Extruded spar/leading edge

[1934A]

While checking out the specs on the Rans S21, I saw that the front spar and leading edge is a single aluminum extrusion. Maybe this had been done before, but this is the first time I've seen it. Looks to make for a very stout leading edge, and it would simplify the build process.

[courierguy]

As a 20+ year, 2 different S-7's RANS flier/builder, I can tell you Randy Schlitter, their Grand Poobah, is one of those smart guys who knows how to keep things simple as possible while still getting the job done. Some smart guys like to make things more complicated than needed, to show off how smart they are. How many other kit plane companies have been around for 30 years (more I think) with continuous ownership? VANS comes to mind, that's it. While the gofast side by side 21 doesn't push my buttons, as a tandem goslow pilot, there has been some buzz about adapting the 21's wing type to the S-7 line, with a bit more spare/square feet. But, the 21 is stealing all the time and energy of the company, so nothing yet. I'd love to hang my rag wings on the wall as spares, and try out that spar.

[1934A]

I don't have any firsthand experience with Rans, but I've always liked the looks of their kits. The S21 looks like it would be a fun, affordable build that sort've fills a niche. I kind of look at it as a C180 Lite, I guess.

If someone was to build the extrusion dies, why wouldn't this leading edge/spar work on a cub wing? Seems like it would sure simplify a wing build.

[skywagon8a]

Since they had to pay for the extrusion tooling anyway, I wonder why they did not extend the splice joint on the lower surface as they did on the upper. It sure would be easier to drive the rivets. As they did it, blind rivets are mandatory. Some of us prefer driven rivets.

[JimParker256]

Since they had to pay for the extrusion tooling anyway, I wonder why they did not extend the splice joint on the lower surface as they did on the upper. It sure would be easier to drive the rivets. As they did it, blind rivets are mandatory. Some of us prefer driven rivets.

I believe the rivet line you are seeing is where the aluminum skin attaches to the spar extrusion, not the splice joint itself... The leading edge "D-extrusion" is a single, solid piece.

As for the "driven rivets" versus "blind rivets" argument: Both work equally well, when properly engineered and installed. Spacing, sizing, and composition may differ depending on the type of stress load being countered.

The one unassailable argument in favor of driven rivets is the cleaner aerodynamics of flush rivets. On the other hand, the arguments in favor of pulled rivets include the "One Week Wonder" airplanes built during AirVenture... It's just a LOT faster to pull rivets than it is to drive them.

[OzAK]

The extrusion question certainly isn’t a new one though it’s interesting to see the Rans version on a wing sized scale.
It’s been at least 30 years I’d say since Earnie Heald started D&E Aircraft, originally in the Pacific Northwest. He was a big proponent of extrusions among other things.
Now located in Florida and under different but very helpful (in my experience) ownership, they still offer some extrusion based parts, such as this, a cross section of the aileron/flap extrusion available in 10’ lengths. With ribs and trailing edge attached, it becomes a complete part without needing a full spar web, very stout. They are part of D& Es Riblett GA 30613.5 56”, 63” and 66” airfoil offerings among others.
Just thought you might find this interesting.

Oz


Sent from my iPhone using SuperCub.Org mobile app

[skywagon8a]

I believe the rivet line you are seeing is where the aluminum skin attaches to the spar extrusion, not the splice joint itself... The leading edge "D-extrusion" is a single, solid piece.

I see two locations where a skin attaches to the "D" extrusion. The upper skin attaches to a strip aft of the "D" section which is part of the extrusion.
The lower skin is blind riveted to the "D" without the advantage of the extended strip. It is the lack of the lower extended strip I question.

As for the "driven rivets" versus "blind rivets" argument: Both work equally well, when properly engineered and installed. Spacing, sizing, and composition may differ depending on the type of stress load being countered.

I don't question the structural strength of the blind rivets. It has been my observation that blind rivets have a tendency to loosen in areas which are subject to certain vibration scenarios. Driven rivets not so much in similar situations.

The one unassailable argument in favor of driven rivets is the cleaner aerodynamics of flush rivets. On the other hand, the arguments in favor of pulled rivets include the "One Week Wonder" airplanes built during AirVenture... It's just a LOT faster to pull rivets than it is to drive them.

Blind flush rivets are available. As far as speed is concerned.... it would depend on who is doing the pulling or driving. Driven rivets are lower cost.

This extrusion has the extended tab for driven rivets top and bottom.