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Old Mar 14, 2015, 02:13 PM
Rudders are overrated
The_LeadingEdge's Avatar
United States, VA
Joined Jan 2014
116 Posts
My scratch build has barely 2" of dihedral .. Wonder how thats going to work out. Thanks for the input.

For those wondering, I apologize for the lack of a maiden. Weather has just not been kind as of late. We've lost the snow, which was quickly replaced by wind and rain... I'll be watching the forecasts and whenever I get a chance I'll give her a toss and post the results.

Andrew
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Old Mar 16, 2015, 07:39 PM
Rudders are overrated
The_LeadingEdge's Avatar
United States, VA
Joined Jan 2014
116 Posts
Quote:
Originally Posted by Amp Abuser View Post
Should be a floater easy relaxing flying, I would just avoid windy days with it.
Floater my a** ...lol

Well I just arrived home from the maiden of my scratchbuild. All in all, not too bad. Although I no longer have a plane to show for it I ran a tank of fuel through it just to get things warm, then with the help of my brother I got it started and leaned it out about 1 full turn. Set it on the pavement with about 50 yards of asphalt to run. As soon as I let go I knew we were gonna have problems; the torque of that darned engine was incredible! I hadn't built in any down/right/ thrust angles, therefore the plane had some incredible left turn tendencies. It took full right-rudder just to keep it taxiing straight, then after nearly taking out my brothers ankles, I pulled her up hard and we were off.
Control in the air was about the same as on the ground; it took full right rudder just to keep her straight (more or less) but at this point she was no longer heading straight, instead she was was barreling down the field to the left towards a few un-expecting joggers ~100 yards away.. Well I figured that letting her take to the left and holding up-elevator would at least give me a tight circle pattern for the remainder of the flight. Instead the 'circle' turned into more of a downward spiral and she made a spectacular *crunch* as she hit the asphalt.
Best part about the crash, my brother and I stood there staring at the wreck for a good 30 seconds in silence until finally he goes "Hm." and that was all.

The wreckage was as expected. Front end, gone. Minimal tailplane damage. Engine and mount still very much intact with a few scuffs in the prop. Wings took a few dents and dings, but are still very usable. Landing gear, amazingly, is still intact and unharmed. All the electronics were fine and there was no fuel leaking out of the tank.
Not sure if I will rebuild this one, considering that the entire front end is literally gone, but I may get around to it. In the mean time, I have another fun project I'm working on with my other Babe Bee, and a slightly larger scratch build to house my Fox .15.
Not a bad learning experience. I sure did enjoy it while it lasted ... all 20 seconds of it :roll eyes: Thanks for following along

Andrew
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Old Mar 16, 2015, 10:22 PM
Now I have to land that thing?
PGregory's Avatar
United States, NY, Poughkeepsie
Joined Apr 2014
437 Posts
Sorry to see its demise, and glad you certainly are taking it ok.
Would you have set dual rates/expos differently, looking back?
The fin was in clear air, your design didn't obscure it behind any thick fuse cross section, or anything. Should have had good grab.
Wonder what diagnostics other here might have about its outcome.
Hm is right.
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Old Mar 17, 2015, 10:27 AM
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Jburry's Avatar
Canada, NB, Mispec
Joined Feb 2015
22 Posts
Some of my 1/2a planes don't have any right or down thrust either (Northern Flicker has 0,0), but it doesn't make them uncontrollable at all. I suspect the culprit is something else. I'd look at the possibility of wing twist being the culprit.

If you have a flat bottomed wing (you seem to), tape a few foot long lengths of dowel on the underside at the root, half span and tip. Compare left to right. This will show any twist. Each wingtip twisting down a couple degrees (washout) is desirable, but most important - left and right must be the same.

With wooden wings and heat shrink cover, minor twists can be corrected by twisting the wing just past "right" and heat-gunning it. The cover will hold it straight. Not that that helps you with that structure!

Heartening that your engine survived!

J
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Old Mar 17, 2015, 01:11 PM
Now I have to land that thing?
PGregory's Avatar
United States, NY, Poughkeepsie
Joined Apr 2014
437 Posts
Isn't washout having the tips twisted up, not down? Which means the tips have a lower angle of attack, preserving lift?
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Old Mar 17, 2015, 01:16 PM
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Jburry's Avatar
Canada, NB, Mispec
Joined Feb 2015
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Front of wingtips down, trailing edge at tips up, which does reduce the AOA at the tips, preserving control.

J
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Old Mar 17, 2015, 05:55 PM
Rudders are overrated
The_LeadingEdge's Avatar
United States, VA
Joined Jan 2014
116 Posts
Quote:
Originally Posted by PGregory View Post
Sorry to see its demise, and glad you certainly are taking it ok.
Would you have set dual rates/expos differently, looking back?
The fin was in clear air, your design didn't obscure it behind any thick fuse cross section, or anything. Should have had good grab.
Wonder what diagnostics other here might have about its outcome.
Hm is right.
I wasn't too concerned about its fate. I built it kinda ugly so that I wouldn't need to worry about ruining a beautiful flying machine.
And I had 60% D/R on both elevator and rudder with about 25% expo. I suppose it could have benefited from a touch more throw on both surfaces, maybe around 75% or so. Wouldn't an engine that small generate a decent amount of torque, or no?
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Old Mar 17, 2015, 06:08 PM
Rudders are overrated
The_LeadingEdge's Avatar
United States, VA
Joined Jan 2014
116 Posts
Quote:
Originally Posted by Jburry View Post
Heartening that your engine survived!
Yes, that red rubber spinner took most of the impact thank god

Quote:
Some of my 1/2a planes don't have any right or down thrust either (Northern Flicker has 0,0), but it doesn't make them uncontrollable at all. I suspect the culprit is something else. I'd look at the possibility of wing twist being the culprit.

If you have a flat bottomed wing (you seem to), tape a few foot long lengths of dowel on the underside at the root, half span and tip. Compare left to right. This will show any twist. Each wingtip twisting down a couple degrees (washout) is desirable, but most important - left and right must be the same.

With wooden wings and heat shrink cover, minor twists can be corrected by twisting the wing just past "right" and heat-gunning it. The cover will hold it straight. Not that that helps you with that structure!
Well I'm not sure that the wing was twisted or warped .. That foam board will really hold its shape after is been folded and hot glued with a thick spar. Wash out, unfortunately, was not incorporated. I think that coupled with much more dihedral could have resulted in a much more stable flight.
And yea, I'm not a fan of iron-on coverings like monokote and such. I bought a roll of covering from hobbyking (their generic brand) which has been nicknamed "chinakote" and so far have had decent success with it. But personally I think shrunk tissue is much simpler, even if it is a little more time consuming. I've had much better results on my smaller electric kit builds with that. The warping trick is something I encountered accidentally on my LaStick build, very handy although I always get nervous aiming a heat gun at thin plastic ..


Andrew
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Old Mar 17, 2015, 07:01 PM
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Joined Dec 2007
1,521 Posts
One wing could have weighed more causing it to list.
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Old Mar 17, 2015, 08:06 PM
Now I have to land that thing?
PGregory's Avatar
United States, NY, Poughkeepsie
Joined Apr 2014
437 Posts
I think we found the real culprit.
http://tinyurl.com/mxpfm2x
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Old Mar 23, 2015, 02:36 AM
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Amp Abuser's Avatar
Joined Dec 2007
1,521 Posts
Total engine run time from start up to empty tank was 6.03 mins on 1 oz 25% nitro.


With my google chrome this page starts it at 360 dpi and allows a reset up 720 / 60 fps HD

You may have to use the link to watch full screen 1080 / 60 fps HD
3rd Flight - 1/2A Skorch TD .049 RC (9 min 58 sec)


Stock TD .049 with Cox RC carb without the muffler

APC 4.75 x 4
In the hand prior to launch 19,380 rpm / 73.48 mph theoretical
In the air the engine ran steady I was getting 21.4 to 23.3k depending on wind direction
In the air 81.06 to 88.3 mph theoretical.
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Last edited by Amp Abuser; Mar 28, 2015 at 04:33 AM.
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