MSN Home  |  My MSN  |  Hotmail
Sign in to Windows Live ID Web Search:   
go to MSNGroups 
Free Forum Hosting
 
Important Announcement Important Announcement
The MSN Groups service will close in February 2009. You can move your group to Multiply, MSN’s partner for online groups. Learn More
canoing[email protected] 
  
What's New
  
  WELCOME  
  WELCOME  
  Memorial Day  
  General  
  Message Boards  
  Off site Picture  
  Pictures  
  Outdoor Adventures Chat Room  
  LIFE SAVING TIPS  
  Paddle Strokes  
  Tell us about your self  
  Name Brand Canoes and Kayaks  
  Cooking on the River  
  Recommendations  
  Classsified Ads  
  Canoeing History  
  Canoeing in Your State  
  " Getting Started " Your first canoe  
  Tips For Safer Canoeing and Kayaking  
  Creating a pattern  
  
  canoe and kayak accessories  
  GOT A HOLE IN YOUR CANOE?  
  Choosing a Kayak  
  Links  
  Documents  
  New Folder  
  cartoon of the day  
  STORY SECTION  
  Hunting from a canoe  
  Sand Lake directions  
  Terms for canoes and kayaks  
  Reflections  
  Insect Repelents  
  CANOEING FLORIDA  
  Darren McGinnis Journals  
  day trips U S South east  
  Canoeing 2-3 Day Trips: US Southeast  
  Canoeing Extended Trips: US Southeast  
  North east trips  
  North east page 2  
  Midwest day trips  
  Mid South  
  US West  
  GAMES  
  MEMBERS MAP  
  
  
  Tools  
 
From: J.R. Sloan Sent: 3/30/2003 5:44 PM
One way to take measurements from a hull model to make Mold patterns.

By J.R. Sloan, 29 March, 2003

Definitions: For our purposes, the following words have these meanings.

Hull: the supporting part of the boat that includes the watertight shape below the gunwhales, both above and below the waterline. The part intended to keep you dry.

Model: any representation of a hull the builder wishes to recreate in 3 dimensions. Might be a scaled-down wooden model; another full-sized boat/canoe; any clay, wood, paper, plastic or other stuff can be used to make the desired shape.

Half-hull model: the traditional method of hull modelling uses a "half-hull": the right or left half of the hull shape is sculpted (of wood, typically) to represent the shape of the hull as seen from the side. Only half of the hull's shape is presented. This half starts by selecting a line from the farthest center point forward to the farthest centerpoint aft, and dropping a vertical plane through this line; the part of the hull on the viewer's side of this plane is the half-hull. Half-hull models of actual boats, mounted for display, become enormously expensive in the hands of marine-style interior decorators.
Forms: Forms present convenient graphic shapes of the half hull, at selected distances (typically, in even inches, feet, meters or other convenient measure)along the model. Think of them as "slices" of the half-hull shape, taken at regular intervals.

Mold(s): the structures used in some types of construction that help the builder keep his materials near to the desired final shape. Molds may be integral or removeable, depending on the desired hull capability. Typically, mold shapes are formed by joining a half hull form and its mirror image along the centerline.

That's enough definitions for our purposes.

Purpose: In this discussion, I will describe one way to create Molds for building small boat or other curved shapes, suitable for strip-building, cold-forming, fiberglass mockup, papier-mache' construction, and other hand-built, curved shapes.

Suppose you want to build a boat, so you sit down and sketch out a zillion or so views of the kind of boat you want. You finally settle on a form that looks good to you.

Step One, build or find a model of the boat. If you have access to a plastic model boat you like, or perhaps a half-hull model, this step is easy. Otherwise you may have to apply your creativity. Here are some suggestions:
(1) Try common modelling clay from the craft store. The positives include good plasticity (so it's easy to form), it stays pliable at common temperatures, and it has a (relatively) long life. Drawbacks include fragility (OOOPS! I dropped it!), malleability at higher temperatures (dang!, I dropped my hammer on it), and difficulty in reproduction.
(2) Try Ceramic modelling clay. It's as easily worked, but dries hard in the oven and will hold its shape for infinite reproductions. Kind of heavy, though.
(3) Try Plaster of Paris over paper structures reinforced with chicken wire or similar materials. Light and strong, but fragile.
(4) Try strip-building over paper or cardboard molds, then modify the basic model with trowelled-on clay or plaster.
(5) Carve it out of wood. Start with a 2x4 or bigger, and some rough dimensions pencilled on the blank. Carve off anything that doesn't look like your boat.Step Two, lay out your model's plan. The purpose of this step is to firmly determine from where you will take the meaningful measurements for your hull shape. On a sheet of graph paper, lay out your proposed boat's final length, as viewed from above. Divide it into convenient segments (for example, for a 16' boat draw a 16" line on your paper. You might want segments beginning at the middle and proceeding fore and aft at 2-foot intervals. Draw lines along each of the two-foot marks, perpendicular to the original line. In two dimensions, this represents your forms, the source of your molds. It should look like your dream boat, divided down the middle with crossed lines every two feet.
Now do the same thing with a side view of your boat. Draw a 16" line on your paper, and draw perpendiculars at two-foot intervals, on the side view of your boat, with the boat's keel (bottom) just resting at its lowest point on your 16" line. Your drawing should look like your boat is sitting on a horizontal concrete surface (the baseline), with its stern on one side and bow at the other, and with your intervals marked exactly where you want to take your measurements.

Step Three, set up your model for measurement. In this step, you will take and record actual measurements from your model. You must decide what your measurement accuracy will be, but in practical terms, the choice of 1/4" graph paper (or some other size) will set an approximate standard you can easily modify later. You need now to secure your model so that it won't wiggle out of the way when you measure it. For a solid model, using clay to secure it may work. For a plasticine (clay) model, laying the half-hull on a piece of mirrored glass has proven satisfactory. Using a marker of some sort, transfer the plan lines from Step Two onto your model (across the top and onto the sides of the model). Be sure the Centerline is straight and true (a major advantage of half-hull models).Step Four, prepare to take the measurements. You will need a table to record measurements; printing a blank spreadsheet form might serve you well. The object is to measure your hull at every point where an interval line crosses one of your grid lines on the graph paper. So, if you have nine intervals, you will need at least nine columns

Step Five, take the measurements. Assuming your model is securely anchored (so to speak) to a smooth surface, this is merely tedious, but not hard. You want to take measurements on each interval line that correspond to the (a) height above the baseline (the concrete floor from above) and (b) the distance from the center plane of the boat. These two measurements are expressed in feet, inches and 16ths of inches, so that a point on a mold could be expressed as (0,9,08 / 1,9,05+), meaning: Height = 0 feet, 9 inches, 8/16" above the baseline and 1 foot, 9 inches, 5/16 inches (plus a little) from the centerline at this interval.

How do you do this practically? Not too hard, really. Make a set of 1/4" x 1/4" sticks of wood (balsa, shop scraps, whatever) about 6" in length. Slide them up next to the hull in multiples of height (1/4" measurement is one stick deep, 1/2" is two sticks, and so on). Where they touch the hull, measure the distance from the centerline. [Remember, that on your 1/4" graph paper, each square equals three inches). Record each measurement in your spreadsheet.Step Six, Transfer the measurements to a form pattern (or, now comes the fun part!). Now, get some brown wrapping paper and make some REALLY BIG graph paper. To scale 1" = 1' (like we've been doing), the graph squares have to be 3" square. You will need a separate sheet of this brown graph paper for each form interval (nine in all). Your objective is to transfer all your measurements, so that your center line is a vertical on your graph paper, and each measurement for an interval is a point on the corresponding sheet.
You will probably have six or seven points on each sheet, maybe more. You are only trying to get a series of points that describe one-half of the hull at this interval.

Step Seven, applying artistic license. Because your measurements were taken on such a small scale, you are bound to have errors in your patterns at first. That's OK, because now you get to fix them. You will need a batten (that's fancy nautical talk for "a flexible piece of stuff that will help you draw curves"). Some people use a limber plastic ruler or yardstick; traditionalists use a long piece of skinny ash or other whippy wood. Your objective is to "connect the dots" from the previous step: each graph's points are approximated with the batten, to form as "fair" a curve (a smooth one) as possible. OOOPs, the dots don't quite line up? So move the one that doesn't fit. Keep at it till you have a nice smooth pattern for each interval. Step eight, take out the scissors. Simply cut out your patterns, making absolutely certain that your center lines are all perfectly straight. Cut as closely to the curved lines you made with the batten as possible. You should have 9 separate half-hull patterns (if you used our 16' example), and the foremost and aftmost patterns may have little or no shapes on them.In a canoe, the middle pattern will probably be the widest, but other boats may differ.

Compare the patterns. First, number the patterns. Number "1" is the foremost, number "9" is aftmost, and so on. Your objective here is to "eyeball the patterns" for smooth lines from the center to (first) the bow, then from the center to the aft). Stack the patterns so the widest is on the bottom, and aligning the center lines on each, work forward so the graph lines on each pattern line up. Typically, you will notice slight variations on each interval, which define curves in your hull. Does your plan call for a nice, gradual curve toward the bow? If so, the edges of your plan will be relatively close together until the curve increases. Same principle as profile lines on a map! Main point here: if you see any obvious irregularities, trim the pattern or tape on extra paper and trim it to suit. Follow the same process for the widest-to-aft patterns.

It's time to create full-scale Mold Patterns for the foundation of your boat! Though this sounds complicated, the following is very simple. You will need some tranparent tape and a large smooth surface (I simply taped a large piece of brown graph paper (see step six) to a table, and ran a strip of clear packaging tape down the middle).
(a) Using this centerline as the foundation, tape the centerline of any interval pattern to the sheet, careful to align all graph lines. Use this strip of tape as a hinge, so that you can flip the pattern from its present position to a mirror image, like opening a book,

(b) Cut a clean sheet of brown paper, at least twice the length of the pattern. Fold the sheet in half from top to bottom. Slide this clean sheet under the pattern, so that the folded edge meets with the taped centerline, under the pattern. Try to get the fold to the exact centerline edge of the pattern. Smooth the pattern out over the folded sheet, and trace the outline of the pattern's curve onto the sheet using a soft lead pencil.

(c) Carefully remove the folded sheet. Fold the taped hinge to the mirror image position. Turn over the folded pattern sheet, and insert it so that the folded edge again exactly butts against the tape "hinge". Be sure to line up the marks from the previous step (b) so that tracing the pattern onto this shape is a continuation of the pencil marks.

(d) Remove the folded sheet, and open to full width. Your pencil marks should define the first of your mold patterns. Transfer this pattern to the wood you want to make into the first Mold.