| Model Ship Builder :: Forums :: Modeling Types :: Computer Assisted Drafting (CAD) |
|
<< Previous thread | Next thread >> |
| Columbia Mission Boat | ||
| Go to page 1 2 3 | |
|
Moderators: Winston, aew
|
| Author | Post | ||
| JosephH |
| ||
  Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | First a little info on the Boat will be drawing up: The Columbia III was one of the last in a long line of vessels operated by the Anglican Church’s Columbia Coast Mission. The Mission provided medical, non-sectarian religious and social services to remote settlements, lighthouses, logging camps and First Nations villages along BC’s inside coast from 1905 to the late 1960s. The Columbia Coast Mission saved hundreds of lives when its vessels hastened to logging camp accidents. The mission also provided a cherished social outlet. “It was very exciting when the Columbia came because there was very little entertainment for us,” remarked one of the attendees at the 50th anniversary tea held onboard Columbia III. In those days the Columbia’s staff brought books, showed movies and hosted Christmas pageants, complete with a portly Santa Claus. For those that are interested in building one or wanting to follow along better I have uploaded the drawings to my site which you are free to download at : Columbia Mission Boat Drawings | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | Here are a couple Pictures of the boat   | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | OK so I will be determining a scale and setting up the drawings for cadding up. I will be using SolidWorks for my cad program which I have used for years. The nice thing is it is a great 2D and 3D program so as I go I can virtually build the boat and make sure everything fits perfectly. there are many features to the software which helped tremendously when I designed planes but probably wont be needed here. One item is it will show where the center of gravity is and if I use the correct wood I want to build the model with it will tell me the weight. then there are many different flow dynamics etc in the program which wont be of use here. These drawings show some tables of offsets I need to figure out as they arent the standard ones I am used to reading (have the complete Bath Shipyard Microfilm for a Fletcher Class Destroyer I lofted the Hull up using the 5000 plus offsets on the plans) Here are the Offsets for the Columbia  | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | So I guess will do a little explanation of offset tables for those not familiar with them and how I set them up for my cad program to read them. First is a screenshot of my offsets from my Fletcher  | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | Ok now in my excel sheet I set it up with the stations on the far left. at this point I dont worry about dimensions for the stations just list them as station -1, -2, -3, F.P. 1, 2, 3, etc to A.P. along the top we want to list out waterlines and below each waterline we want to have 3 empty fields to input our values. offsets are shown one of 3 ways ex1: 3-3-3 ex2: 3-3-3+ ex3: 3-3-3- we break down the offsets as follows. the first number is feet in this case 3 feet the second number is inches in this case 3 inches the 3rd number is eighths of an inch in this case 3/8 inch so our first example is 3 ft 3 inches 3/8 inch the next thing you will need to do is to convert everything to decimal inches. For now we just want to enter the 3 numbers into the table later we will create a table where we will list the offsets as a decimal inch. when we do it will be 36"+3"+.375" or 39.375" the next example we have the same thing but this time there is a 3+ on the end. the plus means a fudge over 3/8" for this we use as a rule of thumb 1/2 of an 8th or 1/16". Likewise in ex 3 we see a 3- obviously this means we subtract 1/16th inch. Now when we create our table we dont want to manually convert each one especially with something like the Fletcher or even worse an Iowa class battleship where we could have literally 15000 or more dimensions. so what we want to do is to create a function to automatically convert them for us. The following formula will automatically convert the numbers to decimal inch for us BUT we also want it to check if there is nothing or a + or a - in the 8ths column. So Here is the formula for you already made and checked which works: =B5*12+C5+(LEFT(D5)+IF(LEN(TRIM(D5))<2,0,IF(ISERR(FIND("+",D5)),-0.5,0.5)))*0.125 | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | Ok now disclaimer I didnt write this formula I had asked for help on an excel group. I wrote the original but i didnt know how to have it check for the + or signs so will do my best to explain the formula and break it down for you: =B5*12+C5+(LEFT(D5)+IF(LEN(TRIM(D5))<2,0,IF(ISERR(FIND("+",D5)),-0.5,0.5)))*0.125 = Needed to tell prog it is a formula B5*12 B5 is the location of the cell containing feet so this says multiply the number in b5 by 12 converting it to inches +C5 this says take the next cell C5 which is the inches and add it to the converted feet +(Left(D5) this is saying take the left side of the next cell which is D5 it basically says the number is on left side and the rest of the formula says to check after the number and if nothing is there then multiply it by .125 which converts the 8ths to decimal inches. and if there is a plus add half of an 8th (the 0.5) or if a minus deduct half an 8th. so that is the basics of the formula. now how to adjust it say your 1 ft waterline is at B5 C5 and D5 and your 2 ft waterline is at E5 F5 G5 so you just replace the letter combos in the formula to match noticing there are 3 locations for the 8th of an inch you need to replace. Ex: =B5*12+C5+(LEFT(D5)+IF(LEN(TRIM(D5))<2,0,IF(ISERR(FIND("+",D5)),-0.5,0.5)))*0.125 so you would change it as follows for the second waterline =E5*12+F5+(LEFT(G5)+IF(LEN(TRIM(G5))<2,0,IF(ISERR(FIND("+",G5)),-0.5,0.5)))*0.125 and you repeat it for every waterline for each station this will make everything decimal inches. | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | OK so now what does all this give us to work with. The First thing we get is our table of offsets entered as I showed earlier for each waterline and station. next we converted it to decimal inches. as you can see Here I created another table on the spreadsheet with everything converted  | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | So Next now that we have the offsets converted to decimal inches we want to convert our stations. in this photo you will see the stations (blue) that we listed before remembering I said we just have to list them as 1 2 3 etc Now in the light green the stations are converted properly ex B to a 2 A to a 1 FP to 0 then it starts going negative numbers. the reason for positive and negative here is because solidworks and most cad programs differentiate positive and negative distances from the origin point (you will understand origins later on as i start drawing) the 3rd one in the clear is the stations converted to decimal inches. ok now how did I get the distances is another explain needed. in most current ships (dunno on old timer ships) each station is evenly spaced along the length of the ship. in the fletcher I think it was 200 stations so we take the overall length of the ship and divide it by the number of stations to get the station distance. in this case with the Fletcher it came to 21" apart so for example station 6 would be multiplied by 21" gives us 126" but it is behind the origin point so we make it negative. When Drawing I put the F.P. on the origin point which makes the origin point the 0" mark  | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | Next we make a table for the Waterlines which is simple you multiply the waterline by 12 to give the decimal inches | ||
| Back to top | | ||
| JosephH |
| ||
| Registered Member #4876 Joined: Fri Dec 23 2016, 03:37amPosts: 1442 | and finally we now have all the info we need to make out curve table. A curve table plots an XYZ point and when you put all the waterlines together in a table then the computer plots all the points and draws the line connecting them all. Solidworks only allows you to use u curve station at a time thus you need to save each station as a separate txt file and import each one separately into SolidWorks. with autocad you can use a comma or I believe it is a colon and space to separate each curve file. I know a comma works for sure. BUT it also makes a difference as to what info you put where in the file or you will get goofy results. Autocad is slightly different I believe but not certain. for SolidWorks the first number is the station the second number is the waterline and the 3rd number is the offset data I believe autocad switches the station and waterline around. as you can see from the image each waterline is stacked below each other. it is important to keep the waterlines in the proper order. so once you have the curve table all made in excel you can copy the table and paste it to notebook and save as a text file. in this example the text file would look like this where you have a space between each number set. some have 2 but thats ok: -21 24.000 0.688 -21 36.000 3.438 -21 48.000 4.563 -21 72.000 4.375 -21 96.000 3.688 -21 120.000 3.375 -21 149.400 3.438 -21 168.000 3.625 -21 180.000 3.938 -21 192.000 4.438 -21 210.000 5.438 -21 240.000 7.938 -21 264.000 10.688 -21 288.000 14.938 -21 312.000 20.688 -21 336.000 28.125 -21 360.000 37.063 -21 382.313 46.375  | ||
| Back to top | | ||
| Go to page 1 2 3 | |
Powered by e107 Forum System