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Nov 03, 2006, 07:20 PM
Victoria Super Mortem
UBILDIT's Avatar

Yes But...

You are absolutely right about everything you posted. What I dont understand is if I did this all evenly on all the parts, why did it seem to take a disproportionate amount of weight in the nose to get the cg close. Even at almost 3 oz of lead weight, the cg was still nowhere near the leading edge of the bottom wing. It at least moved forward from just behind the rear of the servo in the bottom wing to in front of the servo which was still over an inch from the leading edge.
I put GWS Pico's as far forward under the canopy as I could. I did however use small wire and tubing to run the elevator and rudder surfaces. I also built up the turtle deck area with the light spackle so it would be more rounded, and I did use a lot of it, but I am sure that did not even weigh as much as 6-8 grams. I even put a heavy duty LG system just behind the firewall and gobs of hot glue to hold it in place and to help bring the cg forward.
I guess that since Bipes are naturally tailheavy, making anything heavier than it has to be must multiply that tendancy geometrically rather than just by the added weight itself. Does this theory explain it.. If so, I guess I just answered my own question.... LOL..

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Nov 03, 2006, 07:38 PM
Dismembered Member...
arx_n_sparx's Avatar
Bo: There's a lot more surface area behind the CG than ahead of it. Because the nose is much shorter than the tail, it takes a lot more weight there to get things back into balance. I believe we tried to diplomatically tell you not to do this, but.....

Weight is always the killer for us - we need to keep things as light as possible. EPP doesn't look the greatest up close, but it sure does the job without needing any strengthening.

Nov 05, 2006, 07:09 AM
Flashmeister Aviation Inc
MrFlash's Avatar
Thread OP
Soz for not posting guys but just come back frok my summer (??) hols...cheers for the post Si.

Yup seems like the CG is a little far back, and the extra weight might be adding to the probs (is it 19oz with lipo included? ) . The CG on mine came out approx at the aileron servo on the plans .

U can shift it back for more 3D ish kinda flight or keep it forward for more stability but you get to a point where the 3D CG becomes to tippy. Easy way to spot it is that it becomes very twitchy, wont bank over in an aileron turn (just sorta k/e's with its nose in the air) but does killer loops .

My gear isnt super lightweight , just yer average shocky setup, the lipo weighs about 2 oz and the motor about 1 1/2 oz so the weight of the finish on all that area may be adding a bit more than we first thought like the fellas say.

Rather than adding more weight, try moving the motor mount a little further forward..not as complicated as it sounds. Just remove the motor and add an extra bit of 9mm / 18mm epp or whatver to front of the firewall and remount the motor . This will add nothing to the weight but give you a bit extra to help thre balance.

What are the actually probs you get when its flying. If its down to more than one thing a couple of simple fixes might help whilst its in the hangar ??
Nov 09, 2006, 03:52 PM
Registered User
I'm building one in 6mm depron.
How do you guys get the batteries in and out? Can't seem to figure out a way to get to the "lipo cutout" part of the plans (off course i've only checked this after i glued in the servos ).
Do you think it would matter if i place the battery below the lipo cutout on the plans (so i can make a hatch in the fuse to load/remove battery's)?

Anyway, thanks for the great plans. I always wanted to build an ultimate.


Nov 09, 2006, 04:47 PM
Flashmeister Aviation Inc
MrFlash's Avatar
Thread OP
Hi Jonathan,

Heres a close up. Just cut a slot in one side of the fus between the horizontal formers to the length of your battery then put some foam end stops inside to stop the lipo sliding inside the fuse. The battery is also secured with velcro.

I put the battery there to keep the weight around the centre (thrust) line but it shoulnt matter to much I suppose. You can easily change it if it is dosent work out ok

Hope this helps & happy building
Nov 10, 2006, 04:15 AM
Registered User
oh, "lipo cutout". Now i get it . My mind always seems to look for a way to complex solution.

Nov 10, 2006, 05:40 AM
Ham Call Sign: KK4KGJ
Buzz Bomb's Avatar
Nov 10, 2006, 08:40 AM
Victoria Super Mortem
UBILDIT's Avatar

right Now!

Right now it wont' fly at all because it's only recognizable pieces are the tail and both wings which I saved. The rest of it I tore apart with my bare hands so I could get the guts out of it and put them in another attempt without all the covering etc... The first one will be bluecore jsut for giggles then we'll see. Going to go way light on this one.. Thanks for the help. Hope you had a good time off.

BTW Each spackled, sanded and covered wing weighs close to 3 oz. Way to freakin heavy...Live and learn I always say..

Nov 10, 2006, 10:59 AM
Registered User
Just came back from the maiden. Everything went great. This little plane really floats nice and slow. On low rates i think i could almost use it as a trainer .
I was kind off nervous for the maiden because this is only my second depron build plane but it flew like a dream. Big grin now

auw is 320 grams or 11.2 oz
motor is a cheap gws brushless
battery: flightpower 800 mah 3s
no need for a landing gear as i fly behind my house in a field with looooong grass.

Thanks again for the great plans.
Nov 10, 2006, 11:11 AM
Victoria Super Mortem
UBILDIT's Avatar


Could you take a picture of yours from the side? I'd love to see how you placed your wings. That thing looks great.

Nov 10, 2006, 11:42 AM
Registered User
I went with the very technical and high tech method of "this looks about right" to place the top wing
Nov 10, 2006, 11:44 AM
Registered User
just need to find some sort of canopy (dettol comes in a completely different bottle in belgium sadly). Any idea's on how to fabricate a nice looking canopy (love the tinted green canopy btw).
Nov 10, 2006, 01:42 PM
Victoria Super Mortem
UBILDIT's Avatar

Spray Bottles

I used a bottle of Simple Green de-greaser for mine. Just find any spray bottle and hold it up beside the canopy area to see if it will make a good fit. Mine was a little big, but I cut it down and made it fit well. So just try anything that even looks like that other stuff and see if it's close. Wish I had pics of mine.
BTW, love the rudder on yours. Also, it looks like your top wing is slightly forward of the bottom wing and that the bottom one is swept back and the top one is straight or more so than the bottom. Is that how it is or was it just hard to tell in the picture.?? Both my top and bottom wings are swept back and the top one was a good bit more forward than the bottom one.
I am so perplexed by how mine flew that I want to do the best things everyone else has had success with so my next one wont be a dog...LOL...
Thank you so much for the side view picture, it really helped.

And, Mr.Flash, thanks for the update on where the CG was on your model. I've got my bluecore version all cut out and the fuse is ready for electronics install. I'll move the servo's even more forward than I did on the last one and that will certainly help.

You guys are awesome.. Thanks again.

Last edited by UBILDIT; Nov 10, 2006 at 01:43 PM. Reason: forgot
Nov 10, 2006, 01:52 PM
Registered User
mode1's Avatar
Nov 10, 2006, 02:21 PM
Registered User
Both the top and bottom wings are swept back and yes the top wing sits about 0.5cm-1cm before the bottom wing. I really think this plane is best build as light as possible. Mine floats about at a speed slightly faster than a walking pace.
Super plane for 7$ of depron.

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