SonexBuilders.net

If you built the exact same model all over again, what would you do differently?

In fact....I am building the exact same model again.
This time around I'm installing the trike main gear trunnions, even though the plan calls for another tail-wheel bird.
The option to be able to convert was my wife's idea, as she doesn't hold a tail-wheel endorsement. It may also be a selling point when that time comes around.

I'm pretty happy with how mine turned out. Anything I'd do would be for weight reduction. Randy's reported weight savings for his aluminum tank was pretty interesting. I'd also consider making my own titanium firewall. No way would I put VOR navigation capability in again. Definitely tap the case for full flow during the build.

Stuff I did differently that I would definitely repeat:
1) John Deere voltage regulator
2) Gene Berg pressure limiting oil pump cover
3) mechanical master switch
4) additional seat structure (for the A model)

Bryan is Gene Berg the William Wynn of VW engines?

Most of my decisions were around cost so there is plenty I would have done if money wasn’t an issue. First I would have bought the kit instead of scratch building. I would have saved years off the build although scratch building was a lot of fun. Second I would have put a Corvair motor in it instead of the VW. I think the Corvair is finally developed enough now for the Sonex and hits the sweet spot between cost and power. I considered switching over but since my plane is already built the cost of the Corvair motor, new engine mount, new gear legs, and a new cowl that would need to be painted to match the existing 3 color paint job was just too much. Instead I rebuilt my aerovee with a force 1 prop hub and bearing and am working on putting in a bigger alternator and fuel injection system on it as well as a number of other minor tweaks. Airframe wise I would have gone with a panel mounted radio instead of the icon handheld I had hooked to an external antenna and the intercom. There isn’t much else I would have changed on the airframe other than maybe move the headset jacks from below the panel to behind you on the no 1 turtledeck rib.

Keith
#554

BobDz wrote:Bryan is Gene Berg the William Wynn of VW engines?

Bob,
Not really. More of a dune buggy guy I think.
http://www.geneberg.com/product_info.ph ... cts_id=320

I forgot one really big thing I'd do differently. Make the back of the instrument panel accessible somehow. Either make it held on by hinges as some have done, or screws or something.

If I need to make a major panel mod at this point, it would be easier to build another airplane.

I have been putting this off for at least a decade, telling myself each winter that now is the time! For during the build (Sonex A #0525 tok to the air for the first time in may 2005) I specifically asked Kerry if the instrument panel/glare shield was structural. His reply prompted me not to mess with it, but to stick to the drawings. With the benefit of hindsight and countless hours of cursing because of restricted access, I wish I had stuck to my hunch and made everything behind the panel much more accessible. Hinge the panel, make the glare shield top detachable- things like that. Another thing that comes to mind is that the structure under the sheet seat is not sufficiently rigid. Of course, it is fine for flight, but getting in and out of the plane, performing service, repairs, and maintenance, etc (i.e standing in the seat for any reason) wears the old structure down fairly rapidly: I understand that the B model is much better here.

Kai wrote:I specifically asked Kerry if the instrument panel/glare shield was structural. His reply prompted me not to mess with it, but to stick to the drawings. With the benefit of hindsight and countless hours of cursing because of restricted access, I wish I had stuck to my hunch and made everything behind the panel much more accessible. Hinge the panel, make the glare shield top detachable- things like that.

I didn't design the airplane obviously, and I'm a mechanical, not an aeronautical or structural engineer, but IMHO, both the instrument panel and the glare shield are structural. The complete the "tube" of the front of the fuselage, and provide torsional stiffness in that are. And they work together - the instrument panel stabilizes the glare shield.

Having said that, my airplane has some changes, instigated by prior builders, that are worth discussing. My glare shield is fastened with machine screws in tapped holes in the longerons. It's still riveted to the firewall, but I have FEWER rivets to drill if I have to pull the tank, which I've already done once.

My panel is modified as well. The avionics professionals that did my panel elected to put an extension on the glare shield, and use a VERTICAL panel, fastened to the vertical stiffeners at the forward edge of the cockpit and to the extended glare shield with nutplates. I can pull the panel, a little bit. The nicely installed, Tefzel wired and laced harness keeps me from pulling it out completely, but I can access the back of most of my avionics with a minimum of Technical Terms.

I've lost confidence in the glare shield attachment though, and I'm thinking about replacing the machine screws with up-sized ALUMINUM rivets with mechanical properties comparable to the Stainless rivets of the plans. I HATE drilling stainless rivets, even though I have the whiz bang tool for drilling pulled rivets.

Kai wrote:Another thing that comes to mind is that the structure under the sheet seat is not sufficiently rigid. Of course, it is fine for flight, but getting in and out of the plane, performing service, repairs, and maintenance, etc (i.e standing in the seat for any reason) wears the old structure down fairly rapidly: I understand that the B model is much better here.

There is a plans revision to the A-model that beefs up the structure in that area, but I think it's for the cross member for the aft spar, and not for the seat support itself. My plane hasn't flown yet, and I haven't put the seat back in it - I have two wooden novelties I've made up, one is a seat complete with piano hinge and back, and the other is a work platform that carefully bears on the main spar and the seat support that I'm using while I finish things up. I concur that either up-gauging the seat support formed angle or adding a doubler, say, a strip of .063, to the flange, under the piano hinge, might be a good idea.