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Thread: ready to cover the wings

  1. #11

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    Default Re: ready to cover the wings

    There big, very flat alum rivets spaced every 3 inches.
    They are placed on 1/2in wide reinforced tape.
    This is how they do it for the Highlander.
    Last edited by xpflyr; 07-06-2011 at 04:12 AM.

  2. #12
    Senior Member jiott's Avatar
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    Default Re: ready to cover the wings

    For what its worth; shear strength of the glue is not whats important. It is the peel strength, which is always much less than the shear strength. The low pressure area on top of the wing will tend to try to peel the fabric up off the capstrip, a little at a time untill the whole strip is loose. All it takes is that one big unexpected patch of turbulance to get the process started.

    Jim

  3. #13
    Senior Member HighWing's Avatar
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    Default Re: ready to cover the wings

    regarding John's non soapbox, "stop the madness" comments, I would like to make a comment, correct some misstatements, and then render an opinion.

    With the early Kitfoxes, and I have to remind everyone here, that Kitfox did not emerge onto the scene as a 140 mph series 7, or Supersport, The build manual called for a final shrink temperature of 300°. Polyfiber insisted that final shrink temps should be 350°. The arguments raged on the forums then as now, and some caught the "fever" and the result was a lot of wasp waisted Kitfoxes with scalloped trailing edged on their wings. I think a bit of judgement is appropriate here as well, as we are not all building the same airplane. I am finishing a kit purchased in 1992. I am still using the same 1.7 oz. ( ultralight) fabric supplied with the kit - shudder, from all you that read today's literature. My reasoning is that I had 900 hours on my original 1993 kit with no issues. And fabric issues were topics that were never discussed with contemporary builders and flyers. It was simply never an issue. The same can be said with the rib lacing issue. In the day, it was simply a non issue.

    "Face it folks, general aviation has an abysmal safety record and experimental aviation is even worse." John, I need at least one instance where failure to rib lace on a Kitfox has contributed to this abysmal record.

    Weight - Agreed, definitely not a significant issue.

    "Aerodynamics are virtually unaffected" - also no argument here.

    Labor - "The labor involved is maybe six hours, tops…" Not true. A friend earns pocket money doing exactly this and reports that it takes 11 hours per wing on a Cub. I spent in excess of that on my current project - Try riblacing under the wing tank for example. For the typical 40 hour a week guy, it will take two or more weeks on his project to rib lace.

    Expense - "Not much more than a hamburger lunch". Wrong again unless you are talking about the famous $100 hamburger, but with that lunch you get an airplane ride and a tank of gas. Lets look - Current ACS prices.

    Rib lace tape $52.70 (half inch side by side, top and bottom)
    Riblace Cord $42.15 (flat - low profile)
    Needles $2.20 - $18.60 (per each - $40.75 Assortment)

    Pretty much the $100 lunch, And remember that not everyone out in real world land paid $18,000 for their project with $18,000 for their engine and another $7,500 for their glass cockpit. Some guys are looking at used or alternative for reasons that others might not fully understand.

    Appearance - "Oh, yes… the prettiness factor. No lacing bumps looks nicer than bumpy… That’s a hoot! I never hear anyone say a Staggerwing Beech is ugly because it has rib lacing!!! Real pilots will know what the bumps are for and non-pilots won’t know and won’t care if you have them or not." Come on, John - no one has proposed the arguement that they are not riblacing because it is ugly.

    I guess what excercises me on this issue, is because this argument is right in tune with the times. Someone, whether it be government or some other superior thinking group or individual is arguing for the elimination of a more individually arrived at decision. Consider California. I as an individual home owner am in violation of a new law, that my all electric home with a decorative, inoperative fireplace needs by statute, a carbon monoxide detector. But then consider their argument - sound familiar? - 30-40 die each year from carbon monoxide poisoning. And again, it doesn't cost much more than a hamburger lunch to comply. We'll pay about $400 million to save at most 40 lives. You do the math.

    For the vast majority of Kitfoxes out there, I strongly support the decision not to rib lace. For those who choose to rib lace, I have no reason to challenge that decision. I did it twice and in fact did it on the empennage of my current project for reasons of my own.

    One size does not necessarily have to fit all.

    Lowell

  4. #14
    Senior Member Geowitz's Avatar
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    Default Re: ready to cover the wings

    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.

  5. #15
    Senior Member jtpitkin06's Avatar
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    Default Re: ready to cover the wings

    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

  6. #16

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    Default Re: ready to cover the wings

    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

  7. #17
    Senior Member jiott's Avatar
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    Default Re: ready to cover the wings

    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

  8. #18
    Senior Member HighWing's Avatar
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    Default Re: ready to cover the wings

    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

  9. #19
    Dave Holl's Avatar
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    Red face Re: ready to cover the wings

    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
    Dave Holl
    Building Kitfox MK7
    Rotax 912ULS

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