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Hull Lofting Tutorial:

Start: 0
Set the first dxf: 1
Paste other dxf's: 2
Loft profiles: 3
Loft test: 4
Loft Better: 5
Shelling: 6
Full Length: 7
Keel, Mirror & Render: 8

 

 

Background:
The ship lines were created by Dr Allen Magnuson in Feb 2005 using Vacanti Prolines LE. The data was exported in 2D dxf format, then traced in TurboCad Pro 8.2. Hull is based on the proportions of Noah's Ark according to Genesis 6:15. Tutorial by Tim Lovett Feb 05.

 

STEP 5: Loft Better


1. Not a pretty sight

The hull looks nice doesn't it? - Well, not really.

Delete the loft and add the bow profile (drawn onto the "profile" workplane). Now redo the loft.

By the time you complete the bow by adding the front profile the loft is looking a little strange.  You see, the problem is the division lines do not 'flow' with the curvature very well. The best loft is one where the nodes line up to be almost  perpendicular to the loft profiles. In other words, we want the loft to be form a 'grid' of approximate rectangles instead of parallelograms.

Think of the loft forming straight lines between loft profiles. If the straight lines span the loft profiles at a steep angle the resulting loft will not be smooth. Change the texture to 'grid';

  • Select loft > RB > Properties > 3D > Category = Miscellaneous, Material = Grid > Edit Material... > Wrapping: Y plane, Scale=80 > OK > OK

Now do Quality Render. Spin and zoom to accentuate the surface irregularities.

We can play with the ACIS settings to improve this; (ACIS is the 3D geometry engine, same one as AutoCAD)

  • Options > ACIS... > Quality

But there is a limit to how much improvement we can get by increasing smoothness tolerances (and we are trading accuracy of course)


2. A better node arrangement

We want to fit the nodes along each Body to give a better loft. Try this modified set of division lines for setting the profile nodes more perpendicular to the loft. The second image shows the resulting loft, with the (purple) loft lines indicating an improved 'flow' along the hull. The 3rd image shows the much improved surface when viewed in Quality Render with "Grid" material. 

      


3. Halfway along...

The complete set of station X axis positions - measured from Station 1.

Sta

X fore

Sta

X aft

1

0

35

3089.274

2

90.861

39

3452.718

3

181.722

42

3725.301

4

272.583

45

3997.884

5

363.444

47

4179.606

6

454.305

49

4361.328

8

636.027

51

4543.05

10

817.749

53

4724.772

12

999.471

55

4906.494

15

1272.054

56

4997.355

18

1544.637

57

5088.216

21

1817.22

58

5179.077

25

2180.664

59

5269.938

30

2634.969

60

5360.799

The loft to midsection is shown below. Keep checking the loft after several profiles are done to check for any faults. If the loft suddenly splits into a large number of lines then you need to trace the faulty loft profile (Test by slipping profiles in temporary lofts until the problem profile can be isolated). 


Tim Lovett 2005 | All Rights Reserved| http://www.worldwideflood.com