverted as you have it now .. also .. you may want to try narrowing the v angle of the tail ... try to get close the 90 degree...

All of these are just my personal thoughts .. and may not be based upon scientific basis

but why not making it a V-tail (elevon mixing ) with two control surfaces having an angle between them near 90 .. just like the ones shown in the video... I know you will lose the realistic movement of the bird tail ...but at least you will have stable turns with V-tail .. and this info I'm sure of because I've just received it from an Ornithopter Expert.. his name is Dr Kazuhiko Kakuta... aka Kazu Kaku... he is a Japanese doctor ...

Check the following videos of ornithopters with V-tail (upright) with really stable turns

Buteo V2 - Ornithopter RC with foamed polypropylene wing (1 min 57 sec)

080316 ButeoV 2 with foamed polypropylene (1 min 4 sec)

(0 min 20 sec)

(4 min 2 sec)

Good luck

Aug 23, 2010, 12:03 PM
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hey Khaled,

thanks for the suggestions! the elevon mixing tail would probably work just fine, but it's this rotating tail mechanism that got me started on this bird in the first place..! I'm trying out something else, something new, and my intentions are to make it work properly, before abandoning it all toghether.

as for the inverted V-tail thing, I build another X-twin-mod-seagull a few years ago, and my experience there was that an inverted V-tail was much more stable than an upright V-tial..!
also birds themselves hardly have any V-tail at all, its mostly flat. thats why i decided to shape it something like this.

btw, Kazuhiko Kakuta = a genious.. thanx!
Aug 25, 2010, 04:52 PM
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Well, I've been tinkering a lot, sanding the body and painting, (just the head and the wingtips) and made some adjustments.

inspired by the arctic tern i made the tail shorter, and added a small transparant vertical stabiliser, hope that works.

I've added some velcro to the headplug asswel as to the wing-base, so it sticks better, without the need of tape or additional parts to attach them.

and I've strengthened some vulnurable parts like the leading edge using wood-glue (!), deluded with a little water. I tried different things, but this seemed to work best, on depron aswell as on styrofoam. sanded it a bit, and then just painted the glue on it with a brush. when it dries it's completely invisable, while making it more sturdy and stiff, but still flexible without breaking. maybe even more tolerent to bending! I don't know how much weight it adds and it makes the surface feel a little rough, so i didn't glue-paint the whole thing.

did a lot of other minor adjustments, since there's nothin but thunderstorms outside... but she'll fly a straight line across my 5 meter-livingroom! i think she's ready.

Last edited by Johannez; Aug 27, 2010 at 10:02 AM.
Aug 25, 2010, 05:00 PM
you know you can edit your thread
Aug 25, 2010, 06:40 PM
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@ space; i know, why?
Aug 27, 2010, 10:01 AM
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the folding props have arrived!

they looked as cheap as they cost, but since i ordered a few, i tried to fancy one up a bit..

I doubt if it will work as good as the standard prop from Kyosho, but they are easily interchanged, so we'll see.

and, inspired by the thread on KFm airfoils,
(basically a wing wih a hard edge on top, creating an airpocket on the wing, supplying lift aswell as drag-reduction)

i decided to try and put some sort of 'rig' on top of my wing..

trying to make it as flimsy as possible made it look very nice and feathery.. all I have to do is wait for some nice weather..!
Aug 27, 2010, 03:30 PM
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thats awesome. good luck on the maiden!
Aug 27, 2010, 04:16 PM
Registered User
excellent job - it looks sharp and your internals respond, hope cg is good for madian - I been thinking about doing a bird far a while. Love your design I might try it... good luck ff
Aug 30, 2010, 04:36 PM
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did some testflights, but nothing that could be called a real "maiden". the weather doesn't engourage flying in wide open spaces, or traveling to them, and the city doesn't provide some nicely sheltered grassy hills either. dont want to bust her wings against some lamppost the very first time, so i'm waiting for a good park oppertunity. But apart from that, things look OK! cg looks good, she flies straight and stable. tin the meantime, I'm building a carrying box..
Aug 30, 2010, 07:59 PM
Lawn dart pilot/builder
Prime_8's Avatar
waitting , and fly in correct conditions is one o fthat hardest parts of this hobby . well for me . LOL

looks awsome , can't wait for flight vid if possible.

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