Is there or has there been an over-the-body tube BT-50 plastic fin can?

[Tramper Al]

Analogous to the 1340 fin can, have there been any BT-50 models with a plastic fin can that went all the way over the body tube? Such that it was the body tube itself that sat at the bottom of the can - and thus allowed a 24mm engine to be fitted. For BT-50 plastic fin units, I'm really only familiar with the Challenger-1 type, the Centuri Screaming Eagle type, and then the modern E2X/RTF type that often has a plastic screw on retainer. I believe with all of these the I.D. of the can itself it quite a bit smaller than the body tube - which is adhered to the top rather than passing through the way it does with a 1340-type can. I'd like to construct a sort of Challenger III plastic-finned minimum diameter to carry the current Astrocam nosecone, but I haven't found a fin can that actually goes outside the tube.. Thanks.

 

[Ez2cDave]

I don't recall any "external" plastic BT-50 fin cans ( I've been in Model Rocketry, since 1967 ) . . .

This sounds like a project for a 3D printer, with which, I have zero experience.

Dave F.

 

[Back_at_it]

I'm racking my brain here and I cannot think of a single rocket that has a BT50 sized over the tube fin can. I think they were all BT56.

 

[Tramper Al]

Thanks for thinking about it.

Coming at this from another (Estes) angle, consider this old (1973) blurb about small commercial sounding rockets, mainly focused on the Enerjet 1340, but also on a mysterious Estes model 950. That rocket was said to be 0.95" in diameter, have a plastic fin can, and be powered by a D-12-5 engine. In the attached page, see the left hand column with Figure 7. I'm sorry I can't recall the exact reference, but it is a March 1973 model rocket periodical of some kind.

 

[Tramper Al]

And one step further, I am looking at the Quest model Viper. It has a 4 fin plastic fin can unit with integrated launch lug that is installed OVER its body tube. The tube (per model specs and Ninfinger Quest tube stats) has an O.D. of 0.984" and I.D. of 0.944", which I think will be in a range to both fit pretty well over a BT-50 (O.D. 0.976") and allow a 24mm engine, via friction fit at least. Now, the Quests fins aren't nearly as beefy as even the late Estes (Eliminator) 1340 fins, of course. Strangely, Googling Quest Viper and BT-50 yields me nothing relevant.

https://aerotech-rocketry.com/products/25mm-plastic-fin-unit-q21551

https://www.erockets.biz/quest-flyi...-bulk-pack-kit-no-fancy-packaging-qst-1008bk/

 

[jmasterj]

I don't know of any either, but they're pretty simple to 3D print.

 

[Tramper Al]

I don't know of any either, but they're pretty simple to 3D print.

Yes, I've got to learn how to do that. Just take an existing 1340 file and scale it perfectly to the BT-50. I do, though, like to use existing model parts whenever feasible.

 

[Ez2cDave]

Thanks for thinking about it.

Coming at this from another (Estes) angle, consider this old (1973) blurb about small commercial sounding rockets, mainly focused on the Enerjet 1340, but also on a mysterious Estes model 950. That rocket was said to be 0.95" in diameter, have a plastic fin can, and be powered by a D-12-5 engine. In the attached page, see the left hand column with Figure 7. I'm sorry I can't recall the exact reference, but it is a March 1973 model rocket periodical of some kind.

That article is from the MARCH 1974 Model Rocketeer magazine . . . Images below.

Apparently, there was an "ESTES 950 Sounding Rocket" ?

FORTUNATELY, the article was written by JOHN LANGFORD, current Owner of ESTES ! ( Getting more info should be pretty easy )

Dave F.




Dave F.

 

[PDawg]

The Quest Viper. I have a BT-50 min diameter scratch build that uses the Viper plastic fin can. Fits perfectly and mine is 20 inches tall and uses an E-12-6. I have flown this twice, and was awesome.

 

[JPalmer621]

This my BT 70 scratch fin set for my Gemini Titan. Slides over the body tube It fits the one on the left.

 

[Ez2cDave]

I emailed John Langford and he replied back to me.

The "950" used an MPC fin unit ( likely the one that is still used on the Quest VIPER ).

Detail on Fin Unit starts at 13:20 mark in this video.



Dave F.

 

[SolarYellow]

If you can 3D print, you might look for Jack Hydrazine's variations on the Generic E2X fin can. I think he did one with an actual airfoil. Just scale it up slightly so the OD of the can is big enough, then hog out the middle with a big through-hole. I think the "dig hole" function in Chitubox would probably work for that if you can get it precisely centered.

 

[OzHybrid]

Does this help? 2mm thick fins 1mm fincan wall. You'll need to add a tube for a rod guide. 3 fins or 4

 

[Buzzard]

Ref: Post #8

I have known John Langford for a number of years starting as NAR competitors. My first wife and I were married in October of 1972 after I graduated from Air Force tech school as a AGM-28B Hound Dog missile technician. Bonnie and I were headed to FL for our honeymoon and stopped overnight in Atlanta. The next day we had lunch with John, his sister, and their mother (Judge Langford was at work). John mentioned that he was looking for a Science Fair project and I mentioned G. Harry Stine's articles in Analog. Harry had suggested that a model rocket could carry a thermister and transmitter to measure temperature change as the model penetrated a smog layer. Harry had a series of articles in Analog talking about using model rockets and electronics. The articles I apparently had seen predated the mentioned November 1972 reference. I am not saying that I am responsible for John's research, but I do believe that I nudged him in that direction. Sadly the issues of Analog that I had were not kept through various military moves.
For those of you who do not know John Langford's history, he has a PhD from MIT and Dr. Langford started Aurora Aerospace. He hosted the reunion of NAR members at Aurora for NARAM 50 participants. He later sold Aurora to Boeing, started an electric aviation startup, and - oh - purchased Estes Industries.
If you ever meet John, shake his hand. A truly smart individual, intuative engineer, and dedicated model rocketeer.

Chas