Cover for a Small 2v Geodesic Dome Using Waterproof Canvas

Introduction:

Domes are a popular structure at Burning Man and other festivals, but creating a cover usually involves glueing or taping tarps together. I built a small (4m diameter) dome and wanted to cover it in a way that was quick to assemble on-site, durable, and looked nice.

What are we making here?

The cover when completed is one piece with a zippered door, and can be sewn at home using a personal sewing machine.

The cover is for 2v geodesic domes - my dome is 4 meters diameter. It is constructed from 6 pentagons of fabric that have a point in the middle, and 10 equilateral triangles of fabric. Each pentagon is cut from two pieces due to the three dimensional shape of the pentagon.

How big can I make the cover?

Each pentagon or triangle is sewn onto the continually larger whole of the cover, which means the limit for the size of the cover is based on how much fabric you can fit into the right hand side of the needle in your sewing machine (the width of the new piece you are attaching must be able to fit). I would not recommend trying to make a cover for a dome too much larger than 4 meters diameter using waterproof canvas as it is quite thick - but if you used a lighter weight fabric you could go a lot larger! Also consider limitations in fabric size - bolts of fabric are 60" wide so it will limit the size of pieces you can cut.

Any other restrictions?

These instructions assume you already have the dome structure built, and can assemble it for testing - you must be able to test-fit your cover onto the dome as you progress to assure the cover is not too small (or too large).

It also assumes that you have basic sewing skills - you know how to use a sewing machine and can sew in a straight line, and know basic sewing terminology like 'seam allowance'.

You'll need the following materials:

Generic sewing goods:

• sewing machine
• heavy duty needle for sewing machine (denim rated will work)
• sharp scissors
• pattern paper
  • search Amazon for 'dotted pattern paper' in the 'Arts, Crafts & Sewing' category
• pattern cutting board or flat surface to cut out fabric from patterns
• fabric marker or fabric chalk
• pins
• measuring tape
• ruler

Cover materials:

• at least 3 spools of heavy duty outdoor thread
  
  • Coats Outdoor Living works well
• a large amount of waterproof canvas
  
  • Fabric Wholesale Direct has good color selection and the lowest price I found.
  • I bought 35 yards of fabric and had a lot leftover - I used at least 25 yards.
• several rolls of double sided basting tape - 3/8" wide, 60" long
• double pull reversible zipper, marine fabric, in a length to match your door
• 1/2" grommet kit and hammer to affix grommets

Securing your dome cover to the ground:

either:

• 6 or more 12-24" long 3/8" lag bots (choose the length based on how loose you expect the soil to be)
• large washers (1" ish?) that fit on the lag bolts
• impact driver with matching bit to drive in the 3/8" lag bolts

or:

• 6 or more 12-24" long 3/8" thick rebar, bent into 'candy cane' configuration
• sledge to drive in the rebar
• rebar puller to pull out the rebar

You will only need to cut two pattern pieces - one for the equilateral triangle, and one for half the pentagon.

• Equilateral triangle
  • each side of these pieces is as long as one of the long bars of the dome.
• Half Pentagon
  • each pentagon in the 2v dome is outlined by five long bars, with five short bars extending radially from the center to the points of the pentagon.
  • the half-pentagon cuts the pentagon in half - starting at the top point and ending in the middle of the bottom side.

1. Assemble one equilateral triangle and one full pentagon of your dome structure. If the dome is already completely built, that's fine too.
   1. This is ESSENTIAL as you need to measure properly not just the length of the bars, but how much space your method of connecting the dome bars takes.
2. Measure the lengths needed for both the equilateral triangle and the half-pentagon.
   1. make sure to measure from the MIDDLE OF EACH CONNECTION POINT, and not the end of the bars - to account for the space the connectors take, or to account for connections being an inch or two in from the end of the bars.
3. using the dimensions you recorded, draw the outline on pattern paper with pencil.
4. use a ruler to add 1.5" all around the outline of the piece, this is for your seam allowance.
5. cut out the paper pattern pieces on the seam allowance line you just drew.
6. lay out your pieces over the dome structure to check the size, adjust as needed.

Using the pattern pieces you just created, you will need to cut out the following pieces of fabric to create your cover:

1. 10 equilateral triangles
2. 6 half-pentagons
3. 6 half-pentagons with the pattern flipped over, to make a matching side

Tips:

• You may find as you cut out the half-pentagons that alternating cutting a front piece with a back piece will allow you to maximize fabric usage and minimize waste.
• Cut out pieces as you sew them together at first, to ensure the fit is correct - if you cut everything out and the pieces are too small, you will waste a lot of fabric.

I used a full flat felled seam (also called a double flat felled seam) in my cover construction to hide all raw edges, and to provide the best durability and waterproofing.

Review this youtube video which shows how to sew seams using basting tape and waterproof canvas - the full flat felled seam is the last seam shown in the video, and he gives a good discussion of why each seam is used.

Practice sewing this seam on scraps of fabric left over from cutting.

Tip: Pins and ironing are unnecessary to sew the seams on this dome if you are using the double sided basting tape! The tape secures the seam for you. You may however find a pin or two useful in the corners where the most tension will be as you are sewing.

If you don't care about waterproofing or raw edges, skip this part (and you can optionally omit the basting tape), and you can use whatever seam is durable enough for your liking.

• If you change the seam type, you will also want to reduce the 1.5" seam allowance - the full flat felled seam takes a much larger allowance than other seams. Test out your seam and adjust the pattern size accordingly.

1. sew together two matching halves to make one pentagon using the full flat felled seam method.
2. check the sewn piece on your assembled dome structure to see how the piece matches up.
   1. if it is too large, increase your seam size or trim from the edges.
   2. if it is too small, reduce your seam size or recut the pieces and start over.
3. sew one equilateral triangle onto each side of your pentagon using the full flat felled seam method as before.

Your dome top is complete.

Tip: Take a scrap of fabric or ribbon, write 'top' on it, and safety pin it to the center of the pentagon. This will help you to find the top as you sew the other pieces (there is a lot of fabric to get lost in!).

Working your way around the dome, sew in roughly this order (refer to diagram for a visual explanation of each step):

1. Attach a half-pentagon to one of the equilateral triangles hanging from the dome top.
2. Attach the matching side half-pentagon to the piece from step 1.
3. Attach the matching side half-pentagon to the equilateral triangle adjacent to it on the dome top.
4. Attach an equilateral triangle to the bottom outside of the matching side half-pentagon.
5. Attach a new half-pentagon to the other side of this equilateral triangle. This is the new half-pentagon to be used in step 1.

Repeat until all your half pentagons are used up, attaching the last equilateral triangle in step 4.

When attaching the last equilateral triangle, leave the right-hand side open. This will act as the door.

Tip: After you have sewn on ~2 pentagons, I highly recommend fully assembling your dome and trying on the partially sewn cover to check the fit and adjust as necessary.

1. Fully assemble your dome structure and put the cover on to make sure everything fits properly.
2. Make marks in five or six different spots around the bottom, roughly equidistant.
   1. The cover will be staked down through grommets placed in the bottom of the cover at these spots.
   2. The spots should be low enough to reach the ground and should pull the cover slightly taut to prevent wind flapping, and should be high enough to be clear of the bottom seam (which you have yet to sew).
3. Check that the bottom of the cover does not have too much fabric - if it does, you can trim off around the bottom before making the final seam.
4. Sew a simple hem seam on the bottom of the cover, folding over twice to hide the raw edge of the fabric.
5. Hem independently each side remaining on the door opening, folding each over twice to hide the raw edge of the fabric.
6. Attach the closed zipper with pins to the back side of the door and the opening. Check that you can easily zip and unzip the door with your chosen spacing, then sew the zipper to both sides. Sewing each seam twice is recommended to keep the zipper secure.
7. Using the grommet making kit, follow the included instructions to punch holes and secure grommets in your chosen locations.

CONGRATS! YOU FINISHED YOUR DOME COVER!

Skylight:

If you'd like, you can cut a hole in the center of the ceiling of your dome to help hot air escape. The size of the hole is at your discretion. Fold down the edge and sew a seam here to keep the edges neat. Keep in mind this means the dome will be open to rain from this hole - if the weather looks bad some protection can be had by sticking an umbrella through the hole in the top of the dome and securing it.

Internal Ties:

You can make loop ties to help secure the cover to the dome on the inside, as well as provide attachment points for decorations. To make a tie:

1. Cut a long strip of fabric leftover from your dome, about 1.5" wide and as long as you like.
2. Fold the long edges in on themselves twice to hide the raw edges, and sew to secure.
3. Cut the sewn strip into lengths that will make a nice loop that you can pass ball bungee cords through.
4. Sew onto the inside of the dome. A loop at the end of each of the five equilateral triangles coming down from the top pentagon are good locations to attach ties, but do as many/wherever you like.

Sewing Tips:

• The seams used to create the dome create a lot of layers of fabric, and it can be very difficult to sew when you get to points where a lot of seams meet. To help this:
  
  • Use judicious trimming of extra fabric at the point of joining to reduce bulk.
  • It actually might work better if things don't line up perfectly as there will be fewer layers to attach at a time.. it's ok as long as all the pieces attach somehow.
• In some spots where a lot of seams meet, you may end up with some small holes because it is too hard to sew everything together, and the dome may not be completely waterproof.
  • For these spots, you can try applying some flexible rubber sealant. I haven't had a chance to test the dome cover in heavy inclement weather yet. Light rain was no problem.
• Last tip.. it doesn't have to be perfect. It's a dome cover, not haute couture.

Note - these notes about securing are specifically for Burning Man which has extreme winds. This may not be necessary for your scenario.. but it never hurts to make sure your dome and cover are super secure! To secure the cover:

1. Make sure the dome structure is already secured to the ground.
2. Put on the cover.
3. Attach the cover to the dome structure on the inside if you added attachment loops.
4. There are two methods to secure the cover to the ground. The cover should be secured to the ground separately from the dome itself.
   1. The preferred method to secure the cover is to use long 3/8" lag bolts with a washer, driven into the ground using an impact driver. You can find a discussion on using lag bolts here. You only need the lag bolt and a washer (no chain pieces), drive them directly through the grommets with the washer on top.
   2. If getting the materials to use lag bolts is not possible, you can also use 3/8" candy-caned rebar through the grommets.