This took us three tries. Hopefully you'll get it in one. See the last sections for more on disaster.
First, print out a diagram
. It may be confusing, so I've also uploaded some pictures to help.
In the pictures
A = Red
B = Blue
C = Yellow
Notice that B is the edge of pentagons and hexagons. A is always the inside of pentagons, and C is always the inside of hexagons. That's it!
Lay out the bottom ring first. It's going to be in a pattern of CCBCCB all the way around. It will be 15 pieces. Connect them with your 4-way connectors, leaving them pointing up and a little in, toward the middle of your dome. Make sure the top of the machine screw, the rounded end, is on the outside of the dome to prevent your plastic from tearing later. Attach each strut to it's vertices with duct tape.
From here on, it will be useful to have at least 3 people.
Start building the lower ring of triangles. As you can see from the photos, what you are really building is the tops of a hexagon, then the bottom of a pentagon, then the top of a hexagon, etc. Use props to keep it upright. You won't know how far in they are supposed to tip until you are getting close to connecting the last piece with the first. At that point, the ring of triangles will probably be stable. Now screw the vertices to the struts, trying to keep all sharp edges on the inside.