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Old Oct 26, 2005, 01:52 AM
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Melbourne, Australia
Joined Mar 2005
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Bob Aberle Piper Cub PA-11 scaled up?

Hi guys,

I'm fairly new to e-flight and have been flying a parkzone Decathlon for a while and am really keen to build a 'simple' yet pleasant all balsa consturction to take the 'next step'.

I've built a couple of scale Peter Rake 36" models which I love (DH-6 & Eastbourne) - but I'm not going to risk flying these until I've cut my flying teeth on a simpler model that I'm less attached to!

While snooping around the net I came across the free plans for a PA-11 Piper Cub at 30" (http://www.backyardflyer.com/click_t...pipercub_1.asp) and was attracted to the good looks and fairly basic construction.

I'm interested in scaling this up to about 36" - 40" and using either a geared 280 or 400 sp motor. I don't have any idea what the weight would work out at - but am interested to get the opinion of more experienced modelers to see what you think?

So, some questions...

1. Do you think this plan would fly OK when scaled to ~ 36" - 40"? And if so - what size should I go for?

2. Any suggestions on the motor/gear ratio/prop & battery I would be looking at?
(I'm looking at a 280 or 400sp motor & NiMH batteries).

3. Anything else I should keep in mind or change on the plan when scaling up? Appropriate Dihedral, etc?

If it looks like a goer then I'll do a thread and we'll find out!

Thanks!

Cameron.
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Old Oct 26, 2005, 02:24 AM
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United States, FL, Clearwater
Joined Aug 2004
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i've built this plane according to specs and it was a brick. never truly got off the ground. i've had pretty good success with all the other planes i've built except this one.

i tried absolutely everything and had to grossly overpower it just to get it airborne and it flew for all of 1-2 seconds before it flipped over and nosed in.
i even tried increasing the dihedral. no go.

i'm pretty good at following instructions but this one just wouldnt. you may have more luck scaling it up though. knowing me it was probably just something dumb i did or didnt do though.

at least it looked real pretty.

i gave it to my 1 year old to play with (now 18mos) within 48 hrs it was splinters.

*edit*
Here's a link to the thread with the completed pics in it.

http://www.rcgroups.com/forums/showthread.php?t=357950

looking back at those old pictures, the airfoil looks awfully thin. i wonder if i messed up.
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Old Oct 26, 2005, 03:29 AM
Naturally altered
Joined Feb 2005
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It looks real nice. I see no reason why it would not fly good in an enlarged version. I am tempted to build one myself, but with so many projects and so little time, that remains to be seen.

I would bet on a GWS 300 or 350 for a 40 inch version. At this size, a speed 400 and NimH batteries that could handle the 10 or more amps would make it too heavy. 48 inches would look about right for a speed 400 version. In either case I would select a rather low gearbox ratio (2.5:1 or 3:1) in order to keep the RPM`s up (and airspeed). Keep the build real light and use lightweight covering film.

My own version would have no-dihedral wing with ailerons, BL and 3s lipos. 2208-34 or Rimfire for a 40in version and 2212-26 for a 48 inches version (and good aerobatics ).

My .02
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Old Oct 26, 2005, 11:29 AM
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Martin Hunter's Avatar
Kamloops, BC, Canada
Joined Feb 2002
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I'd think that would fly great at about a 40" span with around 200 to 230 sq in of wing on a 280 motor.

Mcharles, your pics show a massive amount of washin on both wings. That would account for a good deal of unflyability. What did your AUW come out to? Overpowering isn't necessarily the answer for a plane that size - light weight is.

Martin
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Old Oct 26, 2005, 05:38 PM
Gravity is a harsh mistress.
Tim Wolff's Avatar
United States, MI, Temperance
Joined Sep 2002
6,608 Posts
Sounds like you are already a builder! Cool!

Have a look at the Citabria Pro. The kit is very complete and among the best I've seen. It should fall together once I get time for it on the building board.

http://www.joeld.net/citabria/
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Old Oct 26, 2005, 06:36 PM
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Melbourne, Australia
Joined Mar 2005
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Thanks - rear end weight?

Thanks guys for your comments so far...

I'm almost getting enough encouragement to try the model scaled up to 40"...

In previous builds and on lists I've heard much of ensuring the rear is as light as possible to aid balancing the model and keeping the overall weight down. As this model has full sheets for the body sides and tail surfaces, do you suggest that I should look at putting 'lightening holes' throughout the tail structure to reduce weight? (and maybe 'cut outs' on the fuselage sheets to save some more grams?)

I"ve heard mixed thoughts about this in the past... (Some say go for it - others that the saving is not worth the effort...)

Related to this, when scaling up from 30" to 40" should I still use the 1/16 balsa on the sheeted surfaces or go to 1/8 for more strength (and maybe use the holes as mentioned above?)

Again on the wing ribs - same 1/16 with a few more ribs or go to the 1/8?

Tim, kits are good - but shipping to Australia adds more $... I'd also like to scratch build from plans as this is what I really enjoy (and feels more creative!) - and a free plan makes the process all the more enticing - if it works!

Thanks guys - appreciate all your input so far.

Cameron
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Old Oct 26, 2005, 06:59 PM
slow but inefficient
Ron Williams's Avatar
Riverhead NY USA
Joined Dec 2000
3,097 Posts
I thought I posted this already but Aerocraft has an inexpensive kit for the Super Cub designed by Pat Tritle that flies great.

http://www.aerocraftrc.com

I did post this already - on the scale forum - cam777cam has double posted. Naughty, naughty. But welcome to the ezone anyway, camcam.
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Old Oct 26, 2005, 07:51 PM
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United States, FL, Clearwater
Joined Aug 2004
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Quote:
Originally Posted by Martin Hunter
Mcharles, your pics show a massive amount of washin on both wings.
Martin
Hmmm your probably right i didnt notice that. Back when i built that plane i knew nothing about washout or in.

with my recent experience with the SA Squirt my rudder throws were probably too high causing it to flip.

Maybe i'll scale it up and try it again. I really want a cub and love scratch building.
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Old Oct 26, 2005, 09:22 PM
Naturally altered
Joined Feb 2005
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cam777cam ...

When building from an enlarged plan, the outline of the plane is the one feature most interesting about it. It's only normal to change a few things here and there to accomodate the stress involved in the structure of a larger and heavier aircraft. The original was built as 5 ounces or so with a very light power set-up. A slightly larger one built in the very same spirit (very lightweight) would fly well at 40", as Martin suggested, with a 280 motor. However the one I have in mind is a little bit beefier for more aerobatic flying (hence ailerons and stronger power set-up). You`ll decide how you want yours built, but here in a nutshell are the modifs I envision.

Wing ribs with 1/16 balsa are just fine, but three more of them per wing panel. Wing joiner and spars should be beefed up a little. Wing is gonna be strong enough to support the flying, so that the struts can me made in 1/8 medium light balsa and used for scale look only. Solid sides are also more than fine with 1/16 balsa. Using light balsa, the weight of sides should be more than acceptable. Lightening holes are a possibility. For my own, i will probably end up with a 3/32 built up stick structure. I like the transparent covering on small planes and buit-up structure. On large ones too. I have a 78" wingspan electric Kadet Senior with built-up fuselage and it`s quite good looking. The tail group is gonna be built-up too, with 1/8 x 1/4 medium hard balsa. That`s it for now.

My .02 (your account now stands at .04 )
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Old Nov 28, 2005, 07:54 PM
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cam777cam

did you ever build this one scaled up?

i'm trying it again at 40" WS this time around. I plan on removing the dihedral and putting ailerons on it.

Actually 3 of these are being built. the one i'm doing and i have 2 younger brothers that are building one each. theirs will be with dihedral though.
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Old Jan 26, 2014, 06:00 PM
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Joined Dec 2012
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I build one also its a nice plane and it flies good I put up the
Wing span to 33" inches and all ribs are from ply wood 1/8.
And 1/16 sheetsOn the sides 1/18 balsa rudder and elevator and put some big wheels But better to fly with normal and the wing I put two servos for the Ailerons and made a turning tail wheel for good controllable
Landings and I recomend to put a little bit over power engine
Like a eflite park engine.
Ok so I made the ribs and made the bodie and a
Tricky part is the wing the struts and aileron ok so start with aileron
Modify the ribs and by the aileron location in the plans make the aileron out of thick balsa.
and to hold the aileron use nilon hinges and to fill up the empty space in the ribs you put wood in it like 4/32 and 1/16 ply behind the balsa to be easier to mount the hinges and for to mount the servos you cover one space with 1/16 ply and make a square hole for to enter the servo.
The strut on the wing I found a strut location on the wing with two x and it does
Not say whare to mount it on the fusaleage so I mount it rite on the landing gear
So attach the two endings on the wing what its located on the plan and the other one ending you put by the landing gear.

Mine flew I have 3 one nitro one electric and a rubber power but scaled the wing
To 20" span but it flies nice and toes planes with power

If you need more details yust ask.
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Old Jan 26, 2014, 06:09 PM
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Hello can any body be kind enough to tell me from what material to make the struts
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Old Jan 26, 2014, 06:10 PM
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Plastic or ply.
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Old Jan 26, 2014, 06:11 PM
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About carbon fiber.
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Old Jan 26, 2014, 06:17 PM
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It's easy to break but if you make it out of balsa
You should take 1/32 music wire and under it put
Yello plastic for good locks and to screw it on the ply
No the wing and by th landing gear.
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