Skiffbug

18ft Skiff mas prod

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Just been on a bit of a trip seeing how much @JulianB responds to these topics, so thought I would introduce one that still confuses me.

Over the past 9 seasons, the mast prod has gone from innovation to must have. But it still confuses me (and some legends I've spoken to).

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On the basic principle, it helps pull the tip of the mast a bit further forward, and the top spreader area further back and so maybe support the mains with larger square-tops. It would undoublty alter what the sail profile should look like from the spreaders up, but I'm still a bit confused how.

Quite unhelpfully, the main on my 18 was designed for the rig without a prod, and that has been subsequently added. So now it feels like the main profile will always be wrong for the mast.

And lastly, it feels to me that it would make for forestay tension more responsive to vang and mainsheet tension and the prod acts as a bit of a lever. So should this then lock in the style of sailing in which the skipper feathers the boat before the gust, as opposed to the sheet-hand releasing main?

Anythoughts from anyone?

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It also does a heap to control to jib sheet angles and slot, as the head of the jib would normally move aft when you sheet in.

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58 minutes ago, Skiffbug said:

 

On the basic principle, it helps pull the tip of the mast a bit further forward, and the top spreader area further back and so maybe support the mains with larger square-tops. It would undoublty alter what the sail profile should look like from the spreaders up, but I'm still a bit confused how.

Quite unhelpfully, the main on my 18 was designed for the rig without a prod, and that has been subsequently added. So now it feels like the main profile will always be wrong for the mast.

And lastly, it feels to me that it would make for forestay tension more responsive to vang and mainsheet tension and the prod acts as a bit of a lever. So should this then lock in the style of sailing in which the skipper feathers the boat before the gust, as opposed to the sheet-hand releasing main?

Anythoughts from anyone?

Does it pull the tip of the mast forward, or merely reduce the bend of the lower mast.

It strikes me as designed to tension the jib luff against lower mast bend (even it doesn't reduce it - it might be a bit high for that). It looks as though mast bend would lever the prod up and retension the luff (as you might be saying).

I don't see why it would change the feather/ease equation.

But it was something discussed with Julian in this thread 

That equation has always bedeviled me skiff sailing. I was never coached as a junior, so it was quite late I came to the ease, don't luff approach (even though I sent more than a few years down the cheaper end of the 18ft skiff fleet).

It was one advantage of getting deeply involved with the 15's. And of course Julian's dad made a big point of ease don't luff in his last book.

But having coached my own training group in that, one of them goes off and sails a Brisbane 18's and gets told she's not using luffing enough.

I'm still looking to get a nice little precise formula I can blindly apply and teach :rolleyes:

 

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if you are looking for a responce from me on this, proders where initially used to get some seperation of the jib, re the slot and allow for longer jib luffs.

They suposidely want longer jib luff's because they apparently want more sail area because they think they are lacking in power.

Given the early 90's 18teens had 17 ft wings and smaller rigs, certianly smaller sail areas, not sure that premise can be justified.    The modern 18teen, those that I have access to closely, have become very wooden, not very intuative, but they win, so what do I know.

Then again, the Kiwi's have smaller, I would hazzard to suggest, far more efficent rigs and have won the last 3 JJ's, so what would they know!

We have seen this all before and we will see it all again.

Using a prod to stabalise the head of the jib has merit, and if that's what you are trying to do, go for it.

But going more and more yacht like masts on skiffs, is very likely to be corrected, as it has before and as it will be again. 

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On 12/19/2020 at 7:07 PM, Rambler said:

I don't see why it would change the feather/ease equation.

In my way of looking at it, main sheet tension has a strong effect on leech tension, and as you pull on you pull the head of the mast back, and induce more bend on the bottom 2/3 of the mast.

Because the prod is below the main shrouds, it is slightly pushed forward, and slightly angled up by the increased mast bend on the top 3rd. These two motions push the prod against the forestay, and so you get the levering action I was talking about.

 

18 hours ago, JulianB said:

But going more and more yacht like masts on skiffs, is very likely to be corrected, as it has before and as it will be again.

It may well be a matter of 'fashion', plus the way the back of the fleet works. The top guys have, and so there must be a performance benefit. But even if the back-fleeters don't think so, they inherit the top fleet's second hand sails, and so get jibs designed for prods.

Thanks for your response, Julian.

I agree the boats currently feel very wooden. You can tell how quickly those big rigs look overpowered and the main starts inverting.

Maybe there is just a much tighter groove in which it works, but I always think that crew skill in driving the boat trumps most of those tiny changes.

 

On new 'fashions', we are now also seeing single spreader big rig masts. After reading Higher Performance Sailing, it seemed to me that this took away from the automatic aspect of the rigs. But of course now they have fully adjustable shroud tensions with the new drums, so perhaps yet another step towards needing to be highly skilled to make these things move.

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I think that the most advanced setups in the fleet now are way more efficient than you guys believe.

This is apparent from the range of both rigs extending, Tech 2 (now) and Honda last year were good to 16 tws with the big rig.

Tech 2 is ok to almost 30 with the small rig. The well tuned square top is a good bit of kit.

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