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Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by FritzW, Aug 11, 2016.
Hmm, how light could such riveted construction be with a very light 2 stroke in the nose?
Hey 80ties we are coming back, with simple affordable planes, just better and lighter with the same hp of the R277
I think it would easily make Part 103.
It would take a little reworking in the nose if it didn't use an inverted bed mounted engine. It could use a HiMax clone wing like a Legal Eagle or the QBWW or typical tube spar UL wing, ...or a pop rivet, L angle spar with an .020 sheet web and HotWing's(?) fluted angle pop rivet ribs. ...or
Nope! As much as I'd like credit it is Cheapracers contribution.
It could also have been addicted2climbing in this awesome thread.
Either way, there are lots of of good, light aluminum rib ideas out there.
I would definitely re-re-re-submit the Kolb wing for this idea again. Amazingly simple, proven in a large fleet. Inexpensive, requires only two simple steel weldments per side. Folds up tight.
I've never seen nudie pictures of a Kolb wing. What's the difference between a Kolb wing and a typical tube spar UL wing?
Oh thank goodenss you asked
First, it's all aluminum tube with a couple of very simple steel fabricated reinforcements.
The Kolb uses a 5 or 6 inch diameter main spar tube, which provides the bending resistance as well as the torsional resistance. So no "D-tube" or structural leading edge sheeting needed.
The main spar tube is installed much further aft in the wing chordwise locatio than seems "right" at first glance. But by putting it there, the airfoil torsional moment (leading edge down from the moment of the airfoil) balances out the lifting force (leading edge up from the quarter-chord station). So the ribs are not always trying to twist on the spar (pop rivets in chear).
The ribs are built up from very small diameter tubing, 5/16" if I recall. They are very simple trusses, low parts count, with .025 or .032 gussets for the mostpart. The central part of the rib at the spar location is a square-ish aluminum piece that has a flanged hole that slides over the main spar and rivets into place. These ribs are very very light, but also very fast to build.
The Kolb uses 1" or 1.25" tubes for the leading and trailing edges, which I believe do not take any pf the primary loads. They're there to attach the ribs and fabric to, and hinge the ailerons.
There are two steel fittings. The outboard fitting is a very simple weldment from round 4130 tube. It is slid inside the main spar tube and riveted. It provides not only the strut attach hard point, but it also serves as aspacer to keep the spar tube from buckling at the point of highest bending load (strut attach).
The inboard fitting is also a steel weldment that does four things. It rivets to the spar tube at the root and provides a steel tab with the main spar bolt hole. It also extends rearward to the trailing edge tube (aileron spar), and provides a strong point for the diagonal drag/anti-drag tube. The third thing is that it provides half of a universal joint yoke for the wing fold mechanism. Lastly, it serves as the rear wing attach point to the fuselage or keel.
The result is a wing that meets Part 103 weight easily, requires only one lift strut, folds back tighter than any other wing, builds flat on a table like a model with no sawhorses, no water levels, no jigging or fixturing, etc., has decent flying characteristics, and uses stock standard cheap sizes of 6061 tube for thevast majority of it.
The Kolb series uses a 5 inch diameter main spar on 103 and LSA single seat aircraft up to 800 or 850 pounds, and a 6 inch spar on the two-seat and higher performance models.
The only "error" or shortcoming with this wing is that the stock, original, olde-tyme ultralight version used sections of piano hinges to attach the ailerons to the rear tube. This was marginally OK on an ultralight at 40 mph. When the weights and speeds increased over 30 years, they never changed around to a bolt type hinge (or a Heim ball/bolt hinge), and when the wings flexed even a tiny amount the piano hinges bound up, making the ailrton controls very very heavy. So that is the one design change that needs to be made for certain.
The Kolb wings were instructed to be built on a flat table with no twist for building simplicity and maximum possible performance. But... big surprise... this gave them a little sharper stall than some other ultralight type airplanes (duh). I would definitely put in 1/2 or 3/4 inch of washout in the outermost rib, just like a model.
Otherwise I believe the Kolb wing design is a big winner when you score it on cost, time, ease of fabrication, stock material sizes, and minizing the number of specialty weldments.
The leading edge looks a bit sharp to my eye. I always thought that the sharpness of the stall had to do mainly with the airfoil shape. Would it help tame the stall to use a little larger tube for the leading edge? Maybe 2 inch?
My Thoughts on the Kolb wing is that it could also be Improved with a more modern shape than the original "that looks like the right size tire to bend the leading edge around" "oh lookie it is perfect".
Is there a good source for 5 or 6" tube with the correct wall thickness? Problems with finding the right tube was what changed the Ranger from a tube boom fuselage to geodetic.
Have you verified that that is what Homer did?
He was a very good designer, and was flying powered ultralight airplanes long before the EAA erroneously anointed John Moody as the “father of ultralights” for retrofitting an engine to an existing foot launch glider.
Ask Dana, lol.
Kolb is good source, friendly, reasonable.
Not in Europe!
Fritz, What tubing would you use for the fuselage ?
For the tailvolume I would use 28mm ( or 30mm x 1,5mm) x 1,5mm
Another issue with the Kolb wing might be mating a single spar wing to a two spar fuselage. I going to have to dig out my Airbike plans...
“I going to have to dig out my Airbike plans...” and start drawing up an aluminum tube and gusset version to match up with my Kolb like wings... (gig). What’s one more project, eh
Kolb wing would be adaptable to a 2 spar fuselage, just different spacing between the spars. I would agree with a larger LE radius, but the existing one may not be responsible for the stall behavior. I'd try twist before I changed the airfoil.
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