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Old Aug 14, 2010, 05:03 PM
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philipa_240sx's Avatar
Ontario, Canada
Joined Apr 2010
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Quote:
Originally Posted by jkarnacki View Post
Might have to try the undercamber wing as I've never made one before and I've recently acquired a heat gun. Woohoo!

- Jeff
I think you need the KFM5 version of the UC wing to get enough strength.

Honestly, I like the KFM 2/3 wings. They fly a bit faster than the UC versions, but are more stable in windy conditions.
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Old Aug 14, 2010, 05:46 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,690 Posts
"..Now to decide between an undercamber wing or KFm2..."

On the 42" wings I think the KFm2 is the better choice. The spar supports the step but more importantly it gives you the strength you need for a wing that wide. A 42" UC wing gets a little fragile...

Jack
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Old Aug 14, 2010, 05:58 PM
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Croatia, Europe
Joined May 2010
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Kfm 3 wings on very windy and cloudy condition today deep in the sky (taken with 480 mm telephoto lens).
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Old Aug 14, 2010, 06:17 PM
Registered User
USA, CA, San Carlos
Joined Nov 2007
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I hadn't thought about that...a single sheet of FFF on a 42" wing would be awfuly flimsy, huh!? With CF tubes it would be stiff, but not torsionally. May go with a flat Kfm2.

- Jeff
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Old Aug 14, 2010, 07:10 PM
I hate gravity!!
schrockie's Avatar
Tampa, Florida
Joined Jan 2010
135 Posts
4d

Sorry to go off topic, but can anyone direct me to a thread or forum on how these 4D planes work. Is it the VPP (variable pitch propellar) or are they reversing the motor.

4D rc indoor electric plane (2 min 44 sec)


Troy
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Old Aug 14, 2010, 07:24 PM
AKA Don
bz1mcr's Avatar
United States, MI, Houghton Lake
Joined Dec 2002
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Reversible prop pitch. No way could the prop rotation be reversed that fast, and the torque reaction if you tried would be absolutely brutal.
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Old Aug 14, 2010, 07:50 PM
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philipa_240sx's Avatar
Ontario, Canada
Joined Apr 2010
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Quote:
Originally Posted by jkarnacki View Post
May go with a flat Kfm2.

- Jeff
I actually find KFM wings far easier to build than UC. The spar along with the triangulation formed by the KFM step adds lots of stiffness.

Just got back from flying tonight... both BB33 KFM3 and my Blu-Citabria. Good times!
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Old Aug 14, 2010, 08:19 PM
Registered User
Cherry Hill, NJ
Joined Sep 2009
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Quote:
Originally Posted by jackerbes View Post
"..Now to decide between an undercamber wing or KFm2..."

On the 42" wings I think the KFm2 is the better choice. The spar supports the step but more importantly it gives you the strength you need for a wing that wide. A 42" UC wing gets a little fragile...

Jack
I have about 3 hours of flight time on my built-up KFm3 wing (http://www.rcgroups.com/forums/showp...ostcount=14334).

It works well with no spar (other than the built up foam) and no dihedral brace. I've done numerous regular loops and a few steep dives into loops with no problems yet. The wing has also survived some hard landings -- one of which beat up the wing saddle and broke one of the rubber bands.

I haven't crashed in quite a while, so now I think I'm ready to build a similar wing with ailerons. I'll report how that version performs when I get it built and flight tested.

Cheers!

Kevin
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Old Aug 14, 2010, 08:46 PM
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USA, CA, San Carlos
Joined Nov 2007
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I'm going to stick with a KFm2 just because I've personally used it on many models and it has worked well. An "old faithful", if you will.

- Jeff
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Old Aug 14, 2010, 09:17 PM
I hate gravity!!
schrockie's Avatar
Tampa, Florida
Joined Jan 2010
135 Posts
4d

Quote:
Originally Posted by bz1mcr View Post
Reversible prop pitch. No way could the prop rotation be reversed that fast, and the torque reaction if you tried would be absolutely brutal.
I'm just asking!! I've seen it a couple of times before in other vids, and want to know about the tech, how does it work? We ask questions to learn.

Troy
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Old Aug 15, 2010, 08:06 AM
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Ontario, Canada
Joined Apr 2010
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Quote:
Originally Posted by schrockie View Post
how does it work?
Electrifly V-Pitch Propeller System:

http://www.electrifly.com/miscproducts/v-pitch.html
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Old Aug 16, 2010, 04:01 PM
Registered User
USA, CA, San Carlos
Joined Nov 2007
1,332 Posts
EEEKKK!!!!

Currently my wing spar (not yet glued in) is set at almost 4 inches per side on a 42" KFm2 wing. I used sketchup to find out what angle I had to glue them, ended up at 5.5 degrees. I just realized why my dihedral is so much...I measured 5.5 degrees TWICE while cutting! Should I try 4 inches per side or should I just cut a new spar joiner out?

- Jeff
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Old Aug 16, 2010, 06:22 PM
Not always grumpy!!
insomaniac45's Avatar
UK, Eastleigh, Eastleigh
Joined Jul 2010
522 Posts
it would be better to cut a new joiner. 4" might prove extreamly slow to respond to turning. 2" is very gentle as it is.
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Old Aug 17, 2010, 12:18 AM
Addicted to building...
Freddie B's Avatar
Omaha Nebraska
Joined Feb 2006
5,992 Posts
Blue Baby 33" Combat!

My 2 cents worth.

I wanted to make a simple front yard/street flyer. Found the BB thread, and thought might as well try this build. Looks simple and what a following it has.

I have also wanted to test some options on the GWS IPS systems for some time. Great platform, or test bed for that.

I live in an area with a lot of wind, so the undercamber wing option works for the times when the wind isn't too heavy, or when it calms for a few minutes and I don't want to go to a park or the field.

But then, it occured to me. What about a couple of these, and then I could have Slow Combat with a flying buddy right out side the house. That's waht it will be, Blue Baby Combat planes.

BB Combat, yes, slow, 3 channel fun. It out to be a blast, and oddly enough, funny to watch with this type of plane.

Design hints at Pico Stick, Slow Stick, fly on the wing, slow deliberate need to think a little ahead of yourself in close quarters like my front yard!

Besides I want to do some KF Airfoil testing, and this would be a good foundation to go forward with that and see the differances we can come up with. Quick and easy test bed.

So anyway a little sharing of my version of the build, nothing fancy, trying to give Tony's design the credit as it was envisioned.

Fred
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Old Aug 17, 2010, 12:27 AM
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Omaha Nebraska
Joined Feb 2006
5,992 Posts
The first item was assembly of the Mono-block, 2 sides, rear former, and flooring. I had glued the motor stick in the mono-block befor gluing the sides on. A channel was cut so the ESC's could be installed, but removable too.

Picture below:

Left fuselage has motor is a GWS 'E' Gear Box, with the EDF motor (low Volt, high KV) 12 mm. This was a motor recomendation from the late Dave Robelen, for his Patter Babe design. Flew well, and yes, it's used! Using a 5 amp ESC in both planes.

Right fuselage has the good old Standard GWS 'A' Gear Box, stock. 12mm high volt, low KV motor. Oh, this was from my old Pico Moth, or a Pico Stick, so it's used too!

Fred
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