Big Dragon 2

jon
Neat video!
That heat forming looks very successful but as you pointed out in the notes at the end doing the same on a sheet for a full wing might be a bit more difficult to get the foam soft enough over a big area without risking over heating the foam and permanently damaging it.

Big sheets on a full wing is one of the reasons I avoid wrapping the leading edge and go for a more conventional solid foam leading edge sanded to profile. Once the profile is sanded one trick I use is to smear wood adhesive over the sanded area. It fills the now 'open' foam cells and once dry it can be sanded to a really smooth hard surface with a fine paper.
You can do the same thing with lightweight filler but the wood glue gives a stronger surface that is a bit more 'ding' proof. An important consideration for the leading edge.

The 'fancy' wing tip.

I doubt it will make the slightest difference aerodynamically but it is light being hollow with just 'formed' 2 mm Depron skins.

Wing-tip - usually fitted t'other way up on skid-landing models. Then the very tip of the tip gets the wear and tear!

Agreed Eric but more often than not the Big Dragon lands so slowly it is stationary before the wing drops.

I actually have 3 160mm templates printed out and a board to attach them to so I can get the ~500mm of skin trained. -Jon

The maiden of the new wing. Not that much wind but it was raining. :woohoo:
Just a short edited video.

The landing is for Eric. The wing tip did not drop until long after it had stopped!

Your 'gunsight' is offset too far left! [badass]
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The sky is crying here - too! It is supposed to be sunny tomorrow afternoon.

At last the weather did calm down this evening so I managed to properly test the new & now decorated wing with a full 15 minutes flight.

I suspect the new wing is a little bit more efficient as it now flies even slower or rather it needs more positive 'down' elevator to make progress into even a very modest wind. In addition the ailerons do not have the same travel as the direct drive ones so its aileron response is rather 'slow' at least compared to the elevator..
I can't do the usual remedy of shortening the aileron horn to increase the travel as it is already at zero! :woohoo:

The aileron is so thick I could have arranged the link to be beneath with wing surface so everything would be completely buried but it would require the servos to be repositioned. As I have only just completed the wing this mod may be 'for later'.

Longer servo arm?

A longer servo arm would indeed be a solution to increase the aileron travel but I have never seen a longer arm for the 3.7 g micro servo (I have lots of shorter!) so I went back to considering completely 'submerging' the servo and its arm within the wing so the link rod also be under the wing skin to a point on the aileron closer to the hinge line. This would however require considerable 'surgery' to the wing to do.

One alternative would be print a new arm but the servo splines are very small well beyond what a printer could be expected to duplicate so maybe a printed arm extension? In order not to have to remove the built in servo or even undo the arm retaining screw the extension would have to added in situ and glued in place. Not ideal as the arm is nylon and almost nothing sticks to that. :woohoo:
This is what I ended up with. It extends the outer hole radius from 12 to 18 mm.

The extension in place.

The extension simply fits over the arm. The servo arms on the wing have had one arm cut off.
The extension is an exact fit so the majority of the forces are mechanically transferred from the arm to the extension. The glue just has keep the extension in place. Glue should alsoextrude through the 3 original arm holes which will help with hat.
A video if the new arm in action.

It now has travel close to that of the original wing's 'direct coupled' servos which should restore a similar degree aileron control. The proof will have to wait until this persistent easterly dies down! :woohoo:

In the Cafe a couple of weeks back I noted that I broke off the nose of the Big Dragon 2. Its pod and wing pylon is a glued together 3D printed structure and of course the break occurred the a point of maximum stress in any sort of a landing incident.
 
To make matters worse the break occurred exactlybetween two previous repairs achieved using an overlapping printed sleeves of different shapes & diameters. Hmmmm.
The  only prectical solution is some specially shaped printed 'joining' pieces to give as big a glue area as possible.
In addition the wing pylon had suffered some localised 'compression' damage so it now looks like this:
 
Unlkely to be quite a strong as the original but hopefully adequate.
I suspect the Big Dragon 2 is close to the end of it life as I really do not relish the thought of reprinting the complete fuselage pod and wing mount as it is made up of atleast 7 different pieces and there are a good many variations I developed as I went along and I have no idea which were used in the final version.   
Still as the electrics still work and with 5 years printing design experience i could probaly do a structurally better job. We shall see! 
 
 

I have also used such printed joining pieces - tend to work if done with some layers so at least some will provide strength.  I also found that reinforced tape will hold fuse half together quite well - I often did just a tape join for early flights while still working out COG (I had two different lengths of front fuse to go with two possible battery arrangements.  That was good for a dozen flights, several with slightly aggressive landings.

To my annoyance and embarassment I broke the Big Dragon again!
 
At least it did not break at the previous repair but further towards the nose.
A fairly simple repair. Glue on the break and an all round printed patch glued over the joint.
This time the motor broke free as well. Not that surprising as it is a relatively heavy.lump on a rather precarious mounting. The previous impact had probably weakened it.
The new mount is a bit better designed and more to the point the motor can now actually be removed. A feature that was lost when additional reinforcing was added to the original motor mount.
Need to let the glue harden for 24 hours so will try again tomorrow if as forecast the wind remains light and the rain stops for long enough. I will also get out my unused "reserve" set of boots.
So now it is back to the seemingly endless job of repairing the Big Skyray.

Calm and sunny today, once the fog had lifted, so as phoped the Big Dragon was tested.
No problem it flew very nicely. The added repairs have added a few gms so some mild trimming required.
Had to make a very limited cicuit to ensure it landed on the small not muddy patch!   

After the substantial crash on the 1 Dec 23
 
By 5 Dec 23 all repaired with new printed parts and some minor repairs
 
Not yet flown.

 

As described in "Been flying" the maiden of the repaired Big Dragon on the 30Jan24 was a disaster.
The wing survived undamaged but the middle of the fuselage and the wing  pylon were destroyed.
These are the salvaged bits.
 
Took a while to work out which print files went were as there were many specials from previous repairs over 6 years of flying.
Nearly 8 hours of printing and it now looks like this.
 
The glue will take some time to get fully hard.
Some filler and paint and you won't be able to see the joints!