Fuselage April-May Truss Frame Revisions and Inspiration
Picking up from where we left off, we made several key truss frame revisions after analyzing the following build logs and info pages on Graham Lee’s ⅞ scale Nieuport 11:
The Nieuport 11 was a World War One fighter which was originally constructed using a wooden truss frame. Today, Graham Lee’s ⅞ scale Nieuport 11 plans are some of the most popular warbird replicas within the ultralight community due to their ease of construction and relatively low build cost. Similar to our own airplane, Graham Lee’s Nieuport 11 uses a gusseted aluminum truss frame. Graham Lee’s Nieuport 11 plans were originally released in 1985 and have since become regarded as some of the best gusseted truss designs to date.
More details on our latest landing gear revisions can be found in our Landing Gear Design Part 3: Revisions blog post but we’ll focus on the truss adjustments we had to make to adapt to the new landing gear here.
We updated our truss layout for 3 main reasons:
Our new landing gear attaches slightly inwards of the lower cabin beam clusters and therefore requires additional reinforcements
The previous truss design didn’t allow for easy pilot access
The previous truss design relied on a massive gusset plate connecting two sets of non planar beams. The gusset would be too thick to bend.
Old truss design inspired by the Legal Eagle; large gusset plate outlined in red
New truss frame inspired by Graham Lee’s Nieuport 11
In taildragger airplanes, the front landing gear takes the bulk of the landing load and the rear wheel is gently lowered to the ground. In the case of our landing gear design, this creates two large upwards forces along each lower longeron of the cabin. To mitigate this force, we had to add a vertical beam at each landing gear attachment point and a cross beam connecting each attachment point with its opposite point across the cabin. Without these new beams, the lower longerons would quickly buckle upwards and inwards during a landing. While Graham Lee’s designs call for the vertical support beams to be perpendicular to the lower longerons, we made them angled so they intersect at the upper cabin beam clusters where the wing attaches. This way, they not only reinforce the landing gear but also serve as a failsafe for the wing attachment which connects at the same joint. The angled vertical beams also form triangles rather than squares which is a good rule of thumb while designing truss frames.
Graham Lee Nieuport 11 Truss Frame Credit: Frank Geiger
Lastly, we adjusted the truss layout on one side of the fuselage to be a trapezoidal shape to allow easy pilot access. This was inspired by the door designs on the J3 Piper Cub and Skylite ultralight. To reiterate, these recent changes in our truss layout were made from a conceptual standpoint and are likely to change as we begin our truss analysis.
*Editors' note: the thought processes and design choices presented in this article don't necessarily represent those implemented into the final design and are subject to change. Flight Club Aerospace is a group of amateur students with no formal education in any fields of engineering. We present this information for educational purposes only, with the understanding that it is not to be re-created without adequate professional oversight and mentorship. For our latest designs and updates, please see our most recent blog posts.