Centuri Groove Tube Question

[lowga]

Flying Saturday at our club launch, and I sent my Centuri Groove Tube (built circa 1975) up for it's 60-ish flight. This time on a Quest A3-6 composite motor. We had a good wind, and a lot of rockets were weather-cocking. It got off the bad well, but almost immediately pitched hard into the wind. The delay was much too long, The rocket arched over and plunged towards the nearby hilltop.

Just before impact the delay finally fired, but the ejection came too late for the streamer to deploy. Thanks to our eagle-eyed club President, I managed to recover this treasured gem with minimal damage. But the nose cone had split into it's too parts. The base was still attached to the shock cord was still there, but the top half of the nose cone was gone.

Anyone know what the exact replacement is and where I might obtain one?

 

[Mightymango]

I believe this will be the correct size or so. I know the original is 4.6 inches long.

https://www.erockets.biz/semroc-balsa-nose-cone-8-4-6-rounded-ogive-sem-bc-846/
https://billsrockets.blogspot.com/2017/09/a-tubular-build.html
The hyperlink says QUEST but it is not, it is about the Centuri one.

 

[lowga]

That's great--but the original nose cone is plastic. Is that available?

Love the build thread too. I'm a big fan of tube fin rockets--but they're all children of the original mother--the Centuri Groove Tube!

 

[Mightymango]

No one is going to make a split cone like the original. You could use a smaller Estes PNC-50YR which is quite a bit shorter, you could 3d print the correct Centuri PNC-89 sized plastic one if you or someone you know has the means. https://www.thingiverse.com/thing:576222

If it was me...I would just get the balsa cone which will probably perform better anyway.

 

[lowga]

The parts list for the Centuri Groove Tube is:

• 1 PNC-89 Nose cone (Semroc/eRockets BC-846)
• 1 Shock Cord
• 1 Body Tube ST-813
• 6 Stabilizing Tubes ST-83
• 1 Thrust Ring TR-7
• 1 Centering Ring HTC-8
• 1 Motor Tube ST-73
• 1 Motor Hook

Does anyone offer ST-813 body tubes and ST-83 tubes? Can't seem to find them. Obviously, I have zero experience in cloning vintage kits.

 

[Mightymango]

https://www.erockets.biz/semroc-body-tube-8-13-0-long/ should be the body tube

https://www.erockets.biz/semroc-body-tube-8-3-0-long/ should be the Stabilizing tubes.

 

[K'Tesh]

https://www.rocketryforum.com/threads/looking-for-info-on-the-centuri-pnc-89-nosecone.142171/
Still waking up, IINM it's the same thing as the Estes PNC-50YR nosecone. But remember, I'm still climbing out of the fog of sleep.

 

[lowga]

Ha, Ha. Thank you. BTW, I dug out my Estes Honest John 1919 kit--remembered that you needed something from the instructions or the decals? Let me know what you need and I'll be happy to scan it and get it to you.

 

[K'Tesh]

Ha, Ha. Thank you. BTW, I dug out my Estes Honest John 1919 kit--remembered that you needed something from the instructions or the decals? Let me know what you need and I'll be happy to scan it and get it to you.

I'd be happy to take anything you can send me. The decals are the major hold up on that kit's sim though.

 

[lowga]

local friend who is really into 3-D printing was kind enough to print five PNC-89 Nose cone replacements for me. Received those today and did a quick dry fit. Everything seems great.

Once all the rain from Hurricane Laura stops in a few days, and things dry out, I will wet sand the parts. Paint to follow and we'll see how close to the original I can get. Have two other Centuri Groove tube originals here, so good stuff to compare it to. It's a little heavier than the original, but i doubt it will affect stability much. I'll weigh it and adjust the sim file, also do a 'swing test' prior to launching it again.

Very happy!

 

[GlenP]

Those can also be fun with a Centuri Booster 8 ...

https://plans.rocketshoppe.com/centuri/cenKBB-8/cenKBB-8.htm
https://www.erockets.biz/semroc-laser-cut-fins-8-booster-3-fins-fiber-sem-fm-3/

 

[lowga]

I'm a huge Centuri fan--check out the sticker on the Creature From the Rocket Lagoon's ride <-- <---

But I've literally never seen or heard of the #8 booster before, nor knew that Centuri recommended a booster for the Groove Tube. That's awesome. Now i have build one.

It also gives me an idea to build a tube fin booster and see that might look and fly. Anyone tired one?

Thank you sir!

 

[GlenP]

The Booster 8 was bundled with the Excalibur 2, but was also available separately. The booster coupler only fits if you have the engine mount centering ring about an inch or so recessed into the body tube, per the original instructions. Those kits originally had one single wide centering ring for the engine mount in the middle, rather than two narrow rings at each end.

For a tube fin booster, you might need those tubes to be a little larger dia than the sustainer, it might work.

 

[Mightymango]

I need a friend with a 3d printer or figure out how/what to get myself as those turned out REALLY well.

 

[kuririn]

It also gives me an idea to build a tube fin booster and see that might look and fly. Anyone tired one?

Discount Rocketry has a booster with tube fins called the "Boostoh".
Pictured is the Boostoh/Super Tooboh combo.
And Squirrel Works has a finned booster with tube finned sustainer called the Tuber.

 

[dhbarr]

The great thing about a tube-finned booster is you can mount the fins so that the CG and CP are 1:1 -- guaranteed to tumble on recovery.