Just seems to be getting more and moreprevalent with simple diamond fins. I am now using sheet plastic for several models, but have yet to hear any comments on the comparative robustness of the resulting fin in the field. This is the Honest John M-50 (1919) with the short fins. Constructed from three plastic parts including the mirrored skin and an internal triangular rib that follows the fold line. The resulting diamond at the tip is filled with Squadron White Putty and then simply sanded smooth.

It feels pretty rigid along the fold and edges, just not sure how the flight loads are going to flex this. How I wonder could Rocksim model the attachment and potential to rip off fins?

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I've used this technique on several rockets and the fins seem to be at least as durable as balsa or basswood fins.

If such fins were filled with expanding foam (whick would be allowed to leak out through the root and tip openings before curing [to avoid making the fins bulge], then be trimmed and sanded at the roots and tips), they would be lightweight, very strong, and resist buckling under flight loads and landing loads.

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