| Model Ship Builder :: Forums :: Modeling Types :: Computer Assisted Drafting (CAD) |
|
<< Previous thread | Next thread >> |
| USF Essex POF CAD Plans | ||
| Go to page 1 2 3 4 5 | |
|
Moderators: Winston, aew, Donnie, bikepunk
|
| Author | Post | ||
| Gary M |
| ||
 Registered Member #4198 Joined: Tue May 07 2013, 10:50pmPosts: 908 | Step 9: Additional Water Lines: Goal: To understand the function of Water Lines and lay them out for future frame lofting. UPDATED Jan 25, 2014: While not a perfect strategy, additional waterlines can be of use when lofting frames. However, I found that the below strategy did not work on the Essex. I think this is in part due to the plans being a little off as well as the fact that the waterlines are not always evenly spaced apart. I will leave this post in place since the below method worked on the Eagle and Peacock. The Water Lines are a series of strategically placed lines that are shown as curves on the half-breadth plan, and are horizontal lines on the sheer plan. The Water Lines, not to be confused with the Load Water Line, transect the hull on a horizontal plan in slices and reveal the shape of the hull. These are our primary source of information when we get to lofting the frames.  essex_added_wls_examples.pdfAs you will see in the below image, I added three additional waterlines to the half-breadth plan. They are 1.5. 2.5, and 3.5. I simply placed a line halfway between the already defined waterlines. These will come in handy especially around the buttocks and forward part of the ship where the curves are more pronounced. At a later stage, we will make a grid which will be used in the actual frame lofting.  The below image is the Sheer and Half-Breadth in semi-final form. It’s important to resist the temptation to start working on frames or other sidebar drawings at this stage. I recommend that you load as much information onto the Sheer and Half-Breadth plans and once finalized, then and only then should you start moving items to other plans. I will selectively delete items from this master plan once complete for better viewing. I plan to break-out the stern, keel, stem details into a separate plan for template use. I learned this the hard way. On my last ship, I made the mistake of skipping around when developing the plans and as a result, when I made a change in one place, I had to go back and fair the plans in other places. I was wasting a lot of time, just chasing my tail... As I state, Its best to stay with a “Master” plan, fully develop it and then once you are fully satisfied with it, then branch out. essex_sheer_example.pdf [ Edited Tue Nov 25 2014, 09:35pm ] | ||
| Back to top | | ||
| Gary M |
| ||
| Registered Member #4198 Joined: Tue May 07 2013, 10:50pmPosts: 908 | Step 10: Midship Bend: Goal: To understand the importance of Midship Bend, dead flat area and their relationship to other parts of the ship. As discussed earlier in this narrative, the accuracy and location of the midship bend is essential for both the development of plans and the sailing qualities of the ship. The midship bend also provides us with our inside dimension for the frames. So, its important to get this right. Failure here is failure everywhere… The bend will be widest towards the keel and will increase as you move toward the top timber. My top timber is 5” wide. The thickness of all the frames will stay consistent fore and aft, based on this frame. This subject will be explained further when we go to lofting. There should be a “dead flat” area located between the lower and upper heights of breadth. These were not pronounced in the drawings in the book, so I am thinking that they are more theoretical at this scale. That being said, take care with the spline tool not to round off this area of the frame. When splining, I placed a point at the lower and upper breadths (maximum beam at these areas) to reduce the spline rounding affect. I think it important to make sure that the dead flat area is “flatter” than the areas above and below it. You can get a real feel for the dead flat area by looking at the Body Plan on page 34. On this plan, there are two perpendicular lines framing the Body that represent this dead flat area. PDF's for clearer viewing=> essex_midship_frame_example.pdf midship_frame_example_with_pull_over_lines.pdf1. Copy and import the Midship Bend found on page 54 of AOTS. Do adjustments as we have done in the past to the imported drawings. You should be getting really good at this by now… 2. Place the imported copy just to the right of Sheer Plan and level it with the base of the keel. Pull essential lines across from your “Master” Sheer to the imported drawing and over the top of it. You may note that CAD will not show the lines on top of the drawing because of a layer priority feature. If this is the case, simply go to =>edit and look for the “Z” with a downward arrow. Click on this, and then your drawing. It will make it the inferior layer. 3. Scale drawing so the false keel = 5”, Keel = 16”, etc. It’s essential that you final measurement for the Sheer (in my case, distance from bottom of keel to top timber at midships) is exactly the same for each drawing. The same holds true for the breadth at midship on your Half Breadth plan. Remember that your Sheer and Half-Breadth are your “master” drawings at this stage - All measurements must be reconcile here. 4. Trace drawing. I then pulled the LWL, Sheer, Main Wale, etc over to the Midship plan to ensure they were accurate. I fine-tuned as needed (See Drawings below). Most lines were dead on, while others needed a fine tuning of about 1/64th an inch. For modeling purposes, it was close enough, but I wanted them to be exact. Keen eyed observers will note a slight irregularity at the rabbet. I need to adjust the drawing slightly in this area, but will wait until the next step. It’s important to note that this drawing is a demo – while good enough for modeling, I think it still needs to be faired with the other plans. I need to do an actual lofting of the midship frame from the plans and will then make any final minor adjustments to the shape of the midship bend. Once the midship bend is faired, we will have the start of a Body Plan. While not essential for lofting, I will make one once the frames are all lofted. It’s just a matter of copying the station frames onto a single grid. The next step will be to create a lofting grid, loft the midship frame, fine tune the midship frame and then finally loft the square frames. Below are the fruits of my labor.   | ||
| Back to top | | ||
| Gary M |
| ||
| Registered Member #4198 Joined: Tue May 07 2013, 10:50pmPosts: 908 | Step 11: Rising Wood Frame Floor and Keelson Dimensions: We need to extrapolate these dimensions because the plans are a bit off and didn’t correspond well to my CAD drawings. I therefore went “off-road” and made a few well calculated assumptions. Here is what we know: 1. The Rising Wood is 4” moulded at the midship bend. 2. The Keelson is 14” square along the length of the square frames. 3. The Frame Floors will be 12” for all square frames. 4. Knowing this information, I created the below drawing. You will note the Frame Floor is inside the two blue parallel lines. Now that we have these items laid out, it’s important to note the dimensions, since each of these will be used in lofting the actual frames. 11_frame_floor_and_rising_wood_with_dimensions.pdf | ||
| Back to top | | ||
| Gary M |
| ||
| Registered Member #4198 Joined: Tue May 07 2013, 10:50pmPosts: 908 | Step 12: Creating a Framing Template: Goal: To create the framing template in preparation for lofting frames. As part of the creation of a framing template, we will need to mark the height of the waterlines and then carry them across horizontally to our Midship Bend drawing. This drawing will be the basis of our template. The WL’s are shown as curved lines in the Half-Breadth and as straight horizontal lines on the Sheer plan. They are numbered 1-4 starting with the line closest to the keel. Lines 1-3 are 52” apart, with the first line measured up from the base of the keel. The fourth line is 68” from the third line, or 224” from the base of the keel. 1. Draw the WL’s as described above, pulling them across to your Midship drawing. 2. Copy drawing and move to another location on your CAD platform. 3. Delete all irrelevant lines. Our goal here is to make a blank template that we will copy and paste multiple times in the creation of individual frames. Below is the information I retained for the template. Note that I left the keel items as well as the keelson. The rising wood and keelson will move up as we progress fore and aft. The frame lines will fit snugly next to the top of the rabbet and bottom of the keelson. 1_essex_framing_template.pdf | ||
| Back to top | | ||
| Gary M |
| ||
| Registered Member #4198 Joined: Tue May 07 2013, 10:50pmPosts: 908 | Step 13: Lofting Frames Using CAD: Finally, we are to the frame lofting stage. Please note, this is not a detailed primer on lofting. Gene Bodnar has already covered that topic exceedingly well in his practicum on the Eagle, found on MSB. Please make sure you are familiar with that text before proceeding. I follow Gene’s methods very closely using CAD. The limitations of CAD – While I have found that computer lofting provides greater accuracy than doing it by hand, it still takes considerable time and brain energy to loft frames. There is no magic program here, just old fashion knowledge incorporated into new technology. That being said, let’s begin… I like to start with the Midship Frame. I found that despite my following the original plans exactly, the fact remained that they were not even close to being accurate. While I scaled them to be exact matches, they just would not line up. My original plan of attack was to use the Water Lines found on the original plans to loft the ships frames, but after considerable time and energy in trying to fair them, they were all but fair... I changed course and decided to use the body plan as my guide. I found it to be more accurate that the WL’s on the half-breadth. 1. Start by tracing and smoothing all the station lines on the Body Plan. 2. Starting with the midship station line, I then copied and moved each line over to its own template, doing so, one by one. In addition to the body line, I copied the two corners of the keel as a location guide when pasting the frames onto the individual plans. 3. Do any gentle smoothing, but don’t alter the location of the lines. 4. Here is the Body Plan in progress.  5. Now that the first station line is placed on your grid, Go to your Master Sheer Plan and measure the sheer (Bottom of Keel to top of Timber head) for the MS frame. I show it below as being 331 inches. Remember, the only plans that matter now are the ones you have created. All lines and measurements must match these. Adjust the length of your MS frame to match this measurement. Below is the measurement taken for the MS frame. Note, that I measured from the base of the keel to the top of the timberhead (sheer line). 11_ms_frame_length.pdf 6. Next, note that each Timber head will be 5” wide at the sheer, so draw a parallel line across the top of the timber head that is exactly 5”. This identifies the location of your inside frame. 7. Once you are satisfied with the frame half, use the book match feature and create the other side of the frame. Here is what your drawing should look like now.  8. The next steps is to draw the inside dimensions of the frame using the spline tool. To do this, I eyeballed the original drawing of the midship frame and started splining away. There should be a smooth taper which is thickest at the bottom of the frame until you reach the top timber. Fine tune the drawing until you think you got it right. Take extra care here, since this drawing will be the foundation of all future drawings.  It’s important to note a few things on the above drawing: 1. The smooth gradual taper of the frame. 2. The top timber width at 5” 3. The base of the frame sits snuggly up against the rabbet line. 4. In most cases, the inside frame line frame will come in just at the keelson. 5. Note the tumblehome. It’s important to keep this consistent from frame to frame. It will gradually taper off as you move fore and aft. 11_frame_floor_and_rising_wood_with_dimensions.pdf | ||
| Back to top | | ||
| Raymond Deliz |
| ||
  Registered Member #4329 Joined: Thu Dec 12 2013, 06:21pmPosts: 382 | Hey Gary, I just went over your latest update and it is truly amazing at what you've been able to accomplish. Everything is starting to look as if all pieces should fall into place with little difficulty. Can't wait for the next edition. Ray | ||
| Back to top | | ||
| Gene Bodnar |
| ||
 Registered Member #126 Joined: Tue Jul 21 2009, 11:20amPosts: 1782 | Gary, Outstanding work here. You should consider writing and marketing a book on the subject. Gene | ||
| Back to top | | ||
| Gary M |
| ||
| Registered Member #4198 Joined: Tue May 07 2013, 10:50pmPosts: 908 | Hi Gene and Ray, thanks for the kudos and for your encouragement. The Essex has been a challenge from the start. gene, do you recall any frustrations when you lofted the frames for your build? I think one of the curses of CAD is that the lines are so exact, that you can drive yourself crazy if you are jus a few inches off. On paper, this would be a fudge factor, but in CAD, you really try to get it exact. For model building, a few inches is just a 16th or 32nd, which really equates to a few brisk swipes with a sanding stick. This all being said, it's truly been a fulfilling learning experience. Happy TG! G | ||
| Back to top | | ||
| Gene Bodnar |
| ||
| Registered Member #126 Joined: Tue Jul 21 2009, 11:20amPosts: 1782 | Gary, I have NEVER EVER found a perfect set of plans from which to loft frames. There are ALWAYS lines that are "off" ever so slightly, sometimes blatantly. But you certainly have the right idea in using research and logic to make the necessary "adjustments" and corrections. Your explanations for making these changes are clearly supported by the logic you describe in your narratives. And this is why you should write a book on the subject. Gene | ||
| Back to top | | ||
| Raymond Deliz |
| ||
| Registered Member #4329 Joined: Thu Dec 12 2013, 06:21pmPosts: 382 | Hey Gary, I would have to agree with Gene as to the way you are going about your explanations with using CAD for lofting frames. I really believe if you do publish a book on the matter, you'd get a lot of people buying it. Food for thought Buddy. Ray | ||
| Back to top | | ||
| Go to page 1 2 3 4 5 | |
Powered by e107 Forum System