Rig setup and optimisation

[nrcoyle]

I have a new to me (1984 vintage) beneteau first 24.

I am trying to understand and optimise this rig type to get the best performance from the boat. I suspect in reality it really needs a new suite of sails, but I would like to see what I can do with the existing setup until finances allow an upgrade.

My problem is that I am struggling to find any guides appropriate to the rig setup, as it seems a little unusual. The rig is a 9/10 fractional rig, but the spreaders are netural rather than swept back and the lower and upper shrouds are in line with the mast. Therefore any bend in the mast, as well as tension in the forestay comes from the adjustable backstay, this has a block to give a 8-1 mechanical advantage.

Can anyone point me to any references where I will be able to read more about this setup and get a pointer as to what I should be looking at in terms of shroud tension and backstay forestay lengths/tensions to get the best performance. I suspect at the moment that I have too much sag in the forestay but am not really sure if it needs to be shortened, or if the backstay tension just needs to be increased.

 

[VicS]

This Selden Masts pdf is well worth down loading, saving and reading

http://www.seldenmast.com/files/595-540-E.pdf

 

[nrcoyle]

Hi Vic,

Thanks for the reply, I had found and read the Selden guide, unfortunately informative as it is none of the rigs described in it are the same as my setup. In fact this is the case with all the references I found which is why I am scratching my head a bit trying to understand the best setup in my case.

Neil

 

[nrcoyle]

Hi Vic,

Thanks for the reply, I had found and read the Selden guide, unfortunately informative as it is none of the rigs described in it are the same as my setup. In fact this is the case with all the references I found which is why I am scratching my head a bit trying to understand the best setup in my case.

Neil

 

[William_H]

I would suggest that a 9/10 fractional rig is close enough to a mast head rig in that you are not going to get much mast bend of the backstay against the forestay. If it does not have an inner forestay and spreaders and shrouds are square and abeam the mast then the mast must be of sufficient stiffness in fore and aft dimension to not need central support /location. ie straight mast when looking from the side. That means that your only adjustment will be lateral making the mast straight when looking from the front by adjusting the ratio of tension intermediate to cap shrouds. Give it a decent amount of tension although I don't advocate for the 15% of ultimate wire strength that many advocate. Just adjust ie increase the tension of the back stay with stronger winds but keep a bit of tension on back stay at all times. The added tension will straighten the forestay when under a lot of load which takes out camber of the jib. good luck olewill

 

[Daydream believer]

Does the backstay go straight to the masthead or to a crane ( extending out the back of the mast)
If there is a crane this will help apply bend to the mast to flatten the main sail to windward in higher winds although it will not tighten the forestay as much as you might want
Suggest you put a knot in the end of the backstay adjusting cord. If it ran through the block & you lost the backstay things could be embarrassing to say the least

 

[nrcoyle]

Thanks all for the advice, the backstay does go to a crane approximately 200mm behind the centreline of the mast as Daydream suggests, I am still playing with tension to see the effect on flattening the main and reducing sag on the genoa, but I haven;t yet been out in a sufficient range of conditions to really get a feel for the best settings for the backstay.

Thankfully the backstay adjuster pulls one side of a V of wire which is complete so should I lose the adjuster I will still have the backstay at its longest length so no risk of the potential embarrassment that daydream warns of, having said that I am sure I am able to embarrass myself in a multitude of other ways.

 

[Concerto]

Have a look at this document from Kemp Sails for fractional rigs. It should help.
http://www.kempsails.com/technical-data/18-tuning-fractional-rigs/file.html

 

[Laurie]

I have a new to me (1984 vintage) beneteau first 24.

I am trying to understand and optimise this rig type to get the best performance from the boat. I suspect in reality it really needs a new suite of sails, but I would like to see what I can do with the existing setup until finances allow an upgrade.

My problem is that I am struggling to find any guides appropriate to the rig setup, as it seems a little unusual. The rig is a 9/10 fractional rig, but the spreaders are netural rather than swept back and the lower and upper shrouds are in line with the mast. Therefore any bend in the mast, as well as tension in the forestay comes from the adjustable backstay, this has a block to give a 8-1 mechanical advantage.

Can anyone point me to any references where I will be able to read more about this setup and get a pointer as to what I should be looking at in terms of shroud tension and backstay forestay lengths/tensions to get the best performance. I suspect at the moment that I have too much sag in the forestay but am not really sure if it needs to be shortened, or if the backstay tension just needs t be increased.

If still looking and want to email me direct (laurie@lmilton.co.uk)I'll send you a very simple guide to set up/tune a fractional rig.
Laurie

 

[nrcoyle]

Thanks for the offer Laurie PM sent

 

[Laurie]

Thanks for the offer Laurie PM sent

Hopefully you should have received stuff? Shout if you have any questions,
All the best,

Laurie

 

[savageseadog]

I would suggest that a 9/10 fractional rig is close enough to a mast head rig in that you are not going to get much mast bend of the backstay against the forestay.

A common misconception. As the backstay is tightened, even on masthead rigs, the mast will bend in compression.

 

[Laurie]

Indeed.
Masthead rigs with SWEPT spreaders should be set up like stiffer or slightly less bendy versions of fractional rigs.............

 

[Salty John]

This isn't the manual for your boat but the rig appears to be very similar so the comments on set up may be appropriate;
http://www.beneteau235.com/tech/Beneteau_First_235_Owners_Manual.pdf