H U L L F O R M V E R S I O N 3 U S E R S' M A N U A L Revision Version 3.28A Date 2 February, 1991 BLUE PETER Marine Systems Pty Ltd 92 Dyson St, Kensington, Western Australia 6151 Phone 61 9 367 6949 COPYRIGHT The following conditions apply to registered users only. Unregistered users should refer to the contents of file REGISTER.TXT. A registered user is a user who has been issued, by BLUE PETER Marine Systems Pty Ltd, a diskette containing a copy of the program HULLFORM.EXE marked with a serial number (of form "Annnn" or "Bnnnn", where "nnnn" represents 4 decimal digits). ---------------------------------- This document, and the software it describes, is copyright 1989, BLUE PETER Marine Systems Pty Ltd. It may not be copied in whole or in part without the express written approval of BLUE PETER Marine Systems Pty Ltd. BLUE PETER Marine Systems Pty Ltd makes the following formal approvals, regarding the program and other material supplied on the diskette: The program file (entitled "HULLFORM.EXE" on the supplied diskette) may be copied to a second diskette, with the supplied diskette retained for archival purposes only. The program file may be copied to a hard disk or RAMdisk, on any machine, provided the user accepts full responsibility to ensure that only one such copy is in use at any time. Any number of copies of the configuration file ("CONFIGUR.HUL") and the sample data files (in subdirectory HULLDATA) may be made. LIMITED WARRANTY BLUE PETER Marine Systems Pty guarantees the manual and supplied diskette to be free of material defects, for a period of 60 days from receipt. In the event of notification of defects, sent within the above 60 day period, BLUE PETER Marine Systems will replace the faulty goods. No other remedy is available through this warranty. The supplied program HULLFORM is a designer's aid only. Ultimate responsibility for the accuracy all calculations is that of the designer, and not of the program. BLUE PETER Marine Systems Pty Ltd disclaims all liability for any limitation or error of the program in the performance of its assigned tasks. In no event shall BLUE PETER Marine Systems Pty Ltd be liable for any loss of profit, lost savings, other incidental or consequential, or any other commercial damages, arising from use of the program. CONTENTS PHILOSOPHY 1 THE MATHEMATICAL MODEL 2 PROGRAM OPERATION 5 0. EXIT TO OPERATING SYSTEM 6 1. Hull lines, input from and write to disk 7 1. Input hull lines from disk file 7 2. Write hull lines to disk file 8 3. Read dynamic waterline data from file 9 4. Write waterline offsets to disk file 9 5. Write section offset data to disk file 9 2. Change hull lines 11 1. Add a new section 11 2. Delete a section 12 3. Edit a section 12 4. Add a new hull line 14 5. Delete a hull line 15 6. Smooth hull lines 15 7. Alter line to which stem fits 19 8. Rescale hull dimensions 20 9. Re-section hull 20 10. Delete current hull 22 3. Plot hull lines 23 Option 1 Perspective view 23 Options 2 to 5 Geometric Drawing Options 26 4. Displacement and stability calculations 28 1. Change heel angle 28 2. Change pitch angle 28 3. Change hull displacement 29 4. Move longitudinal centre of mass 29 5. Move vertical centre of mass 29 6. Change waterline offset 29 7. Find hull state given above displacement 29 8. Find hull state given above waterline offset 32 5. Alter program configuration 33 TUTORIAL INTRODUCTION 37 Example 1. Design of a Simple Hull 37 Example 2. Smoothing a Complicated Hull Section 41 HELPFUL HINTS 43 256K Memory Limit 43 Aborting the Program 44 Designing a Hull from Scratch 44 GLOSSARY 46 INDEX 50 ---------------------------------------- HULLFORM VERSION 3 PHILOSOPHY HULLFORM was developed because, while there are other such programs on the market, they were perceived to be highly expensive, of frequent unreliability, and extremely computation-intensive. As a result, a major fraction of the potential market (who have only limited computer resources) was not being served, and the higher end of the market was not being as well served as it might. HULLFORM is a simple hull design program, portable between a range of computers and graphics devices. Its philosophy is to perform its tasks as simply as possible, thereby allowing calculations to be performed within reasonable time using a minimal hardware specification. For example, while most current offerings use two-dimensional smoothing (operating on surfaces, rather than lines), HULLFORM uses one-dimensional smoothing, applied transverse to the hull, and lengthwise. There is no evidence that the smoothed surfaces obtained from a two-dimensional approach are in any way optimal, or even better than the result of HULLFORM's one-dimensional smoothing applied in two directions. (The display of a surface, rather than a line, being distorted is certainly more impressive, but does this justify a $10,000 computer rather than a $1,000 one?) In its current form, HULLFORM's minimal acceptable configuration is an IBM PC-compatible computer, with 256K (for the personal version) or 512K (for the professional version) of memory, and either a CGA, EGA or Hercules graphics display. It is optimised for the design of small craft, and handles hard-chine sections much more readily than alternatives. It can represent up to six (or 32 for the professional version) curved surfaces on each side of the hull, so handles normal hull sections readily. In addition, offsets for existing hull designs may be directly used as data. The simple cross-section model is central to the program's philosophy; by using mathematically- specified section curves, fine summations transverse to the hull axis are avoided, and calculations are made simpler - and faster. High-precision calculations (up to 60 sections) may be completed in reasonable time, even on a 4.77 MHz PC. You can design a mathematically- precise hull, even on your office word- processing system. (C) BLUE PETER Marine systems Pty Ltd ------------- page 1 ---------------------------------------- HULLFORM VERSION 3 THE MATHEMATICAL MODEL The program holds in its memory, a model of the hull which parallels closely the way many small craft are built: The hull is constructed across transverse sections, each at user-specified locations along the hull axis. The sections are assumed symmetrical, so only half of each section needs to be specified. The sole exception to this rule is the first section, which corresponds to the stem. Catamaran or trimaran forms may be represented, with asymmetric hulls if required. Between the sections run longitudinal hull lines, whose coordinates at the section positions coincide with the section boundary. These lines are indexed, the program assuming the highest-number line to correspond to the keel of the yacht (although this may be of finite width). Between the hull lines, at each section, form control variables determine the curvature (or non-curvature) of the hull surface. The hull sections, lines and control variables may be separately edited, to generate the required hull shape. In some cases, hull lines will coincide (e.g., when a fin keel is added, the keel will be of zero size over most of the length of the hull). The program recognises this, and when any line is moved, all higher-index lines coincident with it are altered to match. All hull dimensions may be specified in feet or metres. If the former is selected, any data written for use in hull construction are output in feet and inches. When feet are the selected units, masses may be specified in pounds or tons; when metres are used, masses may be specified in kilograms or tonnes. The positions of the hull lines points of each section are normally specified in terms of the vertical and lateral (horizontal) offsets a boatbuilder might use, when constructing a hull in an inverted position. Thus, vertical offsets are greatest for the keel or skeg, least for the gunwhale. However, this convention may be reversed by selection of the appropriate option in the program configuration. Note that this feature only changes the mode of display of the hull vertical offsets, not the data stored. If a hull is designed using one of the above options, and the selected option changed using option 5 of the main menu, the redisplayed hull will not be inverted, only the associated coordinates. In order to invert the hull, the user may use the "change hull lines" (option 2) / "rescale hull dimensions" (option 8) selections from the main and (C) BLUE PETER Marine systems Pty Ltd ------------- page 2 ---------------------------------------- HULLFORM VERSION 3 subsidiary menus, entering a multiplying factor for -1 for the vertical offsets. The hull curvature between lines follows the form of a quadratic, which allows arbitrary alignment at either end. The alignment is defined by a "control point", lines from which to either curve end are tangential to the curve. The vertical control is the fraction of the vertical distance from the higher-index hull line to the lower- index one, at which the control point lies. The lateral control is the distance between control point and the intersection point of the straight projection of the previous hull curve (meeting the lower-index line) and the horizontal line already defined by the vertical control fraction. Therefore, a perfectly "hard-chine" surface can be generated by a value of 1 for the vertical control factor (a value of 0 for the lateral control is recommended). A smooth curve ("soft chine") can be produced by a zero value for lateral control, and a less-than-unit value for the vertical control. Similarly, a rounded bottom can be generated by using a vertical control factor of zero for the lowest hull section curve. Using this algorithm, it is possible to represent efficiently a wide range of hull forms. Flared, curved or flat topsides may all be modelled, deck structures may be included, and a wide range of keel forms may also be handled (See fugure 4). The locations or the hull sections are specified in the current measurement units, increasing from bow to stern. The position along the hull where the zero value for position occurs is arbitrary, but either the hull centre, or bow, are recommended. Once the hull has been defined, the program can perform a number of calculations of its dynamic and static properties (e.g., displacement, righting moment). These are found by trapezoidal integration between bow and stern. This technique is less accurate than schemes employed by other such programs. It is used because discontinuities between sections (e.g., transoms) are often used in small craft design, and these generate gross errors when higher- order schemes are employed. As a general guide, errors are about 1% for a hull specified using about 15 sections. For greater accuracy, more sections can be used, errors decreasing in proportion to the square of the number of sections. The program allows ready addition of sections. However, the user must beware the same errors as arise (C) BLUE PETER Marine systems Pty Ltd ------------- page 3 ---------------------------------------- HULLFORM VERSION 3 unseen in other programs - irregularities, near locations on the hull where discontinuities occur. Use of the program's graphics capacity will provide an easy check. (C) BLUE PETER Marine systems Pty Ltd ------------- page 4 ---------------------------------------- HULLFORM VERSION 3 PROGRAM OPERATION The program uses a simple menu-driven interface, to permit portability to a variety of machines (some of which may use terminals on relatively slow serial lines). Between two and four "levels" of menus are involved in obtaining a single result, but menu options are selected to minimise transitions between levels. There are two forms of menu: Text-mode menus are a list of enumerated options, from which the user selects. By convention, option 0 returns to the previous menu, as does pressing the ENTER key (or RETURN key on some machines). Other text-mode inputs (such as the name of a hull data file) are insensitive to the case used (upper or lower), and also require an ENTER when completed. Graphics-mode menus are presented in abbreviated form on the top line of the screen. Selections may include numeric, alphabetic or cursor key inputs, and (with a few exceptions) involve single-character inputs for which pressing the ENTER key is not required. The program is initiated by the command "HULLFORM". The screen clears, with a sign-on screen displayed. When the user presses any key, the main menu appears: MAIN MENU Currently no hull defined 0. EXIT TO OPERATING SYSTEM 1. Hull data, input from and write to disk 2. Change hull lines 3. Plot hull lines 4. Displacement and stability calculations 5. Alter program configuration Enter required option (0-5) : Details on the meaning and use of each option follow. (C) BLUE PETER Marine systems Pty Ltd ------------- page 5 ---------------------------------------- HULLFORM VERSION 3 0. EXIT TO OPERATING SYSTEM This may be used when use of the program is completed. It may not be compulsory, however - the program keeps no files open, so under MS-DOS on an IBM-compatible PC, the machine may be turned off with the program resident, without loss of data. Entry of 0 leads to a request for confirmation: Exit requested - confirm? (Y/N): for which a response of "Y" or "y" is required for an exit to be effected. When exitting from a program, you should always make sure you have saved your work results. Even if you feel the hull you have generated is not good, the output file only occupies only a few thousand bytes of storage (out of 360K on the smallest diskette), and you may change your mind later about its value. You might, for example, keep one filename for your current work file - e.g., "WORKFILE" or "INTERIM". (C) BLUE PETER Marine systems Pty Ltd ------------- page 6 ---------------------------------------- HULLFORM VERSION 3 1. Hull lines, input from and write to disk This allows a user to save, and retrieve at a later time, the results of a work session, or dynamic waterline data for use in association with a selected hull. All data are stored in text files on disk, which may be edited external to the program by an experienced user. They may include the "_" (and, on PC systems, "-") if required. Upper and lower case letters are equivalent - e.g., "mary_lou" and "Mary_LOU" are the same set of hull lines. If it is desired to read a set of lines from, or save them on, a disk or directory which was in not use at the time the program was loaded, it may be specified, prefixed by the disk - e.g., a hull name, "A:MARY_LOU". The menu seen is: Options are: 0. Return to previous menu 1. Input hull lines from disk file 2. Write hull lines to disk file 3. Read dynamic waterline data from file 4. Write waterline offsets to disk file 5. Write section offset data to disk file Enter your required option: Details are: 1. Input hull lines from disk file In response to entry of "1", the program provides a listing of files in the hull data directory, and a prompt of format: Hull data files in directory: B:\DATA\ DINGHY MARY_LOU SKIBOAT SHIP TEST TRAWLER Enter file name (or RETURN to abort): and input of the name of a hull data file name will result in an attempt to read the hull lines. The name may have up to eight characters, but must not include the file extension allowed by the operating system; a standard extension of ".HUD" is appended. (The hull file format is detailed on the following page) Success will be confirmed by a message such as 11 sections read (C) BLUE PETER Marine systems Pty Ltd ------------- page 7 ---------------------------------------- HULLFORM VERSION 3 showing the number of hull sections read from the file, which should match the number saved. 2. Write hull lines to disk file Entry of "2" produces a prompt identical to the above, to which any name, consistent with the rules outlined above, may be specified. A confirmatory response is again generated - e.g., 11 sections written Note that the user is warned, and asked for confirmation, if an attempt is made to overwrite an existing file. When the main menu reappears, it will show the name of the file last read or written, in form such as "Currently using hull: MARY_LOU" The hull file format is typified by the following example, of a dinghy 5 metres long: 242.823 0.046 0.300 1 3 3 -2.5000 0.0000 -0.6010 0.0000 0.0000 0.0000 -0.2400 0.0000 1.0000 0.0000 0.0019 0.0000 1.0000 -2.0000 0.2760 -0.5760 0.0000 0.0000 0.1957 -0.2220 0.0000 1.0000 0.0000 0.0655 -0.0027 0.0000 -1.5000 0.5040 -0.5520 0.0000 0.0000 0.3565 -0.2040 0.0000 1.0000 0.0000 0.1114 -0.0116 0.0000 -1.0000 0.6840 -0.5280 0.0000 0.0000 0.4819 -0.1860 0.0000 1.0000 0.0000 0.1397 -0.0251 0.0000 -0.5000 0.8160 -0.5040 0.0000 0.0000 0.5754 -0.1680 0.0000 1.0000 0.0000 0.1503 -0.0466 0.0000 0.0000 0.9000 -0.4800 0.0000 0.0000 0.6417 -0.1500 0.0000 1.0000 0.0000 0.1433 -0.0789 0.0000 0.5000 0.9360 -0.4560 0.0000 0.0000 0.6836 -0.1320 0.0000 1.0000 0.0000 0.1221 -0.1183 0.0000 1.0000 0.9240 -0.4320 0.0000 0.0000 0.6988 -0.1140 0.0000 1.0000 0.0000 0.0936 -0.1519 0.0000 1.5000 0.8640 -0.4080 0.0000 0.0000 0.6783 -0.0960 0.0000 1.0000 0.0000 0.0632 -0.1555 0.0000 2.0000 0.7560 -0.3840 0.0000 0.0000 0.6138 -0.0780 -0.0000 1.0000 0.0000 0.0318 -0.1087 0.0000 2.5000 0.6000 -0.3600 0.0000 0.0000 0.5000 -0.0600 -0.0000 1.0000 0.0000 0.0000 0.0000 0.0000 The first line shows the displacement (242.83), horizontal and vertical positions of the centre of mass (0.046,0.300), the units code (1), number of hull lines (3) and the stem line (3). (See "Change Hull Lines" item 7 for explanation of the last of these) Subsequent lines show, for each section, firstly the fore- and-aft position of the hull section, then groups of four numbers specifying the lateral and vertical offsets, and the values of the two curvature control parameters. The number of sections for the hull is determined when the program detects an end to the data. (C) BLUE PETER Marine systems Pty Ltd ------------- page 8 ---------------------------------------- HULLFORM VERSION 3 3. Read dynamic waterline data from file Stability, wetted surface, and other such factors change when the motion of the hull distorts the water level about it. This effect can be included, by creating a file containing a set of pairs of numbers in sequence, the first being position along the hull (specified exactly as for the section positions), and the second a water-level height, positive upward. For example, the following set shows (for operation in metric units) water level displaced 20 cm upward at the bow (position -4 metres), -10 cm at the mid-section (position 0 metres), and 25 cm upward at the stern: -4 0.20 0 -0.10 4 0.25 The data format in the file, as long as the proper ordering (as above) is unimportant. Pairs may also, for example, be placed on a single line, two pairs to a line, or each pair may be entered over two lines. Up to 60 heights may be entered, but need not be - the program will take any number up to this limit, and interpolate the data to the existing section positions of the hull in use. Note that this means that, when hull sections are added, removed or shifted, or a new hull is input, the dynamic waterline data must be re-read. 4. Write waterline offsets to disk file This one was mainly for our own use. We experimented with quick ways of estimating the waterline information needed for use of menu item 3, above, based on a variety of approaches centred in thin-ship theory. If you can find a use of your own, you're welcome to it! 5. Write section offset data to disk file This one is for the boatbuilder. It will write out a set of measurements, which will allow him (or her) to lay out each section with the same mathematical precision as used in the program - simply, for each, a set of horizontal and vertical offsets for the outside of each section, sufficiently close to allow accurate reconstruction of your design. You can write your data to a file, or send it direct to the printer by nominating PRN as the output filename. For flat surfaces between hull lines, the program will only output the hull line points. Where the surface is curved, (C) BLUE PETER Marine systems Pty Ltd ------------- page 9 ---------------------------------------- HULLFORM VERSION 3 the interval may be controlled by the user. The program prompts: Enter nominal separation for points on section, default .1000 m : Pressing of the RETURN key results in points being output at the above interval (shown as 0.3333 ft when British units are selected), with any valid numeric input changing the default. (C) BLUE PETER Marine systems Pty Ltd ------------- page 10 ---------------------------------------- HULLFORM VERSION 3 2. Change hull lines This is the entry point through which all changes to the hull are specified. Entry of "2" produces the secondary menu: Options are: 0. Return to previous menu 1. Add a new section 2. Delete a section 3. Add a hull line 4. Delete a hull line 5. Edit a section 6. Smooth hull lines 7. Alter hull line to which stem fits 8. Rescale hull dimensions 9. Re-section hull 10. Delete current hull Enter your required option: 1. Add a new section Option 1 allows addition of new sections, either to an existing hull, or from scratch where a hull is being created anew. (In the latter case, the section details correspond to an arbitrary guess). It leads to a screen display of form: Stations are located as follows: 1: -2.50 2: -2.00 3: -1.50 4: -1.00 5: -.50 6: .00 7: .50 8: 1.00 9: 1.50 10: 2.00 11: 2.50 Enter required position (X to abort): The display shows the longitudinal position of each section in use, from bow to stern (the case above corresponding to a 5-metre dinghy). The user may then decide where the new section is to be inserted. If you change your mind, simply enter an "X" (or any other non-numeric character, as long as your intent is clear). When the new section has been added, the program automatically enters "graphic edit" mode. (For details, refer to option 3, below) However, all that is necessary is entry of the letter "Q" (or "q"), without pressing the RETURN key. The result is the enquiry: Do you want to insert this section? (Y/N) : Entry of a "Y" or "y" (with a following press of the RETURN key) will add the section, and return the user to the "change hull lines" menu. (C) BLUE PETER Marine systems Pty Ltd ------------- page 11 ---------------------------------------- HULLFORM VERSION 3 2. Delete a section Here, the user is shown the section positions, and may then specify which to remove. The screen shows information of format: Enter station to be removed (1-11, X to abort): Upon entry of the required number, a confirmation is requested - e.g., for station 4 above, in format: Do you mean station 4, at 1.50 units from the bow? : Entry of answer "Y" or "y" will lead to removal of that section, leaving (in the above example) 10 sections in the hull representation. 3. Edit a section Any hull section may be edited, using on-screen graphics or numeric inputs in text mode. The section editing menu is shown first: Options are: 0. Return to previous menu 1. Select edit section by number 2. Select edit section by position 3. Edit section graphically 4. Edit section parameters directly Enter required option: Sections are specified using options 1 and 2, the former where the sequence number of the section is known, the latter where its position is known. Once the section has been specified, it is shown on the section editing menu (e.g., "Current section: 4"). If the approximate position of the section is specified, confirmation is requested - e.g., Enter section position: 0.15 Nearest is number 7, at .120 Is this the one? (Y/N): Y The graphic edit option, 3, allows modification of a section to a shape within "qualitative" requirements. Selection of this option leads to a plot on the screen of a half-section, along with scales (in the currently selected length units), a plot of the curvature of the hull section at right, and a top-line prompt. (C) BLUE PETER Marine systems Pty Ltd ------------- page 12 ---------------------------------------- HULLFORM VERSION 3 In this mode, by use of the digit keys, letter keys O, C, D, H, R, A, Q, and the cursor keys, the user may interactively alter the hull section form. The elements of the above line represent: lin-no the hull line number, as defined in section 1 Offset the hull line at this point is to be moved Contr the curvature control point for the curve above the selected point is to be moved Follow the hull line at this point is to be moved, following the hull curve Doub double the increment made when a cursor key is pressed Half halve the increment made when a cursor key is pressed Redr clear the screen and redraw the half-section arrows referring to the four cursor keys, marked with arrows Also plot other section(s) for comparison Quit finish, and return to the section edit menu D= .040 the initial increment per keystroke for "Offset", "Contr" or "Follow" modes Thus, by pressing any of keys 1 to the number of hull lines chosen, the O key, and then the cursor keys, the user may move - both horizontally and vertically - each of the points defining the turning points of the section. Similarly, pressing the C key, and the cursor keys, the user can adjust the curvature of each segment of the section outline. Note that, when "C" is pressed, the hull tangent lines intersecting at the control points are shown. These provide useful information when editing control points, and may be removed by pressing either "O" or "F", and the redrawing the screen using the "R" key. The meanings of the "Double", "Half" and "Redraw" options will be obvious (if not immediately then certainly when they are tried). The "Also" option produces the request: Also plot which sections ("n,n,.."): to which up to 10 sections may be provided. These will be shown on-screen, in the same manner as the section being edited. Refer to the end of the manual ("Tutorial Introduction" 2) for further detail on the use of the section-edit graphic mode. The direct edit option 4, allows entry of known offsets where a section is known already, and fine adjustments. The menu presented is of typical form: (C) BLUE PETER Marine systems Pty Ltd ------------- page 13 ---------------------------------------- HULLFORM VERSION 3 Section 6: Section position: parameter (0.0) .000 Offsets Control Parameters Lateral Vertical Lateral(offset) Vertical(factor) (1.1) 6.000 (1.2) 2.000 (1.3) .000 (1.4) .000 (2.1) 5.800 (2.2) -.500 (2.3) .000 (2.4) .000 (3.1) 5.000 (3.2) -1.000 (3.3) .000 (3.4) 1.000 (4.1) 4.200 (4.2) -.500 (4.3) .000 (4.4) 1.000 (5.1) 4.000 (5.2) 2.000 (5.3) .000 (5.4) 1.000 Enter index ("n.n") and value, or [RETURN] to exit: Note that the values are indexed by a "decimal" parameter, for which the strict format "n.n" must be followed. All parameters may be changed, but the section position may not be moved beyond the range defined by neighbouring sections. The meanings of the "offsets" and "control" variables were described earlier in this manual (Refer to "The Mathematical Model"). They control the curvature of the curved part immediately above the hull line concerned. The user should also see that, in cases where the a line is coincident with another of higher index, changes to its position will be matched by changes to the others. A coincident line will only remain separated once it has been moved explicitly. The curvature plot may be used to maintain a high order of smoothness of the hull. Movement of the curvature control point alters the distribution of curvature between each pair of hull lines, and so may (if desired) be used to match the curvatures of the section edges at the hull line points. 4. Add a new hull line Up to six hull lines may be used, with initial location anywhere on the hull. The selection of this option leads to the prompt, of typical form: There are 3 hull lines now. Specify where hull line must be entered: 0. Not at all (i.e., exit from request) 1. At line 1. 2. Between lines 1 and 2. 3. Between line 2 and 3. 4. At line 3. Enter required position code: Selection of option 1 or (in the above case) 4 will produce a hull line only infinitesimally different to the nominated line; the line will therefore be identified as different to (C) BLUE PETER Marine systems Pty Ltd ------------- page 14 ---------------------------------------- HULLFORM VERSION 3 its "parent" line by the program, and so not constrained to move with it as the parent line is altered (Refer to "The Mathematical Model", at the start of this manual). The other options locate the new hull line approximately mid-way between the nominated lines. It is initially generated with control values such that each the outline of each hull section passes smoothly through the line. When the new line has been added, the above menu is returned, with an additional entry showing the presence of the extra line. Option 0 may then be used to return to the "change hull lines" menu. 5. Delete a hull line Request of this option leads to a prompt of typical form: There are 3 hull lines now. Specify which line must be removed: 0. Not at all (i.e., exit from request) 1-3. Remove line of this number Enter required position code: Once a line has been removed, the above menu is re- displayed, showing the number of hull lines reduced by 1. Option 0 may then be used to return to the "change hull lines" menu. 6. Smooth hull lines Whatever method used to design a hull, once approximate sections have been defined, it is normal to fair the resulting hull lines. This section of the program provides this facility. The hull smoothing menu, in its full form, is presented typically as follows (where the selected line is 2): HULL SMOOTHING MENU 0. Return to previous menu 1. Select line number for smoothing (now 2) 2. Lateral offset 3. Vertical offset 4. Lateral Control 5. Vertical Control 6. Angle from horizontal to hull line 1 Enter option: (C) BLUE PETER Marine systems Pty Ltd ------------- page 15 ---------------------------------------- HULLFORM VERSION 3 When first presented, only options 0 and 1 are provided. Once a hull line has been selected, 2 to 5 are made available, and 6 also when the hull line selected is number 2 or greater. This display shows the standard "backup menu" option, and allows editing each of the relevant hull section parameters for all hull lines. Options 6 to 9 also allow alteration of the angle from one hull line to the prior one, for use in tasks such as fixing the deadrise of a hard chine hull, or the inclination of a side-deck. Once a smoothing option has been selected, it is presented on a graphical screen. This screen shows: - in its upper half, a scaled form of the longitudinal profile of the selected parameter, with both the zero- offset line (unlabelled) and the waterline (labelled "WL"), and a scale to the left. - in its lower half, a plot representing the curvature of this line. - in between, a set of numbers showing the positions of each of the sections in use. The aim of smoothing is generally to minimise curvature, so both halves of the plot should be considered. The top-line prompt indicates that nine command options are provided, corresponding to the upper-case letters shown. In sequence: Smooth points: Entry of an F will produce the prompt "Enter sections to free ("n,n,.. or n:n"):". The user may enter the sequence numbers the desired sections, separated by commas, or enter a range in "n:n" format, or a combination of both. for example, the input: 2:5,7,9:14 would allow freeing of the hull line at points 2, 3, 4, 5, 7, 9, 10, 11, 12, 13, 14 and 15 A curve will be fitted through the offsets for the remainder of the sections, generating a new curve seen on- screen. The curve-fitting scheme used is a "cubic spline", the mathematical equivalent of fixing a batten to the corresponding points on hull frames, while still permitting its fore-and-aft motion. Thus, the process represented is (C) BLUE PETER Marine systems Pty Ltd ------------- page 16 ---------------------------------------- HULLFORM VERSION 3 the freeing of the batten at selected frames, and seeing what happens. Naturally, it generates a fairer curve. After overdrawing of the proposed new curve (and curvature) the user is then prompted "What fraction of the relaxed offsets do you want to include:" The input selects what curve will be accepted. Entry of 0 will hold the old curve, while 1 will select the new one. Any input value is valid, not only decimal values between 0 and 1, but any others - with consequent "unrelaxing" (for values less than 0) and "overrelaxing" (for values greater than 1) effects. Pull point: When the necessary change is obvious, it may be more efficient to move the point manually - i.e., "pull" it outward or inward. The "P" option leads to a prompt for the section number of the point to be altered, then the user may move it up or down using the up- and down-cursor keys, the H and D keys to halve and double the motion increment, and the Q key to exit to the previous menu. Follow: The "Follow" option allows the hull line to be moved without distorting the hull surface above. This may be desirable in cases such as when opening out a line near the keel, to accommodate a skeg or fin keel. With use of the up- and down-arrow keys, the selected point will be moved vertically on the screen (as for "Pull"), but the other coordinate and control points will also be changed so that the curve changes in length, but not in shape. When editing a lateral offset, the line will be moved to follow the hull curve prior to the line being edited. When editing a vertical offset, the line will be moved to follow the hull curve following the line being edited. This facility equates to that available in section-edit mode, but can only support the "follow" movement in one direction at a time: When editing a line's lateral offsets, the altered point follows the form of the hull curve between it and the prior hull line. When editing a line's vertical offsets, the altered point follows the form of the hull curve between it and the next hull line. Redraw: Old curves are left on the screen, for the user's reference. They may be removed by this command, which clears the screen completely, and redraws only the curves for the current section parameter. When redrawn, the curves are rescaled, a feature which is useful when smoothing has reduced the curvature of the hull line. (C) BLUE PETER Marine systems Pty Ltd ------------- page 17 ---------------------------------------- HULLFORM VERSION 3 end-Curve: In fairing a hull line, it may be desired to carry curvature to the end of the hull (e.g., for a gunwhale, at the stern), or to reduce it to zero (e.g., at the bow). This feature provides the choice. When "C" is pressed, you are prompted: Enter bow curvature factor (0-1): The number you input is the ratio of assumed curvature at the end concerned, to that at the adjacent section. The program initially assumes a ratio of zero at both ends. To permit straight end lines, enter zero; to produce a steady curve, enter 1. (Any numeric value is allowed, the "0-1" range being purely a reminder. If a large end curvature is desired, a factor of 10 or more will be needed) After this input, you are similarly prompted for the stern curvature factor. Ignore: In many circumstances, a sudden change in a line's offsets can generate a very large curvature. As a result of the program's automatic scaling, other values may then be drawn close to the zero line. This option allows the user to inform the program that such points should be skipped. Thus, consider an example where a hull line joins the keel at section 5 (as might happen to a chine on a multiple- chine hull). The offsets for this line, at sections 1 to 4, will match those of the keel, and there will normally be a large curvature at point 5. The problem points are numbers 1 to 4, so after pressing key "I", the user should enter the range specification "1:4". When the screen is next redrawn, the hull line will miss these points, and the curvatures which they affect (at points 1 to 5) will disappear. Also: When redesigning any line, it is often useful to be able to refer to related ones (e.g., the gunwhale lateral offset, while working on the chine lateral offset). The program responds: Also plot which lines [1-m] ("n,n,.."): where "m" is the number of lines currently in use. Thus, for example, the gunwhale offset (vertical or lateral, as appropriate) can usually be displayed be obtained by entry of "1". (C) BLUE PETER Marine systems Pty Ltd ------------- page 18 ---------------------------------------- HULLFORM VERSION 3 Note that the current edit data are flagged at the end of the line - i.e, "Ve" for vertical, "La" for lateral, "Of" for offset and "Co" for control. Quit: On pressing of "Q", you will normally be returned to the hull-smoothing menu. The sole exception occurs for option 6, for which the smoothed angles may be applied in four ways - by moving either of the two hull lines used, and by moving the selected line horizontally or vertically. The "exit" menu for option 6 is presented in typical format: Inter-line angle smoothing menu Line currently selected to be changed is 1 which will be moved: VERTICALLY Options are: 0. Quit without altering any line 1. Change selected line to 2 2. Select movement of line HORIZONTALLY 3. Perform changes Enter selection: Options 2 and 3 result in "toggling" between the two options possible. When the desired combination is shown on-screen, it may be invoked by choice of option 3. 7. Alter line to which stem fits By default, the stem is taken to form a continuous curve with the highest-index hull line. For catamarans, this is not the correct choice, however. For example, a catamaran design might use hull line 1 for the outboard gunwhale, line 2 for the outboard chine, line 3 for the keel, line 4 for the inboard chine and line 5 for the inboard gunwhale. In this case, the stem would tie to line 3, not the default of line 5. On selection of option 7, you are only asked for the index of the line desired. This index will be maintained by the program, being incremented, for example, when a new hull line of lower index is added. Trimaran designs may also be developed, but the program only allows for one stem. Additional sections may be added to generate the other stem profile, in such a case. (C) BLUE PETER Marine systems Pty Ltd ------------- page 19 ---------------------------------------- HULLFORM VERSION 3 8. Rescale hull dimensions This facility is useful when using one hull design as a basis for another of different size, or converting between metric and British measurement units. The menu presented is typically: Options are: 0. Return to previous menu 1. Multiply all vertical dimensions 2. Multiply all lateral dimensions 3. Multiply all section positions 4. Convert units to ft and lb Enter option (0-4): When any of options 1 to 3 are selected, the user is then prompted: Enter required scale factor (or RETURN to abort): to which the required size multiplier must be input. Once the scale factor has been input, the scaling is performed immediately. Option 4 allows conversion of the dimensions in which a hull has been developed "en bloc". Length units are converted between feet and metres, and between either kilograms and pounds, or tonnes and tons. The displacement, and most recently computed waterline, are also converted. This facility has proven to have a number of uses. For example, if a hull's offsets are inadvertently entered using the wrong vertical offsets convention (upward versus downward), a multiplying factor of -1 applied to the vertical offsets will solve the problem, in conjunction with selection of the correct convention using main menu option 5. In addition, section dimensions can be entered in inches or millimetres, then modified to feet or metres by multiplying by 0.08333333 or 0.001 respectively. 9. Re-section hull This facility allows alteration of section positions, for a hull whose shape has been defined already. For example, a few critical sections may have been set, and a greater number then required for accurate calculations The initial screen display is a warning: (C) BLUE PETER Marine systems Pty Ltd ------------- page 20 ---------------------------------------- HULLFORM VERSION 3 Re-section hull IT IS STRONGLY RECOMMENDED THAT YOU SAVE YOUR CURRENT HULL DATA SET BEFORE PROCEEDING. ALL EXPLICIT SECTION DATA YOU HAVE WILL PROBABLY BE LOST. Press RETURN to proceed, any other to quit ... This warning is given because the new section data will overwrite the old. If you have any doubts at all that the exercise will be a success, save your hull lines before returning to this section of the program. If the RETURN key is pressed, a new screen is presented, of typical form: Stations are located as follows: 1: -2.50 2: -2.00 3: -1.50 4: -1.00 5: -.50 6: .00 7: .50 8: 1.00 9: 1.50 10: 2.00 11: 2.50 Options are: 0. Return to previous menu 1. Select uniform section intervals 2. Specify new section positions explicitly 3. Perform re-sectioning For options 1 and 2, the program firstly prompts for the number of sections required. Then, if option 1 has been selected, the new sections will be spread uniformly from bow to stern by the program. If option 2 is used, the screen clears, with the prompt: For each section, enter a new value, or X to retain the old one Section 1: {user input here} Section 2: {user input here} .. .. On completion of either task, the menu is re-presented, but now showing both the original positions, and the new ones. At this stage, new sections have not yet been calculated, and if those displayed are not satisfactory, the user may select a new set (options 1 or 2), or quit the process entirely (option 0). When the required set of positions has been found, the new sections can be calculated using option 3. This is the stage where prior data are lost. This facility has two main uses; firstly, making the transition from a few initial sections to a set which can (C) BLUE PETER Marine systems Pty Ltd ------------- page 21 ---------------------------------------- HULLFORM VERSION 3 be used to fair the hull shape as desired, and secondly to obtain highly-accurate estimates of factors such as displacement and wetted surface once a final shape has been accepted. 10. Delete current hull This allows hull data to be discarded from the computer's memory, so that a new hull can be started from scratch. The program responds with a confirmation enquiry: Are you sure? (Y/N): for which a response of "Y" or "y" will result in deletion of all data. (C) BLUE PETER Marine systems Pty Ltd ------------- page 22 ---------------------------------------- HULLFORM VERSION 3 3. Plot hull lines The options available under this section are of two forms: perspective, and geometrical drawing. The screen initially displayed is HULL DRAWING MENU 0. Return to previous menu 1. Perspective view 2. Plan, elevation and end elevation 3. Plan view 4. End elevation 5. Side Elevation Enter option (0-5): Option 1: Perspective view This section allows display of the hull in "wire-frame" form, with calculated waterlines, for any selected heel and pitch. The plotting menu is of initial form Options are: 0. Return to previous menu 1. Select hull azimuth (positive starboard, now .0 deg) 2. Select viewing position: now ( .0,99999.0) giving plot region ( -1.4 : 1.4, -1.3 : .8) 3. Select picture plane inclination (now .0 degrees) 4. Alter heel (positive starboard, now .0 deg) 5. Alter pitch (positive bow-up, now .00 deg) 6. Alter waterline contour interval (now .060 m) 7. Turn a hull line on or off 8. Turn waterline plotting on or off 9. Turn section plotting on or off 10. Plot full hull 11. Plot port half hull 12. Plot starboard half hull Enter selection (0-12): Apart from the standard option 0, these are grouped in four classes: (C) BLUE PETER Marine systems Pty Ltd ------------- page 23 ---------------------------------------- HULLFORM VERSION 3 Orientation Group 1. Select hull azimuth This and 2, below, permit the hull to be oriented whichever way required. Hull azimuth of 0 degrees implies the bow (lowest section number) towards the viewer, with increasing azimuth corresponding to rotation of the bow to starboard. Values should be in the range 0 to 360 degrees. 2. Select viewing position The viewing position is specified with the first (y-) co- ordinate upward, and the second (z-) co-ordinate out of the screen. To prevent overflow of the on-screen display, values are limited within the range -9999 to 99999. Users should note the means used for altering the y- and z- values. For each, a prompt typified by: New y-position, or RETURN: is presented. If no change to the existing value is required, pressing of the RETURN key only is needed. Given any other input, the appropriate change will be made. If a z value within the fore-and-aft extent of the hull is specified, only those sections in front of the viewing position will be plotted. In all cases, the plot is scaled to fit comfortably within the graphics screen. It is possible to generate normal plan, elevation and end elevation views of the hull, by selecting, respectively: - azimuth 90 degrees, large y- and small z- viewing position - azimuth 90 degrees, small y- and large z- viewing position - azimuth 0 degrees, small y- and large z- viewing position Note: when forming a plan view, do not select a zero value for the z-position: you will have no section position behind the viewing point, and see no image. 3. Select picture plane inclination In perspective drawing, the image is projected onto a plane, termed the "picture plane". Conventionally, this is vertical (conceptually, parallel to the graphics surface), and this can generate distortions when viewing angles are large - i.e., large y-position / z-position ratio. To overcome this problem, when the viewing position is changed, the program automatically alters the inclination of the picture plane, so that it remains perpendicular to the line from the viewing position to the hull centre. Option 3 allows the inclination to be changed manually, when distortions are desired. For example, when inspecting (C) BLUE PETER Marine systems Pty Ltd ------------- page 24 ---------------------------------------- HULLFORM VERSION 3 waterlines for a hull, it is normal to use a large y-value, giving a corresponding large inclination of the picture plane. If a low inclination is then forced, using menu item 3, the beam seen on the image will be expanded, enhancing any small discrepancies. Waterline Group: 4. Alter heel 5. Alter pitch This pair allow alteration of the two orientation parameters of the hull. (Note that, for the waterlines to have physical meaning, the hull must be balanced using item 4 of the main menu). The two corresponding prompts are Enter new heel value (-90