Kaos 90

This large, impressive plane was published in Model Airplane News in 1984.  It looks like a giant version of the 60 size Super Kaos published in RCM.  The plan shows a foam wing core fully sheeted with 3/32″ balsa, with hardwood blocks for landing gear attachment.  My short kit has a built-up balsa wing with 11 ribs on each side, plus plywood rib reinforcements for the landing gear blocks.

Leading edge is 3/8″ balsa.  Trailing edge is 1/4″ balsa.  Spars are 3/8″ x 1/2″ hard wood, either spruce or bass. Landing gear blocks are 1″ x 1/2″ hard wood, 6 inches long.  Please specify nose wheel or tail wheel when ordering, so I can cut the correct ribs.   When you build your wings, the rib spacing is as follows.  Starting at the root, the space between the first two ribs is 2.25 inches, the next space is 2.5, then 3, then 3 again, then 4 for the remainder of the spaces.  You can get the plan printed, and draw the wing rib locations on the plan if you think it would help.

The ribs are sized for 3/32″ sheeting.  Scaling the dimensions up from the 59″ Super Kaos plan, the trailing edge sheeting would be 2 1/4″ wide.  Leading edge sheeting extends from the leading edge stick to the spar.  Or you could just go all out and sheet the whole wing for extra strength.

The fuselage top is labeled 3/8″ balsa on the plan.  If I have good 3/8 on hand I will use it.  Otherwise it will be cut from two layers of 3/16 to be laminated by the builder.  In any case, it is split into a front piece and a rear piece, because the total length of this part is 55 inches.  I’ll include a little piece of 1/32″ ply to scab over the joint.

You build the horizontal stabilizer.  I supply the fin, rudder, and elevators, all to be laminated from parts half as thick as noted on the plan.  But there’s something funny about the plan.  It shows the stabilizer saddle cut into the fuselage sides, because the stabilizer at 7/16″ thickness is thicker than the top fuselage longeron, which is 3/8″.  So far so good, but the plan directs the builder to cut the elevators and the filler block between the elevators from 1/2″ balsa.  I can cut them from two layers of 1/4″, which means you laminate them and sand 1/16″ away, or I can cut them from one layer of 3/16″ and one of 1/4″.  You laminate them and they will be the correct thickness.  Sounds like a better option to me, so this is what I’ll do unless you have a better idea.

One other thing:  Maybe you’ll tilt your engine sideways, inverted, or whatever.  So you’re on your own with the cowl.