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Tuesday, January 15, 2008

Chuck Glider from one 1/16" balsa sheet: Part 3, Building

I've been building at night and it has been murky and overcast lately, so apologies for the dark pictures. Here we go step-by-step:

Photo 1. After looking at the grain, deciding which side will be the wing and fuselage, make the first cut dividing the sheet into 17" and 19" pieces. (NB. the final version requires an 18" piece for the fuselage, not 19" - see Part 5 of this series of blogs).


Photo 2. Marking out the fuselage. Cut a 22 mm strip from the 19" piece and then mark 4 mm at each edge.


Photo 3. Here are the fuselage sides, fin and stab cut out of the 19" piece. The back of the right hand fuselage side is trimmed to accommodate the fin. See photo 4. When deciding which piece should be which, ensure that any natural bow in each side opposes the other. This helps to prevent a banana fuselage! (But don't worry if you get a bend, as it can be steamed out easily over a boiling kettle).


Photo 4. Note sharper taper over last few mm of fuselage. Glue the fin in place and then the fuselage sides together. Use PVA and spread it out thinly on both faces.


Photo 5. Place a steel ruler and weights over the whole fuselage and fin assembly while PVA dries.


Photo 6. Shaping the wing. First, round off corners and the LE. For the slope, I felt that sanding the top surface from 33% as originally planned may compromise strength. I decided to taper from 50% of chord. Take care with the razor plane! The blue masking tape prevents errors with the sanding block.


Photo 7. Sanding wing break joints. The sanding block face is kept vertical, and the tip is placed as shown to get the right slope. The middle panel joints are sanded while it is flat on the board. With care, it is easy to get a good joint with such a thin wing.


Photo 8. Wing glued up. Middle panel weighted and tips have light weights (balsa off cuts) just to keep it all lined up. I used Araldite Rapid epoxy, spread evenly on both joint surfaces, but thinly.


Photo 9. Here are all the parts ready for assembly. I made a throw tab - it adds strength to the wing-fuselage joint and would be useful for duration tasks. The long thin piece is the nose skid.


Photo 10. Use CA to glue on the skid, and rubber bands to hold it while it dries. Looks like the nose will be quite strong, so I would be able to taper it later for a better appearance.


Photo 11. Thin the stab. You should be able to see translucent light through it near the TE.


Photo 12. Sand the fin thin as well.


Photo 13. All aligned and glued up. Rubber cutting mats are great for this. Use a set square to ensure that everything is square, especially the fin is perpendicular to the stab (while the stab is flat on the mat).


Photo 14. Check tip heights before the glue dries!


Photo 15. Shape the nose. The skid ensures some strength.


Photo 16. Glue and shape the throw tab - note grain direction. Not easy to see at this angle, but the skid overlaps the sharp end of the tab by ~ 5 mm.


Photo 17. Add blue tack to balance at about 1 1/8" in front of the TE, that is about 63%. Total weight came out at 10.4 g.

All done, lovely!

2 comments:

Anonymous said...

buxZED

do we fix the main wing on sloped fuserlarge or do we have to sant it till horizontal?

Chuck Glider said...

The intention for this model - remember it's for a special event, it's not a typical chuckie - is to fix the wing to the sloped fuselage. In fact, that's the reason for the (slight) slope.