#experimentalaviation — Public Fediverse posts

Like most GA aircraft, my plane has a very loud interior. Whenever I fly, my watch fairly constantly warns me about excessive noise levels. Usually 95 db, occasionally I see 100 db. Noise cancelling headsets are basically required to be in the aircraft while the engine's running. But even then, the noise is still noticeable.

Searching on the vansairforce forums (<3 old school forums), it seems that a lot of the cause of excessive cabin noise is basically panels vibrating against each other, and adding soundproofing material (tape, foam, etc.) helps to massively reduce the noise. The problem then becomes an optimization problem of where to apply the soundproofing to maximize effect while minimizing weight.

I'm thinking of taping a bunch of cheap mics to various spots in the airplane, recording the sound amplitude to try to figure this out. I'm hoping to be able to achieve a noticeable decrease in sound levels doing this.

Of course, I'll also decrease sound levels by just adding carpet to various panels, which I want to do anyway (my cabin is spartan). But I also want to see what the combined improvement will be.

#avgeek #aviation #ExperimentalAviation #homebuilt

My friend @cyanoacry (much more active on bluesky, @cyanoacry.bluesky.social) has a blog about the kinds of thing he gets up to with his Rutan Defiant. Yesterday, he posted a highlights of 2025, which included 2 live streams while flying! Plenty of people record and publish their flights after the fact, not that many livestream them!

https://cyanoacry.substack.com/p/defiant-hijinks-dec-2025-part-2

#avgeek #aviation #ExperimentalAviation #homebuilt

Aircraft and glider transponder codes - FAA gotcha.

I have not yet received my glider registration from the FAA (any day now, lol!), but they have assigned a transponder code for the N-number I have reserved. (see first screenshot)

To configure my avionics, I need to load this transponder code into the device.

FLARM wants it as a 24-bit hexadecimal value. (Each hexadecimal value is 4 bits in binary...so it's going to be a six-character code...but my code is not six characters.)

Hmmmm, that number the FAA gave me just doesn't seem correct.

I then called up a known, long-registered aircraft to compare their transponder code. (2nd screenshot)

Surprise! The transponder code I was given was in octal, but not labeled as such. OK, convert to hexadecimal and now everything makes sense.

Onward!

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Avionics #Electronics #Transponder #Octal #Hexadecimal #Gotcha #FAA

For some glider fabrication jobs, I want the epoxy to cure faster...so I heat it in the microwave.

Seven seconds, mix it to even out local hot spots, seven more seconds, mix again...then apply. (For a small batch...approx 20 grams.)

I think the microwave radiation doesn't merely warm the epoxy. I think it somehow also accelerates (far more than a few seconds of warming would) the curing chemical reactions.

I only do this for epoxy jobs that are NOT structurally critical.

https://en.wikipedia.org/wiki/Epoxy

https://en.wikipedia.org/wiki/Microwave

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Epoxy #Chemistry #Microwaves #Physics

Glider flight controls. How does the control stick make the ailerons work? (And what about those flaperons?)

The video is in three sections. (Sorry about the abrupt jump cut edits.) First section shows the control stick moved side-to-side to move the ailerons. That motion is carried by various push-pull tubes and bellcranks...aft of the landing gear. In the second section of the video we see the lever for one wing goes up while the other goes down.

But I have flaperons, not ailerons. The third section shows the result of moving the flap lever...the same wing control levers now move up together, or down together.

The mechanical mixer allows two different control inputs (control stick sideways motion, and flap lever) to be combined into one final motion.

https://en.wikipedia.org/wiki/Flaperon

https://en.wikipedia.org/wiki/Bellcrank

This completes what was started here:
https://universeodon.com/@KrajciTom/114846515361228698

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Control #Flaps #Flaperon

The second step to improving the aerodynamics of the glider's external 'shark fin' antennae...add fillets to the mounting base.

This reduces interference drag.

After the low density filler cures (epoxy resin with glass microspheres mixed in), I'll sand things smooth. (The piece of wood is covered with transparent packing tape that was lightly waxed. The antennae should come off easily.)

This is a follow-on to:
https://universeodon.com/@KrajciTom/114836322219112991

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Aerodynamics #Antenna #Fillet

The glider's landing gear brake has been successfully bled of air bubbles. Brake lever action feels firm and stiff, not spongy. No leaks noted anywhere. I feel good about initial tests of the brake when the glider is next assembled.

1st photo - overall configuration. The bleed tube is on the left side and leads to a jar in which to collect excess brake fluid. The actual brake line is on the right, and quite thin. The orange color is outer tubing that serves as a scuff/wear protector.

2nd photo - fill the brake master cylinder reservoir with brake fluid, and keep filling it as you bleed out the air.

3rd photo - transparent/translucent tubing lets you see what is happening with the brake fluid.

4th photo - one of many bubbles that escaped as I filled the system with fluid.

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Brakes #Wheels #LandingGear #Bleed #Bubble

Before the glider landing gear gets reassembled, I riveted new brake pads to replace the old ones.

Then I practiced a couple times to determine a workable assembly sequence that required the minimum of wrestling, fuss, and need for a third and fourth hand.

Now I can add brake fluid and bleed out the air bubbles.

This brake is supposed to have enough stopping power that I can inadvertently tip the fuselage and scrape the nose if I brake too hard. (It's no fun to do that...especially if you have an audience.)

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Brakes #Wheels #LandingGear #Rivet

Assembling parts of the glider flight control linkages in tight places.

1st photo - if only every job were this simple! Room to get both hands in, visibility, room to turn wrenches, etc. That's more the exception than the rule.

2nd photo - looking into the landing gear box through a hole that's large enough for one arm/hand. At the far end, where the bulkhead walls and fuselage converge into a tight corner...and where there are plenty of parts already installed...I need to connect another push-pull tube. I can only get one hand in there, there is barely enough room to insert the bolt, I'm working only by feel, and I also need to start the nut and tighten it.

What to do?

3rd - bolt the rod end outside the landing gear box, insert through a hole, then spin the rod end into its threaded socket.

4th - there is only room for a half wrench to tighten the jamb nut.

Whew!

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Collision #Bolt #Clearance

Collision detected!

Now that most of the glider's flight control linkages have been bolted, I'm starting to check for conflicts, rubbing, bumping, etc. Some places have multiple moving parts in very cramped quarters, or moving parts that come very close to stationary parts such as bulkheads..

This video shows one collision. (It's in the 'mixer' section of the flight control linkages, in the fuselage just behind the landing gear.)

Fortunately, this one is easy to fix...swap the bolt and nut on one part.

There is much more checking to be done throughout the glider....

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Collision #Bolt #Clearance

How fast does brake fluid dissolve certain tubing?

I have read that DOT 3 brake fluid will dissolve vinyl tubing, so I won't use it in my brake system.

But how fast does vinyl tubing dissolve in DOT 3? A couple days ago I put a piece of vinyl tubing in brake fluid. I also put a piece of Tygon tubing in fluid...as a control/comparison.

So far the vinyl has not turned into a pile of goo. Perhaps it's gotten a bit softer, but only a bit.

I'll run this experiment a bit longer, but not as long as the famous Pitch Drop Experiment:
https://en.wikipedia.org/wiki/Pitch_drop_experiment

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Brakes #BrakeFluid #Dissolve #Vinyl #Tygon #Nylon #Science #Experiment #Control

I have to take apart the glider's wheel brake piston to swap out the O-ring.

Why? Because I want to use a different brake fluid (that also works with the master cylinder), and the existing O-ring will get soft and dissolve with the new brake fluid.

I cleaned up the sides of the aluminum piston with a scotch Brite pad...and then realized that I can do a better job on surface quality without too much effort.

Wet sanding, starting with 400 grit to remove wear and tool marks...ending with Brasso metal polish and a Dremel and felt polishing pad...and it's a mirror finish.

Now I can reassemble with the new O-ring.

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Brakes #Polish #Piston #Aluminum

As I perform final assembly of various glider parts (landing gear, flight controls, etc.) I am replacing many temporary/keeper parts, such as nuts, and some bolts. (see photo)

The many silver-colored nuts (zinc plated) are ordinary hardware store parts. They are not locknuts.

The few gold colored nuts (cadmium plated?) have a small rounded top where a nylon insert has been added. These are nylon lock nuts...nylocks. Those are the parts I want for most final assembly tasks. (Landing gear locknuts will use cotter pins or safety wire. They withstand greater shock loads and nylocks are insufficient.)

Note that some of the bolts in the photo are threaded along the entire length. Those are not suitable for connecting parts that are subject to shear loads. Instead, you want a bolt with a smooth shank. I am checking every bolt to make sure I have the correct shank length.)

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Procedures #Nuts #Bolts

Do the rudder and elevator interfere with each other at the extremes of their movement?

I think I have a little bit more sanding to do because I was able to increase the rudder deflection a little bit. Now it can get very close to the elevator.

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Drag #Aerodynamics #CarbonFiber #Rudder #Elevator #Interference

What size mylar strip do I need to cover the various control surface gaps?

This is the elevator, full down position. I need a 30mm wide mylar strip to cover it.

The mylar strip will be cut to length and taped in place.

The rudder and flaperons may need different width mylar strips.

All of this drag reduction should boost my cruising speed by 0.01 knots.

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Drag #Aerodynamics #Slick #CarbonFiber

The glider fuselage has been wet sanded.

It's time to for final buffing.

I did some experimenting this morning to get a feel for process and especially process control.

I had two different polishing pads. Would they give different finish quality?

Would a grid of black Sharpie help me keep track of buffing progress?

(Don't worry about the Sharpie. It doesn't stain the polyurethane paint. I can wipe it away with a solvent like acetone.)

Either polishing pad gives similar results, and buffing until the Sharpie grid is gone appears to be a workable control technique.

Water beading on the buffed surface is another indication of progress.

On areas with complex, and especially concave curvature, I'll buff by hand.

I'm not trying to do a fantastic job on the fuselage, but I'll gain experience before I do the critical stuff: the wings.

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Paint #Sand #Buff #Polish

The glider fuselage paint job has been scraped to remove drips and runs, and also to cut off the top of all the orange peel bumps that cover the entire surface.

I had to experiment with making a scraper tool. It required constant sharpening.

I have transitioned to wet sanding with a dual action polisher to remove the rest of the orange peel, but I had to experiment a bit to get a process and system. That's because I can't see the progress of sanding of a white surface that's covered with sanding water sludge. I will probably draw a grid of lines over the fuselage that allow me to monitor progress.

The final photo shows light at a glancing angle across a sanded test patch (fuselage belly...I don't mind screwing up here). I see no signs of orange peel, or larger ripples/waviness.

I think I can transition from this sanding job directly to rubbing and polishing compound.

#AvGeek #Aviation #ElectricAircraft #ExperimentalAviation #Homebuilt #Glider #DIY #Paint #Sand #Buff #Polish

My glider needs a tug that can pull it from the landing spot to the transport trailer or hangar.

That distance may be over a mile at larger airfields.

Glider clubs often use electric golf carts, but those are expensive and way too big for the task. I need a rig that can easily be put in the bed of my truck.

An electric scooter?

Some of them have larger tires, more powerful motors, a larger payload capacity.

Today I tested this model:
https://www.isinwheel.com/products/isinwheel-hyper-x-700w-electric-scooter-with-seat

I measured the static pull...about 40 pounds of force.

That is plenty for pulling a 600 pound glider when you consider that rolling friction is about 1/50th of a vehicle's weight. That comes to 12 pounds.

I don't need high speed. You tow at a fast walk or slow jog.

I don't need dozens of miles of range.

And it's fun to ride.

Need more power for a heavy two-seat glider?
https://www.isinwheel.com/products/isinwheel-h7-pro-1200w-high-end-commuting-electric-scooter-with-seat

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Scooter #eScooter #EV #ElectricScooter

Floor! After taking our anniversary off, yesterday I went about building a frame to hold the floor while I work on it prior to install. After, I set it down and cut out the landing brake. Canards are very aerodynamic and don’t really slow down well; a deployable air brake helps to slow down the aircraft and maintain an approach speed. Given that I’ll be able to slow down via regenerative braking (using the propeller like a windmill), I don’t expect to use the landing brake outside of emergency landings/emergency descents. Which is a good enough reason to make this.

Deviating from plans, I cut this out as a large rectangle. Plans specify a small area for the hinge + a smaller overall landing brake. I have a much wider panel + the area for the hinge it the entire width of the brake.

Today, I spent my time cutting out and fitting foam for the contouring of the floor. Tomorrow, I’ll mix some micro slurry and epoxy the foam in place.

#avgeek #aviation #electricairplane #ExperimentalAviation #homebuit

My wife and I spent 6 hours today glassing the interiors of the fuselage sides. This was the biggest layup I've done so far. We glassed the interiors of both sides at the same time (part of why they're lined up they way they are is to facilitate that), then installed the upper longerons.

I'm very grateful for her help, couldn't have done it without her.

#aviation #experimentalaviation #electricairplane

I installed (microed - epoxy + tiny glass bubbles) the aft spacers from yesterday to the fuselage sides, then I contoured the rest of the fuselage interior. Almost ready to glass these!

As part of contouring, I made the first modification to the plane plans for the purpose of electrification today. There's supposed to be contouring toward the aft end, to allow for fuel sight gages. I don't need those, so I didn't bother doing that.

#electricairplane #experimentalaviation #aviation

Today, on my #electricairplane #experimentalaviation build, I cut and shaped foam for the aft spacers of the fuselage. This was time consuming - the cozy plans do not give precise dimensions for the this fairly complex shape. I mostly eyeballed them, combining that with what little dimensions are given. They're close enough.

#aviation