Construction Rating: | starstarstarstarstar_border |
Flight Rating: | starstarstarstarstar |
Overall Rating: | starstarstarstarstar_border |
Manufacturer: | Sunward Aerospace |
Style: | Pyramid |
Brief:
Khufu's Pyramid is a high drag pyramid rocket that flys on 24mm motors. It is
an unusual rocket that has a solid construction and uses a rear core ejection
to recover in two pieces. It comes in a plastic bag with the usual art card.
Construction:
Kit consists of:
To build the kit I used:
The instructions are clear and straightforward, with several diagrams and photos to help illustrate what to do.
The 8 balsa triangles confused me slightly, the grain runs parallel to the base of the triangles, which would give weaknesses on the corners whereas the structure would be significantly stronger if the balsa grain ran parallel to the hypotenuse. Each of the triangles need the hypotenuse sanded down to a 45 degree angle. The cardboard shroud acts as a mold onto which the 8 triangles are directly glued. It is best to test fit everything before gluing and not to use too much glue as the paper may warp. After everything has dried, a Plasticine mass is added to the apex. If flying on C11 or D12 motors, then 60g is added. If you want to fly on E motors then more is needed, but the instructions do not state how much. This is the only flaw that there is with this model--you have to choose either C/D or E at the build stage and there is no way to alter the mass once the rocket is built. After the Plasticine is added, a plywood bulkhead is added once its edges have been sanded at a 60 degree angle. The bulkhead is glued in with epoxy.
While everything is drying, glue the launch lugs to the coupler, which is used as a guide to mark the point to drill a hole in the pyramid. Drilling the hole is probably the hardest part of the build and would be difficult for younger modelers. After the hole is drilled, the coupler is glued against the bulkhead. Leave the launch lug sticking out of the side of the pyramid.
I "washed" the inside of the pyramid and coupler with thin CA glue, mainly to fill any gaps missed in the previous gluing stages and to strengthen the coupler. The rear base plate is then sanded to 60 degrees on its edges and has the elastic shock cord tied on. It is then glued into place after sliding it over the rear launch lug.
The kit comes with an 18 inch chute. This has to be constructed in the usual way. I swapped this for an 18 inch solar Estes chute, mainly because I could not be bothered making another plastic bag chute when I already have dozens in my recovery box.
The lugs are then trimmed flush. Then you glue a thrust ring in one end, and a motor clip and plywood centering rings to the outside of the motor mount. I altered my retention system by removing the clip and adding to blind nuts to the rear centering ring. The rocket does not need this type of retention, but I've never used blind nuts before, so I thought I would have a go with it on this rocket. This should allow me to use D and E motor as well as 24 RMS motors.
A streamer is added to the motor mount. When prepping for flight, the streamer and the parachute are not to be wrapped around the mount.
Finishing:
I sprayed one coat of cellulose sealer to proof the paper shroud followed by
three coats of spray paint. Thats all it needs, however, I went a bit
further and sprayed one side with a star motif and the adjacent side with the
contrast color. The art card that comes with the kit shows a blank, white
pyramid. No decals are included
Construction Rating: 4 out of 5
Flight and Recovery:
Prepping is straightforward as no wadding is required. The parachute and
streamer are placed on either side of the motor and then I loosely wrapped the
shock cord around both. The core is then inserted into the coupler. Being a
heavier rocket, a 5mm rod is used.
First flight was on a D12-3. A C11-3 is recommended but I reckon that this would be marginal on power. The pyramid gave a good flight and was a real crowd pleaser. Altitude was low, which was expected, and ejection was late but the parachute opened with plenty of time to spare. The core recovered quickly on the streamer.
Second flight was with an E9-4, this isn't a recommended motor but it should be. The flight was fantastic, however, the parachute did tangle with the streamer. This was probable down to my hasty packing.
The third flight was on a D12-3. I did not use a stand off on my pad and there was a degree of charring to the base of the model. I cannot believe I was that stupid.
Flight Rating: 5 out of 5
Summary:
I really like this rocket. Its construction is a bit different from the normal
affair, and the finished product is robust and gives good flights even on more
windy days when a more traditional tube rocket would have to stay on the
ground.
Overall Rating: 4 out of 5
Brief: Khufu's Pyramid is a nice low flying, high drag rocket. It is 6" tall and 5.25" wide. Construction: The kit comes with cardstock for the template and skin of the pyramid. It also has 8 triangle pieces that make up the 4 sides. A 24mm mount is included along with a streamer for recovery of the motor mount. The parachute is a nice and thick. The instructions ...
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