This Halloween I wanted to build a huge outdoor decoration to compliment our "End of the World" party theme. We have a sewer manhole cover in the corner of our yard, so the idea came to mind to build a large tentacled creature appearing to crawl out of it. When completed it was about 6 feet tall and around 30 feet across.

This is a relatively easy build, makes a big impression, and should be versatile enough for lots of Halloween displays.

Rough list of materials:
  • 1/2" plywood - 2' x 2'
  • 1/2" foam board - about half a sheet (4'x 4')
  • 1x2" lumber - about 2' worth
  • 8' steel studs - 3
  • Vinyl trim (like flashing) - about 6' x 3.5" wide
  • 8" diameter HVAC flex duct - 25'
  • 6" diameter flex duct - 25'
  • foam pipe insulation - various diameters, 3 pieces
  • screws, latex caulk, liquid nails, and paint
  • fog machine and spot lights for extra wow

Step 1: The Base

The first step is making a base for the monster. In my case I built something that would fit exactly on top of the existing sewer cover. If you're just setting something in your yard, the construction of the base doesn't have to be as particular. 

Note: If you are fitting something over a real sewer, realize you run, a likely very small, risk of having your utility company take exception to it and having to move it.

I started the base by cutting a 2' circle from the 1/2" plywood (a jigsaw is a good tool for the job).

Next I cut a 1x2 board into eight 2" lengths. Then I screwed these around the edge of plywood (see photo). These pieces act as standoffs for the plywood to sit flat since the real manhole cover (which will be left in place underneath) is slightly domed. Then everything was painted flat black.
<p>Love this! Years ago my co-workers and i built a monster with 2 tentacles and we used foam pool noodles for the suction cups. Your material choice is probably more cost effective and we just got lucky to have found them at the dollar store!</p>
<p>ahahah epic very original top wprk</p>
<p>I like it. Nice project and creative use of regular items to build. Thumbs up!</p>
<p>Cthulhu lives! </p>
<p>Japan, here I come!</p>
Very Very COOOOOOOL!!!!
How long did this take?
I probably spent a couple weekends on it. WIth all the steps laid out now, someone could probably hammer it out in a couple days...some of that just being time for coats of paint to dry.
Serious awesomeness!! And fantastic techniques so much easier/better than what I would have guessed you'd used.
We totally need to do this. Great instruction and pictures. PERFECT for the fog machine! <br>
This is just TOO wonderful!!! Our historic Neighborhood hosts a big Halloween &quot;party&quot; and we see 3000+ trick or treaters each year. There is a contest for the best decorated house; unfortunately I'm out of the &quot;zone&quot; and have to keep my decorating to a minimum since I can't afford to buy that much candy on my own. However, I'm betting I can find a friend in the zone who would LOVE to use your idea, as much as I would!
Oh my gosh that's so scary! I would steer clear of a house if I saw this in the front yard! o.o
That thing is awesome, the only thing that it's missing is some movement & it would be perfect.
Congratulations on the win! I love the idea and execution.
Congratulations on being a finalist in the Halloween contest!!! Can&rsquo;t wait to see if you win! Good luck! (I really love this monster)
This looks like you could use a fan to inflate the tentacles &amp; give them some movement (the material looks too heavy to be self supporting with air pressure alone, but perhaps hinges in the frame would give it some flexibility)
If you used thin (like plastic bag thin) sheets turned into tubes or nylon tubes you could do it. But it would be pretty nosy.
Hmmmm..... <br>Maybe thicker plastic, and music playing to cover up the sound of the fan? <br>An inflatable doll attached to one of the flying tentacles? <br>I'll just have to run the experiment for next year's Halloween, I guess.... (bwaahahahahaha)
Ever see those fan powered things that are just giant air tubes made of nylon that dance around, something like that could be made out of one peace if you where any good at stitching you could sew a monster together in one or several parts and even give them bends so that the air flow caused them to fale about erratically or controlled. But when I say plastic http://www.designtavern.com/2009/01/street-art-joshua-allen-harris-inflatable-bag-monsters/ I'm thinking of both this artwork and there is a way in movies even species used it, to create realistic looking life by using nothing more then plastic inflated either with fluid or air. But ideally THIS is what I mean http://www.youtube.com/watch?v=pv1EQ_BAO7U&amp;feature=plcp
This looks great and I think having one of the tentacles wrapped around a lifesize dummy would look fantastic <br>
lifesized dummy?!? No, no, next Halloween get a girlfriend wrapped in it and your costume should be an exterminator trying to get her out.
I've seen enough hentai to know where this is going.
Cool idea!
Awesome idea - may have to use this idea for some tentacles in the future!
I loved this man. BIg and easy. Could probably add some movement with out too much trouble. I'lll have to try it next year. Thanks, hope you win. dx
just a note, if you paint the suckers before you cut them up, it will be A LOT easier.
For the most that's very true! I wanted to hit the ends (one per) with paint, too, but yeah you could do a combination of painting before and after cutting :)
hope you win
This has got to be one of the best yard decorations I've ever seen- awesome!
This is awesome. very creative use of common products to make a fantastic yard decoration.
WOW I love this! Looks great!
Great Job! i know what ill be doing next year. Thanks for posting. Voted

About This Instructable




Bio: Web developer by day. Gamer by night. Halloween fanatic and DIYer, all the time! My projects tend to combine pop culture, technology, and craftsmanship to ... More »
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