WK95
Well-Known Member
Wing Structure
Legend:
Orange-Shear Web
Light Blue - Outboard Spar Tube
Dark Blue - Inboard Spar Tube
Yellow - Ribs
Translucent Orange - Wing Module Skin
The wing has no taper with a constant airfoil section throughout. The wing span is 9.8ft wide with an aspect ratio of 12.
The wing consists of an inboard section and an outboard section that are joined via two carbon fiber tubes with the outboard one fitting into the inboard one. These tubes are shown in blue. The tubes are sized to resist both bending and torsion. The outboard section tubes are attached to the inboard section tubes via a vertical oriented bolt located on the outer portion of the inboard wing section. One bolt is used on the front and one for the rear. These bolts are also long enough to provide a mounting point for the tail boom. This transfers the loads from the tail to the spar. I'm aware that a circular tube is not ideal compared to an I-beam however is provides an excellent means of joining sections of wing.
The skin is not shown for clarity. The orange components are shear webs made from bidirectional carbon fiber sandwich. They also help distribute the loads from the skin to the ribs (shown in yellow) to then to the carbon fiber tubes. To install the shear web, I only need to layup a long, flat sandwich laminate (bid-foam-bid) then drop into place. Using some putty to hold the web up, I use some micro at the corners and bid to attach the web to the skin. The rear shear web also serves to close up the rear end of the torsion box as well as provide a place for control surface loads to be reacted to the spar.
The unidirectional spar caps are laid up with the skin (bid_skin-uni_spar_cap-foam_core-uni_spar_cap-bid_skin) and are the same size as the skin. In other words, rather than a localized spar cap, the spar unidirectional fabrics are distributed throughout the entire surface. This lets me layup the spar and skin in one go. Simple and removes the need to make a mold for the spar that follows the contour of the airfoil. For reference, to resist bending moments, I am expecting to need at most 3 or 4 layers of uni in the inboard section. In the outboard section, I would need 1 to 2 layers. I'm aware that this configuration is more limited in how I can tailor the width of the spar since I can't tailor the width so the wing will be heavier than it needs to be.
The wing's inboard section fits into the orange part you see on the fuselage which is the wing module. It transfers wing loads to the fuselage and is attached via 4 vertical bolts. The wing module skin OML is seen in orange. Not shown is the load carrying module underneath. Still working on this one. I'm considering 3D printing it using a Markforged printer which is capable of printing continuous carbon fiber strands for reinforcement. Alternatively, I can also make that from multiple sandwich panels cut to shape.
At this wing module, the left and right wing spar tubes meet and are joined with a ferrule. Running horizontally from fore to aft of the aircraft, through the ferrule and spar tubes are shear pins to react the wing bending loads to the wing module.
Other features
The control surfaces on the outboard wing are a double redundant pair of flaperons manufactured along the wing skin in one go with the use of a kevlar live hinge. The control surfaces will consist of a carbon fiber skin with a solid foam core.
Additionally, I'm expecting a 35lb gross weight; up from the previous 30lb projection. The 12lb useful load for avionics and fuel remains.
