- Martin Gregorie, © 2012 all rights reserved.
This version of the Saqqara Bird was built in May, 2011 when Cineflix was recording material for William Shattner's Weird Or What? series 2. It appeared in the third section of episode 20, Ancient Mysteries, which was first broadcast in November/December 2011. Three models were built this time: details are given below. They were all constructed from the plan I drew in 2002 for my original Saqqara Bird, which provided the flight data on Larry Orcutt's Catchpenny Mysteries of Ancient Egypt web site. The only differences are that the 2011 Saqqara Bird:
|The plan as a JPEG image. Click for a bigger version.|
|Wing blanks soaked in warm water, glued together with white wood glue and ready to put in the drying cupboard. The blank at the front is the flat wing, ready to be carved and sanded to shape.|
Make these first because you'll need them when you're cutting the wing mount into the body.
Replica wings are laminated from three sheets of 1.6mm balsa. These are cut out and soaked in hot water for several minutes so they're soft and flexible. Glue them together in a stack with white woodworking glue. Now clamp the centre of the wing to a flat board with the tips raised on pieces of scrap balsa to give the wing the curve shown on the plan. Use a rod and rubber bands, as illustrated, or a length of scrap wood and C-clamps to hold the centre of the wing down. Raise the wingtips by putting a scrap piece of 10mm balsa sheet under each tip. This assembly is put in an airing cupboard for 24 hours or until until the balsa has dried out. Once the balsa is thoroughly dry, carve and sand the outer third of the wing's top (convex) surface, tapering it so the tips are 3mm thick. Then sand both surfaces smooth and round all the edges. Note that the original bird's wing section is a thickish flat plate with rounded edges: it does not resemble the cross section of bird or aircraft wings.
Alternatively, a flat wing can be easily carved from a sheet of 4.5mm balsa. If you give it a flat bottom and a curved upper surface with the high point at about 1/3 of the way back from the leading edge the model will fly a bit better and will show much improved spiral stability. Its worth making both wings and mounting them so they can be swapped over to see how much more stable the model is when the flat wings are fitted.
In addition, I made a wing with dihedral to see how much this improved the replica's spiral stability over the flat wing. This is simply a replica wing that was modified to be mounted the other way up so its wing tips are raised above the Saqqara Bird's body rather then drooped on each side like the original Saqqara Bird and, indeed, is how many small garden birds hold their wings when they are gliding.
If you intend to do this, make sure that all the wings you make have exactly the same chord so they will all fit snugly into the wing mount on top of the body.
|Parts of the Saqqara Bird's body. One body has been assembled with white glue. The other is about to be glued together.|
This is made in one piece by cutting the keel, which includes the vertical tail, from 4.5mm medium balsa sheet. The sides of the body are cut from 10mm medium balsa sheet and glued to each side of the body after tapering the rear half to blend in with the tail. Its much easier to cut the taper before gluing the sides in place.
|The wing fits into a recess in the top of the body, where it is retained with a nylon bolt.|
|Carving the body to shape.|
When the glue has dried the top of the body is cut away so the wing fits snugly into the wing mount with its top surface flush with the top of the body. The wing, viewed from above, must not be skewed on the body and, when viewed from behind, the keel must be perpendicular to the wing. When you're satisfied with the wing fit, carve and sand the body to shape.
I use an M3 nylon bolt to hold the wing on. Clearance holes are drilled in the wings and used as a template to drill a tapping hole into the body. This is hardened by carefully running thin cyanoacrylate glue into the hole and, when you're quite certain it has set, tapping the hole with an M3 tertiary tap.
If you're not planning to swap wings, just glue your wing in place.
If you're planning to use a catapult to launch your model, bend the launching hook from 0.8mm music wire and glue it into the fuselage as shown on the plan. Use epoxy glue or cyanoacrylate for this. The body should be grooved so the horizontal part of the wire is inset into its underside rather than simply being glued onto the surface. Doing it this way is both neater and a lot stronger.
The original Saqqara Bird had no tailplane that has ever been found, but all known models of it have been fitted with one. It is worth making the tailplane removable so you can convince yourself that it is absolutely necessary for stable flight.
I made my tailplane 25% of the wing area, which is typical for model aircraft of this size, and sketched a similar shape to the wing. It is cut from 0.4mm plywood and mounted with an M3 nylon bolt in exactly the same way as I described for a removable wing. Another advantage of making it removable is that you'll certainly have to adjust its angle to get a decent glide: this attachment method allows you to put ply shims under it.
The plan also shows a long, narrow tailplane. The vertical fin of the original Saqqara Bird is canted at 10 degrees to the vertical. As its not obvious whether it was made this way or has merely warped in the last 2000 years, I made this tailplane with the same area and approximate shape as the original's canted fin has when viewed from above. Fitting it has no effect on the way the Saqqara Bird flies, but I've included it on the plan because you may want to try that for yourself. Like my 25% tailplane, it is cut from 0.4mm ply and attached with the same bolt.
|The completed Saqqara Bird.|
After the replica was finished, I gave it three coats of 50:50 thinned nitrate cellulose dope, lightly sanding after each coat. The result is that the replica has a smooth semi-matt finish which protects it against getting wet and makes for a somewhat tougher surface.
In 2011 I made a pair of Saqqara Bird replicas. Both were fitted with a launching hook. Saqqara Bird #1 has pockets under its wing mount that carry enough lead to bring its weight up to 21.9g, slightly less than the original Saqqara Bird. Saqqara Bird #2 is fitted with a pivot point half way back along the wing so it can be used as a wind vane.
The wings and tail of both birds are held on with nylon bolts so they can be flown both with and without a tail, the wings can be swapped around and the replicas can be taken apart for transport and storage.
In addition, a third Saqqara Bird was built with its wings, tail fin and body cut from 4.5mm medium balsa and fitted with a 0.4mm tailplane. The wings and tail were permanently glued on and the bird was ballasted to the same weight as the other two. This bird was built so the launcher could be tested without the possibility of breaking the other two birds.
After the Saqqara Birds were built they were weighed and their CG (Centre of Gravity, the balance point) was measured. By convention the CG is measured from the leading edge of the wing and expressed as a percentage of the wing's chord (its width measured from front to rear).
The original Saqqara Bird's weight isn't known exactly, but a target weight of 22.5g was established by averaging the various quoted weights. As a cross check, the Egyptian Fig wood thought to have been used to make the original is approximately three times the density of balsa, which would give a weight of 23.4g.
Saqqara Bird #1 weighed 21.9g when ballasted, an error of 2.7%.
|A Saqqara Bird on the launcher.|
|The carrier block with a Saqqara Bird in place.|
|A Saqqara Bird on the launcher, rubber stretched and ready to go.|
My launcher is mounted on a sturdy camera tripod. This, like almost everything else about it, is non-critical. All that matters is that your launcher:
The carrier block slides inside the alloy guide track and is propelled by a 150mm long loop of 6mm rubber strip. The guide track is a 750mm length of 'U' cross section alloy extrusion, 20mm wide and 12mm deep. The far end of the rubber, not shown, is looped round a piece of 3mm OD brass tube. This fits across the track into holes drilled in each side, where it is secured by tightening a small nut and bolt that run through the tube: the bolt head and nut are wider than the tube's diameter and so stop it from falling out. I drilled these holes every 50mm in the final 400mm of the track so the launch energy can be adjusted by varying the tension in the rubber strip. The brass tube doubles as a stop for the carrier block, which requires four fittings:
As this launcher was to be used in a video I fitted the clockwork timer so that, if necessary, the camera could be positioned directly behind the launcher. This allowed me to put the Saqqara Bird in place, start the timer and be out of shot for the launch. The long L-shaped wire lever, which is soldered round a brass tube that fits onto a small bolt behind the right side of the guide track, is there to minimise the load on the timer. It swings out to the left on launch, releasing the carrier block.
Although using the timer adds a nice touch, it isn't essential Replacing it with a long screw to act as a manual catch would work just as well.
The Saqqara Bird should balance at the trailing edge of the wing or slightly forward of it. Bend the rear edge of the tail for as steady and flat a glide as you can manage. Bend it up if the Saqqara Bird dives and down if it stalls. My Saqqara Birds have all required the tail to be bent up. The Saqqara Bird should fly straight if you built it accurately, but if it doesn't you can make corrections by bending just one side of the tailplane. The bird will turn toward the side if you bend it up and away from it if you bend it down.
I've now carried out some flight testing flight testing with my pair of 2011 Saqqara Bird replicas. I'll be very interested to see the results of anybody else's tests.