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Old Jun 01, 2013, 05:28 AM
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Norfolk, England
Joined Sep 2001
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There's a lot to be said for reading as relaxation. It's what I always do when I get into 'burn out' mode. I like the escapism of novels though and just finished one about the fall of Constantinople. It was okay, but the same author's book about Vlad Dracula had stronger characters.

Getting back on topic. I've explained my thinking about this design in my thread. To me, it just doesn't look like a good flyer. Still, we can but persevere with what we have.

Pete
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Old Jun 01, 2013, 06:37 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
3,023 Posts
Five years ago, I returned to university for three years and took a Master's in Ancient and Classical (European) History. It was a very enjoyable contrast to my undergraduate Mechanical Engineering and Computer Science of 30 years before. But, learning that "history" is a story about the past that purports to be true and realizing just how much pure speculation goes into much written "history" ruined me on reading popular history. I do enjoy alternate histories... and just dashed through David Drake's 7 volume series of novels that posits warring forces in the far future reaching back to change the past by influencing Belisarius and the eastern Roman Empire to ally with Persia and Axum to defeat a similarly influenced Malwa Empire in the Indian Subcontinent. Triremes and Cannon fire. Steam ships and trebuchets. It was well done and quite fun. Now, back to our movie...

In the three flights accomplished thus far, I proven to myself that it does fly. The sharp stall has been my downfall twice.

If adding more down thrust doesn't allow me to sidestep the stall bucket by force, I have it in mind to build another wing, adding ailerons and changing the airfoil to something with better lift at low speeds and low Reynolds Numbers; perhaps with a larger diameter LE and some under-camber.

David
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Old Jun 03, 2013, 05:59 PM
Ad eos qui nesciunt crepitus
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United States, TN, Memphis
Joined Dec 2012
1,304 Posts
Knight airfoils

David,

Yeah, Yeah, I know........I disappeared for a while...my other passion...bass fishing, and now my kids at The First Tee....teaching 3 days each week.

If you come up with an airfoil you want to try, I'll be happy to take the ordinates from whatever data file and convert it into an airfoil pattern at whatever chord you want....I wrote a little routine to do just that.......the neat part is that when I run it in AutoCAD, it will smooth the curves automatically. Here's a couple to ponder.....some are slower, some with U/C, some with a bit of wash.

How you doin' ?

And remember, history is written by the victorious.

C
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Last edited by Old_Pilot; Jun 03, 2013 at 06:17 PM. Reason: ADDED AIRFOILS
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Old Jun 05, 2013, 04:16 PM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
12,788 Posts
Snag with open framed tissue covered wings is that many parts of the 'section' are pretty close to being straight lines. Having idly contemplated an ultra large scale version of this puppy, and following this thread, I'd be looking at fudging the wing for a little more area - greater span and chord - plus a slightly deeper section with more ribs and maybe riblets too.

Rubber powered FF models of this size fly under different rules to the rest of aviation, I suspect. Good luck with the further testing.

D
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Old Jun 13, 2013, 11:05 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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I got everything repaired and went to the field last night for a quick test before dark.

And... although I had conducted bench tests... the set screws on the motor mount proved to be loose. And, I did not have my tool kit.

Given my pesky bad luck, perhaps I should have chosen a different pilot.

But I have video...

Abortive Test Flight of the "One Knight in Boston" 12 June 2013 (2 min 50 sec)
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Old Jun 13, 2013, 12:30 PM
Never stop being a kid.
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United States, CO, Manitou Springs
Joined Jan 2012
543 Posts
Too bad, but glad to see it caused only a delay and not more damage. Wish that soft, green stuff would grow better here.
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Old Jun 15, 2013, 12:08 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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She flew much better with the wash out and added down thrust. She would do full up elevator at 75% throttle and almost perform a 'harrier.'

Video is uploading.
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Old Jun 15, 2013, 12:15 PM
UMs & parkflyers... for now.
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United States, VA, Herndon
Joined Apr 2012
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Video

Knight Test Flights, 15 June 2013 (6 min 33 sec)
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Old Jun 15, 2013, 01:54 PM
Never stop being a kid.
BrundleFlyBy's Avatar
United States, CO, Manitou Springs
Joined Jan 2012
543 Posts
Yahoo! Congratulations, David. Seems to fly well at surprisingly slow speeds. Does she maintain a neutral attitude at higher throttle settings or do you have to add a lot down elevator to get more speed and keep her from pitching up?
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Old Jun 15, 2013, 05:28 PM
Sir Jasper
zl3vml's Avatar
Christchurch - New Zealand
Joined Jan 2003
789 Posts
Well done David.

I agree with you though - less control through would be better and some more downthrust will help too.

I like your wing hold down system and hidden latch :-)

Mark
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Old Jun 15, 2013, 07:46 PM
Registered User
Norfolk, England
Joined Sep 2001
7,796 Posts
David,
Nice one mate. She appears to fly very much like my smaller version. Stable hands off, but needing a gentle touch when turning to prevent that wing dropping.
Interesting that you've kept cutting back on throws. I hardly ever use rates and never use expo, prefering to keep my thumb at the base of the stick and ease the model into turns - as I fly all my slower models. Nudge in a hint of stick and keep a close eye on what happens. Since I fly mode 1, there's no risk of accidently nudging in elevator too. Good for slow and stable, but too far to move the thumb for faster flying models - around the stick for opposite turns.
Anyway, congratulations. Two down, umpteen to go.

Pete
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Old Jun 15, 2013, 11:45 PM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
12,788 Posts
Hi David
She looks well set on the way to being a good 'un.

Looking at the rudder responce, she's got that twitchyness that comes with adding controls to a FF model. They're designed to fly in a circle in a steady state thanks to a small trim tab with little offset and suddenly there's this big rudder being enthusiastically waggled around, plus the elevator. Found with most of my ultra-giant scale 'rubber models' that being real easy on rudder throw and enthusiasm of use works best.

Let's face it - these are best flown in similar weather to what the 'prototype' would prefer. As in, as close to flat calm as comes handy. Ease up on that rudder throw and your 'Knight' could soon be having its day (groan! Sorry...)

If anyone fancies fancies low wing RE or REM excitement, look up the 'Bee-Tween' plan by the late Randy Randolph. It was a free pull-out in 'Model Airplane News' around 1990 - sorry, my copy is going to be spending the next three or four months in storage with all our 'stuff' while we move to somewhere near the Disaster of Columbia... That model is a cute 36" span low winger based on a Cox 049, but has been electrocuted.

Love your battery hatch David - I never got along with using the wing as a hatch since my first electrics in the 'seven cell trap' days, but yours works real well.

Great little model. If I get lucky, might even get to see her - we're heading for a corporate apartment in less than two weeks now. Three months or so in Crystal City...

Good luck trimming her out

Dereck
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Old Jun 16, 2013, 02:30 AM
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United States, IN, Hammond
Joined Jan 2013
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Great job beginning to end Dave!
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Old Jun 16, 2013, 10:21 AM
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Blacksburg, VA 24060 USA
Joined Feb 2000
3,238 Posts
Dereck is right about how a free-flight (flee-fright?) model has a small rudder tab. Early RC models were adapted from FF designs, and many of them had small rudders (no RETA) actuated by escapements that delivered bang-bang actuation, from full throw one way to full throw the other. A small rudder was the order of the day to prevent over-control. For myself, I prefer expo and triple rates (DX8).

Watching the latest video, it seems to me that the bird flies a bit tail-low, suggesting nose-heaviness. This requires more decalage, or more up-elevator trim, to keep the nose up. Nose-up, the wing may be closer to stall. And when it does stall, it drops a wing. Either one?

Moving the CG aft and reducing decalage or up-elevator trim might help reduce stalling. Maybe more wing washout might help the wing dropping problem when it does stall.

Jim R.
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Old Jun 16, 2013, 10:35 AM
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Norfolk, England
Joined Sep 2001
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Jim,
Did you mean tail heavy? The tail is unlikely to sit low if it's nose heavy. If so, moving the balance point back will just make matters worse.

Pete
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