The Biplane Forum > Biplane Builder's Forums > Pitts > Pitts S-1C Rig Specs



Help Support Biplane Forum by donating using the link above or becoming a Supporting Member.
Reply
 
Thread Tools Display Modes
Old 10-23-2017, 12:28 AM   #1
Z32MadMan
Registered Users
 
Join Date: Nov 2015
Posts: 33
Liked 1 Times on 1 Posts
Likes Given: 2

Default Pitts S-1C Rig Specs

The flying and landing wires on my S-1C are way under tensioned. I took wing measurements with a set of rigging boards today and the wings look a little mis rigged.

Does anyone know the incidence, dihedral, and wash specs should be for the upper and lower wings of an S-1C?

Also I went to turn the first of my flying wires as part of the tensioning process and found the top part of the wire would not turn. After pulling the panel on the upper wing mounting point, I noticed there is one lock nut on the outboard side and a jam nut on the inboard side of the flying wire. Can someone confirm for the inboard nut is not supposed to be there?

Thanks!


IMG_20171022_162006.jpg   IMG_20171022_162445.jpg  
Z32MadMan is offline  
 
Reply With Quote
Old 10-23-2017, 01:10 AM   #2
cwilliamrose
BiP_LIFETIMESUPPORTER.png
 
cwilliamrose's Avatar
 
Join Date: Nov 2009
Location: SW Florida
Posts: 6,774
Liked 1388 Times on 1037 Posts
Likes Given: 9

Default

That second nut (the jam nut) should not be there, it should be under the stop nut. No need for those washers, they should be removed.

As for specs, there should be no wash in any of the wings. The top wing should be flat (straight, no dihedral) and the length of the I-struts set the lower wing's dihedral. There are no adjustments for the incidence at the fuselage unless you're will to do major surgery and welding.


__________________
...........Bill

Project:Stretched Pitts S-1SS

cwilliamrose is offline  
 
Reply With Quote
Old 10-23-2017, 01:27 AM   #3
Z32MadMan
Registered Users
 
Join Date: Nov 2015
Posts: 33
Liked 1 Times on 1 Posts
Likes Given: 2

Default

Okay so the inner jam nut should be removed, threaded into the end of the flying wire and then chased with the lock nut, correct?

And got it. Keep the wings as straight and flat as possible. What should the lower wing dihedral be set to?
Z32MadMan is offline  
 
Reply With Quote
Old 10-23-2017, 01:35 AM   #4
cwilliamrose
BiP_LIFETIMESUPPORTER.png
 
cwilliamrose's Avatar
 
Join Date: Nov 2009
Location: SW Florida
Posts: 6,774
Liked 1388 Times on 1037 Posts
Likes Given: 9

Default

Yes, the two nuts work together with the stop nut last in the stack.

I wouldn't worry about the lower wing dihedral other than to make sure the dihedrals match fairly closely. They should be 3 degrees per side.
__________________
...........Bill

Project:Stretched Pitts S-1SS

cwilliamrose is offline  
 
Reply With Quote
Old 10-23-2017, 05:27 AM   #5
EAABipe40FF
Registered Users
BiP_SUPPORTER.png
 
EAABipe40FF's Avatar
 
Join Date: May 2009
Location: Springfield, WV
Posts: 4,376
Liked 830 Times on 660 Posts
Likes Given: 579

Default

Again as Bill already said. Top wing straight and the I-struts set the lower wing dihedrals. It will be what it is unless you build new I-struts.
__________________
Finished Spezio Tu-holer N92JM(Oct. 2011), AcroDuster 2- SA750 N22JM, first flight 12-14-15
2Cor5:17
EAABipe40FF is offline  
 
Reply With Quote
Old 10-23-2017, 01:56 PM   #6
cwilliamrose
BiP_LIFETIMESUPPORTER.png
 
cwilliamrose's Avatar
 
Join Date: Nov 2009
Location: SW Florida
Posts: 6,774
Liked 1388 Times on 1037 Posts
Likes Given: 9

Default

Or you can reduce the dihedral with a washer stack or spacer. But the limit according to the plans is 6 washers at each I-strut mount bolt. Unless the I-struts are completely mismatched you should be OK.
__________________
...........Bill

Project:Stretched Pitts S-1SS

cwilliamrose is offline  
 
Reply With Quote
Old 10-24-2017, 01:10 AM   #7
EAABipe40FF
Registered Users
BiP_SUPPORTER.png
 
EAABipe40FF's Avatar
 
Join Date: May 2009
Location: Springfield, WV
Posts: 4,376
Liked 830 Times on 660 Posts
Likes Given: 579

Default

No argument Bill but 6 washers, maybe half an inch? I'd just take it as it is. Of coarse if one is different maybe add washers to equalize?

If I-struts are too much different maybe check for other errors? (Been there/done that with my EAA bipe)
__________________
Finished Spezio Tu-holer N92JM(Oct. 2011), AcroDuster 2- SA750 N22JM, first flight 12-14-15
2Cor5:17
EAABipe40FF is offline  
 
Reply With Quote
Old 10-24-2017, 01:20 AM   #8
cwilliamrose
BiP_LIFETIMESUPPORTER.png
 
cwilliamrose's Avatar
 
Join Date: Nov 2009
Location: SW Florida
Posts: 6,774
Liked 1388 Times on 1037 Posts
Likes Given: 9

Default

Yeah, that was my point -- if there's a significant difference you could use washers to improve that situation. 6/16 = 3/8" Not much adjustment available especially when you figure some washers might already be there for correcting the incidence. If I found a difference that needed to be corrected I'd at least see if the struts are different and might be in the wrong locations.

That said, I have yet to work on an airplane that was in need of dihedral adjustment.


__________________
...........Bill

Project:Stretched Pitts S-1SS

cwilliamrose is offline  
 
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump