Wing/Fuse. Blanket Method

We're getting ready to cover our PA-11 and we're going to use the blanket
method. I've used alot of envelopes in the past and don't really care for them anymore. My question is, w/ the blanket, where do most people glue to on the fuse. and wings, and in what order? Thanks.

Any info? I'm getting lower and lower on the hot topics list on the home page...

According to Clyde Smith Piper glued to the center stringer to the bottom longerons. I think later they sewed their own envelopes. Stits says you must glue to structure which the center stringer is not. I have tried to pull fabric apart that was glued together and it is tough. My Clipper I am rebuilding was covered this way. I can't remember if I covered the top or bottom of the wing first. I wrap the fabric around the trailing edge on J-3/PA-11 type so you don't see any seams. On these type you can'tmake the glue joint at the top of the leading edge due to the fabric width. The Polyfiber book has a good method for covering using the blanket method. I too would be interested in knowing how others do it.

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Fuselage fabric

Most of the guys around here lap the top seam over the back bone stringer. There are trwo schools of thought as to the bottom seams. Some put the bottom on first then lap and glue the sides over the bottom. They say if any water travels down the inside of the fabric that it will not cup and collect like it would if you wrap the side fabric around the longerons then put the bottom on. The guys that put the side fabric on first and wrap it around the lower longerons then apply the bottom fabric argue that if you tear the bottom out in the brush that you can replace it without taking the sides loose. I stopped by Fairbanks a few years back to get some gas on my way through. A guy in a hanger next to the pumps was taking the fabric off of a PA-20. The bottoms of the longerons were all rusted out. I remember that the side fabric was wrapped around them with the bottom fabric applied last. You could tell that they had been wet for a long time. It made a lasting impression. Crash

Ryan on the cuby we covered the top of the wings first and the bottom last. The reason was from the ground I didn't want to see the overlap. O the fuse we covered the bottom first then the left side with the lap on the center stringer. AC 43.13-1b says b. The Blanket Method. A blanket is developed by sewing together, side-by-side, multiple sections of fabric with the seams chord-wise or two wide sections of fabric, side-by-side, placing the seam spanwise on the leading edge, the same as an envelope. Close the three remaining sides with a hand-sewn seam or overlapped and doped seams in accordance with the aircraft Vne speed. Small components may be covered by wrapping one piece of fabric over a straight leading or trailing edge, then closing three sides with hand-stitched or overlapped and doped seams in accordance with the aircraft Vne speed.




NOTE: All overlapped and doped seams will he made only over underlying supporting structures extending the full width of the seam. You would have to read the STC that you are using to determine if the seam done the middle of the stringer is legal.

Matt

Cover

Ryan,
If you don't already have it , get the Poly-Fiber manual & video. Doesn't matter what process you decide to use, these will give you the basics in an easy to understand format.

Myself, I covered the bottom of the wings 1st, with the seam right at the leading edge. The fusalage was done bottom 1st, then 2 pieces sewn together at the center stringer (thanks to Mom).

The 4130 tubing used in place of the stringers on the Univair airframes (i don't know if Airframes incorporated does that too) make it easy to use the blanket method. then you have 4 individual surfaces to cover. My 55 model had those on it when I recovered it 20 years ago. I'm sure lots of people do it, but I don't think attaching at normal stringers is the right way to go.

Thanks everyone for the advise. When you when you attach from the bottom long. to the center stringer, do cover the side of the vertical fin w/ the same piece?

It seems I remember reading in Cub Clues (Clyde Smith's piece) where it said (I believe referring to the J-5) that Piper covered the 1. belly first, 2. the sides from the bottom long. to the top long, 3. then covered from the top long. to the center stringer on both sides.

Also whats everyones thoughts on a leading edge surface tape, I've never ran one when using an envelope, but do you need one over the fabric seam/joint as you would have w/ a blanket?

Leading edge tape

The leading edge tape I prefer is a 6" pinked tape that centers on the leading edge. I like pinked tapes everywhere, straight tapes look horrible on a Cub. Yes, the fuselage sides do cover the fin, one piece per side. Make a cover (.016 aluminum riveted in place) for the jack screw hole on the "fin to stringer" fairing (you can drill it out if you ever need to change it). If you don't you will get a dip in the fabric at this point.

Run the fabric up the two little angle tubes at the tail post so your tail spring bolt is out where you can get at it and the tail post is out in the dry and not sitting wrapped up in wet fabric (lowest point on the plane). Install sea plane gromets on each side of the bottom stringer at every cross tube station and two in the very tail.

Install two 3" x 7" retangle gromets under the area of the jack screw for access if you don't have a short metal belly. Also put one on each side of the elevator horn area. One under the torque tube aileron cable arm. Two round gromets under the master cylinder attach bolts or better yet, nut plate your master cylinder bolts and forget the gromets in this area. Have fun! Crash

removed

Good discussions here on installations:
Over the years I have seen many different methods of installing fabric.
I do think that we've come a long way in improving form the original methods. I used to see brand new cubs come in with as many as 6 splicing seams in one wing. Piper did not waste anything. Some were less then 2 feet apart. The blanket method is far superior.
Crashes comment about longeron corrosion is correct as it is a trap for moisture. I like to cover the belly first to help prevent the problem.
The difficulty comes when you have a metal belly. These areas then need to be monitored closely thru the years for corrosion. I have started leaving off all metal belies except for the last piece. Figure if on floats there is less water spray finding its way inside.
I also cover each fuselage side in one piece and also attach to the center stringer. I know that the Stitts manual would say not to ,but then it defers you to the original manufactures methods. (Piper varied on this one as mentioned earlier; as most later cubs were enveloped) For example the manual also says to also not attach to ribs. Kind of hard around a cub fuel tank to avoid this but this rib has been reinforced for just that. The manual is written as a guide in installing fabric to hundreds of types of airplanes and must use blanket statements like that to cover the possibilities. They still will refer you to the manufactures method.
I will only attach to "reinforced" metal stringers using larger, stiffer attachments then the little "toe nail" clips that Piper uses. These were designed for wood stringers and stayed in use when they went to metal.
Some would worry about putting a "side load" on the stringers but that usually would only occur if the initial fabric shrinking were done "uneven", or if the stringer was not attached securely.
I have never seen one of these glued stringer seams cause a problem or loosen up. ( I had a PA-18 sprayer lose the skylite once which pressurized the fuselage. The belly fabric split down the middle but the rest stayed intact.)
To cover an 18A fuselage with sewed seams and make it look good is nearly impossible. No mater how hard you try the seams will start to "snake" on you.
Another thing I notice a lot is rib stitching techniques on the vertical fin. I have seen many cubs were people will stitch the second rib. Piper never did this and it distorts the shape. I also stick with the individual knots and the silver dollar size patches. (only three on the top fin rib) I use this on all of the other controls in the same manner as the original I think Piper added a touch of class to the look with this.
Have a great Christmas

I can add to this: I do a lap seam at the trailing edge and a butt seam at the leading edge. To make the leading edge legal, and after adding the ribstitch tapes, I glue an 8" wide strip of fabric over the LE butt seam. Then I cover the entire mess with a piece of fabric extending from 1" aft of the leading edge sheet metal on top to the same point on the bottom. All selvage edges must be trimmed off carefully, and I use pinked edges everywhere for appearance.

I use lapped edges in the fuselage, with a minimum of four pieces. Bottom and top first, then sides and rudder. To save fabric, a sewn seam can be made to join the fuselage side with the rudder piece. Hide it, by gluing a 4" tape over it, then by shrinking the tape to push the sewn area away from the exterior. If you are a scofflaw, just glue it. Not legal, but it willl never pull apart. The way you get around having to have a full two inch overlap on a glued seam backed up by structure is by citing the original Piper technique. They glued fabric to longerons, and that rarely gives a 2" overlap.

Those rib stitches on the fin always pull out for me. The last several I did had safety wire instead of rib stitch cord, and heavy reinforcement around, under, and over the rib stitch tape, and they still pulled out! But then, I love to slip!

bob