KR2

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ronp987

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Hello,

Does anyone have experience with the KR2? I’m specifically looking into how difficult it is to remove the wings. I’m looking for a plane similar to either the KR2 or Sonerai that has the ability to easily remove the wings in case hanger space isn’t available. Right now I have a J3 kitten Reliant SX that has removable wings but definitely not for taking on and off on a regular.

Thanks in advance
Ron
 

TFF

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KR2 have removable wings but not quick removable wings. The Sonerai is more close to what you want. One of the original needs was to truck it to races. Onex is probably the most useable. Buying a flier or building? Lots of times builders don’t add the folding stuff if you are buying.
 

Pops

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I built a KR-2 back in the 1970's when it first came out. I had a reamed fit for each bolt in each outer wing attach fitting. With a cantilever wing its something you would not want to be removing often.
 

don january

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Its been quite some time since reading but I remember a KR-2 having a yoke and u-joint from a small car incorporated into the wings mounted to a tube on front root spar that would slide away from WAF's and linkage and fuel line connections if applied. It would swivel the wing 360 degrees and fold at any direction to pick up saddle at leading edge of HZ stab. As Pops pointed out this procedure is time consuming and I imagine adds undue ware on the 8 bolt holes in WAFs. O.P. I see your looking for a Plane so your in luck. Now to find one that fits your need.
 

Hawk81A

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I would think if you were planning on frequent removal of the wings, having the fittings reamed for taper pins might be better. I think I remember Ken Rand saying something about this at his last Sun n Fun. There was also a recent reference to a separate folding mechanism on here. Dennis
 

kr2pilot

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I have a KR2. Since the wing bolts are in shear you can use quick-connect pins with cotter keys to keep them in place. The plans call for two AN6 bolts in the front spar and two AN3 bolts in the rear spar that once removed cause the wing to slide off nicely.
 

ronp987

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Thanks everyone this gives me some insight. I’m on a waiting list for a t hanger but this is great info in case I don’t get one.
 

David L. Downey

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I built a KR-2 back in the 1970's when it first came out. I had a reamed fit for each bolt in each outer wing attach fitting. With a cantilever wing its something you would not want to be removing often.
While the KRs do not use them, I thought the purpose of taper pins, washers, castle nuts and cotter pins was to make a precision fit tolerant of repeated separations?
 

TFF

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Not necessarily repeated separations but more like precise tolerance match. If you get a taper pin to seat past a light touch, you might need a pneumatic hammer to get it out and a new pin. It doesn’t pull surface with it when removed but it is held with friction. The nut on the end sets and is a safety of sorts. The Teenie Two uses a light spring to keep the optional taper pin seated. Not a fan of something that’s loose holding my wings on. The project one I had in high school had bolt on wings.
 

Hawk81A

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You wouldn't want to torque the pins on installation, just tight enough to take up any play, so you wouldn't necessarily need a pneumatic hammer. A "C" clamp and socket (or tool fabricated like such) could easily break the pin free.
 

TFF

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A C clamp/ socket can work if not too seated. I use a C clamp on helicopter driveshafts. Most of the time I have to leave it and do something else, and an hour later you hear it pop apart. To do their job, they do deform; a lot will depend on how tight it needs to be to get the friction to hold in place.
 

philb

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Hello,

Does anyone have experience with the KR2? I’m specifically looking into how difficult it is to remove the wings. I’m looking for a plane similar to either the KR2 or Sonerai that has the ability to easily remove the wings in case hanger space isn’t available. Right now I have a J3 kitten Reliant SX that has removable wings but definitely not for taking on and off on a regular.

Thanks in advance
Ron
google my friends kr2 ken atkinson g -bvia it had removable wings fairly quick removal
 

Doran Jaffas

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I would think if you were planning on frequent removal of the wings, having the fittings reamed for taper pins might be better. I think I remember Ken Rand saying something about this at his last Sun n Fun. There was also a recent reference to a separate folding mechanism on here. Dennis
My Sonerai 2 had taper pins. Did not remove them often but it wasn't difficult to do. Still, I agree that removing the wings on any aircraft is not a good idea to do often.
 

rlkidd

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About a week ago, I removed the wings from a KR2 that I had recently acquired, this one has 4 AN6 bolts and 4 AN3 bolts per wing, nylock nuts and associated washers, along with the aileron attachment bolt (nylock w/washers, but it should take a castle nut and pin because of the rotation is sees). Pitot tube disconnect as well (tubing over a tube for the splice). The bolts were difficult to access, a ratcheting wrench was helpful, and I'd consider grinding a wrench down to fit better if I had to do it often. Wing attach fittings seem to fit well (snug), you will need a helper to wiggle the wing slightly to take the pressure off the bolts to move them in or out. Wings are relatively small and light weight, easily handled with two people. This plane did not have any covers over the wing attach fittings, so things might be different for your situation.
Plans may call for longer bolts, that go all the way through the front to back of the WAF, but this one doesn't have clearance to fit those in. That would reduce the number of bolts and sync up with kr2pilot's post earlier.
My friend's Sonerai has wings that pivot very easily, and fold back along the fuselage. It seats two in tandem. Both aircraft seem to have tight seating if you are a large individual.
KR2 is a pretty small plane, you may be able to fit it under the wing of a Cessna if hangar space is tight. If you put it on Harbor Freight moving dollies you could snake one in on an angle. If you take the wings off, they are about 8 feet wide, and not very tall. I think the folded Sonerai may be a little bit narrower, but will be longer. I'm not certain on the horizontal stabilizer width comparison. I hauled a KR2 project, on its belly, underneath a Sonerai, in an enclosed trailer. The KR2 is definitely a smaller airplane.
 

Victor Bravo

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I built a KR-2 back in the 1970's when it first came out. I had a reamed fit for each bolt in each outer wing attach fitting. With a cantilever wing its something you would not want to be removing often.
This is very important ^^^^^^^^^^^^^^^^

If you look at ANY cantilever wing that is designed to fold or be removable (gliders, powered aircraft, shipboard carrier-based aircraft) you will notice that the bolts or pins or shafts that are used for this are much much much larger than regular bolts.

Why do you suppose that is?
 

PiperCruisin

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Why do you suppose that is?
Is this a leading question?

My guess:
Gliders - long wings = larger bending moments
Carrier aircraft - BFM and large landing loads
Single shear designs - preferably avoided
Fatigue - Stress concentration considerations are more important in fatigue than ultimate loads.
Single bolts vs bolt pattern/multiple
 

Hawk81A

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I don't see an AN-6 (main) and certainly an AN-3 as being exceptionally "large". IIRC, wasn't the KR series stressed for 6Gs? (I could be wrong on that).
At his last show, Ken Rand mentioned that his KR-2 had spent the night under a twin Beech at his stopover in Texas.
I thought the build quality of G-BVIA seemed exceptional. The locating blocks for wing attach were a nice touch. Shame that plane had the mishap.
 

BJC

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For perspective, the Glasair-II has a single piece spar attached with an AN-6 in double shear on each side, plus an AN-3 in single shear on each side at the rear spar.

Six g, 260 MPH Vne.

BJC
 
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