Slicing curved strips

21 December 2023

1/16" x 1/16" laminated curved ribs from 2 x 1/16"x1/32" strips

A former of 1/16".

From 1/16" balsa sheet, cut according to the curvature to separate upper (concave) half and lower (convex) half.

1. On the assembly plan, draw parallel lines, inner set being width of upper laminate, lower set being width of total chord and tape to building surface.
2. Cut equal sets of upper and lower laminates, soak for 5 minutes.
3. Pin upper former over the plan.
4. Start layering laminates: upper, lower, upper, lower with thin white glue between upper and lower but not lower and upper.
5. Pin lower former over the plan, pushing against the sets of laminates.
6. Adjust the upper laminate so they match against the inner set of lines and the lower laminates so they match the outer set of lines.
7. Leave to dry. 
8. Remove laminated sets and clean up.
9. Trim the lower laminates by using spacer/s, cut perpendicular.
10. Cross-pin laminated ribs, push to match leading edge follow by the trailing edge.
11. Remove wing and trim lower laminates.
12. Sand smooth.  

Since the laminate is from 1/32" thick balsa, use scissors for quickness, razor blade for accuracy to cut and some sandpaper to trim.

Since the curvature is slight (for camber of 2-6 degrees), perhaps a jig using 3 pressure points is good enough. This type of jig would not be suitable for wing tips, exact shapes or multiple curves. 

Since the laminate is from 1/32" thick balsa, must the laminates be wetted, must white glue be used? Perhaps strips can be dry-laminated with superglue, which will be fast and maybe good enough?

14 December 2023

Going back to the idea of laminated ribs: 1/32" leading and trailing strips and ribs from 2 laminates of 1/32".

• A piece of 1/32" balsa sheet to the length of the overall chord and marked with 2 parallel lines showing the back of leading edge and front of trailing edge.
• A piece of 1/32" balsa sheet to the length of the 2 parallel lines.
• Glue the 2nd sheet to the first sheet and while wet, tape/bound to a round cylinder. No need to bound all around because the rear chord has less curvature. Leave to dry.
• Strip for ribs from the formed laminated blanks.
• Pin and glue the ribs to the leading and trailing edges, one edge at a time.
• Trim/sand the ribs to the leading and trailing edges. 

Instead of a former, if the wet blank were pinned to well placed strips, it would achieve the same result.

The ribs can be laminated upside down, with pinnings on the leading and trailing spacers (which determined the height of the camber) and then pinned down to the building board. Reversing for use, the rebates preferably be at bottom.

The ribs can be laminated upside up with a single spacer (which determines the height of the camber) and the leading and trailing edges pinned/clamped down to the building board. The rebates are at the top, naturally.  

13 December 2023

For a curved strip (non-preformed; sliced from flat sheet), the two ends may be vertical, horizontal but hardly likely to be notched (because it can be avoided).

For vertical ends, such as those with substantial leading edges (unlikely for the tapering trailing edges):

• Prepare and cut a flat sheet to the chord length,
• Cut the curved ribs from top down.

For horizontal ends, such as those with tapered trailing edges:

• Prepare and cut a flat sheet wider than the chord length,
• Mark the chord length,
• Mark the horizontal lines,
• Cut the curved ribs from top down, leaving them connected at the waste area,
• Cut the horizontal lines from the bottom of the rib blank individually.

4 December 2023

The solution of 18 August 2023: Having notches (and gaps) in the leading and trailing edges is using more material (=weight & more stress points). 

18 August 2023

Cut using template going down each time results in strips' ends at an angle that doesn't fit leading and trailing edges strips that were laid flat.

If each rib's end is trimmed square, only one edge can be attached while either the leading or trailing edge is flat on the building board, meaning that the ribs are built 'up-side down'.

By laying the leading and trailing edges with packing underneath can allow the strips to be installed 'right-side up'.

By having recesses at the leading and trailing edges, the strips can be assembled 'right-side' in the hands and then pinned to glue and there is no need to trim the ends of each rib. However, it won't fit perfectly when it is assembled in the air, so packing material underneath the leading and trailing edges will ensure accuracy while one tries to adjust each end of the rib.