Masthead or Fractional rig?

Seanick

Seanick

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www.nickgates.co.uk
I am re-rigging a 24' plastic boat for club and maybe quarter ton racing.

I have the masthead rig.

Cost aside, should I stick with the (shorter) masthead rig or change to fractional.

The total sail area stays the same, except possibly the spinnaker.

Finished boat to be IRC rated.

Any thoughts? COST ASIDE!
 
Fractional rig gives you more options for tuning the mainsail through mastbend and allows for smaller, more efficient (and more easily handled) headsails. Downside is that all else being equal you should move the mast forward relative to a masthead, and that may involve major surgery and you'll need runners for maximum tweakiness (ie shorthanded sailing becomes tricky). You'll also probably end up with more fragile spars as they tend to be thinner so the flexibility can be taken advantage of - obviously the risk is that if you do something wrong it's easier to break the mast.

What I'm not sure of is how IRC treats the two if sail area stays constant - my guess is you'll be penalised for the extra tuning ability.
 
If the boat was originally designed for masthead rig, it may be quite expensive to convert because you may need a a new mast step further forward (very costly if the mast is to be keel stepped) and new chain plates.

Having said that, it may bepossible to use the original position but a chat with the designer, or at least a good sail maker and rigger would be needed.

Cost and work apart, IRC favours fractional which is also more tweekable, easier to handle and faster. On a 24 footer, check stays and runners may not be necessary unless you are aiming for the highest echelons.

Masthead rig is the ultimate for strength and security and still best for serious offshore cruising when safety is more important than performance.
 
Mast bend can be induced on a masthead rig as well. Other than that I wouldn't suggest that modification is going to be worth the trouble, I definitely do not recommend.
 
Seanick said:
I am re-rigging a 24' plastic boat for club and maybe quarter ton racing.

I have the masthead rig.

Cost aside, should I stick with the (shorter) masthead rig or change to fractional.

The total sail area stays the same, except possibly the spinnaker.

Finished boat to be IRC rated.

Any thoughts? COST ASIDE!
Click to expand...

Cost asside, go frac for sure. Taller, higher aspect, rigs are more efficient than shorter rigs.
 
Seanick said:
I am re-rigging a 24' plastic boat for club and maybe quarter ton racing.

I have the masthead rig.

Cost aside, should I stick with the (shorter) masthead rig or change to fractional.

The total sail area stays the same, except possibly the spinnaker.

Finished boat to be IRC rated.

Any thoughts? COST ASIDE!
Click to expand...

Sounds like there might be another boat joining the quarter ton circuit!

http://www.quartertonclass.org/
 
I would agree with the fractional rig route if cost doesn't come into it. Wouldn't have thought you necessarily need runners though, but they do give the ultimate control. Whether you need a new mast position would have to be determined by an expert in the end, designer or rigger etc., but I can recommend a Fernhurst book by Ian Nicolson, understanding yacht design, and in that he describes how to determine the centre of effort by graphical means and if you are able to do that for both existing and proposed rigs it will give you an idea if the mast has to be moved before you start paying professional fee's, so may help your decision. As for IRC then I am confused by JJ saying IRC favours fractional rigs perhaps he will come back and expand (please). I did a trial certificate for my previous boat a HB31 with the same sail area, loosing the runners, but the genoa was higher aspect with less overlap which is how all the IRC boats seem to be going. The trial certificate came back the same, so the higher aspect genoa was rated higher because it is more efficient which compensated for the loss of the runners, which wasn't what I was anticipating or hoping The professional designers therefore must be confident that the higher rating is worthwhile in performance. A lot of quarter tonners have changed their rigs must be info out there. Good luck with your decision.
 
The rumour machine I've encountered says IRC penalises fractional rigs. However, whether it penalises them enough to compensate for the lost ability to tune the mainsail is another matter. I would suspect fractional is still better.

IRC definitely penalises runners. You will get a small advantage using runners on a masthead rig but not enough to justify the IRC penalty and the extra complication.

Have you also considered whether you'll be racing in a quarter ton class on scratch rather than IRC? There's no point boosting your competitiveness under IRC only to find you're one of the slowest quarter-tonners around.

Best of luck with it all. I did some half-tonner 'classic' racing and found it competitive racing but with a friendly social scene afterwards.

And when you get sailing remember that there's some tricks to racing old IOR boats that differ from modern racers. On some of them you can gain downwind by going on a dead run with the pole right back and the spinnaker clew eased to the forestay. That would be pretty much heresy on a modern IRC boat. So worth experimenting when you get on the water.
 
I've done exactly that with my 1975 Extension 24 - changed from a masthead rig to fractional. Moving the mast step forward on a boat of that era often isn't necessary if you do away with overlapping genoas - they have a lot of sail area aft of the centre of effort.

In addition, the fashion these days is for a larger sail area than when these boats were built, so a larger rig need not be a problem.

I just put an Etchells rig straight in the boat, with a bit trimmed off the foot so it could be deck stepped. It works fine, providing the mast isn't raked aft too far, although it would be a little better if the rig was slightly smaller - I may trim a little off the top to make it 9/10ths fractional, which would also help the IRC rating.
 
Thanks for all your thoughts so far.

The boat is a bit of a wild card...http://sailboatdata.com/viewrecord.asp?class_id=4385

However this one has a deeper and narrower bulb keel with a draft of 5', rather than 3'9".

It also has a masthead rig (25') as opposed to the fractional rig with a 31' mast.

The masthead main is 10 sqft smaller, the Genoa 12sqft larger, and visa versa.
I suppose the narrower chord of the keel moves the COE fwd to balance this.

The boat was a freebie on account of storm damage to the bow and chine. All repaired now

And here mid repaint, now finished in 2 pack 709, with new rubbing strakes.


RH-I like the sound of an Etchells rig, any more around?

JJ-Does the IRC favour fractional rig?

Graham-I have seen some QT's with very nice carbon masts, but thats out of my budget.
As a boatbuilder I can do most things, but we are on a very slim budget.
I usually work on wooden boats, light years away from this 'modern' '73 Scout.

DT4134-would rather not have runners, we have enough of those on my lugger!

The question arises as I have no sails for the boat, so would rather source a second hand fractional rig and spend the money on sails than put new sails on a possibly worse rig for club racing.

Savageseadog I agree, the boat is not financially worth it, but it wasn't worth repairing either! I just fancied doing it as I wanted to sail it!. Its only little!
 
Fractional rig; much more tuneable, better angle of attack and slot.

Avoid running backstays though, an anachronistic and unseaworthy pain...

When did you last see a masthead rigged racing dinghy ?!

SilentRunningfromFolkboat.jpg
 
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I suspect the centre of lateral resistance of the Scout is in the same place with both keel profiles - but that the masthead rig was designed for genoas with a greater overlap than the fractional rig, hence their larger sail area.

A significant part of a big overlapping genoa is aft of the centre of effort, so it's possible to switch to a fractional rig with a larger main and jibs with minimal overlap without upsetting the balance of the rig.

No one uses runners these days if they can help it - it was basically a fashion, along with stupidly spindly rigs in the 1980s and early 90s.

Most boats designed at the outset for IRC have 9/10ths fractional rigs, with headsails no larger than about 110%.
 
dt4134 said:
Have you also considered whether you'll be racing in a quarter ton class on scratch rather than IRC? There's no point boosting your competitiveness under IRC only to find you're one of the slowest quarter-tonners around.
Click to expand...

An FYI, the 1/4 ton class race under IRC now, as the boats from the start of the era are not as quick as the boats from the end of the era. They have pretty strict rules about what you can and cannot change, I would highly reccomend getting in touch with the class association. Given the amount of boats with new rigs, it's quite possible that there might be someone out there with an old one...

Interesting class, seems that for many enthusiasts the tweaking and fettling is as least as much fun as the racing, but the money being spent on updating 26 foot boats staggers me.
 
flaming said:
An FYI, the 1/4 ton class race under IRC now, as the boats from the start of the era are not as quick as the boats from the end of the era. They have pretty strict rules about what you can and cannot change, I would highly reccomend getting in touch with the class association. Given the amount of boats with new rigs, it's quite possible that there might be someone out there with an old one...

Interesting class, seems that for many enthusiasts the tweaking and fettling is as least as much fun as the racing, but the money being spent on updating 26 foot boats staggers me.
Click to expand...

Would be a bit daft if they are handicap racing the 1/4 tonners. The great joy of racing in the various 'ton' classes was that it was level rating, so boat vs boat, not boat vs stopwatch.
 
Twister_Ken said:
Would be a bit daft if they are handicap racing the 1/4 tonners. The great joy of racing in the various 'ton' classes was that it was level rating, so boat vs boat, not boat vs stopwatch.
Click to expand...

...but the problem is boats were eclipsed by new designs almost every year, so there's no way a Quarter Tonner from the late 70s, for instance, could compete on a like-for-like basis with one 10 years newer.

However, the racing in the class is still incredibly tight - and there are always boats with a very similar rating to yours in the fleet - so it's much closer than any other type of IRC racing.
 
r_h said:
...but the problem is boats were eclipsed by new designs almost every year, so there's no way a Quarter Tonner from the late 70s, for instance, could compete on a like-for-like basis with one 10 years newer.

However, the racing in the class is still incredibly tight - and there are always boats with a very similar rating to yours in the fleet - so it's much closer than any other type of IRC racing.
Click to expand...

What range of handicap variation is there between an old dog and a rocketship?
 
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