Big Dragon 2

Congratulations

As reported in the "Been Flying" thread the Big Dragon 2 took a serious hit with a truly impressive lawn dart job. The wings folded after I got a bit too enthusiastic doing glide aerobatics

Everything can be repaired/reprinted except the tail boom. I have ordered a replacement (2.1 m fishing pole) super cheap from China.
The most difficult repair will be rejoining the undamaged wing halves. To ensure it ends up significantly stronger I will probably have to cut each wing back by a rib or two and insert a new stronger and flat centre section so the dihedral braces are further out and under less stress.

There are also a few changes I can make to the printed pod to ease installation of the electrics and improve the strength of the motor mount (it broke off in the crash)

Of course I should really scrap the whole thing as I need space to store the the future DH91 (and the existing A350 and V-2!)

Harrisons rods in liverpool will supply rod sections cheaply too. You can actually go to the factory and pick your own. Even specify and watch it made. My eldest lad Andrew works there and would be glad to show you what you want if you ask for him.Mention my name of course They will also supply carbon sheet and give advice too You could be there in about half an hour allowing for the traffic LOL
www.google.co.uk/search?q=Harrison%27s+R...ceid=chrome&ie=UTF-8

Thanks OT but I have already ordered a pole from China.
The first of the replacement printed parts - the battery compartment lid.

Showing the small 'indent' to hold the magnet which I have salvaged.
Its 'partner' magnet fixed into the nose cone is still buried 8" into the ground!

Take a shovel next time! [badass]
Where do you get the G code for your airfoil shapes? Is there any chance you could print out a relevant page (even if it's not all of it) scan it in and post it on the 3D printer page?

klippy
I am afraid I 'draw' my airfoil sections using the 'part ellipse' function in FreeCad.
I find a print of the section I want to use on Google and then 'compare' it to a paper print of the one I have created.
I personally believe I can get as close as is necessary for the light slow planes (very low Reymolds number) I tend to create.
Also when you cover a built up wing with mylar or tissue the actual section of much of the wing is not quite that of the ribs so extreme section accuracy is likely not that significant.

Hot off the printer the second bit - the nose cone.

Exactly the same profile as before but the internal 'fill' is altered to give a slightly stronger structure.
Note the magnet recess.
This item actually stuck to the bed so well the only way I could get it off was by peeling off, and thus scrapping, the masking tape bed covering which I had only just replaced! :woohoo:
Now to design some improvements to the 3 main pod pieces .

Quorneng wrote: Thanks OT but I have already ordered a pole from China.
The first of the replacement printed parts - the battery compartment lid.

Showing the small 'indent' to hold the magnet which I have salvaged.
Its 'partner' magnet fixed into the nose cone is still buried 8" into the ground!

The info may be useful to somebody. Q

A few more printed parts.

Still quite some way to go.
Next is to look at re joining the wing.

As the printing the replacement (and slightly improved) parts is taking quite a long time and I am not over enamoured with the quality of the printing (different PLA supplier) I wondered if it was possible to print all the parts, except the nose, in one go.
Done as 3 pieces there has to be top and bottom surfaces to glues them together. Done as single print this time, and weight, would be avoided without compromising strength.

The blue bits are support structures that are designed to 'break out' easily.
The flat top of the pylon is set to 2 degrees incidence.
It took several goes (about 5 hours!) to establish what would be possible and practical but this is best so far but it still a mind blowing 14 hours 36 minutes! The thought of a failure in the last ten minutes doesn't bear thinking about :woohoo:
This is actually about 4 hours less than their combined separate print times. I have already spent nearly 13 hours printing two of the pieces and last bit will take another 6!

And I have cough and a cold. Have to wait 8 days to see the doc - I'll probably be better by then!

Rather you than me Simon.

i get nervous at anything longer than 5 hours.

would a raft on the base make things more stable when printing that high.

Tony B

or print a tripod that can be removed after? :S

I use a marking tape covering on the bed and so far the technique appear to be to print the bottom layer with insufficient bed clearance - less than the thickness of a piece of paper. It makes the initial layer very thin (almost hard to see!) but it really sticks to the point the finish part is hard to remove needing a sharp very thin blade to carefully 'work' it off,

The final bit not yet included is to set a 100% fill density of the motor mount area but retain the 8% fill for the rest.
I only found out how to do this a few days ago!

Quorneng wrote: I use a marking tape covering on the bed and so far the technique appear to be to print the bottom layer with insufficient bed clearance - less than the thickness of a piece of paper. It makes the initial layer very thin (almost hard to see!) but it really sticks to the point the finish part is hard to remove needing a sharp very thin blade to carefully 'work' it off,

The final bit not yet included is to set a 100% fill density of the motor mount area but retain the 8% fill for the rest.
I only found out how to do this a few days ago!

Well done that man. You're a better man than I am Gunga Din Regards John

Between bouts of coughing some progress. The replacement battery box and nose.

What is mildly satisfying is that the parts fit together perfectly straight from the printer!

Actually my second job as I had to print this part of a dolls buggy again!

Just as well I kept both the CAD and STL files as creating that 20T external gear shape was quite a challenge.