tom kent

1-Dec-10, 05:57 PM

Hi all,

I'm a final year transport design student at Coventry University and for my final project I'm designing a large amphibious transport hovercraft intended to ship supplies to the remote mining sites of Northern Canada.

I understand that this forum is focussed on the recreational/sporting hovercraft and that the design considerations for a vehicle of the size I am proposing are a different kettle of fish compared to the size you are all used to. However, I thought I would throw this out there regardless to see if anyone could help.

I have a copy of "theory & design of air cushion craft" which seems to be a bible of information on the subject of ACV design, however - I am not an engineering student and whilst I have A-level physics under my belt, much of it goes right over my head! As I said, I am doing a design degree and although I have to prove the engineering principles of my concept, I don’t have to specify exact calculations and figures.

A (very brief) initial specification of the vehicle I am proposing is as follows:

Length 20-25 m

Beam 8-10 m

Payload 60 – 80 tonnes

Unloaded weight 80-100 tonnes

Cruising speed 20-40 kts

Range 400-600 km

I have attached an image of a rough CAD packaging model I put together to illustrate my proposal.

5948

I know how to work out cushion pressure (F=M/A) and using a 22.5 m X 9 m vehicle with a All Up Weight (fully loaded) of 180 tonnes I came up with the figure of 888.8 kg/m2 or 8717 pascals.

I also (think) I managed to work out volume flow rate for this craft fully loaded at a hover height of 0.20 m – (I couldn’t find any information regarding hover height for large ACV so I guestimated 20cm?!) and used a simple 22.5 x 9 m rectangle to estimate a length of 63 m for the hover gap, giving it an area of 12.6 m2.

Then to find the escape velocity of the air I used v= SQRT 2 x 8717 / 1.22 = 119.54 m/s

And then for the volume of air lost per sec I used 120 x 12.6 to get a figure of 1512 m3/s

What I don’t know however, Is how to work out how big or fast my lift fans need to be to replace this kind of volume and maintain cushion pressure.

I also don’t know how to work out how much power I need to move this thing at a speed of 20-40 knots as I’m not sure how to consider the friction of the hovercraft’s skirt etc

Any help or pointers anyone could give would be much appreciated!

Thanks,

Tom

I'm a final year transport design student at Coventry University and for my final project I'm designing a large amphibious transport hovercraft intended to ship supplies to the remote mining sites of Northern Canada.

I understand that this forum is focussed on the recreational/sporting hovercraft and that the design considerations for a vehicle of the size I am proposing are a different kettle of fish compared to the size you are all used to. However, I thought I would throw this out there regardless to see if anyone could help.

I have a copy of "theory & design of air cushion craft" which seems to be a bible of information on the subject of ACV design, however - I am not an engineering student and whilst I have A-level physics under my belt, much of it goes right over my head! As I said, I am doing a design degree and although I have to prove the engineering principles of my concept, I don’t have to specify exact calculations and figures.

A (very brief) initial specification of the vehicle I am proposing is as follows:

Length 20-25 m

Beam 8-10 m

Payload 60 – 80 tonnes

Unloaded weight 80-100 tonnes

Cruising speed 20-40 kts

Range 400-600 km

I have attached an image of a rough CAD packaging model I put together to illustrate my proposal.

5948

I know how to work out cushion pressure (F=M/A) and using a 22.5 m X 9 m vehicle with a All Up Weight (fully loaded) of 180 tonnes I came up with the figure of 888.8 kg/m2 or 8717 pascals.

I also (think) I managed to work out volume flow rate for this craft fully loaded at a hover height of 0.20 m – (I couldn’t find any information regarding hover height for large ACV so I guestimated 20cm?!) and used a simple 22.5 x 9 m rectangle to estimate a length of 63 m for the hover gap, giving it an area of 12.6 m2.

Then to find the escape velocity of the air I used v= SQRT 2 x 8717 / 1.22 = 119.54 m/s

And then for the volume of air lost per sec I used 120 x 12.6 to get a figure of 1512 m3/s

What I don’t know however, Is how to work out how big or fast my lift fans need to be to replace this kind of volume and maintain cushion pressure.

I also don’t know how to work out how much power I need to move this thing at a speed of 20-40 knots as I’m not sure how to consider the friction of the hovercraft’s skirt etc

Any help or pointers anyone could give would be much appreciated!

Thanks,

Tom