Folding experiment

25 April 2016

 2nd experiment. I thought the fins should be rearwards.

Progressive foil from flat to curve with curved tips. The fins are toed-in.

 3rd experiment. I want a bit of pod but not the triangular side view pod of the 1st experiment. I want to reduce the sweep back, not the 45 degrees swept back of the first experiment.

 3/4 rear view of the 3rd experiment piece.

3/4 front view of the 3rd experiment.

I added some weight to the front  and it is capable of gliding. There's some form of spiral stability.






For a swept back, the leading portion of the foil gets smaller on plan view. The point of maximum camber does not follow the swept back panel, it remains perpendicular to the root but will be affected by the tip arc. There is progressively less material forward of the maximum camber point. I think the arc at the root for a swept back should have the point of maximum camber further back, perhaps 50% from leading edge or more, how much depends on how much swept back.

The foil goes from maximum camber at the root, to perhaps half camber at the quarter span. In case of a swept back, the quarter and mid span airfoils have a greater positive incidence than the root's. At the tip airfoil, forward of the point of maximum camber, the leading portion is at a positive incidence, the rear panel is at a negative incidence.

I don't suppose curved foiled tips are aerodynamically superior than a flat plate.

Additional points to consider for a swept back configuration

• At the root: Set point of maximum camber of the root arc to be set 50 percent or even further back.
•  At the tip: Depth of camber of the tip arc to be a fraction of the root's. Set point of maximum camber forward. Apart from the lower panel of the fins to set the tip's airfoil, trim the fins so that the area presented is centralised around the zero incidence (to direction of craft).

For a plank configuration:

• Use arcs only at the root if a pod is to be constructed, otherwise, leave it flat.
• Cut separate pieces of fins with curve bottoms (segment would work well too and be easier). These are glued to the tips so that the tips will be curved (if segment bottom fins are used, then a creased triangle at the tips is good). However, this is not solely folding anymore.

22 April 2016

I thought of constructing a swept back flying wing; one with a cambered airfoil at the root and progresses to some washouts/reflex at the tips using the least material and in the shortest time.

I came up with this experiment with a rectangular piece of note paper, a ruler, a pen, and some tape.
Could I do this with thin foam sheet foam? A longer and narrower piece will give more wing area and make the pod and tips smaller. Arcs of different shape and depth will affect the outcome. I will need something to stiffen it spanwise. I wonder if this would be feasible for RC power conversion.

I inserted a small plastic headed dressmaker pin to see where the approximate CG is and found it located between the tips' leading edge and roots' trailing edge. Need something to stiffen it spanwise.


The straight lines were for tracing out the arcs. 6 folds and some tape I came up :


Top view.
 Ooh... clear canopy!









Bottom view.











Front view.
I have curved leading edges.









 Upside down.
I have cambered airfoil at the root that progresses to a reflex airfoil at the tip.
In the side view, the root airfoil and the tail airfoil joins to a S-curve.