Internal Frame Wall Tent; Getting the Size Right and Planning for Shrinkage

If you have or are considering an angle kit for an internal frame for you wall tent, determining the number of Legs, Ridges, Side Supports and Rafters is fairly simple, but if you have more than a few rafters, the total number of pieces starts to add up fast.

How Many Legs, Ridge, Side Supports and Rafters Does your Wall Tent Need?

Figure 1. Top and Side Section of Internal Frame, showing location of 3-way and 4-way Angles, Ridge Supports, Rafters and Side Supports.

• Legs – Each rafter section needs two Legs
• Rafters – Each rafter section needs two rafters (connects top of wall to ridge)
• Ridge Sections – Total rafter sections minus one is the number of ridge sections (Ridge Sections connect one rafter section to the next)
• Side Supports – Total rafter sections minus one, then multiply times two for the number of side supports (Sides  supports connect one rafter section to the next at the top of each wall)

The total numbers of each Support; Leg and Rafter, Ridge Section and Side Support can also be seen in Table 1. for any number of rafters between three and 17.
Table 1. Number of Angle Pieces and Rafter Sections needed for Various numbers of Rafters for Internal Wall Tent Frames.

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How to Determine Length for each Support Section

There may be many sections, but luckily, the ridge sections and the side supports will be the same length, so there are just three lengths to measure and cut:

• Legs – Most wall tents are very near five feet high (60 inches) on the sides, so the legs need to be the same length, but measure to be sure of the exact height.
• Roof Ridge & Side Supports – These are the same distances as calculated in Table 1 of a previous post. But can be easily calculated; The length of these supports depends on the length of your tent and the number of rafter sections and equals the Total Length of Tent – (Number of rafters – one).
• Rafters – This will vary depending upon the width and total height of your tent. Most wall tents are 5 feet high at the wall and 8 feet high at the ridge, so Measure to get the exact length from ridge pole to top of the wall. Do not measure any overhanging fabric on the outside.

So as example, for my 12 x 14 foot wall tent (not considering shrinkage), I would cut support poles as follows:

• Legs – 60 inches – minus one inch for the single angle connector = 59 inches
• Roof Ridge & Side Supports -56 inches – minus two inches for the two angle connectors = 54 inches
• Rafters – 80½ inches – minus two inches for the two angle connectors = 78½ inches

Estimating Canvas Shrinkage

As I mentioned in an earlier post, I was instructed to cut all the poles for my internal frame for three percent shrinkage, but so far the tent has not shrunk that much, so for a better fitting frame, I recommend only cutting poles for one percent shrinkage. If the tent shrinks more than that, you can cut more off the poles later if needed. Not necessarily an easy task, but I think it’s better not to have a saggy tent.

So, in my case, to cut poles and allow for one percent canvas shrinkage:

• Legs – 1% of 60 inches is 0.6 inches, so 60-0.6 = 59.4 inches – minus one inch for the angle = 58.4 inches (or to nearest 16th as 58 3/8)
• Roof Ridge & Side Supports -1% of 56 inches is 0.56 inches , so 56-0.56 = 55.44 inches – minus two inches for the angles = 53.44 inches (or 53 7/16)
• Rafters – 1% of 80.5 inches is 0.805 inches, so 80.5 -0.805 = 79.695 inches – minus two inches for the angles = 77.695 inches (or 77 11/16).

No Need to Estimate Shrinkage for Polyester Wall Tents

Our latest wall tent was made by Elk Mountain Tents of Nampa Idaho. Their tents are made of polyester and do not shrink, so there is no need to account for shrinkage. Check them out, I think you will be impressed by the quality, the features and by the price.

See Table 2 for additional shrinkage calculations for rafters of various sized wall tents.

Table 2. Typical Rafter Lengths for 10, 12, 14, 16 and 18 foot wide Wall Tents (Assumes Tent Height is 8 feet and Wall Height is 5 feet).

Like all construction projects, if you cut too little, you can always cut it again, but if you cut too much the first time you have to live with the mistake or start over.

Marking the Angles and EMT Sections for Quick Assembly

Figure 1. Connector Angles and Poles of the Internal Frame were Marked for Quick Assembly

One last thing to make your life easier. After cutting all the EMT tubing for your internal wall tent frame, assemble all the parts. If your frame is like mine, some sections will fit together better than others. Once the frame is assembled, take a minute and mark the sections (Figure 1) so they are faster to assemble.

I keep a “cheat sheet” of my code (Figure 2) in the bag with the angles to help me remember how everything fits together. Even if you forget your cheat sheet, because all colors go together and all symbols go together, everything fits together faster than if you used no system at all.

Each pole and angle was painted the same color where they connect, then a symbol was painted on top of the color to represent different rafter groups. The code shows how the angles should be laid out as if in three rows and four columns and show how the support poles fit in between and connect all the angles:

Three Rows (Ridge and two sides)

Figure 2. My code for attaching internal wall tent frame sections.

• Blue color represent the blue sky, which is the ridge poles, their associated angles and the upper ends of the rafters that attatch to the ridge.
• Black is on one side of the tent frame and includes the side poles, the angles and the lower end of the rafters that attach tothe wall. The legs are also attached to the 4-way angle.
• White is on the other side of the tent frame and attached just as on the black side

Four Columns for Four Rafters

• The “D” marks are on all the pieces that make up and attach to the rafter nearest the door; 3-3-way angles, 2-legs, 2-wall supports, 2-rafters and one ridge pole section
• The “X” marks are on the next rafter section inside the door; 3-4-way angles, 2-legs, 4-wall supports, 2-rafters and 2-ridge pole sections
• The “O” marks are on the internal rafter section near the back; 3-4-way angles, 2-legs, 4-wall supports, 2-rafters and 2-ridge pole sections
• The “E” marks are on the back (End) rafter section; 3-3-way angles, 2-legs, 2-wall supports, 2-rafters and one ridge pole section

Use any color or marks you wish, just be careful that the marks are clear enough not to be confused with other marks. It’s not as easy as you think to write with a paint brush without practice, a couple of my D’s and O’s look very similar.