Hovercraft LARGE

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Hovercraftby dbc1218 on March 30, 2006

Table of Contents

intro: Hovercraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

step 1: The Skirt and Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

File Downloads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

step 2: The Lift Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

step 3: The Thrust Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

step 4: Steering and Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

step 5: It Hovers!!! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

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intro: HovercraftThis is a full size(4ftx8ft) one person hovercraft built over one summer for less than $200. It was built with no prior experience or knowledge of hovercrafts but with sheerdetermination to build something different. So check this project out, hope you like it.

step 1: The Skirt and BaseLets start out with a little history, I built the hover craft during the summer between my sophomore and junior years of high school. It was built by a good friend, Brain, andmyself Doug. Like I said I built the entire craft for less $200 including the engines and the fans. I will explain how I did it soon but lets start out some of the main things youwill need to get started.

3hp Horizontal Shaft Engine $50 at a local lawnmower repair shop4hp Vertical Shaft engine took it off one of my lawnmowers5.2 moisture resistant Lauan Plywood 4ftx8ftStyrofoam 4ftx8ft1/2in Plywood 2ftx4ftA couple 2x4 8ftA couple 1x2 8ft1/4in bolts and nuts 1in- 3inWood Screws 1/2in - 1inPlastic sheeting Painters SheetBrass Grommets with punch You can get this as a kit

This is about what I started out with but in no way is this everything youll need. Also keep in mind that this is how I did it, if you plan on taking on a project like this doit how you want to and with what is available to you. Use this as a guide so that you do not make the same mistakes I did.

Lets start out from the ground up. On a hovercraft the only thing that touches the ground is the skirt. The skirt is the part of the hovercraft that holds air to lift the craft. Likein the second picture my hovercraft has two engines, one for lift and one for thrust. The lift engine pushes air under the craft and the skirt holds the air in. As more air ispushed under the craft pressure builds up and lifts the hovercraft off the ground. This is how a hovercraft hovers, the only thing in between the base of the craft and theground is air.

But before I designed the skirt I designed the base of the craft. It has to be light(this is the most important) and it has to be strong enough to hold the weight of a personand the engines and everything else. Keep in mind though that when hovering the craft is actually more stable than when its not. The air pressure helps to hold the weightevenly over the entire craft.

This said here is how I made the base. I got two sheets of 4ftx8ft lauan and a piece of 2in thick Styrofoam. The lauan was the cheapest and the lightest sheet of plywood Icould find at home depot. One note, I got almost everything for this hovercraft at home depot. Lows or any hardware store will probably have the same items I got.

The base is just the two sheets of plywood with the Styrofoam sandwiched in between. Holes are drilled all the way through this sandwich and bolts are used to hold all ofthe components on the base.

Back to the skirt which is one of the more trickier parts of a hovercraft. It has to hold its shape under pressure and it has to be the right size. To big and it will drag on theground which will slow the craft down or not let it move at all and to small and it will not hold enough air to sustain lift.

To overcome this I designed my skirt to have 8 different pieces that I sewed all together with nylon string. For each of the four sides of the craft there are two skirt pieces.A upper half and a lower half, which are same shape. The picture shows what each part looked like. Basically the same design for all four sides just different lengths. Theskirt is actually smaller than 4ftx8ft by 2in on all sides. This is done so that the skirt can sandwich between the Styrofoam and the top piece of plywood. So you will needfour longer skirt pieces and four shorter ones.Each piece first needs its flap folded over and sewn. To sew the skirt I used a standard sewing machine and sewed along the seam lines which are 1/2in from the edge.Now take two pieces one short and one long and sew them together at the angled end. Now do this again for all the other pieces to form a two rectangles. Now put onerectangle on top of the other and sew along the outside perimeter. This forms the whole skirt but its not done yet.

Now duck tape along the seam for added strength then flip the skirt inside out so the seams are in the inside. Punch holes on the inside of the skirt in the middle of theflap on the top and the bottom of the skirt with the grommet kit. Put holes on all corners and every foot along the length of each side. Drill holes through the base that lineup with the grommets. Sandwich the top of the skirt between the Styrofoam and the top piece of plywood and then use 1/4in bolts to hold it all together.

This completes the skirt and the base. This is the most general part of the build. The rest of the craft is built specific to the engines, fans and components I used, you willhave to adapt these plans to fit your components.

Sorry about the pictures I could not get them to show up very well. I included the DWG file though. The last picture is the overall skirt put together showing the flap folded


over with the dashed line and where holes should be put with the circles.

Image Notes1. These two vertical blue lines are not part of the drawing

Image Notes1. Short Section2. 563. 44in

Image Notes1. lines should be here2. lines should be here

File Downloads

skirt1.dwg (45 KB)[NOTE: When saving, if you see .tmp as the file ext, rename it to 'skirt1.dwg']

skirt2.dwg (42 KB)


[NOTE: When saving, if you see .tmp as the file ext, rename it to 'skirt2.dwg']

skirt3.dwg (31 KB)[NOTE: When saving, if you see .tmp as the file ext, rename it to 'skirt3.dwg']

step 2: The Lift EngineThe lift engine and fan were added next. Here is what I used, a 4hp lawnmower, a 20in dia. fan that I think came off a air conditioner, angle steel, a piece of sheet metal,some nuts and bolts.

I cut a big hole in the base with a jig saw and then added the engine. The angle steel as seen in the picture is in a u-shape that lifts the engine so the fan is not below thebottom level of the base. I welded these pieces together but they could be bolted together with a bunch of L-brackets. They are bolted to the base and connected with apiece of sheet metal. The sheet metal has a large hole cut in it with smaller holes around it for the bolts that hold on the engine. The larger hole is so the engine sits flaton the sheet metal. The fan is just bolted onto the engine shaft just like blade was when it was on the lawnmower. Then some 1x2s and more L-brackets were used holdon some aluminum flashing to make a fan shroud. You can get aluminum flashing at any hardware store, its used for roofing but all it is, is aluminum sheet metal. A bikebrake and cable of an old bike was used to control the motor.

step 3: The Thrust EngineThe thrust engine was a little bit harder than the lift. It has a larger fan, a pulley reduction and a large fan duct. I started off with the fan. It was hand made with a welderand some steel. This is not a good idea, the fan has to be perfectly balanced and the pitch of the blades has to match the power of the engine. I you are going to build ahovercraft do not build you own fan. I was lucky that my fan did not fly apart and kill me. Do not do what I did here and get a good fan to use.

So once you have a fan you need to build a duct. I used more lauan plywood to cut out the shape and screwed in a bunch of 1x2s to hold the two pieces together. Then Iwrapped more aluminum flashing around the whole thing to make the duct.

The fan was mounted to a 1/2in shaft that ran through two brass bushings with a pulley on the other side. This was all mounted on a 2x4 and plywood frame. Then asmaller frame was made to hold the engine up so that the belt would fit. No type of clutch was used on the engine which is typical for most hovercraft. This finished thethrust engine and fan.


step 4: Steering and ControlsThe steering for a hovercraft is done through air deflectors placed behind the thrust duct. For these I just used the circle I had already cut out for the duct itself. I cut oneof them in half and screwed a 1x2 on the rounded edge of each half. L-brackets were attached to the duct hold them on and allow them to turn. Then rope was attachedto the deflectors and run through eye-bolts. The rope was criss-crossed under the duct so that moving the control stick left would turn the hovercraft left and right turnsright. The control stick was just a piece of PVC pipe with a hole drilled through the bottom so that it could pivot.The Thrust engine is controlled by a lawnmower throttle cable and the lift engine was locked into full throttle. I could have mounted the bike brake on the control stick butit would have been just one more thing to worry about so I just left it wide open.

step 5: It Hovers!!!So here is a picture of it finally hovering. Looks pretty good, but really the project did not go as well as planed. It hovered and I could ride it but that was while I wastesting and it did not have the thrust engine or fan on it. Once I added the thrust stuff it would not hold all of the weight. All is not lost though, the build went well and Ilearned a lot.

So I you are planning a project like this here are a few tips so you do not make the same mistakes I make:1. Use more powerful motors or motor if you build a single engine craft2. Get already made fans do not try to build you own3. Use light components, this is the most important it has to be a light as possible4. If you do not know what you are doing, get some plans off the internet, try Universal Hovercraft they have got some good stuff


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Comments50 comments Add Comment view all 187 comments

theXmaker says: Sep 5, 2008. 12:59 PM REPLYhey, it's better than the other rounded hovercrafts that we see always, but I just wanna ask you:can't you put anything (a cover) for safety to the back 'fan' ???????

bomberss27 says: Aug 9, 2008. 2:00 PM REPLYGreat Job. I'm building one now about the same size as yours, and I wanted to know how I could attach this fan,http://www.qcsupply.com/Products/11455.aspx , to a 5-6 hp vertical shaft engine, the shaft would probably be 7/8" in diameter. I was planning on using thisor just two leaf blowers, about 400cfm. Would the leaf blowers be just as powerful? I like the idea of the lift fan more but if it would be about the same as theleaf blowers, I think they would be easier to attach. Please respond, Thanks.

dbc1218 says: Aug 10, 2008. 10:48 AM REPLYOne of those fans could work but I would go with a horizontal shaft engine, so you could connect it with a belt and pulley like I did on my hovercraft. Alsomake sure your pulley ratio is correct so you DON'T EXCEED THE MAX RPM OF THE FAN, you'll need to govern the motor too. The extra weight ofsome sort of right angle drive to make vertical shaft engine work would be to much. Two leaf blowers would work but I would get at least 30cc each.

If you are not using plans or have not built a hovercraft before expect to have to redesign something to make it work. Just keep working on it and you canmake it work the way you want.


bomberss27 says: Aug 10, 2008. 11:46 AM REPLYSorry I was talking about the lift engine, I'm pretty sure you are talking about the thrust engine. For the lift engine could I just attach the fan to avertical shaft engine with a hub or something? The lift engine on yours is a direct drive, right?

dbc1218 says: Aug 11, 2008. 3:00 PM REPLYAlright now we're on the same page, the lift engine. The fact still is you can't connect that fan directly to the motor because you will exceed thethe max rpm of the fan. A typical small engine like the one you plan on using will rev to 3000-4000 rpm so you will still need some reduction. Apulley and belt could do this and keep the rpm below 1700. The super hard PAG fan on that site is rated at 3300rpm but I don't think it will providethe cfm you need.

I know the fan I used is very much the same fan that you are looking at and I connected it directly to the motor. So I am suggesting not to do whatI did. I just want to give you the "safe" advice not the "it probably won't break apart and send shards of fan blade flying at you" advice.

bomberss27 says: Aug 19, 2008. 2:23 PM REPLYHey, I've got one more question. How does the thrust system on the xinventions hovercraft work? They attach a wood propeller to a weedwhacker engine, and I believe that those have a really high rpm (like 7000-10000), does the wood propeller they use just have a really highmax rpm? Thanks.

dbc1218 says: Aug 19, 2008. 8:05 PM REPLYI'm pretty sure that prop was made for large model airplanes, so I'm sure it was made to spin that fast. I have seen that large of a prop atsome hobby stores and surprisingly they are not that expensive either.

bomberss27 says: Aug 11, 2008. 4:06 PM REPLYYeah I've decided to go with a fan with a higher max rpm, something from universal hovercraft probably. I think this would be much morepowerful than two leaf blowers, so I'll probably use the lift fan. Thanks for the help.

guymark says: Jun 23, 2008. 1:39 PM REPLYI am surprised at how few people have said "extremely well done", I wish I had had the initiative and determination to build a project like that while I was stillat school.

Sure it would have been even better if you had managed to get a professionally made fan - and safer too - but a huge bucketload of credit for actuallymaking even the basic components yourself too.

Seriously impressed - glad you learned a lot from it too, and excellent project and considering your age at the time, amazing resourcefulness anddetermination.

Mark

Prometheus says: Aug 8, 2008. 3:13 AM REPLYScary, my opinion exactly, and even with my own name too. I have to perform some "Hail Marys" now LOL

tigerdog330 says: Jun 27, 2008. 7:31 AM REPLYHow many hp do you recommend for the lift engine? I was thinking like 5 or 6.. Also would a weedwhacker engine would work for the thrust if I were to cutthe stem and attach a prop to it?

Prometheus says: Aug 8, 2008. 3:10 AM REPLYNo, a weed-whacker engine simply does not have enough torque to turn a propeller. A 3hp Briggs-and-Stratton upright utility engine would be muchmore appropriate for the application. You can also salvage the powertrain from a Honda "Spree" motorscooter or similar and simply attach a prop to whatwould be the drive to the rear wheel with a 20" propeller. Ideal would be the powertrain from a Honda "Aero 50", probably the most powerful moped-classed motorscooter to ever exist (built only in '85 and '86, and 70cc mods are apparently still available).

awkrin says: May 29, 2008. 11:35 AM REPLYso u can really ride it?anyways, it's funny how some simple instructables have high quality pics and this one, and many others that a simply "big", don't

dbc1218 says: May 29, 2008. 6:05 PM REPLYI did ride it but it was really under powered.

Prometheus says: Aug 8, 2008. 2:49 AM REPLYAdd another fan unit (for the airfoil) or upgrade the existing one and it might perform better. Ideally you want something like one giant innertubearound the perimeter with enough air pressure underneath to keep it just a tenth of an inch off the ground. Perhaps adjust your weight balance aswell, you might just be dragging on the ground too much. An ideal design can get around with little more than a leaf-blower as forward thrust, but whocan get ideal without spending several digits....Awesome project, and with a few minor tweaks could perform like a dream come true. Well worth themoney and time to try.


Prometheus says: Aug 8, 2008. 2:54 AM REPLYP.S. Added vote for book contest.

carpe_noctem says: Jul 30, 2008. 8:20 PM REPLYperhaps you could look into the jet engine instructable and fill the skirt using the exhaust( i know you should cool it down) and use tha actual drive(?)to power a fan or vice versa

Kalianepic says: May 27, 2008. 8:26 AM REPLYGreat instructable! I have always wanted to make one of these. Do you think that I could scale it down to something slightly bigger than a skateboard? I canforesee some stability issues, but really nothing that couldn't be overcome with a gyroscopic stabilizer... Any thoughts?

carpe_noctem says: Jul 30, 2008. 8:18 PM REPLYi highly doubt their would be enough support

now a surfboard, thats a different story.

perhaps 60in long by 24in wide would be enough, just over twice average deck size.

Prometheus says: Aug 8, 2008. 2:41 AM REPLYActually a surfboard was attempted on "MythBusters" (Discovery Channel), and was rather unwieldy. However, perhaps a design similar to hydrofoilboats could be applied with two of them and work quite well, but that also means double the thrust and even more than double the weight to supportthe two.

To stabilize even a surfboard-sized hovercraft would take one heavy gyro, further reducing lift. An ideal shape is a "golden rectangle" (by the "GoldenMean" of a rectangle 13x21 or an equivalent L/W ratio of about 1.61904:1). Pythagoras had something right, even if he didn't fully understand it'sremarkable scientific relevance. An aerial view of an actual military hovercraft shows how close to a golden rectangle it's footprint is, accounting forit's stability.

carpe_noctem says: Jul 30, 2008. 8:15 PM REPLYPS

SKATE AND/OR DESTROY!!!!!!!!!

dbc1218 says: May 29, 2008. 6:08 PM REPLYSmaller can be done, check out universalhovercraft.com A gyroscopic stabilizer sounds a little over the top but if you want one do it.

pindalanderz says: Jul 28, 2008. 9:55 AM REPLYfor the skirt why not use an inner tube for a tractor tire?

Darth_Reese says: Jul 22, 2008. 1:24 PM REPLYThe mithbusters made two hovercrafts.

minerug says: Jul 21, 2008. 6:21 AM REPLYThe tv show "I didn't know that" made a hover craft with just a bit or plywood, plastics sheeting and a garden leaf blower. It still hovered when it had an adulton it. Nice work though

1up says: Jul 20, 2008. 9:41 PM REPLYWhere did you get the horizontal shaft engine for the thrust? I've been wanting to make a go-kart and I need an engine with a horizontal shaft.

TheMadScientist says: Jul 17, 2008. 6:12 AM REPLYthats really excessive. the air cushon should have a far larger hole, or the back WILL drag.

Thornburg says: Jun 25, 2008. 8:55 PM REPLYIs it me or is Instructables featuring a lot of older Instructables. Like this one was posted in March of '06.


Da_Fudge says: Jun 26, 2008. 5:39 AM REPLYI was thinking the same thing.

Thornburg says: Jun 26, 2008. 8:59 AM REPLYWell it is kinda nice considering alot of them are pretty cool. I just thought I'd throw that out there.

Da_Fudge says: Jun 28, 2008. 4:09 PM REPLYI didn't mean that in a bad way, I was just saying. sorry if I caused any offense.

Thornburg says: Jun 28, 2008. 7:53 PM REPLYOh no, just trying to clarify. Your fine.

dbc1218 says: Jun 26, 2008. 5:18 PM REPLYI certainly appreciate it. This was one of the first 700 or so instructables posted and who knows how many there are now. I just found out thenewsletter goes out to over 160,000 people so the site is definitely growing by leaps and bounds. I think the day of instructables being groupedwith Google and YouTube is coming soon.

Da_Fudge says: Jun 28, 2008. 4:09 PM REPLYWhoa! First 700! That would've been a few years back!

Thornburg says: Jun 26, 2008. 7:03 PM REPLYThat is really something to be proud of. I was here in late months of '06, just it wouldn't let me become a member (honestly). I just used adifferent email and it worked. Anyway good job.

firestormcomputers says: Jul 20, 2008. 8:28 PM REPLYdoes ur name happen to be kyle thornburg?and do you go to freedom high school?

Thornburg says: Jul 21, 2008. 9:16 PM REPLYNo, where is Freedom High located. Never heard of it.

firestormcomputers says: Jul 22, 2008. 12:46 PM REPLYits in Loudoun County VA

Thornburg says: Jul 22, 2008. 1:02 PM REPLYI don't I live any near there, about a 820 miles away.

GWJax says: Jun 28, 2008. 4:26 PM REPLYI've seen a lot of homebuilt hover crafts over the years and with yours the few thinks I would change is putting a seat on it and a protective grill on the back ofthe main thrust blades so hair or other clothing would not get stuck in the blades, as is its a very dangerous setup but it looks really cool.

Josh_B says: Jun 25, 2008. 12:53 PM REPLYTook some filtering, but I finally found some used engines on eBay.

3HP Horizontal Engines4HP Vertical Engines

dbc1218 says: Jun 26, 2008. 5:25 PM REPLYKeep in mind my craft was fairly underpowered with these size engines. Check out universalhovercraft.com and the UH-10F for a 10hp single enginehovercraft design. I might try the UH-13P when ever I get the time and money.


looking4ideas says: Jun 26, 2008. 1:56 PM REPLYI made one using a shop vac I live near the coast so i want to make one that will work on deep water can some one test one out and msg me

supersith22 says: Jun 25, 2008. 4:14 PM REPLYVery nice instructable, I once made one of these but it was round and had no motor on the back.

I_am_Canadian says: Jun 25, 2008. 12:59 PM REPLYI need a video.

Joel D says: Jun 6, 2008. 8:53 AM REPLYhave you ever been sucked into the fan and then cut urself.

Kendallkip says: Jun 21, 2008. 10:22 PM REPLYhave you?

dbc1218 says: Jun 23, 2008. 2:40 PM REPLYNo, I never got hurt riding this craft, but I could have. Looking back, this was the most dangerous thing I've ever built and had a very high potential todo some serious damage. IF ANYONE IS PLANNING TO BUILD ANY THING LIKE THIS PLEASE ADD PROPER GUARDING.

finnster says: Jun 8, 2008. 1:00 PM REPLYdo you by any chance live in kalamazoo??????????

Joel D says: Jun 9, 2008. 4:56 PM REPLYi got my carcasses to power my fan from kalamazoo

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Hovercraft LARGE