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Dry fitted and then put a False Leading Edge on the ribs and adjusted to get a nice straight Leading Edge. Then used thin cyano to glue it all up.
Here are the two wings before shaping the False Leading Edge.
Next out with the razor plane and trim down the False Leading Edge to the same shape as the airfoil. Hmmm seems despite my best efforts at cutting the ribs a few were not quite right. Sanded down the few proud ribs, and will add some balsa to the few that are too low. Once the wing D section is covered in 1/64 ply it should look better.
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Next job should be fun, the DFS air brakes.
Left is a picture from Cliff Charlesworth's excellent book Scale Model Gliders. I have found it an invaluable resource for building this and my K3, both from Cliffs plans.
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Hmmm interesting. Plan has top airbrake (air-brake) further back on the wing. Different from the picture above. Well it makes more sense for me to have the top air-brake raising nearer the spar to be more effective.
I made a kit of parts for the 4 air-brakes. The 4 bits of ply at the top are the brakes. The 4 brass tubes have piano wire in them for strengthening and are the air-brake axles. The 4 long thin bits of ply are the air-brake arms. The 8 bits of spruce are the re-enforcers for the ribs. The 4 brass bits will be the control horns for each air-brake.
Unfortunately the airbrake blades have bent a bit so will use aluminium or bakalite or something similar to make the blades. So Air brakes will have to wait a while - (see further down)
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The tow release is now completed, air tow is going to be possible. Design is taken from Cliff Charlesworth's book.
Here are all the bits, in the end I only used 1 sheet of brass. Rest is piano wire, brass tube and a spring from a biro.
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Here is the completed tow release and also showing the operation in open and closed positions
The spring returns the release to closed position.
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As the 1/4" for the false leading edge worked so well, thought I would do the same for the aileron sub spar and the aileron leading edge. So I measured up the tip ribs that need to be cut for the ailerons. They each need 1/4" cut from them.
Then made up some twisted pairs for the wiring to the servos. Also strengthened the spar where the holes need to be cut for the wiring.
Marked up the rear of the spar where the ribs go, then drew lines perpendicular to the centre of the spar. The blue lines on the spar at the rear are marked up ready.
Glued on the ribs on the line and perpendicular to the spar. The marked up the aileron sub spar and cut slots 1/8" deep. This was then added to the ribs. It was held to the bench so it was straight and the ribs adjusted accordingly then cyano to hold it all together.
Then a check revealed a few ribs were squint a bit, so a combination of adding balsa and removing fixed this. Bottom spar in the picture has the aileron sub spar shaped to follow the contour of the ribs. Pleased to say the washout was evident towards the tip which was pleasing.
Bother, just looked at the picture and realised I made a small mistake. The rib nearest the root on the aileron sub spar should be full length! Well is will be when I fix it! |
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I completed the other wings tip ribs and aileron sub spar and gain had to sand some proud ribs and raise some low ones.
Now on to ailerons. Take the 1/4 leading edge and put it on the aileron sub spar and mark where the ribs go. Cut the 1/8 slots and then fit the ribs. Then adjust for nice profile of the ribs before cyanoing them in place. Picture shows aileron attached to wing so that I could sand the aileron leading edge to shape. Well it worked but was hard work.
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So for second aileron sanded the leading edge before attaching the ribs. Then added the ribs in the 1/8 slots. Adjusted ribs that were not quite right and then added the ribs again ensuring all was correct. Next I put the aileron on the wing and it all fitted fine.
One slight thing about the aileron ribs they are perpendicular to the leading edge. However they should have been at a slight angle to follow the ribs in the wing Did not discover this until added aileron to the wing and thought bother. Could re do them but is it worth over 3 hours work considering once the ailerons are covered the ribs will not be too visable.
Here is a picture of the wings and their ailerons thus far. |
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So got some 1/8" aluminium for the air-brake. I used an impact adhesive (Evostick) and added 1/16 balsa both sides. Need an extra rib to support the air-brake in the wing. Added the 1/16 ply and 1/8 spruce to the ribs to support the air-brake axle. Glued on the air-brake arms and here are all the bits.
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In setting it all up ready to add the air-brake ribs I noticed I had made the aileron 1 rib too short. Hmmm oh well the aileron will be a bit shorter. |
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Here is a picture of the air-brake in the wing in the closed position. Need to take some of the ribs down so they close flush with the wing. |
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Here they are held open. The view is from the rear |
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Here is a picture of the internals of the air-brake. The bit of brass in the middle is the horn for the air-brake. Being brass and tinned I will solder the horn to the brass axle once I have worked out the control movements. Fortunately (and probably by design from the original) when the air-brake open one is helped by the air while the other is not. The top air-brake opens forwards against the airflow while the bottom air-brake opens backwards helped by the air. I reckon this balances them on opening and closing which should make the load on the servo less.
Well I think it is good progress, though when I spotted the short aileron I did think about something easier, however I am pretty pleased with the air-brake.
Next is add the rest of the ribs having first added the holes for the trailing wing incidence joiner.
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