J2Ski Forum Posts and Replies by AllyG

Only 2 hours to go before the Return of the King (assuming his headache has gone by then, and he's still awake of course) - :wink:

Ally

Lizzie-B,
That's a most impressive display of smileys :D

Well done :thumbup:

You've got such a wide range of smileys there's hardly any need for the text now :wink:

Ally

I'm sure Trencher is right and the skis would normally run fastest when they are flat to the snow. However, some of the new carving skis totally refuse to run in a straight line (I had some like this once) and you do have to slightly make them carve just to keep them running straight (ish).

Friction is a funny thing and it's not directly affected by surface area - just the force pushing the two surfaces together and the coefficient of friction of the materials.

However, pressure is affected by surface area as it is equal to the force per unit area. So, I reckon that the pressure on the snow would be much greater when the skis are on their edges as compared with when they are on their flats, and that this pressure would be too much for the snow which would give way and hence greatly increase the friction between the ski and the snow and slow you down.

I might be wrong, of course, but this is what I reckon happens.

Ally

Snapzzz wrote: ... and a little sick

Well, I hope it all landed in a bucket or similiar receptacle :wink:

You two are a total disgrace :wink:

Just look at me this morning - the pinnacle of respectability - all dressed up complete with jewellery and perfume etc. and off with my husband to our local Catholic church to become godparents :lol:

Luckily, I think it's only the baby we have to promise to bring up in a Christian manner - not all the reprobates here on J2Ski :lol:

Ally

I'm not surprised Iceman, if you were drunk last night. I hope you didn't make any er ... mess ... anywhere :wink:

I have no personal experience of such things, but I have had to clean up after my younger daughter when she's spent too long in the 'thinking place' :lol:

I hope your head has recovered by tomorrow, to think up some new Wibble :D

Ally

Have a great time everyone who's off ski-ing next week :D

And remember to make notes of interesting facts about the resorts so you can tell us all about them when you get back.

Ally

Thanks for the video Trencher :D

I found it very helpful as because it's in slow motion you can see how the skier moves up and down and leans towards the centre of the turn. As far as I can see he's in his most upright position when the skis are flat, then he starts to put them on edge and leans into the turn, then he moves back towards a more central position as the edge decreases (but still with his legs bent), then he moves up nearly to the upright position as the skis run flat on the snow and then he does the same thing again only leaning the other way.

Any ideas? Have I got this wrong?

Presumably it's the edging of the skis and the leaning which is increasing the friction on the snow which is providing the centripetal force and stopping him from just going in a straight line and allowing the skis to make a circular motion as they're designed to do.

It's a long time since I studied any physics but this seems to explain it quite well:

http://www.physicsclassroom.com/class/circles/u6l2c.cfm

I know from trying this myself, that the more you lean the tighter the circle/turn you can make (within reason of course).

What is puzzling me is that the PhD thesis article on selecting the best line through a slalom course doesn't mention centripetal force, only ground reaction forces, snow resistance, wind drag, and gravity.

Anyone got any thoughts on this?

Ally

Lizzie-B wrote:
Thanks Andy - Hope you have a had a good holiday.

Lizzie-B - I'm glad you've cracked it :D

Well done :thumbup:

How about quotes - have you got those sorted yet? You can either click the quote button or put it in manually using [quote sign for equals user name] text [forward slash quote]. And don't forget to delete the irrelevant stuff or you might end up with a whole page of quotes just for one important sentence.

If anyone likes the smileys and wants Admin to make some more interesting ones for us to use, officially, then they can vote for this using Admin's new feedback button.

Ally