gard72977

My Feedback: (3)

I would like to start a 50cc project but not sure Im up to scaling up all the structure without help. I have been thinking of using two 1/2 in fiberglass tubes in each wing. Would be built like the wings on a .25" jig except the tubes would stay in and join with 7/16 tube on the inside. ( measurements are approx, I have some tubes from scratching profile planes) I am decent with Turbo cad and have scaled up a rib for 100" wing span. Just need advice on what type of wood (balsa ,bass, or lite ply) to make the ribs from. Im looking to buy some wood and start the wing now. Any help would be apperciated?

doxilia

My Feedback: (3)

If you scale up the plans, what's the thickness of the resulting ribs?

What material you make them from depends a bit on how much you lighten them. Off the top of my head I'd think that something like 1/8" or 3/16" balsa or 1/8" lite ply would work. You could also use CF hollow spars or if you go with the FG tubes, basswood spars.

It might also be worth having a look at the large chaos plans sold by bluejay with the kit.

David

Trisquire

I would use a 50cc IMAC plane as your reference in terms of construction materials/wood dimensions, etc.

gard72977

My Feedback: (3)

I would just buy the Blue jay kit if it was availible and build a 30cc but it has been out of stock for sometime. I do want to build light but Im not getting obessed with it. I dont want this to be a floater. I need a good reccomendation of rib thickness so I can get started. Im thinking of a combination of lite ply andbalsa. I was thinking of the fiberglass tubes because they are 53" and would make a great jig for building the ribs. Im going to work on enlarging the ribs and placing the holes for the tubes on a tempate and go from there.

doxilia

My Feedback: (3)

If the tubes are longer than each panel you could use them as the main structural spar. Then for ease of building I would add a top and bottom 3/8 square spar on to which you would glue shear webs in between each rib pair. I'd place the glass tubes right behind the D-tube section. The nice thing about the Kaos is that having a flat top wing you can join the panels with a straight inner section as you propose.

I would use 1/8 medium balsa for the ribs with the LG carrying ribs doubled with 1/8 aircraft ply - unless you plan to go with fuse mounted conventional gear...

Use a stiff (perhaps basswood) TE spar, a stiff sheet sub-LE and a softer LE. 3/32" sheet balsa for the wing sheeting.

I guess you've already thought about the ramifications of a single piece 100" wing...

David

speedracerntrixie

My Feedback: (29)

I would take the easy way out and do a foam wing. For a 50cc airplane a 1.25" wing tube would be the ticket. The tube and sockets can be ordered from TnT and the wing can be sheeted with 1/16 balsa and called done.

bjr_93tz

I'd agree with this.

See if you can track down someone who has a busted up ARF extra or edge that's about the same size as you want to build the Kaos and see what's under the wing covering.....

gard72977

My Feedback: (3)

The wing will actually be a two piece wing. I would join the wings with the fiberglass tubes and bolt them to the bottom of the fuse.The wings would actually bolt to each other then to the plane. Since I would not have the larger gap between the wings like a edge or extra I was hoping I could use dual small tubes. My idea was to also use the tubes as part of a jig. I could also use a ply mount that attaches to both of the tubes for the landing gear mount. Just some ideas

MarkD

I looked at this a few years ago after I built a 180 FS powered S. Kaos (75" WS).

As I recall the original SK wing thickness was 19% at the root and 17% at the tip.

I drew up a set of CAD plans using the artical in M.A.N. as a guide. I used their material call outs and ended up with an overweight, though immensly strong plane. I could easily build another that would weigh 2 pounds less.

Built as a tail dragger, the wing will have to take a lot of load. For built up I would go with 3/32 or 1/8" lite ply ribs (lots of lightening holes), built-up spruce/fir spars, a 1/8" basa sub leading edge, 1/8" balsa sheeting and cap strips.

At 90" WS/1500 sq. in the fuselage cross section is only about 6.25 " square. You'll need to keep it stiff without a lot of weight. I would go with 3/32" light ply for the fuselage sides (lots of lightening holes), 1/8" hard ply doublers for the forward fuselage a 3/16" balsa top deck. I would add 2 extra fuselage formers to the aft section as well as using some spruce/fir longerons( maybe 3/32" thick x 3/8" to 7/16" deep)

You could certainly use balsa for the sides. but you will be gluing up a lot of sheets to get your blanks. With the cost of balsa, the ply may well be more economical.

The attached picture gives an idea of relative sizes.

Mark D.

MTK

A 50 cc sized balsa and ply plane doesn't need to use any more bracing or size/thickness than your typical 30cc model would, or YS170 powered model. There is nothing magical about the 50cc engine size.

For example, I outfitted my EF 78" Extra witha DLE55 and then put a pipe on it. If you ever saw an EF Extra you'd know what I mean about techniques and material you would need....extremely lightly build. This model's all up weight was 12 3/4 pounds....with 6+HP up front. The joiner tube was a standard 7/8" carbon. Wing area is around 1250 squares. The only special thing I built for the airframe was a soft mount for the engine. Yes, you can soft mount a gasoline engine the same as you can a glow engine. Been doing that for a long time

BTW-This combo was outfitted with a Mezjlik 20x12 3 blader for extreme quietness. Definitely electric like in quietness.

What you don't want in my opinion is a model that weighs in at 22-25 pounds powered by a 50 class engine. Just not enough beans in such a set-up to get great aerobatic performance. So I'd suggest not using the standard techniques and scaled up materials used on the original Kaos. You would get a pachyderm of a plane and you might be disappointed in the performance. Think a little outside the box and build a model that is strong yet very light....instead of thick balsa fuselage, consider carbon tubing stringers and lite ply formers/bulkheads. Conventional wing construction doesn't need thicker rib wood than 3/32". The glass tubes you want to use will work, except having these go out to the tips adds unecessary weight.

Lightening holes everywhere should be employed. Or foam veneered with balsa would work fine..... 1/16" balsa not 3/32" or thicker. That's my 2C

doxilia

My Feedback: (3)

That's pretty funny Matt!

A platybelodon comes to mind!

David

Trisquire

Here are some construction pictures of a 50cc plane. It should get you in the ball park.

http://www.ohiomodelplanes.com/92edg...ual/index2.htm

Tom

gard72977

My Feedback: (3)

Thanks for the information. This is my first large build. Is the 100" mark right for a 50cc Kaos. I have taken the 60 size kaos cad plans and enlarged the ribs and working on changing the size of the spars and adding the holes for the tuubes. After reading all the info Im going to make the tubes go in to the first 4 ribs. I will post some drawing when they are done.

gard72977

My Feedback: (3)

This is number 10 rib have been working on. I will run the fiberglass tubes alll the way to the end of the wing and only glue the first four ribs. the tubes wll be cut and removed fromt he last six ribs after the wing has been built. This will work as part of the jig. Im thinking of using a balsa spar and milling a slot in it and gluing a .25 carbon fiber tube in it. I was thinking of making ribs 1 through 4 with 1/8 lite ply and cutting some lightning holes in them. Just wanted some suggestions before I rework all 10 ribs.

MTK

Gard,

Carbon tubing will make exceptional spar stock. I'd suggest that you forego the balsa and use the carbon tube only. You could use 1/4" x 1/32" for the main spars and 1/8" x .015" for the rear spars. Since you are drawing the ribs in CAD, you could have a laser cutter cut the ribs exactly to spec. Don't forget to roughen to carbon spars such that super glue has good bite. The only ribs that should be lite ply are the center and the gear ribs. I assume that you will use retracts on this bird.

A simple technique if you use retracts is to lengthen the struts using carbon tubing. I use .280" x 1/16" which fits a 5/32" shank just right. The steel shank only needs to be about 1" long; epoxied in place. I also install a 1/2" long length of aluminum tubing around the carbon tube at the epoxy area, to keep the carbon from splitting

If you don't plan to use retracts, don't bother with ply ribs either.

Man that's a thick wing

doxilia

My Feedback: (3)

Yea, same thoughts. That's the first thing I would change if building a Kaos, especially this size. I kept the existing airfoil but reduced it by 20% - in a drawing. Not sure how well it will work but there's nothing like experimentation.

Matt's ideas for the spars strike me as good ones. The balsa becomes redundant if using CF. Another option would be to use hollow rectangular or square sections of CF. It strikes me as it would make a massively strong wing. In the much smaller wing I drew up, I went with spar doublers in typical Japanese MK style. The spars are thin but they are doubled for about half the panel span. The joint makes them very resistant to bending as the grain is locked in place by the glue so they can't slip with respect to each other.

Another very cool wing building design concept is to use interlocking shear webs (see last picture). The webs lock the ribs and spars together practically without glue. The webs also produce the dihedral required by design. With a flat top wing, only the bottom of the webs would be tapered while the top two corners would be at 90 degrees. I think the easiest way to build a Kaos wing is to build it inverted flat on the table with the rib center lines parallel to the surface.

David.

MTK

David,

Nice drawings. I agree on the reduced thickness. Didn't realize you had CAD capability. Can you draw up a wing to my design specs (pricing? PM me please)? I would want to have a couple sets of ribs laser cut. That's to prove a point between foam/balsa versus built up ribs.

Be careful of the interlocking but glueless shear webs. I really like the interlocking feature but I would glue them to the spars and ribs. I don't think you want shear webs to float against the spars and ribs. Vibration will wear the contact points out fairly quickly

gard72977

My Feedback: (3)

This plane will not have retracts. carbon in lengths of 50" is hard to find. I was planning on using arrown shafts and machining a piece of aluminum to join them. The reason for the balsa was to gule the carbon in a slot and then the ribs would glue to the balsa. Not sure I want to laser cut anything. I get a lot of satisfaction out ofcutting andbuilding my models. This is not going to be a expensive build. I plane on using a cheap chinese 50cc and medium grade servos. Im not lookingfor unlimited vertical.I moved to Tupelo and there is a great flying field here. Its a sod farm and everyone has large planes. I usually fly smaller planes and most of mine are profiles. I just cant afford a 10k airplane like the other guys. I just want a large scratch built plane that is different than everyone else. I dont get a lot of satisfaction form a Kit and almost none from a ARF. This plane will be on and off the building board for a while. I actually have plans for a 60and 90 kaos that will fly before this one. (the plans for that 30 are very tempting!) I want a little time with a Kaos beforeI maiden a 100 " scratch built model. I love the look of old pattern plans and want this 50cc plane to be simple and fun to fly. Reducing the wing thickness by 20% percent should be easy enough.Since im notusing rectracts this seems like a good idea (less drag). The wing will be built on a alum plate with fixtures on each end to hold the twofiberglass tubes.

Is the idea of the arrow shafts in a slot in the balsa spar ausable Idea ? Since no laser cutting the top of the spar could be sandedto match the ribs for any inperfections.

I really apperciate the feed back. I enjoy the building more than the flying.

MTK

Gard,

In a medium like this one, you can't tell who knows what they are talking about and who doesn't. I too am a builder/designer at heart so can relate precisely to what you're talking about.

Trike or conventional landing gear? If conventional, fuse mounted or wing mounted? Makes a difference in the design of the mount you build in.

The tube in the balsa is fine and will work great....just heavy is all. You are correct, 50" carbon tubes are not a simple find, but 48" lengths are. Look at ACP website. Doubling that gets you close and if you include the tip blocks you will make 100" on the button, assuming it's a one piece wing. You could design the wing as a two piece x one piece, meaning it is connected in the middle witgh a carbon tube, or as a two piece where you have a joiner tube through the fuse. If the latter, your span will exceed 100" if you wanted

gard72977

My Feedback: (3)

I am wanting to do trike gear and wing mounted. I want it to ba a large version of a 60 size.I have a idea of how I want to do the mounts for the gear in my head but i want to iron out the rest of the wing first.. Is weight going to be that big of a issue. Im not wanting to build heavy but i dont want a plane that is floaty. I like the idea of the 48" carbon spars. Im just not sure if I can designa rib with a carbon spar with out the balsa.

gard72977

My Feedback: (3)

Well I guess I have enough info to start my drawings. I have decied to use a 3/8 balsa spar laced with a .25 carbon shaft. And one .25 carbon shaft in the rear without balsa. It will have a balsa trailing edge for the hinges to attach. This is not a high tech build. I am on a budget for this one. I will keep it as light as possible and may usea limited amount of CF in the rest of the build.The landing gear will be wing mouned and I will machine a oleo type strut. I dont want something intrusive here. Front will be the same. I just want typical Khoas performance not looking for unlimited vertical. I will post some pics of drawings before I order anything. thanks all for your help.

I know I may be jumping the gun starting a large model but I want a 50cc and this makes the most since to me.Because I have never flown a pattern plane I want to get a small one and get some stick time. What birdi from blue jay would you reccomend Sun fli 4 (40size) utter choas (40 size) or the utter choas (60 size) I have plenty of gear already for either size. I have a few sets of plans but I dont want two scratch builds going at the same time. I just want to get a kit in the air quick.