12 spoke Medieval center pole pavilion
Index:
Section 1 – Design
Section 2 – Frame
Section 3 – Fabric Measurements and patterns
Section 4 - Optional
Section 5 – Setup and teardown
Closing
Instructional documentation compiled and researched
By: Lady Christiana Elizabeth Constable of ye Phasiani lacus Manerium
Email; pheasant01@yahoo.com
Section 1 Design – medieval single pole 12 spoke
The designing of this tent begun some two years ago when I seen the first one of these in detail and setup. With permission from the owners of this tent I had taken photos of key elements of this style of tent, but with my economic situation of 2008 could not start the construction of this style of tent, and besides the star pavilion was still in good shape. It was in the May of 2008 when Lady Christiana seen a medieval center pole 8-spoke tent and later the 12 spoke design in October of 2009. After seeing the tent up close I started to surf the web, but the only information at the time that was available for free including the calculations and material list was for an eight spoke design medieval pavilion. To small for my likes I put the design aside but did not forget about it. The 12 spoke design is available online for no charge, from Lady Christiana’s web site on tent construction and I Lady Christiana other than the calculations and formulas will not cover the 8 spoke tent.
Lets begin: There is two ways to calculate the fabric and the framework. One of these methods is by mathematics and trig, and the easy way is simply draw it to scale. In my calculations I used both methods to determine materials required for the pavilion. Note that most canvas is 60 inches wide, and it is advisable not to exceed the 20 ft diameter at the base, as this is the max. Size before adding seams in the middle of the fabric panel. REDUCE the number of seams, reduces the number of leaks that can result, and stress on the panels from weight and wind. Also do not cut the fabric out at this time until the frame is made. Once the frame is made assemble the top portion of the tent frame consisting of the tinker toy, the spokes and the upper center pole.
Roof calculations and design
Step 1) The tinker toy and center upper pole - I will be instructing about the 20-foot diameter tent within this article. The first will be the designing of the tinker toy, which is the heart of this design. It is such a simple design for setting up the tent. The roof design is simple to determine, as we will take the number of spokes divided in 360 degrees. This will determine the angle required for the tinker toy and the base, which is 30 degrees for the 12 spoke. The more spokes the less the angle, the fewer spokes more the angle. Please keep in mind that if you are on the base line (spoke) and it is 7 ft radius – diameter at eve of tent will be 14 feet at the eve line, the upright which intersects the tinker toy, less insert length should be 7 ft. +. This will work out to be very near 45 degrees in reality as there made be variations in the setup of the pavilion.
Step 2) Spokes and determine segments - First we must determine what width on materials at required. We will deal with 2 segments of the circle; the eve line, which will be known as base of the triangle known as (Bi) and the base segment line at the base of the tent to be known as (Bb). Lets begin with 3.14 x the diameter divided by 12 spokes, to determine the width for both the eve line and the base line. 173.5 inches x 3.14 = 544.79 inches divide by 12 spokes = 45.40 which is 3 ft 9 7/16 inches for (Bi) overall measurement (segment line of eve). The same calculations will be used for the base circumference. This is part of the circumference and later when the frame is set up we will take the actual measurements from spoke to spoke (segment line Bi) to determine width to be for transfer to the fabric pattern. See pattern and fabric instructions for more detail. This is an approx. measurement of the base, but please keep in mind that (Bi) measurement is not the final figure portion of (Bi) measurement and is in fact 1/12 of the circumference. We need the segment measurement to work and this will be determine in the setup of the frame for final measurements.
To determine Ci we will need the spoke diameter, which will become the base (Bs) of and the vertical height (As) of the upper center pole from the tinker toy to the top of the upper center pole. With the formula of Bs 2 + As 2 = Ci 2; take the roof of Ci. Example (As) = 85 inches and (Bs) = 86.75 inches. Therefore (Ci) will equal 121.45 inches or roughly 10 ft 1 ½ inches.
Now we must take the eve segment measurement of 45.5 inches and divide by 2 which = 22.75 inches. This measurement will become (Bi). We now have (Ci) derived from above and with the same formula we now would use Bi 2 – Ci 2 = Ai 2; take the root of (Ai) to determine length of fabric needed. More will be cover in the fabric section. When calculated Ai = 88 inches approx.
Draw a line to represent (Bi) eve segment and insert a vertical at center point of (Bi); this will be (Ai) than draw line (Ci). This should be drawn to scale and also full size, as this will have the correct angles for the roof panel when it comes to cutting out the pattern.
Using a tape measure from the center point at top of pole down to the outer point of the spoke verify the measurements. This will be known as (Ci). Verify the measurement of the segment for the eve at this time by spreading the spokes out in an equal measurement from the hub. They should closely be to the measurement derived in dividing the circumference by number spokes. In this case actual measurement of (Bi) is 45.25 inches. The segment measurement should be smaller than 1/12 of the circumference (12 spoke design).
Wall panel calculations and design
Now that we have determined the isosceles triangular roof fabric panels, it is now time to determine the wall panels. This is relatively simple as we subtract the difference from the roof eve radius measurement and the base (ground) radius measurements. Our radius eve measurement is 7 ft and our ground measurement is 10 feet leaving the difference of 3 feet. This will be our base line known as (BB). We will also need the height of the pavilion living area or what will be known as the lower center pole (AA) again we will use the measurements of the actual tent been (BB) = 3 ft (36inches) and (AA) = 6ft 6 inches (78 inches). BB 2 + AA 2 = CC 2; take the root of CC 2 and transfer to (Ab); Ab been the length of fabric for the wall panel. (CC) also known as (Ab) will equal 85.91 inches.
Take the base Circumference and divide by number of panels to derive the length require for the base of the trapezoid. 20ft x pie divided by 12 panels = 5.23 feet. Also take the eve line segment measurement than subtract the eve segment from the base segment. The difference is to be divided by 2 of which will make the measurement of (Bb). Base measurement 62 ¾ inches - eve measurement segment 45.5 inches = 17 ¼ inches. We will divide this by 2 which will be 8 1/8 inches been (Bb measurement. We now have (Ab) = 85.91 inches and (Bb) = 8.125 inches which will give us (Cb)
The formula again is Ab 2 + Bb 2 = Cb 2; take the root of Cb.
Draw the segment line base of 62 ¾ inches and a vertical line through the center of the 62-¾ inch segment line. Draw a perpendicular line to the length of fabric (Ab). At top draw a horizontal line parallel to the base segment line. The Eve (Bi) is to be divided in half. If done correctly you should come out with a trapezoid.
Using the height of 78 inches from ground to eve, and using the differences of eve and ground radius of 36 inches we will be left with a tight measurement of 85 7/8 inches. Again we will divide the base lateral perimeter and eve perimeter measurement to determine the centerline of the wall panel. In this example we divide 44 inches by 2 and the base measurement of 62 inches by 2 leaving us with 2 parallel lines – top one been 22 inches and the base 31 inches. We now connect the top parallel lines to form the outside edge of the panel. The base and eve line must start at a perpendicular line right angle to each base and eve line. Mirror the other side and you should have two sloping lines that if continue from the eve line would eventually intersect, if you have done it correctly.
Drip edge calculation and design.
Use the same calculation as above but change the height to height of drip edge except the base. The angles will be the same, just that (Ab) (Bb) and (Cb) will be different. We know that (Bi) is constant as this is the eve segment, and we know that (Ab) is your choice of length for the drip edge. Therefore we will use trig to determine the new Ab of the angle and add this measurement to the segment length of (Bi) at either end. This will create a narrow trapezoid pattern.
Scaled floor plan of medieval tent showing spokes, eve and base circumference, and furniture placing. This drawing was scale to ¾ inch to the foot
Cross-section of medieval pavilion. The brown lines are the frameworks; the black and red lines are the canvas.
As further aid in setting this type of tent up, I have included rope positions. It may not be period, but it does aid in transferring the stress points from the tinker toy to the center pole. Keep in mind that the opposite spoke is set up the same way, thus creating balance, and transferring the stress to the center pole. This also aids in reducing tension on the canvas, and to prevent a failure when either setting up or tearing down, on the tinker toy. With these adaptations it is possible for one person to setup this tent. The ropes once connected with the spokes and upright should be a close as possible to the 45-degree angle, and since gravity pulls downward, ropes will take the tension and allow for flexibility in windy conditions. Lets say that the weight is 1 lb to the foot transferring out from the tinker toy. This will create a lever action on the holes the spokes go into on the tinker toy, and may in time fail at the holes. This extra insurance will counter the foot-pounds away from the holes and transpose it to the center pole.
After during the calculations and thus the pattern, we now have the roof panel and the wall panel. Once you have completed your drawing, it should look similar to this one. You may notice a middle drawing. This drawing is the roof drip edge taken from the wall panel, to allow rains water to be shedded. This one is designed to be 1 ft wide.
At this stage, we should now have a working drawing to scale, and the necessary angles to design the canvas panels. DO NOT CUT YOUR CANVAS AT THIS STAGE, as the slightest measurement variations could result in the canvas not to fit properly. You may at this stage make a scale model, like the one shown at the top of the article. Some may even venture to the one shown below, to check measurements and assembly. To determine amount of fabric needed please go to fabric layout for medieval center spoke pavilion.
Shown here is the scale cloth model of the tent, for final positioning of the canvas, and any minor changes to be made. In this case after designing and making the model, I will incorporate storm flaps on the opening to make it nice and comfortable inside. Scale of model is 1 inch to 1 foot. All angles for roof and walls will remain a constant to the full size version, unless the vertical or base measurements are changed. It should also be noted that the red panels is the inner lining. Outer panels, which would have been white, are not shown here.
Shown in this photo are the tinker toy, center pole, spokes and rope arrangements, all to scale. Also is the inner lining panel. More on inner linings will be cover in options. Scale of model 1 inch to 1 foot.
A view into the model’s interior showing the lining and framing.
As one can see there seems to quite a bit of room in the pavilion, and there is, but there is one disadvantage to this design and that is the center pole. This tent is not a clear span type, and for those that wish to have a clear span please check the article on star pavilions. However for those that wish for this amount of space assuming that the base is 20 square feet, it works out to 314 square feet. The star pavilion shown below is roughly 153 square feet. In short this style double the square footage, and one other advantage on the 12 spoke, it can have separate rooms, partition by drapery.
Now that we have a design, and I will mention, this design can be applied to fewer spokes of more spokes. If you wish to have more spokes within the design, consider that the tinker toy will have to be increase in diameter. The min. diameter using a 2-inch depth hole is 16 inches. When making mine, I made it to the width of the plywood I had on hand, which work out to be 22 inches. I believe there is enough room to do an 18 spoke design on this style using the same diameter tinker toy, thus increasing the size of the tent to 28 feet in diameter base, however it may be required that the doweling would have to a larger diameter to handle the stress loads and wind loads.
Because of materials required and the need to transport, and that it is most likely I Christiana will have to set this pavilion myself. To fit the current furniture I have, and to max available space, I had chosen the 20-foot diameter pavilion. With this in mind, we will now proceed to the framing package.
No comments:
Post a Comment