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Author Topic: Twin Prop Direction  (Read 2272 times)

Online Ken Culbertson

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Twin Prop Direction
« on: April 25, 2025, 10:38:48 AM »
I have heard that the rotation of twin props matters.  They naturally counter rotate but which one should be the clockwise and which one should run the fastest?   

Ken
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Online John Miller

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Re: Twin Prop Direction
« Reply #1 on: April 25, 2025, 11:35:16 AM »
The outboard motor is often set up to be a little faster than the inboard. As for prop rotation, most often used seems to be where the props rotate towards the top of the canopy, but your tests will determine exactly what is best for your design.

Speaking on this subject, I'm not sure that opposite prop rotation is so important that I would search for a special crankshaft to accomplish that in an IC powered twin. Unlike a full-scale twin, Gordan Delaney's red "Twin Pathfinder", a model stunt design, uses standard tractor props and flies very well with that set-up. My own version of Mark Fechner's Classic Twin Flight Streak", Uses a pir of OS .20fp's both turning in the same, stock, direction with no problems that I've seen.

I personally would try it both ways on an E-powered twin, where it's much easier to have opposite turning motors.

John M

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Online Ken Culbertson

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Re: Twin Prop Direction
« Reply #2 on: April 25, 2025, 11:52:11 AM »
The outboard motor is often set up to be a little faster than the inboard.

You would think that you would do the opposite to create better line tension, especially overhead.  I have the outboard running slightly slower than the inboard.  The plane pulls like a mule.  I like pull, but I could live with less and I know some others that will complain when they fly it.  Perhaps your recommendation is worth a try. 

Ken
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Online Dan McEntee

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Re: Twin Prop Direction
« Reply #3 on: April 25, 2025, 02:49:48 PM »
  When Walt Brownell was building his first twin electric model, he would come into the hobby shop and we talked about that, wondering what would be the best for flying stunt. Walt was an aeronautical engineer and he said, I think, that common practice with twins that had props that rotated each direct, the norm was to have the tips turning out, away from the 12 o'clock position. just quickly searching a picture of a P-38 Lighting, that was they way they turned. I remember reading somewhere that Britain got some early P-38s as part of Lend Lease, but they got versions where bot props turned to the right, clockwise, as viewed from the cockpit. They reportedly did not like those at all and sent them back, as it were, when the P-51 was further developed. Walt experimented and test flew numerous combinations. I think he settled on a 10-6 electric prop that was cut down to 9-6, and he liked the tip turning in towards the canopy from the 12 o'clock position. He felt also that the flaps were much more effective with the prop blast going right over them from the leading edge of the wing more or less, so he made the flaps on the second model smaller. That didn't seem to be affected by prop rotation, but did feel that tips turning in was better.
   I always want to built a twin with counter rotating props just to feel what it flew like. I rounded up parts to build some Fox .19 and .25s that had left handed crank shafts, but haven't gotten to that project yet. next comes a Jack Sheeks Mosquito that would have two LA.25s or FP.25s but left handed cranks can't be found. I have acquired an Enya .30 and another that has a left handed crank so that project may still get done. it's all just in pursuit of finding out what it feels like.
  Type at you later,
   Dan McEntee
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Online Ken Culbertson

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Re: Twin Prop Direction
« Reply #4 on: April 25, 2025, 03:15:18 PM »
   I always want to built a twin with counter rotating props just to feel what it flew like.
I have maybe 10 flights of sorts.  Not quite a pundit yet but I can tell you that it is quite different.  Mine is inline with a canard up front so some of what I am liking may be that.  One thing that has totally surprised me is the lack of wake turbulence.  I can't explain it but it is just not there.  I expected double and got half.  The sound is fantastic.  Now I know why Paul flies quads.

Ken

"I think, that common practice with twins that had props that rotated each direct, the norm was to have the tips turning out, away from the 12 o'clock position." ... that is how mine turn now.  I will try reversing it next time out.
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Offline Trostle

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Re: Twin Prop Direction
« Reply #5 on: April 25, 2025, 05:51:49 PM »
I have heard that the rotation of twin props matters.  They naturally counter rotate but which one should be the clockwise and which one should run the fastest?   

Ken

The following probably has little to do with what is the best prop rotation for twins.  Regarding the deHavilland Hornet:

"Many of the difficulties induced by fitting high powered engines and handed propellers centered on longituginal and directional control and stability.  Airscrews rising inboard were triied first since they were preferable for fore and aft stability, but they blanketed the rudder at low speeds and rendered it ineffective for correcting swing on the ground.  Airscrews rising outwards were there fore fitted which initially showed unacceptable stability but the problem was solved by careful use of weights and correct size of tailplane."

(Various publications note that pilots gave highest praise for the Hornet's handling capabilities.)

The P-38 went from same rotation propellers to counter rotating one way and the counter rotating the other.  I cannot find the reference to this right now, but I do remember for the P-38, it ended up rotating the props opposite of the Hornet.  I think it had something to do with the twin booms and the horizontal stabilizer why one way was better than the other.

In each case, the different teams were apparently resolving different problems.

Interesting stuff.

Keith

« Last Edit: April 27, 2025, 03:16:26 PM by Trostle »

Offline M Spencer

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Re: Twin Prop Direction
« Reply #6 on: April 25, 2025, 09:32:41 PM »
When you notice you havnt got it , is when its trying to climb out of a hole in the air .
full power Acceleration / power burst ,  when the lines arnt tight , can do a hard left
and three snap rolls , Make you get out of its path . Can Bite .

' Bump ' starting gets your fingers clear , to . Dont want to flick into a running engine .

Online Dennis Toth

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Re: Twin Prop Direction
« Reply #7 on: April 27, 2025, 10:14:16 AM »
I think you should contact Bob Hunt (he is on this forum) regarding this. He has built quit a number of electric powered twins and tested all configurations. As I recall one of the things he did confirm was to run the inboard motor a bit faster than the outboard to get better line tension.

Best,    DennisT

Online Ken Culbertson

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Re: Twin Prop Direction
« Reply #8 on: April 27, 2025, 10:51:59 AM »
I think you should contact Bob Hunt (he is on this forum) regarding this. He has built quit a number of electric powered twins and tested all configurations. As I recall one of the things he did confirm was to run the inboard motor a bit faster than the outboard to get better line tension.

Best,    DennisT
I have spoken to Bob about this, and he does recommend running the inboard faster for that reason.  My setup is very similar to his latest twin using the same motors and being inline.  I suspected his setup would be right for a very light plane but with even a slight difference in speed the pull on my 70oz beast is far more that I need to be comfortable.  I wonder what others think of running them the same speed or even with the starboard running a bit faster.  I think my next test will be with them equal and start increasing the g-force settings instead.  I was hoping to pose this question to Bob as a chat on the Zoom meetings, but he hasn't been on in weeks.

Ken
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Online Lauri Malila

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Re: Twin Prop Direction
« Reply #9 on: April 27, 2025, 11:33:18 AM »
I have no experience of the subject, but I’d think that you must first decide if you want to create more line tension with rpm difference (and together with it possible trimming anomalies) or do you want harmony.
In the latter case I’s start with slightly more rpm in outboard engine. How much more, can be calculated from how much longer the outer motor travels/lap.
For example, if the motors are 10” apart, the outer one travels 62,8” longer/lap. Then just calculate the difference in percents from line lenght and adjust accordingly.
Maybe that gives a starting point.
L

Online Ken Culbertson

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Re: Twin Prop Direction
« Reply #10 on: April 27, 2025, 12:39:07 PM »
I have no experience of the subject, but I’d think that you must first decide if you want to create more line tension with rpm difference (and together with it possible trimming anomalies) or do you want harmony.
In the latter case I’s start with slightly more rpm in outboard engine. How much more, can be calculated from how much longer the outer motor travels/lap.
For example, if the motors are 10” apart, the outer one travels 62,8” longer/lap. Then just calculate the difference in percents from line lenght and adjust accordingly.
Maybe that gives a starting point.
L

I like your idea.  I was already thinking that direction.  I am of an opinion that any line tension that is not produced by centrifugal force through a properly placed leadout guide and tip weight is counterproductive and will produce unwanted drag and or yaw.  I could be completely wrong but that is the way I am currently leaning.  Your post made me realize that even if they are running the same speed, the starboard motor is actually running "slower".  A very light plane such as those Bob builds may need that differential in the overheads.  As long as I keep my speed up (5.3-5.4 ish) I don't.

Any thoughts on prop rotation direction or wake turbulence?

Thanks - Ken 
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Offline M Spencer

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Re: Twin Prop Direction
« Reply #11 on: April 27, 2025, 08:21:08 PM »
Saying TWIN is like saying SINGLE ENGINE . Theres a bit of variety going .

Theres certain factors , that influance things . I think ' Prop wash ' well clear of fuselage , is one to consider .
Side Area Distribution another . Straight Edge across the prop driver / spinner Backplate , as it were , to ensure none whatsoever inset . Straight Inbd. A hint off offset , outbd . 1/8 or 1/4 in. from in fwd. on ruler .

LOWER PITCH PROPS are definatel an assett .

If the inner wing gets ' waked ' watch it . The Mosq. spun out a few times from inverted on the outer , recovering . or not, as the case may be .Ten Yards of SIDE AREA sat out there marvellously , in contrast .


Offline M Spencer

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Re: Twin Prop Direction
« Reply #12 on: April 27, 2025, 08:32:31 PM »
Talking of P-38's ,



This Here has ( had ) a thickish airfoil , good grip on the atmosphere .
Capeable . Usless on 9 x 6 3 bl . good on 10 x 4 3bl . Olde OS 35 - S .

Gotta wingover outta it . On the OUTER . and a few loops , inside and outside .



flew Backwards , which could be a head doerinner , but usually CLOCKWISE .  LL~

Energy Conservation , Momentum , and the olde flick of the wrist , like a stock whip
or fisherman , is part of the equation . 2.25 kilo might be 88 ounce ( wince ) WAsnt
AS LUDICRIST AS IT SEEMS . ( AHEM )  675 / sQ IN  . INNIT . wHEREWEREWE .


Offline M Spencer

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Re: Twin Prop Direction
« Reply #13 on: April 27, 2025, 08:36:59 PM »
Side Area ( test ) Zample ,

AMPLE is better stability than lesser . 262 V Good . Whirlwind , Smooth & watch it . Mosquito - Dont let it catch you out . tho the Fun is in the reverse oida . If you dont mind leaping for your life , on occasion .

Offline M Spencer

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Re: Twin Prop Direction
« Reply #14 on: April 27, 2025, 08:44:26 PM »
And IF you have to keep richining the inner , for the same rpm . many turns , and It Gioes Way Rich as he letsit GO , OS 35s on 10 x 6's

The Inner goes full rich & the outer from four to flat chat , as it leaves his hands , there May be Trouble .

So , If Something needs adjusting , DONT . Find Out WHY it needs adjusting . Before attemting aviation .

Offline M Spencer

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Re: Twin Prop Direction
« Reply #15 on: April 27, 2025, 08:53:27 PM »
And JUST TO RUB IT IN ,

This Flying wing Fence resembles a Me 262 . The one that resembled a Nf 11 Meteor , on 15 thou new Sig Lines  . ( The Fuse. was 58 inch long ) stretched the lines several inches & had 1/4 round delayed reation , duetoit ,
In EIGHTS . Which got intresting . Wheres my Aeroplane ? behind your head ! outa center of voiticle 8 . So see yive got secure wires , omit . Not elastic .



them There Tanks wot go INSIDE the Spraybar , in the plan view . Should go full rich level , full tit overhead . set so she dont ' go dry ' overhead , and your home & done .

thisis thenew setup onit . Might take it to the Vets Gathering , despite being striped , as rattle can colour chart TEST ! ( Tho dont wanna get ether oily ) The Westlands sanded and faded , shoul hitit w8ith CLEAR
and bringit too . The de H , below , I dinnae wanna putta Mark On , atall . Being One Flight knew .


Offline M Spencer

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Re: Twin Prop Direction
« Reply #16 on: April 27, 2025, 09:21:55 PM »
RIGHT , wake - WIND , wubbish .

Yr ANGULAR YAW in the gusty stuff , is about the same . That 38 , the 40 inch Cr to Leadout guide  had a RESTRAING wotsit , out there .
She was quite stable , a bit of yaw in a shifty breeze . The REULT could be FELT at the handle . Thje guide pulling the lines fore & aft ,
say two or four inches ( at the tip )  Wheras it woukldnt go much past Six Inch there ( seven V max 0 as The resultant  ! Line Loads
Restrained and , when it was ' working ' rather than ' dithering ' , the restraint at the tip , was more active . dynamic ! Secure . WHEN the Injuns were ' right on ' . Remeber the outer injun  manouvres ,
and handle whip / lead - dynamics . Blah blah .



Id been flying five million times a week ( well , a gallon anyay ) back then & gone tru about twenty , or thirty .
the beeg wans 78 in, two metre . Max. FAI span ( The changed to this as jelous of P. W.s B - 17 , in my opinion . )
The red 67 one took off , throw by a W W II Spitfire ground crewman , in his blue best blazer . walking his dog .
Think it was , level , level, level , loop,loop, loop , inverted , inverted half loop level , outer roud , nuther alf, Sq Sq Sq ,
into sq 8
wingover , hourglass , cloverleaf , etc repeat & so on . G R O O V E - ie , turns , stops flat , steady , light controls . and glides ook too .

So there we are . The TENSION on the big one is just the same , LIGHT & STEADY . fingertippy handle type like . in calmish air .
NOT really a gusty air ship , It SITS in the yaw/roll , dragging at the wires . on da liddle one , tips jumpin about six or eight inches .
There Ya Go .

BUT , in GOOD AIR the puls about the weight of the model , on both . a bit under . mmaybe a bit over - with the wind behind it .
Whirlwinds Fiirst flight was in country breeze STRETHING the .015 solid lines . INCREASING handle spacing reduced proportional variation , so lost porpoise , onna da nextone, that day .
( we wont mention the Hurricanes first was in 20 to 30 , steady , or that it was  L E A N , or that the C G was way back . or that when the engine ( finally ) cut , 1./4 lap & it was downind.
control reversal . Just as well the GRASS WAS LONG , soft , moist , ( v good fodder ) and that it landed itself post dusk , unscathed . Mate .

The Moral of this story is that NO TWO ARE THE SAME, unless theyre the same . even If theyve got the same wing , and other things . USE LOW PITCH , to desemble Tourque Steer .
Dont Panic , jog 20 k before flying , to loosen up . No drinking for at least a week beforehand . and watch what you eat .  ;D ( one or two might be a bit over the top , but neverthelesss . . . )

This eres the 67 in. one , wot doneall THAT . Two crankey fox 19s with ' racing clearances ' ( loose ) wot ive stillgot . some aussie louse trashed it . Voimin , Brain Dead bimbos & maggots .
Half the countrys I Q is below 100 , and there ancestry dubious . Manners abysmil . domesticated rather than civilised . not in all cases , tho .


Offline M Spencer

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Re: Twin Prop Direction
« Reply #17 on: April 27, 2025, 09:27:24 PM »
this explains why the australians are so cheerfull . or is it feeble minded .judgeing by the Road building these days .
Were magnificent works of architecture on the railways & buildings by the convicts . standards are slipping .





SO , the moral of this story . IF ITS MUSHING , youve GOT TO ' Watch It ' , be on your tippy toes , tickly at the andle , prance aboutabit , ballet like , stepping back and side stepping .

BUT

If it pulls like a mule up down and sideways , dig in hang on and steer it . But IF THE AIRS DRY   ( relitve dencity ) do the dance routene trip .
the 262 did the best schedule known to humanty , at Musswellbrook , The Bloke supposed to be FILMING IT , only did stills. i was told on landing .
As he didnt know how the movie bit worked , onisnew Camera . ( fume exasperate , steam out ears and so on ) Minor stepping About & Slip steam avoidance was required, in warm stillish air .
As It was 70 OUNCE ( oriental WING ) 2 OS Max .25 plian bearing 70s things on 9x6s or 4s , on 70 foot f 7 stand 18 thou. steel . Wotit Needs to STEER STRAIGHT Zactly with the andle . MATE .

So there .

And dont mention the Aboriginals .  ;)


Offline M Spencer

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Re: Twin Prop Direction
« Reply #18 on: April 28, 2025, 12:15:38 AM »
Quote
First, when you decide not to use opposite rotating engines used as an improvement to a linked rudder, I consider that a significant change from the original design



Ahem .



Quote
The engines were as large as the rules of the time permitted and offered the possibly of the pair of them being able to produce more thrust than a single engine of similar total displacement.  Also the engines are opposite rotating which eliminates undesirable effects of Gyroscopic Precession, and P-effects.  No movable rudder would be required as there is no propeller induced yaw to be compensated.  The sound of two of stunt engines singing in pair should also create a favorable perception.



Theres a ' Pre Cut ' file , for this , 60 span . If anyone can handle it ? . Please ? . ( Be a bit easyer ' profile ' , but there you go .  COUNTER ROTATEING CRANKS .

NOW ; wot ees on about was during ROTATION ( Tail down to tail up , on takeoff . AND as tail drops , on landing )

IF the Pilot knows this & COUNTERS the effect with the rudder , He can invent the interconected  rudder , for Control Line .

Which will still work with both props right hand . But He'll blow a fuse if you think you should use it with Counter rotateing Propellors !
==================================================================================

Therefore , ' Mush ' -  Vertical yaw ' , Brings in the ' P ' effect . also Powering Up , acceleration , as all forces have an opposite and equal force , out of a ' Air Pocket ' can have your undivided attention , if you still have any left . In an Instant .

So , the Answer to the question is one or the other . If your pushing it , Have a go . With the rudder or props .
What Al Did .
https://airfactsjournal.com/2021/10/mustang-musings-what-its-like-to-fly-the-legendary-p-51/#:~:text=Immediately%20after%20takeoff%2C%20the%20pilot,particularly%20during%20takeoff%20and%20landing.
Quote
P-factor:
At low airspeeds and high angles of attack (when the propeller is angled more vertically), the downward-moving propeller blades on the right side of the aircraft experience more relative airflow than the upward-moving blades on the left. This asymmetry creates a torque that causes the plane to yaw to the left, as if being pushed by a force.

OH NO , it dosnt . It Causes ASSYMETRIC THRUST . or s that metric . OFFSET . Unqequal . more here than there . Side to Side . Depending on what way your going , with the nose. Up or down .
So it'd yaw going into the mash, as it went . Also opposite , as it went out .

The easy answer is get clear of mush ! and air pockets .

BUT if its a All Weather Comp. Ship . you may have to take things a bit more seriously .
The Lancaster & P - 38 trimmed nose heavy toward Max. Speed . downhill . THIS is why the prop rotation was selected , to lesses the nose Fwd. Trim . So it might come out off it. On later models !

« Last Edit: April 28, 2025, 12:50:27 AM by M Spencer »

Online Ken Culbertson

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Re: Twin Prop Direction
« Reply #19 on: April 28, 2025, 08:04:19 AM »
.
The Lancaster & P - 38 trimmed nose heavy toward Max. Speed . downhill . THIS is why the prop rotation was selected , to lesses the nose Fwd. Trim . So it might come out off it. On later models !
:! After getting your post translated into American ( LL~) you may have just answered a question that has been bothering me since the first flights of the twin.  None of my designs have ever had a problem with the 2nd corner of the hourglass.  This one does and although it recovers immediately and is not even visible in slow motion on video it bothers me.  I think the direction of the prop rotation may be the issue.  I had never considered the vertical effects of "P" which are not cancelled by counter rotation, especially with it inline.  With the plane on knife edge vertical becomes horizontal.  This is one of the reasons some single motor planes fly better running clockwise. So, you have put me onto something...or not.  At least it is worth changing the rotation from tips out to tips in to see before I resort to traditional trim to mask it.  So, I will either fix an issue or murder some innocent electrons.

Thanks - Ken
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Offline M Spencer

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Re: Twin Prop Direction
« Reply #20 on: April 28, 2025, 07:50:30 PM »
Yea , stir things up , you work your way through the inane drivle & the odd piece fits . Further steps along the path , as it were .

Flying the second hourglass corner ' Hard ' ( slamming it - on - off at the handle ) is not a good idea .

flying it either slow to full , and slow off , for the top leg . As in a measured deliberate ' easeing ' to find the breakaway point ,
or flying the corners as rounds - to see if it the carries tension even through the lot - Sometimes you get your arm full out -
by the first top corner - and draw it down as you go across , stepping aft as you turn into the downward leg .  :P

Tip weight . Turned to Al rabe & hit ' show all posts' . tho like usall , He gets off track a bit or Has his own perception ,
theres some thought through trails of explanation / logic - Enlightening as to aerodynamic effects  & mass / inertia / & reactive resultant THING .

theres only four pages - I printed off one or two - He gets into reverse props - a bit . And TIP WEIGHT . If you throw too much in , get hingeing , then pull it back .
But in windy kiwiland , a hint off hingeing keeps you going . Rather than spinning out and piling in . ( Like a certain bue aeroplane could snap into )

https://stunthanger.com/smf/profile/?area=showposts;u=882

Is your plane a ' Two Much " , with adjustable leadouts ? . ( My Spitfire - engine Swapping - St 60 /51 SF46 seems a bit critical on C G , with fixed leadouts . Spot On ( matched )
it does marvelously . Nose or tail heavy it starts yaw roll . Tho it needs the toolbox sitting on the inner wing , plane inverted . Beforehand . Wash IN on the inner screwws it compleetly .

A degree and a half washout on the hurricane semi acale . It Floated through the top of the Vert.  8 ( Outside loop over 45 deg . As in ' Sailed through Nicely ' all by itself , so you could ' catch'
the reversal point at the handle for the lower inside , as iff you had all day . This THING was V good , undisturbed - By reasonably steady highish winds . 15-18 and steered good in even higher .

The discernable wash out on the low wing layout presumeably was a major contribution .

Quote
Seventeen months passed before engineers were able to determine what caused the Lightning's nose to drop. They tested a scale model P-38 in the Ames Laboratory wind tunnel operated by the National Advisory Committee for Aeronautics (NACA) and found that shock waves formed over the wing when the airflow reached transonic speeds causing turbulence. Also the aircraft nose would tuck, because the downwash over the tail diminished, creating greater pressure on the bottom side of the horizontal stabilizer. This could be remedied by adding full elevator up trim, and sometimes the aircraft would recover at lower altitudes as the air density increased.

Blah de Blah . Ive tended toward the + tailplane incidance , on the highish placed tailplanes . He rattles on about longitudeinal diheadral , incience & downthrust , on a longer post ( I just checked a few longer ones there )

I think , maybe , if youve gone Zero zero Zero , theres your culprit . It may need the old 3/16 across the full surface , back there . You put a  L O N G  stick across it - fore & aft . Or two , ea side , pack parrallel  .
to see she's say 1 1/2 degree positive .
you generally gottra run offset on the outer . inboard stright , maybe . ( depends upon the ship - the more side are little ones seem way more consistant ) THOUGH the big P 38 was too , with naff all side area .
Next One ? will have fixed Outer Tailplane ( outside booms ) as i think itll work better like this . Make the pilot less strung out .

I take it its ' dropping off on a wing ' into the top leg , up there ? ( Still steady through the top of the Vertical eight though ? ) Id built the P - 38 to fly clockwise - cause off the dual tourgue prop bit ,
Havving been having the Mosquito flying the pilot on occasion .

So THATS an Answer , Too !

Same wing ,, ( 6 in shorter , thinner same airfoil ) on a Mewgull , in a stiff steady breeze , would increse speed ONLY ( really ) in the Square eight , faster out of each turn . THE POINT BEING
it ' THREW ' the outer , in the last center top turn . AS IN - it did a big gyro yaw and put the outer up a foot . and the inner down a foot . IMEDIATELY picking itself up , Straight before 1/4 of the top leg was done .

Nuther drivle was in massive cross wind - downfield to 50 foot alt. Across diagonal above - wind shear / two distinct levels . this thing would sail round in a deep 4 stroke - on 15 or 20 %nitro on a 12 x 6 .  :P

AT the wind shear Level in the ' downwind ' leg off the overhead eight = Massive ' ROCK '- One Sine cycle . i think near 18 in down the 12 in up inner tip . scarey. At First . but as it gave a BIG TUG at the handle
as it did it .
It Wasnt a trouble . in retrospect .

First time did a O Head , when the engine had settled in , Thought I was going kite Surfing . Needs a Distinct restraint on the muskly arm . Pulls It to full stretch ! otherwise .
Blahdy Blah .

Center OFF Cravity . The liddle Phntom wiff za Lost Motion 3/16 slack at the T E , runs the C G 3/4 Aft on the plan its a rip off of . Grooves & turns V well . get rid off the orrible slack , and it wont do nuffin proper .
no Matter what  .

THE IDEA being . try throwing the C G BACK ( use (extreeme ) caution ) and conversely , Fwd . A couple off ounces strapped / taped ( plasticine ? ) on the nose . Try 1/4 oz or something - try it 1/4 & 1/2 inch aft ,
off where your at . Tetitively . See if it jumps around and bites . Or starts purring and rubbing your legs  :o Like the Mosquito . BEWARE - Danger will robinson. Danger . etc . It Its Tryn to put ITS NOSE IN .

the Arm Out , Flick off the wrist , AS You Side Step - right left - one pace - aS YOU TURN into across and draw arm down , and step aft into the downhill corner .  AAARRRGGGHH .  Literal .
rough the Phantom'd cut loose and make ya run TWELVE TIMES in a Flight . After you got back from the townies Torture Treatment . Steeping Clear , Taking several deep breathes , and muttering smoother smoother
after youd opractised your Ballwet steps ( with noone looking ),
We might exagerate a bit their .
BUT
it was the Phyce ' ahead of it ' slight easy 7 light touch , at the HANDLE that would get you through ANYTHING .
Whereas The Big Long wing thing's , HAMMERING the Lower Turns , and then others , in Squares and wingover,
was the norm , Easing OUT of the lower corners , and it'd have no bobble . Slamming em , 50 % either Way .
good or Bobble , So the EXIT from the Square was where you needed  to pay attention - Concentaqte . Particly when tail heavy .

one further last rattle - the excellent little red TWIN  . one muffler fell off , & it had a slight porpoise , Both & da Definate . Level at four or five feet Alt. Flat .
One and it'd eaee at ten foot . both a bit higher to sit striaght .
The VETERAN ' old time stunt ' GROOVE ALTITUDE . =   =   =   =   =  center of gravity = = = =  = Maximum Aft . = = = = = TEST

All this full size shert , they ESTABISH the Maximum aft. C.G. LIMIT .
As it goes back , somewher the stability starts going DIVERGENT .
as in it POROISES . ( waggles the stick , your head & neck . then trys to throw you throughj the canopy )



In this Book , he talks about POSITIVE STABILITY being a prerequite to SMOOTH CONTROLED aerobatics . Aft C G & it jumps about like a jellyfish .

SO , Thrustlines . vert & Horizon. CHECK .

Rear End incidance CHECK .

Explore and establish Working C G . tickly with respect to Dead Zone elevators or & free controlled movement of FLAPS . ( for groove ) BEFORE elevator starts moving !

Typically Hold the elevator - and the flaps go 1/8 before it cuts in . FLAPS HELD SECURE - 5 mm freeplay 2 elev. T E  . equal about neutral .

i put a flattened brass bush , in the elevatorn horn , on the p 51 , and it cured its waywardness . Means you can SLAM a Corner  & it EXITS CLEAN .

As your nervous reactions at the handle , are only controling the Flaps / Lift . NOt the Pitch of the fuselage . So she dont porpise , turns hard , and exits clean , on an aft Center of gravity . MATE .

and seems less critical of leadout setting with it ! And Dont forget the TIP WEIGHT TEST .

read through Al's diatribes , before endevouring to digest other than the Salient Points . They always have sore heads , downtown . rouch grouch grouch .



ACTUALLY , these things shifted line , if you shifted the throttle , till they stuck bigger surfaces aft , when they had any power . so If its a bit vintage and smaller than 20 % Tail , its in the ' narrow trim ' range .
and Loose Elevator'd HELP .  ;D

Offline M Spencer

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Re: Twin Prop Direction
« Reply #21 on: April 28, 2025, 08:07:23 PM »
Bugger .

Quote
Twin-engine aircraft have unique handling characteristics due to factors like engine torque, asymmetric thrust, and the potential for engine failure. These differences can lead to significant yaw and roll tendencies, especially during takeoff and single-engine operations. Understanding these characteristics is crucial for safe and effective flight.

Meant to Say . full size P 38 . One Engine OUT . Will fall out off the sky , full throttle - on the other .

correct proceedure On One engine - Is to PULL THROTTLE BACK - Trim Straight - then - Bring Up remaining engine As Far as it will STAY STRAIGHT . seems not to bother mine.  ;D thoo its not exactly overpowered .  :

(
Quote
As a result of the propellers turning clockwise on a conventional twin, there is a left rolling tendency of the airplane. If the right engine fails, this left roll tendency will help us maintain control and resist the roll towards the right, inoperative engine, caused by asymmetric thrust.

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