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    Surface cracks in bent aluminum 6061-T6

    No alodining or anodization of the part prior to bending. I did polish, then bend, then polished again on a subsequent part. I also polished against the grain, if that makes a difference, until I could not see any surface cracking. it seems that bending aluminum angles is common for kits. As...
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    Surface cracks in bent aluminum 6061-T6

    Thanks for your thoughts. Yeah, bending angle without cracking seems to be quite difficult. It's in the plans and is the part that is at where the fuselage tapers into the tail cone. I did notice cracking and sought to polish the surface before to reduce nucleation sites, and afterwards to...
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    Surface cracks in bent aluminum 6061-T6

    Thanks for the replies. It would seem that the only way to guarantee the bend radius in the second method is to have a steel rod in the corner of the aluminum angle. You would have to clamp it in place to prevent it from squirting out. I would have thought it would have been unnecessary to have...
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    Surface cracks in bent aluminum 6061-T6

    Thanks for the feedback. The way I bent it was the second method shown in the EAA video (3:16) https://players.brightcove.net/627008079/7MKHE9SrL_default/index.html?videoId=35607276001 I'm not sure about bending around a rod in this case. Sorry for not being clear. Is the first method...
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    Surface cracks in bent aluminum 6061-T6

    Hello All, I bent some 1/8" aluminum angle (closing the 90 degree to something smaller) and noticed some cracking on the surface, using a vise to squeeze the ends together. It's a relatively small bend (from 90 to 86), so was surprised. I redid it to another piece and got the same result. I...
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    Screws vs Rivets

    So, that was my original thought as well, and it makes more sense to me than to replace with a 3/16 bolt or screw because the rivet will take load immediately, whereas the bolt will have to have some displacement of the sheets before it takes load (there has to be some clearance, otherwise the...
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    Screws vs Rivets

    Thanks all for the tips The rivet was supposed to be standard 1/8" pull type, stainless steel, protruding head for two 0.032" 6061T6 sheets. I made a hole with a #18 accidentally. There is a 3/16" hole right next to the oversized hole, and I was stepping up from the pilot hole to the final when...
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    Screws vs Rivets

    I overdrilled a rivet hole and tech support suggested I use a screw instead of a larger sized rivet. I'm trying to understand why that would be the case. Wouldn't you want to replace the rivet with a larger rivet? While the screw would support higher shear loads, the screw would only be loaded...
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    Firewall Forward max weight reasoning?

    Thanks very much. this is me mostly just trying to understand airframe design. I understand that controllability and structural integrity can be the limiting factor to FWF. It didn’t make much sense to me that FWF just be a weight limit in the case for structural limit. Rather, as you suggest...
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    Firewall Forward max weight reasoning?

    Thanks. I’ve had an opportunity to write Mark. He was kind enough to answer my questions, which I’m sure he’s been asked a million and one times before.
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    Firewall Forward max weight reasoning?

    Thanks very much. Definitely something you wouldn’t want to do without significant analyses and thought. Looking at a Sonex B aeromomentum Am15 combination. Very cool engine, but mostly trying to understand aircraft design more. I also wondered about vibratory loads and whether that factors...
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    Firewall Forward max weight reasoning?

    I’m trying to understand what drives the maximum firewall forward weight. Since the Engine is cantilevered, I am assuming that one component is simply the stress on the engine mount. If this is the case, then an airframe max g could be derated. Another factor is elevator control authority. This...
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    Bolt holes, burr and fatigue life effects

    Thanks for everyone's input. My brain is slowly "grokking." Just trying to build the right model in my brain so all the factoids I pick up fit together. Interestingly, I learned as I read through materials that while differences in clearance may affect how much load a particular bolt takes...
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    New EAA Chapter Build Project SoCal

    That's awesome! At EAA20, there is a fairly robust, kid focused programming. EAA20 also just did first flight for the club built RV-12
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    Does your auto-conversion airplane have over 500 hrs TT?

    Always enjoy seeing the statistics that Ron presents and the discussions afterwards
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