Advice please

[monkey992]

Hi my name is sean,
I'm doing a GCSE electronics prodject, in which i will build a surfboard speedometer. Is there any advice you can give me on what would work well/ how you would do it? Greatly aprieciate any relys. Thanks
Sean

[GowerCharger]

the only way i can imagine it would work would be gps based, although i dont know if gps is accurate enough. If you did it using an impellor or something it would cause drag and most people wouldnt want that.

Isnt that a bit complicated for gcse? its a long time since i was in school but we did much much simpler things than that for our gsce electronics (i made a digital code door lock iirc)

[cj]

Hi my name is sean,
I'm doing a GCSE electronics prodject, in which i will build a surfboard speedometer. Is there any advice you can give me on what would work well/ how you would do it? Greatly aprieciate any relys. Thanks
Sean

If you figure it out, I want one.

The only thing I can think of is:

What do they use on boats to make the speedometers work?

Good invention idea though, I think a lot of people would want one if they weren't too expensive, and didn't get in the way or cause the board to drag. What in the hell were you smoking when you came up with this idea? it sounds like it might be a winner, I can see the infommercial now.

[LeeC]

This seems a bit complicated for GCSE but maybe you could build it the same way as an airplane's speedometer...



ll
ll < stopper (moves up or down)
ll
ll
ll
======= << << <<--- Air going into tube this way as airplane is going this way >>
^tube^

Sorry for the crap diagram but basically the air rushes into a tube with open ends, one is aimed in the direction of travel (ie.towards the front of the plane). There is a small stopper in the tube which moves up as air moves into the tube and pushes it up.

The faster the plane is going, the faster the air will be going into the tube. The faster the air going into the tube, the further up the tube the stopper is pushed.

This stopper is conected to a lever which moves the speed gauge, so as the stopper moves up or down the tube, the arrow on the speed gauge moves around, indicating the speed of the plane through the air. This is called the indicated airspeed (IAS). This might not be the actual speed of the plane, however... but why not?

... think about this: A plane is parked on the ground (stationary) and is pointing into the wind which is blowing at 5mph. The air is going into the tube at 5mph, and the stopper moves up, and the arrow on the speed gauge indicates that the plane is moving at 5mph. But really it is stationary (at 0 mph)! The real airspeed (0mph) is called the actual airspeed.

You can apply this to the surfboard, if there is a current of 5mph going north and your board is moving into it at 10mph going south, this type of speed gauge will think that you are only doing 5mph, which is incorrect. I'm not sure how complex and accurate this needs to be, but maybe its something to write down in your evaluation as something to improve on.
(BTW these are complex pieces of equipment, because of the complexities of fluid dynamics and stuff like that, the tube needs to be the right size, shape, and design so that the airspeed is indicated as accurately as possible)

The principle is the same for your project, except the tube will be attached to the surfboard instead of a plane and it will be travelling through water, not air (duh!)

The proper name for the tube is the 'pitot tube', google it or look on wikipedia there will be much better explainations than mine I'm sure.

Your main problem would be connecting the stopper to the speedometer. I suppose you can't do it mechanically, you will need sensors to determine the position of the stopper and some connection to a digital speed display.

If you have any more questions just ask, I'm sure there are other ways of building a surf speedometer, but this is the simplest I can think of right now. Good luck!

[surferdude_scarborough]

ask roy. nuff said.

[parrysurf]

Try a boat set up. Little wheel wont offer much drag. All parts easy to get

[monkey992]

thanks for all the advice. Youre a great help.sean