Thursday, 19 March 2015

Hanno Prettner Magic - Part 3

A bit of progress in the past few days. The Magic is taking precedence now - mainly because I am using my large Building board and there isn't as much space available.

The retracts have been added - and as a bonus, here is a little video coz I know you all like them.. I have added 1/16" soft balsa infill around the retract mount to give the sheeting something to stick to.

Quite pleased with that nerd the retracts and wheels are fully retracted and out of the draught when retracted.
The hinge for the flap. I actually made a small mistake with the hinge line, it should be 3mm higher - I have located it centrally. I may cut them out and redo them, I'll weigh it up.
The angled wing tip was a bit more tricky than I thought it would be. Getting all the spars cut to length and at the right angle was a bit difficult. When I got round to doing the other tip last night it was much easier - lessons learned and all that... There will also be a 1/16" ply facing which will go on after the wing has been sheeted.
Although not shown on the plan, I have added 1/16" balsa webbing down the length of the wing. This adds a lot of strength and my flying is definitely not as good as Hanno's so I think I will need all the strength I can get.
The false LE and TE have been sanded to the correct profile, this wing is now ready to be joined to the other half when completed then sheet covered.
Repeat for the other wing - but with far less textual information. Just remember to make one of each side..

Anyway *some* progress - not much though..

Aileron mounting rails. I wanted to mount the servos from underneath (like I did on the flea fli) - However, the depth of the servo is 3mm too much - never mind. The balsa sheet bracing is in place because there isn't much wood under the bearer.


Working on the wing. The Other wing half has been skeletally completed.
Time to join the two halves
I am adamant that this wing will be straight so that when I set the dihederal, I propped both wing tips up using these little jigs under the last rib. This will ensure that both wings will be identical (warp wise)


Joining up the centre section was fairly easy. As both panels were propped up it was simply a case of sanging the LE, TE and spars so that everything touched where it should. Building on the plan ensured that I had the correct LE sweepback


All clamped up while the glue dries...
Now. the plan shows that the panels are joined using 10mm balsa across the centre bays only. I am decidedly unhappy about that and elected for a tapered 1/4" spruce spar across the 4 centre bays - top and bottom. To compensate for the dihederal, the upper brace is inlaid by an additional 1.5 mm at the centre and the lower has the extremities tapered. This looks much more rugged, but I would welcome advice on whether it will be strong enough..


Another shot.


This shows the amount of tapering required on the lower brace - more than the upper brace because the wing is tapered.


And after it has been planed and sanded to shape.


Adding the lower skins. Cut as per the plan using 3/32" balsa sheet - not especially good quality although it looked OK when I did the cutting. The U/C holes are a bit on the small side. I'll open them up after the upper sheeting has been done.


Note the holes for the Servos. I am putting Tower Pro MG996 servos in for the ailerons.
I have got a bit further than this, the other panel has also been sheeted (lower surface) and the servo mount for the flap servo has been added.


I have followed BEB's lead and brought the five servos to a HD15 pin D socket and plug. I have to admit that I am not really happy with this and may move to a similar solution that Martin McIntosh used on his P51. The only reason I am unhappy is that the wires were too big for the solder buckets so I am not getting maximum strength from the joint. I don't think they will fail though..


The socket is mounted on a liteply plate and is deliberately placed at the fuselage side so that there is space for the plug to fit alongside the fuel tank.


A switch has been fitted for the retract power - a NiMh 4 cell battery which will be located in the wing root. This is sat next to the Flap servo


With the servos fitted and wired (and TESTED!) I have laid up the sheet for the upper skins. I am using slightly harder wood than I used underneath.


Adding the skin. I have used PVA to glue the skin down. The multitude of weights scattered around help ensure good adhesive contact. Just how many objects can you get on a wing before it gets totally crushed.


With the skins in place and trimmed back, the LE is glued in, stripped from 3/8" balsa sheet


Slot cut out for the battery and lots of elastic bands pulling the LE in place.


Upper view of the wing, LE has now been trimmed and sanded and the wing is almost ready for glassing.


Lower view. The wheel bays have now been sheeted, but my circular wheel orifices are definitely not circular. Its amazing how a mm or so of deviation is so obvious when it is meant to be circular. The wheels are a very close fit, less than 1mm in places - other places its a bit more... blush


Finally for now, the upper centre section. I'll use velcro to keep the battery in place and a bit of filler is needed but apart from that I think it looks quite neat. Note - you wont get a close up of the wheel bays... nerd

Next job is apply the ply wing tip caps and the bits of TE that are not flaps and ailerons, then glass it.

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