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    Drilling straight holes...

    I'm building a sonex. I have a situation where I am trying to expand a hole from the #40 pilot to 3/16". I drill out to 5/32" with a guide in place. Following the directions (page SNB-W08), I now mate another piece of aluminum angle, which now prevents me from using the drill guide. The surfaces...
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    Noise reduction methods

    I've been reading about articles about how for delivery drones and EVTOLs to see widespread use, they need to address how noisy they are. Trying to think of ways to make them quieter. Reducing propeller speed is probably the biggest. I would imagine that would mean more blades for a given...
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    DARPA Research Announcement for Platform Design Optimization Leveraging Power Beaming

    Hi All, Found this call for proposal to look at how design methods might change as a result of using beamed power. Text of announcement is below. I always like hearing how a new tech might change the design process. The range and endurance equations will obviously have to be modified. What other...
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    BD4 Performance specs

    I've started looking for the next kit, and came across the BD4C. It seems to have really good numbers, even if it wasn't a 60 year old design I'm trying to understand what the reasoning is. It's got a higher wing loading than an RV-10, yet still lands and takeoff in comporable distances...
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    Substitute phenolic with delrin?

    Not sure if this is the best subforum, but here it goes! I have a rudder pedal mount that I need to fabricate. The rudder pedal rotates between two peices bolted together. Plans call for fabricating it our of phenolic, but I want to use delrin instead because: I have some lying around Aircraft...
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    Thin sheet hole matching

    Hi All, Here's my scenario: I'm trying to match drill a thin sheet of aluminum (0.03) that is already at final hole size. The holes are on the top piece. If the top piece was thicker, I could use a hole transfer punch if the material was thicker (like 1/8"), but at 0.03", it's too thin and...
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    Backside rivet removal?

    I have a situation where I have easier access to the backside of the countersink Pop steel rivet than the blind side and want to remove it. Any suggestions? I think I need to first remove the mandrel somehow, then the expanded part, before I’m able to tap out the rivet. Surely someone has to...
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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

    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?

    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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    Do extrusions (non cut side) need to be polished?

    I was reading through the Zenith construction standards and there was a mention of the need to remove all cutting marks as they may be stress risers. That makes sense to me. I wouldn't consider extrusion surfaces to be smooth. They often have lines that show the direction of extrusion. Do these...
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    Bolt holes, burr and fatigue life effects

    I've been told that not properly deburring can lead to decreased fatigue life in a bolt hole. I'm trying to go through the mental exercise of how burrs affect the fatigue life on a joint. Haven't found a good explanation yet on the internet. I understand how a crack that is cyclically loaded may...
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    Spinning and unremoveable nylock. Any tips?

    Hello All, I've got an An3 bolt with an nylock nut that I was attempting to tighten on some metal parts. For some reason, I couldn't achieve the appropriate tension. When I tried to remove, I noticed the nut would spin, but not descend down the thread. Yes, I held the bolt stationary. I'm...
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    Where to buy pre-bent stock aluminum sheet metal?

    Looking to purchase some prebent 0.032" and 0.025" 6061 Aluminum C channel. It seems like it would be a common thing, but can't seem to find a source. I tried Aircraft spruce, Wicks, but no luck. Thanks!
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    Repair of compromised Longeron

    Hello All, I'm the proud owner of a new Sonex. Unfortunately, there are some issues with the previous owner's work. In a few instances, he redrilled holes next to others and near edges, seriously compromising the structural integrity of the piece (in this case, horizontal stabilizer spar)...
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    Joining Composite Tubes

    Hi All, I'm looking to build a truss structure from fiberglass tubes. I haven't seen a lot on how to join pieces together. Most of the stuff I have seen is about extending a tube using an insert. In Solidworks, one can miter a joint to make them fit well together. My current thoughts is to do...
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    Match hole mismatch

    We've started putting together a RV-12 kit, which has match drill holes that we drill to final size. When we assemble pieces together, we sometime note slight misalignments that doesn't hinder a cleco going in, but prevents a pop rivet from fitting in the hole. We've been taking a drill bit and...
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