Thursday, 19 March 2015

Hanno Prettner Magic - Part 2

The cowling. Before I can fit the upper deck, I need to get the cowl fitted.


To get rid of the run marks and the air bubbles, I have sanded down the cowling using 80 grit sand paper. The cowl was measured for height from the prop driver to the Firewall and cut and filed down to size. the holes for the prop driver, cylinder head and needle vale removed and a test spinner (not the final one) fitted to check alignment. Note also the test fit of the first of the two decks that I made.

 

An underside view. I have to admit that I am really quite pleased with this. nerd There is a very slight gap at the join with the fuselage sides, but nothing a tiny bit of filler wont cure.

Installation of the pipe. I made a clip for the rear end of the pipe to hold it in place - I'll probably replace this with a spring clip at the centre of the pipe later.
photo0045.jpg

I have added 8 hardwood mounting blocks and a hard 1/8" square balsa flange to support the sides of the decking. After a bit of consideration, I have decided to use the second of the tunnels/decks that I made and started trimming and sanding it down to fit.
photo0054.jpg

A bit overexposed in the bright sunshine yesterday afternoon. but you can see the air intake for the cooling air above the cowl - I still need to make the outlets..
photo0056.jpg

The fit at the rear of the fuselage. Again a couple of minor gaps that need help with a bit of filler. I am still sanding down the decking to remove the blimps caused by the problems removing the first of the two decks that I made..

Apart from giving the cowl and the tunnel a couple of coats of primer I have done very little on the Magic. I ordered the wing ribs from Belair and they arrived last Thursday. The Flea-Fli was cleared off the bench and work has now started on the wing.
This very much a 'Metric' model - none of the standard wood sizes have been anglicised so I have to make a couple of compromises. It is amazing though - just how difficult it is to get a 1/4" wide spar into a 6mm slot..
Spars. The spars are listed as 6x8 mm and made from balsa. I originally was going to go for 1/4 x 3/8 spruce (planed down a bit) but then decided to settle for 1/4 square balsa with a 1/4 x 1/16 spruce cap. So the first job was to laminate the spars.

pb170024.jpg

(Look a bit warped but they really are straight - just a distortion of the wide angle lens)
This is just marginally less than 8mm but adding the spruce cap adds a huge amount of strength for very little additional weight.
Pin down the upper spar (wing is being built upside down) and a quick push together to make sure everything fitted.
pb180002.jpg

Next step - mark out the slots for the retract bearers, cut 1/8 ply doublers and get them glued up.

pb180003.jpg

Cut the ribs back where the flaps will be located.

pb180004.jpg

All the slots etc. were marked and cut using a square over the board and drawing verticals from that point. The excess was cut using a razor saw.

pb180005.jpg

False leading edge glued in... The u/c bearers have also been added as well. One problem I have spotted is that the U/C pivot point is about 8mm inbound from the point shown on the plan. Which means the wheel well will also have to be moved in a bit.

pb190007.jpg

Finally, the upper spar and false TE have also been added. I am using Kevlar cloth (again) for the hinges and laminated the false TE/hinge block as described in the Flea Fli build.