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anyone building a king kobra?

Old 07-30-2007, 09:14 PM
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Default anyone building a king kobra?

just checking. i have decided to build a couple of older planes, the king kobra being one of them. anyone building this plane or have they recently? thanks in advance
Old 07-30-2007, 09:40 PM
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Default RE: anyone building a king kobra?

Not recently but I have built one in the past, its a typical Sig kit with printed balsa sides and built up stab. I changed mine by making it a tail dragger with the LG mounted on the fuse just ahead of the wing.
Old 08-03-2007, 03:30 PM
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Default RE: anyone building a king kobra?


ORIGINAL: dhal22

just checking. i have decided to build a couple of older planes, the king kobra being one of them. anyone building this plane or have they recently? thanks in advance
Hello there,

I have one Brand New In The Box .... Not even the plastic clear film is removed from the kit !!!

I was flying it back in the 80's ... many memmories, so I decided and bought one in 200. Still in the box though I am building my Oxalys by TS Composite.

It's an ich to start thinking of building it.

Regards
Old 08-05-2007, 06:24 AM
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Default RE: anyone building a king kobra?

i am well underway on the KK but i think more info needs to be in the kit building forum.
Old 08-05-2007, 01:47 PM
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Default RE: anyone building a king kobra?

The King Kobra is a fairly easy build, if you build it "stock" according to the plans. It's stable, snaps OK, and is aerobatic enough to fly the old-style, 1970's-style "pattern". The thick wing keeps the speed relatively slow. Mine's about 10 yrs old, but it's a bit heavy. I plan to make a major rebuild: lighten the wing (add top and bottom spars, and cut out large bays out of the foam wing between "rib" stations); change from trike landing-gear to tail-dragger; change the vertical fin/rudder to a more conventional layout with the rudder extending aft and below the elevators; add a bottom, ventral fin from the wing trailing-edge to the enlarged rudder to increase side area for better knife-edge flight; and change the slanted-engine mount to a full side-mounted engine.
Old 08-05-2007, 02:02 PM
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Default RE: anyone building a king kobra?

Are you planning on cutting out a "honeycomb" pattern in the foam wings? It's a really effective way to lighten the wing without sacrificing much strength.

Old 08-05-2007, 02:34 PM
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Default RE: anyone building a king kobra?

I'm not sure what you mean by the "honeycomb" pattern. Do you mean a series of hexagon-shaped cut-outs (looking down at the top of the wing)? Cutting a true honeycomb pattern seems a bit tedious, especially for my short attention span.
My cut-outs will look more like a series of large side-by-side octagons, separated apart by the "rib" material left at the rib-stations. Open bays will be recovered with plastic film. Given the existing cut-out for the aileron servo, most of the span-wise, bending strength in the wing is in the leading edge section, along and ahead of the high-point of the airfoil. I'm counting on the "diagonal" material remaining at the "corners" of the octagons to help minimize warping.
Old 08-05-2007, 02:47 PM
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Default RE: anyone building a king kobra?

Received your picture. Your technique looks great. I'll keep it in mind for building another foam wing from scratch. In my rebuild, however, I'll be cutting away and discarding a lot of the wing skin with the underlying foam.
Old 08-05-2007, 08:14 PM
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Default RE: anyone building a king kobra?

Hey Nathan...That looks Kewl!! So do you Hotwire those cut-outs?? Or some other method??

Thanks...

Chuck
Old 08-05-2007, 08:50 PM
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Default RE: anyone building a king kobra?

The stock KK does not build heavy so doing this type of cutouts on the foam is not need but can be done if you want to save a few ounces. Go easy on the glue when skinning the wing and you will have a fairly light wing. The plane is relatively small so a standard .60 will fly it nicely. I powered mine with an OS .61 FSR. If doing one again I would add the servos in the wing and as I said before make the plane a tail dragger.
Old 08-05-2007, 10:44 PM
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ORIGINAL: navav2002

Hey Nathan...That looks Kewl!! So do you Hotwire those cut-outs?? Or some other method??

Thanks...

Chuck
I didn't get a picture of my wing before I sheeted it []. That picture was from another club members similar plane, but I used a very similar cutout pattern with identical results. It really does lighten the wing quite a bit. Believe it or not, the foam is not the least bit flimsy.

Yes the cut-outs are hotwired. I just added a long thin metal attachment to my solder gun, nothing fancy. The big thing is to think carefully and make sure your cutouts will not interfere with anything (wing tube, servo mounts, etc). I made a template with the cutouts to lay over the wing, then marked them in with a Sharpie. Remember, the wing still has to take an enormous amount of load in the maneuvers we put our models through. After that it's pie if you have a steady hand.
Old 08-06-2007, 06:53 AM
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Default RE: anyone building a king kobra?

I'm building this plane mostly because i need the building practice. i've been out of building and flying for 10 yrs until last yr. the KK appealed to me in several ways. it won't be the fastest but it will be a start. and it's big enough for me to add retracts, oversize the engine if i want and do a light glass job on the exterior. i have already prepped the wing for aileron servos and it will be a tricycle gear as i am using spring air retracts. I'll see if i can figure out how to add photos.
Old 08-06-2007, 07:12 AM
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Default RE: anyone building a king kobra?

i think i've got a photo of a wing uploaded.
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Old 08-06-2007, 07:43 AM
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Default RE: anyone building a king kobra?

Looks wonderful. Keep up the good work!

Nate
Old 08-06-2007, 10:04 AM
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Default RE: anyone building a king kobra?

I wish one of you "honeycomb" fans would weigh all of the pieces of foam that you have removed from the wing and report the weight here. I doubt there is a 1/2 ounce of foam to be measured. Yes, the glue not glueing those sections "could" decrease the weight some, if you put the glue on the honeycomb and not on the wing skins. I've never understood the fascination with this technique, especially after seeing more than a couple wing failures because the honeycomb process weakened the structure to the failure point.

I'm not trying to start a fight, just a discussion. No offense intended.


Ed Cregger
Old 08-06-2007, 10:44 AM
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Default RE: anyone building a king kobra?

No offense taken. (I don't offend easily. [8D]) You are right, just the wings won't do as much, but using these little tricks on the whole build can really add up. Granted, I've only used this technique once, but I've never had a problem with my wing failing. It's all about being careful where and how much you do it.

Anyway, this is dhal22's thread and about the whole airplane, so let's not get too stuck on this one subject.
Old 08-06-2007, 10:45 AM
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Default RE: anyone building a king kobra?

ORIGINAL: Ed Cregger

I wish one of you "honeycomb" fans would weigh all of the pieces of foam that you have removed from the wing and report the weight here. I doubt there is a 1/2 ounce of foam to be measured. Yes, the glue not glueing those sections "could" decrease the weight some, if you put the glue on the honeycomb and not on the wing skins. I've never understood the fascination with this technique, especially after seeing more than a couple wing failures because the honeycomb process weakened the structure to the failure point.

I'm not trying to start a fight, just a discussion. No offense intended.


Ed Cregger

Good Point...Reminds me of a story:

A buddy of mine was building a KitFox Speedster (Full Scale)...He's an excellant craftsman...built a few Aircraft..A couple of RV's and KitFox's...

Kitfox gave an option on the Speedster drawings to cut some lightning holes in the ribs of the Vertical Stab, Rudder, Horizontal Stab and Elevator (if I remember correctly)...He elected to do so...He laboriously cut out all the lightning holes in his stack-o-ribs...When he finished..His Wife (also helping with the build) picked up all the cut-out pieces and put them on a digital scale......They weighed 3oz...lol...He described it as one of those "I Told Ya So" moments...

Maybe ED has a point??

Have Fun...

Chuck

edit: Nathan...Your right about dhal22's thread...Sorry..
Old 08-06-2007, 10:48 AM
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Default RE: anyone building a king kobra?

The other marks on the wing are where the ailerons will be shortened to add flaps. Again, a lot of this is for building practice. I have been assured that the plane doesn't need flaps.
Old 08-06-2007, 11:00 AM
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Default RE: anyone building a king kobra?


ORIGINAL: Ed Cregger

I wish one of you "honeycomb" fans would weigh all of the pieces of foam that you have removed from the wing and report the weight here. I doubt there is a 1/2 ounce of foam to be measured. Yes, the glue not glueing those sections "could" decrease the weight some, if you put the glue on the honeycomb and not on the wing skins. I've never understood the fascination with this technique, especially after seeing more than a couple wing failures because the honeycomb process weakened the structure to the failure point.

I'm not trying to start a fight, just a discussion. No offense intended.


Ed Cregger
Ed,

The 2M pattern guys can remove more than 3oz with this technique. Combined with careful glue application and wood selection, you get much lighter wing panels and this makes for a plane that rolls, snaps and spins more accurately. Care is required to leave enough support near the wing root and around retract mounts, but it is worthwhile for that last few percentage points of performance. Looks really cool, too!

Back to the KK build now.

Mark
Old 08-06-2007, 12:17 PM
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Default RE: anyone building a king kobra?

i just appreciate the fact that there are people out there who love this hobby enough to read and post on this thread. Extreme weight mgment has not been a huge concern for me yet. i am adding a few things that will cause the weight to go up a little but i am learning a lot with all of the time i spend reading other builder's threads. So the next one I will spend more time on weight mngment.

thanks again
Old 08-06-2007, 11:18 PM
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Default RE: anyone building a king kobra?


ORIGINAL: mmattockx


ORIGINAL: Ed Cregger

I wish one of you "honeycomb" fans would weigh all of the pieces of foam that you have removed from the wing and report the weight here. I doubt there is a 1/2 ounce of foam to be measured. Yes, the glue not glueing those sections "could" decrease the weight some, if you put the glue on the honeycomb and not on the wing skins. I've never understood the fascination with this technique, especially after seeing more than a couple wing failures because the honeycomb process weakened the structure to the failure point.

I'm not trying to start a fight, just a discussion. No offense intended.


Ed Cregger
Ed,

The 2M pattern guys can remove more than 3oz with this technique. Combined with careful glue application and wood selection, you get much lighter wing panels and this makes for a plane that rolls, snaps and spins more accurately. Care is required to leave enough support near the wing root and around retract mounts, but it is worthwhile for that last few percentage points of performance. Looks really cool, too!

Back to the KK build now.

Mark

------------------


The first time that I showed up at the flying field with a new pattern model featuring a servo in the wing for each aileron, I was told that my patternship was substandard and would never perform rolls crisply enough for competition flying because of the added weight in the wing panels. This was around 1982 or so. <G>

I have never seen a King Kobra "in the flesh", though I have long admired its great looks in the magazine ads, etc. I wish you the best of luck with your project and will cease to drag your thread off topic. Thanks for your patience.


Ed Cregger
Old 08-07-2007, 06:04 AM
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Default RE: anyone building a king kobra?

You guys are being too nice. I could, i suppose, turn this into a build thread. But the original post was just a fishing expedition, i was looking for ideas and recommendations to compare to mine. Please don't worry about steering this thread in the wrong direction, you're not. I appreciate the ideas that have been posted already. Now that i've spent some time perusing the classic pattern forum, i realize there is a lot of interest in this area of rc. I am glad to post progress photos if there is enough interest.
Old 08-07-2007, 06:42 AM
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Default RE: anyone building a king kobra?

I for one would love to see the build as you do it. Post all the pics you can
Jack
Old 08-07-2007, 07:22 AM
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Default RE: anyone building a king kobra?

well, i will upload some photos then. of course they will be midproject though.
Old 08-07-2007, 08:58 AM
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Default RE: anyone building a king kobra?

BUILD THREAD!! BUILD THREAD!!

My restoration thread started with two questions and ended up being a long thread, so it wouldn't be the first time. In fact, I think they're all sick of me now.

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