KR2S :: Stub Wings

Darren & Hardy's KR2S Project

Stub Wings

The stub wings exit the fuselage and follow a straight line that points to the wingtips. The fuel tanks will nest in the stub wing area allowing enough room for the aileron controls to pass in the gap behind the main spar. As the stub wings have the dihedral already set, fuel line pickups and drains are easily established near the fuselage. Carbon fiber/urethane composite skins will cover the wings of this KR2S from the fuselage to the wingtips.

	A 3/8" line is marked inside the two AS5048 airfoil templates and then the marker is held extended from my finger tips and the hand slides along the profile to give an even line the whole way. Staples and icy pole sticks secure the template which has a chord length of 44" verses the 48" template at the fuselage.
	2" thick foam is cut to fill the bottom skin. I then carve the sides down to the lines that I marked previously.
	The foam is then lifted out and I have carved channels with the surform down to the carved out areas on the sides. This sets the levels to which I need to remove the rest of the foam.
	...almost done.
	When placed back in the stub wing, the shape conforms to the 3/8" lines perfectly.
	These carbon fiber straps are left over elevator gap seals and are good for stopping the foam from falling through and onto the garage floor. The plastic around the sides will allow me to cleanly remove the skin when the resin is set which will make fitting the tanks easier.
	The microballoons slurry is coated on the foam outside of the stub wing just because it is easier. The plastic sheet layup method is used to then apply the carbon fiber which is positioned on the 45^o angle.
	The whole composite skin is then lowered into position and rests on the straps. Clamps and timber just stop the edges from lifting.
	After the composite had dried I removed it and the airfoil templates from the spars. I used a cheap adjustable hole cutter attachment and added some lightening holes to the 4 templates. The gap between the holes and the template edges is 1 1/2" which leaves plenty of structural rigidity. Out of curiosity I weighed the removed disks and discovered my KR is going to be 10oz lighter!
	I wasn't happy with the valley depth along the spars that would have to be later filled with micro so I epoxied a 1/8" strip of hoop pine across the top and bottom of the spars and sanded them more closely to the contour of the templates. I have cut the supports out of the bottom of the templates which make them easy to slide down into position and then remove while sanding.
	With the lower skin held in place from above and below, I have begun making the primary strengthening supports for the fuel tank. These will be floxed in situ and then shaped to accept the fuel tank before being covered in carbon fiber.
	I have cut out the basic shape of the tank and then placed some sand paper on the supports.
	The tank then gets put on top and the sandpaper is pulled out while holding the tank in position. This is the best way to get the foam to exactly match the tank contour.
	The carbon fiber has been layed over the foam ribs which had a small layer of flox applied. Where the CF meets at right angles, the foam at that corner is sanded down and the triangular void filled with flox. When cured, this makes the edges and indeed the whole rib incredibly strong.