Hole in Estes Alpha Fins

[coopwyo]

My class is building the Estes Alpha for our rocketry unit. I bought the bulk pack of rockets and the fins contained in each kit have a hole laser cut in them along the root edge of the fin (see picture). Does anyone know what this hole may be for? It is not referenced in the instruction sheet and does not show up in the completed rocket pictures. Thanks for the help!

 

[Scott_650]

The holes identify the root edge of the fins - it's to help a beginner attach the fins correctly.

 

[neil_w]

The holes identify the root edge of the fins - it's to help a beginner attach the fins correctly.

If it doesn't say it in the instructions then I'm not sure how much help it would be...

 

[SolarYellow]

If it doesn't say it in the instructions then I'm not sure how much help it would be...

Yeah, that surprised me when I checked. I knew what the hole was for, but only because I know how to orient the fins.

ETA: I emailed Estes CS with a link to this thread and some comments.

 

[kuririn]

Termites.

https://www.rocketryforum.com/threads/estes-alpha-laser-cut-fins.169168/

 

[BEC]

That laser-cut hole is indeed there to indicate the root edge of the fins. The die cut Alpha fins (from the mid 1970s to the early 2000s) have a dimple rather than a hole at the same place. Some versions of the Alpha instructions mention this dimple and its purpose.

That note had gone away before the fins were converted to laser-cut-in-China (with a slightly different shape) some time around 2004 — so the laser-cut hole's purpose has never actually been shown in the instructions.

They could save a bit of production cost by not cutting those holes, or they could put the note back on the instructions that say what it's for. But they've done neither in decades.

Here's the first appearance of the marker in Alpha instructions, circa 1979. Last sentence here.



I've seen Alphas with the fins mounted by the trailing edge (which makes it look like a Centuri Astro-1 or its Semroc relatives the Astro Jr. and Astron) and my grandson actually built an Alpha with the leading edge on the body. That one wasn't stable on a C.

 

[GlenP]

My first rocket was a Centuri Viking, it has fiber board fins. Unlike the balsa where grain direction is important to avoid a fin cracking along a grain line on a hard landing, the fiber board laminated fins on the Viking have no reference dot. And apparently the model has sufficient stability margin for 3, 4, or 5 fins, glued on any edge!

 

[lakeroadster]

My first rocket was a Centuri Viking, it has fiber board fins. Unlike the balsa where grain direction is important to avoid a fin cracking along a grain line on a hard landing, the fiber board laminated fins on the Viking have no reference dot. And apparently the model has sufficient stability margin for 3, 4, or 5 fins, glued on any edge!

View attachment 608162

Classic stretched body tube.... makes for a "forgiving" build.​

 

[SolarYellow]

I bought a Viking bulk pack. The die-squishing on the fin sets made every fin dished like a spoon. I suppose they could be glued on at an angle to work like propeller blades and make it spin if one wanted to. Fortunately, I didn't get the pack with the intent of ever building a Viking.

 

[brockrwood]

My class is building the Estes Alpha for our rocketry unit. I bought the bulk pack of rockets and the fins contained in each kit have a hole laser cut in them along the root edge of the fin (see picture). Does anyone know what this hole may be for? It is not referenced in the instruction sheet and does not show up in the completed rocket pictures. Thanks for the help!

How about using the hole, and a piece of thin kevlar string, to make the rocket land on the top of the tube, rather than on the fins, which are heavily swept back and can break off?

 

[MALBAR 70]

What ever you do, don't fight them, that's bat-tery.

 

[GlenP]

follow-up:

I built my Viking something like this one, with three fins attached on the long edge, with LE shorter than TE, since I thought it would be lighter, less air resistance and would go higher, that was some clever engineering for a Cub Scout, right? I did not get the fins on straight and was embarrassed at how crooked one of them was. I just could not get the glue to grab, the fins kept falling off and I had to put them back on, I got sticky glue finger prints all over. But when it came time to launch it, the crooked fins made it spin and wobble, almost like a corkscrew type rocket that made a pulsating tremolo sound as it went up and left behind a helix smoke trail that everyone thought was really cool and asked me: "how did you do that?"

That's my origin story!

 

[BABAR]

follow-up:

I built my Viking something like this one, with three fins attached on the long edge, with LE shorter than TE, since I thought it would be lighter, less air resistance and would go higher, that was some clever engineering for a Cub Scout, right? I did not get the fins on straight and was embarrassed at how crooked one of them was. I just could not get the glue to grab, the fins kept falling off and I had to put them back on, I got sticky glue finger prints all over. But when it came time to launch it, the crooked fins made it spin and wobble, almost like a corkscrew type rocket that made a pulsating tremolo sound as it went up and left behind a helix smoke trail that everyone thought was really cool and asked me: "how did you do that?"

That's my origin story!

View attachment 608654

I prefer to think of corkscrewing as a safe flight entertainment feature, rather than a defect. For a sport rocket where you aren’t out for competition or even flying an altimeter, I find the rocket launch profiles are at least as cool and often IMHO cooler than the arrow straight standard rockets.

https://www.rocketryforum.com/threa...ns-spaced-at-120-degrees.121768/#post-1406937