Sean's Glasair Sportman Build: Gear Leg Fairings

So I started down this path years ago.

First I tried to make aluminum gear leg fairings, and was not happy with them. Made 1, never finished it. I did not like how the two rode inside each other.

Then I thought about using the foam and fiberglass method. The benefit to this is you can add a step.

When I had Langair make my extended gear legs, I asked them to machine a ridge into the gear leg for a step. More on that later.

Then a member of the forum came up with a method to 3D print gear leg fairings. I know (well knew) nothing about 3D printing and modelling, so I avoided this. If I did not have the ridge on my legs for the step I could have just used the other members design. Good old 'rule of 3's'. Change one thing, need to change at least 3 more...

For months and months I have been thinking about and asking others what modeling software to use. They all have their pros and cons... for now I am using OnShape. It's free, with a catch. Everything you model is public. That is fine with me for now.

Then comes which 3D printer.... read lots of reviews, and finally decided on the Bambu Labs H2D (with AMS). They had a Black Friday sale...

So now I have to learn how to model and print. I gotta say this has been a fun journey.

The H2D is a BEAST of a machine. I love it. Works awesome.

OnShape is extremely powerful and fairly easy to use and learn. There are tonnes of how to videos.

So I started off by printing a portion of the existing design from the other member of the forum.

Genius design. Great job BS!

So I need to make mine a bit bigger. I've modeled the first 9" of the fairing, as the gear leg is a consistent diameter that far down.

(Add OnShape pic here)

I had a bard time splitting the part in two. The double curves got bisected, but I then learned that you can add parts together using the boolean feature. That solved that problem.

Learning how to create screw holes... so far am failing. Can't figure out how to locate the point on the curved surface. I will get there... will just take some time.

So I took dimensions of the gear leg all the way down. Next challenge is to determine the best method to narrow the fairing as it goes down. The extrude function has a 'draft' feature. Need to figure out the draft angle and I will try that.

I am used to AutoCAD 2D modelling (am passable at that... not great, but can make something look reasonable). I am used to being able to specify exact distances. You can do that with OnShape, but its not easy. You freehand draw the feature, then add a dimension to it, then you can adjust the dimension. Frustrating - but I am grateful to have a tool that I can use and learn.

First part of my design below. Already seeing some problems now that it is printed.

It fits together perfectly... too perfectly. There is zero slop. Will be prone to crack. This piece took 10 hours to print using PolyMaker PETG. But the quality is outstanding. Super impressed. And I am getting the hang of OnShape. Next step is to test fit and see what I need to change / learn. Very excited by this entire process.

Test fit. Fits very well... almost too well. The two circles that hold the front together are just too tight. They will snap together, but getting them apart is very difficult.

Version 2... redid the S curve that locks the two sides together... much better now. Added the intersection between the fuselage and fairing. Much better now, but could be a bit better.

The new model is about 80% done. I am having a problem getting the loft as the S channel narrows to fully intersect as a surface. Almost there. Then have to add the screw holes, and lastly the internal donut for the step. But its basically together.

So I finally plowed through and finished the model - only to realize I forgot the pins that interlock the top and bottom pieces respectively. Print underway without the pins, but that will allow me to check the rest of the fit. 20 hour print for all 6 pieces (3 tops, 3 bottoms.

Very interesting journey to get to this point. I am tempted to start over again (again) now that I am more fluent. OnShape is so powerful, but you have to think like OnShape. You can do so much with it... but you have to know how to accomplish a task. Google Gemini (free version) has been my saviour. I can ask it how to do something in detail, and it gives me step my step instructions. You also have to think like the printer... and how it is actually going to make the piece. Example... the pins and sockets.... easy enough to create... but the printer cannot print well a hollow with a flat interior end. So I rounded them. Hoping that will work.

First full size test print (without the pins and sockets) for general fitment.

Bit to snug in the middle around the donut for the leg step, and slightly to snug at the bottom as well. Hoping that will be an easy fix to both.

Fixed. Printed a test piece out where it was tight (around the ridge for the gear step). Has a little bit of play, which was the intent.

Deciding on when or not to print a full test piece of the latest design, or just go for it. Probably a full test piece.

Nope... printing a test piece with new settings and new filament.

Using Polymaker ASA filament.
Changed layer height to .15 mm
Changed wall setting to outer, then inner
Slowed outer wall print speed to 50mm/sec
Slowed inner wall print speed to 200mm/sec
Changed to 3 wall loops
Sparse infill density to 8%
Sparse infill pattern to adaptive

8.5 hours print time for 4 pieces.

I am getting some stepping on the ellipse. I need to figure out how to smooth that out. You can see it in the onshape model.

Progress!

Changed the export settings from onshape and have almost completely eliminated the stepping.
Printed test pieces with ASA. Significantly lighter.
Printing the starboard gear leg in its entirety in one shot. 30 hours. Reduced layer height from .2mm to .15mm.
Ordered some TPU. That should make it a bit 'bendy' but printing it 9" tall will be a challenge.

First leg printed out of ASA installed. 30 hour print. Weights 1 lb, 4 oz (565 grams).