What is the best design for a miniature hovercraft for a race?

[enginelover]

props and engines

am not sure if this info is already up there
but i get my aero modelling supplies from this person called mr eshwar
he is in bangalore pm me for his number if u want it :)
he has props and os engines
but if i were you i would go for a fx .18 or similar which would be more than sufficient
and a standard 6X18 prop would do me think how much does ur model weigh ?
plus don't think too much about motors :)
cause the ones that work are just too expensive and for it u need a battery which will weigh a ton
or u can get a LI-po battery which will burn a hole in your pocket...
either way

 

[Danger]

Mach, as Enginelover pointed out, you have to know what weight of machine you are dealing with before you can even begin to choose your fan.
As for the motor, if it plugs into mains electricity, it isn't 12 volt and probably isn't even DC.

 

[ank_gl]

ok, i am almost done with my hover machine. i used a 50X30 cm sq. wooden sheet(its really light), n had a hole of 5 inch dia punched through it in the centre, n mounted a 12 V dc motor over it with a fan 5" dia n abt 3" pitch. rpm of the motor is lil over 5000, n used PVC sheets for the skirt. hollaaa, system is more than working. now only the propulsion system is left.
the whole thing is about 2 kgs. i ll see if i can put up a pic or some vid of it soon(i left it at my cousin's place, so i ll hav to get it back first)

 

[Danger]

Right on, Ank; that's good news. I look forward to seeing the thing in action.

 

[Gambit]

Hey Ankit..! Great going buddy...!

too bad that i am not able to do anything as of now...I guess my work schedule hates me doing all such things...I literally am not getting enough sleep now-a-days. Extra training hours and all...anyways, Congrats...I woul love to see a picture or two of your hovercraft. Did you use motors or engines? let me know...

 

[Danger]

Guys, I'm kicking myself for not thinking of this sooner.
I've got the perfect way to make a multi-segment double-layer curtain with approximately zero effort. Just attach a bunch of 1 or 2 litre milk bags to the edge of the deck. They're approximately the same material as the poly vapour barrier stuff that I was talking about, and are already the right shape. You can seal them with air inside, or just leave them open.

 

[Gambit]

@Danger

Dont kick yourself too hard...lolzz...

Well, coming to your idea, I can get a 1 litre milk packet but not a 2 litre packet. So, I guess, i might have to make the skirt myself. I just Ankit would reply soon with the pics of his hovercraft...with regards to the lower side of the craft, if it has holes or not.

I get the idea you want to convey, that there will not any holes under the craft, But still, I can't seem to understand if we use a milk packet, how will we provide the outlet for the air to escape and provide lift? I hope you are able to understand my doubt...!

 

[Danger]

if we use a milk packet, how will we provide the outlet for the air to escape and provide lift? I hope you are able to understand my doubt...!

Unfortunately, I still can't understand it. The whole point of the curtain is to prevent the air from escaping; you don't want an outlet. It's the trapped air that provides the lift.

 

[ank_gl]

oh it ll be atlest sunday before i could post the pics. its at my cousin's place.

 

[dopa]

Rc Hovercraft Race @shaastra 2007

Hi friends
SHAASTRA 2007 (IIT MADRAS,INDIA) brings you an opportunity to earn a lot of cash and become famous .
Participate in FIRE n ICE event where you have to make a small hovercraft
and compete with others.

For more information look at the link below
http://www.shaastra.org/n/events/Fire+n+ICE

lots of exciting prizes to be won

 

[kach22i]

For more information look at the link below
http://www.shaastra.org/n/events/Fire+n+ICE

Interesting propeller dopa, can you tell us something about it?

http://www.shaastra.org/images/gallery/images/Hovercraft%20SoE%20propellor.jpg
Hovercraft SoE propellor

 

[dopa]

that pic is of a hovercraft which IIT MADRAS made in SHAASTRA 2005.That was a part of our soe (spirit of engineering)


well here is a chance to make a hovercraft of your own and compete with others
http://www.shaastra.org/n/events/Fire+n+ICE
lots of prizes to be won

 

[Gambit]

Hey ank...! waiting for the pics of your craft buddy ! Make it fast !

 

[ank_gl]

http://img232.imageshack.us/img232/1549/hoverej6.jpg

it is still incomplete. propeller fan is dismounted. have to change the motor, the one i used was kinda slow. overall, it sucks

 

[Gambit]

Nice going Ankit !

Good one there Ankit. But I too think it will be tough job to move the craft forward. Is your hovercraft hovering for sure? or is it just getting inflated and staying that way? Also, did you make any holes on the skirt. I hope you saw the two types of skirts I put the pics on the forum about. I was having doubts about the type of lift from the skirt.

I found a plastic propeller which has only two blades. I wonder if it would be enough. I have been seeing hovercrafts(small rc ones) with circular propellers (fans) for thrust with lot more blades than two. Similar to the fan we have in computers. And I saw that the propeller for the lift has only two blades, still they were working. I could not undertand the differentiation between the two kinds of propellers. Would it make any difference if we use the other kind ?

I would like advice from experienced guys out there to help with the choice of the propellers for both the lift and thrust.

I saw in a website where the hovercrafts are running on ordinary AA size batteries. Is it possible for me use the same batteries and still make my hovercraft move? I was just curious. I hope Danger could throw some light on this aspect. Is there any kind of a thrust calculator similar to the lift calculator you told about?

 

[Danger]

I appreciate the vote of confidence, Gambit, but it was Russ who posted the lift calculator; I just dug up his post and copied the link here. I believe that he was also the one who linked to a fan/propellor formulae site. I'll see if I can find it.

 

[Gambit]

Thanks Danger. I wanted to know if buying the other kind of a propeller would improve its performance. I was just apprehensive about the design. Anyways, which motor do you reccomend for a craft like Ankit's which weighs about 2 kgs. I believe 2 kgs is quite high and we need to put in extra effort to moved to forward know what I mean?

 

[Robin07]

I've read your posts and I'd suggest to use syrofoam, a very light and tuff material, as your board. Use a stiff rubber skirt that you can adhere to the outside edge. If you mount your motor in the center and blow it straight down you'll get the lift, a lot like the old Hoover vacuum cleaner did. This vacuum moved on a cushion of air, no wheels are used. You'll be suprised to find that it doesn't take allot of air to achieve lift. Run a grove on the underside of the syrofoam so that some of the air is directed to the rear of the board and through a hole in the skirt, this will give you forward motion. Redirect the escaping air flow so that so will be able to steer.

With most project that I've been involved with, the key thing to so is plan your project and start building. There's a lot to learn in doing things.

Have fun, my kids had a blast.

robin07

 

[Danger]

That's a difficult question for me. It's a matter of scale. You're talking about a machine that weighs less than the driver's seat on a 'real' hovercraft. The one that I want to build runs a 400hp motor through 2 transmissions for both lift and thrust, and uses variable pitch blades. All of my investigations into hovercraft have been on large military and civilian vehicles such as icebreakers and troop transports. The only one that I've ever actually been a passenger on had 4 turbo-prop engines for thrust; I don't even know what was providing the lift. This is sort of like asking an automotive mechanic how to set up a 1:32 scale RC car.
My best estimate for this model would be to use the blade assembly from a regular household fan and mount it on the motor from a cordless circular saw or drill. You'd probably want at least 2,500 rpm. If a gas motor is called for, I'd go with a 30cc (approx.) from a weed-whacker or chainsaw. This is all just off of the top of my head, though, since I have no practical experience with anything this small. (I really wish that Ceptimus was still around, because he knew this kind of stuff inside-out.)
Sorry that I can't be of more help. Curtain designs and such are pretty much universal, but it's really hard to down-scale propulsion systems.

edit: Sorry, Robin; I wasn't ignoring you. You sneaked in while I was composing this.

 

[ank_gl]

Good one there Ankit. But I too think it will be tough job to move the craft forward. Is your hovercraft hovering for sure? or is it just getting inflated and staying that way? Also, did you make any holes on the skirt. I hope you saw the two types of skirts I put the pics on the forum about. I was having doubts about the type of lift from the skirt.

I found a plastic propeller which has only two blades. I wonder if it would be enough. I have been seeing hovercrafts(small rc ones) with circular propellers (fans) for thrust with lot more blades than two. Similar to the fan we have in computers. And I saw that the propeller for the lift has only two blades, still they were working. I could not undertand the differentiation between the two kinds of propellers. Would it make any difference if we use the other kind ?

I would like advice from experienced guys out there to help with the choice of the propellers for both the lift and thrust.

I saw in a website where the hovercrafts are running on ordinary AA size batteries. Is it possible for me use the same batteries and still make my hovercraft move? I was just curious. I hope Danger could throw some light on this aspect. Is there any kind of a thrust calculator similar to the lift calculator you told about?

not that much nice though.
now to answer your queries...
1. yes, the hover is hovering;)).
2. yup, punched small holes with a paper punch pad. without the holes, fan was sputtering a lot. sputter went a lil down after the holes.

now to the prop. obviously with more no. of blades, you get more lift(ofcourse drag also increases), the fan i am using has 5 blades(i can post a pic if u want)

batteries! there's my problem. i can't find a light enough battery pack for this stuff. those AA batteries just don't have enough juice. honestly i really don't know whether they can move it or not.
i have a 12V, 7.5AmpHr lead acid pack, weighing 1 kg or so. with this supply, it works fine(ofcourse, its NOT onboard). hovers and moves. lil slow but. that's why i am looking for a new propelling motor n prop, but haven't found any yet. actually my college has started so i get only sundays to work
finally, the only problem i am facing is BATTERY. damn you battery

 

[Gambit]

now to the prop. obviously with more no. of blades, you get more lift(ofcourse drag also increases), the fan i am using has 5 blades(i can post a pic if u want)

Yes, a pic would do. it is the same fan used in computers?

batteries! there's my problem. i can't find a light enough battery pack for this stuff. those AA batteries just don't have enough juice. honestly i really don't know whether they can move it or not.
i have a 12V, 7.5AmpHr lead acid pack, weighing 1 kg or so. with this supply, it works fine(ofcourse, its NOT onboard). hovers and moves. lil slow but. that's why i am looking for a new propelling motor n prop, but haven't found any yet. actually my college has started so i get only sundays to work
finally, the only problem i am facing is BATTERY. damn you battery

Yeah, batteries are my problem too. I too am looking around for other alternatives. I wonder, the load a motor would pose to be is too much for a pack of AA size batteries or not. Because all rc hovercrafts i saw online are powered by set of small batteries. Not a single big one.

 

[kach22i]

(1) The one that I want to build runs a 400hp motor through 2 transmissions for both lift and thrust, and uses variable pitch blades. ......(2) The only one that I've ever actually been a passenger on had 4 turbo-prop engines for thrust; I don't even know what was providing the lift.

1. Is this your own original "dream project" or would you build from plans?

2. Sounds like the SRN4, which used to cross the English Channel. The gas turbine engines drove via gearboxes and shafts a centrifugal lift fan below deck and a pivot 21-foot propeller on the roof. I went on the roof of a SRN4 shortly before we crossed, I should of taken up the offer to ride in the pilots cabin up top but felt I should not abandon my wife like that back in first class.

Lots of great SRN-4 pictures here:
http://www.hovercraft-museum.org/

You can post as a guest here if interested in real hovercraft:
http://www.hoverclubofamerica.org/forum/

 

[Danger]

Is this your own original "dream project" or would you build from plans?

I'm designing it from the ground up. Of course, I'll probably never get to actually build it, since I don't buy lottery tickets.
It's to be a fully-enclosed 5-seat vehicle (similar interior to a compact car).

Sounds like the SRN4, which used to cross the English Channel.

That's possible. I was only 11 at the time, and my memory of it is very vague. I could have sworn that there were 4 pylon-mounted engine/prop assemblies on the deck, but I might very well be getting it mixed up with something else. The one thing that I do remember for sure is that it was loud.
This was a special appearance to ferry people up and down the St. Lawrence during Expo '67 in Montreal. I've never thought of it before, but I suppose that some Googling might turn up details. (Perhaps on those sites that you linked to; thanks for those. I can see that I might be spending a fair bit of time checking those out.)

 

[kach22i]

4 pylon-mounted engine/prop assemblies on the deck,...Expo '67 in Montreal.

1. 4-Pylon would be the very large SRN4

2. 1967 in Montreal would have been the SRN6

My dream hovercraft which is partially drawn up on AutoCad (not updated in 2-years) and in 3-foot foam model form would be just over 40 feet long with a pointed bow. Diesel generator to converter to several adjustable pitch ducted fans for thrust and lift. Payload; half is enclosed cabin/people, half is exposed cargo almost pick up truck like.

It's fun to dream. My current craft is a factory built 1989 Scat II HP (10' x 6') with a 35 hp two stroke. I've done many modifications to it, it's a on-going experiment and test bed for the big one.

Link:
http://www.carnuts.us/viewtopic.php?t=446

 

[Danger]

That's a sweet little ride.
I have to leave for work now, but I'll log back in when I get there.

 

[Danger]

My dream hovercraft which is partially drawn up on AutoCad (not updated in 2-years) and in 3-foot foam model form would be just over 40 feet long with a pointed bow.

That's a bit more ambitious than mine. I'm looking at about 16' x 6' with a rounded snout. Cabin inside about 7' x 5'. The engine will be a water-cooled small-block with the radiator in front of the lift fan(s). All of the comfort goodies such as adjustable seats, heater/AC, stereo, etc..
My point of pride about it (if the idea works ) is that it will have precision steering and brakes. Maybe I should refer to it as a hover-car rather than a hovercraft because it's a bit of a hybrid.
There'll be a quadcycle retractable landing gear that can be dropped to below the skirt at the corners. The wheels will be full-castoring with hydraulic brakes. For precision steering, it'll be lowered and use differential braking for control (in conjunction with the rudders). Panic braking will drop the gear instantly with the wheels locked, throw all fans and props into reverse-pitch, and rev up the engine. I wonder if anyone's ever tried that before? Any ideas as to the success of it?

 

[kach22i]

I wonder if anyone's ever tried that before?

Not exactly like that, the reason being that 95% of typical hovercraft operation is done over water (including ice and swampy stuff) or where wheels will not be of any use.

My hovercraft is registered as a "watercraft", and for good reason.

One guy named "Pat" at the HCA is working on some things which are out of mainstream. I'm not sure what he has posted but you can look him up on the site below.

Link:
http://www.hoverclubofamerica.org/forum/

My dream design has an independant bow thruster and reversing buckets at the rear. Getting these things not to slide around goes against their very nature.

The best "controled" small hovercraft I've been in where you can control the skirt drag. The little bit of skirt drag is all it takes in a near frictionless condition (think of a skater hitting rough ice). Look up Sevtec and see the link below.

http://groups.google.com/group/alt....1fc54/bee0c44b588af285?hl=en#bee0c44b588af285

 

[Danger]

My hovercraft is registered as a "watercraft", and for good reason.

Mine will have to be as well, simply because it would be illegal to run it on water otherwise. While the wheels won't do any good on water for steering, the gear itself will have drag-scoops to aid in stopping. Precise steering on water would be by simply shutting down the lift fan and using the rudders or even oars. Most of the stopping in any case would be from the thrust reverse. The lift fan will then suck the thing down onto the surface while the the props try to blow it backwards.
I should point out that when I refer to precision steering I mean dead-slow situations such as getting onto the trailer or navigating a very narrow beach access path, not something like slalom racing. It's not that important anyhow; braking is my main concern. With a hoped-for 100+mph top speed, I want to be able to stop right now.
Thanks again for the additional links.

 

[kach22i]

Danger, I don't know where you live based on your profile, but I strongly urge you to seek out a hovercraft event and get some water spray on you. I don't want to discourage you or talk down to you, I want you get to the most out of your enthusiasm. Put on your "I want to make new friends" hat, attend a rally or event just to talk to people. We are always looking for new members and often enjoy giving rides to strangers.

http://www.hoverclubofamerica.org/Events/index.html

Aug
25-26 Connecticut Hover-In
Meet us Saturday, starting at 9:00am. The first cruise up river leaves at 10:00am sharp. The Bissell Bridge is located in Windsor CT. Of I91 take Exit 35 to 218, and then left onto 159, if you are coming from the North, and Exit 34 if you're coming from the South. The boat launch is at the end of E. Barber St, just follow the boat launch sign when you get to the traffic light.

Aug
25 Lowell Hover-In
Lowell, MI - We will cruise to Grand Rapids. The cruise will be the same as last year going up stream 24 mi. and down stream 29 mi. for a total of 106 mi. Sunday will be an event with prizes.

The only expense will be a $15 camping fee per night. BBQ, hot dogs and a bonfire Saturday night. All are invited to my shop later Sunday. For more details contact Don Bender #1645. (269) 795 3458


Oct
6-7


Maumee River Cruise
Near Toledo, OH - More details coming soon.

Oct
6-7 Big Spring Hover-In
The 29th annual Tennessee Hoverin at the Rural Retreat Campground in Big Spring, TN. Contact Dave & Sherri Galka for more information.

Look up the term "PLOW-IN".

 

[Danger]

Danger, I don't know where you live based on your profile, but I strongly urge you to seek out a hovercraft event and get some water spray on you. I don't want to discourage you or talk down to you, I want you get to the most out of your enthusiasm.

Much appreciated. Unfortunately, I doubt that there's a single hovercraft within 200 miles of me, let alone an 'event'. There are probably a few in the lake areas of BC, but I can't get there. I'm a few miles outside of Calgary, Alberta, Canada. I work 6 days a week (5 if there's a stat holiday), and my wife is on swing shifts, so we really can't leave the area. She can because she has co-workers who will swap shifts, but I'm the only employee here. Can't afford to travel, anyhow.
Even if I had time off to come down and check out a Yank event, and had the bucks, I'm not allowed in the US.

I certainly value any advice/experience that you have to offer. My solution to plough-in might not be practical, so feel free to dissect it mercilessly (as with any of my plans). In the design that I'm thinking of, the curtain is actually of smaller perimeter than the deck, most of the difference coming from the front being set back some 12"-18" from the bow of the hull. I plan to hang strips of tough rubber, such as mud-flap material, from the bow that are just long enough to pass under the bottom edge of the front curtain segments. It's my hope that at high speeds they'll be forced under at an angle and thus act as a boat prow. As a side-benefit, I figure that they'd cut down on abrasion of the curtain on dry land.