• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

PA18 wing fuselage rigging

giangab

giangab

Registered User
Hello all,

I am progressing on my restoration project of a PA18/95.

I wish to ask:

1. what is the tolerance on wing to fuselage triangulation, i.e. The allowable length difference betweeen Left and Right distances measured from each wing tip (nav light bolt on main spar) and rear top of tail fin.

2. Is the vertical fin perfectly on the vertical simmetry plane ... or should it have a side "twist" to compensate for prop wash?

Thanks for helping.

Gian



Sent from my iPhone using SuperCub.Org mobile app
 
I have not measured the tips to fin. I jig the fuselage which verifies square and Trammell the wings for the same reason.

Vertical stabilizer should point 1 1/2" left of the middle of fuselage at windshield.
 
giangab said:
Hello all,

I am progressing on my restoration project of a PA18/95.

I wish to ask:

1. what is the tolerance on wing to fuselage triangulation, i.e. The allowable length difference betweeen Left and Right distances measured from each wing tip (nav light bolt on main spar) and rear top of tail fin.

2. Is the vertical fin perfectly on the vertical simmetry plane ... or should it have a side "twist" to compensate for prop wash?

Thanks for helping.

Gian



Sent from my iPhone using SuperCub.Org mobile app
Click to expand...

no hard limit...

I measure from rear strut attach fitting on wing to tailwheel bolt, when getting ready to rig a plane to know what i am dealing with...

have seen up to 5" different on flying planes, under 1" is normal... 0 would be optimal....

the more out of square they are the worse they will perform at both ends of the envelope.
 
Thanks a lot Steve and Mike.

One inch difference at rear strut is some couple of inches at wing tip. I am well within that limit.

Obout the vertical stabilizer it is noted. I believe that it should be cecked before recovering with fabric.
As the bottom and the rear end of the stabilizer are fixed I would understand that the front top tip should be "twisted" to obtain the required measurement. The vertical stabilizer would then be "blocked" by the fabric covering.
Correct?

Thanks again.

Ciao

Gian


Inviato dal mio iPhone utilizzando SuperCub.Org
 
Yes, I do it prior to cover. After test flying and getting wings to fly level hands off I tweak the fin the fly feet off.
 
The other symmetry to check is fuselage square vertically. I was working on a J3 that was out so bad that one set of strut forks were almost all the way out, and the other were all the way in just to get close to the correct dihedral. Check the diagonals from one rear spar attach to the opposite strut attach. They should match and if they don't, fix it before cover.


Sent from my iPhone using Tapatalk
 
Thanks for the advice.
The plane has been assembled naked and checked for all rigging, dhedral, washout, simmetry, square all of which are good.
Thanks for all advices.
I will be pleased in getting any useful hint and trick.
Gian


Inviato dal mio iPhone utilizzando SuperCub.Org
 
Hello Steve,
Regarding fin alignement, which apparently is a must to have the plane to fly straight, with no foot input to withstand the prop wash.

I have measured the fin alignment while the fuselage is still naked: it is perfectly simmetrical.

You say you "tweak" (twist, bend, force) the fin after the test flights, this means, of course, with fabric and paint on: but this will not wrinkle the fin's fabric?

Someone here (Italy) claims that the fin correction is done by squaring the horizontal stabilizers then tilting the finn off its verticality

Thanks for your advice and clarification.

Gian


Inviato dal mio iPhone utilizzando SuperCub.Org
 
Piper instructions say to take the front of the verticals stabilizer at the top and apply force to it so you bend it in the direction you want the tail to go. Doesn't take much, you would be surprised what 1/4 inch will do!


Sent from my iPhone using Tapatalk
 
Make sure you have the offset as Steve described in post #2 before covering and then “fine tune” from there later.
If not; you may see a wrinkle in the fabric if major adjustment is needed. :sad:
 
Ok while naked twist the top of the fin to Steve's indication, then revover, test fly and fine tune as required.
Last query: this is a PA18/95 with a 90 Hp Continental ... is the 1 1/2 imch offset ok? (Same as for 150 Hp?)

Thsnks all for the help.


Inviato dal mio iPhone utilizzando SuperCub.Org
 
giangab said:
Ok while naked twist the top of the fin to Steve's indication, then revover, test fly and fine tune as required.
Last query: this is a PA18/95 with a 90 Hp Continental ... is the 1 1/2 imch offset ok? (Same as for 150 Hp?)
Click to expand...

I guess I can’t speak to that exactly for a 90 hp; as all of my experience is with 125 - 180 hp cubs and they are all similar.

Your “fine tuning” can go either direction.....as needed.
 
And you can use a little heat on the fabric to remove any wrinkles. Don't put the iron directly on the finish, just hold it close. It's amazing how you can fix stuff like that.


Sent from my iPhone using Tapatalk
 
giangab said:
Ok while naked twist the top of the fin to Steve's indication, then revover, test fly and fine tune as required.
Last query: this is a PA18/95 with a 90 Hp Continental ... is the 1 1/2 imch offset ok? (Same as for 150 Hp?)

Thsnks all for the help.


Inviato dal mio iPhone utilizzando SuperCub.Org
Click to expand...

It's speed related, not HP

Glenn
 
Thanks.
Where can I find this:

The instructions on bending the fin are in the Service Instruction for rigging the rag wing Pipers
 
cubpilot2 said:
I guess I can’t speak to that exactly for a 90 hp; as all of my experience is with 125 - 180 hp cubs and they are all similar.

Your “fine tuning” can go either direction.....as needed.
Click to expand...

Yes, has always worked for me.
 

Attachments

  • PIP_SM019.pdf
    155.8 KB · Views: 216
You must log in or register to reply here.

Similar threads

giangab
PA18/95 command cables trimming
Replies
5
Views
3K
Steve Pierce
Steve Pierce
giangab
Supercub headliner
Replies
6
Views
5K
KevinJ
K
giangab
Stabilizer/Elevator rigging
2
Replies
41
Views
20K
mike mcs repair
mike mcs repair
S
To de-wing or not to de-wing, what should I consider?
Replies
15
Views
2K
aktango58
aktango58
Q
Fuselage alignment- how critical???
Replies
18
Views
5K
qsmx440
Q
Back
Top