Twister - FINISHED, DONE, READY TO FLY!!!

[Rusty]

Hello,  Please find attached questions regarding the pushrod that goes between the flap horn and bell crank.

I am scratch building a Twister and want to make the controls as best I can.   I really don't know that much about it and have just been using what they gave in the kit.

Thank you.

[Steve Berry]

Simple answers: A, B, B

Steve

Sent from my SM-N986U using Tapatalk

[Rusty]

Simple answers: A, B, B

Steve

Sent from my SM-N986U using Tapatalk

Thank you for the reply.    My concern is that in Q1, A  the angle of the pushrod will apply sideways pressure on the bell crank instead of lateral.   I was thinking the pressure should be straight in line with the bell crank movement. 

[Ken Culbertson]

What Steve said A,B,B.  If you are scratch building, I hope you are using metal profile horns instead of flap mounted but if you aren't, make sure the wire connecting the flaps is stiff.  Same with the elevator.  Also see if you can mount the bellcrank so that the pushrod is parallel to the fuselage exiting the inboard wing from the bellcrank arm to the flap horn with the bellcrank centered.  This probably means mounting it "backwards" which is common.

Good luck, I love Twisters - Ken

[Brett Buck]

Thank you for the reply.    My concern is that in Q1, A  the angle of the pushrod will apply sideways pressure on the bell crank instead of lateral.   I was thinking the pressure should be straight in line with the bell crank movement.

   Well, perhaps ideally, but putting a bend in the pushrod doesn't change that. It's not like the bent pushrod will push straight back and then turn a corner. The force will still be in a straight line from one end to the other. Putting in the bend  does give a way for the pushrod to flex. You want the pushrods to be straight.

    If you want to keep the forces in the bellcrank plane, you would have to tilt the entire bellcrank. That is OK, but it does complicate the issue of clearance for the crank and leadouts.

    I also note that using a ball link on the bellcrank end will cause a torque trying to tilt the bellcrank, since the force is being applied above the plane of the pivot. The ball is about 1/4" out of plane, the force  times the 1/4" is the torque. I think you *should* use it, but you need to make the pivot resistant to this torque tipping the bellcrank up and down. This has caused severe hunting on other airplanes using traditional pivots, which were OK when new but hunted wildly when it got some wear on it.

     As luck would have it, I literally just built the bellcrank and mount for a new Skyray, and can show how I do it. The bellcrank is a 3" version of my usual forked-end sandwich bellcrank. The pivot rod is a nominally 3/16" diameter titanium rod. This one was one of the orthopedic repair rods Jim Rhodes gave me, the actual diameter is about .185. The bearing is 1/4" OD 3/16" ID telescopng K&S tubing about 1 1/16" long. It spins very freely but has very small amount of rocking motion, maybe .010 at the ends of the bellcrank. The mount  uses 1/8" aircraft ply (with a bunch of lightening holes) just glued to the back of the 1/4" x 5/16" medium balsa spars. This is adequate for the light pull tests I need (18-20 lbs). I use a similar method on the big airplanes, but the mount is 1/4" ply glued to the lite ply landing gear spar.

   This will allow free movement while still keeping the bellcrank level under the torque applied by the ball link projecting above the top surface.

     Brett

[M Spencer]

Overkill , but seeing you asked .



Found Maybe 5/32 flap horns are a bit stiff , unless really Zero discrepancey under loads the go . But as things want a bit off give , it depends .

One TRIMS the cross toobs , to abouta quater . But a Foot when fitting , sees theyre true , square , perpendiculat & suchlike . as thecasemaybee .

One tends to ' neutralise ' Wire Ends etc , for No Slack Freedom . ( freeist movement ) if its all stuck up tight in the topoffthewing , when its got Diheadral .

https://stunthanger.com/smf/open-forum/francherized-twister-article/msg484827/#msg484827  Chance Ted may know a thing or two about it .

Vindy used liddle short orns , as wier weighs a bit , unless its not there . This is onee of the ' Fine Tune ' / ' Fettle ' areas . Where you GET IT RIGHT , before nailing it . ( Final assy )

Generally - a STRAIGHT RUN to the Flap Pushrod . as in , If it were 1/8 wire . One bend each end . THATS IT .Three longitudes . You Can Leave THE ENDS at three inches - Till alignments Perfected .
Then cut grovve adjacent washer to bind & solder . And cut 1/32 + outside that . Bellcrank mount & Controls is where its false economy to skimp . just threw out a plane with a inaccessable ' Z ' ed flap  pushrod ,
rather'n put up with divergance. Flaps are the LIFT & tail is the PITCH . Mate .

[M Spencer]

Some Other Bits , you can dither about for days . ( Pass / Come Back ) with it up inthetop there . To Get NO BINDING .





Solder'n The Washer , Foist One . ( Itll settle down a touch , Often bevel inner edge off washer , to get it flat against lengthwise wire . Groove , even , to get it in more still against it . Thats just a Jig .


Getting further away , out at the end , there .

seeing we're here .The 1/8 holes get 1/8 brass tube . Later Cut to 1/4 or something . dual Adjustabble .


And youve gotta BOIL , in baking soda - Neutralise Acid . Oil. Wash in thinner . Petrol . Boil in oil . Chain Lube . MOREYS . Hot . Wipe with a rag & thinner . Then SPRAY WITH CLEAR . or something .

No Binding . No Corrosion .  And no scraps of 1/8 x 1/4 x 1/2 left after gear Leg repair to get caught in the bellcrank slot and just ' tip ' on each pass . BINDING . Needing a ' bump ' at the handle. to get past . AT ALL .

[Rusty]

Ken, I have a piece of 3/32" music wire connecting the flaps together.  I have the bell crank mounted where the plans call for and it centered in the lead out openings. 

Brett,  I understand what you are saying about the direction of force.   That lead me to ask another question.  I did some research and read the thread where you made your laminated bell crank.  That convinced me you are a REAL engineer.  I know other engineers in modeling that would / could never do that.

Thank you to everyone.  I am learning and improving.  Sadly, my only control line flying buddy, Jim has been diagnosed with lung cancer.  A few years ago I met him at one of my swap meets and he got me back into building and flying CL.

[M Spencer]

For sooth . another tricky one up in the top there . youve a bit more freedom with it thrown in the middle . ACTUALLY . A wire Post solder ( tight fit ) in the bellcrank . With a few washers & things . And Brass Tube at
the spars , to secure it . is pretty secure & free moving . IF you leave a little vertical end flat . Like a m.m. . So It dont all tighten up as the day warms . 


Yours'd be at an angle , outa da crank arm , but maybe yer angle the crank arm angled midway to movement arc - at flap horn . One Small ' kink ' toward an ends not so bad . A BEND midway or a Z , and Yr DOOMED .



AAAAHHHHEEEIIIEEEEE , Geting that to Work & Not Bind / or conflict the spacve time therom ( Two things cant be in the same place at the same time ) as they confict . hit . Jam . Bind . or deflect ! . 



So , ya dunno how easy ya gottit . But if you do the Fred Flintstone 2 .m.m. steel ( .077 1 ) or 3/32 or 2.5 or . . .  A 1/8 WIRE Pushn Rod , leave the ends out at three inch or so , for sighting aligning , and ease .
Till its all mid range aligned with NO binding , sticking , OR SLACK . You can leave the slack for theelevator . no worries . 5 m.m. / 3/16 th at the elevator edge , can be Good for grooveyness and stability . on a aft
C. G.

Hung from leadouts ,a hand on it . no Flap T E  DEFLECTION . 3/16 at elev. T. E. o.k. . When it falls off the hook with you pushing down , get your bare foot under it real quick , so it dosnt damadge it . the Plane .
never mind about the foot .
Which brings us to solder blobs & Irons & bare feet .
and FUMES . Acid Solder , Sanding Bare . Pre tinning .

DONT SOLDER NEAR LINE STORAGE . Pref in your blacksmith area , Downwindest , So the CORROSIVE FUMES are absent from the work area .
if you store your lines ABOVE your soldering bench , Thats the end Of Em . And anything else ferrous etc up there . BE WARNED .

[Rusty]

Mate, I am using .092 wire to connect the flaps to the bell crank.  Is a bullroarer louder than a model plane?

[M Spencer]

With your 3/32 Flap horn , if the arms are at the inner flap faces , or say 1 1/2 apart , itll be pretty stiff . IF it were six inches , theyed be like Beringers ' Torsion Arms ' and need to be considered .

We'd decided to go to Blah Guage wire , in Oiklund , 2.7 m.m. , for Horns . On .35 ships . as it can get a bit bumpy their , in the air . In fact youd design for 40 m.p.h. winds , to fly some seasons .

the ' absorbancey ' of things , to shock loads , in rough air , you can visualise , if you try'n consider WHAT forces are absorbed - transfered - transmitted , by the ' working surfaces ' HERE .



Tho our widdle fings may be a widdlebit smaller , the Same Principles are still involved . Support - Manouverability - stability - . And you dont wanna get in the way , of either of them .

SO , Considering Operating Conditions . You Dont have to make it to stand 40 knots , if your not gunna fly in it . IF its just for Mild air , you only need half the durability . as it were .

So you can get a Francher Twister REAL LIGHT . So hook up to the article and study THAT . Deviations sholdnt  e required . We threw in that stuff , to show you's a bit of BLACK SMITHING in miniture .
For the more isolated , do it yerself , types . Out there . 

[M Spencer]

Mate, I am using .092 wire to connect the flaps to the bell crank.  Is a bullroarer louder than a model plane?

No , but it carries a lot further . Mountain top to mountain top . Further Sometimes .

I thing teds got a carbon Rod in there , with wire ends . Without looking . If you asked me , Id bind a light carbon tube to it , to stiffen it . As it weighs naff all .
Some use something like 1/4 x 1/2 BASS , pushrods  . as the Expansion Rate Vs Barometer matches the Timber Aeroplane .
If we flew at Mach 2 , itd grow six inches , like the Concorde .  But the tiber Pushrod does with the need to have it adjustable , as it stays in tune .

Those ' SAILING ' boats , Tuning was what it was all about . TRIMMING is the P. A. Term . But having no / less  variable factors , gets it all hunkey dory - straight off the bench . sometimes .
Others never come right . Relieved I wouldnt have to persevere with the last concoction . As it was contrived rather than DESIGNED . So taght a lot about FLAWS . But there is a limit .
Like Learning all the differant ways to CRASH .

Not productive entirely .  Flap to Bellcrank is the A1 Top Factor control system requirement . After seeing it all stays where its put . In the Air Too. 

Guess how many TONNES loadings in the mast & hull , and inbetween. T

RE . But theres no whitecaps . Flying coastal - there usually was - in the sailing / flying season . Year round , half of its gales .
When the winds getting good for KITES , its getting a bit much for STUNT . or is it just more challengeing . You need something for 20 / 25 knot winds , in N.Z. or youll miss weeks / months of flying .
Something for 40 , like the Folkerts , will see you right , year round .

Go Way less overengineered , for fair weather flying . But STILL . the Flap Pushrod is the No ONE Control Component - as far as operating forces - so nothin pansey their .

iMIT cONSTRUCTION oITICLE : https://www.scribd.com/document/24098001/Imitation-Article

[Brett Buck]

Brett,  I understand what you are saying about the direction of force.   That lead me to ask another question.  I did some research and read the thread where you made your laminated bell crank.  That convinced me you are a REAL engineer.  I know other engineers in modeling that would / could never do that.

   Oh, I think anyone *could*, it's very simple to build and it doesn't take too long. If you build one yourself, be sure to use a quality aluminum for the facing - these are .032" 6061-T6, but I think any normal engineered and heat-treated alloy would work. I also have one made of .020 titanium, that was a fun afternoon cutting that out. Not random hardware store aluminum strip flashing or of unknown grade, which has brought others to grief in the past. .032 is *great overkill* for a Skyray 35, of course.

     Same with the pivot, greatly excessive but it was what I had. I do note that if the pivot wire bends under load, the bellcrank will potentially bind up. For the big airplanes, this is about 10 lbs load and it's suspended with about a 2" spacing. It's 3/16 to reduce the flexing, and it's titanium because 2.5" of 3/16 music wire is *heavy*.

    Brett

[Perry Rose]

Brodak sells "Z" bend rods that are perfect for the bellcrank end and Du-Bro has solder on threaded couplers and clevis's for the flap end. Quick, simple, friction free, inexpensive and bullet proof. Don't forget it's only a model airplane.

[Brett Buck]

Brodak sells "Z" bend rods that are perfect for the bellcrank end and Du-Bro has solder on threaded couplers and clevis's for the flap end. Quick, simple, friction free, inexpensive and bullet proof. Don't forget it's only a model airplane.

    The DuBro clevises are not remotely durable enough for stunt plane use and are absolutely infamous for failing at inopportune times. No commercially-available clevis, even the "heavy duty" 1/4-scale RC types, will stand up for very long. Soft solder joints are also not durable enough. If you could braze them (i.e. silver braze with a torch), that would be good enough, but that will usually destroy the clevis as it tends to unbend itself, and getting it red hot softens it even more.

   This is a DuBro 2/56 Kwik-link that I was using on my rudder connection - it's only ground adjustable, does not intentionally move at all in flight, running on a plywood horn, and drenched in oil. This is after only a few years and maybe 200ish flights. I replaced it - and the new one is wearing out, too, at a high rate. This is a best-case situation, if if it fails, the airplane is unlikely to crash, and there are practically zero static loads.



    I am not sure why a stunt plane is so much more demanding than, say, a 1/4 scale RC model with a Quadra, but history has spoken.

     Ball links are particularly important on the bellcrank-to-flap connection, because of the compound angles they have to move through, all three dimensions. Bend wire (z-bends, etc) require some clearance/slop to allow the required movement in all the dimensions. That's not entirely fatal - we did it for years - but ball links and carbon or fiberglass pushrods are also a lot easier. Screen the ball links for getting tight, pick the loose ones.

     Brett

[Ken Culbertson]

Please use CF Pushrods and Ball Links.  Every place there is metal on metal will start to wear out on the first flight, mostly from vibration.  Even on Electric.  For space reasons I used the DuBro safety clevis, the Black one with a retaining clip, on the flaps for Endgame III.  Even brass bushed they started having slop in as little as 50 flights. I redesigned the controls for Endgame IV to use all ball links.  My other control pet peeve is the bellcrank post.  If you compete you are going to have a pull test that is 4-5 times anything you will have in flight short of a runaway hitting the lines at full speed.  Unless reinforced the typical thin bellcrank on an 1/8" steel (even piano wire) post held centered by two wheel collars between the top and bottom of a 2" wing is going to bend.  Replacing a floating bellcrank in a finished plane is only slightly less torture than waterboarding.

The picture is a bit dark but you can see the components.  This is the center section of Endgame IV but it is identical to what I had in my Twister except I used a 4" bellcrank to keep the movement the same as my other planes and wider to accommodate a tricycle landing gear mount.  What is important is that the center post remains removable. The 1/8" ID brass tube is sandwiched between two .3mm doublers with a hard 5/32 balsa (grain spanwise) center.  The lack of any gap makes it nearly impossible to bend the pivot rod.

If you wonder why so much fuss over the controls it is because they are the most overlooked part of the plane for new fliers and the most important.

Ken

[Dan McEntee]

    The DuBro clevises are not remotely durable enough for stunt plane use and are absolutely infamous for failing at inopportune times. No commercially-available clevis, even the "heavy duty" 1/4-scale RC types, will stand up for very long. Soft solder joints are also not durable enough. If you could braze them (i.e. silver braze with a torch), that would be good enough, but that will usually destroy the clevis as it tends to unbend itself, and getting it red hot softens it even more.

   This is a DuBro 2/56 Kwik-link that I was using on my rudder connection - it's only ground adjustable, does not intentionally move at all in flight, running on a plywood horn, and drenched in oil. This is after only a few years and maybe 200ish flights. I replaced it - and the new one is wearing out, too, at a high rate. This is a best-case situation, if if it fails, the airplane is unlikely to crash, and there are practically zero static loads.

    I am not sure why a stunt plane is so much more demanding than, say, a 1/4 scale RC model with a Quadra, but history has spoken.

     Ball links are particularly important on the bellcrank-to-flap connection, because of the compound angles they have to move through, all three dimensions. Bend wire (z-bends, etc) require some clearance/slop to allow the required movement in all the dimensions. That's not entirely fatal - we did it for years - but ball links and carbon or fiberglass pushrods are also a lot easier. Screen the ball links for getting tight, pick the loose ones.

     Brett

    Another thing that we lost when Tower/Great Planes Hobbies went away is their hardware. I think they had the best hardware as far a selection and quality went. If I was going to use a clevis on anything, I always used their 4-40 threaded clevises after seeing customers brink back examples of DuBro clevises breaking from vibration. I never had a problem with Great Planes clevises. They were made from heavier steel and Nickle plated also, so if you needed to solder anything to one it was very easy.  I think their screws and fasteners were better also. When I go to swap meets now, that's one thing I look through junk boxes for. I didn't get too far into the use of. ball links to remember if they produced those or not. The Great Planes aluminum spinners were pretty good also and reasonably priced.  I for sure do miss their products.
  Type at you later,
   Dan McEntee

[Rusty]

Brett and Ken,  I went through my helicopter stuff and found some tail rotor carbon pushrods.  I have everything to put carbon pushrods and ball kinks everywhere.   The 3/32 music wire connecting the flaps has a brass tubing in the middle epoxies to the trailing edge.  The plans for the Fancheruzed twister has 3/32.

I am using light weight 1/4 for the flaps.

Thanks again.   Please pray for Jim.

[Ken Culbertson]

Brett and Ken,  I went through my helicopter stuff and found some tail rotor carbon pushrods.  I have everything to put carbon pushrods and ball kinks everywhere.   The 3/32 music wire connecting the flaps has a brass tubing in the middle epoxies to the trailing edge.  The plans for the Fancheruzed twister has 3/32.

I am using light weight 1/4 for the flaps.

Thanks again.   Please pray for Jim.

I forgot what my Twister came with.  I know I used a 3/32 profile horn from Tom Moris.  That is strong enough because it is being driven by a horn brazed near the center of the wire.  It may be just me but if you can't find one of those and the horn will be bolted to the INBOARD flap, I would use 1/8".  The reason is with a thinner wire the inboard flap will have more force than the outboard and cause a slight roll in turns.

Ken

[M Spencer]

The Friction / Bindings ' a thing ' .



This sucker , with just a tiny bit of binding , in the flap horn , wouldnt exit straight & felt rubber . The controls were smooth & free  . just wanted a push to move them .
Thought ' the controls should fall under their own weight ' was a bit over the top . ( if you had any line tension ) Aerodynamic & mass ' balance / counterweights ' can
steady  it all up , incidently . In bumpy air . Supermarine anylisis states ANY Control Friction destabilises the Aircraft . Most discernable at Aft C. G. Limit .

term is ' divergent ' . Convergent is positive stabilty . Self straightening .

mechanically ' Soft ' controls , dont help none at all . Whereas I go on about them working like a ( Antique ? ) rifle bolt .Positive direct friction free exact no deflection ( Within reason ) ACTION .

The Magum with the Z in the 3/32 pushrod , I left at the Op shop . It'd NEVER go exactly where you put it . Similar ' flaw ' but ten times worst . A limit to wasteing your time .

Have A READ of Teds diatribe , as it was cutting edge stuff . and still is . I cant see he got it wrong , So WHY CHANGE IT . Exact & itll be a Pleasure to Fly . NO SHORT CUTS  .

[Steve Helmick]

Ken wrote: "The 1/8" ID brass tube is sandwiched between two .3mm doublers with a hard 5/32 balsa (grain spanwise) center.  The lack of any gap makes it nearly impossible to bend the pivot rod."

I like Ken's bellcrank mounting as shown in the picture, but the ".3mm" made me wonder if the decimal point is a typo, as well as what the ".3mm doublers" are made from. By my calculation, .3mm is just under .012", while 3mm is just under 1/8". I'd bet it's 1/8" plywood of some sort, and IMO, "Lite Ply" would probably do just fine, but I also don't believe I've ever used "Lite Ply" for anything. There are many things I would NOT use it for. Steve 

[Brett Buck]

 3/32 flap joiner is perfectly OK for  Twister, the control forces should be very light, even if it is a little asymmetrical due to being off-center. I use a 1/8 flap horn and 3/32 elevator horn, even on regular-sized models.

     Brett

[Rusty]

Okay Guys,  I made some progress.  I installed a carbon pushrod,  ball links and quarter scale control arm.  I measured the plan control arm to determine which hole to put ball link.

[Rusty]

Pic

[Ken Culbertson]

Ken wrote: "The 1/8" ID brass tube is sandwiched between two .3mm doublers with a hard 5/32 balsa (grain spanwise) center.  The lack of any gap makes it nearly impossible to bend the pivot rod."

I like Ken's bellcrank mounting as shown in the picture, but the ".3mm" made me wonder if the decimal point is a typo, as well as what the ".3mm doublers" are made from. By my calculation, .3mm is just under .012", while 3mm is just under 1/8". I'd bet it's 1/8" plywood of some sort, and IMO, "Lite Ply" would probably do just fine, but I also don't believe I've ever used "Lite Ply" for anything. There are many things I would NOT use it for. Steve 

Carbon Fiber plate.  I use .5mm where 1/8" plywood would normally go and .3 where 1/16" went. This but stiff and strong.  Plate is different from matt and cloth.

Ken

[Brett Buck]

Pic

   That's pretty heavy-duty alright!  I am curious, why the doublers at the roots of the flaps so not go all the way to the arms on the flap joiner I use similar doublers to reinforce the hardwood inserts where the horns go in.

   Also, it's perfectly good in this case, but in the future I would suggest shortening the cross-bar on the flap horn to be as short as possible, an inch and a half of music wire is stiffer than three inches.

     Brett

[Ken Culbertson]

Pic

I hope you haven't closed it up yet.  The pushrod is good.  Make sure you have 6 turns of the screws on each end and the screw will go in 8.  This is to center it and give you two turns either direction without letting either end get below 4 which is my comfort zone.  I have flown as low as 2 but it is not safe.  The other thing, and I hope I am not alone on this one.  NEVER solder leadouts or lines anywhere.  It is not a matter of "if" they will break but "when".  Wrap them just like you do lines.  I lost two planes to this in my early days when the metal VECO bellcrank was the standard.  If you are doing much maneuvering of have a big motor and it pulls alot the leadouts can saw through the bellcrank is as little as 100 flights.  I have seen less.  And if that doesn't happen the bellcrank might saw through the leadouts.  If it is not too late get a nylon one and run the wire through some thin tubing.

Ken

ps - if you have already epoxied the pushrod ends in don't forget to wrap about an inch of the rod with kevlar thread.  Heavy duty sewing thread will work but it is not as sexy.  This is not to meke it stronger, it is to keep the rod from splitting.

[Rusty]

Ken, the ball links have plenty of threads.   The holes on the bellcrank have been chamfered. The is no sharp edge to cut the leadouts.  What fo you recommend to keep the wire wrapping from unraveling, epoxy, shrink wrap?

[Jim Svitko]

I have to agree with Ken regarding the leadouts rubbing on that metal bellcrank.  Chamfering the holes might buy you some time, but it will not prevent a disaster.  Even with grease, the leadout strands will start to fray.  Also, as he said, never solder.  Wrap just like you would do for the lines.

It might be more work, but the slotted end bellcrank, with the leadouts around a teardrop fitting, solves many problems. 

[Ken Culbertson]

This thread covers most of what we are talking about.  Even has an example of the Teardrop Jim mentioned.

https://stunthanger.com/smf/building-techniques/bellcranks-leadouts-and-sleeves/

There must be a hundred posts on this issue.  Try searching "leadout","bellcrank","tubing".

Ken

[Dave Lajb]

What Steve said A,B,B.  If you are scratch building, I hope you are using metal profile horns instead of flap mounted but if you aren't, make sure the wire connecting the flaps is stiff.  Same with the elevator.  Also see if you can mount the bellcrank so that the pushrod is parallel to the fuselage exiting the inboard wing from the bellcrank arm to the flap horn with the bellcrank centered.  This probably means mounting it "backwards" which is common.

Good luck, I love Twisters - Ken

I am in the process of doing a scratch build twister as well and honestly this was driving me nuts.  The plans show on the wing build with the pushrod exiting the outboard wing.  Yet the fuse profile shows it exiting the inboard side with the horn on the inboard side.  Now that makes more sense.  But now I have to ask, why the inboard side vis outboard?

[Dave_Trible]

I am in the process of doing a scratch build twister as well and honestly this was driving me nuts.  The plans show on the wing build with the pushrod exiting the outboard wing.  Yet the fuse profile shows it exiting the inboard side with the horn on the inboard side.  Now that makes more sense.  But now I have to ask, why the inboard side vis outboard?

In my experience it really doesn't make any difference.   The last few profiles I built I put the controls on the outside.   I guess to have all the external 'junk' on one side for cosmetic reasons.    It may make a difference if you put your bell crank in reversed- front line is 'up' or normal rear line 'up'.    It might make sense to put the pushrod down the side that keeps it better in line with the control horn.   On mine I used the front line for up but just mounted the bell crank further toward the outboard side enough to have the pushrod exit on the outboard panel.    One very minor thought- the controls on the outboard side with an outboard-mounted slimer engine might keep the controls lubricated,   maybe not so much if a muffler hangs pretty low.   Actually putting any lube on controls isn't too wise.   Any grit that sticks and accumulates will make a grinding slurry that may actually chew the controls up faster.   Better to leave them dry.   BEST to use Delrin parts wherever possible and never worry about wear again.

Dave

[Ken Culbertson]

I am in the process of doing a scratch build twister as well and honestly this was driving me nuts.  The plans show on the wing build with the pushrod exiting the outboard wing.  Yet the fuse profile shows it exiting the inboard side with the horn on the inboard side.  Now that makes more sense.  But now I have to ask, why the inboard side vis outboard?

It has a lot to do with the size and composition of your flap horn, geometry and your preference in which leadout is in front.  Most are used to and as a result prefer the down line in front.  If you use an adjustable leadout guide and keep them close together at the tip you would probably not notice the difference.  The geometry part means that arguably, the pushrod should be as close to parallel to the fuselage as possible at neutral.  Now to your question, the force exerted on the flaps when deflected in a corner at full speed is a lot more than we think.  If the inboard flap has the flap horn mounted on it the entire force of the bellcrank is place on the inboard bend of the horn which allows the inboard flap to move more in a high stress turn which creates an outboard roll.  The reverse is true if the horn is mounted on the outboard.  To overcome this you can use a "profile horn" with the brazed horn off center, shorter horns that have the arms closer to the fuselage or thicker wire.  3/32" and 1/8" are the popular sizes.  Personally, I switched to the offset metal horns long before they were difficult to find.  3/32 is fine for this type of horn but IMHO not for the flap mounted bolt on type horn.  Some wire is more prone to twisting than others.  If you want to see if your horn is stiff enough put one end in a vise and see how much force it takes to move the other.  A "tricks" you can use for smaller wire is put the horn over the wire in whichever flap it goes on with the bolts on either side with just enough clearance to bolt on the ball links and bend the other side to be as close to the fuselage as possible.  Use tubing or hardwood blocks for the wire.  Never wire on balsa.  Ok, there is the overkill explanation.  Some may, and probably will disagree with some of this but it all comes from 65 years of learning from doing it wrong the first time.

Ken

[Brett Buck]

I am in the process of doing a scratch build twister as well and honestly this was driving me nuts.  The plans show on the wing build with the pushrod exiting the outboard wing.  Yet the fuse profile shows it exiting the inboard side with the horn on the inboard side.  Now that makes more sense.  But now I have to ask, why the inboard side vis outboard?

   I would put them in the outboard wing on a flapped airplane like a Twister. The reason is illustrated above- if you drive the flap with the horn on the outside, any flex in the flap joiner will give you more outboard deflection than inboard deflection, which might cut down on the amount of tab you need on the outboard flap. It's a minor effect (like a lot of thing we worry about) and you can certainly do it the other way way around, but that would be my preference.

    Brett

[Ken Culbertson]

   I would put them in the outboard wing on a flapped airplane like a Twister. The reason is illustrated above- if you drive the flap with the horn on the outside, any flex in the flap joiner will give you more outboard deflection than inboard deflection, which might cut down on the amount of tab you need on the outboard flap. It's a minor effect (like a lot of thing we worry about) and you can certainly do it the other way way around, but that would be my preference.

    Brett

I was about to comment on the difference in what you would do as an expert vs someone learning.  You have done it for me.  As an expert I would want what you said as a "beginner in stunt " I would want the roll to be outboard if any.

Ken

[Dave_Trible]

If possible I'd use 1/8" horns.   I braze mine but getting the wire that hot also softens the steel making then even more prone to flex.   I few years ago I thought it might be prudent to stay with the 1/8" on the flaps but make 3/32" wire to save a dab of weight on the stab/elevator.   Admittedly this was one of my bigger airplanes.  The result was an airplane that was very hard to fly.   It felt like I had rubber bands in the control system.  That 3/32" wire flex made it impossible .  I bit the bullet and tore the horn out.  I put in a 1/8" wire horn and finally had a pretty nice flying airplane.  The experience has me now using 1/8" wire for everything with a .35 or larger engine.  Long ago I also bought some 'tweakable' horns from somebody.  Had the same experience but worse,   They would take their own tweak about every flight and change trim every time.  Just really too soft.   The 1/8" horns are nearly impossible to tweak without breaking the flaps but I just don't try.   I'd rather use other means and have very solid horns.

Dave

[Brett Buck]

And, just to clarify, the construction AS SHOWN - 3/32 joiner, pushrods, etc -  is perfectly adequate for a light-weight, light duty system like a Twister. The only thing I would consider changing on the current airplane might be to bush the leadouts to the bellcrank somehow.  It doesn't need to be retrofitted with 1/8" flap joiner, a shorter joiner, forked-end bellcranks with titanium pivots, or any of the other things that might be good practice or necessary for a larger 40-60 piped or electric stunt plane expected to go 1000 flights with no maintenance.

      I am sure that Ken and Dave would agree that showing *good practice* is one thing, going back and cutting up or disassembling a workable system that is 85% complete to try to make it "better" from a durability standpoint is quite another. Stunt fliers are extremely prone to "paralysis by analysis" and that is something that you have to fight to avoid bogging down relatively simple projects with it.

      Brett

   

[Ken Culbertson]

And, just to clarify, the construction AS SHOWN - 3/32 joiner, pushrods, etc -  is perfectly adequate for a light-weight, light duty system like a Twister. The only thing I would consider changing on the current airplane might be to bush the leadouts to the bellcrank somehow.  It doesn't need to be retrofitted with 1/8" flap joiner, a shorter joiner, forked-end bellcranks with titanium pivots, or any of the other things that might be good practice or necessary for a larger 40-60 piped or electric stunt plane expected to go 1000 flights with no maintenance.

      I am sure that Ken and Dave would agree that showing *good practice* is one thing, going back and cutting up or disassembling a workable system that is 85% complete to try to make it "better" from a durability standpoint is quite another. Stunt fliers are extremely prone to "paralysis by analysis" and that is something that you have to fight to avoid bogging down relatively simple projects with it.

      Brett

   

I quite agree.  Where we might disagree is that pointing out something that is wrong or could be better, even if it is not changed now, can and should influence how you do it on the next plane.   Unless learning the pattern without in person expert guidance at the field has become significantly easier recently the plane we are talking about here will have been rebuilt several times well before any of the things we covered happen to the controls which is what I suspect you were implying. 

Ken

[Dave_Trible]

Yes I agree with both of you.   It happens here very often that things are 'over thunk' and made too much of.    I wouldn't be tearing anything up at this point to change it.   It's more about things you might think about in the future AND there are quite a few others who take their que's from what they see and learn herein.   Thats where I hope to be coming from with my comments. Carry on.....

Dave

[Brett Buck]

     I would note that my *original* Skyray was built in about 1991 or so, and it has completely unbushed stranded leadouts straight out of the kit, running in the kit SIG nylon bellcrank, and the kit 3/32 music wire pushrod also running an unbushed hole, with a soldered washer retaining it on either end. it is adjustable only by putting a "z" bend in the pushrod and tweaking it with a big paur if pliers, and only adjustable at the elevator by unsoldering the washer and moving it to another hole

     It is still perfectly functional after what is now *34 years*, and in fact the airplane won Advanced at the Golden State meet about 6 months ago. There were a few nearly-complete rebuilds of the wing and the fuse,  but not to the control system. The loads are absurdly light compared to what we have to do to keep full-size airplane controls together.

    Note that I had built the airplane with the notion that it was going to last about 1/2 hour, for my work buddies to fly at a work picnic (with predictable results). That didn't happen, Zach Schultz recently used it to go from "not able to fly inverted" to winning Advanced at one of the more competitive local contests in the country in about a year and a half.

      Brett

[Rusty]

Hello Guys,  I am making changes, that I can, to do what you recommend.  Ken recommended I epoxy thread or wire to secure the pushrod tube to the insert.  I did that by mixing up some epoxy, putting the pushrod in my drill, putting epoxy on the pushrod where the thread goes and then hand wrapping a few times and then used the drill the wrap the rest.  It took, literally, minutes to do it.  I then put some epoxy over the thread and smoothed it out.  I'm not going to redo the leadouts where they connect to the bellcrank.  All my planes from day one were made this way and none failed.  The reason they don't fail is because I don't use them enough to fail.  I believe, 100%, if I flew all the time it would.  I don't even have anyone to fly with now.  I, almost, abandoned the Twister, but didn't.   I finished my Vector over a month ago and can't try it out.   <poor me>

[John Skukalek]

Why can’t you try out the Vector Rusty?

[Dave_Trible]

Hello Guys,  I am making changes, that I can, to do what you recommend.  Ken recommended I epoxy thread or wire to secure the pushrod tube to the insert.  I did that by mixing up some epoxy, putting the pushrod in my drill, putting epoxy on the pushrod where the thread goes and then hand wrapping a few times and then used the drill the wrap the rest.  It took, literally, minutes to do it.  I then put some epoxy over the thread and smoothed it out.  I'm not going to redo the leadouts where they connect to the bellcrank.  All my planes from day one were made this way and none failed.  The reason they don't fail is because I don't use them enough to fail.  I believe, 100%, if I flew all the time it would.  I don't even have anyone to fly with now.  I, almost, abandoned the Twister, but didn't.   I finished my Vector over a month ago and can't try it out.   <poor me>

Rusty I fly about 85% of the time by myself.   Just make a decent stooge and go fly.   Just be extra careful to stay out of the prop when you are by yourself.  Go slow and think about where you and your hands are!

Dave

[Ken Culbertson]

Twisters love to fly solo.  I kept mine at my office where I could sneak in a few.  Electric makes it easy - and clean!

Ken

[Rusty]

Why can’t you try out the Vector Rusty?

I don't have anybody to help, like hold it when I start it and launch it, etc.  I'm sorry I brought this up.  I know it is whining.  I know I could make some kind of stooge, but flying to me is not a solitary activity.  To me it is comradery. 

Thanks for asking. 

[Paul Smith]

2.4 RC is best.  No pull cord to mess with. No spikes required

A $34 radio, four D-cells, any old servo.  2x4's for weight. .
The radio effectively cost NOTHING, since I needed it for scale & carrier.  The release is hooked up to the pushbutton channel 3.

It's great to have flying buddies, but it's handy to be able to get in a quick test flight without having to round somebody up.

[Rusty]

2.4 RC is best.  No pull cord to mess with. No spikes required

A $34 radio, four D-cells, any old servo.  2x4's for weight. .
The radio effectively cost NOTHING, since I needed it for scale & carrier.  The release is hooked up to the pushbutton channel 3.

It's great to have flying buddies, but it's handy to be able to get in a quick test flight without having to round somebody up.

Thank you.   What do you do when it lands opposite your launch area?  Do you roll up your lines, move the airplane back and roll them out again?

[Ken Culbertson]

The old screwdriver in the thong trick.  Stick a screwdriver in the ground or a crack in the concrete or whatever.  Hook your thong around it.  Go get the plane and walk it back to the stooge. 

Ken

[Dave_Trible]

I made a holder from an old wooden kitchen cutting board with a piece of wooden closet pole  (10-12") sticking straight up from it.   I keep it near circle center.   When I land I lay my handle on it then go pick up the plane and walk it around with the holder keeping the lines off he ground.   

Dave

[Dan McEntee]

    A friend and flying buddy here, Bob Arata, used a 5 or 10 pound weight lifting weigh, and had a wooden dowel or length of conduit with a big washer on the end that he would use for holding his handle while walking back with the airplane to his stooge. Then he could pull the dowel out and it would fit in his flight box and the weight would lay flat.. I have seen guys use a gallon milk jug filled with water to give it some weight and depending on your handle it can hook on the top of the jug, or you can put the thong on it.
  Type at you later,
   Dan McEntee