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Thread: Blind rivet construction

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    Blind rivet construction

    I've been to a Sportair workshop and got some experience with dimpling and solid rivets but I am very interested in building a CH-650.

    As I look at the construction using the blind rivets, Zenith has you use a special head in the puller to turn the flush head rivet into a dome shaped one.

    My question is this...would dimpling the skins and using an unmodified rivet puller head to achieve a flush rivet be acceptable? Seems that it would improve the "bond" of the sheets (since the dimples sit inside each other) and also improve the aesthetics (which of course is subjective). Probably not going to do much for reducing drag...or would it?

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    Registered User Monty's Avatar
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    Re: Blind rivet construction

    As I look at the construction using the blind rivets, Zenith has you use a special head in the puller to turn the flush head rivet into a dome shaped one.
    I'm relatively certain you could accomplish the same thing on your puller with a carbide burr or a countersink in a lathe, or a drill press if you are careful.

    My question is this...would dimpling the skins and using an unmodified rivet puller head to achieve a flush rivet be acceptable? Seems that it would improve the "bond" of the sheets (since the dimples sit inside each other) and also improve the aesthetics (which of course is subjective). Probably not going to do much for reducing drag...or would it?
    There is a man near me who did this on another airplane (I can't remember what the kit is right now) He filled the rivet heads with epoxy.

    This is what I plan to do on my airplane. Drag reduction depends on how fast you go. Most of the rivets are in a line parallel to the airflow, so the drag reduction is probably not that huge. Never the less, that is what I am doing.

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    Re: Blind rivet construction

    xxxx
    Last edited by stol; May 5th, 2012 at 07:46 PM.

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    Registered User Monty's Avatar
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    Re: Blind rivet construction

    2- The concept of doing this is to make a inexpensive fastener using quality flat head blind rivets. When you pull a falt rivet head into that half round cavity two things happen. It creates a round headed rivet that clamps the material you are joining together. As the rivet id pulled into that half round shape tip the aluminum flat rivet head work hardens and makes a tough and durable fastener. By just dimpling the skin and using a flat head pull rivet will not be sufficient to properly clamp the skins together. Reason being is the pulled rivet is soft and is hollow in the middle where the pull pin is located. A regular aircraft rivet is solid and is alot stronger. Zenith taked the reduced holding force into account and adds more rivets the if that area used bucked rivets. IMHO.
    I disagree. If you dimple and use aircraft practice, the shank breaks off in the head. The shank is a structural member. There is no reason that the clamping force would be any better with the magic machined pull head. The rivet material is swaged into the hole and around the shank.

    Everything should be tested of course, but I am going to dimple and use flush pulled rivets. Of course driven rivets are stronger, but there is no reason you can't use more of the pulled flush rivets and achieve the same strength.

    There is no magic here. Just modify the rivet puller and make a few test samples. Make sure your strength is what you think it is. Otherwise use standard dimpled skin type construction. Make sure your test samples conform to strength requirements.

    If you are going to use the flush rivets in a non flush application, then just sending out your pull heads and using proven methods is easier...but not required.

    Making test samples if you don't follow a proven method is required.

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    Registered User stol's Avatar
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    Re: Blind rivet construction

    xxxx
    Last edited by stol; May 5th, 2012 at 07:46 PM.

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    Re: Blind rivet construction

    Getting optimum performance from "blind" rivets requires a much higher degree of accuracy in fabrication, particularly hole size. For certified aircraft use, I think the only way to reasonably achieve ordinary design levels is by reaming, i.e., a very precise operation, maintaining a good "vertical," no "wiggling" allowed.

    Us older gents will recall that John Thorp originally contemplated "pop-rivets" for the construction of the T-18 and some were assembled using these rivets, but "in service" difficulties quickly surfaced and I recall one in particular who disassembled to re-rivet with AN rivets. I visited and talked with the Heintz facility in California but, other than that, I do not have any recent exposure to the Heintz "approach". I do think that a builder who gets good training in the "care and feeding" of solid rivets doesn't gain that much convenience going the "blind" route. But, before you react negatively, this opinion contemplates attaining a bird with a 30+ yr service life.

    Onward and upward
    Marc Bourget

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    Re: Blind rivet construction

    Thanks for the insight gents!

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    Re: Blind rivet construction

    A word of caution...!
    Changing from "pop" type rivets to "flush" type rivet systems MAY change some of your low speed/stol handling characteristics.
    Button/domed head rivets have a tendancy to create a boundry layer turbulance that is similar in nature to the effect created by vortex generators. By flushing the rivets, & smoothing the wing surface, you may increase the high/top speed, but you also increase your landing/approach speed.

    I must note that this is information that I have read about & that I do not have any personal knowledge of this. YMMV

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