Sonex Onex – addaon – Bay Area, CA

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addaon

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Greetings! Some of you may remember me from days of yore on this forum. Real life has been taking an uncomfortable amount of time, as it is wont to do.

But on Tuesday, I will be taking possession of a brand new Sonex Onex kit. Doing it the lazy way, with the machined angle kit and pre-assembled main wing spars. Engine is undecided, but likely to be an Aerovee, because support is nice.

The kit will be going into a messy, rented two-car garage in East Palo Alto. Since I haven't even thought about what I'll need for the shop yet, I'm not putting any schedule on completion -- or even, really, on starting.

I encourage local forum members or those visiting the neighborhood to stop by and say hello. Many hands make light work, and chatting about a shared interest is always great.

PM me for more info; if you kick off another thread, PM me to let me know, since I'm not nearly as good as I should be on monitoring the forum.
 

addaon

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Set up some Home Depot shelving, work lights, etc. Officially started opening boxes. So far just put the tires/tubes on a shelf, looked over the plans, and located the packing list... but officially ready for inventory to begin! 1.0 hour, w/ Cynthia Yeung.

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addaon

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The start of a project is never exciting, but documentation has value. On Saturday (2/8), I spent four hours starting to inventory the kit. Boxes 1, 3, 9, and 10 were easy, so I got those out of the way. Most of the time was spent on Box 4. After a quick stop at Home Depot to get some cheap stacking plastic boxes for small parts, Box 4 is mostly done. I have questions out to Sonex about a few issues: A single part is missing (ONX-C03-11), some part numbers are confusing (M-ONX-C02-10 in packing list, ONX-C02-10 on part), and the flash on laser cut parts is really nasty at times. Still, forward progress! Estimate ~4 hours remaining for full inventory, not including figuring out how to get rid of this much cardboard and packing paper.

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addaon

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Inventory done, or as much as it will be for now. No new issues found. Next steps: Cleaning up and setting up a work area. 2.0 hour, w/ David Geisert.
 

addaon

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Thursday: Dealing with cardboard boxes. This is become a theme. 0.5 hour.

Sunday: Got the palette up on sawhorses as a table -- it'll do for now. Need to grab some MDF as a surface so I can drill on it safely without taking all the sheet out of it. Decided on the first build step, which will be the rudder. Got sorted out for page T09. Realized that the hinge isn't part of the kit, as it's considered standard hardware. Fair, but unexpected. Aircraft Spruce does a "sonex hardware kit" that includes everything needed, but is perpetually back-ordered because some part of it always will be. Ordering the hardware separately (which is easy to do from the kit description, thankfully) lets you see what's backordered; so the hinge is on the way. Also ordered tools, clecos, etc from Aircraft Spruce in a separate order. Goal is to build the rudder next weekend. 1.0 hour, w/ Andrew Sakai.

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addaon

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Spent some time this weekend. Page T-09 done, which meant getting basically all my tools up and running. First holes drilled, debarred, and riveted. No photos today – phone battery died. Page T-08 up next. Need to figure out how I'm going to bend the thick plate for one part, and need to figure out what the story is with T-08-17, which is listed on the page but not (as far as I can tell) drawn. 6.0 hour, approx.
 
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addaon

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Reply on T-08-17:
Sonex said:
That is an error in the plans and we will get it corrected. There is no ONX-T06-17.
(I assume the T-06-17 and T-08-17 is just further confusion.)
 

addaon

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Last Thursday, I allocated an hour to finishing up page T-08. The only remaining job was to bend the plate for the vertical tail spar attachment. I decided to take the arbor press approach, as described in detail in an EAA video.

It went... less well than that video would suggest. Turns out a one ton arbor press with a 20:1 mechanical advantage isn't quite enough. That is one tough plate! Need to find more mechanical advantage and try again. 1.0 hour, w/ Cynthia Yeung & Jeff Miller.

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addaon

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Lots of progress to report.

Last Thursday, 3/13. Returned to bending the vertical tail spar attachment. I mentioned last time that I needed more mechanical advantage. Recall that the approach here was to use an arbor press to push the plate into a notch cut in a piece of scrap wood, bending it. Obviously (not too obviously, since I didn't think of it the first time), the mechanical advantage here is related to the distance between the sides of the notch. So I cut the notched wood at the bottom of the notch and screwed it, with some space between the halves, onto another piece of scrap, effectively widening the notch. This approach worked great, and a bit of strength got the bend to ~37°. Unfortunately, with the half-inch-thick scrap I was using, bending bottomed out at that point. I moved the halves closer together, expecting difficulty to still stay high, but apparently overestimated, as the bend quickly got to 42.4°, more than the targeted 40.2°. I expect unbending a couple of degrees to be pretty straight-forward, but am waiting for final fitting, as it's not clear what accuracy is required here. Page T-08 finished. Started on page T-07, which consists of two spar assemblies. The forward assembly, which uses the vertical tail spar attachment just bent, was straightforward; so got that out of the way. 1.0 hour, w/ Andrew Sakai and David Geisert.

Sunday, 3/16. Looked at what it would take to finish page T-07; the remaining task was assembling the main spar. This was the first part I've encountered to use bolts. I had ordered the Onex hardware kit from Aircraft Spruce, but not yet inventoried it, so I had a large box of assorted nuts, bolts, and other bits. A short trip to Home Depot got a set of hanging containers, which mounted up nicely. Sorted and labeled everything, should save lots of time going forward. 1.0 hour, w/ Andrew Sakai.

Yesterday, 3/18. Assembled the vertical tail main spar, finishing page T-07. Bolts not yet in place (chuck reamers just arrived today), but parts that will be bolted are drilled out to a #21 and cleco'd in place. Flipped over to page T-06, final assembly of vertical tail and rudder. Recall that I deferred drilling the skin on the rudder and assembling it, because I wanted to get the vertical tail assembled first to fit the rudder against it before committing to the exact hinge position. In that vein, I cleco'd together the frame of the vertical tail and cleco'd on the skin, confirming that everything fits nicely. A possible exception is the fiberglass tail tip, which looks like it's going to take quite a bit of trimming -- question out to Sonex. 3.0 hour, alone.

The next step is to rivet and bolt the frame of the vertical tail. At that point, I can either finish the vertical tail (riveting the skins), or re-cleco the skin there and use it for fitting the rudder, moving on to finishing up the rudder. No strong opinion at this point, but likely to move back to the rudder for the sake of variety.

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addaon

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I received the following question by PM, and thought I'd answer it here in case others might be interested.

skier said:
What made you choose the Onex over the Sonex? As far as I can tell, there isn't a huge difference in price, they use the same engine, they're both LSA elligible, etc. While I like (and would love to own) a single place aircraft, it doesn't seem there's enough of a difference between the Onex and Sonex to justify giving up a seat. I'd be curious the hear what led you to your decision.
The Onex vs. the Sonex brings up a bunch of issues. In my case, cost was not a primary driver, nor was LSA compatibility. Here are some of the things I thought about:

• I'm a big guy. The Sonex is a small two-seater. I can fit into it with someone else (and will, for training), but not comfortably. If I were to build a Sonex, it would be in the Sport Acro (center seat) configuration, and I'd probably fly it that way 95% of the time. Because of this, the Onex and the Sonex are approximately equal in utility to me.

• This probably isn't my last plane. I'm seriously considering buying something to fly while building; and whether or not I do, I strongly suspect I'll build another plane in the future. Since my second plane is likely to be a four or five seater, I'll be able to take up a friend in that; the second seat in the Sonex has even lower value in this case.

• The Onex is a noticeably newer design, and Sonex as a company has continued to learn over time. The Onex kit itself is noticeably more polished - more parts are pre-cut, more parts are match-hole drilled, etc. There's a little bit of everything left to do in the kit (control surface skins aren't match-hole drilled, for example), so I feel like I'll learn just as much from the Onex kit as I would from the Sonex; but it'll go a bit faster, I'll screw up fewer times, and I'll be happier with the end result.

• The folding wings are cool. I don't actually need them, since I'm likely to store the aircraft at the airport anyway, but I'm more than willing to reward great design by putting my money behind it, and I think that getting a good folding wing design into the kit space is a big deal.

• The Onex has that overbuilt feel that is really reassuring when thinking about flying something you put together yourself. It's ~85% the scale of the Sonex, and ~100% of the weight; it feels like there's a lot of margin in the design, and the gap between cruise (~135 mph) and Vne (~216 mph) really reinforces this. The Sonex is a solid, aerobatic design; but the Onex just feels like it's going to forgive a huge number of mistakes. And I'm pretty sure I'll make those mistakes eventually!
 

addaon

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On Friday, decided to push ahead on the rudder. Got the ribs and skins drilled to #40, and everything cleco'd together. Hung it off the vertical tail to check fit; looks good! Need to open up to #31, de-burr, and rivet, then the rudder is ready for flight. 3.0 hours, alone.

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addaon

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Yesterday, mostly finished up the rudder. Up-drilled, deburred, riveted. Deburring is by far the slowest part of this process for me.

All went well, until the very last rivet. It set poorly, with the mandrel sticking out significantly. I decided to drill it out as practice drilling out pull rivets; turns out it's **** hard to drill out a rivet with a protruding mandrel when you can't knock the mandrel out. Did a crappy job of it, proving that I really did need the practice, and enlarged the hole significantly (as well as somehow scuffing the surrounding area a bit). Asked Sonex for advice. They provided two options: Go up a rivet size (difficult because CCP-52s aren't readily available; they suggest using a Cherry Q instead of a Cherry N), or use a "rivet washer" to get the rivet to grab properly. Since I doubt this will be the last mistake I make, I sourced some off-brand CCP-52 equivalents, and will be using them in here and as needed.

Rudder complete, modulo a single rivet. 2.0 hours, just me.

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