Wing Covering-Rib Stitch or Not

[Larry H]

I will be covering my main wings soon. What is the consensus on Rib Stitching or Not Rib Stitching? I’ve heard some say no rib stitching is necessary on a Legal Eagle or Legal Eagle XL. Just glue the fabric to the ribs without rib stitching is what I have heard from some people. I wish I had more faith in glue ony. What do you all think? I’m building a Legal Eagle XL.

[Kamcoman77]

Some in flight videos show the covering fluttering a good bit under the wing in the prop blast area, don't know about on top. I think I'm going to rib stitch the center section, out to rib #7, then just go with the glue from rib #8 outward (XL).

[Larry H]

I mistakenly posted my same questions in the For Sale area. Charles replied there and stated he used glue only with no rib stitching and has been flying his inside hangar stored Legal Eagle for 6 years with no separations.
Charles if you see this what process did you use? What I mean is when you started on a wing surface did you attach the fabric with your iron around the perimeter, then shrink the fabric before you ironed the fabric onto the ribs or did you iron the fabric around the wing perimeter and onto the ribs at the same time then shrink the fabric in between the ribs? Kamcoman your idea sounds like a good idea and thank you and Charles for your replies. I would be interested in more responses or ideas from others also as to how you covered your wings.

[CHARLES DEBOER]

I used the Stewart System.  Look up the videos on you tube . You can buy the materials from them but the glue is cheaper if you buy the Three M product.  I purchased mine from the Aircraft Spruce. Follow the instructions, watch their videos. I have never built an airplane before and it works great.  https://www.youtube.com/watch?v=v5chb_LPxb4

[Larry H]

Thank you Charles. Yes I’m also using Stewart’s System. I’ve watched these videos a few years ago. The way he is showing in this video he will be rib stitching or using the clips that snap through the fabric into/onto the ribs. The wire clips are used on some airplanes rather than rib stitching. Many years ago I owned a Cessna 120, I believe that one used wire clips to attach the wing skin to the ribs. In this process the tape is applied to the rib surface to protect the wing covering fabric from abrasion because the wing fabric is not glued to the ribs which means the wing fabric can move around while flying. Most all old fabric covered airplanes use this technique. My understanding is that some guys that have built Legal Eagles have glued the fabric directly to the wood rib surface, no tape involved. If I were to use tape on the rib surface then I’m depending on the tapes glue to hold it all in place if I were to glue the fabric onto the tape. Just thinking about it logically if I’m going to glue the fabric directly to the ribs I don’t need to worry about wind flopping abrasion of the fabric across the rib surface. 
Does anyone have an opinion on this?

[CHARLES DEBOER]

I used felt instead of adhesive tape.  After the final shrink of the material I applied pinked seam tape over each rib glued and ironed down each rib.

[Larry H]

Thank you Charles, the pinked seam tape over each rib is a good idea if the builder is not going to ribstitch.

I decided to call Leonard today and see what he had to say about procedure he used and recommended. First off I am using the water base Stewart’s glue system for my Legal Eagle XL and Leonard uses the Stits now PolyFiber system. The technique Leonard used was paint the (Poly Tak (I think is correct, follow Poly Fiber instructions) on the perimeter and Rib top edges, let the applied Poly Tak dry. Apply the fabric over top and glue the perimeter of the wing sticking it down according to Poly Fiber instructions, probably ironing it down? Next Iron/shrink the wing fabric in required steps to the correct taughtness. Once the fabric is taught follow the Poly Fiber instructions to stick/glue the fabric directly to the wood surface of all the ribs. Bottom line is Mr Milholland didn’t recommend doing any rib stitching, just glue the fabric to the entire rib surface only. I thought I had heard him say it’s a waste of time to rib stitch in a forum maybe. So the KISS (Keep It Simple Stupid) side of me would rather not do any Rib Stitching and the scared side of me says maybe I should do some rib stitching like Kamcoman77, I’ll have to think more on that before I start covering my first wing.
In the interim I’m going to the shop and glue a scrap of wing covering to a rib stick and see how tough it is to tear off if it’s even possible to tear off.

[DA Miller]

I believe a poly tac demo had two pieces of fabric glued together and they could not be pulled apart but one fabric could easily be peeled from the other.  My point is: peel strength and shear (?) strength can be very different. Keep this in mind when you do your glue test.

[Kamcoman77]

If you really want to see how strong your Stewart System would be, I suggest you test several setups. Suggest a small box of 5 sticks with middle stick a 1/4x1/4 piece for a "rib", so you can test gluing & shrinking fabric. 1st - EkoBond on bare wood, let dry, fabric, iron along perimeter glue line to set glue on frame but do not iron along rib, shrink, iron along rib glue line, add EkoBond on fabric over wood and wipe excess with paper towel. 2nd - Same test but coat wood with your choice of varnish (sand lightly) before any other work. 3rd - Same test as 1st except add your choice of tape over "rib" before any other work. 4th - Same test as 2nd but add your choice of tape on "rib" before any other work. Wait a day and push the fabric from underneath trying to lift it from the "rib" and see what happens. I think you will find the strongest joint will be the varnished wood without using any tape between wood & fabric. Sounds like a lot of work, but at least you will have first-hand knowledge of how strong your bond is.

[DA Miller]

Kam, first of all you have suggested a very comprehensive and valid test of the glue/fabric bond.  Thanks for that.  I was planning on gluing my fabric directly to the bare wood of the rib.  I'm not arguing about the stronger bond between the fabric and the varnish, but I'd like your opinion on why this is so. Did you establish this through your own testing? I value your input on this TKS

[Kamcoman77]

It was a couple of years ago that I made up some samples of bare wood and varnished wood. As I remember, the fabric stuck about the same on some of my samples and better to the varnished wood on others. I decided to varnish all my wood before fabric because it was easier than masking all the ribs, and there was no instance of the fabric to bare wood sticking better than to varnished wood. I'm using Varathane water-based spar urethane varnish since my Stewart System glue is water-based.

[DA Miller]

Thanks Kam for that input. I'm going to my local HW store to check out water based varnish.

[Chuck in Indiana]

Because "The Kid" said he'd feel better if I rib stitched.. I'm going to do that.I'm still not in the mood, though.  The weather has been really nice this summer, and I've been playing motorcycle.
Grand Kid Max will be visiting for a few days over Thanksgiving. He's taking Aerospace engineering at school and is interested in all things that fly, but especially rockets.
During his visit, I'll let him learn about whitewashing a picket fence rib stitching..

[Larry H]

I called Marty Feehan that teaches the STEWARTS SYSTEM at Oshkosh a lot of years. He was missing from Oshkosh this year because of a bad knee.
Marty told me he would rib stitch some. He suggested at least a 6” spacing. I think I’m going to do that. For some reason I can’t seem to wrap my mind around trusting the glue only.
Chuck your idea of allowing your grandson to touch your airplane is admiral of you. Be sure to tell him how fun it is and your not so sure he should get to have all that fun! 😉

[Chuck in Indiana]

Be sure to tell him how fun it is

Noted. 
FWIW, and I know this is comparing apples and potatoes..Ed the Rocket Scientist (RIP) and I built a Pitts S1S back in the day. Our goal was to keep it as light and clean as possible. We were successful. I don't remember the empty weight now..I'm old..but it had an O-320, fixed pitch prop, no electrical system, and would out perform a 180 Pitts with a constant speed. Ed was raised by Matty and Elsie Laird, and knew some speed tricks.
One of the reasons it was so light was we used the light weight Stits HX 90 (?) fabric that was available at the time. Fortunately, we rib stitched it at (from memory again) 1 inch. It was a good thing. In flight you could see the fabric balloon up between each rib bay..(!!)
Here's Ed in happier times.