The Ranger, an easily built high wing LSA runabout

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billyvray

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Hotwire?

My similar idea mentioned on the first thread:
tube spars (though it still applies to this). Each air foil is cut through the middle chordwise for a "top" and "bottom" rib half. Stack foam pieces up for ribs, or a block if you want a continuous section. Spar shapes, trussed shapes, holes, etc. can all be cut out. You could cut large sections of foam or pieces of ribs in two shots.
Then stack and glue the tops and bottoms together around your spar-and-compression-member-ladder and glue together as a unit. Or glue ribs individually and then slide of the spars and then assemble the wing components.

Personally I'm playing with ending up with a completely skinned outer surface but large trussed sections removed internally, and then cover with vinyl. It may require a light glass or dacron covering prior, testing will be done to check the strength of the rib panels.



Neat stuff guys, I like this thread.
 

ScaleBirdsScott

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If you added some wire leads (and a way to safely handle the sucker) a hotwire cookie cutter sounds like a pretty awesome way to make foam ribs to me.

Would "stamping" and compressing foam into a compressed state do more harm than good? I haven't messed with foam that much in a while but I've always worked it with a mind towards trying not to crush it. If uniformly done in a controlled manner though, I could see how maybe a "hot" press could cause the outer region on the foam to both compress in and then melt together an outer shell on the foam, to, in a way "case harden" the part. It probably does help.
 

Tiger Tim

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Or glue ribs individually and then slide of the spars and then assemble the wing components.

Personally I'm playing with ending up with a completely skinned outer surface but large trussed sections removed internally, and then cover with vinyl.
I think that's how the Belite ProCub's wings are put together; a zillion foam ribs all shouldered up to each other with metal or carbon compression ribs every so often in the stack. IIRC it's even vinyl covered.
 

billyvray

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Supposedly he covered with dacron and vinyl but I'm not positive on that. Same end effect though - smooth skin, reduction in "finishing"....
 

FritzW

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...alternative fabrication methods without CNC equipment....
a26355a3-90f6-46b6-9606-51b840707cc9_1.eb35f71b12ece7c274e2dc197e99ca4a.jpg You can get one of these at WalMart for $23. Of course, you could build a far better one just as cheap (and the worlds leading homemade hot wire cutting gurus are probably on this forum).

The TP plans have a clever way to do it. Make a template out of 3/4" ply and drive a couple of nails through it. Flip the template over so the nails are pointing up. Press a piece of foam onto the nails to hold it in place then zip around it with a hand router (or hot wire cutter). The plans claim you can make a rib in 30 seconds, but that's just sales pitch hype. I think it would take closer to 35 seconds.
 

Victor Bravo

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Based on the color schemes of Fritz's foam and wood, I have a real hankering for:

View attachment 78697

Might have to call this wing method the Shortcake
Scott, does that mean you are going to fly the Ranger wearing a bright white suit and a little white cap, becoming the "Good Aero Humor Man?

I want to go on record saying I don't like the foam ribs, because they are not very durable and aluminum really doesn't like any kind of glue. Having to go thru a chemical conversion process to glue to aluminum negates any time saved cutting the foam ribs. So yes you could glue plywood capstrips on the foam ribs to make them structurally acceptable, but then you have to come up with a method of structurally... and robustly... attaching the foam ribs to the aluminum spars.

THEN all you have actually done is to make a weather-resistant structure into a non-weather-resistant structure.

With all that said, a stack of foam ribs can likely be band sawed out in less time than a hotwire cutter is set up, templates made, and then wire cut.

What is so awful about aluminum ribs, by the way?
 
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Pops

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I have made aluminum ribs for wings of 2 Bearhawks, can turn out a main rib ready to use with the lighting holes flanged in about 20 minutes. They are 2024-T3, .025 and .035. Building is fun.
Please don't take all the fun away.
 

Geraldc

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cutting foam ribs.jpg

This is how I did my pvc foam ribs. Cut out aluminium template on bandsaw and put two sharp screws in to locate foam
that was rough shaped.I used a laminate trimmer in my shaper. You can use a router table.The bearing on the cutter runs on the template.An hour later and ribs were all done and all identical.I have a cnc router but rarely use it these days.
 

FritzW

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The purpose/goal of the Ranger, besides being a fun, good flying little airplane, is to be an open source, non-fiddly, non-tedious, quick build "kit on a thumb drive".

Sheet metal ribs ain't rocket science, I've pounded out dozens of them. but (to me) they get tedious real fast. *If good, safe, durable ribs can go from 'aisle 12 at Home Depot' to 'glued to the spars' in an afternoon then they're the right ribs for the Ranger. ...at least until someone in the open source world comes up with a faster and easier way to do it.

*foam ribs aren't set in stone yet, they're just leading the pack.
 

ScaleBirdsScott

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For me the key would be weight. Can it do the job and survive for a given amount of time? I'm also coming at it from the perspective of "for an ultralight" such that the airframe is the disposable bit. If it gets damaged or degrades you swap the foam out. Swap a whole wing, it's only $200. Maybe he Dacron sail is still good and just the foam and junk got a little soaked? No big deal.

Y'all wanting a proper N-numbered LSA version may well want a more longevity-minded wing structure and that's perfectly viable, especially without a super tight weight limit to abide. But this being open source I'm quite in favor of making the design general and adaptable enough that a variety of options can exist. Why not have 2-3 landing gear configurations? Why not have 2-3 wing methods on deck?
 

Geraldc

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cutting foam ribs2.jpg
These foam ribs are by rough calculation about 1/3 the weight of alloy.They weigh 24 grams each or 0.8 oz.
Material is Gurit Corecel M at 70kg per m3. Very strong and compatible with epoxy, vinylester and polyester resins.
Thickness is 8mm
 

Vigilant1

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"Fritz, please design us an airplane!"
"Thanks!"
oh
"But don't use ribs like that. Those are wrong":)
 

FritzW

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I put together a couple of mock ups tonight to start checking out if/how these ribs are going to work out. The XPS is 1" thick instead of 3/4" like I plan to use but it's all I had on hand. The blue-green adhesive is Stewart System Ekobond, it's not what I'd use either (maybe) but it's close enough for what I'm doing with this test.

One of the ribs has 1/32" Birch ply capstrips and the other is 1/16" birch ply. The orange stuff is 2 offset layers of 2" cast tape (I had it on hand and it's pretty neat stuff, water activated). It'll be interesting to see how the cast tape "C" channel works out.


20190228_194257_resized.jpg 20190228_194257_resized.jpg 20190228_205610_resized.jpg
 

FritzW

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When the naysayers start throwing out comments like that it makes me think I'm on the right track. ...that, and several decades of hundreds of airplanes having no problems with foam ribs. :gig: It's always the guys who are the first to admit they have no background in structures or materials that are the first to tell you how your structures and material won't work.
 

Victor Bravo

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OK, I will once again admit 100% that I do not have a formal background in structures and materials. I don't know exactly what Fritz' formal education is on this stuff either, and he may have ten or a hundred times better understanding of this stuff than I do.

Regardless of who it is, Fritz or Billski or Autoreply or anyone else, I want one of the people who does have a significant formal education and background in these materials to please humor me and answer these same questions:

1) On a simplified and low-cost build, intentionally designed for amateur garage level homebuilt airplane hobbyists, how do you achieve a robust, reliable bond between foam wing ribs and an aluminum spar?

2) What kind of service life would be reasonable to expect?

3) How much stronger or weaker, or more robust or less robust, are 3/4" XPS foam ribs compared to .025" 6061-T6 hammer formed aluminum ribs?

If I am wrong, and a qualified materials engineer verifies foam ribs with ot without 1/32" plywood caps are stronger or more robust than .025 aluminum ribs, then I will stand corrected.
 
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