Author Topic: Another odd question - Forward sept wing trailing edge and flap hinge line (Read 58095 times)

Bill Schluckbier · « **on:** April 21, 2024, 12:35:42 PM »

Hello,

I have another odd question regarding flaps. I have been reading Bob Hunt's Genesis book (highly recommended) and in it he mentioned that Bill Werwage's Juno with had the wing trailing edges swept forward significantly and that it seemed to handle the wind well. In the build article for the Juno it was mentioned that sweeping the trailing edge forward allowed to keep the wing's center of pressure (CP) roughly in the same location for the wing as a whole as the flaps moved up and down. Seemed like an interesting idea and explanation. I also noticed that Bill's follow on designs used a straight wing trailing edge so maybe there is my answer....

I understand that a straight trailing edge makes building the models simpler without the need for lucky boxes or separate horns for the flaps. Would sweeping the flap hinge line forward provide an aerodynamic benefit? In the real world, most airplanes with tapered wings sweep both the leading and trailing edges. Any insight?

Thank you,

Bill

Dave_Trible · « **Reply #1 on:** April 21, 2024, 02:45:54 PM »

I don't know of anyone really testing this in a meaningful way for stunt airplanes. I have not used it as a design feature on any of my own designs but I have a couple classic airplanes that fly extremely well and have a small amount of forward sweep in the flap hinge line. I've read where some thought it created trim issues. Again I've not seen that. These I have are only about 3/4" forward sweep at the tips and don't require lucky boxes or separate horns. There is enough 'give' in everything that they work fine in the limited range they have to travel-maybe 35-40 degrees each way. I would think the 'tiny' benefit they might have is that the airflow boundary layer is ever rolling outwards towards the tips and facing the flaps more into that airflow could in theory add some lift though it would seem imperceptible . I'd think the reason most have done it is for cosmetic reasons, being able to taper the wing planform a little more that you can do with a straight trailing edge.

Dave

doug coursey · « **Reply #2 on:** April 22, 2024, 11:22:23 AM »

https://youtu.be/xjjqtSO8Tds?si=kUW1b4knLzCaFkAh

JUST WATCHED THIS WINDY VIDEO ON HIS LAST SPITFIRE WHICH HAD FOWARD SWEPT TRAILING EDGE AND SAID IT WAS THE EASIEST TO FLY OF HIS SPITFIRES

Bill Schluckbier · « **Reply #3 on:** April 22, 2024, 05:08:52 PM »

Thank you Dave and Doug for your replies; I will definitely watch the video. I have seen many of Windy's videos but somehow I missed this one.

Thank you,

Bill

Brett Buck · « **Reply #4 on:** April 22, 2024, 06:13:00 PM »

I think the swept-forward hinge line is probably a mistake, if nothing else, I think it makes it much more prone to yaw instability with the controls deflected.

Brett

M Spencer · « **Reply #5 on:** April 22, 2024, 08:03:08 PM »

Published The ories ! . Hunt / Wewage - > Effectivly LONGER MOMENT ARM . if you average the hinge , half way out , its further forward .

P. Walker . - . " Break my arm if you ever see me try another swept forward hinge ! " yaw / Trim instabilty ' errors ' making it a P A I N .

My ' observations , having half the planes with it , most severe sweep . Like THIS , ( Which is a M B 5 minus two . First 5 had that empenage , so a 3 could have 5 tail feathers , if you wanted to make life easier .)

o.k. Had a wreck 65 ounce STANDARD F2B ' 46 / 60 ' ( magnum based ) dunger out in hard bumpy air on the weekeend .
Had me thinking Id have to do a Standard ' 46 / 60 ' DECENT Genisis Spectrum Hallmark STANDARD YANKEE STUNT SHIP . as the orrible free T Tiger 46 ona 12 x 6 Tornado without touching the needle ' Did the Trick '
if not perfectly , PERHAPS it'll be acceptabilitil . as theres another two came withiit need bearings , it'll be three free . As We Said ' Something your not to worried about PLANTING ' ( in a GALE - . so no undred hourfinish or suchlike )
Swept Hinge - Stability - YAW . and THINGS .

published ' Hunt werwage ' = " Self Servo Effect " as in lighter control loads with it . IN THE WIND .

Bob ' quote ' Genisis 3 favourite ' with the is it ? 3/4 Flap Hinge Sweep .
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THIS with a Rabe Mustang FIVE Airfoil . Fully sheeted . SEE THE HINGE LINE . Mate .

For Flying in GALES - Rough air - Turbulance . a projectile . , 4.5 to 4.8 if your lucky , lap time . Std. Setting it usually self ' unloaded ' to suit on Atd. setting . THOUGH , when its billowing like billyoooooo
o , Down Proping keeps it moving . or accelerating ' out of a hole ' . With Tourque ( reactive force ) being the PRIME ISSUE . aaarrggghhhhh . Duck . Wheres my helmet . So there are limits .

HOWEVER : That Scale planform , once at 2:3 Flap to elevator , flew itself through the pattern smoothly , consistantly , and self generated consistant ' bottoms' Tho the V 8 from inverted , downward -
required ' comitment ' . After seeing it do it o.k. a few times , one accepted it was possaable . If inexplicable .

WITH THE 1/8 " FLAP HORN WIRE & C/F PUSHROD . Stiff 1/2 flaps and elevator . AND the prime flying feedback was the wee tail followed . the WING lifting the ship , in the rounds . In the squares ,
It was ' On the Controls ' ( as in the moving surfaces seemed the primary element - in force . other than the POWER . Equal and in concert . Apparently . )

That , A few spitfires , a Mustang , and others , WITH DIHEADRAL = The YAW is the complication . MB3 was fine - other than into the clover ( 45 up level ) and Top - 2nd Crner in the Hourglass .
this is where being able to leap 30 foot per bound saved the day .
AS IT NEVER HIT THE GROUND , the obsevation was a Rabe rudder may've made the jackrabbit act unnessesary .

Wot appens with diheadral & swept hinges ; The Yaw ( resultant of POWER reaction . ' prop grab ' - plane try to rotate opposite prop . As the PRIOP's ' gripped ' and the plane ' HASNT GOT A HOLD / Grip . ->
it's in a AIR HOLE OR UNBALANCED . The reaction to the primary force ( power - at that point , engine ON . )

The Flat Wing rather swept Folkerts , concived around 76 , for a 11 x 4 ! ! , If it KEPT MOVING was pretty good regarding yaw , roll , tension , and things like that .
First Flight on 9 mm intake 7 C'case pressure - Hor. Eights high , upwind , were FINE .

So presumeably electrification would lower the fuel consumtion to acceptabe . for that trim .

Presumeably , deflected swept flaps ' gather ' the atmosphere inwardly , in extremis , the fuselage acts as a fence , so working hard at high pressure , the flow theres good.
In V light wind and over 15 , the Folk was ' neutral ' fore & aft . around 8 to 12 it was soggeyer , wanting a touch more flap dialed in .

So , a SUMMARY . Adjustable Ratio . fore & aft . Provision for interconnected rudder , for if required . 1/8 wire flap horn wire for .46 / 60 . Im thinking the 5/32 is a bit stiff for bumpy air , when its blowing .
Several Notorious champions consider a little cushioning in roll from air load deflection is neccesary . the lenght of arm along the hinge , as a torsion bar , absorbs some ' bump ' reducing roll in uneven air turbulance .

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M Spencer · « **Reply #6 on:** April 22, 2024, 08:58:23 PM »

" Knocking you down would take a wind of at least 70 mph. The terminal velocity, which is the wind speed (falling speed) where the force of the wind equals the force of gravity, for a person is about 120 mph — that would likely knock you down. "

Figured a 1.2 lap time with G 15 on 50's is 187 / 300 kph odd . From the shelter of a Big hedge , a calm day oon a cyclone ( Hurricane ) the air from the Tasman concentrating falling across Auckland Harbour.
Raising on the raise and dropping to funnel through out downwind , the pushing down on the ground air from the raise over the Macracapra Hedge further enhancing its efficency , Sothat on occassion , downwind
the pip was sqyuezzed from the 180 downwind to say 240 / 250 , where it was inobservable . QUICK , befor the noise stopped twice as it hit ' into wind ' concurrent with a judder or two , before into the lee of the
hedge .

So , theres wind and theres wind . Three Goes totalling the field got it back after trying loops in lulls ! ? on the next flight , without breaking the lines . The new .015 solids woulda snapped like spagetti , if you ' caught '
it firm without cushioning the snatch .The brother refused to launch it for a third go . And I was just getting the hang of it ! .

Now this deflector ! ( NOTE THE DEFLECTION ) was a Renouned Wind Flyer . So we presume he knew a thing or two about it . He mayve even have thought aboutit a bit . and come to a few concusions .
LIKE THIS .

He perhaps mayve decided , was the way to doit .

My sealevel speriance gotme looking athis . Thought the inge might even keepit stright , inna urricane but wotid I know . I was only 16 . Nontheless . It was Contrived for a 11 x 4 prop & 40 knot wind . wotyer got often . for a HP or torp 40 rear induction . or a Super tigre maybe . R V .

THIS didnt like a muffler inboard ( it'd kick - drop nose to zero tension , on a slow wingover , 2/3rd thu. ( or 60 up, dowhill ) a step & kick appropriate line , and it'd ' caught ' the air again ! ! .

(( I wondered ; and figured . Maybe it was the equal Taper wing . Smaller Chord inboard tip . The Later bl

@dy gret big one with the ribs the same, and tips. Dont do that . So USE EQUAL TIPS . )
muffler outboard itdidnt doit . or muffler free . With a 9 mm intake on a 21/40 ST & C'case pressure , unmuffled . it didnt even think of it . Was fine manouvreing UPWIND . But used a bit of juice .

So THATS Swept Flap Hinges . Digest in morsels r youll get indegestion . See you dont choke . SET A FEW PARRAMETERS and ARRANGE THE REST to SUIT . theres no ' one sixze fits all ' .

The throw the componnents on the floor & get a bit of chalk , got Coppers a few World Championships . . F1 Grand Prix . BALNCE & PROPORTION is whereitsat . Mate .

A Genisis Three with a funny fuselage , and Bob's your Uncle .

( Hunt swept Hinge . hope bob chimes in with his observations , Has Flown Bill's Juno , too. I think . )

To the Field once or twice , down the sheltered street , the sprint across the main road in a lull , and across the gap to the lee behind the 12 foot hedge , crouched sprinting holding tight with all fingers & toes
did the trick .

I believe it was some time before someone got a 300 kph lap out of a .15 on straight fuel .

THUS : a few comments regards ' flying in the wind ' have some grounds in fact .

Power , Yaw control . ( Balanced Fuse. Side Area . ) I find with a flat wing , C G & leadouts at near the bellcrank pivot , the reliable waytago . One can even ease the C G Behind the pivot .
A ROUNDED ( fully ) fuse is less implicated in the cross wind effect . To big a rudder or nose , will act as a vane or suchlike .
As In lowish Fuse side Area , and not a oversized rudder , will get it stable in yaw , for a flat wing .
Diheadral your better having it 5 ton And good stiff flaps , Elevators & controls . Like a 2 kilo 630 Sq. in. M B 3 . and wear a helmet . Obviously 18 thou. lines are a minimum , billowing over 18 Knot wind .

FLAP SWEEP . if its got a TON put a RABE RUDDEr onit . while yer buildingit .

Bill Schluckbier · « **Reply #7 on:** April 28, 2024, 04:51:19 PM »

Bob - Thank you so much for taking the time to post a reply. I really enjoy reading the history of how the design choices came about; it provides them with context.

Thank you,

Bill

doug coursey · « **Reply #8 on:** April 30, 2024, 02:51:51 PM »

HERES A VIDEO OF WINDYS SPITFIRE WITH SWEPT TRAILING EDGES

Steve Helmick · « **Reply #9 on:** April 30, 2024, 04:24:11 PM »

When asked about that (swept forward flap hingeline), Paul Walker said it made trimming MUCH more difficult.

I'd leave it at that, but considering that a lot of models are flown for years and still aren't really well trimmed, it makes sense to just don't do it.

Steve

M Spencer · « **Reply #10 on:** May 09, 2024, 12:29:44 AM »

But if ya gotta do it ! , its gotta be done , as in if your trying a semi scale somthin , it CAN be workable , even a Non semiscale somthin , like the Genisis III , Crossfire cetra .

The Typhoons butchered for a ST 60 from the previous RV OS 80 , considerably smaller motor , but 15 5 nitro and it swings the 12 x 6 Master three blade o.k. .
The engine bay work swa the C G go way higher , or somewhat higher , unforseen . ( shifted beares from under drop in from top engine with top cover , to
cowl from existing underside , angle cut . Bearers etc OVER ( above / underslug ST 60 ) with the front cowl now LEAD . as its 12 Vs 18 Ounce . And a ounce in the lower lip .
AND a heavy spinner dome nut .

The previous swinging in triangle bottoms , on these things , is largely eliminated , going to .016 solids instead of the .018 seven strand steel lines . Less drag & inirtia in the wire , and less weight maybe .
Last flights on the typhoon had it a slight weave / kick in the hourglass bottom , eased but still tight . V tight if you say you caint doa fivefoot corner .Slight wallow . Similar slight wallow in tight Sq inside
bottom , but ased / opened - no swing .
Got non adj. leadouts with 1 3/4 od spacing . SO . . . . Id thought it now 76 Ounce , but the scales say 82 . plus 5 or 6 ounces of fuel .

Oh Dear . I think it's 630 sq in odd . Very odd .
So if it can do it ( the schedule ) at that weight , resonably well . ( Better control - steerability - accuracy than a 64 oz Magnum with soft flaps . Theres no harm trying - if your willing to persevre and chop
things about , if you were to preocupied to install during the ' build ' . ( Wobbly rudder - adjustable leadouts ) Noext Time it'll get it . Figure I could hit 54 Oz ( 1/16 th wing , mouldded fuse & rear surfaces )

Spit on 11 x 5 1/2 on a mega rich flight 4 stroked pre igniting ? maybe ( only one gasket , 10 % nitro ) on a motor Ive had from new . So pulled to check bearings as slight brown Exhaust residue .
Or course , the replacement motor wont give the same run . So , ONCE it's rebearinged , watch out . Was 5.2 or 5.4 more likey . An estatic flight wot hit the mark . the .016s , turning well grooving , no swing.
AND I forgot the spinner Wt. nut on the uva mota , so it missed the mark on all that too .

Which is why reputable souls keep a NOTE BOOK of ALL SETTINGS , so were told . and in M'Cyle racing . Particularly !

Another Notorious Example , https://stunthanger.com/smf/at-the-handle/oscillations-around-the-roll-axis/msg640718/#msg640718

Told by Brian ' Flys seven degrees Nose Out . You look straight down the inboard leadingedge - flying it ' ( nutha reputable says ' they ( F C ) Dont do TIGHT corners )
But if you want to get hysterical , THAT means the outer flap hinge is nearenough straight , whilst the inner hinge is raked to billyo . Which must do somethging , aerodynamically .
But Since Its Teathered !! Maybe it flys an inner wing and an outer wing , as two interconected dissimaler raked surfaces , aerodynamically . But anchored ( by lines ) and somewhat balanced Vs loads .

Know Nuthin on This , aerowise . Plans on one of the ' free ' sites .

Therefore ' addition ' of raked flap hinge , with no other variations to a existing design , may not cut the cake , a THINK about the whole cabbodle as a INTEGRATED concept / design , might get you into it .

Having purloined the drawings for THIS , and tripped over some cheap light 2 1/2 spinners ( $ 2 ! 2 & a something , anyway . Think 2 3/8 does it .) Finally Figured INBOARD tanks , on a profile test ship . maybe .
One mighta noticed ALL Al's semi scale things ve got Raked Flap hinges , so the previous remark , You Might NEED to use raked flap Hinges , could hold tho the Berringer's didnt were less scale . take yer Pick .

THIS : ( Id been burning a gallon a week ) First Time Airbourne ,

Was Loops , Outside loop into Sq Out, into Sq 8 , then hourglass , wingover , clover repeat & other things . Good Evening Air . Thrown by Ex RAF Machanic from Biggles Day . Reapeared , With " Not Bad Eh . Not Bad " Which I though a high complement . Not a word on the castor smoke pouring aft , in his best blazer & tie . Followed Instructions . Clean Launch . So , The RAKED FLAP HINGE isnt always totally abysmal .
The 2 metre one'd be going now , if I pulled my finger out , for a week .
As part f a ' concept ' it can well work well . One or two whove tried it have won a thing or two withim .

Bill Schluckbier · « **Reply #11 on:** May 09, 2024, 10:13:49 AM »

Air Ministry -

Thank you for posting the photos and your comments. I had seen photos of the Firecracker and Bandolero before; I believe in the PAMPA magazine.

Bill

M Spencer · « **Reply #12 on:** May 12, 2024, 11:16:02 PM »

The Bit between the teeth ! .

The braincell moves on from the last point , SO ;

Cogitating , it becomes evident , that PERHAPS . As the drag of the flap at the tip is Further Forward , the tendancy to swing ( yaw osscilation ) might be slkightly greater , acording to the degree of flap hinge sweep .

THEREFORe perhaps a touch more aft area / longitudeinal stability / weather vane effect , as in Fin or Aft side area , could be required to ' balance things ' again if say a Std set up was modified with / to a swept flap hingeline .

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' We ' come to this , as ( Contry to somes observations ) Ive Found the Diheadral set up ship , is generally more ' locked in ' on OUTSIDES . Presume the wing channels the airflow in a tad ( like the flap sweep trip )
so as they sit well and hgold the air . whereas on INSIDES they tend to skid - in the vertical - as airflow sweeps out and off . All but the Hurriane have this tendancy . Under Pressure .
Stinking hot day , bad engine run , or pilot not showing consideration to smooth & measured handle opperation ! .

as in if yr a bit rough , she's o.k. on outsides , but lets ya know ona da inside squares .

The fancy ' lifting ' section At the ROOt can mean the FLAP at low deflection , in rounds , is more favourably aligned , in outsides , giving noticeably better lift in the bottom of the top outside in the vertical eight .
Allowing darn good ' hold ' and transition , smoothly , to thew lower inside . hurricane again better here , but the diheadral & flap sweep on the ten ton typhoon , alows it to do what no man would think it could .
82 ounce bigeezes . Shouldnt do nuthin .

---------------------------------------------------------

Theres oily Fircrackers , like THIS . Which theres a published plan for . And Later Firecrackers . AND a .35 firecracker plan .
Alan Resinger

These Below being the later one :

Heres a bitonit : https://pampacl.org/wp-content/uploads/2020/02/SN_Magazine_-NOV_DEC_2007.pdf theres a 2006 / build on Hoffmans , in stunt news . for a few strucyure photos ?

Bill Schluckbier · « **Reply #13 on:** August 05, 2024, 12:14:48 PM »

Hi -

I just noticed you reply, a few months late. Thank you for the information and my apologies for the lateness.

Dave_Trible · « **Reply #14 on:** August 20, 2024, 06:44:23 AM »

In scanning over Scientifictions stuff from above a light went on (dimly) in my head. He was talking about the airplane flying in an outward skew and that then making the swept trailing edge outboard nearly parallel with the lines, tangent to the flight path and then the inboard side more seriously raked forward, which would present that wing flap ahead of the outboard side and turned to accumulate more of the waining boundary layer to work with. On my Neptune and other classics from that era that used swept edges, very little to NO tip weight is/was used. Perhaps the differences in lift side to side more or less negated to need for tip weight......hm....that would also be true to a much smaller extent with the straight TE. It may also be a source of confoundment in the trimming process-attempting to use tip weight as standard fare when it might not be needed...

Dave

doug coursey · « **Reply #15 on:** August 20, 2024, 07:45:09 AM »

WHY NOT SWEEP THE ELE TRAILING EDGE ALSO

Chuck_Smith · « **Reply #16 on:** September 17, 2024, 06:58:00 AM »

I can only speak from my own experience; my Bearcat has both a swept-forward TE and dihedral. It glides through the pattern pretty effortlessly. Now that said, it's a profile with a GIANT fuselage cross-section so the dihedral is likely having a very minimal Dutch roll effect. It also has a boat-load of tip weight.

In theory I don't think a swept fwd TE will have much affect good or bad other than moving the MAC around and moving the plane's CG point forward a little. It does however, complicate the heck out of linkages and add complexity to your build. I recon the reason we see straight TE hinge lines on the "99th percentile stunter" is that it makes it simple to rig the flaps.

From a retired aero-guy perspective, I tend to worry more about the taper ratio and aspect ratio than sweep. Controline airplanes are weird due to being tethered to the earth so you need a stiff drink before you start thinking about inertial reference frames and relative wind

Without flaps? Swept fwd TE is everywhere in combat and the old Sneeker, Shoestring, Ringmaster and many more have a swept fwd TE and they fly (for what they are) pretty nice IMHO.

YMMV and that's cool, it's an interesting discussion.

Chuck

Author Topic: Another odd question - Forward sept wing trailing edge and flap hinge line (Read 58095 times)

Bill Schluckbier

Another odd question - Forward sept wing trailing edge and flap hinge line

Dave_Trible

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

doug coursey

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

Bill Schluckbier

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

Brett Buck

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

M Spencer

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

M Spencer

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

Bill Schluckbier

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

doug coursey

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

Steve Helmick

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

M Spencer

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

Bill Schluckbier

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

M Spencer

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

Bill Schluckbier

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

Dave_Trible

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

doug coursey

Re: Another odd question - Forward sept wing trailing edge and flap hinge line

Chuck_Smith

Re: Another odd question - Forward sept wing trailing edge and flap hinge line