Wing Jig-its are a tool for
supporting the construction of model airplane wings on any number of surfaces.
It is used as a wing leveling system. This system has been proven and comes
from the early 1920’s when wood wings were the method of the day. In the model aviation discipline, it is a great tool to build flat, straight wings that ultimately fly well.
The single Jig-it is use in combination with others as a system to support wings while they are being built. Each Jig-it is made from durable material, traditionally aluminum but in this case Maple. Maple is solid, without cracks, has the consistency of a plastic, and can be worked with hand tools and can be finished with your favorite varnish. It’s durable, and holds its settings well.
Jig-Its are attached over the plan, on the perimeter of the plan so that the guide blocks are just inside the edge of the plan. In this example they are attached to the work surface with a typical drywall screw and can be removed and re-positioned if required. This wing is 42 inch span and I felt that 4 per panel was not quite enough. I added a few more to make 6 per panel.
I created the leading and trailing edges and prepared to install them in the guide blocks tightened by hand. The Trailing edge did not need any prep, it jigged in easily. The leading edge is a diamond and is attached to each rib on edge. I had to add some triangle stock to make some landing pads for the guide blocks.
This is only for the leading edge if the leading edge is installed into ribs on edge, otherwise no simple modifications to spars are needed. These nubs are removed and trimmed off later in the building process.
Once these spars are jigged up they can be leveled. Initially they are raised up by the use of a straight edge ruler measured from the plan work surface. This gets things close, then they are leveled by a small sight level at each jug station and between. I used the Level App on my smartphone and it worked but a good small mechanical pen sized sight level will also work. I got the reference for my App level zeroed or calibrated by placing it on the concrete floor and making it zero set. Then I used the level app and raised and lowered each spar to a couple a 10th’s of a degree on the level. I had to lower the leading edge slightly as it was high but measured is on the spars center line all around so that the leading and trailing edge center lines were all at the same measurement.
At this stage our wing is ready for rib construction and installation. Leading and trailing edges are captured in the Jig-Its, and have been leveled. During the building process, a leveling process is routinely accomplished to ensure things remain as initially set. If a builder wished, wash-in could be incorporated in the wing at this time. This example is a wing that is symmetrical so no washout was applied.
Wing ribs are constructed in the stacked rib method with plywood templates of the tip rib and the root rib. The image above is a set of ribs for the left or right wing.
The images above are some steps in the development in carving a series of ribs. Details of this process can be found in other areas of the internet so instructions are abbreviated here.
A series of completed ribs are laid over the plans for judgement process, length and placement. In this case they passed inspection. In the past errors in rib making resulted in a set of ribs that were too short requiring the set to be rebuilt.
However, ribs are made in any fashion that suits your building style. Some designs are not so simple and cutting out each rib by hand is the only way. This design had a straight trailing edges and this lent itself to stacked rib construction easily enough. Root and Tip templates were made and then rib material is bolted between. Sanded and carved to shape delivers suitable ribs for half a wing. Procedure is duplicated for the opposite wing half. Ribs are left long deliberately and cut to the exact length when installed in place.
Ribs added one at a time, cut to length and installed, one at a time until completed all ribs. This will make a reasonably rigid structure that can be removed from the jig system and then inspected. In this case they were added from the tips towards the center. for both panels at the same time. Ribs spacing and length are trimmed one rib at a time and the jig is checked for settings along the way.
This last image is a check for straightness out of the wing jig. The wing can be removed and then re inserted. It can even be put back in the jig flipped over
This particular wing is spar less, but could be placed back in the jig and top and bottom main spars added at this stage. This wing gets sheeted fully and in this case strength is from the fact that the wing sheeting is attached to each rib. The wing design is from a aerobatic class airplane and was an interesting project in that the wing is spar-less. There is no main spar and the strength for this wing is incorporated in the Skin. The wing is fully sheeted and there are more ribs than typical. This construction resulted in a very stiff wing that is very strong overall. One of the lightest wings that I have completed.
Weights are being used as well as pins to do the sheeting process. Bottom of the wing was sheeted first. This process was don in the jig. The jig is plenty strong enough to hold the wing in place even with all the weights.
The wing can be removed, inspected, flipped over, reinstalled and with this jig, because the wing is straight, it is easily placed back into the jig as needed.
Further progress in sheeting is being completed. The wing is now ready for sheeting on the top side.
The advantage of the wing remaining in the jig is that the system is strong enough to support the wing while sheeting work is done. Top and bottom are completed in this method. One could have removed the jigs at this stage and completed sheeting on a flat bench but the jig holds things in place well so that weights and pinning of sheeting and parts can be made easily.
At this stage I was running out of things that are heavy, included is a roll of solder and a small crocodile paper weight.
Bottom sheeting process is the same as top. Carpenters glue is used for sheeting as it gave time to work the sheeting in place. Pins work, even though I am not fond of the use of them. Perhaps slow set CA glue could do.
Once sheeting is done, the jigs are removed from the workbench and the wing can now be completed in the usual fashion. Tips and Ailerons built to requirements.
Once the wing is sheeted, the Jig-Its are removed and the wing gets its sanding and shaping, leading and trailing edges with the ailerons. No more use of the Jigs at this time they have done their job.
Later stages of the aircraft build whereby the wing is installed into the fuselage. An expanded treatment in the use of this jig with this project can be found in the online forum Hip Pocket Aeronautics. DFH-21
For now this completes the presentation for these wing Jig-Its and a PDF file can be found here on this site. If you want to have a go at building your own set of Jig-Its here is a master file. They are labor intensive to make and need the right choice of maple. So a set of completed Jig-It’s can be obtained through this website in our Store Section.