Fractional Rigs… Good bad or indifferent...

[Breizh]

Hi All,

I am interested in the views of the forum users as to what they think of, know about, fractional rigging…

We are looking at a GK24 which has a fractional rig, not really sure what the real benefits are, so looking for all your collective knowledge of such things…


Thanks in advance…

Breizh.

 

[30boat]

Fractional rigs are more tweakable than masthead ones.The mast can be bent to flatten the main delaying the need for reefing.The genoa ,being small,is easier to handle than on a masthead rig(same goes for the spinnaker).On the minus side if the rig has backswept spreaders the main will rub against them on a run .If the spreaders are straight then runners are needed to support the mast.The rig is also more difficult to set up than a masthead rig requiring higher tensions,typically up to 25% of the breaking strength of the wire(shrouds) as opposed to 10/15% on a masthead rig.

 

[langstonelayabout]

Fractional rigs are more tweakable than masthead ones.The mast can be bent to flatten the main delaying the need for reefing.The genoa ,being small,is easier to handle than on a masthead rig(same goes for the spinnaker).On the minus side if the rig has backswept spreaders the main will rub against them on a run .If the spreaders are straight then runners are needed to support the mast.The rig is also more difficult to set up than a masthead rig requiring higher tensions,typically up to 25% of the breaking strength of the wire(shrouds) as opposed to 10/15% on a masthead rig.

+1

And as the owner of a masthead rigged boat I'm pleased to confirm that I'd always prefer a fractional rig...

 

[Breizh]

So does that fact that the genoa is smaller mean that the speed would be slower?

 

[boguing]

So does that fact that the genoa is smaller mean that the speed would be slower?

Nope, the main is bigger. And is not sheeted so close to the centre - big +.

The only way that I'd go back to masthead rig is one with the mast much further forward. Small headsails and easy to trim big mains make life so much easier. I call these 'masthead fractional'. Obv. you can't just move the mast, it needs to be designed that way!

 

[saltylegs]

Many moons ago I was looking for a GK24 and compared quite a few, the fractional was always considered faster and easier to handle single handed and tended to be the choice of racers, as such a lot had an outboard as standard when most of the masthead versions had the inboard option.
My preferred choice would be the fractional rig.
Best of luck.

 

[Slowtack]

If you like optimising the boat (whether for cruising,racing or both) and tweaking the rig and enjoy that aspect of sailing go for fractional imho. My current and previous boats were fractional. The larger main + smaller headsail configuration also suits for cruising where I am frequently single or short handed.

 

[Breizh]

Thank you guy's, thats very helpful information.

So the follow on question I guess is, are they usually the same cost to replace as mast head sails? I know there are a lot of permutations but just on average?

Breizh.

 

[johnalison]

I believe that the superiority of a fractional rig was demonstrated back in the 30s on model yachts - ie for a given sail area, a fractional rig is faster. The masthead rig became popular for cruisers around the 60s as the boat could carry more sail lower. The problem of managing a large jib was invariably managed by changing hanked-on sails to smaller sails in higher winds.

The advent of furling jibs and easier mainsail management has changed the cruiser's priorities and a modern cruiser with more beam aft and a fractional rig is actually easier for a short-handed crew to cope with than smaller boats from the '70s with masthead rigs. There is nothing wrong with a good boat with masthead rig and I would probably choose one if I were doing blue water sailing, just that a fractional rig gives better value to many of us.

 

[Twister_Ken]

The battle is lost, and the masthead rig lost it. A substantial majority of new boats are now supplied fractional, and the size of the genoa is slowly diminishing - less than 110% now seems to be the norm on new designs.

 

[boguing]

So the follow on question I guess is, are they usually the same cost to replace as mast head sails? I know there are a lot of permutations but just on average?

Breizh.

I'd hazard a guess at the cost of a main and a rolling fronts'l being roughly equal. A full suit would be a little less for fractional, less cloth per white sail and spinnakers.

 

[charles_reed]

So does that fact that the genoa is smaller mean that the speed would be slower?

On the contrary - fractional rigs will usually tack through smaller angles and be faster off the wind than masthead rigged boats - that's why nearly all pure racing machines are fractionally rigged. Their masts are usually farther forward and their mains considerably larger that with masthead rigs.

However they do require far higher rigging loads and, if you've seen a fractional rig with full mast-bend working to windward in a blow you may note that the leeward caps and inters are loose and flapping. For that reason (amongst others) fractional rigs aren't such a good idea for solid offshore cruising boats.
Most have 22.5 degree rake on their spreaders (the backstay only induces mast-bend) and you need to tack downwind or fly a spinnaker, and the spreader-ends work havoc on the main, even with wear-patches and spreader end-protection.

I speak from bitter experience having had a fatigue fracture in a 10-year old 3/4 rigged mast.

Masthead rigs (IMHO) only became popular as a gesture apeing ORC rule boats where mainsail area was more heavily penalised than foresail area. Both traditional and modern designs have favoured fractional rigs.
If interested, Marchaj's classic book is an illuminating read, if a trifle mathematically demanding.

 

[charles_reed]

Thank you guy's, thats very helpful information.

So the follow on question I guess is, are they usually the same cost to replace as mast head sails? I know there are a lot of permutations but just on average?

Breizh.

Masthead rigs are usually slightly cheaper to re-canvass than fractional boats - two reasons: a mainsail is rather more complex and requires more work than a comparable area of foresail and, usually, there's less sail-area in a comparable masthead rigged boat.

Two, hard earned tips, avoid cross-cut genoas and seriously consider fully-battened mains.
I'm afraid both add a lot to the costs of re-canvassing a boat, but both give longer life and more satisfactory sailing performance.

 

[prv]

if you've seen a fractional rig with full mast-bend working to windward in a blow you may note that the leeward caps and inters are loose and flapping.

Really? I'm new to owning a modern fractional rig (previous was a stout wooden pole on a gaffer) but one of the nuggets of information I've picked up is that a slack leeward shroud is acceptable on a masthead boat but is dangerous on a fractional. Certainly my leeward capshroud (set up by the riggers, as I wouldn't claim to know better at this point) remains tight even when well heeled over. The leeward lower does get a little soft, but nothing like the slack I've seen in old charter boats, which were probably masthead rigged given their age.

I speak from bitter experience having had a fatigue fracture in a 10-year old 3/4 rigged mast.

Could this be related?

Pete

 

[Twister_Ken]

Really? I'm new to owning a modern fractional rig (previous was a stout wooden pole on a gaffer) but one of the nuggets of information I've picked up is that a slack leeward shroud is acceptable on a masthead boat but is dangerous on a fractional. Certainly my leeward capshroud (set up by the riggers, as I wouldn't claim to know better at this point) remains tight even when well heeled over. The leeward lower does get a little soft, but nothing like the slack I've seen in old charter boats, which were probably masthead rigged given their age.


Pete

Ditto, flappy rigging isn't a great idea on any modern boat.

 

[Simondjuk]

If the leeward shrouds on a fractional rig with swept spreaders are going slack, the rig isn't property set up, the mast will be more prone to pumping and tend to rotate around the windward shroud, subjecting to spar to twisting loads. Both are likely to encourage fatigue failures.

 

[charles_reed]

Not really, the fatigue fracture was due to mast pumping and down to too small a X-section area.

I did make the point that when you put on full mast bend...
If you think about it with a swept spreader rig, if you put aft pressure using the backstay, you are taking some of the load off the caps. Do caps up too tight and you immediately start distorting the hull

Ask any rigger.

 

[prv]

If you think about it with a swept spreader rig, if you put aft pressure using the backstay, you are taking some of the load off the caps.

That may in fact be true, but it's not intrinsically obvious "if I think about it". In my head, the point where the capshrouds and the forestay meet is fixed in space. By pulling the masthead backwards above that point, I push the middle of the mast, below it, forwards. The tripod of shrouds and forestay remains the same.

Pete

 

[boguing]

They shouldn't blow about in the wind, but should also not be expected to be anything like tight.

We had an owner who eliminated all the lee slack. That was not enough, apparently. Sail in breeze, tighten, tack repeat. Then repeat with spanners.

Nigh on 50 years ago. when I was 7/8, the American 'Mad' comic did a one page strip on this, with the mast eventually escaping through the hull. Funnily enough, it was another ten years before I ever set foot on a sailing boat and never forgot it.

Ripped out the chainplate sub structure (massively glassed in grp and s/s structure).

Strangely, he couldn't find the bottle screws when we turned up to look at it.

To prove that the boat was as stong as designed, we picked onother (33) up by one chainplate alone. No problem, and case dismissed.

 

[Daydream believer]

However they do require far higher rigging loads and, if you've seen a fractional rig with full mast-bend working to windward in a blow you may note that the leeward caps and inters are loose and flapping. For that reason (amongst others) fractional rigs aren't such a good idea for solid offshore cruising boats.
.

Leeward shrouds on my fractional rigged boat do not flap & I would be concerned if they did.I did have mine too slack once & the mast could be seen inverting in high winds when the main was allowed to flap for a short while
As others have said fractional allows greater tweaking options.
As to sail cost the area of sail may well be the same, so price per M2 should balance out

However, I suspect that for serious ocean sailing a masthead may be better if , for instance, like some Halbergs the lower rigging goes forward as well as aft giving a secure support all round. In addition I would suspect it would be easier to have a cutter rig allowing storm ( or smaller) sails to be carried . I know some fractionals have inner forward forestays fitted ( often by the owners to prevent inversion)but i suspect that they may put stresses on the mast where not designed.
But the OP was talking about a GK 24 & that is not an ocean cruiser but an excellent " shorter trip " little yacht that performs well for its year of design & purpose