Pete's Projects
Components
(a) Main body.
(b) 32mm body locking knobs (a pair)
(c) Wing jig mounts (a pair)
(d) Pivot bolts 50mm total of 4.
(e) 6 100mm or 70mm Rod holders + 6 small pressure plates (white) shown installed.
(f) 8mm or 6mm hole drilling guide.
Also a set of 10 rib spacers (size as nominated by you)
You will need.
(A) 2 x 19mm square aluminium tubing, length to suit wing panel span.
(B) Four rods of the same length in either 8mm - 5/16” or in 6mm - 1/4”depending on the support diameter you have chosen
Rod Size & Materials Choice
Either size will work, whatever sizes are available in your area will be fine.Yes, larger diameter will be stiffer, but either size is ok, the smaller size could be ideal if you are working on thin wings and are concerned that the thicker one may not leave enough “meat” around the holes.
(My preference is for Aluminium arrow shaft made by Easton, as these are straight to within a couple of thou. and are very stiff and light. Easton 2016 shafts have a diameter of 20/64” (5/16”) and a wall thickness of 16thu. There 1616 is 16/64” (1/4”) Dia. and again 16thu. Wall thickness. Arrow shafts are shorter, a 2016 will be aprox. 30.5” long, a 1616 aprox. 29”)
Aluminium rod would be fine, make sure it’s as straight as possible. Carbon Fibre rod in 6mm, or tube in either 6, or 8mm would be fine, as would K&S brass tube. You could use piano wire in 6mm or 1/4”, but this is quite heavy, and not my preference
Jig Mounting
I suggest mounts the brackets flush with the edge of your workbench using threaded inserts. This will allow you to rotate the jig so that the ribs will overhanging the workbench, either with the LE or TE facing up, you can also flip the jig around so that the opposite edge faces you. Thus giving you far greater access to the wings structure.
Fit a pair of threaded inserts 340mm apart (as per photo)
Basic Assembly.
1. Measure in 10mm from the end of each of the tubes and mark a cross line, do the same at 118mm. You should now have two hole centres marked 108mm apart, 10mm from one end.
2. Centre punch, and drill two holes 6mm diameter fully through the 19mm tube.
3. Debur the holes and all four ends of the tubing, as well as filling a bevel on the four corners of the tubing. (This makes sliding the shaft supports on and off the tubes easier)
4. Fit the pressure plates to the shaft supports, and slide 3 shaft supports onto each of the aluminium tubes.
5. Slip the tubes into the body, and secure with the four 50mm long threaded knobs and thumb nuts.
6. Slip the large washers onto the 32mm. threaded knots and screw one into each end of the jig body.
7. Mount the jig body between the pair of support brackets.when building flat on a workbench.
PLEASE NOTE.
Finger tight is all you need, especially the locking collars on the shaft brackets, these take very littler pressure to hold them in place.
Setting Dihedral Angle.
Measure out 575mm from the pivot (Arrowed) and mark a line across the tube. This is were you will be setting your dihedral angle. With both arms set level you should have a distance of about 80mm from the bottom of the arm tube to the work bench.
To set a dihedral angle add the mm shown on the jig body to the 80mm (flat distance) to get the angle you want. So for 3 degrees you want a measurement of 111mm (the 80mm under the arms plus the 31mm listed on the jig body for 3 degrees) The exact measurement is not that important, as the measurements 575mm out along the arm means that in round figures, 1mm is equal to 1/10th of a degree, more than accurate enough for most modellers.
Drilling Holes
Work out were you want the holes in the ribs and using the drilling guide drill the appropriate size hole depending on your rod diameter using either 100, or 70mm hole centres.
Hole Position - Anywhere you like.
My preference, have the rod holes behind the main spars, this gives you better access to all areas of the wing.
In a typical “D” box construction, this will allow you to complete all top and bottom L.E. sheeting as well as all cap stripping with the wing on the jig. Basically everything except the wing tips.
I like to drill the rib templates, and then use these same holes to hold a block of ribs together to produce a set of ribs. In the photo I have drilled another hole in front of the main spars simply to help hold the rib block together.
Rib Spacers
Using pegs, or the little spring clamps shown simply. clamp the spacers between the ribs, they will hold the ribs straight and square.Take a little time to get the first one or two positioned correctly.
Tips.
1. I like to work from the tip rib into the centre section, if that means there is a rib more than shown on the plan , so be it, (an extra rib in the centre section can’t be bad) or, use a different set of spacers, and or reposition the last couple of ribs.On the wing shown I used the 70x 60mm spacers to produce the wing panels, and the 50x45mm spacers for the centre section.
2. With a set of 10 spacers you can position the ribs on one panel then add the spars to hold things in place,then remove them and do the same on the other panel (or use extra spacers depending on the wing span you are building.)
Rod Supports Positions.
Slide one support up as close to the main body as possible, position another around the mid point and the third just outside where the last rib will be.
Exact positions are not critical (one at each end, and one in the middle)
Tips.
1. I like to use off cuts of Laminex for rib templates, yes its a bit harder to work but it lasts very well and you can “feel” when the razor plane or sanding block has reached the final size.
2. If you lay the rib template onto the balsa sheet and take a washer, (say 3 or 4mm) and run around the template with a pen in the hole you will have a rough-out rib approx. 3mm oversize all round.
