SonexBuilders.net

First off..........I'm not going to install a LRI unless mandated by the FAA. Period. I'm pretty well informed about how they are going to single-handedly save the planet, but I'm not going there.

What I do intend to install is an old-fashioned stall warning horn (think Cessna) that relies on suction from the leading edge to activate a reed-style horn. I've already tested the horn going down the road in the Buick and by using the wife's vacuum cleaner.

What I need to know is approximately where the stagnation point on the leading edge is during a wing stall. Has anybody "tufted" their leading edge to gather that info that they could share, or is it published somewhere?

Hiatus season is over here @ Area 51%

I also like the reed-style horns.

I believe locating it at the location of the stagnation point as determined by tuft testing would be wrong by an inch or so. The stagnation point is a high pressure area (just like the front of a pitot tube). That is where you would install the switch style sensor.

The point you really want is one that becomes low pressure relative to the cabin and is probably an inch or two ahead of the stagnation point. Probably close to but slightly below the leading edge.

Here's a video that shows the relation between pressure and flow streamlines.
https://www.youtube.com/watch?v=edZLT9eymIk

You could probably get close by copying the placement from another airplane, but the Sonex is different enough that I'm not sure you could do it without needing to adjust the placement slightly.

I wonder if you used the same location for your stall warning that Van's uses on their RV's? It would likely get your pretty close to where you need to be.

Just a thought...............

Gordon.....Onex.....Hummel 2400

You could build a test article and try out several locations. I'm envisioning a leading edge section like the Sonex Workshop project. This section could then be modified to hold the reed switch and held out the car window to gather some data on the airflow. It will be an approximation, but it will likely be a quick and easy way to develop a plan without access to a flying Sonex for tuft testing.

Jeff

I thought about the workshop leading edge, but there might be some influence from the rest of the wing that would require it's presence. In fact, I believe tufts might be required on the complete wing surface to show when the stall occurs to get placement of the port correct.

I also thought about using the area of the wing that is destined to have the landing light as a test-bed. It would require a flying airplane and a landing light that is retro-fittable to cover the hole left by the adjustable test port. I already have the conduit run. Are the landing lights that are available, such as Duckworks, set up to allow fitment on an assembled wing?

I'm also wondering if the airfoil (the number escapes me), as used on the Waiex, might already have that information available.

Keep the info coming to the uneducated here @ Area 51%.

You could take the Cessna air vent approach. A cover over a larger hole.

Does a Grumman Tiger have a stall horn? They have the same airfoil as a Sonex, maybe
you could copy it's position.

Rick
Sonex 524

Area 51% wrote: Are the landing lights that are available, such as Duckworks, set up to allow fitment on an assembled wing?

I installed duckworks lights while I was building my wings and while having the wingtip off definitely made it easier, I think you could install them on a completed wing. They definitely advertise that you can!

Yes you can install them on a finished wing. I have done it on 2 different RV's and it was not too hard a job. It IS easier to do it during assembly of the wing, mainly for routing the wiring.

Gordon......Onex....Hummel 2400

Conduits and other provisions have been built into the wing to accommodate any future lighting (except the lens cut-out) as well as the pneumatic line for the stall horn. So from where I stand, it appears, from what I've seen on build sites, if I have a surgeon add an extra wrist to my left arm, I should be able to install the landing/taxi light post-assembly?