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Wing recover

cubpilot2 said:
Update: So I did just that... Using the heavy weight fabric we sewed the three strips together and using the old methods of attachments at the trailing edge. The difference in scalloping between the blanket method and this was amazing!
The photos below is of a cub covered with the heavy fabric in the blanket method (glued span size to the leading edge.) The scallops are 5/8 or more between ribs depending on the rib spacing.

With the "envelope type" method on the wing that I just finished in silver, the scallops are 3/32 to 1/8 inch deep as measured with a strait edge over the cap strip reinforcing tapes.

The Red wing is my 180 cub with the 12 inch L.E. extension.

I am no aeronautical engineer but IMO when you allow the vertical cross section of the airfoil to be reduced this way; that there has to be some difference in the lift component.

I would bet that if you did one wing with the blanket method and the other in the envelope; that it would be wing heavy as hell.
Click to expand...

no...

It all has to do with the order of which direction you shrink it.....
 
The end shape during flight is totally different anyway, as the fabric balloons up instead of being stretched down. The tighter fabric may end up shaped more like the ribs than the other one.


Sent from my iPad using Tapatalk
 
mike mcs repair said:
no...

It all has to do with the order of which direction you shrink it.....
Click to expand...
Correct, place the iron on the ribs first to shrink the fabric span wise. This will pull the span wise fibers up to the level of the ribs. Then shrink between the ribs. If you shrink between the ribs before the fabric is pulled up to the rib caps it WILL always have a belly in it.
 
skywagon8a said:
Correct, place the iron on the ribs first to shrink the fabric span wise. This will pull the span wise fibers up to the level of the ribs. Then shrink between the ribs. If you shrink between the ribs before the fabric is pulled up to the rib caps it WILL always have a belly in it.
Click to expand...

That is what I always thought.
Keep in mind that this is the "heavy weight fabric; and medium does not react the same. I was involved in all of the wings in the photos and they were all ironed using the same basic technique.
The Polyfiber manual even corroborates what I experienced. They say that you Will get the scallops with the heavy fabric! I just never thought that it could be to that extent, and that it is preventable.

I have aireal photos of the Blue cub and the wing fabric does not balloon up. The shape is still there.
The airplane is also a good performer and flies nice.

In the old thread mentioned above the guy built a 2 x 2 frame of pvc pipe as it is flexible enough to show the stresses; and covered it with the heavy fabric.
When shrunk the frame distorted nearly an inch in one direction and hardly any on the other. It does not pull evenly.

IMHO either use medium wt fabric or change your install methods to avoid the scalloped look. After seeing how tight and flat this turned out; I am no longer seeing as much desire for the extended leading edge.
 
It also depends on which generation of fabric you have. I have seen a lot of differences in the shrinking characteristics with the runs of fabric over the years.
 
The 1991 Stits manual states the thread count at that time was equal in both directions. I would guess that would have a big influence on how the fabric reacts to heat.
 
cruiser said:
The 1991 Stits manual states the thread count at that time was equal in both directions. I would guess that would have a big influence on how the fabric reacts to heat.
Click to expand...
That is correct, but if you start shrinking in the bay between the ribs the chordwise fabric will pull down between the leading and trailing edges before the spanwise threads holding them down creating the scallop.
 
I'm getting close to placing my wing order from Javron and Jay is admandtley against the wing leading edge extension but I'm getting mixed reviews. Have you guys who have done it totally happy with it? Worth the weight?
Blue Skies,
Denny
 
flylowslow said:
I'm getting close to placing my wing order from Javron and Jay is admandtley against the wing leading edge extension but I'm getting mixed reviews. Have you guys who have done it totally happy with it? Worth the weight?
Blue Skies,
Denny
Click to expand...

I add it to every one I do
 
flylowslow said:
I'm getting close to placing my wing order from Javron and Jay is admandtley against the wing leading edge extension but I'm getting mixed reviews. Have you guys who have done it totally happy with it? Worth the weight?
Blue Skies,
Denny
Click to expand...
My Backcountry wings have the extended leading edges. The Cub has lots of other little changes so I can't say exactly what this mod did other than to say the fabric stays flat on top with no scallops and the plane is a super performer at all ends of the flight envelope without VGs. It also has the extra long 110" flaps.

I also glued a thin layer of felt to the LE skin to smooth out the bumps of the fastener screws. Can't say whether that did anything other than it sure looks good. It took a lot of Stuarts glue to do the job so there may just be extra weight with no functional performance improvement.
 
Extended leading edge will make for a stiffer wing. The big question is how much twist do you want to put into the wing as you build it?? One way to figure this is to build the wing and put it on the fuselage before you do the extended leading edge. Rig the entire plane/wing as you want. This will correct for any fuselage issues. Now you how much twist to put into the wing, take it off and add the leading edge with the twist set on sawhorses. Lots of cubs flying with .5 degree vs stock 2 degree of twist and doing fine. Just some points to make more work for you and things to think about.
DENNY
 
DENNY said:
Lots of cubs flying with .5 degree vs stock 2 degree of twist and doing fine.
Click to expand...
This is fine, but deserves a little discussion for those who may not know why the twist is in the wing in the first place. Twist (wash out, leading edge down) is done in order to ensure the wing root stalls before the tip. Why? To ensure that there is aileron control into the stall regime. This is more important on airplanes which do NOT have differential aileron control (More up travel than down travel). Guess what, the CUB does not have differential aileron control. As a result the outboard section of the wing can stall before the root especially if the aileron is deflected down. Thus it is very important in a Cub to use plenty of rudder to assist the aileron when a wing drops during stalls. I do not know why some may choose to use .5 degree of wash out rather than Piper's 2 degrees. Me, I'll use the 2 degrees.

There was extensive discussion here a few months back about a fellow who stalled and crashed his Cub with no visible rudder input correction in an attempt to keep the wings level. Thus the stalled wing hit the ground first.
 
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The only two reasons I can think of for taking twist out is to correct for fuselage issues or to make it fly slower, The main point I was getting at is if you want to run it at .5 degrees don't build in 2 degrees. It is a pain to hang it on the fuselage just to check everything but it can save time in the long run.
DENNY
 
I think what he meant was that the more twist (washout) is in the wings, the less angle of incidence the wingtips have. The wing root will maintain the AoI set at the wing attach.

Angle of Attack is the angle of the wing's chord line to the relative wind, and is a primary factor (along with airspeed) in generating lift. Angle of Incidence is the angle of the wing in relation to the fuselage.

Need more AoA? Pull back on the stick. Need more AoI? Break out the welder.
 
mike mcs repair said:
normally??

or what I do?
  1. all steel parts removed sent for blasting, inspection, powder coating
  2. all hardware removed is replaced
  3. wing measured & trammed
  4. ribs replaced as needed
  5. hanger blocks replaced or repaired as needed
  6. new leading edge from Univair blanks since it's already removed(and is less time/$$ then cleaning and bondoing old junk..
  7. maybe replace trailing edge if bad shape...
  8. maybe prime leading and trailing edge to help prevent corrosion..
  9. hang and align flaps and ailerons with wing in proper twisted position
  10. replace tip wood bow
  11. replace lighting wires
  12. add Atlee Hurricane tie downs if not already installed
  13. extend top leading edge back 14"~ if wanted..

thats the pre fabric 2 minute thoughts...
Click to expand...

Kind of late to the party: 1)To Mike's list I would add Atlee's spar/strut attach fitting reinforcement and leave off the stock tie down ring and 2) I probably would not add the extended leading edge. Watch the trailing edge, of the extended edges, when sweeping the wings of snow. The edges between the ribs can dent and show through the fabric as the fabric will be attached through the covering process.
 
Skywagon
I always appreciate your input, and would advise others to do also. Some of my posts are short and don't cover all the aspects of a issue. Your input along with several other members are what make this forum valuable!! We just all need to get in the same place with a six pack, case, or keg of beer and have a good hanger flying week!! I have a open room if you want to visit AK!!
DENNY
 
I am ready to apply covering to the wings of my experimental PA12 not originally built by me. Is it necessary to have them inspected prior to recovering with new fabric after repairs were made as necessary?
 
jimboflying said:
I am ready to apply covering to the wings of my experimental PA12 not originally built by me. Is it necessary to have them inspected prior to recovering with new fabric after repairs were made as necessary?
Click to expand...

can't hurt... I don't mind someone looking over my work, even though I think It's perfect... maybe they will find a brain fart...
 
jimboflying said:
I am ready to apply covering to the wings of my experimental PA12 not originally built by me. Is it necessary to have them inspected prior to recovering with new fabric after repairs were made as necessary?
Click to expand...
Deffinately worth the effort, things can easily get missed or not properly located, think of it as a peer review.
 
Last edited:
Since you did not build it you will need an A&P to do your condition inspections. Whoever that may be should be brought into the loop sooner rather than later.
 
skywagon8a said:
This is fine, but deserves a little discussion for those who may not know why the twist is in the wing in the first place. Twist (wash out, leading edge down) is done in order to ensure the wing root stalls before the tip. Why? To ensure that there is aileron control into the stall regime. This is more important on airplanes which do NOT have differential aileron control (More up travel than down travel). Guess what, the CUB does not have differential aileron control. As a result the outboard section of the wing can stall before the root especially if the aileron is deflected down. Thus it is very important in a Cub to use plenty of rudder to assist the aileron when a wing drops during stalls. I do not know why some may choose to use .5 degree of wash out rather than Piper's 2 degrees. Me, I'll use the 2 degrees.

There was extensive discussion here a few months back about a fellow who stalled and crashed his Cub with no visible rudder input correction in an attempt to keep the wings level. Thus the stalled wing hit the ground first.
Click to expand...

Think aileron reversal at low speed. This was a characteristic of my Howard and the first time it happened it scared the **** out of me! Crosswind landing in the flare, ailerons displaced for the crosswind and the wing with the down aileron (the one you want to go up) stalls and that wing drops suddenly. That's the reason for wash out.


Sent from my iPhone using Tapatalk
 
dgapilot said:
Think aileron reversal at low speed. This was a characteristic of my Howard and the first time it happened it scared the **** out of me! Crosswind landing in the flare, ailerons displaced for the crosswind and the wing with the down aileron (the one you want to go up) stalls and that wing drops suddenly. That's the reason for wash out.
Click to expand...
Good example, Thank you. That would be scary.
 
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