Agamemnon - i14 869

an area to discuss dinghy developments
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Ancient Geek
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Re: Agamemnon - i14 869

Post by Ancient Geek »

First of all Ness, yes the mast went up and down (Only a bit) to tension the rigging. Robin Stevenson books have the only pictures I can think of of the set up but there must be plenty elsewhere!
As to restoration, I race modern boats at least modern versions of old designs, any class that is raced will have developed and any boat that has been raced or rescued will have been brought up to date I see no harm in doing that exactly as she would have been if consistantly raced all the time.
I realise some people get their enjoyment from cotton sails wooden masts and leaky boats, myself, I prefer them to work, and not to spend hours drying sails.
What we all agree on get these boats sailing, and enjoy them in your own way, we are thank goodness non of us the same.
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Re: Agamemnon - i14 869

Post by davidh »

Sadly no, the tensions end up transmitting themselves into the hull, one way or another.

You also have to remember that if the boat is to be sailed with a trapeze, then these issues double - make that quadruple for twin trapeze (though in the firefly that is not the big issue of course)

As you increase kicker tensions, one of the 'side effects' is that you also increase compression in the mast. Increasing compression in the mast is transmitted through the mast heel onto the hog (if the mast is deck stepped then this loading goes via the king post).

Somewhere I have a picture of my then 'brand new' Contender, with the mast speared down through the deck and out the bottom of the boat. How did I do that..... too much kicker m'lud!!

So, in the event of dealing with an 'old lady' as I'm sure 869 is, it might be better to use a transom mainsheet system to help keep the leech standing up, would resorting to the sort of boat bending (literally) loadings that we can achieve these days with a modern cascade kicker.

D
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Re: Agamemnon - i14 869

Post by Nessa »

David, I too have learned that lesson the hard way - I destroyed a marauder using exactly that method! So while I won't be going to contender style extremes (I currently use a 32:1) I do need a bit of oomph in there to keep that main under control. I do hope to use the trapeze at some stage, but I do have quite a novice crew who will find the cockpit layout more than a little challenging when it comes to climbing out onto the gunwhales.

I am very much minded to make the boat as up to date as possible while at the same time being aware she is an old boat. Is there any way of guessing/estimating the strength of hull? I am supposing that she was raced pretty hard given that John Prentice seems to be a well known name from her hey day.
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Re: Agamemnon - i14 869

Post by Michael Brigg »

Is there any way of guessing/estimating the strength of hull?
This is surely a bit like trailing your boat. You start out with a "test run" around the block. Check everything is tight and add a few extra ties and then set off, carefully avoiding all the pot holes and drain covers and spending most of your time looking in the rearview mirror.

By the time you arrive you are usually going at 60-70mph on country lanes and have decided that the faster you drive the more it smooths out the bumps.

I think that if the boat flies then the loads on the rig and hull are immediately reduced. It is the cautiously managed hull or for that matter the over heavy crewed one that suffers as rig tension cannot be converted into speed.

On big boats most of the breakages occur in the doldrums where the rig components rub incessantly in the calm slop. Does this apply to dinghies?

The other important factor here is your sails. One of the findings on the sinking of The Marquesa (a boat on the Tall Ships Race) was that the use of modern sails meant that the natural tendency of the rig to spill wind in a squall was lost. The Marquesa was subsequently unable to lose power and was sailed under. (this was compounded by a new higher stern deck house that prevented shipped water from flowing of the swamped deck)

Try starting out with older "softer" sails and introduce less compliant cloth as you get more confident with the hulls capability. I expect the hull will surprise you.
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Re: Agamemnon - i14 869

Post by davidh »

Nessa,

we have something else in common - destroying marauders!
(i've two of those down against my name - both ended up later serving duty as the centrepiece of a viking funeral!). The area under the mast could always be a bit suspect, all the more so if you drove the boat hard. A shame though, for with a few modifications, the Marauder was one of the most 'complete' boats that I've sailed. If you could crack the fore and aft trim equation, the boat tramp away upwind, whilst that classic peter milne aft section made the boat fly downwind. Sadly though the class is no more, though one ot two individual boats are rumoured to remain, these though are scattered far and wide, without any form of a class association to support them.

That's sad, as one of the last Committee members from the Association I'd love to see someone get to grips with the boat. Truly, this is now a 'lost class' in every sense of the word.

But we digress! Ancient geek has it right! The boat is there to be sailed and if changing out a horrid tufnol block or two can make a real difference, then do it.

How about using transom sheeting, but bringing the tail back along the boom to a 'centre' mainsheet turning block and cleat?

D
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Re: Agamemnon - i14 869

Post by ACB »

Sorry to harp on but I still don't get it, in the case of keel stepped masts with the kicker attached to the mast below the deck.

I can easily understand that the shroud and forestay loads resolve into pressure on the mast step and that trapezing will rapidly increase that pressure.

I can understand that in a dinghy luff tension comes from the aftweard lead of the shrouds and from the mainsheet, but I don't see how the kicker could generate forestay tension.

Surely the tension in the kicker resolves into compression in the boom and compression in the section of the mast between kicker attachment and gooseneck, but none of it is reaching the mast step?

Of course, with a deck stepped mast, the compression will go into the king post, so that is a different story.

What am I needing to understand here? (I certainly do need to understand it before getting to grips with the Albacore!)

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Re: Agamemnon - i14 869

Post by Ancient Geek »

To those so young, they do not know, John Prentice (Known as Johny woodbine because of his chain smoking!), (A senior player in the worlds largest licenced betting office - Lloyds of London.) was one of the very best as a racing sailor and a good egg too. He went on from Int' 14's as he got even richer and the 14's ceased to interest him, as they sought to be pieces of athletic kit more suited to a gym rather than a gentlemans conveyance! He had a couple of top flight Ocean Racers and a 6 metre or two all called Battlecry. Sadly he left us a year back.
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Re: Agamemnon - i14 869

Post by alan williams »

Hi Dave
Best thing that could have happened to the Mirror 14, Mudraider. Designed to beat a Hornet never even got close.
Nessa you should find that your 14 hull should easily cope with the rig loads, if the dreaded rot has not set in,as these boats were very well constructed being the Rolls Royce's of the sailing world, they were designed to take crew weights plus 35 stone as they were built before the trapeze was re-introduced I woulld not advise the use a 32-1 kicker too much power and not enough free travel to allow the boom to rise when required.
Have Raced against your boat in the past and she was one of the leading lights in the fleet at that time.
Have Fun.
Regards Alan Williams
Ps if anyone knows where Audacity INT 14 732 I would love to know as I would like to try and get her back. Last local somewhere in S. Wales.
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Re: Agamemnon - i14 869

Post by Rupert »

ACB, cut out a piece of paper in a triangle (sail shaped), and pin it to something with it's bottom rightangled corner. Now pivot it backwards. You will see that a point 2/3 the way up will have moved. Experiment with a ruler, and let us know if the point is nearer or further from another point a jib tack's distance away from your drawing pin! I've never tried this, so you will be enlightening me, too. My guess is that it is further away, so therefore the jib will be tighter. 30 + years in Fireflies tells me it works in real life!
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Re: Agamemnon - i14 869

Post by Nessa »

It's a small world isn't it: Agamemnon's new crew's father is also a Lloyd's Name and a quick phone call reveals he knew Jonny Prentice pretty well....

David, I have in mind exactly the sheeting arrangement you describe. I've used it on lots of boats and it works pretty well in my opinion. I can't afford to upgrade the sails any time soon, so we'll be using those that came with the boat (the spinnaker has a great helmet design on it) and they feel like they will have plenty of give in them - possibly more than we would want.

Does anyone know the ownership history of the boat post-Prentice? I bought her on ebay from a lad oop north who knew nothing about boats and so sold it again once he realised it was too much for him. Where was she last seen sailing, and by whom?

Jonny Woodbine - that explains a few burn marks in the decking then! More urgently, I have noticed some woodworm holes as the epoxy comes away. Does this mean the boat will disintegrate any time now? I will treat them of course, but I am still concerned.

Currently she is in my garage just outside hideous Dunstable if anyone wants to come look, advise, drink coffee etc.
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Re: Agamemnon - i14 869

Post by Michael Brigg »

First of all that Kicking strap on Aggamemnon; 3:1 on the strop to a simple V jammer sounds far too feeble. Perhaps this is just a coarse adjustment that you use when pulling the sail up. Once up and running you would take up the slack in the strop on the 3:1 and then cleat it leaving the 8,16 or 32:1 block/lever/cascade to play with. I found this arrangement very good even on a firefly where there is less slack to take in and usually one might expect a less muscular kicker. Without such an adjustment I find you can be left with yards of cordage tangling up the bottom of the boat, the greater the ratio, the worse the problem.

Secondly about kickers and rig tension/hull strain. I agree it seems odd that a kicker attatched to a mast foot could transfer stress to the hull but its all about Zen philosophy. you know... butterlies in africa triggering hurricanes in america etc.

Try standing a straw on its end and press on the top of it. Under compression it becomes much more bendy, and is more easily made to move.

A mast under sail is being compressed by the forces of rig tension in the windward shroud and the forestay (or jib luff). Tension on the kicking strap may have 2 effects. One is that it causes the boom to be pushed against the goose neck.and moves the mast forward. (The opposite effect to the mast ram.) It also pulls the boom downwards around a point at the attachment of the gooseneck and tightens up the sail cloth along the whole length of the boom, but most noticeably in the leach of the sail. This doesn't just reduce twist in the sail but also depending on the stiffness and cut of the cloth induces a progressive force from goosenek upwards pulling the mast backwards toward the end of the boom. this must in turn be transmitted to the forestay and shroud proportionately depending on your sailing angle.

If you doubt this then I dare you to put full kicker on your rig if you havn't got the jib tensioned up!

In practice of course the forestay cannot lengthen to let the mast go back, so as kicker tension moves the hounds backwards they have to go lower, which is only possible if the mast bends which of course is exactly what it does. Kicker tension induces a prebend which in excess closes the slot which you hoped to open with increased forestay tension. The quick guys seem to know exactly the right balance of jib vs kicker to use but it's something that has always eluded me.
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Re: Agamemnon - i14 869

Post by davidh »

Michael,

Thanks for this!

"Kicker tension induces a prebend"

I'm surprised the definitive statement on the subject came from a medical man, after all, they do not get much call for worrying about the triangulation of forces.

Sadly, the technical aspects of rig loading is one of the things that I'm a bit of an anorak about.

So.... in very simple 'janet and john' terms..................

As you pull on the kicker, you induce a forward 'thrusting' force that acts on the mast through the gooseneck.

(nessa... here's a quick diversion, just for you! Which class that we both know well uses HUGE amounts of kicker?
Now ask which class introduced lower shrouds at the gooseneck height
Case rests!)

Even with a mast ram, or by trying to lock the mast off at deck level, you will start to introduce prebend.

With the mast in a prebent state, you have to now consider the forces at work. The mast wants to return to statis, but cannot. Nor can the mast move upwards, as it is held in tension at the hounds. So, inducing prebend will start to increase rig tension AND will also see an increase in the measured compression forces at the heel plug. To keep every thing in equilibrium, the mast step presents an equal and opposite force upwards. It is this increased force that acts on the hull.

I doubt if many people would remember all this is the 'how it used to be' practical example BUT(appealling to ancient geek now as he is an ex merlin man) there was a time, oh, limited swing spreader era I'd guess, when the number 1 'must have' fitting was a long split pin that went through the holes in the hull fitting for the mast heel and then through the heel itself. The purpose of this was to stop the mast 'lifting out' of the heel fitting - which it would only do when on a broad reach, with the KICKER eased off completly. Come to think of it, Proctor 2532 boom sections spring to mind too. Whatever, to make these rigs work downwind, you had to let the kicker right off - which could then allow the heel to lift. Kicker back on solved the problem, but then you went slowly, capszied, or both!!

Interestingly, the trapeze issue is a completely different set of forces at work. Much of the understanding on this came from work we did when twin trapeze systems suddenly started to appear. Believe it or not, some of the early work on this was done on a 505 rigged with twin wires. A well set up Proctor D section, pretty much bulletproof unless you did something really silly, would go all spagetti like then break when subjected to twin wiring. The mast would go out of column to leeward, closing off the slot, before collpasing completely. Now it is easy to assume that when you're twin wiring it and the windward shroud goes slack, that the rig is not being stressed. Take it from me, having done a lot of work on the subject, that the compression loads in the heel, under those circumstances, are huge!!!!

Michael.... stick to mumps and measles - they're much easier and less of a hassle!

D
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Re: Agamemnon - i14 869

Post by JimC »

In practice though to get the same tension down the leech the same load has got to come from somewhere... Queenie AJB had a low kicker purchase all the time I knew here, so I've retained it. I've discovered that in practice I wham on the main as hard as possible, then take up the slack with the inadequate kicker purchase, so I doubt the practical difference is very great...
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Re: Agamemnon - i14 869

Post by Ancient Geek »

Somehow I don't recall it being as complicated as some posts seem to want to make it, and sorry Davif H Inever used a split pin to hols the mast in, Newton and compression kept it in as it does in my current (Admitedly rather bigger.) boat.
I think the poster before this got it right.
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Re: Agamemnon - i14 869

Post by davidh »

Ancient Geek,

amen to the Kiss comment - spot on.

What noone here has asked is the question of 'what are you trying to do' to the rig that demands either a super powerful kicker.... or a weak one, or any other method of controlling the rig.

An older 14 will have a less than powerful hull, yet a big rig, with a main that carries quite a lot of roach.

The trick surely is to see what needs to be done, then - and only then, to start trying to make changes.

A 14 of this vintage is almost certainly (except inthe lightest of weathers) 'overpowered' and anything that closes up the leech will only make this situation more so.

Then you have to take into account sailing 'style'. Last weekend at the 8.1 nationals, Steve Cockerill used hardly any kicked at all, instead he just graunched in the main and sailed upwind like that - and won.

So - as AC said, KISS.... make sure what you have works - once you've sailed the boat a few times you can then see what else you need to be doing!!

D
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