Maxsurf allows you to join two surfaces together along a common edge so that the two surfaces behave as one larger surface. This procedure is referred to as Bonding. The edges may be in the same surface, or in separate surfaces.

Bonding is an extremely powerful tool to help you create all kinds of features such as areas with specific radiuses, chined transitions etc. Aside from that Maxsurf has the capability to enforce specific tangential continuity across a bonded edge.

Two rules govern which edges may be bonded together:

1. The two edges that are to be bonded must share the same number of control points along their respective edges.

2. The two edges must share the same stiffness in the direction of the edge.

Bonded surfaces are typically used to achieve particular design features where different types of surfaces or surfaces with different properties have to be used.

Typically a bonded surface is used to achieve a combination of regular hull surfaces:

·   Areas with a specific radius using conic surfaces: bilge, bowcone, transom-hull transition

·   Areas with no curvature using linear surfaces: flat plate

·   Areas where you require a different stiffness in the direction other than the direction of the edge. For example a transition from transverse stiffness 5 to transverse stiffness 3 along a longitudinal bonded edge.

Example applications

·   Knuckles in the hull, chines

·   Bowcones

·   Bilge radiuses

·   Flat of sides, flat bottom plate

·   Box shaped models, deckhouses that require plate expansion

·   Bulbous bow transition into hull

·   Tangential keel – hull transitions

Example of a model using bonded surfaces; bow cones, swim platform, radiuses and large fillets.

The advantages of using bonding are:

·   Tangent transitions between surfaces with different properties.

·   Control over the shape of the bonded edge.

·   Knuckles can be created without adding a lot of extra control points as opposed to using compacted control points.

·   Model transfers into other programs more easily (no trimming problems)

·   By dividing the model up into different panels, the plate development can be a lot easier in Workshop. You can use the Develop Surface command in Workshop without having to subdivide the surface.

The disadvantages of using bonding are:

·   It can sometimes be difficult to change the surface shape of the bonded surfaces due to tangency constraints. Applying the tangent transition at a later design stage and some practice can solve this.

·   Certain changes, such as changing the number of control points on the edge or the stiffness of the edge, affect both surfaces. This may result in:

o         A large number of surfaces (use the Assembly window to manage large number of surfaces)

o         A large number of control points

Two edges need to be selected for bonding. The first edge selected will remain stationary in space while the second edge is moved to exactly match it. The process of bonding may be performed by using the following steps:

·   Select the edge that you wish to remain stationary first,

·   While holding the Shift key down, select the second that you wish to move and bond to the stationary edge,

·   Choose Bond Edges from the Controls Menu and select the type of tangency you wish to apply to bond the edges together.

Or,

·   Select any control point, excluding corner points, from the edge that you wish to remain stationary first,

·   While holding the Shift key down, select any control point, excluding corner points, from the edge that you wish to move and bond to the stationary edge,

·   Choose Bond Edges from the Controls Menu and select the type of tangency you wish to apply to bond the edges together.

Corner points cannot be used to select edges, as they fall on two edges simultaneously, and so do not uniquely define one particular edge. Hence edges that you wish to bond must contain at least one intermediate control point.

Only two edges may be bonded together. However, if you wish more surface edges to be bonded you can manually bond the third edge by compacting and grouping the control points and make the surface stiffness’s the same.

Also see:

Advanced - Transpose on page 169 for information on how to swap rows and columns.

Maxsurf has additional options for bonding together two surface edges while maintaining overall fairness across the surface edge. This is particularly useful in situations where it is necessary to create a number of surfaces in an area of the hull but no discontinuities are desired. Maxsurf has three options to bond together two edges

·  No Tangency

·  Approximate Tangency

·  Strict Tangency

No Tangency:

Ensures that each control point along the bonded edge maintains the same location as the corresponding point on the other surface and the surface has the same stiffness in the direction of the bonded edge.

Original surfaces to be bonded

Bonding with No Tangency, points on edge share same location

Approximate Tangency:

Ensures that the two control points in the same row or column perpendicular to the edge remain in a straight line. This is the same effect you can get by using the Align to Vector command and it helps ensure that the surfaces share a common tangent direction across the edge. In some cases, particularly when there is significant twist in the surface, this is not sufficient to guarantee tangency and the third bonding option must be used.

Approximate Tangency – Rows are colinear across the surface edge

Strict Tangency:

Ensures both that each row or column running across the surface edge is kept in alignment with the corresponding row or column on the other surface, and also that the next control point on each side of the edge is kept at an equal distance from the edge. This guarantees tangent continuity in all cases.

Strict Tangency – Rows are co-linear across surface edge and points are equal distance from the edge

After bonding with a tangency constraint, and points either side of the edge are moved, the points on the opposite side of the bonded edge will move in the opposite direction to maintain continuity. If a point on the edge is moved, then both adjoining points will be moved in the same direction and by the same amount.

When bonding two edges together using tangency constraints, some control points will be moved by Maxsurf to ensure continuity. In this case, the rule as to which points remain unchanged and which points are modified is the same as that used with simple bonding. The first surface selected is treated as the master surface and is not modified in any way. The second surface selected is regarded as the slave surface, meaning that Maxsurf will modify points in this surface as required to meet the constraints.

Positioning the mouse cursor over a bonded edge will display both edge names and the continuity constraint in the bottom left of the status bar:

The following types of bonding annotations are possible:

·   C0 = No Tangency

·   C1 Lenient = Approximate tangency

·   C1 Strict = Strict Tangency

If a bonded edge is selected, the bonding constraint will be displayed ticked in the Bonding menu:

You can change the type of tangency easily by simply selecting a bonded edge or a control point on that edge, excluding corner points, and re-apply the bonding.

Selecting a shared control point on a bonded edge.

Any two edges may be unbonded by selecting the bonded edge or a control point on that edge, excluding corner points, and choosing Unbond from the Controls menu. Once the edges are unbonded they are free to move independently.

Edges within a surface may also be bonded to one another as long as they follow the requirements of number of control points and stiffness. If you wished to form a closed surface, you might start off with the following net arrangement, with the object being to bond the two edges as indicated.

This net would generate a closed surface joined along the bonded edge. To highlight the bonded edge as shown, select the Bonded Edges option from the Contours dialog.

Bonding can effectively combine two surfaces to form a larger surface. As a result, commands that previously worked on single surfaces treat bonded surfaces as one. Examples of this are:

Adding and Deleting of controls, where the row or column extends across a bonded edge.

Surface locking, where all surfaces that are bonded together are locked or unlocked in unison.

The Size Surface function, i.e. bonded surfaces cannot be sized independently.

Surface movement commands such as Move, Flip, Rotate and Align.