2 meter custom design and build Electric glider - failed.
Apr 22 2012 by FaTe
Quick jump
This project was my latest attempt to build a better FPV platform than a stock model. Unfortunately during it's maiden flight it was found to be highly sensitive to control input with constant adjusting required. I managed to get round a full circuit to land but when coming into a glide slope for landing, slowing down the whole high sensitivity got massively worse, lost air-speed and stalled cracking the wing completely in 2 while 1 piece was still bolted in place - says enough.

I decided to post the project anyway because it's a case of lesson learnt with the design flaws and to be honest is totally surprising it was able to fly a circuit at all.

This glider is pure balsa with carbon fibre re-enforcements, it has a 2 meter wingspan which where designed to come apart into 1 meter pieces for storage. Motor to tail it was 112CM long, the tail was a solid carbon fibre rod 5MM in diameter but it still was pretty flexible this is where my mistake lies. In flight the vibration of the airflow caused a fish tail effect which in turn adjusted the control line lengths (by swaying right it would pull more on the rudder than it should for example). So each correction to bank the opposite way to the roll resulted in the tail flexing and the rudder pulling in the opposite direction so it was full on correcting.

If your building something similar with a not so light model (500 grams +) I'd suggest continuing the fuselage as a whole balsa construction to the tail OR using a 7MM/5MM carbon fibre tube and epoxy the rod inside like a sleeve but this is more weight (I already had to add 245 grams of lead in the nose!) Well here's the build:
The back of the fuselage had a divider separating the tail servos from the main compartment.
Magnets where used to hold the front panel on the nose in place.

fuselage electronics test setup
Here you can see all the electronics in place and I added a hinge on the nose panel.
The wing was to be held in place using a nylon nut with this steel locking nut in the balsa wood.
Quite an a-typical tail build with a span of 50CM and a height of 15CM.
Now covered using solid silver Orafilm.
Most people install servos into the wings on the wing frame meaning later if they need replaced you have to damage the frame. Instead I always put the servos on plywood covers.
Mocking up servo placements in the wing.
The basic frame with ribs standing 2 meters tall.
You can see how the wing uses a slot/tongue interlocking system.
When the slots overlap they line up the hole for the nylon bolt to pass through pinning the wings together.
All the frame work together.
I added 2MM balsa sheeting over the entire wing top which made the wing super solid and didn't actually add that much weight for the benefits gained.
All sanded down ready for covering.
Again the same solid silver Orafilm with servo panels installed.
The plan was to mount FPV gear on this plate which overlaps the other wing when together.
When I got to the field and began adding weight to balance COG I ended up adding 245 grams of lead into the nose to balance COG! (Making AUW 1275 grams still light really)
The whole plane in 1 piece for the last time...
So as I said previously when landing and slowing down resulted in a nose dive the damage was not small. Here it just looks like the elevator popped off, thats snapped 3 good grade pin hinges clean off, it was just hanging.
The true death picture. Notice the wing bolt is still screwed in place... notice the right wing is still in place and the left .. well isn't at all. Totally snapped all the panels.
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