Why is NOVA not building higher aspect ratio wings or wings with closed cells?


With higher wingspan you need longer lines: so more drag.
Specially in high speed gliding the additional line drag will eat up the advantage of less induced drag.

With higher aspect you will need more structural stiffness: so normally more cells = more lines (see above)
- or more wing curve = less efficiency
So there are some kinds of optimal aspect ratios depending on the target range of the wing.
There are also some optimal wing curves (see relation aspect on ground / projected aspect) depending on target range.

Re. closed cells: when the intake is in a good position, the open cell has 99.75% of the l/d of the closed cell.
So no need to close it because of that.