Using Excel Graphs to
Loft Fair Curves
After looking for several months on the internet and trying various CAD programs, I had failed to come up with a simple way to lay out the lines for my fishing vessel to check the fairness of the design. My building technique involved setting molds on a strongback, and laying plywood over the molds, FRP (Fiber Reinforced Plastic) on the plywood, then popping the hull off the molds, and FRP (Fiber Reinforced Plastic) inside the hull on the plywood for a composite FRP (Fiber Reinforced Plastic) Plywood hull. My FRP consisted of stitched biaxial cloth and cold cure, 17 oz below the waterline, and 12 oz above. My design ideas came from the FAO Fishing website using the 7.4 M hull there, taking the widest frame, and coming straight back to the transom with the keel and chine for a planing hull. However I still needed more stability and lift so I had to modify the hard chine vee to lay on ski's hence the search for a CAD program that would allow me to lay in my own lines and check for fairness. Applying the formula for when all else fails, return to simplicity brought me to try excel graphs. The example below is just that, an example. To get a better idea of what the lines will look like you will need to add columns for every 12 inches of hull or so and then, if the molds are on 36 inches, only use every 3rd one
I use 0 for the Baseline and Centerline and measure in cm
columns for the molds starting from the stern as below,
I found you can then highlight the measurements themselves, as such;
then click Insert/Chart
Select "Line" for type, and highlight "Line with markers" exactly as below
click next then make sure you select "Rows"
click next and give it a title
click next and make sure "As new sheet:" is selected
You then have a
graphical representation of your lines for a hard chine boat.
Another neat trick is
to use excel to make a scale model.
Then do the same for each column,
and you will have all
the measurements you need to build,