HPA
Outdoor Free Flight Forum => Rubber => Topic started by: Jmk89 on Oct 04, 2026, 08:35 AM
Today saw the start of actual building of my attempt to replicate John O'Donnell's Hatband Coupe model (for the earlier attempts to find information and discussion on how certain design features were determined, see this thread (https://hpa.aeromodelling.gr/index.php?topic=385.msg6234;topicseen#new)).
I started by setting out the wing outline.
HB Wing outline.jpg
As the picture shows, the tip is a laminated outline (1/4" x 1/32" x 3 laminations). The leading edge is 3/16"sq balsa shaped by clipping the front top corner down to about 1/16" above the building board. The LE in the tips is soft, that in the centre panels is medium. The TE is 1/8"x 3/8" balsa shaped using my tilted sanding block (https://hpa.aeromodelling.gr/index.php?topic=397.0) to give a 1/32"rear edge - again the density of the balsa differs, with medium in the tips and medium hard in the centre panels.
I also have produced the straight wing ribs:
HB Wing rib block.jpg
This photo shows the sandwich with the blanks glued together using glue stick and the templates attached to the blanks using double-sided tape.
HB wing rib block shaped.jpg
Here is the "block" after shaping using razor plane, rasps and sanding blocks. The eagle-eyed may notice that three of these are 1/16" thick and the rest are 1/32" - the 1/16"ribs go at the dihedral breaks. Also some of the ribs are darker than the others - they are medium hard balsa for the centre section panels and the lighter coloured ones are medium soft for the tip panels.
HB wing rib block immersed.jpg
And then into a butter tub containing isopropyl alcohol. They should have separated by morning, and then can be laid out on newspaper to dry.
Tonight is the National Rugby League grand final and, although it is not usually something I take much interest in, one of the teams competing is the Newcastle Knights. I spent two years in Newcastle as a kid which I enjoyed greatly so I have a soft spot for the city and would like the Knights to win. So I may shape the diagonal wing ribs while listening to the radio broadcast.