Discusion Thread: Raceair Skylite Build and sub-kit developments

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addicted2climbing

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Hello All,

This will be the thread where people can ask questions, offer advice and such in relation to postings in the build log titled: Raceair Skylite Build and sub-kit developments.

I just made my first post so have a look and let me know what you think. I will post updates as I move forward. Also trying to finish my Zigolo to make room for the build of the Skylite so for now much will be virtual work in Solidworks and or small things that don't take much space. Zigolo should be done by summer and I hope to get going on the Skylite immediately after.

Keep it clean and as much as possible on topic...

Marc
 

GeeZee

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Looks good! I’ve been thinking about the best way to flute the upper half of the rib (that forms the airfoil shape). I’m thinking a template with the airfoil shape, then I could just hold the rib piece up to the template and flute to match.
 

Victor Bravo

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Cut a thick wooden "male" rib curve shape with depressions sanded into it with a Dremel sanding drum. Then cut a "female" wooden curve to match.

Sandwich the strip of flat aluminum tightly between the male and female halves of the "mold, and clamp everything down to the bench.

Take your plastic hammer and form the rib, tapping the metal into the flute depressions as you go. Basically the opposite of how you would form a solid sheet metal rib with a fluted flange. This way you are making a rib with a "fluted web" more or less.

Now the Skylite rib flange has a 45 degree bend in it too, so you might need to have another wooden form and clamp saddle with a chamfer on it to bend that.
 

addicted2climbing

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Cut a thick wooden "male" rib curve shape with depressions sanded into it with a Dremel sanding drum. Then cut a "female" wooden curve to match.

Sandwich the strip of flat aluminum tightly between the male and female halves of the "mold, and clamp everything down to the bench.

Take your plastic hammer and form the rib, tapping the metal into the flute depressions as you go. Basically the opposite of how you would form a solid sheet metal rib with a fluted flange. This way you are making a rib with a "fluted web" more or less.

Now the Skylite rib flange has a 45 degree bend in it too, so you might need to have another wooden form and clamp saddle with a chamfer on it to bend that.
VB,

Building the skylite rib in that fashion would be difficult due to how they are made. I tried to draw out a blank for that very same method and it does not work will since the rib is broken into separate upper and lower surfaces and not a single sheet with top and bottom. However, the sheet metal shop I had make the blanks is playing around with a few ideas to find a way to supply me a pre-curved upper surface portion. He is a local shop and use to make ultralight parts in the past for other people. For now I will try my hand at building a traditional rib per plans. If he manages to sort it out, I will modify the plans and or jig as needed to accommodate the pre curved part. Also needs to be cost effective and the current jig will work with builders who want to bend their own rib blanks. In an attempt to get the cost down, I am playing with 3D printing nylon (bit of a learning curve) to make the widgets. Also playing with glass filled and standard PETG as its easier to print and still has good mechanical properties.

Marc
 

Victor Bravo

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Looking at the black and white rib drawingm it really looks like making that upper piece at a low price, in quantity, is going to be difficult. Those ribs look like they were designed for individual fabrication by the builder, where time was not a big concern. The big iggue even for a scratchbuilder is going to be making an even, identical set of rib parts. I can't imagine being able to turn out quantities of those rib caps without a "production" quality set of steel stamping dies. Yes it is definitely the lightest way to make the rib, but the cost of that specific design is high in time or complexity.

Three ideas come to mind:

1) Our friend John at the airport has experience and resources with casting. Between your ability to design and draw the mold, and print a plastic buck for sand casting, and his ability to understand and manage the casting process, you can come up with a steel rib form that has the flutes in it on one side and the 45 degree flange on the other side. Put a strip of aluminum in it, clampt it in place with a strap or toggle clamps or a female airfoil shaped edge clamp, and hammer the material over and into the flutes. Then move the hammer to the other side of the rib and hammer the 45 degree flange into it. The 45 degree flange will probably have to have a few flutes in that too.

2) Go to a 2 piece riveted upper rib cap, as the cost of using 25% more metal on that one part. Probably a 10-15% increase in weight for the finished rib.

3) Use a Kolb style rib which is riveted together out of small diameter tubing. You can supply pre-cut gissets and stamped aluminum widgets (the Kolb uses these already), and your customer can crank out a rib in fifteen minutes, bending the upper rib cap over a simple plywood form by hand. .
 

addicted2climbing

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VB,

This Rib jig is for the home builder so slow home fabrication is OK. The jig just makes it easier and a more repeatable process. Only the upper curved portion takes some skill but Ed says once you get a few under your belt they go quick. Before I radically change the design, I may as well try and build them per plans and see how it goes. I have a local machine shop looking into an easier process as well as he has some ideas he is trying out.
 

addicted2climbing

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Hello All,

Its been a while since I had a chance to do any work on the Skylite. Over the holidays, I finally got my 3D printer modified to print Glass Reinforced Nylon and after all the threads I read saying it was a nightmare to print, I find it nearly as easy as PLA. In fact I cant get PETG to ever print well but GR Nylon works every time. Anyhow, it prints well and the layers bond well. Its pretty tough stuff and very difficult to break the part even with Pliers. My initial plan was to print an exact copy of the wing rib attach widgets and have had good success with that, but part of me does not like the direct connection of printed curved plastic interface and a rivet so I have come up with a bit of a hybrid widget. Also the Widgets spec'd on the plans do not leave much room for the head of the rivet gun to access when riveting and the connection rivets would be easy to be pulled off angle using the widgets shown in the plans. By using a hybrid widget, I can print a simpler and stronger widget base and then add a aluminum clip on a tangent to the tube. Also I can make the clip taller to give better access for the gun. Below is a screenshot of the front of a rib and a sub rib is shown behind.

1641789810062.png
The green parts with the yellow rivets is a 6061 sandwich plate for the rivet to bite into. I could also reverse the rivet and not need the plate, but the gun access is too tight there. Moving the rivets to the rear and adding the bite plate is a departure from the plans but it makes riveting easier since there are no clearance issues at all. All holes can still be drilled on the jig as before, jut the orientation of the rivet's are flipped.

1641789856027.png

This hybrid widget is only a few grams more than the Injection molded version so its only a slight hit in weight and as I mentioned rivet tool access is much better. I plan to print this up (blue part) tomorrow and then bend a few clips to see how it all works out.

Here is a shot of the rear widget using the same scheme.

1641790261669.png
small section of wing as test in Solidworks.

1641790472969.png


Open to any advice or discussions on this..
 

GeeZee

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Looks interesting. Just wondering if the new widget could just be cut from aluminum. You’d loose the shoulder that rests against the spar tube. Not sure how that would affect strength. another option (that would take it out of the DIY realm) would be to make aluminum widgets out of T0 (soft) material then have them heat treated to T6. I think Indy has companies that heat treat. I’m sure CA has too. T0 aluminum could be pretty deep drawn to form a large shoulder that rests against the spar tubes. This shoulder could be large enough to eliminate the need for the right angle tabs. Maybe even “easier” would be to weld up aluminum widgets using small pieces of 2 1/4 ID tube for the shoulder. I was actually considering this last option. I figure if I’m learning to weld 4130 I might as well learn to weld Al. It’s possible 3-4 spot welds would be sufficient.
 
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Looks interesting. Just wondering if the new widget could just be cut from aluminum. You’d loose the shoulder that rests against the spar tube. Not sure how that would affect strength. another option (that would take it out of the DIY realm) would be to make aluminum widgets out of T0 (soft) material then have them heat treated to T6. I think Indy has companies that heat treat. I’m sure CA has too. T0 aluminum could be pretty deep drawn to form a large shoulder that rests against the spar tubes. This shoulder could be large enough to eliminate the need for the right angle tabs. Maybe even “easier” would be to weld up aluminum widgets using small pieces of 2 1/4 ID tube for the shoulder. I was actually considering this last option. I figure if I’m learning to weld 4130 I might as well learn to weld Al. It’s possible 3-4 spot welds would be sufficient.
Actually, it would be very, very easy to form the "new" widget from 6061t6. The very small flange could be formed in the forming block sandwich with zero risk of cracking provided you start with the smallest excess possible on the flange edge...probably even net edge.
 

BJC

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Open to any advice or discussions on this..
ake aluminum widgets out of T0 (soft) material then have them heat treated
FWIW, I like the concept of stamping them in soft aluminum, with enough flange to eliminate the tabs, then heat treating them. Include a plan for a drilling jig with the kit, to ensure proper rivet placement into the spar tube.


BJC
 
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flame suit on!
this part could probably be made annealed with the full flange, riveted to the spar with a washer under the head and used un-tempered. A set of forming dies would be needed though...rubber block hydroforming would likely work really well also.
 

cluttonfred

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OK, Marc, I'll be the one to say it.... Do you have a solution in search of a problem? The existing injection-molded "widget" design has worked fine for years, if you can replicate it then why not spend your time elsewhere?
 
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TFF

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I would want aluminum if it was doable. I would think stamping them out would be pretty easy. I can see the plus of the plastic as it probably is cheaper in small batches. That and less hand finishing.

How long does it take to print one? That’s a lot of printing just for one wing. If you had ten orders, it would take a month if printing. That and aging. Aluminum will age like all the other aluminum. Plastic, which is amazing, is going to be different, better or worse. It will be harder to gauge.
 

GeeZee

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Both CluttonFred and TFF have good points. Just buying them from Oscar is the easiest option but having a single source is risky, especially if Marc is planning to kit these up. I don’t know what it would cost to have twenty something of these printe by a third party. I have an Ender 5 and it would take it forever to print these. Assuming I could even mod it for nylon. mr Downey makes a good point. Maybe we don’t need as much strength as we think. Perhaps a weaker more ductile alloy would work. I guess the $64 question is how “strong” is the reinforced nylon widget and what alloy and thickness would be required to replace it.
 
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