Edmonds 2-stage CiCi2 and more glider repairs
Here's another glider repair project, but this time the damage wasn't due to shotgun ejection charges. Instead, it was due to my own mistakes.

The CiCi2 is an absolutely brilliant design from Rob Edmonds combining gliders, staging, and a big gap between the motors. In the pic at left, you can see the blue sustainer and the gold booster. The white band at the lower end of the gold tube is the booster motor. Above that, at the forward end, is the gap staging vent hole just below the black motor pod of the sustainer.

Also visible are multiple repairs to the gold booster section.  There's a plate over the knitted booster spar just aft of the forward wing.  And there's another diagonal plate, even with the booster motor, which reinforces the joint between the booster motor pod and the main airframe spar.
The gap staging has always worked perfectly, and required almost no special preparation other than ensuring the sustainer motor nozzle was cleaned out. I was always concerned about not having enough friction joining the booster tube to the sustainer motor. This would guard against premature separation at staging, but it has never been an issue.

My mistakes with the bird were not trimming the sustainer to turn and not spending enough time getting a decent glide out of the booster. The results of the poor booster trim are evident in the pic, as mentioned above 

On its last flight, both mistakes combined to doom the bird. The glider flew in a straight line away from the range head never to be seen again while the booster dove into the ground and became a pile o' parts

At right is a quite blurry pic of the fateful last launch. 



In the pic at right, you can see where the booster motor pod separated from the main spar. The joining plate from the previous repair is in the upper left corner.

My great sin here is having never gotten the booster properly trimmed after the first wreck.   The second wreck should never have happened (although the fly-away might still have).


Yet again I rebuilt the booster section.  And this time it finally got a decent trim. A key to this was adding some incidence to the forward wing when it was glued back on.  Basically, I deliberately misaligned it to do this.



In the pic below, it is hard to see the misalignment, but the left end is turned up slightly making it sorta swayback.  A piece of 1/64" plywood acts as a gusset over the splice.  The repair is near the forward end, just aft of the canard.




The motor tube, at the forward end, was also damaged in the wreck.  A wrap of kraft paper makes it good as new.




Having gotten the booster done, I set about building a new sustainer.  The CiCi2 upper stage is not quite identical to the single stage version. Foremost, it's longer by about 3". The other differences are more subtle, and I'm not sure I managed to cover all of them in the replacement. Without the original, I had to use my single stage version as a model, and it's not totally stock since its last wreck - for example, I had to swag some of the details on its new motor pod.

One of the subtle differences I found was the angle of the motor pod on the CiCi2. It had to be reduced considerably versus the single stage version in order to get it aligned with the booster pod. In this reincarnated CiCi2 (left), the motor pod is nearly parallel to the forward wing versus an angle of about 6° on the single stage version (at right in the pics below). Other modifications include the dual vent holes in the sustainer pod and the kraft paper reinforcements at the pylon-motor tube joint, both to guard against the nuclear ejection charges. 

(By the way, the 6° incidence of the CiCi at right proved to be way too much.  It looped off the rod and power pranged requiring yet another overhaul of that rocket )


Ever since I saw Tim Sapp break his Flat Cat hand tossing it in my yard, I've wanted to try carbon fiber for the main airframe spar in a glider. In the shot at left, you can see the 1/8" CF rod sandwiched between the dual 1/16" thick pylons. Inside the motor tube, the shiny part is where I applied some thin CA and then sanded it smooth. This will help protect the tube against the "fuzzies" caused by repeated motor insertions/extractions.


The aft pylon is shown in the pic at right.  The 3/4" long, faint white line midway along the length of the pylon is the thick CA used to tack the CF rod to the pylon. Once that set, a piece of 1.5oz glass was applied over most of the pylon's length.



Another of the subtle differences between the single and the 2 is the height of the rudders. I can't remember for sure, but I seem to recall they were a bit taller on the CiCi2 sustainer. And in the pic at left, you can see that they could stand to be about 3/8" or 1/2" taller in order to touch the booster wing, which, as I recall, they did on the original.


At left is a pic of the entire bird. I have some blue dye, and I'll mix a spoonful of that with a bit of alcohol, then swab it on the bird to give it some color. That will make it easier to track, and the alcohol will dry fast thus avoiding warpage due to moisture. Given that I'm off work for another few days, I ought to be able to get this thing up in the air soon.


With some blue dye on the new upper stage, it looks pretty good.  The repair gusset between the motor tube and main spar of the booster is visible at the leading edge of the wing.  Some balancing clay is seen at the very bottom of the pic.


Here's a liftoff pic of the rocket's return to action.  I can't recall any of the the details.  My notes say it flew on a B6-0 to A8-3, and that the motor didn't eject from the sustainer pod.  [Sometimes you can't win for losing.]   The notes also say the booster was too tail heavy and that the sustainer needed to be trimmed for turn.

So I have some more work to do before I fly this one again.  But now that it's repaired, I look forward to flying it some more.


Doug's Rockets Homepage

12-27-2008