Potential power plants...

Potential power plants...

Babe Bee, Dragonfly, QRC, OS PET III.
The Cox engines all all 40+ years old, the OS Pet about 60!

While pondering over the choice of engine (I spend a LOT of time pondering), decided to check out another long-standing thumb rule.

"5oz and 100sqin for a Babe Bee"

So I built this.
20" x 5" wing, 7" x 2" tail set 2" back from wing TE.

From previous experience I learnt that trying for a good smooth finish adds so much weight that it defeats the model's purpose. So this time only two coats of dope and cornflour mix, with inadequate sanding, and two coats of acrylic spray. Ignore poor finish.
54gms so far.
With tip weight, covering and Babe Bee, hope to be just under 5 oz.

Incidentally, here's a simple way to jig the wing for a warp free build.

Cut two wingtip rib blanks (end plates) of length equal to the chord and height equal to the airfoil thickness (5"x 3/4" in this case.)
Don't cut the rib shape, leave them rectangular.
Attach a rib to each, ensuring identical alignment.
Pin the bottom spar to the building board, add end plates.
Attach LE and TE with appropriate packing.
Add ribs. Add top spar after installing control system in the centre bay.
Carve and sand end plates, LE and TE.

Side by side, the Nobler sure looks like it needs a 09!

The wee one is 100 sqin, 65gms. So 4.5oz with Babe Bee and 8cc stunt tank.

Decided to power the Nobler with the OS PET and keep it for myself.

Sent the smaller model to my young friend.

Making a crush proof box was almost as hard as making the model!

The weight just crept up on me!.
At least it doesn't need and tail ballast, balances 1/4" behind LE.

A lot of effort down the drain, I fear...

"A lot of effort down the drain, I fear..."

Not really, You gained a lot of knowledge and experience. I am sure you now have a list of both what different to do and what not to do.

Looks good, fly it and let's see a video.

@Free Flight

Those two I already had 

What I need is 6lb balsa...

Regards
Iyer

Looks good, just fly it. Should amaze you despite more weight than you wanted.