Author Topic: Hinge Line Configuration (Read 6342 times)

jfv · « **on:** March 19, 2018, 09:15:29 AM »

Based on some reading, I found that the hinge line configuration is something we should possibly consider when building our stunt planes. The three configurations that are most common are shown on the sketch. Which would be considered most appropriate, or does it really matter? I'm assuming they would be sealed.

Brett Buck · « **Reply #1 on:** March 19, 2018, 09:51:37 AM »

Quote from: jfv on March 19, 2018, 09:15:29 AM

Based on some reading, I found that the hinge line configuration is something we should possibly consider when building our stunt planes. The three configurations that are most common are shown on the sketch. Which would be considered most appropriate, or does it really matter? I'm assuming they would be sealed.

This matters more than most of the things we idly gas on about to kill time in the winter. The 3rd example is the correct answer.

Brett

jfv · « **Reply #2 on:** March 19, 2018, 10:46:23 AM »

Thanks Brett. That's what I was thinking. Never really considered it before though.

Igor Burger · « **Reply #3 on:** March 19, 2018, 11:10:31 AM »

From your 3, the 3rd is certainly the best, but you can do it even better if you:

1/ give stab TE corners like in 1st version, but angled little toward elevator
2/ if you do LE of elevator sharper, you will not do mistake if you copy LE of stab and do it on elevator

The problem here is air flow which must enter elevator surface from stab disturbed on the gap. That kink visible on 1st elevator will make separated buble ater that kink which can any time appear or disapear and thus can make tracking problems or hunting. Therefore LE of elevator must be smooooth. Your round elevator nr 3 is much better but can be even better and smoother.

My point 1/ will make place with well defined conditions for separationg after stab. It WILL separate, turbullate etc anyway, so it is better to define place where it happens for 100% all the time. And that little angling of flow toward elevator will make good condition for sticking back to elevator surface.

Tried, works :- ))

Brett Buck · « **Reply #4 on:** March 19, 2018, 12:28:26 PM »

Quote from: jfv on March 19, 2018, 10:46:23 AM

Thanks Brett. That's what I was thinking. Never really considered it before though.

Thank Paul Walker, I ripped it off from him.

It's very important, more important than the trivial things we obsess over like a few ounces here or there, or the wingtip shape.

Brett

Dave_Trible · « **Reply #5 on:** March 19, 2018, 05:26:35 PM »

Quote from: Igor Burger on March 19, 2018, 11:10:31 AM

From your 3, the 3rd is certainly the best, but you can do it even better if you:

1/ give stab TE corners like in 1st version, but angled little toward elevator
2/ if you do LE of elevator sharper, you will not do mistake if you copy LE of stab and do it on elevator

The problem here is air flow which must enter elevator surface from stab disturbed on the gap. That kink visible on 1st elevator will make separated buble ater that kink which can any time appear or disapear and thus can make tracking problems or hunting. Therefore LE of elevator must be smooooth. Your round elevator nr 3 is much better but can be even better and smoother.

My point 1/ will make place with well defined conditions for separationg after stab. It WILL separate, turbullate etc anyway, so it is better to define place where it happens for 100% all the time. And that little angling of flow toward elevator will make good condition for sticking back to elevator surface.

Tried, works :- ))

Igor wouldn’t you think , on your last point, that might be the best reason for those who might put zig zag turbulation tape on the stabs- to establish a consistent point of turbulation under all conditions rather than more turbulation?

Dave

jfv · « **Reply #6 on:** March 19, 2018, 06:13:24 PM »

Igor:

Is this what you are suggesting?

Istvan Travnik · « **Reply #7 on:** March 19, 2018, 06:21:04 PM »

Devil's attorney asks:
There is an airfoil with some part of it moving.
Why shall be its thickest point so aft? (as I see, at 45-50% of chord).
Why isn't it better to keep at 30-35% ? (Similarly e.g. to NACA 009)

M Spencer · « **Reply #8 on:** March 19, 2018, 11:32:30 PM »

Primeval Tecnology can usurp tecno marvels , at times . Double Upholsterers Thread . ( H.D. Cotton Thread , care to snap or cuts you ) .
Scissors are better , actually .

but tough blokes Can Snap It .

Reasons , STRUCTURALLY , well done , the two surfaces are One , integrally .
Thus Defected , the resistance to bow under load , is considerable.

Aerodynamically , the slightly raised ' V ' s are comparable to Vortex Generators , for flow attachmen / adheshion .

Geometrically , The ROLLING Hinge Motion ( Square Tailplane Rear Face ( maybe the edges radiused ) , Round Elevator L. E. )
gives a varying effective Horn ( control Arm ) Length .

Both , the rolling ( vertically ) hinge effectively lifts the control surface , compared to pins , progresively through the travel .

Thus if replaced by Conventional Nylon Hinges , More Throw is Required for same effective deflection ! .

Wrenching apart a tailplane with Nylon Hinges is Difficult , wit Sewn Hinges , nearer to Impossable ;
for a comparison of structural integredy .

Howard Rush · « **Reply #9 on:** March 20, 2018, 12:09:14 AM »

Looks like a closeup of my knee.

Igor Burger · « **Reply #10 on:** March 20, 2018, 02:37:35 AM »

Quote from: Dave_Trible on March 19, 2018, 05:26:35 PM

Igor wouldn’t you think , on your last point, that might be the best reason for those who might put zig zag turbulation tape on the stabs- to establish a consistent point of turbulation under all conditions rather than more turbulation?

Dave

Reason for turbulator and also for sharp LE is IMHO stability of transition point. I did an analyze of blunt flat stab on JavaFoil and it gives enough data to see that the transition point (the point where lamiar boundary layer converts to turbullent) can abruptly move from LE to hingeline and back. All happens at angles in range 0 to 1 deg. Such abrupt change in air flow will certainly change the lift of airfoil, and thus cause hunting. I wrote about it some years back, it will be somewhere here on SH or on SST, I am not sure.

Wire turbulator on LE or sharp LE safely keeps trasition point on LE. It perfectly matches observations of Dave F. from Stunt news. So now I use zig - zag turbulators on LE of the stab, does not matter if necessary or not.

This could be also answer for Istvan - stab never comes to positive AoA (in respect to lift created) and we know (see thread for optimal airfoil) that such airfoils benefit from high point moved back (FX71) The trick is to make high pressure (ascending thickness down the air stream) till it reaches transition point, so that will prevent creating of separation bubble close to LE and thus laminar boundarry layer pressed toward the surface. Hinge line then safely mix the air enough, so it does not matter anymore. High point moved forward is good thing fpr wing, to have nice round top of lift curve to prevent step down at critical AoA - regime where elevator never works.

Igor Burger · « **Reply #11 on:** March 20, 2018, 02:46:28 AM »

Quote from: jfv on March 19, 2018, 06:13:24 PM

Igor:

Is this what you are suggesting?

No, sorry, I see Idid not write it clearly. I mean top of surface of stab to be andled dow, so that flow will be "sent" down to the elevator. I mean maximally 5 or 10 degrees. The back side can be straight.

I do not know if it is well visible on picture.

Frank Imbriaco · « **Reply #12 on:** March 20, 2018, 04:16:13 AM »

Good discussion. And, the square-off of the elevator and flap t.e. is certainly preferred. That softens response. I cringe whenever I see knife-edge t.e. on any movable surface.
A common trend in R/C pattern is to thicken the rudder t.e. and square it off. Obviously not part of our equation with fixed rudder on our ships.

Howard:
That was comical, as usual. Was on the beach Sunday and saw at least a 1/2 dozen folks with zippered knees. I pray my bad one holds out.

jfv · « **Reply #13 on:** March 20, 2018, 12:31:07 PM »

Quote from: Igor Burger on March 20, 2018, 02:46:28 AM

No, sorry, I see Idid not write it clearly. I mean top of surface of stab to be andled dow, so that flow will be "sent" down to the elevator. I mean maximally 5 or 10 degrees. The back side can be straight.

I do not know if it is well visible on picture.

Got it. Thanks.

M Spencer · « **Reply #14 on:** March 20, 2018, 11:15:36 PM »

Anyone got any figure on atmosphereic pressure Ea Side of the hinge line at verying deflections ? say @ 10, 20 & 30 Deg.

or w ind tunnel pictures ?

Differentail effective air speeds ? Does the air ' pocket ' in the concave side at / about the hinge ?
the flow assuming more of a curve over the between the deflected surfaces .

Is leakage thru hinge more differentail air speeds Ea Side , than pressures - Creating a venturie effect .

M Spencer · « **Reply #15 on:** March 20, 2018, 11:21:20 PM »

Just foundum thisum . Looking for Flow / smoke thingo .

Which is This :

From :https://www.cati.com/blog/2011/08/model-aircraft-control-surface-spacing-and-solidworks-flow-simulation/

Dean Pappas . Even tho its R/C its a hingey bit on the back of a Sym. Bit . Tho its not attacking at the angle . $:-\$

======================================================================

Getting a bit off topic , a Land Yacht sail thingo . And A Hydrofoil of a ceterboard yacht . High Lift low Drag tripe .
The Ply Templates look more akin to a Wing experiment . or maybe just a experiment ( both wing & tailplane )

Ted Fancher · « **Reply #16 on:** March 23, 2018, 02:19:31 PM »

Quote from: Howard Rush on March 20, 2018, 12:09:14 AM

Looks like a closeup of my knee.

You, too, Howie? I thought it was mine.

Ted

M Spencer · « **Reply #17 on:** March 23, 2018, 06:19:20 PM »

Knee must be better than new then .

Author Topic: Hinge Line Configuration (Read 6342 times)

jfv

Hinge Line Configuration

Brett Buck

Re: Hinge Line Configuration

jfv

Re: Hinge Line Configuration

Igor Burger

Re: Hinge Line Configuration

Brett Buck

Re: Hinge Line Configuration

Dave_Trible

Re: Hinge Line Configuration

jfv

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Istvan Travnik

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M Spencer

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Howard Rush

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Igor Burger

Re: Hinge Line Configuration

Igor Burger

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Frank Imbriaco

Re: Hinge Line Configuration

jfv

Re: Hinge Line Configuration

M Spencer

Re: Hinge Line Configuration

M Spencer

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Ted Fancher

Re: Hinge Line Configuration

M Spencer

Re: Hinge Line Configuration