Hovercraft!

calumwm · 13 Aug 2010 at 00:48

helloo, i thought i'd stick this on here just to see what response i get

i'm going into upper 6th in september, and one of my subjects is product design. i'm known around school for making the biggest and most unusual projects - and as it's my last chance i thought i'd go out with a bang

hopefully not literally though...

so i've decided to build a HOVERCRAFT! it'll be 8x4ft, and powered by a 250cc yamaha bike engine. the project will start rolling properly in september, but so far i've got a sheet of 1.2m x 2.4m x 2.54cm marine plywood.
the skirt will be made from 2 tractor tyre inner tubes (ext diameter 1.2m, tube width 22cm), with a third chopped from each, and sealed back together in a figure of 8 sort of shape.

i've looked into propellers, and i think a paramotor one is what i'm after - although i'd like one around a metre diameter, but i can't find any :/

at the moment the body will be fibreglass, but i'm considering carbon fibre - it will all depend on my budget - after a bit of research i've been quoted £125 p/m^2 of finished surface.

because of this i'm also after funding for it, so i've sent letters to the likes of boeing, BAe, top gear, urenco, sellafield, and VT aerospace. if anyone has any useful contacts i'd be more than happy to get in touch with them

at this stage i think it could cost anywhere between £500-1000, and i've had £100 sent so far...

on another note, an interesting thing i've found is the 'Hovercraft Act 1968' - in section 4 (3), it says:

Except as otherwise provided by or under this Act or an enactment passed before the date of the passing of this Act, a hovercraft shall not be treated as being a ship, aircraft or motor vehicle for the purposes of any such enactment or any instrument having effect by virtue of any such enactment.

SOURCE

does this mean it will be allowed on roads or not? if it's not treated as a 'motor vehicle' is it governed by other law requirements such as having lights, brakes, ability to steer - all the MOT stuff?

anyhow, i'll be updating this with pictures etc throughout - enjoy! i know i will

Calum

calumwm · 13 Aug 2010 at 10:41

i might be able to get hold of a 450, but a local college is donating it to me - theyre after collaboration between our school and themselves, so i might be able to sort it...

are there any formulae for working that sort of stuff out? so far i've found the skirt pressure needs to be about 0.1psi using force=pressureXarea, so i'm after something that will let me work out the power required.. any suggestions?

i also didnt mention before that just one engine will provide thrust and lift - i'm looking at making a box behind the propeller - half of the air will be used as thrust, and the other half will be channelled into the skirt to lift the craft.

calumwm · 13 Aug 2010 at 11:44

nope, i havent flown/driven one, so it makes it more exciting when it's finished

lol

i have got an RNLI station nearby with a hovercraft, so i'll have a look at that when we get back to school, and ask very nicely for a go

and more engines = more weight, but more power obviously.. grr compromise :/

plus space issues, and weight distribution - it'll probably limit it to one man.
i'll have to ask the college in september, and have a big discussion about it.

at the moment steering will be rudders on the top half of the back of the propeller, and we've been thinking about the one engine doing both tasks - could bevel gears be a feasible way of sorting it? if we can work out the size of the cogs required to provide enough lift, we could work something out so that the prop speed can be changed as you change gears but the lift fan speed would remain constant? i've been warned to stay away from gears, and after typing that i can see why

and a few classmates have mentioned the scrapheap challenge thing, watching it now, 8-9 mins in? they lift off a bit higher than i thought

calumwm · 14 Aug 2010 at 01:00

i thought that too about the PSI, but thats what the formula tells me - and an example was similar, so i'm not sure :S

the weight issue is just going to be improvised i think, and the engine(s) will be as central as possible - and does the air have to be channelled once it's on the underside? doesnt the air spread out until the pressure is constant on the whole underside?

we've looked into swivelling the fan, but i think it will make it more difficult as the engine would have to be attached and moved with it, which would make it quite heavy and difficult to steer :/

rudders are simple i think as they have a few ways of controlling them - i think it could be as simple as steel wires (like bike brake cable), but it would look bad and probably be dangerous having them across the body..

i've also been drawing up a few ideas today, and landing gears popped into my head - its going to have to get around school, and wherever else i take it (without engines occasionally) so i'll have to make a trailer, or wheels for it.
to make sure it definitely does hover and isnt just a fancy go kart, theyd have to be retractable, so is it a good idea? comments?

and as it IS a school project, there are strict things about me doing the work, so the majority of it is up to me - including the design, but thanks for the offer!