Ok, lets concentrate on the tip now. This is all that is left after all.
Using ExtractSrf extract the lower surface:
Now, using DupBorder, create a circle out of this surface. Then we need to play with CPanel a bit.
Click on the Perspective caption in the viewport with right mouse button and select under Set CPanel->To Object.
This is how your CPanel should be positioned now:
Ok, now Offsetting the circle we recently created will work from Perspective viewport. So, select the circle, and Offset it by 1 units inwards.
Now, with the part of that red curve we have on the image above, we will create Sweep1 surface from the edge of this yellow surface. It would be great to first shorten the red line a bit. We will do that by creating a Point on it using OSnap option Near.
Split this red line with the Point. Now, using the lower surface edge and this bigger part of split line we will make a surface with Sweep1 command:
Ok, still in the perspective viewport because we have CPanel set the way we want it in that viewport. So, using Offset command offset this line left and right by 0.1 units:
Now, create a Circle from the center of this tube. We have the line in the center, so just point your cursor over the end of that line and input 1 unit as radius:
Using that circle, we will Split those two lines and delete the short parts:
Then, using BlendCrv command, blend the two lines:
Now, Join the blend curve,and two lines. After joining them, using CloseCrv command close the set of curves into one closed curve:
Now, we need to move that closed curve along the center line. Just move it a bit, like on the image below:
Using ExtrudeCrv extrude that rib (use the Cap option and set it to Yes):
And for the end, use ArrayPolar command and array those ribs in total of 14 times around 360 degree:
Ok, and in the end you should have something like this: