DIY Lift Reserve Indicator

I have completely forgot to tell you about my Lift Reserve Indicator project. 

For reasons that we don’t need to repeat I have gained a particular interest in the stall point at landing... 

A traditional angle of attack meter is complex and expensive (and feels like overkill for an ultralight aircraft) but I found a number of articles on the web talking about  “Lift Reserve Indicator” (here is one, here is another, and you will find many others as well as "for and against discussions" doing a simple search…). 

While producing very much the same information as a traditional AOA indicator it is just a differential pressure gauge connected to a probe with forward and aft ports - and therefore at a fraction of the price and easy to do yourself... 

I got a 0-2.0" WC Dwyer pressure gauge from Amazon (but there is obvious other sources) and made a new gauge face using a inkjet printer... Inspired by the Icon Aircraft Lift Reserve Indicator I added a wing profile to the needle. It will make it more readable by the corner of the eye... 

The probe is an aluminum bar, (1 cm by 2 cm) as long I could drill (some 13 centimeters). It is mounted approximately at ~20% of the wing chord counted from the leading edge and leaning forward. The angle need to be refined in test flights to confirm the correct reading.  

If it works? I don’t know... but be sure I will tell you about it here once I have tested it in flight…

A productive weekend

A major step in the reconstruction has been completed, both wings are now covered and finished (when using ORATEX that is actually a tautology…).

To document his major step I made what is probably my most boring film. And to make a boring film worse I forgot to lock the auto focus so with a big white object in the center of the frame the image is sometimes flickering… very annoying.

So, unless you are seriously considering using ORATEX for your air craft project you will have much more fun watching any of my other films.

Covering the wings

I have started covering the wings and have just completed the left wing. 

The Avid Flyer wings are complicate to cover.The flaperon hinges are sticking out through the fabric as extended spars, the trailing edge is a wire and the only surface for gluing is the leading edge tube.

With the widest Oratex UL600 being 1800 mm it can not wrap the entire wing. I opted for pre assembling 2 sheets of fabric, one 1800 mm and one 900 mm, with a 15 cm overlap to make a wide enough sheet before attaching it to the wing structure.

The overlap by the trailing edge is glued (and the glue activated!) before covering the wing.

I cut holes for the flaperon attachments and had to start by covering the first 2/3 of both sides of the wing at the same time. The bottom sheet was glued to the leading edge tube, wrapping around it, and the top sheet then goes on top of it and an additional 10 cm behind the leading edge glued to the bottom sheet. The fabric is obviously also glued to the 1 inch wide cap strip of each spars (and the entire surface of the wing tanks).

A 2 piece reinforcement were added where the flaperon attachments goes through the fabric.

To make covering the first wing more challenging I also have the pitot tube, LRI probe and a trap door for a USB cable on the left wing. The red and black cable is in view of a future - eventual - wing tip strobe.  

With overlapping sheets that therefore need additional glue you have to add time for the glue drying but it is not difficult to finish a wing on a weekend. And when I say finish I mean it. No layers of paint to be applied.

I used 1400 grams of fabric (including the glue on the fabric) for the left wing. This means that even including the glue on the structure covering both wings will only add around 3 kg.

The right wing is ready to be covered but I'm out of glue at the moment so I'm doing the wing strut fairings at the moment...