Here's how to easily make a HUGE spider decoration. It requires minimal specialized tools, is about 5 feet tall, costs about $100 in materials, and you can store it every year for re-use. I made it because I have about 500 kids come by every year on Halloween and I wanted to make something spooky and fun.
Step 1: Buy the Supplies and Cut the PVC to Size
For a spider that is approximately 5 feet tall, you will need the following supplies, all of which I was able to find at Lowe's.
For the legs:
A piece of scrap wood (about 4 inches wide by 18 inches long) for the spider body.
4 u-bolts large enough to slip over the width of the PVC pipes
5 pieces of 10 foot long PVC pipes (I used 1 1/2 inch thick pipe)
6 matching diameter 90 degree PVC joints
16 matching diameter 45 degree PVC joints
PVC Pipe cement
Black spray paint
PVC pipe cutter (you can get one on Amazon, I highly recommend this instead of a hacksaw-- never use a circular saw on PVC pipe)
For the head and body (you can use your creativity, but here's what I did):
An empty bleach or detergent bottle for the abdomen
Some fuzzy black fabric to cover the abdomen
Spray glue to attach the fabric
Small carvable foam pumpkin for the head
Paint for eyes
White plastic for fangs/mandibles (I used rigid white plastic from a bucket lid)
After gathering the supplies, carefully measure and cut the PVC to size (WATCH YOUR FINGERS!). For the back legs, take the first three 10-foot pipes, and mark them so each one will make two 3-foot sections and two 2-foot sections (3+3+2+2=10; for all three of those). Carefully use a specially made PVC cutter and cut those. Take the fourth 10-foot section of pipe and cut it into six 1.5 foot sections and two 6-inch section (1.5+1.5+1.5+1.5+1.5+1.5+.5+.5=10). Take the fifth and last pipe and cut two more 6-inch sections. All of these pieces will be your spider's back three sets of legs, and the last long pipe will be the raised front legs.
Step 2: Assemble the Back Leg Sets and Attach to the Base
The back three sets of legs are as shown in the diagram. I made mine exactly flat and exactly the same, because I installed the spider on the lawn with stakes (I will talk about that later). You may wish to slightly angle the legs back if you don't have an area to stake it down, so it will be more stable if you can't put in stakes.
I tried to make the spider WITHOUT pipe cement, which made it too rickety. So, you'll need to assemble each of the three pairs of back legs thusly, moving left to right, using pipe cement at each elbow joint:
A 3 foot section with a 45 degree elbow. To that elbow, a 2 foot section topped with a 90 degree elbow. Down with a 1.5 foot section, with another 45 degree elbow which will pass under the body. The six inch section passing to another 45 degree elbow. Going up, a 1.5 foot section to a 90 degree elbow, down on a 2 foot section, then a 45 degree elbow, ending in a three foot section. (See my diagram for clarification).
Now that we have the back legs, we will make the body to which they will attach. Getting a drill, drill holes in the scrap wood that match the diameter of the u-bolts; these holes will travel the length of the wood, so the u-bolts are in a vertical line. You will pass the u-bolts under the PVC pipes and up through the wood, then use the nuts to tighten the u-bolts firmly on the top. In my picture, you can see how this works. If you find the pipes flop around too much, make them thicker by wrapping the pipe around and around with duct tape where the u-bolts are touching the pipe.
This is the main spider frame.
Step 3: Front Arms
You should have one 9-foot piece of PVC pipe left and four 45 degree elbows. For a spider with scary raised legs, cut the pipe into 4 lengths (I used 1.5, 1.5, 3, and 3-- feel free to vary for effect). These are the front arms of the spider. Angle them such that they are reaching out, and assemble them left to right, thusly:
A 3 foot length, a 45 degree elbow, a 1.5 foot length, a 45 degree elbow, your last six inch length, a 45 degree elbow, your last 1.5 foot length, your last 45 degree elbow, your last three foot length.
Attach them using the same method as the back legs (u-bolt, wrap the PVC with duct tape if required, and attach UNDER the board). I originally put the front legs OVER the board, but it was too top-heavy and kept flopping down-- to keep the front legs up, you need to have the legs under the board and the bolts tightened very strongly.
Paint your spider as desired with spray paint. You'll be done now, except the body and head of the spider.
Step 4: Finish the Body and Stake It to the Ground
You can be creative with what you use to make the body and head. I wanted my spider to have a relatively small body with long creepy legs.
I made my spider a body from an empty bleach bottle covered with a black bath mat from the dollar tree store. I spray-glued the bottle and covered it with the bath mat. I attached the body using a zip tie around the bleach bottle handle, with a little black duct tape. It neatly covers the u-bolt tops which are sticking up.
The head I made from a small carvable pumpkin from the dollar tree store. Spray painted it black, turned it on its side, and painted on eyes. For the mandibles/fangs, I used heavy shears to cut a rigid white plastic lid into fangs, and pushed them into the mouth area of the pumpkin/head. Then I jammed the pumpkin down on the front u-bolts, and steadied it around the base with duct tape. (Pro tip, on Halloween I used an LED light that attached to a 9-volt battery to give it glowing eyes-- bought that on Amazon-- taped over the wires with black duct tape to hide them).
To install in yard: I found that my spider had rather crowded legs, since I had made the back three leg sets on a flat surface. So, I cut two heavy broom handles in half and drove them into the ground with a mallet for stakes. The PVC pipes slip right over the broom handles, and you can manipulate the legs to a more realistic pose by carefully angling the stakes. The stakes on my spider are under the front and the back set of legs, the middle set is not staked.
Touch up with black spray paint and you're done! I added a huge spider web and some fuzzy baby spiders for props. You now have a spider big enough to eat a small trick-or-treater.