Last minute change for Design Contest plane.
 

I just don't have time to do justice to my Bobcat so I put it on the shelf. This is my bipe I originally started for the contest, I have to go with it for now.

I've got the fuse 80% done, the wings need ailerons, I laid up the cowl, bent up the LG, intalled the motor. I need the vertical fin, windscreen may be clear or I may make it out of wood.

The plane with out the motor weighs about 6 oz., so it should be 10 with the motor. I shooting for 18 oz. flighing weight.

Last minute change for Design Contest plane.
 

and....

Last minute change for Design Contest plane.
 

and...

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Looks fabulous from here... Get it flying! We've got a few days left....


phil in austin

Last minute change for Design Contest plane.
 

Gotta love that round cowling! And semi-elliptical wings to boot...looking GOOD! :D

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VERY sweet wing planform... elipses rule!

Andrew

Very cool!
 

If you've not already named it, you should call it the StaggerThing! hehehe.

Last minute change for Design Contest plane.
 

It looks really cool. :cool:

Those wings definitely add a lot of character.

I was a little disappointed when you switched to the Bobcat because I was looking forward to seeing this plane. I'm glad that you're going to build it. I still want to see the Bobcat too!

Don't forget to update your contest page.

Last minute change for Design Contest plane.
 

The Bobcat is just on the back burner, I'll try to have it done by June, but I got a boat to sail from VA to NJ, and my Dad's in the hospital in Indy, it looks like I'm going to go there, last time it was for two months.

Sounds good, I'm terrible at naming things.

This is what I did last night:
I think I first saw LG built like this in an Andrews H Ray. These don't pullout, but they're a pain to cover around. To build it you first cut three 1/8" plys about 1 1/2" tall by the width of the fuse, then the middle one is cut to allow the 1/8" LG wire to form a v or u with in that space, you then sandwich them together using epoxy or thick CA with the LG wire buried in the center.

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This is another view LG.

Notice that even though the plane has a round cowl I'm using flat sides. I made the firewall cut away behind the engine for cooling, but left the firewall round on the other side to help hold the cowl and I'm going to run the fuel fill line out the back on the left side.

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Sitting on it's LG.

Last minute change for Design Contest plane.
 

I LIKE it. Very classic looking. And simple to build with the all sheet wings.

I hope it's not a problem but the tail surfaces look a trifle small for the wing area. Especially the vertical. Time will tell I guess. Watch for dutch rolling tendencies or any tendency for it to fall off to one side or the other during climbs. Or unexplained snap rolls during high speed pullups.

I'm temped to follow in yer footsteps. Something compact like this would be a perfect "motorcycle model" to go on the back of my bike so I can get two hobbies in during one Sunday morning. What's the span?

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man thats a nice model!

If you want to check the tail surface size is OK, I can post the formulae on here (depends upon the wing area, tail moments) from my book on designing model airplanes. Also some good stuff on bipe setup.

Andrew

Last minute change for Design Contest plane.
 

Thanks. Yea, if you're going to make sheet wings why not elliptical, they're hard to build otherwise.

It spans 24", I think it's 200 sqs.

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OK, thanks that would be cool. :) :)

Last minute change for Design Contest plane.
 

Simplifying things here are some basic formulas:

Vertical tail surface area (rudder and fin combined area):

Area= (K x Wing area x MAC)/Dv

where: K is a constant = .22, the MAC is the mean aerodynamic chord length in inches and Dv = vertcal tail moment arm, which is the distance from the CG point to a point 25% back from the vertical fin MAC.

Rudder area from 30% to 40% of total fin area is recommended as minimum.

Horizontal fin area (elevators and hor.stab surface combined):

Area = (K x MAC x Wing area in sq. inches) / Dh

where K= .52 for semi or symetrical wings, .57 for flat bottom wings and.60 for undercambered wings

Dh is the tail moment arem, measured from the CG to the 25% point of the MAC of the horiz. stab.

I hope that made sense... I allways add between 10 and 20% to my surfaces for extra stability and increase my moveable surfaces that same amount as I like to have lots of control authority!

AJC