reenforcing lower cowl

[Dave S]

Dorsal,


Similar issue up here. Back when I started testing the plane, one of my hangar neighbors observed that the lower rear part of the cowl where the air exits the cowl behind the radiator was vibrating up and down quite visibly.



With the nose gear, some material is cut out of the rear of the cowl bottom and I originally though the cutout was in part responsible for weaking this part of the cowl and exacerbating the vibration problem - not so sure now.



To reinforce the cowl in this area, I riveted an aluminum bar across the bottom of the cowl in this area with the bar on the inside surface of the cowl. That seems to have solved the issue. I don't have the precise dimension of the aluminum bar right off hand, but I believe it was approximately 1/8" thick.


The other thing I did on the cowl bottom was to rivet in a fabricated aluminum "U" shaped edge for the NACA duct - this won't help the vibration at the back issue but I wanted something a bit more solid than the simple fiberglass edge. Photo attached; but, photo included to show approximately where the rear lip reinforcing bar went in later - the bar was riveted in just a bit forward from the notch in the rear of the cowl for the nose gear, on the flat part of the cowl, so it would not be near the radiator bottom.



If I recall, the vintage of your kit and mine is about the same.