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    Posted: 01 Apr 20 at 3:38pm
Originally posted by JimC

Hang on Rupert, you're surely not suggesting people should get some evidence instead of speculating wildly without any?

It should, I hope, be obvious that a very small variation at the pot will make for a larger variation at the tip, and that because of the multiplication effect wear in the various components will also have a significant effect.
It might be interesting to measure say 10 each of new Toppers, Aeros and Lasers to see how much they vary, and repeat the exercise with 10 of each well used examples... I'm willing to bet, though, that no-one will actually do it!

if they could stick them on the weighing scales at the same time that would be eye-opening too for sure  Wink
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 20 at 3:26pm
Hang on Rupert, you're surely not suggesting people should get some evidence instead of speculating wildly without any?

It should, I hope, be obvious that a very small variation at the pot will make for a larger variation at the tip, and that because of the multiplication effect wear in the various components will also have a significant effect.
It might be interesting to measure say 10 each of new Toppers, Aeros and Lasers to see how much they vary, and repeat the exercise with 10 of each well used examples... I'm willing to bet, though, that no-one will actually do it!


Edited by JimC - 01 Apr 20 at 3:34pm
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Posts: 8956 		Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 20 at 3:05pm
Can someone give an idea of how far out mast tips can be from one another? From that we should be able to work out how many mm the pots are actually.
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The rake of the mast tube will be set in the deck mould, and there could be some variance there, particularly if the mast tube is a seperate part of the mould from the rest of the deck. However I think the bigger risk comes from assembly.

Depending how stiff the deck is prior to joining it would be possible to introduce some variance. Potentially if the mast tube went into the pot at the back edge, and then as it was pushed down the deck moulding slid forward as the gunwhales aligned this could distort the deck moulding giving a different rake than if the deck moulding started at the front and slid back. 

It could be controlled with assembly jigs or with strict procedures but if it just relies on procedures it certainly opens the possibility for variation depending on the workforce.
 




Edited by Granite - 01 Apr 20 at 1:08pm
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 20 at 12:30pm
I dunno folks, I think you're making a storm out of nothing. That the Laser construction is a bit agricultural is no suprise.

The mast rake relative to the deck must be controlled by the deck moulding. That's surely going to be long cured and rigid by the time the deck and hull are joined. As for the mast rake relative to the hull mould, its going to be difficult for that to vary much, because there won't be more than a few mm variance if the two mouldings are going to meet at bow and transom.

So why a great big cup? Think about it. You want to get the pot in the cup first time, its very fiddly to align what you can't see. So a great big pot and its almost impossible to get it wrong. If mast rake varies significantly I would be reasonably confident it was an issue with the deck moulding process.
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Posts: 353 		Post Options Post Options   Quote Riv Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 20 at 11:35am
I have not expressed myself clearly.

The mould builders decided upon a larger diameter cup in the hull than the bottom of the mast pot (looks about 15mm to me)

They did this for a reason. What would the reason be? I can only think that boats were being produced in several moulds all slightly different (+/- 7mm) and this level of tolerance allowed all the hulls and decks to fit and so reduce waste, improving profit.

This means that the fore and aft position of the mast pot was +/- 7mm. Would this make a difference?

To produce Lasers quickly how many moulds were used? 5 hull and 5 deck moulds? Given the horizontal tolerance how accurate were mast pot rake tolerances?

The other option is that the fore and aft measurements were always spot on but the mast pot rake measurement was the one that was out. This I feel is more likely. as it is more difficult to check than the fore and aft position.

On a similar subject who has used the knot method of reducing mast rake on a Laser for windy conditions?
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Posts: 399 		Post Options Post Options   Quote CT249 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 20 at 8:36am
As I understand it, the tolerance around the mast cup in the bottom of the hull is irrelevant.  The mast rake is set by the mast tube, which is held in a jig while it and the deck are being laid up.  The gap between the plywood of the mast cup and the mast tube is filled with bog, and when the hull and deck are brought together the bog can slop around - the mast tube angle is not affected by the mast cup position.

From personal experience the top people (ie world champs and Olympians) in Lasers worry less about production variations than the people in the other SMODs I sail.  I'm not denying that LPE may have problems but that is a problem with one manufacturer, just as the J/24s had problems with Italian manufacturers, RS had a problem with Brazilian (?) manufacture, etc.

I think that Sam is on the money when he notes that it's unlikely that there is only one ideal rake, given the difference in sails, vang power, people, rigs, conditions etc.  I sail way inland and have to dial in far more twist than when on the coast. My arch rival (3 time world Masters champ etc) back in the day used a lot less vang upwind in a breeze than I did.  The top sailors have a very different style than most people so the leach tension that applies to one group is unlikely to be optimum for the other, etc etc etc.


Edited by CT249 - 01 Apr 20 at 8:37am
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Posts: 8956 		Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 20 at 7:19am
The new kicker will have changed the optimum (I'd guess to more upright, as it's now possible to get the boom beyond block to block), and more aggressive squad sailing styles will have altered it too.
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Posts: 403 		Post Options Post Options   Quote GybeFunny Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 20 at 6:56am
Originally posted by Sam.Spoons

Given that mast rake, on boats that can adjust to taste, varies by loads I wonder how the Laser has had an optimum/ideal rake for 40 odd years?
Presumably as it has had the same sail cut and spars for most of those years.


Edited by GybeFunny - 01 Apr 20 at 6:57am
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Posts: 403 		Post Options Post Options   Quote GybeFunny Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 20 at 6:55am
Thanks for sharing that mast step photo, very interesting. My first laser sail number 63k sailed very well but when I upgraded to a 144k boat it was a pig to sail, it screwed up into wind in every gust. I compared the mast rakes and the 144k boat had a considerable amount of extra rake. I have had 2 other boats over the years which had the normal mast rake so in my very limited experience 25% of Lasers are bad, I am certain Ovington can improve that rate!
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