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Post by Longy on Nov 18, 2005 13:34:00 GMT
Im sorting a new luge out this week, what i need to know is how everybody elses body pan sits in relation to the truck axles, above, same height or above the axle. Cheers.
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Post by Joel on Nov 18, 2005 14:31:38 GMT
Hia dude Not 100% where mine sits, but I reckon about on the axle is the right place. Obviously how high you place the pan affects the handling and stability. So here’s some theory: Placing the pan above where the truck pivots will cause it to lean over and into the corner. As the distance between the edge of the pan and the pivot is longer than if the pan were level with the pivot you will also have more leverage on the board making it turn in quicker and harder, also helping this will be the higher centre of gravity. On the down side the board will be inherently unstable, so on straits at speed it will be prone to wobbles and will take more effort to keep control of. Placing the pan below the pivot will cause the board to lean up and away from the inside of a corner. Again the edge of the pan is further from the pivot than in the level position, however as the pan needs to move down and away from the corner more, rather than less effort is needed to turn the board. This makes the board less responsive and harder to turn, but more stable so on long fast straits. Having the pan at the same level as the pivot is obviously a compromise between the above two. You don’t have to fight the board to turn as it leans into the corner, but isn’t as unstable on the straits. Enough of theory, because when it comes down to it we are only talking a matter of one or two inches. This also doesn’t take the rider into account, a luge is only a few inches tall, put a rider on it and it’s height (and thus centre of gravity) is increased by a massive percentage (more massive in some cases than others. This is what really causes the board to be unstable. So, as I said at the start, placing the pan about level with the axle is about right. Stops the board from being naturally unstable, gives you a good ground clearance, keeps the flow of air under the board as undisturbed as possible. You can always add/remove risers to adjust if you see fit, but you probably won’t need to. Look forward to seeing your new board. Joel
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Post by Longy on Nov 18, 2005 18:32:33 GMT
Thats exactly what i needed cheers mate!
I was thinking of dropping the pan ultra low underneath the axle but was a bit worried about the swingboat effect you can get vis-a-vis landy drop downs, i thought i could get around it by making the pan into a basket type thing. I want to get this luge mega dialled in, Andy (who i met in the eliminators at Dalby blasted off into the distance while i was still farting around on the start line, this luge will be lighter and i'll be faster off the start i hope.
I'll post some pics next week when ive skinned the pan and set the trucks on it.
You know i didnt think wheel size meant much but 69mm Manx's are not a luge wheel (ive sussed that one out) It'll be 83mm flys next.
Joel what do you think about aerodynamics of a luge, is it that important?
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Post by Joel on Nov 19, 2005 10:22:22 GMT
Hia Longy, glad to be of help. Not sure why I do it sometimes, helpin people become faster, guess I like a challenge. You're right about the Manx's, they may be good for stand up, but are just too small for luge. For most courses you will want an 80mm wheel minimum.
I sent an e-mail to Jason A the other day regarding aerodynamics as he was also baffled by the way I disappeared from him at Dalby.
In a sport where there are no engines three things are key, braking, cornering and aerodynamics. Dalby is a long fast course with no corners as such, so the first two become fairly obsolete, leaving aerodynamics and as the major factor to getting down the hill quickly.
There are several things that you can do to make your luge more aerodynamic. Firstly, you can make the underside as smooth as possible. Fairings can be added to the underside, with only small gaps for the wheels, to prevent the air being disturbed and building up as it moves under the luge. Fairings can also be added to the sides and top of the luge at the front and rear to fully enclose the trucks and wheels. This will also allow to be channelled/deflected around the luge in a smooth manner rather than being churned up and causing a lot of turbulence.
Finally you can add an air box/cone behind the head. Your head is the highest point of the luge/rider combination and causes a lot of turbulence. It is, in fact, turbulence behind the luge, rather than an un-aerodynamic front, which slows you more. The air box closes the gap behind the head and reduces the turbulence. The added bonus of this is that it also helps prevent other riders from drafting you as there is less "wake" for them to tuck into.
Now, as mentioned in the above post a luge is only a few inches high, but when you put a rider on it this increases dramatically. No matter how aerodynamic your luge may be if the rider isn't then it is all for nothing. I would probably say that 90% of aerodynamics is in the person and only 10% from the board. To be as aerodynamic as possible you need to concentrate on four things.
Firstly, and most importantly, keep your shoulders as low as possible. Raised shoulders act like a giant spoiler causing a huge amount of turbulence, thus drag, behind you.
Secondly get your head low. As with your shoulders the head causes turbulence behind you, the lower it is, the less turbulence. This is why Wedge helmets are so good, the narrow chin piece allows you to get your head very low and still provides forward vision.
Thirdly are your arms. Build up a good speed on your luge, then spread your arms out so they are nearly 90 degrees to you. You will be amazed how much pressure is on them and how much it will slow you down. This is called "Air Braking" and can be a very useful tool. Keep your arms and hands in as close to your body as possible. I have my elbows slightly bent as it helps get my shoulders lower, but only slightly.
Finally are your legs. Poor leg position will cause a build up of air in front of you causing a barrier and will also cause turbulence up and over your body. Your legs should be extended out in front of you, keeping them low and flat with as little bend in the knees as possible. Your toes should be pointed out and your thighs, knees and feet should be pressed together.
It is with this final point that one of the many advantages of a boomless luge becomes apparent. A boom that is too short will mean that your knees will be bent preventing you from being able to extent your legs and point your feet (a boom that is too long defeats its purpose). The boom it self prevents you from holding your legs and feet together. This causes the air to be channelled up between your legs and gather at your crotch causing a lot of turbulence, a similar effect to air braking with your arms.
A digital camera can be a very useful tool when it comes to improving your tuck. Get your kit on and set up a camera at about ground level facing your luge side on. Set the timer, get on your board and assume your best tuck. You can then look at the photo to see where you can improve. Repeat this from the front to check the front profile. Now, I havn't actually done this yet, but it is something I'm gonna look into to see what a small change can make.
In conclusion, aerodynamics is hugely important, but concentrate on your own aerodynamics before moving on to those of the board. However aerodynamics alone will not make you win, there are the other two key factors mentioned above, braking and cornering, together with an understanding of racing lines and the ability to react to other riders. Together all this adds up to Rider Skill and is more valuable than any equipment that money can buy.
Hope this helps
Joel
P.S. Wow, what an epic. Tom W would be proud
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Post by BOS on Nov 19, 2005 14:33:23 GMT
Joel said 10% board, 90% person which is probably nearly true. But keep in mind you are trying to punch the smallest a hole as possible in the air so by keeping your luge as narrow as possible will help but dont comprimise your moveability. All my luges are really wide, which is good cos its comfy and suits my style but not so good for aerodynamics, hench Joel drafting me at dalby. But hey you need the overall package, luge, bearings, trucks, wheels, aerodynamics, helmet, leathers etc...to be good. And some of these factors may change from place to place, hench different winners at different places (unless your names Pete Elliot)
Ill talk to you soon Longy about wood!
BOS
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Post by Longy on Nov 19, 2005 15:34:43 GMT
Yes, i see now that a bunch of different factors could lead to a faster luge cheers Joel! As somebody has pointed out via pm my waving to every Marshall on the way down the course at Dalby does not help aerodynamics (thanks for that ;D) Now im looking at a different helmet (with visor), tweaking my tuck and finding out how to get my big feet into some type of smaller profile.
Plus im also looking at the kayak i've got stuffed on the garage roof, any idea how those Swiss luges go that are made of fibreglass all ergonomic and curvy??
Ben, im here when you want me mate ;D
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