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Dec 01, 2019, 09:31 PM
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GeoffS's Avatar
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3D Printed Leading Edge for Sheet-Foam - Just another crazy idea...


A few days back I posted about making some 3D-Printed leading-edge "shoes" for my EzFly Trainer: https://www.rcgroups.com/forums/show...postcount=2925

I had some time on my hands waiting for some other jobs to finish up, so I quickly adapted the 8mm EzFlyer design to a double-layer of Dollar Store 5mm foam and printed a test-piece.
Probably not a really practical idea, but I may try it out on a build with a KF wing sometime...

The print is pretty light. I think the 70mm test-section I printed was about 2.5g.
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Dec 02, 2019, 07:41 AM
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Extreme Sports's Avatar
Not a crazy idea per se, but perhaps doing it on a foam KFM wing is not the most logical application. Reasons should be obvious. Rather print a female of the desired LE profile and use it as a sanding template, then wrap the LE with packing tape.

Might be worth doing on a large, dual skin wing made from 2 sheets of depron, or a hot-wired core....in both cases you get the benefit of a good airfoil across the full chord, so adding some weight to the LE might make some sense.

Even better, use the technique for large wings with complex scale parts such as slotted flaps and hinged ailerons (frize or otherwise). Here the added weight might be less of an issue, given the size and willingness to trade weight for scale appearance.

This link shows my original concept. https://www.rcgroups.com/forums/show...&postcount=370 and below are some pictures of the test piece.

I've since applied it to add slotted flaps on a ~1.7m correx skinned Grand Tundra look-alike. IIRC they added over 100g, but at that size there was no noticeable performance hit. I've not taken any photos yet, but they do look really cool compared to simple hinged flaps.
Dec 02, 2019, 12:27 PM
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I really like this idea. However, I imagine that the leading edge cap would need to be adjustable or come in various sizes. The foam is not always the same thickness.
Dec 02, 2019, 12:41 PM
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GeoffS's Avatar
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Originally Posted by Michael763
I really like this idea. However, I imagine that the leading edge cap would need to be adjustable or come in various sizes. The foam is not always the same thickness.
True.
I didn't expect this would be anything but an idle curiosity for folks...

If there was any interest, I could upload it to Thingiverse and a "Customizer" design.
This allows you to set the parameters to your desired values and create a new STL file.

For example, I have a servo control-arm with a number of adjustable parameters: https://www.thingiverse.com/thing:3979363
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Dec 02, 2019, 12:43 PM
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GeoffS's Avatar
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Originally Posted by Extreme Sports
... Even better, use the technique for large wings with complex scale parts such as slotted flaps and hinged ailerons ...
That seems like a MUCH better application!

Cool designs!
Last edited by GeoffS; Dec 02, 2019 at 05:40 PM. Reason: Fix markup
Dec 03, 2019, 06:37 PM
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Quote:
Originally Posted by GeoffS
True.
I didn't expect this would be anything but an idle curiosity for folks...

If there was any interest, I could upload it to Thingiverse and a "Customizer" design.
This allows you to set the parameters to your desired values and create a new STL file.

For example, I have a servo control-arm with a number of adjustable parameters: https://www.thingiverse.com/thing:3979363
Attachment 12861447
I did not mean for my statement to be taken negatively. I was just hoping to point out that options to print different sizes/thicknesses or adjustability could be advantageous. That is why I started my comment with I really like this idea. When I use balsa for leading edges, I have to sand down the thickness, which makes it frustrating and time consuming.
Dec 03, 2019, 07:22 PM
If it flies, I can crash it.
rocketsled666's Avatar
You could make a hole in the LE form so multiple segments could be strung together on a CF rod. If you the LE and TE this way, you might not need a separate spar in the wing.

I think this is a very interesting idea. I have 3D printers. I have foam. I have Carbon Fiber rods. I'm going to play around with it some, myself.
Dec 03, 2019, 08:06 PM
Retired CAD guy
birdofplay's Avatar
Great OUT OF THE BOX idea.

It ties in with the Hybrid 3dp and foam efforts.
Things like Lockey has been doing.
https://www.rcgroups.com/forums/show...Jet-EDF-Hybrid
and
https://www.rcgroups.com/forums/show...os-DIII-Hybrid
and
https://www.rcgroups.com/forums/show...oam-3D-Printed

et al
Dec 04, 2019, 12:16 AM
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GeoffS's Avatar
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Quote:
Originally Posted by Michael763
I did not mean for my statement to be taken negatively...
Non taken!
Quite the opposite, I thought your post was a good suggestion.

I am honesty surprised this has generated more than passing interest.
I was totally serious about creating an customizable model if others were interested in experimenting with it.

I was playing around yesterday evening with printing this using the "spiral vase" mode of the slicer program.
This is probably the best way to work with this kind of structure.
It prints about 5X faster and weighs about half of my original "fancy" version.
Without the "wings" it is a little harder to get aligned with the top and bottom of the foam, but it wasn't bad when I tried it.

I glued a short section to a double thickness of some 5mm Dollar Tree foam to see how it would look.
The section is hollow with an surface only on the bottom end.
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Dec 04, 2019, 12:24 AM
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GeoffS's Avatar
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Quote:
Originally Posted by rocketsled666
You could make a hole in the LE form so multiple segments could be strung together on a CF rod. If you the LE and TE this way, you might not need a separate spar in the wing.

I think this is a very interesting idea. I have 3D printers. I have foam. I have Carbon Fiber rods. I'm going to play around with it some, myself.
That's an interesting twist to the technique!
I was trying to create the lightest "fairing" that could attach to a foam wing for support.

Your idea is sort of the reverse: take structure (i.e. weight) out of the foam part of the wing and put it into the leading and trailing edges.

Let me know if I can help with generating the 3D models.
My design is in a fairly obscure modeling language called OpenSCAD.
I would be happy to share my code, if it would help.
It's probably simpler to import a set of airfoil coordinates into whatever design program you're familiar with and work from there.
Dec 04, 2019, 12:33 AM
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GeoffS's Avatar
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Quote:
Originally Posted by birdofplay
Great OUT OF THE BOX idea.

It ties in with the Hybrid 3dp and foam efforts.
Things like Lockey has been doing....l
Thanks!

Those hybrid foam/3d-printed designs are amazing.
Way (WAY- like a couple of levels higher) more sophisticated than mine!

I'm encouraged to continue. I think there are some possibilities for using different materials for different parts of a plane.
We already mix plywood and balsa or foam. This isn't really any different.

Foam is light and easy to work with, but it's hard to get repeatable complex shapes.
Someone in the EzFly thread thought a good use would be to print a "negative" leading-edge template to help shape the foam more accurately.
That's another possible way to combine the strengths of each technique/material.
Dec 04, 2019, 01:50 AM
If it flies, I can crash it.
rocketsled666's Avatar
Quote:
Your idea is sort of the reverse: take structure (i.e. weight) out of the foam part of the wing and put it into the leading and trailing edges.

Let me know if I can help with generating the 3D models.
Yep, that was my thinking. In my workshop I have a plane I bought a really long time ago, don't even remember when, called a "Merlin". It's a CF rod fuselage with wing, tail and a motor. About a 4' span I think. There's a plastic block fixed on the fuselage rod that holds the RX/Servos/ESC, plus some landing gear. The wings are like lunch-tray foam, formed to make a deep undercambered airfoil. The only structural support is a 2mm CF rod running the length of the leading and trailing edges. The rods stick out about 2" from the inner end of the wing and plug in to receptacles on the plastic block on the "fuse". The wing isn't supposed to be stiff as a board, and it's not. This is a slow flier model. It flexes a bit in flight. But it's surprisingly robust for a 4' wing with no main spar. That's where the source of my idea came from.

As for help, I've got a lot of CAD experience under my belt, but thank you for offering. Besides two Formlabs SLA printers and a Robo3D FDM, I have a laser cutter and a 4-axis CNC. I make stuff all the time (or at least, when I have the time). I've already got a bunch of projects underway, though, so this is something I'll save for later this winter probably. But let me know if I can help you with anything!
Dec 06, 2019, 11:58 PM
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GeoffS's Avatar
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OK, this has now gotten completely out-of-hand...

I just finished designing the first pass at a fully parametric airfoil design library...
(the earlier version was pretty limited in the dimensions of the LE and thickness of the wing)

The first item I designed and printed is another leading-edge .
This time I wanted to increase the bonding surface between the printed LE piece and the main wing foam.
I decided to push the one of the two pieces of foam (the upper one in this example) aft and make a matching aft edge of the LE piece.
When I assembled the test print to some foam scraps, the difference between the previous version (tht just butted against the foam) and this was dramatic.
This version is much more sturdy.
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Dec 07, 2019, 11:17 AM
Rough Landing
rainyday101's Avatar
We need a hybrid scratch built forum. I just ordered a 3d printer because I have been thinking about exactly what you are doing. I want to build hybrid foam, balsa, and 3d printed planes using the strengths of each material.
Dec 07, 2019, 11:25 AM
Registered User
That looks really nice and useful. Will you be tackling one layer/flat plate through five layers/KFm-6?


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