I won an Ebay auction with parts to the Egg Crate, and they arrived today:
The chute wadding was an unexpected bonus, but the 1970 A5-4 motor caused me to cringe a bit. Priority mail ain't the way to ship those things
Measurements are:
Payload tube - ST-20, 5" length
Body tube - ST-16, 12" length (note balsa coupler glued in one end - more on this later)
Nose cone - 2.5" bezier, exact match to Semroc ST-2026
Fins (I will scan and send in patterns on Monday):
Root chord - 3.0"
Tip chord - 1.7813"
Sweep length - 2.2813"
Sweep angle - 45 deg
Semi-span - 2.2813"
Launch lug stand-off:
Root chord - 2.0"
Tip chord - 1.625"
Sweep length - 0.1875"
Sweep angle - 45 deg
Semi-span - 0.1875"
As you can see there are 2 launch lug stand offs on each sheet. I sincerely doubt this puppy uses all four, but suspect it does use two.
I puzzled over the lack of a balsa adapter, and originally thought it had been lost with the instructions, decals, motor tubes, etc. I also could not figure out why there was an ST-16 balsa coupler glued into the body tube and why a paper ST-20 coupler was in the parts. I did some ciphering, and figured out that using a Semroc BR-1620F adapter would put me at least an inch over the rocket length given in the catalog.
I couldn't figure out what was up, and had about decided the length was a typo.
Then it hit me...
I went over to the parts section of the 71 catalog, and noticed there was no balsa adapter to connect a ST-16 to an ST-20 - there was only a paper one, the PR-1620, which had a shroud 1 " long.
Mystery solved - I think.
The Egg Crate used a paper shroud - seems kinda crazy for an egg lofter - and part of the ST-16 (over an inch) was used in the construction of the adapter. The balsa coupler was then used to connect the adapter+payload section to the body. Length problem solved.
Does anyone have any instructions to verify the above (and also to tell me if 2 launch lug stand offs were used)? Pretty please?
I am planning to clone this, but may make life simple and use a Semroc BR-1620F - at 1.2", it is a little longer than the PR-1620, but a 10.5" body tube would provide a match to the catalog length. That would save the trouble of constructing a paper one, and eliminate the need for a balsa coupler.
Now to work on drawing the decals - looking at the pic on the inside back cover of the 71 Centuri catalog, they consist of a black and red roll pattern, and a couple of lines. Also looks like 2 horizontal strips of silver foil along the egg capsule.
Rocksim file with correct fins and using the BR-1620F attached.