LOL $27.50 1972 dollars is about $197 in 2024 ... our club bought a pair ($49.50 in the catalog) that did seem like a huge investment at the time!

__________________
David Stribling
NAR 18402 SR
But it is rocket science!
Get yer Barrowmans here

Hi David,
Thanks so much for all the wonderful information you have provided and are still providing on this very rare vintage Centuri model rocket tracking equipment! I had searched previously and located the instructions on the YORP site (thanks to Jack Komorowski and Scott Hansen for providing the Sky-Trak instructions!): https://plans.rocketshoppe.com/pubs...ri/sky-trak.pdf . So far, I had not been able to locate the other information that you provided today, thus, that is the reason for me starting this thread and asking the questions. I am extremely glad that you have all of the elements to the set including the Sky-Trak(s), the Centuri Altitude Computer with instructions, and the Centuri Flight Data Sheets. All of that is exactly what I was hoping for. If you are able, it still would be great to see up-close, clear photos (with some overall dimensions) of the actual Altitude Computer sheet, clear plastic arms, and the clear Sky-Trak protractor that goes with the Altitude Computer. Looking forward to seeing more if you can share the additional images and dimensions please! Thank you!

Hi Earl,
Somehow, I was thinking that you might also have one of these Centuri Sky-Traks. It is good to know that you do! Have you been able to inspect/inventory it even though you said you have not assembled it yet? I have a friend who is sending me one also, that I hope to have soon, so I am attempting to gather as much information on it as I can find. David (Rocketguy101) and I, as well as you and I, have collaborated on some significant Centuri model rocket history items in the past, so, if you guys agree, I am hopeful that you and David (Rocketguy101) and I can all collaborate to help document this equipment and create patterns so that others can potentially construct their own as well, if they wish. Today is a great start with everything that has surfaced so far!

David Stribling and I both have 2D and 3D CAD software that could help facilitate accomplishing my ultimate goal of documenting this equipment, for the benefit of all, if y'all are willing and able to help on this project. What do you guys think?

Another couple questions that I have for both of you guys is how long is the sight tube and is there more than one of the white vinyl elevation protractors provided, in other words, is there one for each side of the wooden half moon disk just below the sight tube (the instructions only say quantity of 1)?

There is a nice write-up on the Centuri Sky-Trak in the Centuri American Rocketeer Vol. 4, no. 1, pages 10-11 (copy attached here), which gives some very good details for the whole set.

Thank you both for sharing and thanks to anyone else who can chime in to help support this effort!

Kind regards,
Jeff Jenkins
aka: Faithwalker
NAR #46879 SR

Attached Thumbnails

   

Yes, just the one elevation angle protractor as I recall. The sight tube I don?t know for sure the length, as mine is kind of hard to get to right now due to some on-going rearranging work underway inside the home. But, I?m pretty sure the sight tube itself is simply Centuri ST-16 tubing painted flat or semi gloss black.

Overall, it is a fairly straightforward piece of equipment and though not necessarily complicated, would take a bit of effort to replicate if someone really wanted to accomplish that task. But probably one of the more nicely produced pieces of rocketry equipment from back in the day.

Earl

__________________
Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970

Yes one elevation protractor (white plastic)

They don't identify the sight tube in the instructions, but the tube couplers used to make the peep sight and crosshairs are listed as "HTC-175". Looking at the back of the Centuri catalog under "Large Scale" rocket parts the HTC-175 fits the #175 tube. The LT-175 Large-scale body tube is listed as 1.84" OD x 1.75" ID. My sighting tubes are 18" long.

The peep sight is a 1/8" launch lug (guessing 1-1/2" to 2" long??)

The protractor that comes with the altitude computer is printed on cardstock (scan attached).

There are a lot of fiddly bits (leveling springs, etc) that would make this is challenge to clone. That tripod alone would take a lot of effort and money to build!

I am still trying to get the comp sheet to flatten out. I have reverse-rolled it and it is helping but I tried to take some pics of it and could not get a satisfactory result. I will leave it overnight to see if it flattens more, else I will have to tape it down. The plastic arms are flattening out better now also, so I should get close up pics tomorrow or so.

Attached Thumbnails

       

Attached Files

Centuri_SkyTrakProtractor.pdf (29.7 KB, 25 views)

__________________
David Stribling
NAR 18402 SR
But it is rocket science!
Get yer Barrowmans here

I was able to reach (barely!) the top of the box that mine is stored in and was able to get to the sight tube. Yes, it is the heavy walled MiniMax tubing as David mentioned. I was going off memory from several years ago last time I had looked over the parts. Just a bit larger in diameter than the ST-16 tubing I was thinking it might be. Having looked it over again I was thinking booster tubing for the MiniMax Hustler and that would be the 1.75 stuff David mentioned.

Thanks for attempting to photo the computer plot sheet.

Earl

__________________
Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970

Thanks, guys! All that information is very helpful!

Kind regards,
Jeff Jenkins
aka: Faithwalker
NAR #46879 SR

ERockets still carries a supply of the LT-175 tube (although they do list it as discontinued): https://www.erockets.biz/semroc-hea...ntinued-master/ , and they also still sell the HTC-175 (SEM-CPL-175) coupler tubing: https://www.erockets.biz/semroc-tub...ng-sem-cpl-175/ . I went ahead and ordered some of each to be able to construct spares, if needed.

Another question that I have for both David (Rocketguy101) and Earl, some of the previously referenced literature (the Centuri American Rocketeer Vol. 4, no. 1, page 10) for the Centuri Sky-Trak mentions a carrying case, "the two parts separate easily for storage in a compact and lightweight carrying case." Did either one of yours come with a carrying case? If so, are you able to provide a few photos of it please? Thanks!

Kind regards,
Jeff Jenkins
aka: Faithwalker
NAR #46879 SR

Or the old school wood and steel models...

__________________
John Simmons a.k.a. "Lakeroadster"
NAR 113985
My Fleet with Build Data: Lakeroadster's Rocket Shop

I taped the comp board to a piece of foam core, but it still has some bulges that give off reflections when I try to take the photo. I finally resorted to taking an overhead with a ruler, living with the reflections, then setting it vertical for the closeups, so no ruler there.

Attached Thumbnails

                 

__________________
David Stribling
NAR 18402 SR
But it is rocket science!
Get yer Barrowmans here

The comp board is 17" x 22" x 0.010" thick glossy poster board (dang glossy and the light reflections!!"

The orange grid is 1" x 1" with 0.1" subdivisions. The grid area is 10" x 18".

As stated earlier, the protractor is printed on the same cardstock material as the comp board.

Attached Thumbnails

   

__________________
David Stribling
NAR 18402 SR
But it is rocket science!
Get yer Barrowmans here