Hi everyone,

Not much activity on the forum, so I thought I’d share what I’m doing.

Early this year a young member got interested in Control Line flying.
After spending a small fortune on hardware and paid instruction, he managed to solo a SkyBee.

About then I’d posted a thread http://www.rcindia.org/fuel-and-engines/cox-babe-bee-049-overhaul/msg318814/#msg318814

That got him interested in Cox 049s. He bought them left and right, from PeeWees to BabeBees, Surestarts, a Black Widow And even a TeeDee.

(Over 50 years ago, we had struggled with diesel powered SkyBees and finally learned to fly after we got our first Cox Babe Bee, and built a mouse racer (anyone remembers those?)
I and my friend used to fly ten flights each on a single Singer Sewing Machine oil squeeze bottle of fuel.
After failed experiments with smaller batteries, we’d managed to get an Eveready 6G dry cell, about 6” tall, 2” in dia and maybe 500gms in weight.)

So I knew that a Babe Bee powered trainer is a good way to go.

By this time my young friend had acquired one sheet each of 5mm and 2mm balsa.
So I drew up a plan for a trainer and sent it to him.
He built it and became competent at flying it with a Babe Bee on 25’ thread lines.

Then he wanted to know how to do loops!
This was not possible with the trainer, as it was intentionally designed with low sensitivity for a beginner.

So I built another model with profile fuselage and symmetrical section built up wings.
Called it the ‘Musty’ for its fuselage like a Mustang.
He insisted that I send it to him, and not fly it myself first.
It got damaged in transit, but he was able to fix it.
And fly loops!

Next he wants to do inverted flight and outside loops.
He started building a Baby Ringmaster, but the ribs did not come out well.
So he asked me to build him a Nobler.

A NOBLER?
Wow!
A tiny one perhaps. And simpler too.

So that’s why I’m designing and building a ‘Simpler Nobler’

Attached are pics of the Musty.

(The earlier story is here:
http://www.rcindia.org/kites-trains-free-flight-and-all-others/control-line-revisit/msg318891/#msg318891)

‘Musty’ pics

How to start on trying to design and scratch build a 1/2A model that may be capable of basic aerobatics?

Here are some thumb rules:
1. You need a Tee Dee or a Black Widow. Very difficult with just a Babe Bee (For those not familiar with Cox engines, these are different 049 models, ie, 0.8cc)
2. You need nitro in the fuel, 20% if possible
3. All up weight should not exceed 6oz (170 gms)
4. Wing loading should not exceed 6oz/sqft, ie, wing area should be at least 1 sqft
5. Achieving 3 & 4 at the same time is not difficult if you have 6 Lb/cuft balsa. (This means a 1mm x 10cm x 100cm sheet weighs only 10 gms!)

The unavoidable weights are:
- engine and prop 60gms
- tank, undercarriage, bellcrank, pushrod, leadouts say 30 gms
- covering 10 gms

So you’re left with about 70 gms for the airframe!

Every single balsa sheet I have is 9-15 Lb/cuft, far heavier than desirable
Let’s see how close to the target weight we can get.
If it’s grossly overweight, I might have to get some imported balsa from Jodhpur Sharmas...

I had built an RC Model http://www.rcindia.org/gas-glow-nitro-planes/hornet-049/

I remember that. What a screamer. Amazingly fast.
And 4 and a half minutes on just 5ml!

We still fly it! Going strong

Sent from my moto g(9) power using Tapatalk

How to make sure it resembles a Nobler?
Retain the outline and proportions as far as possible.

How to make it simpler?
Make the flaps fixed, not moveable.
Sacrifice the leading edge taper and make it a constant chord wing. Simplifies the ribs.

Span 24” plus 1” each tip.
Chord excluding flaps 5.5”
Flaps taper from 1.5” at root to zero at tip.
Stab/elevator span 11”, chord 3.5” at root, 2.5” at tip
5” distance between trailing edge of flap and leading edge of stab.
2” between firewall and wing leading edge (assuming engine with integral tank mount)

Here’s the sketch.

Musty has green wings now

Let’s begin.

Make a rib template using any material stiffer than balsa. I used some fibreglass sheet. Be as accurate as you can. Note that I cut the rib shape only on one side. (Pic 1)

Cut 14 rib blanks 1” x 5.25” from 1.5mm or 1/16” balsa sheet.

Make a temporary jig (Pic 2)

Insert a rib blank into the jig (Pic 3)

Place rib template on top of the rib blank (Pic 4)

Cut the top shape of the rib.
Then invert the blank and cut the other side of the rib.
This ensures that the curve of the rib is identical on top and bottom.

Clamp the ribs together and cut the slot for the spar. 2mm wide x 1/2” deep.

While the ribs are clamped, sand them with a sanding block so that all ribs are identical.

Select 2 ribs and cut 1.5mm or 1/16” from the outline. The two ribs will form the wing centre section and will be covered with 1.5mm sheet.

Cut a 1.5” x 12” strip from 2mm sheet.
Cut it diagonally to get the two (fixed) flaps.

Cut wingtips from 1” x 5.5” of 2mm sheet.

Now the long parts. Note different lengths.

LE 1/4” sq x 25” hard balsa. I used some decades old brown strip I had, could be Simbal (often used in kits long ago)

Spar 1” x 26” medium hard balsa 2mm thick

TE 2 pieces of 3/4” x 24” of 1.5mm balsa.
1/4” of the bottom TE is chamfered so that the top TE strip can follow the top outline of the rib.

Weight of all the wing parts (excl centre section sheeting) 42gms
LE itself is 7gms!

Medallion 049 got entry in family of my engines.
I think Tee Dee will be jealous whenever they will sit together.

A profile fuselage would have been simpler.
But because of the potential weight penalty, decided to make a simple built up one.
Should be about half the weight...

Looking very good.  Please do share the weight of the completed ready to fly fuse when completed.

I see that you have also cut a slot for the flaps in the fuse. Usually kit drawings show only the wings in the fuse slot and the flaps are affixed but not in a slot.

Made some progress today.

Lower part of fuselage cut from 16”x2” of 2mm sheet (2 pieces)
Upper part from 9”x1” of 2mm sheet (2 pieces)
Front part of fuselage made solid by sandwiching two layers of 6mm balsa between the sides.
Uprights and top and bottom sheeting 2mm.
Weighs ~29gms.
Several gms (10 or more) may get added by the motor mount of ply/hardwood.

Stab/elevator from 11”x3” of 2mm balsa. Tip chord 2.25”
Fin from 2mm balsa, mounted askew In slot on top sheet to give right rudder.

Weight so far - wing parts 42gms, fuse 29gms, stab 7gms. Total 78gms.

@ Free Flight
Reason for flap slot - I had planned to cut away the fuselage bottom from the max thickness position till the TE. And attach the wings with rubber bands!

Coming right along. Cool.

Interesting concept to hold the wing with rubber bands. What are you plans that the wing does not slide with the pull in flight. I assume you are going with this concept as "a give" should and when the eventual strike to the ground?

My crash experiences has always  been that the profile fuse gives behind the wing TE and/or the rudder. Wing usually stayed intact in the mount.

From the photos I gather that this will be a 1/2A (Cox 049) model. Perhaps you already know this, but on the Cox redie engines, I always spin clockwise with a reverse prop. This way the outward pull is sufficient and can keep the right thrust and fin deflection to minimum or zero. On the brushless electrics (reverse any two motor wires), I always  follow this practice.

Just sharing, FYI.

Cheers!

Will save 1/4oz wingtip weight too.
But I don’t have a left handed prop...

Wing being assembled.
Egg crate construction.
Pinned the lower TE strip (the one with the chamfered edge) on the drawing board atop the plan.
Mounted the ribs into the slots in the spar, but did not glue.
Held the LE in place with rubber bands around the spar.
Aligned the ribs with the TE, making sure that the spar is exactly over its position in the plan.
Pinned the two end ribs and the two centre ribs in place.

Often when I buy CA, I forget to check if the nozzle is in the box. It often isn’t.
It wasn’t, this time too.
Impossible to glue small joints with the with the glue bottle tip that’s about 3mm dia.

I’d bought syringes for fuelling Babe Bees, so the needles must be lying hidden somewhere in their protective covers. Some searching led to one in a most unlikely spot - the compartment in my cupboard where I keep my passport, car registration etc!

Mounted the needle on the syringe and sucked a few drops of CA into it.
But not before poking myself in the finger!
Fortunately the needle had been inside sterile packing. So no tetanus shot.

All in all, my first attempt at super gluing with a syringe was quite successful.
Even though I failed to cover the plan with film, or rub it with soap/candle.
But tearing off bits of the plan while removing the wing wasn’t too high a price to pay.

84gms so far.

It was 84gms yesterday.

Add micro balloon epoxy mix fillets to firewall and fin.
Give the wing two coats of dope.
Give the fuselage and tailplane two coats of dope/cornflour mix.
Cover with tissue. Add two coats of dope.
Spray 2 white undercoats of PU spray.
Cover the wing with Monokote/Chinakote.

Already 108gms!

Yet to add wingtip weight (10gms), second half wing covering (10gms), bellcrank/horn/pushrod (5gms) and undercarriage (15gms).

Doubt if I’ll stay under 7.5oz.
Better order some 20% nitro fuel!

Within minutes, got an interesting reply on RCGROUPS from 049flyer:

KK

I think that your simple Nobler is a great effort but just a bit too large. If you look at a good number of 1/2A stunt planes you will find that have smaller wing spans and smaller fuselages.. Like the Baby Ringmaster or Baby Flite Streak.

You have built a nice .09 stunt plane in my opinion. I don’t think it’s over weight for the size of plane it is. I doubt that many on this board could have built a plane that size and come in under 6 oz.

Stick a Cox .09 on it and have fun! An Enya .09 or a Fox .15x would work too (similar weight and power as the Enya).

What do fellow RCI members think?

There are a lot of experts everywhere

The Hornet I built (RC) 38" span, flying weight approx. 450 gms

Plans and article here:  https://outerzone.co.uk/plan_details.asp?ID=5419

Cox 049 engine

Flies just fine!  I say go ahead and use that Cox 049, it will fly great

Depends what you expect from the model. Put and 09 engine and it should be capable of doing a lot of stunts. With a Cox 049 perhaps much less.

I started my RC career in the early eighties with this model below. 573 square inches at 26 ounces. The 049 did the job.

https://outerzone.co.uk/plan_details.asp?ID=11286

Airframe 132gms now.

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.