Adding fins to rocket tail...

evan_ross

I'm building the tail section for a model rocket.  It's basically a cone (small side down, big side up) with fins attached.
The problem is the fins.  I make a sketch and then do a symmetric extrusion.
The edges of the extrusion don't touch the cone.
Is there a way to make that happen?

Jake_Rosenfeld

Hi Evan,

Can you post the URL of your document here? It'll be easier to help that way.

evan_ross

https://cad.onshape.com/documents/c65007e1a62931dc2b0783f0/w/405e8efe19e6f5cefda176f1/e/2c56bf5d454bec31c45c51d2
I modified it slightly as an experiment trying to embed the edge of the fin into the cone.

jakeramsley

If you are making the side profile like that, I would use a replace face to make sure the two parts meet properly.  I modified the sketch a bit to make the gap easier to see.

1. Start a replace face and select the end cap of the face that you want to touch to be the "Face to replace".


2. Select the outer face of the rocket to be the "Surface to replace with".  This will try to rip off the face you are replacing and replace it with another one that fits the same surface as the rocket.  It will then extend other edges/faces of the part in order to make a valid part.  As the face of the rocket is cyclical, there are two potential solutions it could find.  If you are finding the fin going all the way through, click "Flip alignment" to get the other solution.

larry_hawes

That's great tip feature I did not know existed.

evan_ross

Hmm, it's not quite working for me (probably pilot error / lack of experience).
Once the fins are joined to the cone, I want to have a concave fillet to blend the side of the fin into the surface of the cone.

lana

@evan_ross
Use Boolean feature to merge fins to the cone then Fillet the resulting edges

evan_ross

Woohoo!!!   The toughest part was finding a way to select the face of the fin to be replaced.  Had to zoom in all the way and find the tiny gap between the fin and the cone's surface.
It would probably be easier if i'd switched to x-ray view.
Now I know for next time.

owen_sparks

evan_ross said:

Woohoo!!!   The toughest part was finding a way to select the face of the fin to be replaced.  Had to zoom in all the way and find the tiny gap between the fin and the cone's surface.
It would probably be easier if i'd switched to x-ray view.
Now I know for next time.

The "hide part" option (either from right click menu or keyboard shortcut "y") is your friend here.

Owen S.