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Old Nov 05, 2006, 06:49 PM
Crash Master
Gene Bond's Avatar
Indianapolis, IN
Joined Sep 2001
16,632 Posts
I can say this:

I had a blast with the DDx1.5 this weekend while camping. Finally got sturdy enough landing gear to ROG from about anywhere. The motor power is just sufficient, not quite good enough at 25°, until the pack warms up... but pre-heat it in the armpit for a few minutes, and it's good to go

Flies great 3D the way I set it up. Sure, I still have it a tad nose heavy, but not so much that it's a pain, and with the current speed, it -just- begins getting pitchy ar full throttle... So I shouldn't touch anything. Hugh alpha is very controllable, to bring it in and drop at your feet.

Really flies like a well behaved Bipe. Makes me wonder I may push this thought some, with some more experimentation Meanwhile, it's a winner! Need to get over to Jer's and do some video, this week.
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Old Nov 06, 2006, 06:55 AM
gpw
“There’s no place like Foam”
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Out of all the bipes , this one decides to be well -behaved..... How Cool !!! and unexpected.... We await your videos..... Yeah , I finally got DSL and can watch the movies now ... Yippee !!!!
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Old Nov 06, 2006, 04:40 PM
Launchpad McQuack
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Netherlands, Moordrecht
Joined Sep 2004
1,130 Posts
I'm no aerodynamic expert, but to me it seems it only really needs the lower wing to fly. As long as the lower wing doesn't stall, the elevons keep responding, and the model stays in the air.

I guess the upper wing does stall at a certain high-alpha angle, but it keeps pushing the airflow over the top of the lower wing, preventing a stall.

Since the wingtips of both wings are far apart, there's not so much interference drag as with regular bipes. Therefore it behaves more like a quick racer... (mine did about 75 km/h (47mph).

I've flown her last saturday at our club. First flight was very very pitch sensitive. Brought her in for three chunks of lead in the nose. also connected the pushrods at a lower point on the servo horn. I had throws of about 10mm total, but used only about 10° of servo horn travel. It still could be better.

Lost prop+adapter on launch of the second flight. No speed, no control, stall, bounced on the nose. Firewall cracked (again...) and lipo hatch cracked (again). Luckily no further damage.

Both items will be strengthened by thicker ply this time.

Also need to roughen up the motor shaft, to prevent the propadapter from coming loose.

Prop-er
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Old Nov 06, 2006, 06:53 PM
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Joined Sep 2006
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My 150% Build

Glad to hear everyone is having success flying the new 150%!! As for me, I have begun my build. I may glue in some light ply to the nose (I can access thru the bottom hatch). I built mine a little different. I did not build a battery compartment, but rather a large compartment under the canopy. I still have a small compartment under the front bottom as well, which is secured with a hatch latch. I like the idea of being able to move battery around, etc. to achieve correct balance as opposed to possibly having to add weight. I installed a landing gear which I think will work good, made from carbon rod and music wire threaded/CA's on to the carbon. It appears to be quite sturdy. From my experiences with the 20" version, it comes in with a pretty gentle flare, so it shouldn't need much. I am not planning on 3D'ing this plane (I can't anyway!) but rather for attempting to take up my camera to take some aerial footage. Here are my pictures. Anyone see anything that would keep her from flying? Thanks!

Mark
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Old Nov 06, 2006, 06:58 PM
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Oh, I also used two carbon rods instead of one in each wing for extra bracing. I wanted this to be a "payload plane" but not am wondering since there is no airfoil in the wing how much lift it will have. I would think with two wings it should have plenty of lift, although the top probably doesn't do a whole lot... My payload hopefully will be a small digital camera to record pics and video...

Mark
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Old Nov 06, 2006, 07:11 PM
Launchpad McQuack
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Netherlands, Moordrecht
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You could be surprised by how much lift a flat airfoil could produce. (mind you, a flat plate still IS an airfoil...)

A small light digicam should be no problem. (Make sure you don't tape your new Canon EOS400 to it....)

I thought my 20" duplex was heavy, but it flies with ease.
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Old Nov 06, 2006, 07:53 PM
Crash Master
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Indianapolis, IN
Joined Sep 2001
16,632 Posts
Funny, when I saw the motor/prop recommendations on the DD4 (150%) plan, I was amazed at the difference of intention for the flight envelope I'm sure with the right (nose-heavy) cg, the big'un would fly just as well as the little'un, except... The flat-plate syndrome gets worse, the bigger the chord.

My guess is the big'un would need somewhat more forward cg % than the little'un, due to the lack of wing thickness. I do believe the numbers are true, based on some high and low aspect ratio winged planes I've flown. I see it more on the big'un at less than 1/2 the speed of the little'un, even though the wing is only 50% bigger. But, the little'un is an average chord of ~6", and the big'un ~9", so 3% and 2% thickness. Not being sure what the optimum thickness is... I'd guess about 6%.

By cutting a top plate and bottom plate for each wing, you could thicken it up, and possibly eliminate the other bracing? (spar)... I'd set the LE of the plate about 1" behind the LE of the wing, and end it about 2-3" in front of the TE. I'd be willing to bet it'd tame the pitchiness at higher speed way down... Cutting the LE of the plate on an angle would minimize the drag.

Just some food for thought. I've seen it work on other models!
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Old Nov 06, 2006, 08:58 PM
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Prop-er, were you flying the original, or the 150% over the weekend? 47 mph is pretty impressive, especially if it's the bigg'un!! My friend at the field finally got his together and couldn't fly it. His CG was too far back and his throws were WAY too much. I adjusted his rates for him and he tried again, this time he was amazed how much better and how easy it was to fly. 5 members are now building the plane, looks like it's going to be a pretty popular bird!!! How much throw is recommended for the 150%? I thought about making the control surfaces a little bigger, but went with the original plan. I don't plan on flying the way Gene does (at least not yet!!) or I'd bust everything up!!! The new Realflight upgrade has a neat 3d trainer function on it, where you can control just elevator, just rudder, just ailerons, etc. etc. Hopefully that will help me!! I finished taping my wings with the extra strong packing tape, top and bottom of them. Boy, it made a huge difference in the stiffness of the wing. My new Delta should be ready to fly in a day or so... already getting nervous and excited!

Mark
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Old Nov 06, 2006, 10:22 PM
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In my Blu heaven! near Lincoln NE
Joined Mar 2003
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Seems like the natural order of progression is for someone to do an FMS model of it!

Robert
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Old Nov 07, 2006, 01:47 AM
Launchpad McQuack
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Netherlands, Moordrecht
Joined Sep 2004
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Quote:
Originally Posted by thetriguy
Prop-er, were you flying the original, or the 150% over the weekend? ... looks like it's going to be a pretty popular bird!!! How much throw is recommended for the 150%? Mark
Mark,

I was flying the smaller 20" version. It has a pretty speedy motor.

The recommended throws on the bigger 30" version depends on the speed of the model. If you plan to slowfly it, get all the throws you can get. You can always put a load of expo and dualrate on it to settle it for the first flights.
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Old Nov 09, 2006, 10:45 PM
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Got her all finished up!!! Will maiden within a day or two!!! I'll try and post some pre flight pics tomorrow!

Mark
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Old Nov 10, 2006, 05:34 AM
gpw
“There’s no place like Foam”
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What about an EPP version , that would thicken the wing ....or howz' about a KF treatment on the wings ???? specks for thought ???
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Old Nov 10, 2006, 08:13 PM
rab
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Arlington, Virginia
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What is a KF treatement?

Allen
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Old Nov 10, 2006, 09:41 PM
Crash Master
Gene Bond's Avatar
Indianapolis, IN
Joined Sep 2001
16,632 Posts
Finally got together w/ Jer today, after a little bit of Chinese take-out, we played in the wind a little:

http://s63.photobucket.com/albums/h1...urrent=DD4.flv
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Old Nov 10, 2006, 09:48 PM
Use whatcha got!
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Metairie, LA
Joined Sep 2000
2,982 Posts
allen - look for the Kline-Fogelman thread... More or less, take a flat plate wing and double it on the bottom just for the front portion of the wing.

-mike s.
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