EFWD Build

[efwd]

OK, the dimples that were evident in the previous photo at the trailing edge of all the bottom false ribs was annoying. It was not the evident in person. I had glued all the ribs to attach the Oratex in spite of being told it was not necessary. Anyhow, as a testament to the forgiveness factor of Oratex I used a suction cup and a heat gun to release the fabric from the false ribs. Wha-la. I have other examples as well.

[jiott]

Yes I rib stitched the fabric to the rib on the bottom of the tanks. But I knew ahead of time that I wanted to do this, so when I glued the rib to the tank bottom I made sure my little spacer blocks didn't interfere with my stitching layout pattern. The actual stitching required a small curved needle I made out of some SS safety wire. I used individual stitches at each point, rather than try to daisy-chain them all together. Was not too difficult.

Whether its really required on the positive pressure bottom of the wing I don't know, but since they tell you to do it on the non-tank area of the wing I figured might as well carry it all the way. Besides, who knows, maybe someday I will fly inverted on purpose or not.

[efwd]

Ah nuts....
Lars, from Better Aircraft Fabrics stated that the Oratex glue is so strong that lacing would not be required anyplace on the wing. As the Kitfox manual states that with one inch wide cap strips it used to not be necessary but they and PolyFiber recommend it. Hmm. I can flex the cap strip where they support underneath is nonexistent, so I can put some in but I will have to accept odd spacing Im sure once I start doing it and run into the spacers. I believe I have two in there.

[jrevens]

I didn't lace that rib, Eddie... just the tail end behind the tank. For some reason my tanks didn't allow anything but capstrip (very few, thin spacers) to be level with the other ribs, so it was not possible for me anyway. If yours is like mine, you have a little more glued surface area at the leading edge because of the Laker leading edge also. I have seen a few very nice Kitfox aircraft that the builders admitted they didn't actually lace that entire rib, but they made it look like they did by using short little pieces of cord glued to the surface... fake stitches. I didn't do that... just glued the fabric down good with that super-duper Oratex glue. I flew in a Mod. IV once that had 100 hp and no rib lacing at all. It had quite a few hours on it, and the covering seemed to be doing just fine... it was actually a little loose in my opinion, and you could see it billowing a little as we flew, pulling against the glued areas. I wasn't so sure I liked that, but I guess it had been flown like that for a long time.

[efwd]

Thanks John. I didnt use the Laker LE but I have glued to the false ribs and I am aware many people dont. I believe that billowing would not be chanege with lacing but in our case with Oratex another heat shrink would improve that. Ill admit I have employed the Faux stitch on a couple spot that I put holes under where the flapperon bracket belongs and therefore would not get a stitch. I simply was trying to avoid having empty holes visible under the UL600 tapes.

[David47]

I'd really like to know the peel strength of a glue holding fabric down before I decided not to rib stitch. Consider rib stitching as the belt that holds the pants up if the breeches snap ...... That's not to say you need to do it everywhere. On the positive pressure side where you're talking about, you can probably get away with it. On the suction side, not so sure ... just saying.

[jrevens]

I'd really like to know the peel strength of a glue holding fabric down before I decided not to rib stitch. Consider rib stitching as the belt that holds the pants up if the breeches snap ...... That's not to say you need to do it everywhere. On the positive pressure side where you're talking about, you can probably get away with it. On the suction side, not so sure ... just saying.

Not to keep hogging Eddie's thread here, but I agree David. As I believe and have stated on this forum, I don't know why anyone wouldn't rib stitch their Kitfox... it takes a relatively small amount of time and is good insurance. When this subject comes up, I always remember how & why Steve Wittman died when the wing fabric on his airplane came loose. It was not laced to the ribs.

[efwd]

John, dont ever hesitate to reply in my threads. Your input is one among others that I wait patiently for.
David, the peel strength for the Oratex glue is reportedly in excess of 100#per sq inch. I can say that I'm not able to pull it off even the narrow false rib with out heating it to over 300 degrees to soften the glue. I was told that it is somewhere around three times the strength of the Polyfiber product. I cant say I have even heard what air over the top side of a wing is capable of exerting.
Eddie

[mr bill]

I do not have numbers, but the Stewart Systems (really 3M I think) is very strong in tension or peel and many times stronger in shear.

[jiott]

Just a couple of comments FWIW: Remember the peel strength of the fabric glue is to the VARNISH on the ribs, not to the bare wood. You are not only relying on the fabric to varnish bond, but also on the varnish to wood bond-whichever is weaker. Also, the bottom surface of the wing is slightly undercambered, putting a constant tension trying to pull the fabric away from the ribs. I like the insurance and peace of mind given by rib-stitching.