Maxsurf Training
Tutorial 1: Design simple hull 1. If you have an existing design open, first close it by selecting File | Close. Now create a new design by selecting File | New Design. 2. Go to Data | Units, and select metres as the units for length, and tonnes for weight. 3. Go to the Surfaces | Add Surface menu. Select the default surface. 4. Make sure that you have one of the design windows topmost and choose File | Save Design As; specify the file name and where you wish it to be saved. In the Perspective window, you should have something like this (turn on the Net – Display | Net | Show Net to show all the control points, and turn on the Half display – Display | Half, so that you see just one side):
5. Set the precision to medium (Surfaces | Precision | Medium). This allows the program to work relatively quickly, without losing too much accuracy. 6. Now we can make the surface approximately the correct size for the design. This is done with the Surface | Size Surfaces command. Place a tick next to the default surface (it should be the only one in the list). Then type in the length, beam and depth values (42m, 14m and 8m respectively). Leave everything else unchecked.
96
Maxsurf Training
Save your design again (File | Save Design or by pressing the button). 7. We will add some shear to the hull by lifting the forward control point in the profile window. Remember that there is only one control point here, so it can be selected just by clicking the mouse on it and dragging it to its final position:
Now move the forefoot up a bit. Remember there are two points here so select them both by dragging a box over them:
Then click on the selected control points to move them:
97
Maxsurf Training
8. We will now fair the plan shape, so switch to the Plan window:
First we will close the bow, by dragging all the forward control points onto the centreline: If you hold the shift key down whilst dragging them, they will only move in the vertical or horizontal direction. This helps to just move them into the centreline without moving them longitudinally:
Now close the transom a little. Remember that there are two points here so drag a box over the control points to select them both and move them into the centreline a little:
98
Maxsurf Training
9. We will now add control point rows and columns to increase control of the surface. In the body plan view, add a row between the top and middle rows, by selecting Control Points | Add Row, then clicking on the activated column (whichever column has a highlighted control point), at the position you wish to place the row.
Control point columns can be added in either the plan or profile views, in much the same way as this row was added; highlight a control point in the shearline edge (topmost row), then go to Control Points | Add Column, and click on the required position of the new column, along the topmost control point row. Hydromax should add a new column here. If the shape distorts unexpectedly, undo the move, and try adding the column to the bottom edge instead. Add 2 columns of control points, one either side of the middle column; try to keep the columns evenly spaced along the length of the hull.
99
Maxsurf Training
10. Review the surface properties in the surfaces window (Window | Surfaces), you should have a B-Spline surface, with the maximum stiffness that will still allow the shape you require; this is limited by the number of control points defining the surface, so will be an iterative process; for the moment we will constrain the longitudinal flexibility to 5, and the transverse flexibility will be 3. 11. Now we can manipulate the edges to gain the desired shape. Start with the edges in the profile view then move to the plan view, and finally the body plan view. Moving between the windows a few times, verifying any changes in the other views, you should start to gain a fair overall design. 12. Now we need to set the frame of reference and zero point. First, go to Data | Frame of Reference, and click on the Find Base button, this will set the baseline at the lowest point of your design. Now enter a value of 5 m in the DWL edit box. Select Set to DWL, and the perpendiculars will be set to coincide with the intersection of the bow and transom with the datum waterline. Click OK. Now go to Data | Zero Point, and set the zero point to the Aft Perpendicular and the Baseline. Don’t check Locked Zero Point, this will ensure that if the aft perpendicular moves, the zero point will move with it.
13. To better visualise the shape, we shall add some sections. This is done in the Data | Grid Spacing dialog:
100
Maxsurf Training
Click the Add button and type 11 stations. Then click on the Space button and select "Evenly along the length of the model". When you click OK, the station positions will have been automatically calculated. To add a section at the transom click the Add button and enter 1 in the edit box. The default longitudinal position is zero, click the Sort button and rename the station to st 12. Click OK to close the window.
Similarly create 3 waterlines, make one of these the datum waterline, 2 buttocks and 2 diagonals. These can now be switched on using the toolbar buttons they will give you a good idea of the overall hull shape. Save your design again. 14. In the body plan view, if the net is turned off, the columns can be viewed and therefore manipulated individually. These are selected by clicking on the control point indicator for the column you wish to view in the inset box. The section closest to this column (and therefore the most affected by the movement of those points) is also displayed. Any other section can be viewed instead, by clicking on its section indicator in the inset box.
101
Maxsurf Training
15. By manipulating the control point net in all three views, we can achieve the required hull shape. We know that our overall dimensions are correct, but the waterline dimensions need to be altered, so that they match the design requirements. LWL is the same as LBP, because we set the perpendiculars to the DWL, so we need to manipulate the design to make this equal to 40 m, and the BWL equal to 14 m. The draught has been set to 5 m already. These dimensions can be viewed by selecting Data | Calculate Hydrostatics. This will also give you an idea of the volume of your vessel, and several other useful values, including the Block Coefficient, which should be maintained as close to the required value of 0.65 as possible, to prevent unnecessary distortion of the vessel later on. Manipulate the edges of your design first, and then the internal control points, until you are happy with the shape of your design. 16. Select Data | Parametric transformation, and select search for Block Coefficient, set the required value to 0.65, and constrain the waterline Length, Beam and Draft. Click on Search. Note: The programme is using Lackenby method to alter the position of the sections, and not the actual sectional shape, so if your vessel has a block coefficient that is a long way from 0.65, the program may not be able to find the required value. In this instance, you will need to manually adjust the sections in the body plan view to try to increase/decrease the block coefficient, and then try the parametric transformations again.
102
