Our Windrose project has been "on ice" a couple of years but now we have found some new inspiration to finish the work.

"We" are Anders Andersson and Jan Carlsson.

The first contact with the Windrose was in the Swedish gliding magazine Segelflyg sport's December issue 1985. With fresh Gliding License on the pocket we wanted to build and fly a motor glider, which will give us the opportunity to leave the sea breeze area and found good thermal. And fly on weekdays without a need of air towing.

The drawings was ordered in November 1986, but the building permit was delayed until the end of May 1989, due to questions about the rear fittings on the 13 meter WR. and questions about the spoiler effectiveness.

At this time the 15 meter Windrose drawing was published with a new designed rear fitting, and in general better design, and of course 10 units better performance.

So we are building the 15-meter wings with carbon fiber spars and 4130 steel main fittings. With 1° or 5 inch dihedral at the tip.

The templates for hot wire the Styrofoam was made of 3 mm PAPER BAKELITE, it's much stiffer and durable, and we used round 2.5-mm OD steel nails to fasten it to the foam.

The DB 170-50 Knytex (17 oz, 50 inch wide) needs to be just 1 layer. It is not a "BID" but a Double Bias, not woven, but two uni directed layers at ± 45°, hold together with sewing, it seems to be hard to work with, we didn't use it.

DB 170-50 Knytex is available at AIRCRAFT SPRUCE & SPECIALTY COMPANY, PHONE (714) 870-7551, FAX (714) 871-7289.

We used 4 layers (more time laminating, but less filling and sanding) of Hexcel 1018-TF970. Which add less weight and is stiffer. It takes about 4 hour to make the skin on one side for 4-5 men. The hardest thing to make is the carbon fiber spar. Making it takes a lot of time, 12-14 hour on 4 people, and it can't be rushed because it will exotherm, we used Ciba Gaigy's 5052-epoxy system. Use dish gloves or better gloves, over thin cotton gloves to protect your hands from epoxy allergy.

Our wing weight is 34 and 36 kg (left and right) no paint, but micro/epoxy filler at wing spar and at glass fiber lap's. Aileron is 3 kg each, and paint will add maybe 1-2 kg each wing, so max. 38 - 41kg each? Jim's calculations say 97.5 kg together. The Hexcel skin is lighter and we were careful with epoxy. (1kg = 2.2lbs)

We have done the proof loading of the wings and fuselage as well. Yes it was a thrill, with 1370 Kg of Weight (3020 lb.) on the wings it first seems to be unreal. But nothing broke, the wing tip's was bending 95 cm. (37")

The input data was MTOW 347 Kg, wing Weight 88.5 kg (corrected for non-spanwise weight distribution (wing fittings)), and 5.3 G load factor, to match JAR 22.

Irv Culver says; C_L max. 1.5. C _La = .100972 per degree. C_D0 at C_L max. = .012. C_M = .003

I divided the half span in 10 segments equal length! From centerline to tip.
Maybe you are not familiar with meter and kilogram so I will recalculate it.

B/2= 293" /10=29,3" per segment.
TOW=765 lb. - 195 lb. (wing weight) = 570 lb.
5.3 G's * 570 lb. = 3021 lb. /2 = 1510.5 lb. each side.

The wing has no twist so the load is divided equal per sq. feet.

Sta./lb. 1=209.5 2=198.4 3=187.4 4=176.4 5=165.4

Sta./lb. 6=154.3 7=137.8 8=115.7 9=93.7 10=71.6 (=1510.2 lb.)

You can reduce the weight near the tip to take in count the fact the losses from tip vortex. If you have other MTOW and G load's just recalculate the figures with the same % differences.

Like this; if you just want 4 G's, 4/5.3 = 75.5%, so sta. 1=209.5*0.755 = 158.2 lb.
we used "sand blasting" steel powder (don't know the right name in English) it reduce the volume so it is easier to handle, used 2 or 4 bags on each segment.

It is also important that the fuselage is allowed to move or roll along the lateral axis. We used two sets of two steel angles in a cross as a "hinge" hold together with one bolt in a much bigger hole, the outside corner facing the other outside corner, one set at the elevator hinge place, and one in the place of the seat. Thereby we also tested the fuselage! But at the end we supported the forward end of the boom too, we did not have any fiberglass on boom or pylon at this time, but we loaded the place of seat with 5.3 G * 116 kg / 255.7 lb. = 1355 lb. It did bend a lot but no damage.  

The tail boom is made with 3.5 mm (1/8"+) 5 ply Finnish birch plywood in the sides, top and bottom, and the by Jim Maupin recommended extra longerong was glued in, to take 8 G's.

I did not mount the nose wheel or skid; it will make a lot of drag from the forward part of fuselage. It's easy to add drag but hard to reduce it!

Instead the main wheel was moved 5" forward to prevent the bird from being standing on it's nose after using the wheel brake, we have a 300X100 glider tire on a Std Libelle hub/drum brake (Zündapp moped hub, mid -60's?)

The rear spar-fitting bulkhead (in the fuselage) is mowed back 5/16" to fit without any spacers between bulkhead and fitting. The rear double fittings is made of 1/4" 6061-T6 to cope with the JAR 22 demand's of 5.3 / 8 g's. The 15 m rear fittings is a big improvement compared with the one on the 13-m WR.

Fuselage weight is 36 kg without "pod" shell, bare wood. Elevator 6.5 kg, rudder 4.2 kg,

The fiber glass pod is a result from collaboration work between Norway and Sweden, Kjell Undbekken have made the mould and plug. It has one layer of 9-oz fiberglass on each side of 4 mm Divinycell.

In the aileron up position the push rod end ball joint is interfering with the rear spar fuselage fitting, and limiting aileron travel to about 21.5° up, maximum up is about 24° limited by aileron gap itself. Down travel are 18° with flap set to neutral, with the bellcrank from drawing sheet E 1.

Information's on the pitch trim device. The elevator or stabilator is a "all flying tail" unit and have a 5/8" built in trim tab at a angel of 30 degrees, Some builders test flights have showed that it is much to effective, I think it is better to build it with 15 degrees from start. If already built, the required forward stick force can be reduced with a triangle shaped Balsa wood strip glued on top of the tab, with the sharp end forward and a 4-5 mm squared trailing edge, reducing the upper surface to 15°, and/or trim back the fixed tab. Mush Hide flew his WR without any spring and cut back until he got it fully trimmed.

If one extra spring is coupled to the flap handle with a cable, so its spring tension become stronger at more negative flap setting it will trim automatically for speed changes.

For weight/speed trim we need another device.

We have been thinking of a couple different solutions on this. The best trim I have seen is on the DG planes, it just release the spring's or the "artificial stick force devise" with a small handle on the stick at the desired speed and when locket again it is trimmed.

We have a Fuji Robin EC44-2PM engine, direct drive; it's light, powerful, 57 hp at 6500 rpm, and 6.3 kg-m at 6200 rpm. We first wanted to have the starter rope inside cockpit on the right side of the stick, but it was not possible to do that, the aileron push rod was in its way. So it was just to buy a starter kit, it costs 3-4 kg in weight + 3 kg battery.

In bench test it produced 75 kg = 165 lb. static thrust at "just" 5500 RPM (45 HP) with the first propeller. I will make a new prop on the experience of that test run with lower pitch near the hub to prevent it from stall in the turbulent air from the pod, the turbulent layer is about 3" each side of pod, plus the flat rear end. I'm aiming at 5800-RPM static (50 HP) and 6200/55 HP in climb. BUT the propeller will make a hell of a noise.

The 6-inch wide end of the motor compartment, make a lot of drag, about 4 L/D units compared to a streamlined edge, and it have been showed that it reduce the propeller efficiency too, something to think about when designing the cowling's.

The most perfect engine would be a small and light, four-stroke, about 50 hp and 4500 rpm, but.