1200mm Dragonfly

Got the wings built & it loosely assembled. Next is to fix & glue the centres of the wings together & cover the wings & tail so I can see where to position the battery for the best COG.



 

I suppose it depends on how true to the original you want to be.
As Eric points out the original had a very long "motor" and a light prop so a long nose made sense to get the required CG. 
With electric you know you are going to have a compact heavy battery as well as a relatively heavy motor so it improves the effectiveness of the tail volume to concentrate them together to get a suitable CG position and shorten the nose accordingly.
With the motor in that long nose and as a consequence the battery a long way back the plane will have a significant longitudinal inertia compared to the original. This could make trimming for stable flight a bit harder.     

The original did have a long nose, I think that's part of its charm.
The two models from The Model Barn both needed a load of lead up front to get the required COG & even in the FX707 I had to replace one of its balls so the idea is the battery can go in the nose to save on lead. It can always be moved back to be mostly behind the COG if necessary.

A bit confused as to why increased longitudinal inertia makes it harder to trim. Is it the side to side or the up/down or both?
I've ordered a gyro for it to try to make flying it easier.
 

Inertia can effect both but up/down is normally the more sensitive.
The natural stability forces are set by the effectiveness of tail surfaces and the length of their moment arm from the CG. A plane with more inertia will thus naturally recover more slowly than one with most of its mass concentrated close to the CG. This then poses the question was the deviation caused by a permanent out of trim effect or just an external disturbance?
It "natural stability" recovery takes too long there is a danger the "ground can get in the way" before it does!  
         

I've been trying to cover the tail of the Dragonfly with Kavan film. Its a disaster!
I've read the instructions & used the temperatures therein & its pretty much like using the Polyester fabric I used on the Buzzard & Slider but totally unforgiving. When ironing it onto the edges it wrinkles if you don't get the timing perfect. Once the edges are done using the heat gun shrinks it but when moving the heat gun away it can catch it & it produce massive wrinkles in what had been flat.
Maybe a simple straight wing would be easier, the Dragonfly is very curvaceous.
It seems terribly sensitive to the amount of heat & once its wrinkled there's no undoing them.
Removing it is a doddle, a quick blast with the heat gun & it curls up & can be peeled off.

So I'm going to have to use either the polyester fabric or traditional tissue.

Presumably you mean fold the edge of the material over the edge of the wing/tail.
As for the polyester fabric which is based on the technique for the plastic films you've got to pull it over the edges & then tack & then bond it. With a curved edge its not easy.
When you try to shrink it from the middle, it pulls the bond off the edge as there isn't much temperature difference between shrink & melt.
The instructions say 100C for melt, 140 for shrink. I found it would shrink with the iron set ar 120. I used the heat gun at its lowest setting but it still was able to wrinkle the film as it was moved away.
When I tried to fasten a single panel over the fixed plane & elevator on the tail the bond pulled away from the hinge join & the elevator was pulled up.

To start with I think the tail is too small & curvaceous for this material.

I've double-checked the temperature settings. Use 100C to fasten the film around the edges & 140C to shrink it. I found that after sticking the edges if I ran the iron the iron over the surface without altering the setting it would shrink the film smooth.

When using the heat gun I kept it moving, I learnt that doing the polyester fabric, but a couple of times when moving it away having shrunk it smooth it wrinkled. The moving-away loci must have gone closer to the surface unintentialy.

When shrinking a surface with the hinge using the heat gun. I held the control surface down but the glue on the hinge longeron melted & the shrinkage was enough to twist the elevator & unstick the film.

All in all I found the film difficult to use especially on the shape of the tail.
I've ordered some Polyester fabric to use instead.

Edit
I attached the Kavan instruction pdf but it swamped the post so I've deleted it. Its easily found.

 

I've been pushing on with the model but its stalled at the moment because some stuff I ordered from ebay which should have been here thurs/friday hasn't arrived yet. There is four separate orders & none have arrived so I suspect its down to Royal Mail. They were talking about reducing second class deliveries to once per week.
I gather from my mate the postie that morale is pretty low & there's alot of sickies (he's one).

Aliexpress orders coming from China don't seem to be taking any longer!