Hi Mark;

The BT-30K length provided in the Body Tube Reference was taken directly from the 1974 Custom Parts Catalog; unfortunately I wasn't able to directly measure a sample of BT-30K, as I don't happen to have the Sprite in my kit collection. I also notice that Semroc has used the 1974 Parts Catalog length for their part.

You raise a valid point based on the information provided in the kit instructions, however if one were to rely on the listed overall length of the model then 2.75" would be too long (although this by itself is not a reliable data point as Estes was notorious for "approximating" kit lengths in their catalogs). But in thinking about it, and knowing of other errors in the 1974 Parts Catalog, it wouldn't be surprising to find yet another error. Perhaps when someone was transcribing 2-3/4" into a decimal entry it came out 2.34". Maybe someone with an actual K-15 Sprite kit can confirm the length of BT-30K. I'll be happy to correct the Reference List if the listing is in error.

Thanks for raising this one!

NOt sure if this was resolved, but finally remembered to grab my vintage built-up Sprite (purchased built, so I have to guess it;s correct, although did not open it up myself ).

Tube length on mine is 2 3/4"

Hope that helps - going to be building up another one with mini engine mount and streamer recovery, so I can fly it ( since I have an original BT70 tail riong in the parts box, found it the other day while foraging, lol ) ..

will post pics once stuff starts looking somewhat like rockets, lol .

~ AL

I have a Sprite that I built in 1967 and when I measured the body tube, it's 2.75"

A few years back I bought a whole bunch of "ST-30" tubing, plus lots of cones from BMS, in order to put together Skyhooks, Marks, Sprites and Spaceplanes.

I marked the tubes after they arrived. The '2.34"' figure shown on the Ninfinger BT chart caused me endless confusion. Why such a strange amount? Somewhere along the way I found a reference to the tube's true length.

Hi Stefan;

The feedback that the guys have provided regarding their measured tubes is helpful, as it confirms the point. As Mark conjectured, it would appear that the BT-30K was 2.75" long, and was distinguished from the BT-30J by the fact that it had the factory-punched exhaust hole.

As I indicated in my earlier post, my best guess as to the incorrect length dimension in the 1974 Custom Parts Catalog is most likely due to someone transcribing the 2-3/4" length into a 2.34" decimal entry. Close scrutiny of the Parts Catalog will show other errors in other areas, so not so surprising.

I want to thank everyone for making the effort to measure an actual BT-30K; I don't have a Sprite in my collection, so I had to rely on the Parts Catalog as the source for the Tube Reference. This feedback allows me to update the Sprite entry in the Tube Reference, which will happen with the next release.

Thanks;

Speaking of the pre-punched hole for the Sprite - I have a somewhat modified hole punch that is just right for punching that hole. Several years ago I looked high and low for one that had enough reach to make the required depth on the tube, and finally found one. I can't tell you where I finally stole (er, found) one, but it works and I'd be glad to loan it out to someone making a clone.

If I'm ever able to make it to a meeting that you're at, I'll bring my tube so we can get it punched. Thanks.

Kurt,

Can you post a photo so I'll (we'll) know it when we see it? Thanks.

Sean

OK, here you go. It is >just< long enough to punch the hole in the correct location on the tube. The punch is made by the McGill Company, Marengo, IL. No model number or anything.

It originally had a moveable depth gage that I removed (easy to remove) so you could get full depth off the punch. Otherwise it would not reach.

I also drew up a punching guide for the tube, I'll have to search around for that. It made punching the tube easy.

Here is the marking guide. It has been a few years since I drew this thing and I kind of forgot how you use it. Somehow the black circle ends up where the hole should be, and the long rectangle is where the hook goes. You tape the guide on the tube and then punch through it to make the hole. Remove the guide before gluing the fins on of course.