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Nice new Laser for Christmas
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JimC View Drop Down
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Topic: Nice new Laser for Christmas
    Posted: 07 Dec 14 at 9:18pm
Originally posted by bustinben

I'd agree with that in principle, but there's an assumption there that the performance penalty for being light in windy conditions is the same as it is for being heavy in light conditions though.

Mmm, but no. Remember its not time that counts but places in fleet racing.
If Sailors A, B, C, D, E finish 1,2,3,4,5 in light air and 5,4,3,2,1 in heavy air they get the same points whether they are 2 secs apart or 20 secs.
lets say that we have 3 sailors, L, M, H.
in light air they finish L, M, H. in heavy air they finish H, M, L. In moderate conditions M wins and L and H are fairly even. Series of 4 races, one light, one strong, two moderate.
L scores 1, 3, 2, 3
H scores 3, 1, 3, 2
M scores 2, 2, 1, 1
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sargesail View Drop Down
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Posts: 1459 		Post Options Post Options   Quote sargesail Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 14 at 9:18pm
Originally posted by JimC

Originally posted by bustinben

P.S. I know I've argued that the published radial "ideal weight" is utter b**locks,

Curiously, in a class which is weight sensitive, when fleet racing the ideal weight to be is smack on the average for the fleet. This may not relate to the weight that's "ideal" to get the boat round a range of courses in the lowest average time. Very counter intuitive but you can do a paper experiment to demonstrate it.

Mean or median?
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Posts: 288 		Post Options Post Options   Quote bustinben Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 14 at 9:30pm
Originally posted by JimC

Originally posted by bustinben

I'd agree with that in principle, but there's an assumption there that the performance penalty for being light in windy conditions is the same as it is for being heavy in light conditions though.

Mmm, but no. Remember its not time that counts but places in fleet racing.
If Sailors A, B, C, D, E finish 1,2,3,4,5 in light air and 5,4,3,2,1 in heavy air they get the same points whether they are 2 secs apart or 20 secs.
lets say that we have 3 sailors, L, M, H.
in light air they finish L, M, H. in heavy air they finish H, M, L. In moderate conditions M wins and L and H are fairly even. Series of 4 races, one light, one strong, two moderate.
L scores 1, 3, 2, 3
H scores 3, 1, 3, 2
M scores 2, 2, 1, 1

Mathematically you are quite right, but that's only if the light airs actually has the effect you're proposing rather than just leveling the playing field.  I think reality is that sailor 1 cannot be beaten by sailor 5 in windy conditions, but sailor 5 can be beaten by sailor 1 in light conditions rather than there being a clear reversal of potential positions.  This is just my perspective on this class of course, other classes may behave differently.
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Posts: 288 		Post Options Post Options   Quote bustinben Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 14 at 9:53pm
Originally posted by Chris 249

Originally posted by bustinben

Originally posted by Chris 249

Originally posted by bustinben

I think all this may be moot anyway in practice - how does LPE or Sailboats.co.uk know what the "optimum mast rake" is?  

Reputational damage to the class aside that is.  

And that notwithstanding the fact that any decent laser sailor knows that the "all boats are the same" thing is utter b**locks anyway.

Dead

Since our Lasers come from a different builder I don't know whether the claim about your Lasers is correct, but where is the objective evidence that there is a discernible speed difference between Lasers today?

In your earlier posts you have disputed claims by other people about Aussie boats being faster, you disputed the claims that the optimal weight range of Radials is narrow, and claimed that the sails were better than others reckon. To be honest IMHO you're right in all of those points, but is there any more or less evidence for the claim that there is significant variation between Lasers than there is for the claims you dispute?

One can feel a difference between Lasers (or THINK one can feel a difference, which is quite a different matter) but finding hard evidence of an actual speed difference in current boats appears to be impossible, unless the boat is actually beaten up or broken. 

Well, the physical differences are readily provable to anybody who cares to check.  I know that they're there because I've measured them myself.  I've got a table of rake measurements from a range of boats, and not only are no two the same, they're in fact all very different.  Anybody who is a member of a club with more than 1 laser can repeat my experiment  Smile

As to whether it actually makes a difference on the racecourse, that's much harder to prove conclusively. Sailing two boats with different rakes does feel different, but can you be sure that one is better than the other?

What you *can* say on this topic if you understand how the laser rig works, is that if you have a mast that is raked 2 inches further back than other, then you have the same leech tension as the forward raked boat if it loosened the traveller or clew strap by the same amount.

A bit of 2 boat tuning in hiking conditions up until you start de-powering significantly will quickly show you what happens if you do that (clue, it's not going to be very fun).

That doesn't help you assess where the limits lie however.  I'm sure there's a point where going further forward will start to disadvantage you.

P.S. I know I've argued that the published radial "ideal weight" is utter b**locks, but I'm not sure I've claimed that it has a wide range?

I understand the effect of rake on leach tension. I just question how much difference the leach tension variation creates. The loose-leach boat may well be faster in situations when you want more twist, such as chop or when there is a lot of wind shear. I know people like to maximise the available range of leach tension, but still wonder whether it is really important (or noticeable) as a factor for the vast majority of sailors.

I've never had a low-profile tiller, for example, but even when I was serious enough to score one of those nice triple-triangle cubes I never noticed a performance gap in fully-blocked conditions, let alone a gap that could be identified as being due to leach tension. I also notice that there's a significant difference in the point in the wind range when fast sailors go block to block; I used to go block to block when my arch rival (3 time world Masters champ) still had about 2" of separation, which seems to indicate that there's not just one ideal leach tension.

As you say, there is a point where going forward will disadvantage you, which indicates that it's all a matter of tradeoffs. I broke the mast base in an old boat and out of interest, tried to stick it back in, but got the mast too upright. The boat appeared to be noticeably quicker downwind, but was a complete dog upwind; in the first championship race after the mast base broke, I amassed as many points as I had counted in the whole of the previous two such titles I'd done.  Dead  Sure, I could get LOTS of leach tension but wow was that slow!

PS; sorry about getting your weight comments wrong; my point was just that you have (correctly IMHO) said that a lot of accepted wisdom about Lasers is wrong, and in the same manner I believe that a lot of the accepted wisdom about leach tension is wrong or over-stated.

No offense taken  Wink I think the lower tiller makes no difference to leech tension, rather than leech tension making no difference.  You can tighten the traveller effectively as much regardless of the tiller, it's just that a non low/stiff tiller then starts to have annoying issues.  Once you get traveller tension up to a given level, and wind speed is above a certain number of knots, then the main blocks are always right out on the corner being pushed down to the eyelet. If you pull on more traveller tension, it's not going to make anything better, ergo, the advantages of the flashy tiller are more ergonomic than anything else.

As for the overall effect of leech tension, it's very hard to know, as you're always prejudiced by what you think is true.  If you think something is slow, it will make you slow.

I don't know whether half an inch in the middle of the range makes a difference.  I do think 2 inches back does, and here's my reasoning:

when you're getting powered up you want to start flattening the sail to reduce power and drag.  If you have a mast that is further forwards, when you go block to block you have bent the mast more (hence the greater leech tension).  This flattens the sail starting at the top because the top section is more bendy than the bottom section.  

If you don't have this forward mast, you have to start pulling on the other sail controls sooner to depower and flatten.  Kicker will bend the lower mast more than the upper (relative to the mainsheet pulling down on the leech), which is the wrong way round from what you want, and pulling on downhaul causes the leech to open and you lose height.

That's my hypothesis.  I'm not sure how to prove it though  LOL
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 14 at 10:41pm
So is it true to say you want the most upright (or even fwd leaning when not tensioned) mast possible on a Laser (within expected tolerance)?

Edit: and is it possible to 'improve' a boat by sticking a wedge in the mast well, assuming no one checks?

Edited by Peaky - 07 Dec 14 at 10:43pm
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jeffers View Drop Down
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Posts: 3048 		Post Options Post Options   Quote jeffers Quote  Post ReplyReply Direct Link To This Post Posted: 08 Dec 14 at 1:37pm
Originally posted by Peaky

So is it true to say you want the most upright (or even fwd leaning when not tensioned) mast possible on a Laser (within expected tolerance)?

Edit: and is it possible to 'improve' a boat by sticking a wedge in the mast well, assuming no one checks?

If someone finds that then you will almost certainly get binned and probably protested under rule 2 or rule 69 (even at club level IMO, that is blatant cheating).
Paul
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jeffers View Drop Down
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Posts: 3048 		Post Options Post Options   Quote jeffers Quote  Post ReplyReply Direct Link To This Post Posted: 08 Dec 14 at 1:43pm
Originally posted by JimC

If my memory serves me correctly the mast rake on the Topper is almost entirely controlled by the deck moulding anyway, but I could easily be wrong.

Correct. But the mast cup does through bolt from the underside of the hull through both mouldings so if the alignment is out it may affect rake a little but probably only by a minimal amount depending on the amount of play in the hole that the bolt goes through.
Paul
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