Aluminum Wing Structure

[leshoman]

i  not familiar with weights of alum wings but each wing panel on my Legal Eagle XL, readr to bolt on and fly is 27 pounds including ailerons and aileron control horns

[Golden Eagle]

Hi Les,

  That is good information, Les, thanks!  I will keep that information in mind as I investigate the weight aspects of an aluminum spar and preformed ribs.  One thing I can assure everyone is that I will not pursue it if the weight is more than a pound or two (than a wooden spar and wood ribbed wing).  It is my hope that the weight of a full bolt-on wing comes in a bit less than 27 pounds.  If it isn’t, the idea goes out the window.

  What I will do is make:  (1) 2024 T3 .020 rib and (1) false-rib (with lightening holes).  Note that I don’t actually have to make the “bent and formed” 3D shapes of the ribs, just the 2D shapes with the flanges will do, since all I need is the actual weight of the pieces, not the measurements.  Then I will make a practice 4 foot length of a shortened section of spar out of 2024 T3 .032”  that is 7” in height and about 4’ long, along with the typical riveted angle aluminum cap strips, vertical stringers, doublers, attach points, rivets, etc.  Then I will do the math by multiplying the number of required ribs and false ribs, and add both weights to that of the calculated spar length.  Either it works, or it doesn’t work.   I’d like to find out.

  BTW, Les, I used to be based at Vacaville (my hometown).  I’ve flown it to Rio Vista in my Cessna 172 many times.

  Here is an airplane I built and just sold a couple of weeks ago.

Cheers everyone,
Mike Welch

[okdonn]

This experiment will be interesting to watch and see how it turns out. The Tailwind folks build either wood or aluminum wings, though they are very different wings from the eagle series. In general, they have found the weight to be about the same, and recommend that you use the material that you are most comfortable working with.
Also, I wonder if a Cub style rib wouldn't be lighter than the formed sheet ribs, like this:
http://www.eaavideo.org/detail/videos/most-recent/video/5718447898001/building-aluminum-rib-jig?autoStart=true

[Golden Eagle]

Eagler’s:

  I just completed some initial weight calculations.  I found weight charts for sheet aluminum and angle aluminum.  The spar web of .032 AL is .452 lb/ft2.  There is approximately 16.33 sq feet of forward spar and about 9 sq ft of rear spar.  This calc’s out to be roughly 11.4 lbs. of AL for the spars.  Then deduct the lightening holes which knocks off about 1 lb.   The 3/4” x 3/4” angle AL is .11 lbs/ft X 2 (upper & lower) X 2 (wings) gives 8 lbs for the cap strips.  Ribs are made out of .020 AL, which is .284 lb/ft2.  Rib and partial ribs roughly come in at around 9 lbs. total.  Maybe 7 lbs if you space them a bit wider and deduct for lightening holes.

  Therefore, if you add up the various weights of the members, you come up with about:  11.4 + 8 + 9 = 28.4 lbs.  Add another pound for rivets.  Let’s just round it off to 30 lbs. until we get one built (if it ever gets built).

  In a nutshell, it appears as though just the aluminum alone (without fabric and paint) should weigh in the vicinity of 30 lbs per wing.  If one were to shoot for a 32 lb wing, then I’d say upon an initial investigation this isn’t completely a waste of time.  So at the moment, I’ll just ponder the idea.

  I need to mention that the spar dimensions of .032” 2024 T3 is what the Bearhawk uses.  A Bearhawk is by any measure a full size airplane.  Meaning it weighs a LOT compared to an ultralight.  I suppose a guy could reduce the spar from .032 to, say .025, and be just fine on an ultralight.  The weight savings may not be worth the unknown area of making it too thin.  It wouldn’t be worth it to me to save 1/2 lb on an entire wing to sacrifice a considerable amount off strength.

  If a finished, flyable wing came in at 33 lbs each, is that a deal breaker for most guys for an aluminum wing’s internals?  Maybe not for most guys, but for those that REALLY want an wing’s internal structure to be made of aluminum it certainly may be a possible way to go.

  For what it’s worth, I don’t really have much of a problem with the wing having wood spars and ribs.  I am very experienced in both forms of construction, including welding chromoly.   I’m just kicking around ideas.  Don’t shoot me.

MIke Welch

[Golden Eagle]

OkDon,

  That rib video that you furnished is exactly what I think is needed to come up with a viable aluminum wing design.  Clearly that rib uses much less material than the style I calculated, which would significantly reduce the weight of all of the ribs.  Some may have noticed that on my calculations the ribs were the heaviest part of the structure.  The ribs you shared could well bring the design on down to a 30 Lb total each wing.  I’m going to do some “ciphering” on how much that rib would weigh. 

  I’m done.  Upon initial comparison, and using a little thicker material, it comes in only slightly lighter than the full shaped rib.  This was mostly due to the fact that I assumed .032 thick strips to make this type of rib, rather the .020 thickness of a full shaped rib.  If a guy were to use .020 to make the strips, I’m not sure of the integrity.  .020 might be getting too thin for this type of rib. I guess you’d have to make one and see if it feels good enough to do the job.

Mike Welch

[challenger_i]

The wing you have depicted is for a CH-701. While it would have a really good low-speed lift potential, you might want to investigate its drag. You may find that the drag outweighs the thrust capability of a half VW.
 Just something to consider, before you invest the time, and cash.

  Also, as the CH-701 wing structure is designed around a stress-skin structure, and you desire to cover with fabric, you will need to work-up a satisfactory compression, and drag/anti-drag system. As One has to built ribs, any way, you might have a look at the ERCO Ercoupe wing structure. Just a thought.

  Another structural method, for a low n slow bird, is the wing on the old Le Pelican design. The spar, and the leading edge (D-cell structure) is aluminum, and I can't see why One couldn't fab-up sheet metal ribs, in place of the foam ribs.

   Everett

[scottiniowa]

I have been pondering a few of the thoughts on this "new wing" idea.

And I think I will toss some of the reverse thoughts that should be taken up if you choose to go down this road.

IT was wrote:
Re: Aluminum Wing Structure
« Reply #21 on: April 23, 2018, 06:17:45 PM »


The wing you have depicted is for a CH-701. While it would have a really good low-speed lift potential, you might want to investigate its drag. You may find that the drag outweighs the thrust capability of a half VW. 
 Just something to consider, before you invest the time, and cash.

  Also, as the CH-701 wing structure is designed around a stress-skin structure, and you desire to cover with fabric, you will need to work-up a satisfactory compression, and drag/anti-drag system. As One has to built ribs, any way, you might have a look at the ERCO Ercoupe wing structure. Just a thought.

  Another structural method, for a low n slow bird, is the wing on the old Le Pelican design. The spar, and the leading edge (D-cell structure) is aluminum, and I can't see why One couldn't fab-up sheet metal ribs, in place of the foam ribs.

   Everett
Perhaps I am missing a thread, but I do see anyone making reference to the CH-701 profile?  Plenty of reference's to build ways, but nothing to the profile of this  701 rib. There are so many things involved but clearly this is a case of selecting first, the wing profile, then choosing the best method for building that, (alum if you wish and so it goes) Scottiniowa

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 Golden Eagle


Re: Aluminum Wing Structure
« Reply #20 on: February 04, 2018, 12:58:05 PM »


  That rib video that you furnished is exactly what I think is needed to come up with a viable aluminum wing design.  Clearly that rib uses much less material than the style I calculated, which would significantly reduce the weight of all of the ribs.  Some may have noticed that on my calculations the ribs were the heaviest part of the structure.  The ribs you shared could well bring the design on down to a 30 Lb total each wing.  I’m going to do some “ciphering” on how much that rib would weigh.  

  I’m done.  Upon initial comparison, and using a little thicker material, it comes in only slightly lighter than the full shaped rib.  This was mostly due to the fact that I assumed .032 thick strips to make this type of rib, rather the .020 thickness of a full shaped rib.  If a guy were to use .020 to make the strips, I’m not sure of the integrity.  .020 might be getting too thin for this type of rib. I guess you’d have to make one and see if it feels good enough to do the job.

Mike Welch
Doing the calculations, first and foremost, is exactly the thing to do "before" any building takes place.  And it looks like Mike did. So other thoughts on these calculations, is perhaps at the front of cyphering.  Simply being, "you know exactly what the size/shape and strength of the wood spars are.  If you choose to go the lightest route, and use fabric to cover the wing. It would be most prudent to know the spar you have designed is at least the same strength of the wood spars.  If you can't come up with these calculations, anything you do after with RIB design, is really mute.  Simply being, if the spars cannot carry the load, there would be little basis to go on!  These formulas are out there, and in fact in many iterations.  Lots of ways to figure, but in the end, the results are generally close.  Note:  I am not saying if one formula doesn't show it to be strong enough, find one that does... that just don't make sense.    Scottiniowa        

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 Golden Eagle


Re: Aluminum Wing Structure
« Reply #19 on: February 04, 2018, 11:49:16 AM »


Eagler’s:

  I just completed some initial weight calculations.  I found weight charts for sheet aluminum and angle aluminum.  The spar web of .032 AL is .452 lb/ft2.  There is approximately 16.33 sq feet of forward spar and about 9 sq ft of rear spar.  This calc’s out to be roughly 11.4 lbs. of AL for the spars.  Then deduct the lightening holes which knocks off about 1 lb.   The 3/4” x 3/4” angle AL is .11 lbs/ft X 2 (upper & lower) X 2 (wings) gives 8 lbs for the cap strips.  Ribs are made out of .020 AL, which is .284 lb/ft2.  Rib and partial ribs roughly come in at around 9 lbs. total.  Maybe 7 lbs if you space them a bit wider and deduct for lightening holes.

  Therefore, if you add up the various weights of the members, you come up with about:  11.4 + 8 + 9 = 28.4 lbs.  Add another pound for rivets.  Let’s just round it off to 30 lbs. until we get one built (if it ever gets built).

  In a nutshell, it appears as though just the aluminum alone (without fabric and paint) should weigh in the vicinity of 30 lbs per wing.  If one were to shoot for a 32 lb wing, then I’d say upon an initial investigation this isn’t completely a waste of time.  So at the moment, I’ll just ponder the idea.

  I need to mention that the spar dimensions of .032” 2024 T3 is what the Bearhawk uses.  A Bearhawk is by any measure a full size airplane.  Meaning it weighs a LOT compared to an ultralight.  I suppose a guy could reduce the spar from .032 to, say .025, and be just fine on an ultralight.  The weight savings may not be worth the unknown area of making it too thin.  It wouldn’t be worth it to me to save 1/2 lb on an entire wing to sacrifice a considerable amount off strength.
Kind of dangerous game of comparing the web of a 2000# or higher gross aircraft, to one of 575#  EVERYTHING in your load calculations change. Almost to the point, that like stated here, you simply can't get things so thin to comply with the strength reduction plan, but ease of building, becomes the burden do to the building process can't be completed. Scottiniowa
  If a finished, flyable wing came in at 33 lbs each, is that a deal breaker for most guys for an aluminum wing’s internals?  Maybe not for most guys, but for those that REALLY want an wing’s internal structure to be made of aluminum it certainly may be a possible way to go.

MIke Welch

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 okdonn



Re: Aluminum Wing Structure
« Reply #18 on: February 04, 2018, 11:14:20 AM »


This experiment will be interesting to watch and see how it turns out. The Tailwind folks build either wood or aluminum wings, though they are very different wings from the eagle series. In general, they have found the weight to be about the same, and recommend that you use the material that you are most comfortable working with.
Also, I wonder if a Cub style rib wouldn't be lighter than the formed sheet ribs, like this:
http://www.eaavideo.org/detail/videos/most-recent/video/5718447898001/building-aluminum-rib-jig?autoStart=true

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[color][size][font]
Don in Okla.  DE Plans B-40 (small), CE plans CE-02 (all weather),  Tailwind project #746 (medium),  C182A (large)
One size does NOT fit all!
[/font][/size][/color]





 Last bit of cold water- Hopefully we all know that any shape, of any type (aircraft or wing)  can be built. But it can almost always go back to the saying, "if you have enough time and money" it can be done.
An example would be, you MIGHT be able to create a rib for $40.00 and 1.2 hours.  i.e. the XL rib can be built time after time in 30 minutes and the cost far less that what was just mentioned.  And it MIGHT be 3% lighter. But both go against the low cost, easy to build and low labor aspect of this plane. This changes with every aircraft design.  Unless the love for flying something you created, is at top of the list, if you build an aircraft that does exactly the same thing, for twice as much labor/money, it can quickly become a burden on your mind and pocket book.  Don't get me wrong, there are always good things that can be made better.. Scottiniowa

[challenger_i]

Page 1, last post. Mike attached a photo of a CH-701 wing. I guess I over-stepped my limits by responding.

[scottiniowa]

Page 1, last post. Mike attached a photo of a CH-701 wing. I guess I over-stepped my limits by responding.

Heck no, Challenger, (on response)    I just didn't go back that far to see that.  Without response (and correct ones like yours I might add) the new ideas don't get brought out. Thanks for pointing it out.

[challenger_i]

No worries.

  I have been battle-planning a metal-frame wing for a Mini-Max type airplane for some time. Researched many an airfoil, trying to get just a little more
lift for using low horsepower.
 As for structure along the lines of the original wing, the wing plan for the Hummel CA-2 is very close. Also, it uses the Riblett GA30-618 airfoil.

  Regarding the lineage of the Millholand/TEAM airfoil, the original Mini-Max airfoil is almost identical to the NACA 4414. The Mini-Max has a bit more blunt leading edge.

[LSaupe]

If you havent yet seen the rib structure on the Hummel Ultracruiser they do a real nice job in keeping the weight down for a Part 103 all aluminum wing.  The ribs are a truss (riveted) design.

Gull 2000 has an aluminum wing as well (Part 103) though unsure if it has stamped ribs or truss style.  Backyard Flyer has a nice part 103 aluminum wing as well (welded rib design).

Many options out there.

[Leonard]

Hi Guys,
 Remember that the XL wing has been tested to 4 gs that's a 1000+8 # of bricks the jig bent the first time and had to be made stronger the bare wing weighed less than 20 #

[challenger_i]

I would like to point out that both wings specified are stress-skined structures. While there are some good ideas in each wing, One will need to do more engineering, before those concepts could be safely used in a fabric-covered wing.

If you havent yet seen the rib structure on the Hummel Ultracruiser they do a real nice job in keeping the weight down for a Part 103 all aluminum wing.  The ribs are a truss (riveted) design.

Gull 2000 has an aluminum wing as well (Part 103) though unsure if it has stamped ribs or truss style.  Backyard Flyer has a nice part 103 aluminum wing as well (welded rib design).

Many options out there.

[NikkolaiV]

Hey, new eagler here...been debating a build for months now, and either the XL or the Double have fit my interests more than any other aircraft. I was also looking into the aluminum wing design, and found that the Kolb firefly is an aluminum wing, fabric skinned, similar size (~3sqft less surface than the XL, if memory serves.) I also was looking into the Kolb Firestar as an aluminum replacement for the Double Eagle, again a similar surface area wing. Still in the midst of researching, but figured I'd share my preliminary findings and see if there was any feedback out there.

[okdonn]

While not directly applicable due to both being stressed skin wings, there both aluminum and wood wings for the W10 Tailwind. They weigh within a few pounds of each other, the recommendation being to decide which to build based on your comfort with the materials. That having been said, the wood wings are smoother . . .