Jig for Gussets

Actually...(27 June 2014)

Since my intended gusset material is 1/16" balsa and I don't want to sand the cut/chopped gusset, I shall simply mark the angle against the grid markings of my cutting mat and use that as my jig for marking and cutting gussets. Simple, really.

I have made 1/8" gussets from a balsa strips. I positioned the strip against the grid markings of my cutting mat, this gives reference points at 90 degress intersection. A bit of slicing is required, slicing from the 90 degrees angle towards the 45 degrees angles to prevent bits of balsa breaking off if slicing the other way round. I used a new 11 blade, because it is stiffer than my NT cutter. The problem is not getting the slices perpendicular to the mat. No matter how lightly (and carefully) I sliced, it is not perpendicular. The skew is only a fraction of a millimetre but I can see it and it is more evident when using thin (non-gap filling) CA.

The previous thoughts of using a jig (below) is useless, because it doesn't ensure slicing accuracy and I don't need anything more to know where to slice the strips.

 

Uses

Gussets can be used to position formers, longerons and anything that needs to be set up at a specific angle. It is also very useful because it distributes the stress to a larger area if it is glued in placed. Used wisely, the resulting frame could be made strong yet light. A good examples of gusset use is at the trailing edge and rib juncture, a small contact surface can be enlarged.

There are times when multiple gussets are to be used throughout the frame. Aesthetically, it is pleasing if the gussets are identical. I don't like varying sizes and shapes of gussets when they ought to be identical.

The goal then is clear, to have a jig prepared for marking or cutting identical gussets.

Design idea 

A small base plate (also serving as a chopping board) marked with various angles, i.e. standard 45 degrees and 30 degrees and specific angles of model requirements crossed by the X and Y axes lines. By placing balsa strip of the desired width, place ruler over X or Y axis to cut once, and using the other axis to cut again and repeating the procedure will result in identical 90 degrees gussets with the right proportion of length and width. Skewering one of the axis will result in angled gussets of the same amount. Small blocks may be glued to the base plate to provide positive tactile feedback in case of failing eyesight and guide to the placement of balsa strip and ruler. Guides for balsa strip to be no higher than thickness of strip and the guides for ruler to be higher than the strip. Place them away from the cutting/chopping line of motion.
The limitation to this is that the gusset material has to be easily cut, not too thick, not too hard. When the gusset material is too thick or too hard, then maybe it ought to be sanded.

I don't suppose I will want to sand the gusset edges, but to adopt the same gusset chopping board into a gusset holding jig for sanding, have the edges of the base plate parallel to the X and Y axes, mark the angle line towards the edge and mark a parallel terminating on the other edge.

Construction

I think a 2" x 3" baseplate is big enough for my purpose. Material for baseplate may be thin ply, acetate, formica or even cutting mat. Material for guides is balsa, so that it may be scrapped away if need to.