Editor's Note: There are four articles in this series.
|Cost (US$)||Weight (oz)||Time to construct (hours)||Skill (scale 1-10)||Tools (scale 1-10)|
|$140*||9.6 total||One long weekend||6||7**|
|*Depends on sourcing of materials.|
|**Tools include a hobbyist level sewing machine.|
The challenge came when Backpacking Light Publisher, Ryan Jordan, sent me 5 yards of spinnaker fabric with instructions to 'see what I could do with it.' Since we have already converted a down sleeping bag into a SuperUltraLight top bag, constructing a SUL pack and tarp will complete the "Big Three." In this article, the first in a series of four, I go over the technique used to efficiently allocate the 5 yards of spinnaker with very little waste so that a pack and tarp can be made, and there is even enough material left over for a stuff sack. Other than the single piece of spinnaker (54 inches wide), the only other supplies required are a few notions - which is what small sewing supplies like buttons, needles and thread are called in the sewing world - and a small piece of heavier fabric to reinforce the pack's backpanel. Part 1 of this series includes the materials list for each of the components; the construction of the SUL tarp, pack, and stuff sack will each be covered in the subsequent articles. The finished weights of the masterpieces you'll be creating are: pack - 3.1 ounces, tarp - 6.3 ounces, and stuff sack - 0.2 ounces.
The following design elements are based on my experience and technique when traveling in the backcountry. You may need to adjust the design to fit your own backpacking style. We’ll begin with the rationale behind my designs, discuss how I decided to cut the fabric, and finish with transferring the designs, cutting out fabric, and a project organization technique.
Having spent a lot of time underneath various tarps, my preference is for a little more coverage so I can leave the bivy at home when the forecast is less daunting. For my SUL kit, this makes a lot of sense, because the extra coverage in my canopy weighs less than the lightest of bivies. But with only 5 yards of fabric to work with, I couldn’t get the coverage by making the tarp larger. I decided on making it as wide as the fabric would allow with the ends protected by overhangs. In the following CAD (computer aided design) drawing, I drew my SUL design in BLACK and my old 6’ x 9’ tarp in PURPLE. The diagonal lines are drawn at 45° to approximate a driving rain. Note that I have the SUL tarp pitched higher in this illustration and it still provides much greater protection.
Front and profile sketches of my 6' x 9' silnylon tarp (in purple) and the design of the new SUL spinnaker tarp (black). Note that the SUL tarp is pitched with more head room, and still provides better weather protection thanks to the protected ends and greater width. For comparison, my old silnylon tarp weighs over 8 ounces, while the SUL tarp weighs only 6.3 ounces.
I decided to add a catenary curve to the ridgeline of the SUL tarp. Catenary curves are a culmination of complex mathematics that are difficult to do without good CAD software, so I cheated a bit by tracing the catenary ridgeline curve off my other tarp. Previously, I had copied the catenary curves from my Dana Nuk Tuk pyramid onto silnylon for my ultralight family tent with excellent results. The use of a catenary curve for the tarp left more fabric for the other smaller pieces in this project. I took advantage of this by extending the size of the foot-end overhang and increasing the width of the stuff sack and the pack’s side panel pocket. If you don’t have a tarp with a catenary ridgeline, try to borrow a friend’s - the payoff is worth the effort. (For more information, see Catenary Curvature as an Element of Ultralight Tarp Design.)
The finished 6.3 ounce tarp, with protected ends and catenary ridgeline.
Pockets can add a lot of weight. You might think of it like this: in each place that the fabric is doubled, like the pockets and reinforcements, the weight is at least doubled in that location. Most mesh fabrics are heavier than you might expect - heavier than most ultralight fabrics. I also like a fairly simple pack. For these reasons, I like to pare away all unnecessary pockets. The favored large back pocket adds a lot of weight. Typically, I don’t use a large back pocket, preferring to keep most of my gear on the inside. Perhaps I’m comforted knowing all my tools for survival are tucked safely within. I do like a single small water bottle pocket, located low on one of the side panels, and a place to store wet gear. Wet gear, particularly tarp and ground sheet, are easily secured with a small piece of shock cord. In my design, I integrated the shock cord with the top compression strap to handle all compression for the pack and exterior contents with a single pull of the top compression strap.
The finished 3.1-ounce, 1700 cubic inch (plus exterior storage) SUL pack.
The stuff sack is a simple design made with left over materials and turns out to be just the right size to hold the tarp or serve as a large ditty bag.
The SUL stuff sack is small, but sized right to contain the previously shown tarp, and adds a scant 0.2 ounces.
Make Your Own Pattern
I use a CAD program to position the pattern onto a virtual piece of fabric. This allows me to move and rotate the various pieces to find the best fit and minimize waste. It’s like putting together a jigsaw puzzle, only you have the option to resize the pieces if necessary to make things fit. Usually, this method is used to determine the minimum amount of fabric I need to purchase. However, in the case of this article, I was given 5 yards of fabric, so my goal was to get as much out of it as I could.
Use a CAD program to position your pattern pieces onto a virtual fabric like a jigsaw puzzle. This is the best way to ensure minimal waste. The photograph shows the minimal amount of unused material from the original 5 yard piece of spinnaker.
The CAD image below shows the pattern pieces. The pieces are color coded to indicate the project they belong to. The size of each piece is listed below the figure. The sizes will also be described in the text of each of the articles to come. However, you might want to download CAD software and my SUL Pattern CAD drawing so you can measure individual pieces using the CAD software's measuring tool. Note that you’ll need to download the file and view it in a CAD program. For a free CAD program, I recommend CADstd lite. Use the import function to load the SUL Pattern CAD .dxf file. You could also use my CAD drawing as a starting point for creating your own design.
- Main tarp body (54”-33”x78”)
- Front tarp overhangs (24”x54”)
- Rear tarp overhangs (8”x30”)
- Tarp reinforcements (5”x5”)
- Pack front panel (30”x11”)
- Pack side panels (30”x6”)
- Pack shoulder straps (3.5”x16”)
- Pack backpanel (2 pieces; 10”x11” and 27”x11”)
- Pack side panel pocket (8”x7”)
- Stuff sack (11”x14”)
|spinnaker||5 yards (54 inches wide)||Tarp, pack, stuff sack|
|1.9 ounce urethane coated ripstop nylon||0.5 yards (60 inches wide)||Pack backpanel|
|watch band clip (center release buckle)||one||Pack top closure|
|3/4 inch ladder locks||two||Pack shoulder straps|
|3/4 inch micro cord locks||three||Pack, stuff sack|
|3/4 inch nylon webbing||1 yard||Pack shoulder straps|
|1/4 inch thick closed cell foam||3 inches x 36 inches||Pack shoulder straps|
|3/4 inch grosgrain||3 yards||Tarp, pack|
|shock cord||2 yards||Pack|
|1/4 inch nylon webbing||1 foot||Tarp|
|Aircore 1 Spectra cord||30 feet||Tarp, pack, stuff sack|
|white Gutermann thread||1 spool (274 yard)||Tarp, pack, stuff sack|
|black Gutermann thread||1 spool (274 yard)||Pack|
Transferring the Pattern
Before working with the fabric, start by trimming the ends straight. You will find that lightweight fabrics, such as spinnaker or silnylon, are not woven straight to begin with. The ripstop lines won’t be perfectly perpendicular and square with the edges. Since the number of threads are the same between grids, I assume the ripstop grids really are straight and cut along those lines, which makes cutting much, much easier.
I use the straight lines of the ripstop grid to help cut the ends straight.
Do not cut out individual pieces before drawing the entire pattern onto the fabric. This will help avoid mistakes. I used a black grease pencil to draw my pattern onto the fabric by measuring each piece using the CAD software's measuring tool first. Cut the fabric using sharp sewing scissors, as dull scissors can easily fray the cutting edge, making sewing difficult. As I cut each piece, I place it into a grocery bag, with all necessary notions, and mark the side of the bag to indicate the project within. This helps to keep each project organized, with each piece and notion accounted for. This reduces mistakes like mixing pieces from two different projects, or not having enough pieces or notions.
After creating the design in a CAD program, I transfer the measurements onto the fabric using a black or white grease pencil. I wait to cut the fabric until my entire pattern is added, and every piece is accounted for.
For the SUL tarp, I copied the catenary curved ridgeline from another tarp I own. If you don’t own a tarp with a catenary curve, or can’t borrow one, a straight ridgeline will work nearly as well.
|When cutting fabric for several projects, I like to place each projects’ pieces and notions into separate plastic bags as I work. This helps to keep things organized, which reduces errors.|
This SUL kit works very well for my style of backpacking. I encourage you to alter these design elements in any way that will better suit your needs. Adding a large back pocket, for example, would be an easy modification. Just follow the instructions for adding a side panel pocket, which will be published later in this series.
Now that everything is cut out, we’re ready to begin sewing. The next three articles in this series will show how to sew these pieces together to create a superultralight tarp, backpack, and stuff sack.