Control Free-play (slop)

[Warren Leadbeatter]

Now much control free-play is too much?   Today I noticed on my 4 year old Vector, with the belcrank held tight, my elevator can move up and down a bit more than about 1/8". or 4 mm. The flaps move a bit less, about 2.5 mm or 3/32".  The model is hunting and inconsistent in turns.  Would this be the reason?  How can I tighten it up or is it time to rebuild?  Any suggestions?

[Allan Perret]

Depends on what kind of access you have to the flap and elevator horns and the materials of those components. 
Good access >>>  You can drill out existing holes and install bushing.
Poor access  >>>  Maybe you can get a little spot of epoxy in the hole, and when its cured open it up just enough for a tighter fit than you had before.  Might not be a long term fix,  but if you dont have better access

[RandySmith]

Now much control free-play is too much?   Today I noticed on my 4 year old Vector, with the belcrank held tight, my elevator can move up and down a bit more than about 1/8". or 4 mm. The flaps move a bit less, about 2.5 mm or 3/32".  The model is hunting and inconsistent in turns.  Would this be the reason?  How can I tighten it up or is it time to rebuild?  Any suggestions?

Hi Warren

That is the most frequent reason for a plane to hunt, I have check many many planes  that hunt  and once the flap slop was fixed they worked better, without hunting,  you can have a little elevator slop but any slop in  the flap-bellcrank  will make the airplane hard to live with.
The reason why is the AOA changes without any input from the pilot , especially when you have wind and fly up and downwind, the flaps are free to move by themselves...a bad sitiation
Randy

[minnesotamodeler]

Actually a little elevator slop has cured many a "hunting" airplane. I don't know why, but it works. Wingflap slop I don't know about.
I had a good flying Rat Racer long ago that had nearly worn through the elevator horn.  We replaced it with a nice new close-fitting one and it hunted all over the sky...drilled out the new horn to oversize and it settled back down again.  Maybe some expert here could explain the aerodynamics of it, I can't.

[Warren Leadbeatter]

Hi Warren

That is the most frequent reason for a plane to hunt, I have check many many planes  that hunt  and once the flap slop was fixed they worked better, without hunting,  you can have a little elevator slop but any slop in  the flap-bellcrank  will make the airplane hard to live with.
The reason why is the AOA changes without any input from the pilot , especially when you have wind and fly up and downwind, the flaps are free to move by themselves...a bad sitiation
Randy

Hi Randy

I find it funny (odd) that there is not more talk about this on the forums. I just did open heart surgery on the Vector and I have replaced the bellcrank to flap control rod with a Tom Morris style ball link control rod and now I have zero slop in the flaps and about 1.5mm or 1/16" in the elevator.  It wasn't an easy task! Will give it a try as soon as I can.

Thanks

[Kim Doherty]

Now much control free-play is too much?   Today I noticed on my 4 year old Vector, with the belcrank held tight, my elevator can move up and down a bit more than about 1/8". or 4 mm. The flaps move a bit less, about 2.5 mm or 3/32".  The model is hunting and inconsistent in turns.  Would this be the reason?  How can I tighten it up or is it time to rebuild?  Any suggestions?

Warren,

I strongly agree with Randy. As a full size pilot, instructor and aerobatic pilot I can not conceive of a reason for having ANY slop in the control system. There are a lot of "Old wives tales" out there. This one should be avoided at all costs. What should be free is the ability of the controls to move of their own accord just due to their own weight. There should be no stiction WHATSOEVER!  This is IMHO one of the most prevalent problems of less than perfect models.

Kim

[peabody]

Noel Drindak is very wise....an engineer with a passion for control line planes and detail...plus he likes to blend a LOT of technology into his creations!
Noel wrote a piece in Snews a few years ago about "slop".......the long and short was/is that if the alignment is proper (perfect), there should be no need for slop. He feels that slop masks mis-alignment.....
The American winners of the Nationals for the past several years (over a decade?) use ball links in their control systems....
Ball links have no slop in them...

Have fun

[Andrew Tinsley]

   A very long time ago, before flaps were common on stunt planes, any airplane that hunted was given deliberate slack in the elevator. It always WORKED. No slack gave hunting and vice verse.
   It may well have been misalignment in the airplane that caused the hunting in the first place, who knows. But slop in the elevator cured it, guaranteed. It ISN'T an old wives tale, it worked and worked well. I leave others to explain the phenomena, but it is a fact. I have seen dozens of examples treated thus and NEVER a failure!

Andrew. 

[peabody]

Hi Andrew.....I'm sure that your 'solution" works for you....HOWEVER...I still hold that Noel (and others) are right....if the plane is built accurately, it won't "hunt".

[Larrys4227]

I've got a Brodak Cardinal (ARF) that had  slop in the flap horn hole. I bushed it, but the plane
still hunts all over the place. Getting discouraged with it ... anything I do doesnt make any
difference. I need to put it on the bench and check alignments ... maybe adjust the flap position.
Its a handful to fly ..... so it sits in the corner collecting dust. 

[Andrew Tinsley]

Hi Peabody,
   
  I am sure that you are right. Alignment of airframes was not a very high priority in the old days! If a plane hunts, then surely something is incorrect in its design / build. Putting on the thinking cap and trying to figure out what causes the hunting gave me a bit of a headache. Assuming that there was a non zero / zero  incidence on the wing / tailplane, I really couldn't figure out why this gave rise to hunting. I am sure that someone can enlighten me to the hunting mechanism! I have never had hunting on a flapped plane, so I really can't comment, but on a plane without flaps, then a little slop in the system did cure the hunting. My comments were made because one contributor to the thread said that it was an old wives tale. I can confirm emphatically that it is not!
  Having got that of my chest, I am NOT advocating that folk should have slop in their systems. I agree that something is wrong with the plane and it shouldn't hunt, one really should get to the root of the problem and not put up with a palliative cure!

Regards,

Andrew.

[john e. holliday]

From day one I was always told or read to build light and straight with solid controls.  I won't mention the combat plane that almost caused the pushrod to cause a failure at the stabilator horn.  If not for the Z bend the pushrod would have fell out.   

[dale gleason]

Life is full of surprises. I've built probably a hundred or so control line planes since 1955, six dedicated stunt ships in the last ten years. On the IMPcat "G", just about ready for primer, I tried to cover all the bases...I've included all the trimming mechanisms, but hopefully built it accurately enough that their use will be minimal.

I took the ship to a DMAA meeting recently to  "Show-n-Tell" and admitted that it looked a little like a pregnant whale, when to my surprize, Bill Lee (I believe it was) noted it cannot be a pregnant whale because it is a "male whale"! As Gomer says, "Surprise, surprise!".  I care not its gender, I just hope there are no more surprises and this plane flies itself.....dg  

Some particulars:  Down and right thrust, zero wing incidence, one degree up stab LE, "Hi-Zoot" Rush Stabilizer, piped PA75, Morris controls (a'la Jim Snelson), Bob Hunt lost foam wing (straight and true), 63 ozs target weight,  three weekends, and still counting, of ROliver's building& finishing school, testing his patience to the max.

The point?   I've learned more about trimming in the last month than all the years before, and this plane hasn't even flown yet. Trimming may not be a black art, but it is close. Another little item, I've never really flown a "good" stunt ship, say one of Paul's or Windy's or Ted's, but I flew Richard's recently and I think it is imperitive that one knows what we're trimming for, ie, just how does a good, well-trimmed plane handle? In a word, it's wonderful.

[Warren Leadbeatter]

Finally got to re-test the Vector after fixing the control slop.  For what it's worth, removing the slop from the Vector's controls solved the hunting problem.

Cheers

[john e. holliday]

Warren, glad to hear it is working like it should.

Dale G.  Great picture of your plane, but, aren't worried about a hernia hefting it that high?   Hope you have a good log book.

Me I am still learning how to adjust handles to tame planes down or to get them working better.

[Allan Perret]

"Hi-Zoot" Rush Stabilizer

What is a   <<  "Hi-Zoot" Rush Stabilizer  >>

[Howard Rush]

What is a   <<  "Hi-Zoot" Rush Stabilizer  >>

That's what I was wondering.

I wouldn't put incidence in the stabilizer unless there's a way to take it out easily if it doesn't work.

[Howard Rush]

What is a   <<  "Hi-Zoot" Rush Stabilizer  >>

My wife has been looking for something like that.  Is it a pharmaceutical?

[W.D. Roland]

OK Dale
Please post the Rush Hi Zoot stab details. Is it from the nemesisssssssss?


I have several airplanes with slack/slop in the controls and 2 with zero slack/slop
There is a big diffrence in flying slop vs no slop.
The biggest place that I notice this(now) is in the overhead 8s where the aiplanes with slop need anticipated hand/control movement when changing directions and the airplanes with no slop go exactly where pointed exactly when told to do so.
I would think this even more so for 4 leaf----one day I hope to find out.

David