Hoop fin: attached at both root and tip.

[Dotini]

I'm a cautious guy who wears both belt and suspenders. So why not attach both ends of the fin to the rocket?


The only problem I see now is that the hoop is under tension, and should one join fail, the fin would spring back to a rectangle.

 

[lakeroadster]

Is that different from the tube fin that doesn't have full circumference, like @jgavins and you were discussing here?

 

[Dotini]

Is that different from the tube fin that doesn't have full circumference, like @jgavins and you were discussing here?

View attachment 479520

Very different. His design is sleek. Mine is admittedly rough, plasticly rude, and somewhat barnyard.

 

[Dotini]

Assembling the fins on to the tube is the tricky part. First I do one edge by applying the CA into the angle of the tee, place the fin into contact, hold steadily for 60 seconds, then wait two hours for full cure. Then bend the other edge (now under tension) into CA applied on the adjoining tee, and hold steadily for 60 seconds. Without releasing hold, apply restraining clamps, and wait for two full hours before proceeding.


Tee sections are from Evergreen Scale Models, and budget priced.
0.020" PETG plastic sheet is a Duco product, also modestly priced.

 

[Dotini]

The fins are set and curing. But they are under a deal of tension, and conceivably could part company from the model if the joint(s) failed.

So I am slowly applying a 2nd layer of CA into these six joints.




At some point I will sand off the excess of the tee sections, and even fair in the flat ends.

Edit:
This is what it will eventually look like.

Weight, including motor mount, shock cord, parachute and altimeter is 1.96 oz. So if I don't add too much paint and ballast, it should fly on anything from an A8-3 to a C6-5.

 

[Dotini]

"Hoop Fin", almost ready for launch.

Finish is rough, but good enough to test.


After weeks of traveling, my launch partner Blair has returned, and we have scheduled a session for tomorrow. There are five new rockets for maiden flight and two for their 2nd flight. Probably won't get to them all.


Left to right: Apprentice Bash, "Box Fin", Animist 3 (with new weighted nosecone), Mongoose Bash, "Hoop Fin", another Estes E2X bash (with reversed fin can & altimeter bay), and bone standard Apprentice for reference data.

 

[lakeroadster]

What an impressive fleet you have built @Dotini

I must admit that when I saw this photo I thought... Wankel Engine

 

[bobbyg23]

"Hoop Fin", almost ready for launch.
View attachment 479881
Finish is rough, but good enough to test.
View attachment 479880

After weeks of traveling, my launch partner Blair has returned, and we have scheduled a session for tomorrow. There are five new rockets for maiden flight and two for their 2nd flight. Probably won't get to them all.

View attachment 479882
Left to right: Apprentice Bash, "Box Fin", Animist 3 (with new weighted nosecone), Mongoose Bash, "Hoop Fin", another Estes E2X bash (with reversed fin can & altimeter bay), and bone standard Apprentice for reference data.

I have this weird feeling you like the color yellow.

 

[Dotini]

What an impressive fleet you have built @Dotini

I must admit that when I saw this photo I thought... Wankel Engine

View attachment 479890

Since January 1, when I was Born Again in the miasma of lockdown, I have completed approximately 30 rockets. Two have crumpled up, one was impossible to launch, and all the other have flown successfully - except those noted above. Only a few have been kits. I've been lucky to acquire a launch partner, and the support of a knowledgeable and resourceful forum.

 

[Dotini]

I have this weird feeling you like the color yellow.

Yeah, I have taken to substituting yellow for white.

Here's (almost) everything I have - though some are leftovers from 30 years ago.

 

[neil_w]

Go build that Quinstar! Fun to build and fun to fly. Put a 24mm mount in it and launch on D12s.

Quinstar gets the coveted three thumbs up:

 

[Aeronerd]

"Hoop Fin", almost ready for launch.
View attachment 479881
Finish is rough, but good enough to test.
View attachment 479880

After weeks of traveling, my launch partner Blair has returned, and we have scheduled a session for tomorrow. There are five new rockets for maiden flight and two for their 2nd flight. Probably won't get to them all.

View attachment 479882
Left to right: Apprentice Bash, "Box Fin", Animist 3 (with new weighted nosecone), Mongoose Bash, "Hoop Fin", another Estes E2X bash (with reversed fin can & altimeter bay), and bone standard Apprentice for reference data.

Very original and impressive collection!

 

[BABAR]

Yellow is a good color for visibility of rocket on ground for recovery, not as good as fluorescent pink but a bit more conservative.

 

[Dotini]

"Hoop Fin", almost ready for launch.
View attachment 479881
Finish is rough, but good enough to test.
View attachment 479880

After weeks of traveling, my launch partner Blair has returned, and we have scheduled a session for tomorrow. There are five new rockets for maiden flight and two for their 2nd flight. Probably won't get to them all.

View attachment 479882
Left to right: Apprentice Bash, "Box Fin", Animist 3 (with new weighted nosecone), Mongoose Bash, "Hoop Fin", another Estes E2X bash (with reversed fin can & altimeter bay), and bone standard Apprentice for reference data.

I'm very pleased to report successful flights today on all of these rockets. No damage and no real trouble of any kind! Each rocket returned the full range of ALT2 data which will be useful in refining the motors, parachutes, ballast and design directions going forward. With special regard to the HoopFin, which flew on an A8-3, we could easily ascertain it could do with more length and more power. And I really don't like that pointy nosecone on it or the Animist 3.

 

[lakeroadster]

Was the 12:1 length/diameter BT-60 rocket stable, as previously discussed here?

 

[Dotini]

Was the 12:1 length/diameter BT-60 rocket stable, as previously discussed here?

Yes. The 12:1 BT-60 rocket I call Apprentice Bash was very stable. Wind was variable up to 8 mph. Launch rod was tilted ever so slightly into the wind. As a precaution, I had 0.30 oz of plumbers putty in the nosecone along with the altimeter. A C5-3 took it up smartly and it leaned slightly more into the wind. Altitude was 316' and descent took 24.6 seconds. If I launch this again, I might be tempted to remove ballast or even the ring itself. I never would have imagined those 3 little Apprentice fins would be so effective.

 

[jqavins]

Is that different from the tube fin that doesn't have full circumference, like @jgavins and you were discussing here?
View attachment 479520

Very different. His design is sleek. Mine is admittedly rough, plasticly rude, and somewhat barnyard.

Starting with flat sheets of PETG has given @Dotini fins that are, well, it's hard to say what shape they are. My concept was to have them be circular arcs, which Dotini's certainly are not. That's the main difference.

Correction: the main difference is that he's actually built his, while I've sat on my backside watching TV and reading/posting on the forum. A rocket that exists is worth more than ten conceptual sketches any day of the week.

 

[lakeroadster]

Starting with flat sheets of PETG has given @Dotini fins that are, well, it's hard to say what shape they are......

HETF: Half Elliptical Tube Fins... that's what they look like to me.

 

[Funkworks]

Has anyone tried this with balsa? I had a a good time pushing the limits of curving balsa with hot water and/or ammonia. With < 1/8th inch thickness, I'm pretty sure one could do these half tube fins.

 

[Dotini]

Two further flights today finalized my development of the "HoopFin", my elliptical variation on the tube fin theme.
A modified BT-56 nose cone was introduced, carrying the altimeter and 0.50 oz of plumbers putty, extending overall length slightly and bringing total weight to about 3.4 oz. A flight on B4-2 yielded 178', and B6-2 attained 196'. No further flights of this model are planned.



"HoopFin"

 

[lakeroadster]

Two further flights today finalized my development of the "HoopFin", my elliptical variation on the tube fin theme.
A modified BT-56 nose cone was introduced, carrying the altimeter and 0.50 oz of plumbers putty, extending overall length slightly and bringing total weight to about 3.4 oz. A flight on B4-2 yielded 178', and B6-2 attained 196'. No further flights of this model are planned.

View attachment 480846

"HoopFin"

That's one awesome bird @Dotini