Lofting a pontoon structure - Difficult to get a nice finish

Rhino Rhino for Windows
1

I am dealing with a pontoon for a Zero warbird (Nakajima A6M2) that I am having a little problem with. The problem lies in the aft part of the pontoon. I am not modelling the rudder fin of the pontoon, but just need a simple finish. Due to the shape of the pontoon, I have split it in a fore and an aft part. I am pretty happy with the fore part, but I cannot get the rounded look I looking for in the aft part.

image.png735×122 133 KB

image.png1154×174 11.3 KB

As for now I have lofted most of the aft part but the rounded ending gives me a little headache. From above, the curve show the shape I looking for:

In perspective:

image.png440×773 33.8 KB

So the final part should have a shape like this (minus the rudder):

image.png661×581 202 KB

I have tried to copy and scale another sections to the loft, but the result does not look good.

Any suggestions are welcome.

Zero Rufe - Pontoons V2 2017-05-21.3dm (769.1 KB)

2

Hi Xvis - It looks to me like the top edge is not level until the back - it slopes up to the rear; the lower edge of the rear part appears to be a straight line. I can’t tell for sure but I think the upper surfaces of the whole thing can be made as a single simple surface and trimmed with the intersection of the lower surfaces.

-Pascal

3

Thanks for the reply! Yes, I agree that the top part could be made of one surface, and I might just do that. My biggest issue was how to close the end of the pontoon (see encircled below) to get a nice rounded finish. I have marked the shape it should get.

image.png404×647 37.7 KB

Any suggestions on how to close this to the shape I am looking for?

4

Hi xVvs - it might be something like the attached - but the bottom detail is obviously incorrect, this is a general layout of how you might go about making that part

Zero Rufe - Pontoons V2 2017-05-21_PG.3dm (1.0 MB)

-Pascal

5

Thanks! That was the shape I was looking for!

I will try to extend the ‘flat’ bottom of the pontoon and trim the odd part from the bottom. How was this shape created?

image.png395×660 19.2 KB

6

Hi xvis - see the linked screen capture (no sound).

  1. 3 clean mathing degree 5 curves
  2. EdgeSrf
  3. Surface matching as shown - sorry about the non-existent command line, I hope you can see what I did there.
  4. A little point adjustment with DragMode set to ControlPolylgon.

-Pascal

7

Looking through the steps needed to get this result, I doubt I would get anything near this. Again, many thanks!

Edit: Added image of the finished part.