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Old Feb 17, 2015, 07:14 PM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
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Scratch Building a Two Meter Kaos

The Kaos is a very special airplane that has been around since 1970. Anyone who has ever watched an accomplished pilot flying one has wanted one. Kits have always been available. ARFs came along later. They fly so smooth that they make the average sport flyer such as an Ugly Stick look spastic when it is in the air. Since the Kaos is one of the earliest of the pattern planes, to me it's considered the grandfather of them, and 40+ years after they first became available, they still are competitive in the early pattern classes. Perhaps the reason for its success is the fact that the while in the design of most aircraft the fuselage is 75% of the wing span, yet the Kaos I have plans for has a 58.5" wingspan and a 54" fuselage, so the fuselage is 92% of the length of the wingspan. Over the years pattern planes have eventually grown to where the length of the fuselage is longer than the span. This greatly contributes to the aircraft flying on heading better, or more fittingly, the term "flys like an arrow."

Kaos, Super Kaos, Extreme Kaos, Chaos, Ultimate Chaos, Killer Chaos: Just what the heck is the proper name of this bird anyway? And what are we supposed to call it? Why so many names?

I built two in the past. Since I have been a scratch builder most of my RC life, I never build anything the right size. Maybe I am just a lousy pilot, but to me, bigger flies better. My first Kaos, built in 2/84 had an 84" wingspan and was powered by an OS piped 90. Weight was about 12 pounds as I remember so giant loops were not on the flight schedule. Every time I took it out to the flying field, all the guys would line up for a few moments at the controls. It flew 'like an arrow', and was a true joy to do touch and goes without ever touching the nose wheel. The roll rate was too slow, but remember, those were back in the days when a single underpowered servo ran both ailerons. Even so, it did beautiful 4 point rolls. I think the reason my friends wanted a few minutes on the sticks was they knew I wasn't as good a pilot as the Kaos made me look, so they wanted to see for themselves.

You know how our fond memories from the old days are never forgotten, and probably embellished over the years. I missed the old Kaos that I flew for around 4 years before giving it to a friend, so 1/03 I built another similar plane, this one eloquently named, "Big Pattern" in my record book. 82" span, 10 lb., 1250 square inches. 18.4 oz. wing loading. Been flying the crap out of it ever since. Bigger control surfaces, two ailerons servos and a computer radio make it a very modern version of the previous Kaos from 21 years earlier. Powered by an OS 1.08, it flies very similar to the Kaos, even now that we have moved to New Mexico where our flying field is at 5340'.

I just finished a scratch of a 72" Top Flight Contender, 7 lbs. and also powered by a 1.08 2c. It is waiting for its maiden flight. Any day now… But, the workbench is clean, a blank piece of paper is taped down, and time for the next build. I've been on a building jag since last spring, replacing many old planes with five new ones, and still not done. Just having too much fun! However, the Contender was a bit more complicated than my more usual fare, so I'm ready for something a little more on the simple side. How about that 2 meter Kaos I've been thinking about?

I'm sure a blank drawing would scare the bejesus out of those not used to scratch building, but for many of us old timers it is just an invitation to let the fun begin. Notice the balsa supply is in reasonable shape, so let's let the fun begin.

For anyone interested, here are some links to my recent scratch threads. The Kaos will be built using similar construction. 90" Sig Kadet

76"Tiger


102"RCM Trainer


72"Contender
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Old Feb 17, 2015, 07:20 PM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
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First thing needed to start marking up a blank sheet of paper is a plan. I just happen to have a plan for a Super Kaos 60. (1973 ) Also have a small 8x11 plan for a Kaos 90 from Outerzone. Also been doing a little research, and plotting some minor changes I will make to the newest version. Always wanted to have a new 2 meter pattern plane. Just love watching them fly at contests. No, my contest days are over, but I still like to watch. But it will be a cold day in you-know-where before I spend upwards of $2k on a plane that could have a mid-air any day. Most of my builds cost under $100 for balsa, ply, glue, and covering. Compare that to $500+ for an ARF the same size…

Have a Super Tiger 2300 (1.41 cu. in.) I just took out of the drawer and mounted to a test stand. Over the years I have morphed away from liking real thick wings. Too much drag uses up too much power. Look at the wing thicknesses of the newer pattern planes. Did you know the Kaos used a 20% airfoil? On this build I plan to use a 14% root and 12% tip, and 38% back at the high point. Also making the tip cord a bit smaller for a better roll rate , along with 3" wide ailerons.

Last but not least, the two meter plane will have a 78.5 in long fuselage, and a 77" wingspan. Projected weight will be in the neighborhood of 8 pounds. Plan to have the plane done and flying before we leave on a month long RV trip at the end of March.

Love to chat. I'm retired with nothing better to do but to build and try to encourage other flyers to give building a try. Happy to hear your comments and encouragement, even if you tell me it is sacrilege to mess with the Kaos design. Well boys, even the vintage flyers can use a bit of a facelift now and then.

By the way, kept wondering what a Killer Chaos was, so Googled it to see. Can't post a photo that is not mine, but can say that my rudder shape that was drawn to the old Kaos style will be getting a face lift. The antique design definitely needs a redo in my silly opinion.

Out of town tomorrow, so will start making balsa dust on Thursday. Glad to have you join in.

Tom
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Old Feb 17, 2015, 07:24 PM
AndyKunz's Avatar
Illinois
Joined Sep 2001
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You'll love it, I know! I'll be following this thread. I rebuilt the wings for a friend who had a 96" Kaos - he flew it too close to a post and the post one. Sheered everything off about 6" from the fuselage on the one side.

I can't wait to see yours come together!

Andy
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Old Feb 18, 2015, 12:23 AM
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Brilliant, this will be fun, subscribed .
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Old Feb 18, 2015, 08:44 AM
iFly/Hobbico R&D
Spain, PM, Sóller
Joined Aug 2006
118 Posts
Nice, I've always wanted to do a very large pattern plane myself. Perhaps in the 100" range. Oh well, some day...

Hey, just a quick comment about your airfoil selection...be careful with a thinner tip airfoil than root airfoil. The Kaos has some wing taper already which will help the plane to have the stall behavior it needs to behave as a proper pattern plane. Having the thinner wing tip will just make that behavior more pronounced...perhaps too much. You do not want to end up with a plane that tip stalls too easily.

Good luck

Sportjet
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Old Feb 18, 2015, 05:14 PM
Scratch Builder
tomclark's Avatar
United States, NM, Deming
Joined Apr 2014
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Hi Sportjet,

You are right about really thin wings with heavy wing loadings, so thanks for your concern. But, look at the newest pattern plane photos from magazines and the web. Notice the airfoils they are using. Many tips are very thin.

Actually, I have been flying 16% roots and 12% tips for many years now. This pattern is 9 years old, and that is the wing configuration. Plane is 67" span and 65" fuse. There is a huge difference between planes with 25+ wing loadings and the light weigh planes I build.

Also, though I no longer fly competitions, I do enjoy watching the masters fly. Many of their maneuvers have required snaps in the middle of loops, rolling circles, 45˚ up and down lines, etc. The big Kaos will be very light with the wing loading well under 20 oz. per sq. ft. so it will have a hard time doing snaps on command.

Well, time will tell.
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Old Feb 18, 2015, 07:09 PM
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Oh, I woudn't be so sure of that. The high percentage thickness may make the wing difficult to stall, and a snap entry may be hard, but It should snap provided it's been trimmed to do so. You have have to put stall strips on it, you may not.

Granted you won't get the kind of snap Andrew Jesky will do, but it'll snap well enough to please you.
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Old Feb 19, 2015, 06:32 PM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
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The weather around here has just not been very good for building lately. My brother-in-law has 18" of snow on his farm outside of Lexington, and the TV news keeps showing the record snowfall in Boston. I mean, building season is supposed to be in the winter, right?

So why do my flying buddies keep calling and saying let's go flying? Today was perfect flying weather. 68˚ and a 5mph breeze right down the runway. I had a new plane ready for it's test flight, and had just retired my last 72 radio and replaced the receiver with a new Tactic 8 ch 2.4, so I was anxious to test fly the Contender and get my favorite old pattern plane trimmed out - again. Started out with a light jacket but in no time was down to a T-shirt.

Bottom line, can build some other time… The flying was great. (Go ahead and throw rocks.)

I did get back to the workbench late in the afternoon to get ready to rip some sticks and build the elevator and rudder. Hey, forgot to draw out the elevator, so started there. Then glued up the rudder and it's dinner time. Boy does time fly when you are in the shop and having a good time.

Will start posting some serious building pretty soon.
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Old Feb 20, 2015, 07:07 PM
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I'm subscribed

Michael in Newmarket, Ontario, Canada
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Old Feb 20, 2015, 09:44 PM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
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When reading on the RC forums it is funny how you read over and over how people just don't have time to build. I guess the impression, especially after looking in on some threads how the build goes on for months and months, is building takes forever. I love building, but there is no way I ever spend all day in the shop. My building time is usually a couple of hours here and there. Today was very nice weather again, so the wife and I walked 18 holes at the golf course this morning. Great exercise and fun! I hit the shop for a few hours afterwards.

Today was a slow day, where you spend more time thinking than actually doing. Ripping some sticks and gluing up the elevator goes quickly. When the glue had set up a bit, the parts were unpinned, and rough sanded a bit. The outer edges are 3/8 x 3/4 wide, larger than usually used for tail surfaces. The Kaos will be flown harder and faster than my usual sport fliers. The sticks positions are not measured out. I just eyeball the position and glue them in. This is not rocket science, and having them in an exact order is only to suit those who must have everything exactly even - not me. They become invisible when covered, so it really is irrelevant where they go, as long as the structure is strong and stiff.

Next I had to call out my kit cutter. It was made by Dremel over 40 years ago. It usually sets on a small shelf on the side of my small workbench, but when cutting bigger pieces it can be set anywhere. I ripped and glued together four sheets, so they will cover the area around the firewall and over the wing saddle. This takes time as you decide just how much wood you want to put in each area. I start off small, as more can always be added to where any place might be subject to a lot of stress.

Believe me, it is harder to explain than to do. It does take up a lot of time, this thinking business, but this is the part of scratch building that to me is somewhat like why some people work crossword puzzles.

After tomorrow's build it will make more sense than the photo shows now. Here I used CA thick, so glue is dry instantly, and then glue together enough wood to make the second side. I trace out the outline of the plane, then pin the two sides together and cut them both out at the same time, so they are identical.

The two plywood airfoil patterns were cut out a couple of days ago. They are just rough sanded and will be refined when finished. They are needed ahead of time so you can trace out the area where the wing saddle will go. I'll build the wing as soon as the fuselage is mostly done, and will go into detail at that time. For now, the base rib is 14% of the cord, and the tip is 12%. The high point of each rib is 38% of the way back from the leading edge. The top of the each rib has a very slight curve to it, and the bottom of the rib will have a slight flat , less than 1/16" of an inch difference. Once again, beginners stress themselves out over airfoil shape, but believe me, it is just not super critical.

Photos will make the fuselage construction seem very simple, and wing photos will make that much easier to understand also. If you're in a hurry, check out the fuse construction on this link. It will help to make a little sense of my ramblings.

By the way, started a list of how much balsa is going into this build, and will give a report at the end when done in about two weeks.
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Old Feb 21, 2015, 01:15 PM
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United States, NM, Deming
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Stick building is quite simple and fast. The plans are just outlines, and the sticks are cut out and laid over the plans and glued in place.

The fuselage will be 78.50" long spinner to rudder, and of course the sticks are not that long, so you have to use multiples on larger fuselages. Every place sticks are joined, they are just butt glued and then 1/8" light ply reinforces every joint.

After the first side is glued up, it's flipped over and the second side built on top so they match. There is nothing critical about where the vertical and diagonal sticks are placed, so I don't bother measuring and just glue them in by eyeball. Works for me. On planes that use transparent covering a little more care is taken for appearances.

Next up is putting the two halves together and epoxying in the firewall, and plywood parts for the landing gear, wing blocks, and wing dowels.
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Old Feb 21, 2015, 09:34 PM
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United States, NM, Deming
Joined Apr 2014
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The fuselage is not finished, but made some progress today.

Epoxy is used in places where the most stress will be. This piece of 1/4" ply will eventually have the wing dowels in it. It is epoxied to a plywood vertical pieces to spread the the stress around, and the landing gear plate will be epoxied to that after the wing dowels are drilled.

I like plywood motor mounts. They eliminate a lot of vibration. Blind nuts will be used to make it easy to remove the engine for maintenance. I used about 1/2˚ of down thrust, and 1˚ of right thrust.

These blocks will be drilled and threaded for the wing bolts, so they are epoxied to the fuse sides and a plywood plate.

The last photo shows plywood triangles also epoxied in place. The landing gear will not be coming off even after the first 10,000 touch and goes.
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Old Feb 22, 2015, 04:57 PM
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United States, NM, Deming
Joined Apr 2014
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Of course the reason to post build threads is to show others that building is fun, and it really doesn't have to take months to scratch build an airplane. Check the dates on these posts. Started on Tuesday, and on the following Sunday the the tail surfaces are mostly done, and now the fuse is nearing completion. Sure, nothing is finished sanded, and will add a few sticks here and there - it is so easy to change your mind when you look back on what you have done.

Don't start laughing when you see the foam canopy that is just starting to take shape. It has a long way to go, unless some one can point the way to a really cool looking plastic canopy about 22-24" long. The rest of the plane is starting to look good - or at least as good as a naked Kaos can look without it's canopy.

The motor mount has the blind nuts installed and is ready for fuel proofing before the bottom sheeting is installed.

No sheeting on the bottom of the fuse, so there are a few places for the covering to be ironed down.

The servo mounts are cut into the back. Hardwood blocks are glued in and the area soaked with CA for strength.

Dropped the old Kaos tail shape. My apologies to the purists.

The fuse has just a bit to go and then time to start on the wing.
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Old Feb 22, 2015, 06:46 PM
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Great work you are doing here, always wanted to try a project like this.
Looking foward to the rest of the build.

Dave
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Old Feb 22, 2015, 06:55 PM
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Subscribed. I have a feeling this isn't the first time you have done this
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