The many crashes of the Flying Flea on Saturday

On Saturday:

1. Acceptable wind condition, hand launched, nose dived and smacked the ground, nothing broke.
2. Moved the 2S500mah battery out of the intended battery slot compartment, placed it in the cockpit. Acceptable wind condition, hand launched, nose dived and smacked the ground again, one of the rigging tabs came loose, together with a strip the tracing paper covering.
3. Glued back the rigging tab, taped the battery just in front of the rudder. Acceptable wind condition, hand launched, looped and smacked the ground once again, the wing pivot made of 0.25mm clear PVC sheet broke, the hinge at the fore wing pulled out of the foam.

Back at home, I placed the damaged model on a table, a gust of wind flipped the model, sending it on its fourth crash upside down and broke the rudder hinge.

I removed the 0.65mm nylon fishing line rigging wire and pull lines, took a small plastic horn and glued it to the apex of the cabane struts to use as the wing pivot. This took the front wing forward and higher. Deemed desirable based on the internet search of  a forum for full size Flying Flea.

It listed a few key points:

1. CG to be  23-26% of the total chord.
2. The front wing must not overlap the rear wing.
3. Use latest reflexed airfoil (which I can do nothing about it unless I want to do a new model).
4. More than quarter chord vertical distance when the front wing is at maximum angle.
5. 0 degrees incidence for rear wing, 0-12 degrees incidence for front wing.
6. Not to use older designs (which I happened to based my model on, well, can't do much there).

 The plastic horn will bring the front wing forward and higher, while not in keeping with at least one key point, it ought to improve the dangerous dive somewhat.

While trimming the sheared off rudder hinge, the rudder lug points broke. These items were fabricated from 0.25mm PVC clear sheet. I think it is not flexible enough. Another lug point at the wing had the lines pulled out of the centre hole too.

So I repaired the broken lug and horns with more 0.25mm PVC clear sheet, as that is what I have and tried using tape hinge for the rudder. The taped hinged rudder looks ok, but on testing, it was too inaccurate, the rudder cannot centre well because the hingeline is only 2-3cm. I sewed on figure 8 thread hinges with yellow thread (the fuselage and rudder is sprayed yellow) and this is fine.

Using white thread, I rigged the model. I did not have to use aluminium tubing anymore. The thread is more flexible than the 0.65mm nylon fishing line and a few half hitches do the job admirably well, more importantly, no curved lengths of rigging which lead to spongy lines.

In the evening (after a trip to jethobby in the afternoon to buy a non-in-stock replacement motor shaft for the AS2816 and ended buying a FMS mini Mustang of 800mm, and assembled the Mustang), using excel determined the CG to be at 2.75" from the front wing's leading edge.