#homebuilt — Public Fediverse posts

A week ago I had my third emergency detached retina surgery. Earlier today the surgeon conducted a one-week post-op exam and said I'm healing fine with everything looking good...so far.

The surgeon deliberately put a gas bubble in my eye, so I can't return to the mountains until that bubble is gone...in 4 to 6 weeks.

Once I get back home, I will do a few minor things to the glider, then assemble it again for a full-power taxi test.

I need to cultivate more patience....

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Retina #Eye #Surgery #Medicine #Vision

The glider now has 12 pounds of lead shot and epoxy added to dead space in the very end of the tail boom.

My initial estimate of volume indicated that I could add 8 - 10 pounds this way. I'm pleasantly surprised, and I didn't make a chocolate covered mess of things as I was pouring this goop into the tail.

I need to add a few more pounds to the tail. Phase two of this project will use lead plate, bolted to the vertical fin spar. (I need to unroll the 1/4-inch plate first, then develop a template to cut the lead.)

I could not add the epoxy/lead shot mix all at once because of the exothermic reaction of epoxy. When mixed epoxy is in a thick blob (instead of a thin layer), it generates enough heat to warm itself...which accelerates the chemical reaction...releasing more heat...further accelerating the reaction.... I have seen epoxy smoking hot because of this, so I added a bit, waited a half hour, checked temperature with an IR non-contact thermometer, added a bit more when it was clear that the exotherm was only very mild, etc. That took a while, but turned out well.

I note that Roto Metals has a discount on some 1-inch lead plate. Get your fork lift ready. No free shipping!

https://www.rotometals.com/lead-sheet-plates/sheet-lead-1-64-lbs-sq-ft/

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Ballast #Math #Density #Exothermic #Chemistry #Thermodynamics #Lead #Epoxy

The glider's 3rd battery now has a sewn carrying handle that makes it easier and safer to install in the crowded battery box.

Next, I need to devise a retaining system for it and finish the wiring harness that connects it to the rest of the system.

Progress will slow for the next day or two because the things I have ordered (epoxy, lead shot, etc.) will be delayed while we ride out a snowstorm that should end tomorrow.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Safety #Battery #Sewing

Where does the 'typical' glider battery go in this electric glider?

In the battery box, next to the high voltage motor batteries.

My final decision on this battery location depended on the weight and balance measurements I made last week. It shows that I need to add weight to the tail...so, the heaviest batteries are full-aft in the battery box, and this 3rd battery goes in front. All of this is aft of the tail in the fuselage/tail boom.

I now need to sew some sort of sack and carrying handle for this battery. It's not a heavy battery, but I want a secure way to handle it as I install/remove it.

Above my hand is a black/gray marbled-pattern object. It's a yoga block. That semi-dense foam will be cut to size to take up any dead space along the sides of the battery box to prevent the batteries from banging side-to-side if the other retaining systems fail.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Safety #Battery

My glider will use a tow rope that is too strong. That rope, when under maximum pull, may damage the glider.

I need to install a weak link as a mechanical 'safety fuse'.

Here is one weak link system I can use:
https://wingsandwheels.com/tost-weak-link.html

But which weak link is appropriate for my glider?

Federal Aviation regulations require a tow rope (or weak link) to have a certain breaking strength with regard to the maximum operating weight of the glider:

"The towline used has breaking strength not less than 80 percent of the maximum certificated operating weight of the glider or unpowered ultralight vehicle and not more than twice this operating weight."

https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-91/subpart-D/section-91.309

To complicate matters, my glider can carry 400 pounds of water ballast. When I'm flying 'dry', I would prefer to have a weak link that is just strong enough for the dry glider, and when flying 'wet' I would prefer a (somewhat stronger) weak link appropriate to the heavier operating weight.

See the second graphic, which shows which Tost weak links I can use in the dry or wet ballast condition.

I will start out getting the weakest weak links allowed (green, yellow, and white) and see if that launches me well without premature weak link breaks.

Pro-tip. Try not to lift the rear end of the ground launch car.
https://youtu.be/kd9QxRPb3hk?t=33

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Math #Weight #Safety

My glider needs the center of gravity shifted aft, so I need to add weight in the tail.

The first photo is looking into the rudder cove (rudder removed). I can bolt some lead plates to the flat face of the vertical fin spar, but I will need even more weight added back here.

Note that the rudder hinge support is glowing green...a flashlight on the other side is illuminating it.

That part is hollow and it's nothing but dead space. I can add lead shot and epoxy in there.

The second photo shows the view of this pale green fiberglass part from the other side. Before I can add lead shot in there, I need to add a dam to retain it while the epoxy cures.

Third photo shows a piece of scrap Plexiglas that fits up against the end of the rudder hinge support.

Final photo shows the Plexiglas dam glued into place with RTV silicone caulk. It has a semicircular cutout that allows a larger diameter piece of tubing to be placed there while I pour lead shot and epoxy into a funnel and fill that empty space.

Half of the caulking work was done blind and by feel. I am accessing this tight space from the inspection port in the side of the vertical fin. There is just enough room for one hand and this part to pass through the port and then get positioned. I practiced before applying the caulk so I knew exactly how to position and twist the part so that I didn't make a mess and most of the caulk ended up in the desired location.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Epoxy #Ballast #Lead #Plexiglas

The electric glider's two main batteries each weigh about 16 Kg (36 lbs). I need a positive restraint system that can handle vibration and especially negative G.

Yesterday evening I epoxied in place some retaining blocks for the two battery clamping bars, but the garage gets cold overnight. I placed an incandescent lamp over the top of the battery box and wrapped some towels as a 'tent' to keep the warm air from easily escaping. This allowed the battery box to stay slightly warmer and accelerate the curing of the epoxy.

The second photo shows one end of a battery clamping bar (yellow) that fits under a carbon fiber inverted shelf (black). On each side of the clamping bar there are now two blocks of garolite (pale green) that prevent the battery block from sliding off to the side.

Garolite (G-10) is commonly used as the substrate for printed circuit boards, and you can get it in significant thickness, which is what I need.

https://en.wikipedia.org/wiki/G-10_(material)

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Epoxy #Chemistry #Temperature #Garolite

For the glider's ground support equipment, there is good news and bad news in the first photo.

The good news is that the eScooter has more than enough pulling power to move the glider about on a smooth, level paved surface.

The bad news is that this version of the red tow bar means that any sideways push against the tail of the glider is transmitted to the eScooter...and makes it extremely difficult to keep the scooter from toppling over.

I had to re-design the tow bar.

The second photo shows what I've come up with. Now the wheel on the yellow tail dolly carries the weight of the glider's tail and reacts to any sideways loads. The eScooter merely needs to provide the pulling force and doesn't have to deal with those sideways forces. That should be much easier and safer for the driver.

The next time I assemble the glider at the airport, I'll give this towbar a final test with the eScooter.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Logistics #Design #Dynamics #Physics

Where is the center of gravity of the empty glider located?

If you measure the location of the main wheel and tail wheel (reference to something such as the glider's nose), and the weight each of them carry...you can do the math to answer that question.

Where is the center of gravity when the pilot is in the glider?

Climb in, and then take the same measurements.

Now I know if I need to add trim weights to the nose or tail, and how much.

Determining center of gravity location is critical for safety of flight and good handling characteristics. I'll do these measurements and math more than once so I can be very confident of the results.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Aerodynamics #Math #Mass #Weight #Balance #Safety

One surface of one glider wing has now been covered with mylar gap seal tape.

Tomorrow I will flip the wing over and apply gap seal tape to the other surface.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Fairing #Drag #Aerodynamics

Gliders often go to significant lengths to reduce drag.

My flaperons are driven by a push-pull tube that exits the wing skin and pushes against an external drive horn. There are two of these setups on each wing...four external devices that need fairings.

But they and the flaperons move. That complicates things.

First photo shows one push-pull tube and drive horn without fairings.

Second photo shows the inner/smaller fairing that will eventually be glued into place.

Third photo shows both fairings in place and the flaperon near the limit of its down travel.

Fourth photo shows both fairings and the flaperon approaching the limit of its upward travel.

One fairing of the two pairs on one wing are drying overnight. Tomorrow morning, I will make final adjustments to the remaining inner fairings and then glue them in place.

I'm using RTV silicone, which needs humid air to cure well. It's winter in New Mexico and the air is super dry. I have put a very large pot of water on the wood stove to humidify the air overnight.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Fairing #Drag #Aerodynamics

I need to make a cloth canopy cover for the glider.

Now that I have the canopy installed, I can measure overall length of the planned cover and the width at various points.

I'll lay out a pattern on paper that is 1/4 or 1/3 of the overall width...like gores for a hot air balloon.

I have three different types of stretch fabric from very light to somewhat heavy. We'll see what results I get.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Sewing #Fabric

This video shows the flapperons moving as camber-changing flaps. The two control surfaces move in unison. My flap control system has five settings. The central setting is flaps zero or flaps neutral. Two settings increase the camber more, which is suitable for low speed flight. Two settings decrease camber... this is when the two flapperons move upwards.... and this is suitable for higher speed flight.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Technology #Wing #Aileron #Flap #Flaperon

Adjusting the flaperons.

This video shows them operating as ailerons. I move the control stick side to side.

Note that at max deflection, the control surface moves above neutral position more than it moves below neutral position. This is the principle of differential ailerons. It helps reduce adverse yaw.

The first comment to this toot will be a video showing the motion of the flaperons as camber changing flaps.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Technology #Wing #Aileron #Flap #Flaperon

The glider instruments need to be tested in a more holistic way...as holistic as you can get when the fuselage is sitting in the garage.

First photo shows tubing attached to the pitot probe. The long external tube allows me to add pressure to the pitot system while looking at the instruments on the panel.

Second photo shows the airspeed indicator (small round display) and glide computer screens. Both of those systems have pitot pressure sensors. I have pressurized the external tubing so that the airspeed indicator shows about 105 knots indicated airspeed. As you can see in the lower part of the glide computer display (V IAS)...the two devices agree within about 1 knot. I can't ask for better than that. (The vario also has a pitot pressure input, but it also uses GPS. It's very confused and angry that GPS says the glider is stationary, but it's supposedly moving through the air at a ridiculous speed. I may have to wait until flight testing to really evaluate the total-system performance of this advanced vario.)

Another bit of good news is that the leakage rate of the pressurized and sealed pitot system is pretty low. After a minute or two the indicated airspeed only drops a few percent at the most. That's not perfect, but it's pretty good.

Third photo shows what the instrument panel looks like when all the devices/screens are running. That's right, if I lose electrical power, my instrument panel is a blank, black hole.

Since I powered up all the screens, it means I'm ready to hook up an ammeter to measure current draw of each device, and my maximum load when everything is running. I'll do that tomorrow.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Technology #Instruments #Avionics #Test #Testing #Pressure #Airspeed

Because the back side of the glider's instrument panel is so crowded, I have moved the vario speaker to the space under the turtle deck, aft of the wing spars.

To make connections easier, I added some 3.5mm audio jacks and plugs to the speaker box and the long cable running aft. (2nd photo)

The first photo shows one audio plug and two jacks. What's up with that?

The standalone vario has an audio output, and the glide computer also has an audio output. They use different styles of sound, programmable with slightly different parameters. Now I can more easily choose and change which audio output I want to use.

This should end my soldering work. Tomorrow I'll be working on (third photo) all the pneumatic connections from the three pressure probes: pitot, static, and total energy...to all the flight instruments that need these pressure signals.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Audio #Wiring #Speaker #Pneumatic #Technology

I have checked the alignment of the pitot tube with the horizontal axis of the glider's tail boom.

I had to put the glider in a level flight attitude to align the inertial measurement unit in the variometer, and will do it again when I perform the weight and balance analysis.

The first photo shows a small portion of the tail boom, which has a gentle conical profile. Because of that, I had to put a calibrated spacer at one end of the bubble level. (I also double-checked by putting the same setup on the bottom of the tail boom...the boom is now level.)

I took the opportunity to measure the inclination of the pitot tube that is mounted high on the vertical fin. It's well within one degree of level also, which is what I want. (If you keep misalignment under about 15 degrees, the pitot tube should provide accurate indications of total pressure.)

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Sensor #Technology #IMU #INS

The final instrument has been installed, and it passes basic function tests.

It's a modern glider variometer that has an inertial measuring unit, two GNSS receivers, a three-axis magnetic field sensor, and two air pressure sensors. It can determine the true flight path, in 3D, very precisely, and its response time to changes in air motion is very short.

In this short video, I show that the vario display (small round screen) is sharing data with the glide computer (larger rectangular screen). As I raise the instrument panel, the artificial horizon shows a corresponding change.

Here's a good explanation and demo:
https://youtu.be/RoCG2RNBR_k?si=ML8QYJ5HzvSivLW1

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Sensor #Technology #Wind #IMU #INS

Installing the flaperon on the glider's wing.

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

It's a full-span flaperon, in two halves. Each half is almost 12 feet long.

Each flaperon half has 8 hinges made of a pintle/gudgeon pair. (1st photo)

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

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

When installing the outer flaperon half, I also have to engage two sets of pin/sockets that ensure the two halves move as one unit. (2nd photo) (Each flaperon half is driven by its own flight control linkage, not shown here.)

One of the 8 hinges on each flaperon half also serves as a retainer that handles side loads. (3rd and 4th photos.)

The flaperon halves are intentionally not very stiff longitudinally so that they flex with the wing, but they are much stiffer radially to resist deformation because they are driven at only one point by the flight control linkage. This feature is fairly easy to achieve in composite fabrication because you can orient the fabric fibers in certain directions. In this case we used Kevlar, not carbon or fiberglass.)

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Wing #Flaperon #Kevlar

I am almost finished with wet sanding the last side of the last glider wing.

The orbital sander has done all it can do on the mostly flat top and bottom of the wing, but the leading edge is strongly curved.

I'll sand that narrow strip by hand...tomorrow when I'm not tired.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Paint #Sanding #Polishing #Wing

I must be making good progress wet sanding the glider's wing.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Paint #Sanding #Polishing #Mess

The final (2nd) glider wing is getting sanded to remove orange peel from the polyurethane topcoat.

After sanding is complete, I'll buff it with rubbing compound to give it a semi-mirror finish.

Tomorrow I hope to finish sanding this top side. (The bottom remains unsanded.)

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Paint #Sanding #Polishing

After the epoxy has cured overnight with the help of a heating blanket, the mold is disassembled and gently pried away from the counterweight.

The weight is over 1600 grams (a bit more than 3 pounds....ummmm, what is that in slugs?)

To remove all the plasticine that stuck to the counterweight, it's not elegant, but a wire brush removes it.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Epoxy #Composite #Workshop #Lead #Mass

Making a lead counterweight for the glider's control surface.

The mold is made from scrap MDF 'wood' that is covered with clear packing tape, waxed, and plasticine applied to seal against leaks of epoxy.

After epoxy is mixed, a bit of lead shot was added to the mold, epoxy poured on top, mixed with a stick, and tapped with a hammer to encourage air bubbles to leave and the lead shot to settle/pack a bit tighter.

The aluminum tubing one top of it all puts a negative half-cylindrical shape in the part...which is what I need to make it nest/fit to another part.

(The first comment to this post/toot will have a few more photos and text.)

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Epoxy #Composite #Workshop #Lead #Mass

I made some fiberglass 'angle iron' that will be used as braces for the top of the glider's instrument panel.

The mold was a piece of square steel tubing, well waxed.

Note that one of the fiberglass pieces is made from shorter scrap fabric, so the middle is a bit thicker because of the need for 1 inch overlap (2.5cm) of the scrap pieces.

Now I need to use a cutoff wheel to trim and clean up the parts.

Some of the paint from the square steel tube is now stuck to the fiberglass parts. Because these are internal parts, I don't care about this cosmetic flaw.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Fiberglass #Epoxy #Composite #Workshop

My glider wings need mylar to cover over the control surface gaps, but what width?

When the flaperons are moved to fully expose the pintle pockets, I can still use a 30mm wide strip of mylar.

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

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

All control surfaces will get mylar covering to reduce drag.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Mylar #Drag #Aerodynamics #Wing

Two black Sharpie lines will show my progress of gentle hand sanding of the glider wing's leading edge. This will be to remove the orange peel texture.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Wing #Sanding #Paint #Painting #Sharpie

The underside of the glider's right wing is ready for sanding to remove orange peel from the final coat of paint.

(Now I know how long of a line a Sharpie can draw before it runs out of ink)

The three oval areas are inspection/access ports to the inner moving parts of the flight control system...flaperons, and spoilers.

The grid of black lines will help me monitor the progress of sanding.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Wing #Sanding #Paint #Painting #Sharpie

Delivery day for the oxygen cylinders!

I got help loading them in the truck when I picked them up at the delivery point in Alamogordo.

Back home, I'm alone and the unloading was slower and deliberate. Fortunately, I only had to lower the cylinders off the bed. Raising them would have required a ramp or other equipment.

I got them into the garage before the next monsoon rainstorm.

I need to make a wall rack to hold them upright, safely, securely. I think I need to get a 20-foot stick of 1-inch square steel tubing from the world famous Basin Pipe and Metal.

Can I make an air liquefaction plant?
https://en.wikipedia.org/wiki/Liquefaction_of_gases

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Steel #Oxygen #Hypoxia #HighAltitude

Successful test of the right wing tip light assembly.

The electrical power was provided from the wing root, 25 ft away.

The first comments to this post will include some photos.

Because glider wings and winglets are removable, I had to make the wiring connections work despite repeated disassembly. I am using automotive door jamb connectors that are spring-loaded knobs or bullets of brass.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #LED #Lighting #Navigation #Wiring #Wire

The glider turtle deck and cockpit get a few more items.

The oxygen tank is now mounted under the turtle deck. A retaining cable runs back to the rear steel carrythrough tube, and will only be used once...in the event of a crash. (Wooden 2x4's are mockups for the wing spars to ensure I am installing items with acceptable clearance.)

A two-litre water bladder hangs behind the seat pan, and the drinking tube is at a convenient location.

I still have to install another fiberglass antenna bracket under the aft end of the turtle deck.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Fiberglass #Composite #Safety #Hydration #Water

Glider progress on closing out open spaces in the fuselage.

First photo shows the new fiberglass closeout panels I made this weekend. The new panels have bits of blue tape on them.

Second photo shows a fiberglass GPS antenna bracket near the top of the turtle deck.

What you don't see in the second photo are the wing spars, which will run across this space.

I am considering also making fiberglass shields to cover the autoconnect funnels, which are gray and located aft of the wing spar cutouts.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Fiberglass #Composite

I need to install some anchor plates into the glider, around a blind corner (a bulkhead flange) in cramped quarters.

https://www.aircraftspruce.com/catalog/hapages/anchornutsk1000.php

It's easy to drop these small parts, and Murphys Law dictates that they fall into an inaccessible place.

Fortunately, you can run string through the mounting lugs to serve as a lanyard.

If you install an anchor nut on metal, you use rivets. On composite panels you often embed them in epoxy.

If you work in a wood shop, you probably use tee nuts:
https://www.aircraftspruce.com/catalog/pnpages/04-02058.php

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Nut #AnchorPlate #Lanyard

Gliders need help to get airborne.

Here's an update I pulled from an SSA (Soaring Society of America) newsletter:

"The SSA awarded several grants for projects and Bill Daniels of the White Sands Soaring Association provided an update on how grant money is advancing their winch project."

"Our thinking is shifting to power electronics, data capture and temperature management. The big battery pack which can power 40 to 50 launches on a charge is also sitting on the shop floor. The inverters are in hand. The load pins (a kind of load cell) serve as axles for the upper pulleys while measuring forces on them. They are being made on the other side of the world and should arrive in a few weeks. Various connectors and other bits arrive daily. Since everything is liquid cooled and we operate in a hot climate, we will need robust temperature management systems which are still being designed."

https://www.ssa.org/

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Winch

Successful high power test of the glider's electric motor with the spinner and propeller installed.

I had it at full power: 4600 RPM and 150 amps at 115 volts DC. I conducted this test three times. No problems with vibrations, excessive temperature of the motor or any other components, or rapid draining of the batteries.

This is a major milestone for the electric motor system.

#AvGeek #Aviation #ElectricAircraft #Homebuilt #Glider #DIY #EAA #Motor #Engine #Propeller #Battery #Test #Milestone #Success #Goals

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

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

We ran a Unix-like OS Xv6 on our home-built CPU with a home-built C compiler

https://fuel.edby.coffee/posts/how-we-ported-xv6-os-to-a-home-built-cpu-with-a-home-built-c-compiler/

#HackerNews #Unix #Xv6 #HomeBuilt #CPU #CCompiler #TechDIY #HackerNews

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