Super-Fli Build

The Kraft Super-Fli is one of my all time favorite aerobatic aircraft. Its clean, simple, elegant lines convey one purpose, and one purpose only—aerobatics! Besides, it’s just a great looking aircraft. Designed by Phil Kraft, World Champion pattern flier and R/C model aircraft designer, the Super-Fli is the culmination of a model designers dream to design a full scale competition aerobatic aircraft. The plans used for this build were purchased from Model Airplane News. Dan Lutz, builder of the prototype model says the Super-Fli is a “piece of cake to build, simple and strong”. While I agree that the model is simple and strong, and consists of few pieces, the “piece of cake” part depends on how well versed one is at cake making. A sheet pan cake is far easier to construct than a 5 tiered decorated wedding cake. I judge the Super-Fli build somewhere between the two mentioned cakes, a sort of Black Forest cake made with fresh cherries. If you’re versed at composite construction using Styrofoam, bending gear wires, vacu-forming your own canopy, fabricating wheel pants, and building a wood cowl, it’s not that bad. I would rate it a 3 to 3.5 out of 4. Although the Super-Fli was kitted by Bridi Enterprises, Great Planes, and a few others, there are no ready made parts available that I know of. The Goldberg Ultimate wheel pants look like they are a good fit for the Fli, and can be purchased from various sources, but that’s about it. You must construct everything else. The supplied build article was rather short on photographs, and the plans could be more detailed about a few items, but both are adequate for the experienced builder. Not wishing to write a complete step by step article regarding the build, I’ll post some photographs and comments to help clear up any areas the plans and build article didn’t include. Also noted are some areas that caused me to engage in more head scratching than actual building!

Fuselage Side View

The 3/8 fuselage side panel will take

considerable sanding to match

fuselage contour. Sheeting around

cockpit is very fragile! I finally used

epoxy resin and micro balloons to

help strengthen it.

Tail Wheel Assembly

A Dubro tail wheel assembly is used. The plans show the plywood tail wheel mount on the inside of the balsa tail post. I opted to extend the plywood tail wheel mount across the whole bottom fuselage and through the tail post.

Engine Mount and Mount Box

Ready for installation, a Dave Brown .60 engine mount is mounted to the engine mount box. The box is then epoxied to the plywood firewall with triangle stock for extra strength. Small squares are velcro used for temporary cowl mounting.

Wing Fuselage Cut Out and

Ply Facing

A rather hefty chunk had to be cut from the leading edge of the wing for fuselage fit. Go easy with this cut and sand a little at a time to fit fuselage! The final relief tapers slightly from top to bottom of wing and from the leading edge rearward. Also, there is no plan template for the 3/4 ply facing and must be cut to fit wing once fuselage fit is OK. Note slightly tapered center rib for wing dihedral.

Wing Belly Faring

Landing gear chin block is tack glued and sanded to shape. The plans showed the wing belly pan carved and contoured from a single block like the one above. The block route was far more work than I wanted to deal with so I decided to fabricate the belly pan a different way in the next photograph.

Aileron Removed and Bell

Crank Mount Hole

The wing tips were tack glued and sanded to shape. After making the aileron template, ailerons were cut from wing using a Xacto saw blade. Aileron bell crank Nyrod control rods were added to the wing and bell crank mount hole cut out. A 1/4x1/8 spruce spar was added over the Nyrods and epoxied in place. Relief was then covered with 3/32 balsa strip and sanded flush. The spruce spar was not contained in the plans.

Belly Faring and Gear Block

I cut 3, roughly 1/2 pieces, to fit the

wing contour and then sheeted over

the pieces with balsa to finish the

wing lower pan. The gear chin block

had to be cut completely through and

areas relieved to fit around the

landing gear wires. Relief areas were

then filled. Gear looks weak but once

soldered is very strong. Gear mount

block grooves were filled with JB

Weld after gear was installed in block

grooves and secured in place with

steel straps.

Tail Section

The horizontal stabilizer does not extend to the rear of the vertical fin. Note the area in front of the horizontal stabilizer has been filled. The area behind the horizontal stabilizer still needs filling. Once this area is filled the elevator can’t be removed for covering! The area will be filled after the horizontal stabilizer and elevator are covered and the elevator is permanently hinged.

Completed Belly Faring and

Gear Faring

Completed belly faring with hole for wing bolt access. The plans did not specify the size balsa for use on the gear fairings nor how to mount them. I finally settled on 3/16 balsa sheet and glassed them with 2 o/z cloth. The gear fairings were attached using Goldberg 5/32 landing gear straps. A 90 degree bracket will later be added to the rear of the faring and mounted to the gear chin block. Wing center section has been glassed with 6 oz cloth.

More Tail Section Notes

Pay extra attention to aligning and

attaching the tail surfaces. The

horizontal stabilizer sits at a slight

angle. No specific degree angle is

mentioned in the plans but it’s about

1/2 a degree +incidence. Also, the

base of the vertical fin must be at the

proper angle so the top of the

vertical fin is level when the aircraft

is level.

Final Shape

Pants ready for glassing above. Once glassed with 2 layers of 2 oz cloth, the foam is dissolved and removed with about a tablespoon of acetone.

Wheel Pants

I used See Temp template material

to make all patterns for the Fli. Using

hardware store pink foam, the wheel

pant is rough cut to shape, then

sanded to desired contour with a

sanding block.

Build Continues...

Covering the Super-Fli continues on the next page. CLICK HERE

Cowl Side View

The cowl was constructed per the build article using the keel method. Once constructed and sanded, the outside was glassed with 3/4 oz cloth. The inside was reinforced with 2 oz cloth. Automotive primer will fill any low spots.

Ready For Final Sanding

The cowl has been shot with white automotive primer and sanded. Ailerons are quite large and should provide an exceptional roll rate. Styrofoam turtle deck was constructed gluing leftover foam from microwave oven packaging then sheeted with 3/32” balsa.

Wing Dihedral Note

Dan Lutz stated in the build article that a “little wing dihedral” was added to the prototype. The plans, like the full scale aircraft, call for none. Not knowing exactly how much “a little” is, I decided to add “a little” too. I finally decided on 3/8” inch at each wing tip. Keep in mind that adding wing dihedral will throw off the belly pan side dimensions in the plan because the underside of the wing will sit deeper in the belly pan.