Parallax Terror: Tubes galore!

Parachute size is not your only concern. A 30" parachute will slow your rocket's vertical descent rate but won't do anything to its ground speed if the air speed is high due to a significant wind. If you're concerned about the fins being snapped off due to an angular impact, only fly the rocket in calm conditions.

(I had a similar problem with my Feuerlilie F55https://www.macs.hw.ac.uk/~adrian/rockets/f55.jpg, whose wingtip fins like to snap off given any provocation. I gave it a 75cm parachute and it still lost a fin when, due to a significant wind, it hit the ground at a fair horizontal speed.)

adrian said:

Parachute size is not your only concern. A 30" parachute will slow your rocket's vertical descent rate but won't do anything to its ground speed if the air speed is high due to a significant wind. If you're concerned about the fins being snapped off due to an angular impact, only fly the rocket in calm conditions.

(I had a similar problem with my Feuerlilie F55https://www.macs.hw.ac.uk/~adrian/rockets/f55.jpg, whose wingtip fins like to snap off given any provocation. I gave it a 75cm parachute and it still lost a fin when, due to a significant wind, it hit the ground at a fair horizontal speed.)

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To be honest, I don't think that tube fins this small will have any issue on landing.On larger sizes, perhaps, but not 38mm, and not with Blue Tube.

It isn't actually all glued. The last two are just there to provide support.

CarVac said:

To be honest, I don't think that tube fins this small will have any issue on landing.On larger sizes, perhaps, but not 38mm, and not with Blue Tube.

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Looks like your tube fin plane is positioned a few cm forward of the rear end of your body tube. I am presuming the engine will stick out a cm or more beyond that. If this beauty comes down vertically, seems like the butt of the engine should take the brunt of the impact when it lands, which would spare some stress of the fins.

I am wondering whether this design will ALSO be less prone to weathercocking. From a side profile the surface area of the fins is much less than the "true" effective surface area relative to the airstream. Not sure if I am right, but guessing superstable WITHOUT the downside of weathercocking. Going to have a good bit of drag, but the build is for looks/cool factor, not performance.

CarVac, I thought you were still here on the Left Coast and didn't realize you were new in New Jersey.

Flying on grassy fields should help a lot.

Positioning the outside tube fins forward of the inside ones is a great idea. Many of the larger tube fin rockets use fins that are cut at an angle on the bottom for the same reason. I've not tried it because my tubers are generally under 4" in diameter.

Keep us posted on how this project goes.

o1d_dude said:

CarVac, I thought you were still here on the Left Coast and didn't realize you were new in New Jersey.

Flying on grassy fields should help a lot.

Positioning the outside tube fins forward of the inside ones is a great idea. Many of the larger tube fin rockets use fins that are cut at an angle on the bottom for the same reason. I've not tried it because my tubers are generally under 4" in diameter.

Keep us posted on how this project goes.

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I tested it and the amount of forward offset needed to prevent the outer ones from contacting first is too much, so I will just keep them in line for the best bond length. That seems like it will be more important than what strikes first.

Carvac that looks wild . I like how you have a open space 90°apart . Make it eazy for rail buttons . With square cut tube fins it always go to have them 1/2" or more from the bottom . Did you hand cut all of them ? I will have to figure out how I'm cutting tube fins for my next project .
10" sono tube maybe a fin blade on a table saw .

I used a hand miter saw frame which obviously doesn't work for tubes larger than 4 inches.

CarVac said:

I used a hand miter saw frame which obviously doesn't work for tubes larger than 4 inches.

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You just need a larger miter saw frame

Area66 said:

You just need a larger miter saw frame

View attachment 182885

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That's not a miter saw frame though.

CarVac said:

That's not a miter saw frame though.

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Gerard is Canadian. Probably a lumberjack, too. LOL!

Must... resist... Monty Python joke...

chris m said:

Yes I'm thinking a 8-12" tube fin for my L3 should be cool

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That's what my level two rocket is. Eight tubes. Four inch diameter. 56 inches long on a J240w DMS.

Andrew

accooper said:

That's what my level two rocket is. Eight tubes. Four inch diameter. 56 inches long on a J240w DMS.

Andrew

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So how did it do . All of my tube fin rockets have been 6 . Would like to find information on the number of fin (tube at scale of 1-1.5 times caliber) vs aerodynamics . And what will be the most stable. I have seen one rocket with two half fins . Would like to build a three tube fin see what it does . Sorry to hijack your thread . But tube fins are getting popular due to ari . With his L3 and both blue tube fin rockets .

Peak of flight #334 has a lot of good ideas

How is this tube fin going ?

chris m said:

How is this tube fin going ?

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The last tubes are on but I need to get more tubing for an avionics bay so that I don't have to guess at the correct delay. I also need rail guides and paint.

Cool tube fin rockets are getting very popular now . Think there cool and there a crowd pleaser . Getting the tubes soon for my 10"

Carvac any update ? I am working on a 36" tube fin that's 4" with three fins .5" off the bottom . May add another set of three between them that's .5" below the first sets lip so it would be staggered . Just think right now

chris m said:

Carvac that looks wild . I like how you have a open space 90°apart . Make it eazy for rail buttons . With square cut tube fins it always go to have them 1/2" or more from the bottom . Did you hand cut all of them ? I will have to figure out how I'm cutting tube fins for my next project .
10" sono tube maybe a fin blade on a table saw .

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I built a roller assembly to hold my 10" Sonotube to cut a 2" piece off for a ring fin OUTSIDE my skinny elliptical fins which kept insisting on breaking off. One flight so far worked OK, the ring took a beating but no broken elliptical fins :wink: Not thinking very far ahead, I built it too high the first time, the blade couldn't reach the Sonotube, had to redesign it a bit.