Let’s start working on the upper wing center section. Like all FLYLINE products, this is a printwood kit, but I found this one at a swap meet with many of the balsa parts already roughly cut out of the sheets. (One thing I checked carefully before buying it was to be sure all the cutouts had been made oversize, without any parts being cut off short.
- Here are examples of a lower wing center section rib at three different stages of “cutting out”. The rib at the top might as well still be in the intact sheet…I cut closer along the ink lines, and then sanded the edges to get the middle rib, which is the final trimmed part. AFTER all the outside cuts were made, I cut out the spar notches and trailing edge indents using a SHARP No. 11 blade. Right here is the place where all the old time stories you hear about breaking and splitting parts come from.
- Here’s where the fun part begins. The kit provides an array of stripwood, both spruce and balsa, every dimension with a specific function. Each piece must be measured and sorted to determine what is supposed to be used for, and then cut to correct lengths. Here you can see the 3/8″ x 1/4″ balsa leading edge, the 1/2″ x 1/8″ and 3/8″ x 1/8″ spruce main and rear spars, the shaped center section trailing edges cut from 1/2″ balsa printwood, and the spar joiners, cut from 3/16″ x 1/2″ and 3/16″ x 3/*” spruce and then cut precisely to the correct angle to provide outer panel sweepback. The secret is to take your time and get it right.
As you can see by looking at the curved profile of the bottom edge of the ribs, it's not possible to build the wing by assembling the spars and ribs flat on the building board...they won't lie flat. I made a simple diagram using a rib cross section do determine the exact stand-off distance of the bottom of each spar from an arbitrary bench top reference, then cut 1/4" and 7/32" shims from scrap balsa to support the spar sections in correct alignment during assembly.
Here's what the center section looks like spaced up off the board with all the ribs assembled over the spars and the leading and trailing edges in place. The dark blocks are small magnets that I'm using as building weights here, and the clothespins serve as clamps to secure the tapered spar joiner sections.
This is the upper wing center section assembled, ready for the addition of various gussets and strut mounting hardpoints and then sanding. Getting to this point makes you feel as though you are accomplishing something of value.
Good day Bob, how did you manage to get the angle cut in the spar joiners? I’ve made 3 attempts so far with a coping saw and just can’t seem to keep the saw square throughout the entire cut. Is there a trick?
Jim,
There are a couple of ways around your problem. When you mention a “coping saw”, do you mean a power tool such as the Dremel, or a hand coping saw (a long,thin blade held in tension in a “C” frame)? The hand version would probably be so wobbly that even the most expert hand would have difficulty making a straight cut. A wider blade would help, if that were your only option. The same applies if you are using a power tool…the narrow (about 1/8″) blades wander too easily. Use the widest blade you can get. In either case it’ll be hard to get a perfect cut. If those are the choices you have for tools, my fix would be to cut oversize (leave a little extra material outside the line) and then dress the cut part using a big sanding block .
The easiest way I’d recommend is to get a hobby razor saw (X-Acto, Zona Saw, etc.) and use diligent care to let the long, flat blade keep the cut straight for you as you work. A miter box would be a big help in doing this, but you’d need one with enough adjustment to define exactly the angle of cut that you need.
The ideal method (do you cabinetmakers out there agree?) would be to use a table saw with a guide fence adjusted to hold the part at exactly the required angle. I don’t have one, so I used my big band saw, left some extra wood for a trim, and block sanded the final cut to the exact dimension I wanted.
Let me know how it works out for you.
Bob
Bob, I was using a hand coping saw with a very thin blade. I like your hobby razor saw idea. I experimented last night with laminating 1/8 in layers that were easy to cut with good accuracy. I had excellent results. I also constructed the trailing edge by laminating layers, and cut it from a sheet as one piece instead of two as in the plan.
I just came across your blog today and I was going through your stages of building this model. On this step there are a few illustration pics missing.
I ordered this as my first model back in 85′ when I was overseas in the Navy. I built it to about 75% before I wound up selling it. There are some many things I would do different today if I were able to get another kit. I am enjoying viewing your building process. Thanks.