As we get to the last of the flap repair (for this wing anyhow) I'm learning more skills that will come in handy later for my build.
So far, I've had the opportunity to work with blind "pop" rivets (the predominant style in the Zenair line of aircraft) and solid "bucked" rivets. Both have their place and use.
Last night I started working with flush rivets. Designed with a smooth flat top they too are bucked or squeezed to form a bond between two sheets of metal. The advantage these have however is that they leave the top surface smooth and thereby more aerodynamic. It also looks real cool! Most modern metal aircraft use this style for aerodynamic reasons. They are particularly handy around windows trim and landing gear plates where thickness tolerance of adjoining parts is important.
In the case of our flap repairs, we wanted to come up with a way to clean up the trailing edge and correct the ham-fisted attempts at a straight edge by the original builder. Ron made up a sleeve which will be flush riveted to the trailing edge.
It starts with marking out the rivet lines and drilling small #3 holes, the size of the rivet shank:
Next, the hole is very carefully countersunk with a bit in the cordless drill:, to a depth that matches the shoulder of the rivet. Holes for larger rivet are usually countersunk using a dimpling tool, but this tool works here:
Here is a picture of a typical flush rivet. Note the smooth flat top, angled shoulder and round shank:
Making the hole match the rivet so it lies flush is the goal here. Too shallow and the rivet won't lie flush, too deep and it can't hold the bond adequately enough nor be completely smooth on the surface:
Work a little at a time, test fit often and eventually the rivet will sit perfectly flush with the surface... smooth!:
Now repeat 30 times along the trailing edge :)
Ron and I flipped the wing over on the bench and I removed the damaged nose skin:
I know at this point I shouldn't be surprised by anything I find with this repair, but this was interesting. There was a "perfectly" blended rectangle, held in place by rivets and covered by the magic of cheap paint located at the back edge of the nose skin. It is hard to make out in the picture below but I really didn't notice until I took off the skin what it actually was, so I don't have a before picture.
Once the skin rivets were removed, and the damaged nose skin removed did the curious patch reveal itself, again nothing surprises me anymore:
My only guess is that this was some sort of Mickey Mouse access panel to get at the wing strut mounts, but I can't for the life of me figure out how anyone thought this was an acceptable patch..... jeebus.
On a happier note, I recently confirmed my attendance this fall at the Zenith Factory open house in Mexico Missouri. It's a two day drive from here, but most importantly William Wynne will be there demonstrating the build up of Corvair engines. As a bonus I'll be able to take my core items for assessment and perhaps send my heads away for rebuilding at the same time. Can't wait to atttend and learn even more!
Next up, more finishing work on the wing repair and prepping the bench for slat building.
Been a while since I posted, but the new job is taking up most of my days and weekends are escaping us because now the outdoor work around the house begins. Excuses aren't welcome, but the grass doesn't stop growing.
Much earlier in this blog (my first post actually - click here) I spoke of all the work my mentor Barry Morris and I put into trying to promote and develop the South River / Sundridge Airport. Unfortunately, Barry passed away before seeing the local municipalities get their acts together on this important community asset.
I honestly thought all was lost regarding the airport. Three times the municipality almost sold the property to non-aviation interests who wanted to turn it into a number of non-aviation purposes. How disheartening.... however....
I'm ecstatic to say the property was sold to a couple of business men that are enthusiastic aviation people who want to continue to develop the property PROPERLY as a municipal airport, including paving a runway and installing lighting. "Build it and they will come...." is a quote from the 1989 "Field of Dreams". How perfectly appropriate!
On the 12th of May, the new owners, in conjunction with COPA and the local flying club hosted a fly-in pancake breakfast. Ron, his wife Donna and I attended and joined the fun.
Over 40 aircraft from all over southern Ontario attended, it was wonderful! The new owner couldn't wipe the smile off his face! There are a bunch of photos on the airport Facebook page. I was way to busy chatting with friends to take a bunch of pictures but here are a few:
Of course one of the more interesting planes that arrived was a newly kit built Zenair 750 STOL, just like I'm building. Spoke at length with the owner who has about 80 hours on the airframe after completing it last year just south of us in Emsdale. The biggest thing he recommended was keep at it. There is a ton of stuff he still wants to do cosmetically (more paint, etc) but he's having way too much fun flying! He let me sit in it too and I'm even more convinced that I've made the right choice :)
The chance to see another completed 750 was a real good motivator!
The 701 flap repair is almost done. Some final trimming to be done, but the skin wrapped real nice and the joining patch turned out real smooth. Happy to be moving on to building my own flaps shortly and not fighting with other people's mistakes.
Ron has never been very happy with the pinched trailing edge design of the wings and flaps on the 701. The original builder (as I've been saying all along) never really paid attention and the trailing edge isn't nearly straight enough. The pinched rivets called for in the plans really add a lot of drag too.
The plans in the 750 model I'm building wraps the skins forward to the spar, making the trailing edge much cleaner both in appearance and more importantly aerodynamically. Every little bit helps!
To clean things up, we'll be adding a trailing edge strip and attach it with flush rivets. Here, we're fitting the trailing edge "cover". The first one worked real well, I'll add a picture when the one is done.
We plan on building flaps and slaps at the same time for three new 701's and my 750 and new slats for this repaired 701. This sounds like a ton of work and it is, but there are huge time savings because they are dimensionally the same, meaning we only have to set up jigs once.
I spent a couple of hours the other night bending my slat ribs on the forming block. The 750 slats are identical to the 701, so I didn't need to make my own forms for this. The only adjustment needed was one tooling hole on the tail end which is different:
So they turned out ok, but will need some clean up. Not a big deal, but not a nice as I would have liked.
Next up, finish skinning the 701 wing extension. Here is a graphic of what I have complete and ready to assemble (highlighted in blue). Lots of stuff ready to be bent still.
Thanks for reading :)
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Husband, father and 911 dispatcher. Long time pilot with a licence that burns a hole in my pocket where my student loan money used to be. First time aircraft builder. Looking to fly my own airplane.