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#experimentalaviation

1 post1 participant0 posts today
Public
TomKrajci 🇺🇦 🏳️‍🌈 🏳️‍⚧️

This is part of a fairing that goes over the glider's tail wheel. I'm using this part to develop my skill at scraping paint with a straight edge razor.

This part fits on the underside of the glider, so nobody really looks at it. It is at the end of 21 ft of fuselage, so the air flow by then is plenty turbulent...so I do not need a pristine surface like I do for the first foot or two of the fuselage.

Let's not talk about all the pinnoles, shall we?

Anyway, if the part is convex, or saddle-shaped and I can get the razor across the positive curvature axis to do its work... I can quickly and fairly smoothly scrape down runs and drips to get them almost flush with the rest of the surface. Then I smooth it with 600 and 1200 Grit paper before buffing.

(After I develop my skills on such small belly parts, then I'll be comfortable working on the fuselage, and finally the wings.)

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Paint #Sand #Buff #Polish

Closeup view of a painted glider part...a tailwheel fairing. The low angle of the light helps highlight runs in the not-very-good paint job. A straight edge razor can be used to scrape away the high parts of runs and drips, and if you're careful, you don't mar the rest of the painted surface.
Public
TomKrajci 🇺🇦 🏳️‍🌈 🏳️‍⚧️

Polishing the glider's paint - a brief experiment with an electric dual-action polisher on a test piece.

I used a coarse foam disk and cutting/buffing (not polishing) compound. The machine was at the lowest speed and light pressure was used for a minute or two.

This is a promising follow up to: universeodon.com/@KrajciTom/11

The difference in surface prep was obvious. Where the paint had been sanded with 1200, the surface gained a gloss almost instantly. If the surface was sanded with 600, it remained hazy. Those sections only sanded with 400 were very hazy, even with more polishing time and a bit more pressure.

It looks like I'll hand sand to 1200, then use the electric polisher.

I just had an idea. If I build a bracket/clamp to hold the polisher upside down, I can hold small parts and better control the process.

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Paint #Sand #Buff #Polish

Brief experiments with machine polishing on surfaces sanded with different grits. Even with only a minute of polishing, those sections that were sanded with 1200 grit became glossy quickly. The reflection of the light is not at a glancing angle. I'm figuring out how to manage the sanding and polishing process.
I will build a bracket/clamp to hold the electric polisher upside down...to allow me to hold small parts and better control the polishing process.
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TomKrajci 🇺🇦 🏳️‍🌈 🏳️‍⚧️

I need to remove the orange peel texture from my painted parts. I will sand the flaws to remove them.

But then I need to use finer and finer sandpaper to prepare to buff and polish the paint to a mirror finish.

This evening I'm learning how much work it takes to sand away the flaws, and what grit to use. (400? 600?)

And I'm learning how much work is needed at finer grits to prepare for buffing.

If you have ever ground and polished glass, this will be a familiar process.

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Paint #Sand #Buff #Polish

A small glider part (battery box cover) has been sanded to remove orange peel. The finish is now matte. I have made some test pads of foam rubber, double sided tape, and various grades of sandpaper. Working with bright light helps me evaluate my progress and surface quality.
Even with a slightly coarse paper (600 grit)...at a very glancing angle the sanded surface of the paint presents a specular reflection. This can help evaluate the quality of the sanded surface because with finer grits the surface should be specular at a less glancing angle.
Besides 600 grit, I also have 1200 and 2500 grit. I hope that is fine enough to provide a surface that buffs and polishes quickly.
Public
Aut

Tuesday build at the EAA hangar. We started by making some slat support backets for the nose ribs while another team identified the ribs for the wing. An encouraging start to our build as we have nice instructions, a nice kit, and nice videos to help us.

Several members in a hangar at a very large work bench, each working on sorting and categorizing some aircraft parts.
thin aluminum angle that has been marked out with various points and had relief holes drilled on the bend. These will become nose rib reinforce brackets for the slats.
Some people figuring out the placement of ribs on a wing spar using a tape measure. The placements are given in millimeter offsets from the end of the spar (so-called stations)
Two people carrying a wing spar with ribs clecoed in place where they will live. The wings have been marked with marker for their position.
#eaa#experimentalAviation#avgeek
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TomKrajci 🇺🇦 🏳️‍🌈 🏳️‍⚧️

How to remove/demold a part from a fragile part. (Hint: You can create shear in more than one way, and it may be better than creating a peeling action with hammer and chisel.)

The blue Styrofoam that served as the form will be destroyed as it's removed from the fiberglass wingtip weel, but it's a one-off form/mold that lacked any taper.

(This is a follow up to universeodon.com/@KrajciTom/11 )

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Wing #Epoxy #Fiberglass #Composite #Shear #Peel

No! You risk damaging the wing's surface this way. (OK, you could use a plastic/rubber wedge, but let's try a finesse method first...)
The long clamp squeezes on both ends of the fiberglass part...never touching the wing. This squeeze causes the base of the fiberglass part to bow outwards...shearing along the surface of the wing.
Only light force was applied to tighten the clamp...and the part easily popped off.
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TomKrajci 🇺🇦 🏳️‍🌈 🏳️‍⚧️

Making a custom wingtip wheel for my glider's right wing.

The bottom of the wingtip was covered with clear packing tape, then lightly waxed.

Hot glue temporarily attached the blue Styrofoam mold/form, which also contains the 60mm diameter roller blade wheel.

The part is made from seven plies of 7725 weave fiberglass that will be cut into a triangular shape after wetting with epoxy.

No vacuum bag, so this is a hand lay up. I had to use some small pieces of metal to coax the fiberglass to stay in the correct place.

The garage will be heated overnight so that the part cures, then some tugging and a rubber mallet should separate the part.

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Wing #Epoxy #Fiberglass #Composite

The underside of the wing tip has been covered in clear packing tape, then waxed.
This is one ply of dry fiberglass, colored white, laying over a piece of green plastic sheet. Faintly visible through the fiberglass is a triangular pattern. After wetting seven plies, I will cut the fabric to that triangular shape. That shape will drape over the form and make the part in one step. The two edges of the open triangle will join and overlap along the trailing edge of the part, aft of the wheel.
Wetted fiberglass has a green tint. Scrap metal helps hold the fabric in the correct location. Strips of light brown fabric are Teflon coated fiberglass, which serves as peel ply. I'm using it to also help coax the fiberglass into the desired shape.
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Rachel Brindle

Yesterday I made the decision to build a new landing brake panel. There’s just too much masking tape debris that’s epoxied to the panel. I’ve already spent some 10 hours trying to sand it off. While I could spend more time sanding it and getting it available, it’ll be much less time to build a new one.
Another part marked “not for flight”.
I already have excess material on hand for this, so I’m not really even losing time on this decision. In fact, I’m gaining time.

Anyway, masking tape bonds really well with epoxy, don’t use it as a kind of mold release. Plastic packing tape, however, works well as a mold release.

Part of the inside of my first landing brake panel. “Not for flight” is written in all capital letters on it. There is also a lot of masking tape remains on the skirt of fiberglass surrounding the foam panel.
Close up of another side of the landing brake panel, showing more masking tape detritus that’s proving time consuming to sand off.
#avgeek#aviation#ElectricAircraft
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TomKrajci 🇺🇦 🏳️‍🌈 🏳️‍⚧️

Discovering and fixing a small mechanical interference in the spoilers.

The spoiler cap, in some places, wasn't fitting into the recess in the wing properly.

Why?

1st photo - spoiler is halfway retracted into the wing. One of the parallelogram arms is at a 45 deg angle. You can see that I have already removed some semicircular sections in the upper spoiler paddle to avoid parts colliding as the spoiler closes.

2nd - looking directly up into the spoiler paddle. There are spring loaded bolts to hold the spoiler cap. This particular bolt is rather close to a parallelogram arm...

3rd - ...especially when the arm is swinging more as the spoiler is almost fully closed.

4th - That telltale dimple on the parallelogram arm tells me everything. The bolt is a little bit too long.

A Dremel and cutting wheel removed 2mm of bolt.

Problem solved!

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Wing #Spoiler #Parallelogram #Geometry #Interference #Dremel

A view of the back side of the upper spoiler paddle (carbon fiber, black) as the spoiler is halfway closed into the wing. One of the grey round steel parallelogram arms has swung to a 45 degree angle. (The arm will swing much further as the spoilers fully close.)
Looking vertically up into the spoiler paddle. One of the spring loaded spoiler cap retaining bolts (shiny, plated metal) is visible. The upper end of the darker gray parallelogram arm is also visible in the right half of the photo. The spoiler is fully open because the parallelogram arm is vertical.
The spoiler is almost fully closed in this closeup view. The gray parallelogram arm has swung through more than 60 degrees from vertical. The arm is getting close to the end of the bolt. (Only the very tip of the bolt is visible from behind the aft lip of the spoiler paddle.)
This dimple in the gray steel parallelogram arm is definitive proof that it is colliding with the bolt. Shortening the bolt solves the problem.
Public
TomKrajci 🇺🇦 🏳️‍🌈 🏳️‍⚧️

Checking the fit of the spoiler cap into the glider wing. (I need to do more sanding of the beveled edges because it sits a little bit high.)

The typical glider spoiler is mounted on a swinging parallelogram, and is controlled by a push-pull tube. It also features an over center lock, which was not activated in this video.

Note that the lower spoiler paddle is not installed at the moment. When it is, it produces a complete wall to the local airflow over the top of the wing. That is how we control descent angle during final approach to land.

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Wing #Spoiler #Parallelogram #Geometry

Public
TomKrajci 🇺🇦 🏳️‍🌈 🏳️‍⚧️

Making a fiberglass wingtip wheel for the glider wing.

1st photo - making the mold/form out of foam, with a 60mm diameter inline skate wheel in place. Note that the underside of the wing is covered with clear tape to protect it from epoxy when I lay up 7 plies of glass.

2nd photo - making the fabric template. A single piece of glass fabric (weave 7725 because it drapes so well over various curves and corners) will make the final part, but there will be an overlap along the trailing edge. I draped a piece of plastic over the foam form after it was hot-glued to the wing and then traced out the pattern, with some reference marks such as a center line.

3rd - Demolding the cured part by squeezing it so that it flexes/distorts a bit...and the epoxy at the base easily shears off from the waxed clear tape. (No need for hammer and wedges.)

4th - rough sanded final part.

#avgeek #aviation #ElectricAircraft #ExperimentalAviation #homebuilt
#Glider #DIY #Wing #Fiberglass #Epoxy #Composite

Blue Styrofoam is attached to the underside of the glider wingtip. The foam is easy to sand and shape to the desired contour. Unfortunately, such a mold is single-use becuase I did not add any taper to the part, so I had to tear the foam out with pliers after the fiberglass cured. No worries, I have paper templates in order to quickly make a second form for the other wing.
A template for the fiberglass fabric. This wingtip wheel is a single-layup operation. Note that while the leading edge will be a continuous piece of fabric, but the trailing edge will have the two ends overlap.
Demolding a part *should* be an easy matter...if you set things up correctly...good geometry in the mold, proper use of release wax, etc.
Final part after rough sanding to remove the outer weave pattern. It will get a proper trimming job later, then painted white.
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