Lyn Brianne length - anyone know

marv_mcd · Post by **marv_mcd** » Mon Nov 14, 2005 9:23 am

Hiya,
Does anybody know how long the spillway is from the big lip after the flat to the bottom please?
We reckon it's about 350m, in which case given that it took 20s to do the run, that'd put our average speed at 40mph... Surely not?!
No wonder it felt fast :)

boater rich · Post by **boater rich** » Mon Nov 14, 2005 9:33 am

I heard a story that Llandusyl paddlers have had a speed gun on one of their trips down the spill way and they recorded speeds of 50mph+

I would quite easily believe that you could average 40. I take it the stopper at the bottom was manageable, I was there the sunday of the Teifi tour and the stopper looked to be at least 6ft high with a massive towback.

Rich

marv_mcd · Post by **marv_mcd** » Mon Nov 14, 2005 9:42 am

Sweet :)
It was perfect really, not much water going over - sufficient to get on the plane straight away but no wave at the bottom. The end was mad, everyone was just taking off and flying 10-15 metres, skimming or single leaps.

John Leopold · Post by **John Leopold** » Mon Nov 14, 2005 10:18 am

Hate you lot, I have wanted to do the dam for years, and you paddle it when I can't. As I was working overtime at home with 1 year old son to pay for Saturdays access ticket on the Tawe. Oh to be young and single again!!

JIM HEPPY · Post by **JIM HEPPY** » Mon Nov 14, 2005 2:03 pm

Ive just measured the pan view from a good map system and its 315m but this measurement doesnt take in to the fact that it is on a slope.
We were up paddling the Tywi a couple of weeks ago and the resovrior had about six feet before going over the slipway. Due the the size of the res i reckon it will take some rain to fill it up. cheers Jim

JIM HEPPY · Post by **JIM HEPPY** » Mon Nov 14, 2005 2:03 pm

Ive just measured the pan view from a good map system and its 315m but this measurement doesnt take in to the fact that it is on a slope.
We were up paddling the Tywi a couple of weeks ago and the resovrior had about six feet before going over the slipway. Due the the size of the res i reckon it will take some rain to fill it up. cheers Jim

Pete the kayaker · Post by **Pete the kayaker** » Mon Nov 14, 2005 2:13 pm

It had plenty going over the spillway last Wednesdsay (enough to give three of us whiplash!) - so I guess the rain we had did the trick.

marv_mcd · Post by **marv_mcd** » Mon Nov 14, 2005 4:12 pm

Great, thanks Jim.
Is it possible to work out the height drop from your map as well please? If I assume an average 35deg slope then that's about 385 metres of ramp. Crikey :S

conoroneill · Post by **conoroneill** » Mon Nov 14, 2005 8:34 pm

Martin,

The Tourist notice board at the top of the dam says how high it is. If I remember rightly, it is something like 90m.

SANDY0728 · Post by **SANDY0728** » Tue Nov 15, 2005 11:10 am

Somebody must have got a GPS.

Take the height at the top and the height at the bottom (from sea level).

Work out the height difference, use the figure stated above for the length from vertical perspective.

Use your long forgotten Trigonometry skills to work out the length of the face of the slide.

Just don't ask me to work it out!!

Sandy.

Vulch · Post by **Vulch** » Tue Nov 15, 2005 11:25 am

Hmmm. Well kids, Mr Pythagoras reckons that the length of the hypothenuse of a right-angled triangle is equal to the square root of the sum of the length - squared - of the other two sides. So if the data is correct - ie horizontal length of 315m and vertical drop of 90m, the length of the slide should be the square root of 315^2 + 90^2, which equals:

327 metres and 60 of your Earth centimetres (and about 5 mm...).

Trig not required.

20 seconds to do the run...

16.38 metres per second...

so in English,

assuming 1624m to each mile... (so 0.2017 miles in total)

36.31 miles per hour.

Think that's right.

Vulch

Rich P · Post by **Rich P** » Tue Nov 15, 2005 12:29 pm

Come on we must be able to do better than this Vulch is right but that's only an average speed and marv needs to know how fast he hit the stopper at the bottom.

A quick google reveals that

s=0.5(v+u)t where s is distance covered v is the final velocity, u is the initial velocity and t is time so:

327.6=10v

v=32.7m/s i.e. double Vulch's estimate giving a whopping 72 mph

Somehow I suspect something is wrong somewhere either that or I am very surprised that nobody get seriously hurt doing it.

Rich

Ps I will now go back to being a sad Maths geek with no friends except Mr Farmer who as a maths teacher should have done this first !

conoroneill · Post by **conoroneill** » Tue Nov 15, 2005 6:33 pm

I've just put a video clip of this trip onto our club web page. Marv (the person who started this thread) is the third paddler down.

http://www.bristolcanoeclub.org.uk/vide ... ov2005.wmv

Steve B · Post by **Steve B** » Tue Nov 15, 2005 6:55 pm

Magic!!

JamesA · Post by **JamesA** » Tue Nov 15, 2005 7:09 pm

conoroneill wrote:I've just put a video clip of this trip onto our club web page. Marv (the person who started this thread) is the third paddler down.

http://www.bristolcanoeclub.org.uk/vide ... ov2005.wmv

The absolute business. I note everyone had big grins after doing that one!

RichA · Post by **RichA** » Tue Nov 15, 2005 8:37 pm

Rich, you're forgetting the terminal velocity that the boat will reach whilst skimming down the water...I don't know how to do it. Maybe someone will get really bored and work it out!

DaveB · Post by **DaveB** » Wed Nov 16, 2005 3:14 pm

Looking at the video clip the last bloke down seems to take 17 seconds on the descent which increases the speed significantly.

MikeR · Post by **MikeR** » Wed Nov 16, 2005 4:14 pm

RichP,

Sorry, but the equation quoted corresponds to an object free-falling vertically downwards and an absence of wind resistance (and, in this case, boat on concrete resistance!).

I'm afraind 72mph is a little optimistic! Good to see common sense kicked in though and you were sceptical about your answer!

Mike.

Disclaimer: this post is based on me correctly recalling A-level maths from 10 years ago, so may be a load of old bobbins!

JamesA · Post by **JamesA** » Wed Nov 16, 2005 4:36 pm

Hmm, so long does it take for you to get back to the TOP of the dam, if you want to make another attempt?

2 minute drive or more like 15? :)

Patrick Clissold · Post by **Patrick Clissold** » Wed Nov 16, 2005 6:10 pm

Has anybody actully been caught by the dam people and told off before? Every time I'm up there its deserted.

AliceB · Post by **AliceB** » Wed Nov 16, 2005 9:29 pm

Back in the day I was fortunate enough to live only a few miles down the road....

Has anybody actully been caught by the dam people and told off before? Every time I'm up there its deserted.

They use to have quict a scary old man wielding a rather hefty maglite...oh and a rather manky alsatian, but i agree they're not always about.

And, yes they have! not me I hasten to add....run it, it's all good! Lower water is better as, from memory, there can be quite a sticky hole at the bottom in high water (also goes a bit quick!). Also kayak's are better than canoes ;-) learnt that the hard way

Patrick Clissold · Post by **Patrick Clissold** » Wed Nov 16, 2005 11:27 pm

You paddled a Canoe down Llyn Bryanne!? You need to talk to Jon Lovell, im sure he would take up the challenge aswell.

Rich P · Post by **Rich P** » Thu Nov 17, 2005 8:11 am

Mike R wrote

Sorry, but the equation quoted corresponds to an object free-falling vertically downwards and an absence of wind resistance (and, in this case, boat on concrete resistance!).

Sorry your A-level maths is flawed the equation is generic and will work in many situations but requires constant acceleration over the whole time. There are several things wrong the first is that the spillway has a vertical drop at the start followed by a flat bit which probably takes about 20m off the length making it nearer 300. The second is as RichA says:

you're forgetting the terminal velocity that the boat will reach whilst skimming down the water

So if one assumes that all the acceleration happens in the first 5 seconds (not unreasonable) then you get the velocity as about 20.69m/s which is about 45mph a far more reasonable estimate.

Rich

Ps Is this why I spent 12 years at university studying maths ?

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Lyn Brianne length - anyone know

Lyn Brianne length - anyone know

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