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Picture of Giant Halloween Spider
Let's face it - every house needs a giant spider at Halloween.  Not the "Oooo a scary spider just dropped on my head as I went to the front door" kind of spider - I'm talking about the "That furry black beast just ate my dog" kind of spider.

Well, this one isn't quite that big (see last photo for one that is) but the design can easily be scaled up with larger materials to a prop that is very large.

This design is based on a spider we made a couple years ago, with modifications to minimize the number of pipe fittings, and flexibility to add your own body shapes and sizes.  We used 1/2 inch PVC pipe because we had lots of off-cuts left over from a gardening project - I would probably choose 3/4 inch if starting from scratch.

Given the number of joints in the legs you can also pose the spider in different ways (like front legs off the ground ready to grab a passing child) or omit the last segment of each leg so the spider sits flat on the ground.  We found this configuration better for use suspended in a web.
 
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Step 1: Materials and Tools

MATERIALS (all PVC pipe is 1/2 inch, you can scale up as needed).  Approximate prices shown from small hardware store - you may be able to find better pricing at big box stores.  Prices are for all components, not each component.

60 feet x PVC pipe [$12.00]
1 x PVC "T" fitting [$0.40]
3 x PVC 4-way "Cross" fittings [$3.00]
16 x PVC 90 degree "Elbow" fittings [$4.00]
16 x PVC 45-degree "Elbow" fittings [$13.00]
8 x pins to hold legs to body (16d nails work fine)

2-3 x cans spray foam insulation [$15.00]
2 x cans black spray paint [?]
PVC pipe primer and glue [$9.00]
Duct tape [?]

TOOLS
PVC pipe cutter
Drill with 3/16 inch bit
Sandpaper
Drop sheet
Ruler

Step 2: Build the Spine

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Cut 8 x 5-inch pipe segments - these will be the struts from the central spine to each leg.
Cut 3 x 3-inch pipe segments - these will join each of the vertebrae
Cut 1 x 12-inch pipe segment - this is the "tail" and supports the abdomen of the spider

Using the PVC primer/glue, glue 1 x 5-inch strut into each side of the PVC "T" fitting, and 1 x 3-inch segment into the center of the "T"

Now repeat with each of the 2 x PVC "Cross" fittings - 1 x 5-inch strut into opposite sides of the cross, and 1 x 3-inch segment into a center hole

Repeat for the last Cross fitting, this time using the 12-inch tail instead of a 3-inch segment

You should now have 4 x vertebrae ready to be joined.  It is critical that all the leg struts are parallel - I raised then on two blocks while being glued to ensure they were all in the same plane.  Apply primer and glue to the middle of a "T" fitting and the corresponding hole in the next fitting.  Insert the fittings together, twist 90-degrees to get a good joint, then hold together on the raised blocks of wood so the struts set in the same plane.

Repeat for all 4 x vertebrae.

The final step is gluing one 90-degree "elbow" to the end of each leg strut.  It is important that each elbow is perpendicular to the spine, I found the easiest way was to insert a longer piece of pipe dry into the side of the elbow not being glued, glue the elbow on, and while wet rotate the piece of pipe until it is at 90-degrees to the spine

Step 3: Build the Legs (8)

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Cut 24 x 2-foot pipe segments - these will be the segments for the legs (3 per leg)
Cut 8 x 4-inch pipe segments - these will be the pieces that join the legs to the spine

Using PVC primer/glue, glue 2 x 2-foot leg segments to each side of a 90-degree elbow fitting.  Repeat 8 times.

Glue 1 x 2-foot leg segment to a 45-degree elbow fitting.  Repeat 8 times.

Now glue the segments joined with the 90-degree elbow to a segment with the 45-degree elbow at each end.  Make sure that all pipe segments are parallel in the same plane, and that the joint with the 45-degree elbow points inward.  Repeat 8 times.

Glue a 4-inch segment to one side of a 45-degree elbow.  Now glue this to the other end of a leg assemble, making sure that the 4-inch segment is parallel to and in the same plane as the 2-foot segment on the opposite side of the leg.  Repeat 8 times.

Sand the last inch of the 4-inch segment on each leg to allow a looser dry fit into the "hip" elbow attached to the spine.

Step 4: Attach the Legs to the Spine

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Insert the 4-inch segment at the end of each leg into the "hip" elbow fitting attached to the end of each strut of the spine.  Rotate the leg as you insert it to ensure the leg seats all the way into the fitting (approx 1-inch). Position the legs into the final shape you intend to pose the spider, usually four legs forward of the body and four legs rearward.

Once satisfied with the position of the legs, drill and drill a 3/16 inch hole all the way through the hip leg fitting and leg segment inside.  Drill the hole approximately 3/8 inch below the end of the fitting.

Step 5: Build the Body, Attach to the Spine

I decided to use old packaging material I had laying around - you can use almost anything as long as it is light and waterproof/durable (the spider will probably be outside in the elements).

Make the abdomen for the spider.  This can be made from anything as long as it is big, round and light.  A beach ball or balloon is ideal.  Other spider builders have made fiberglass balls - I think a beach ball is easier :)

Our spider uses a plastic garbage bag filled with foam packing peanuts, and 'shaped' into a spherical shape with duct tape.

Attach the abdomen to the tail of the spine with duct tape or similar.  Try and fill major crevices with duct tape.

Make the thorax for the spider - this can be made from almost anything as long as it is reasonably firm, and long enough to overlap the front of the spider.  I used some blocks of polystyrene foam, you could also use a plastic bag filled with crumpled paper, cardboard box inside a plastic bag, etc.  Attach the thorax to the spine with duct tape or similar.

Continue taping the thorax, abdomen and spine together.

Step 6: Foam the Outside of the Spider

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Start spraying sealant foam on the outside of the spider.  Make sure you use random patterns as it will continue to expand and set into the shape you spray.  The more random your pattern, the more 'organic' the final skin will look.  Don't try to spread the foam after spraying, just spray and let it plump up.

As each side dries, you can rotate and keep spraying.  Slide a nail into the end of the spray tube to prevent it setting in the tube between applications.

Be careful you do not get the sealant foam on your clothes or hair.  It is incredibly sticky and only removed with acetone - not good for either surface.

Step 7: Paint the Spider

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Once the foam is dry, spray the spider body and legs.  You may need to go over the body twice to reach all the nooks and crannies.  Place masking tape over the last inch of the legs before spraying so that the fit to the body does not become tighter (remember you sanded this in step 3).  Remove the tape prior to assembly.

Step 8: Final Assembly of the Spider

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Check the spider to see if any foam is blocking the "hips" attached to the body.  Cut away any foam with an Exacto knife or similar.

Insert the legs, the pins, then respray any pieces missed.

Voila!  Biggest spider in the neighborhood.

Step 9: Final Thoughts and Alternate Designs

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The spider can be scaled up with larger diameter PVC pipe and longer leg segments.

Pictures on this page are from our "Big Brother" spider - he has 4-foot leg segments, a 4-foot abdomen and is as big as a small car.  This gives you an idea of how the basic design in this Instructable can be modified by removing the last leg segment so it sits flat on a roof, web, etc.

Some other thoughts and options:
- Mold a face and add scary eyes and teeth
- Buy pipe insulation sleeves and slide over the leg segments to make them thicker
- Rotate the front legs back to make the spider 'rear'
- Successively shorten the last segment of each leg front to back to make the body angle upward, ready to pounce
- Stick marbles or glass beads in the front of the 'face' for eyes
- If you intend to suspend the spider, attach an eye-bolt or similar to the center of the spine, extending down through the foam to the outside of the body, so that a rope can be attached to take the weight

Step 10: Last Minute Change...

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Found an old skull prop that I had and decided to go for a "human skull bursting through the front of the spider" effect.  Steps were easy:
- Carve out space for the skull
- Hot glue it on
- More spray foam - make sure it runs back over the body
- Mask the skull with painter's tape
- Spray the new foam red
- Go back over the overspray with black
winter5683 years ago
My son and I just finished our giant spider. I added some eyes and LED lights to light them at night. Just on the top back of the spider you can see the solar panel for the lights. We spray painted the body of the spider bright red first to fill in all the cracks and then sprayed the the body black. Nice multicolor effect. We spent 2 days and about 40 dollars in materials to build it. As always, wonderful ideas and instructions to be found here.
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mcorbin winter5688 months ago

Cool! This could become a photo op for trick-or-treaters. They could lie down and become part of the scene

This is a better close up of the eyes to show more details. All of the eyes started out point forward, but through the process of taping the wires down and the the shifting of the spray foam some changed their orientation. All and all it seems to work.
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Here is a closeup of the eyes. They had small holes in the tops of each eye that I wanted to close up so I just used the spray foam on each which created a bubble that just added to the organic look of the face. I used an empty windshield washer plastic bottle cut up to form the pincers and a scrap piece cut into small teeth with 4 LED lights behind them. This turned out so good that I want to make at least one more spider to put on the roof of the garage.
GiantSpiderEyes.jpgGiantSpiderBack.jpg
ORDuckFan (author)  winter5683 years ago
That is way cool! Can you post a close up of the face (spider - not son :))
spacecadetjess made it!9 months ago

Fantastic tutorial! Made this over the course of a week with for this year's decorations with stuff we pretty much had laying around the house! Sadly I didn't have the supplies to make teeth or a crazy body, but I like him! Thank you for the instructions! :)

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great use of web. Probably very cool to walk under on Halloween night

gonecountry007 made it!9 months ago

Thank You for the IDEA. I used a 2 liter soda bottle and fastened the legs to it.

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ORDuckFan (author)  gonecountry0079 months ago
Awesome! I love it. It's almost scarier with a small body - kind of like a giant daddy long-legs.
NerdSpouse9 months ago
Just finished building a version of the spider. This was really easy and fun.
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finfan73 years ago
The skull one definitely wins the creepy contest. I think I might have to make one of these and hang it from my ceiling.
And this is a great Instructable. Plenty of detail but kept relatively simple. Good work.
kslatin3 years ago
Just letting you people know. to save money for the body I just taped two shoe boxes together.
acardenas23 years ago
Didn't buy glue or primer, bought a few extra joints JIC, 37 dollars.
acardenas23 years ago
Love it! We are on our way to the local HD to pick up all the stuff. Love your tomb stones too. Go Ducks!
kslatin3 years ago
How much does it cost for all of the supplies total. The thing is that I really want to try this but i don't have a large amount to spend.
l8nite3 years ago
the skull is over the top cool !
Awesome!
simonfrfr3 years ago
AWESOME! I should make one of these! I will make it move though!
bwells24 years ago
I would be scared out of my wits if that thing would be real!
sockit4 years ago
Great Spider - looks way easier than the paper mache-over-ballons version I did one year. One 'simplification' option on the legs would be to eliminate 8 of the pvc connectors (and the 8 short stubby pipes), by having 45 degree connectors come off the spine instead of the 90 degree ones. I haven't done Holloween decorations in years, but this 'ible may inspire me to get back into the spirit!
ORDuckFan (author)  sockit4 years ago
I don't think removing the 90-degree elbows and stubby bits will work - the legs would all be perpendicular to the body, and they need to be flared.
Here's a sketch...
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sockit sockit4 years ago
But I now realize that my bad suggestion would not allow rotating the legs. They would have to stick straight out.
Are your tombstones football teams? If you had one that said "Florida Gators" that would pretty much make my day :) I'll die happy when USF beats them.

And more on topic: I love your spider. Will definitely have to try it once I don't live in an apartment any more.
ORDuckFan (author)  mooseinakilt4 years ago
We're huge Oregon Ducks fans - all the tombstones are the Pac-10 teams and notable other recent wins - Sooners and Michigan
Love it! I saw clips from their first game of the season where the score was something ridiculous and they made the poor guy-in-a-duck-suit do an insane amount of push ups. You back a good team. I'm anti Michigan also, so that's good enough for me :)
ORDuckFan (author)  mooseinakilt4 years ago
Beating Michigan at our home in 2003 when they were #3 was awesome, spanking them in 2007 in Michigan was even better. Nothing like running a Statue-of-Liberty play *and* a FAKE Statue-of-Liberty play against them in the same game :D
Hehe... Great Stuff is not great stuff. Good luck getting it off of anything.
I respectfully disagree: It's great at sticking to everything, including clothes, skin, hair, children, pets... :-)
oolala1704 years ago
this is soooooo cool awsome yur awsome thanks
Some Dork4 years ago
My wife is a spider nut and saw this . . . guess what I'm on the hook for making next Halloween? :)

There have been a few similar projects like this in the past, but this is my favorite by far. Well constructed and the organic look from the spray foam really sets it apart. Love it!
b75cycle4 years ago
Built this today. Added golf balls for eyeballs. Used the foam to create pincers. Double check the total amount of PVC pipe needed to save extra trips to the hardware store.

60 ft PVC tube needed
Step 24 - 2ft section of legs = 48 feet

Had a lot of fun building this and the entire family got involved. Thanks for the plans!
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ORDuckFan (author)  b75cycle4 years ago
Thanks for the heads-up on PVC pipe! Materials list changed. The legs do in fact need 48 feet ... 8 legs x 3 segments x 2-feet.
l8nite4 years ago
to dang cool !!! where did you get the 4way fittings? I can never locate them at the home improvement stores
zascecs4 years ago
Wow, I made the exact same thing a few years back, except that it was hung from a tree with several pulley systems, making it go up and down.

..and with remote controlled blinking eyes. Anyways, great i'ble.
zack2474 years ago
this is awesome! i totally want to make one of these...
That is amazing! Great idea!

Oscar
Wesley6664 years ago
You used that expanding construction foam on the body! I was wondering how you got it to look like a giant black meatball! LOL! Jkes, this is soooo awesome!
tjdtjd14 years ago
that is awesome. I am sooo doing that this year.