ready to cover the wings

[Geowitz]

Thank you Lowell for that most reasonable response.

Does it hurt to rib stitch?...No, but does it hurt not to rib stitch?... I see no evidence of that on a Kitfox.

[jtpitkin06]

Thank you, Lowell, for your line-by-line analysis of my posting. At least I know someone is reading it in entirety.

However, you didn’t comment on one of the most important lines. Specifically that 2 of the 3 major covering manufacturers do not recommend omitting mechanical fabric attachment.

If someone using Stewart Systems wishes to omit lacing, that’s their choice. It’s not my choice, but I won’t sneer at the decision. Even so, Stewart Systems recommends you do rib lacing. Note the reply from Stewart did not say up to what speed the “glue only” application qualifies. There are no speed charts available so you are on your own.

If using something other than Stewart Systems, disregarding the manufacturer’s instructions is not in my comfort zone.

No, in my vast data base of aviation knowledge, I don’t have an example where the wing covering came off a Kitfox. My position is we shouldn’t have to wait for someone to get killed before we decide to follow the recommended procedures. We have 100 years of experience with fabric covered wings. The covering manufacturers have done massive amounts of testing to get approval for their STCs so it makes sense to me to follow their lead. The problem with simply covering a Kitfox and flying it without lacing is: You don’t know if you have a 50% safety factor or a 5% safety factor.

While I’m sure many of the readers are comfortable flying without rib lacing, there may be some who are on the fence. If I get the undecided to at least consider the pros and cons then I’ve done my job.

Thanks for reading.

John Pitkin
Greenville, TX

[xpflyr]

John, I read your whole post but even before I did, I decided to rivet stitch.
( That's their method of mechanical attachment on the Highlander )
I wasn't going to because I didn't like the look. Seems silly now but what can I say. Do I think the fabric would have come loose had I not? No,, I don't but since I'm building why not take that possibility out of mind? So I did.
Thus the wonder of experimental building. Also, that retail thought was a good one.
Don

[jiott]

Maybe I'm wrong, but it sounds to me like the discussion here is mostly about if the fabric will come off the wings and cause an emergency if you do not rib stitch. I think that is highly unlikely. The much more likely scenario is that the fabric will start to peel off the upper capstrips and eventually become unattached. Because of the tightly shrinked fabric, this condition will be almost unnoticable and hard to test for on the ground. What will happen is that in the air the fabric may lift off the capstrips, probably only a small amount, but nevertheless destroying the proper airfoil shape of the wings and causing a loss of performance and efficiency. This could remain unnoticed for years.

Jim

[HighWing]

Jim,

I agree with your assessment, but again an observation. There were a couple of Kitfoxes in a neighboring airport as I was building. Over their wing tanks, the Polybrush stuck the fabric to the wing tanks in a hap- hazard pattern as the wing tank did not have a perfectly smooth surface. This made the final color finish look pretty ugly - severely marbleized look.
I didn't want that and took great pains to avoid the fabric being glued to the top of the wing tank anywhere. It was a chore, but I was able to accomplish that goal. Also consider that the number two rib normally there is missing due to the wing tank, except for the false rib on the bottom surface - imagine a rib on the top of the wing with total loss of fabric attachment. Then sometime during the 9 years I flew it, I thought of exactly what you are proposing as the top of the wing is the critical lift portion of the airfoil and my build modification concerned me. During a group flight, I asked a buddy to come in close and see if he could see any evidence of ballooning over the wing tank. The answer was no, but then again, I suppose the greatest negative pressure would be just before the stall and I was never able to check that. However this thought reminded me of someone who did.

Check the two YouTube videos –
http://www.youtube.com/watch?v=bIsWseMbDQU
http://www.youtube.com/watch?v=gor7LhsAILs
I was surprised that there was not more puffing up between the ribs and false ribs especially in the stall. I think the fabric flutter in the first video is due to shrink issues. Inadequate shrinking over the wing tank may be due to the heat sink effect of the wing tank under the fabric. Folks sometime comment on wrinkles near the filler necks and the first rib. It usually happens on a very cold morning when it is visible on prefight.

Still, I agree that your proposition is likely to be the most common issue.

Lowell

[Dave Holl]

Don't know weather this link will work but the article is interesting even more so to me as I also fly this type and it was made in 1963!
http://www.lightaircraftassociation....ety%20spot.pdf
Dave