Is This Shape Possible?

[Anonymous]

Hello all,

At my school, we are doing a bottle rocket competition. I am hoping to be able to 3-D print my nose cone. My idea is to have the nose cone have spirals coming down it. My idea is that then the air will flow through them and make the bottle rocket spin so it will stay at a straighter path. Does anyone have any suggestions on how to do this? I used the revolve tool but can't figure out how to then manipulate the object for the curves. Any suggestions would be greatly appreciated. 

Thanks 

[mavigogun · Accepted solution]

You're part way there with the Revolve.    Revolve cone > Offset Plane above cone > Sketch on Plane > Project cone circumference and center point to Sketch > draw 2D Spline curve from center point to circumference >   Create Sketch anywhere > Project to Surface Spline curve >   Sketch on cone base > draw fin Profile intersecting Spline curve > Loft from fin Profile to cone point with Spline curve as Center Rail > Circular Pattern to taste.

As with all things Fusion, there are other routs to this destination; some might use Coil to create the spiral path- the above method was easier for me.    Alternative to the Profile, Patch Lofting from the cone center Line to the Spiral would be another way to create a base for a fin.   Questions?  Feel free.

[Anonymous]

Thanks for the quick reply. I've found there's a lot more to fusion 360 than I thought. So I'm slowly getting through the steps. What do you mean by project to surface spline curve?

Thanks

[Anonymous]

Is there any way I could get that Stl.?

[mavigogun]

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@Anonymous wrote:

 What do you mean by project to surface spline curve?

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Create Sketch > Project/Include > Project to Surface > Select the cone for the Surface and the Spline(curved line) you created on the Sketch above the cone; the result will be a 3d Projection onto the surface of the cone.   Think of it as shining a light from behind a Sketch element, casting a shadow onto a wall/shape.   Super useful tool.

Unfortunately, I didn't retain the file.

[mroek]

One thing to note is that you need to change the projection type to "Along Vector" for this to work. By default it starts with "Closest Point" (at least for me), and that doesn't get you the result you want.

[Anonymous]

Niw that you have the answer to CAD methods...

Rockets dont need to spin because of the presence of fins...can you not add fins to your rocket?

Spinning a rocket with fins will just make it less efficient and less stable. 

[Anonymous]

Yeah, so we have our fins on our rocket but it'll still spin and therefore slowing the rocket down. So we can curve the fins and it then flys straight. Like passing a rugby ball. If you spin it'll go straighter and further. So now we're trying to use the nose cone to spin the rocket so it might be more effective as more air hits it. But any suggestions are more than welcome, a bit of Australian competitiveness here!

[Anonymous]

A rugby ball doesnt get the advantage of fins so it has to rely on the rotation of the ball.

With small rockets, the fins are intended to keep the center of pressure below the center of gravity to keep the trajectory relatively straight. You can push this too far and get weather cocking, but that's easy to correct.

If you are spinning, something is not straight, and spinning is going to hurt your total distance. It is only a detriment to a properly designed finned model rocket.

It would be more advantageous to determine why the rocket is rotating during flight because it's likely something isnt true or your center of pressure is too far forward. It's often as simple as straightening fins or adding weight to the nose cone.

Here are some resources.

https://spaceflightsystems.grc.nasa.gov/education/rocket/rktstab.html