Mainsheet thoughts.

[GregPitt]

Any thoughts?
Has anyone, to anyones knowlage tryed putting a centre mainsheet system on a national 12? As I imagine there are some down sides to it. Space in the cockpit, extra loads etc. Also I can imagine keeping the boom on the centre line wouldn't be easy. Has anyone got any thoughts on this? I presume it is leagal?!
Many thanks, Greg.

[Alex D]

I know some 12's have them, usually with the option to set them either way. Space would be the top issue.

[Chadders]

Yes it is legal and a few have used centre mainsheet arrangements with sucess but the problem is space which is why most people use stern sheeting with split end mainsheet set up.  My own boat when I bought it had a Laser type arrangement with stern sheeting which then ran along the boom and down from the middle to a central block on the thwart and that worked for the previous owner but not for me I took it off after the first sail!  The nice thing about a 12 is that if it works for you you can do it and I guess it is a combination of personal choice and crew size.
Howard C
 

[johnk]

There are three  options:
a) sheet goes from boom end, round block near transom, back to boom end, along boom to mid length, through block to hand. The only obstruction is the block on the boom at mid length which could be a head banger!

b) sheet goes up and down between block on centre line just aft of thwart (or where a thwart would be) and mid boom enough times to get appropriate mechanical advantage and leads from hull mounted block (swivel) to hand. This latter is used in single handers such as Solos but makes it impossible (or nearly so) for a crew to move around. The sheet loads are all at mid boom which could have structural implications with a loose footed main but kicking straps work OK.

c) as (a) but sheet goes from mid boom to block on centre line and then to hand - used in Laser and centre main Toppers. Again this would obstruct crew movement.

Keeping the boom on the centre line is straightforward for (a) but would need a track with controls for (b) and (c). Most crews do not like having to sit on a track!

If you want to try it I would recommend (a) which only needs an extra block attached to the boom at mid length plus a longer mainsheet. Most of the sheet load on the boom is at the aft end so there is little change in loading from the normal transom sheeted arrangement.

[Martin]

I used method a) when sailing a 29er whilst on a Sunsail beach Holiday in Turkey.  It took a lot of getting used to but is clearly suited to the skiff style of boat where you tend to use the cockpit as a working platform that you walk around.
I have seen it used on an A/C boat (on a small shifty puddle)and to my my mind it looked a bit awkward.  It might work better on a DB but personally I think the split mainsheet arrangement works really well on a 12.

[Gareth (Guest)]

I had the same conundrum moving in to the 12, just about a year ago.  I tried the conventional transom sheeting for a couple of months but couldn't make it work. The next variation was option (a) listed above, I liked the sheeting angle but found there was too much rope to sheet in and out. So the final set up is a split tail on the transom up to block on end of boom then to a good ratchet block half way along the boom.  The sheet loads are a little higher so you do need a decent ratchet block (I'm happy with the Ronstan Orbit, good holding and much lighter than the Harken so it doesn't swing around as much)  The split tail keeps the boom central.  The compromises are: without the extra purchase at the end of the boom a little more kicker is required to maintain leech tension and the holding power of the block does chew the mainsheet.
Gareth
3162 Bicycle Clips

[JimC (Guest)]

Its interesting to note that when the Toppers were first considering their current centre main option they did a fairly thorough trial with a days racing of boats with both arrangements, swapppig boats between sailors and using using former top Topper sailors who had moved to centre main boats.
Although I don't think any human could really spot any advantage for one against the other in the race results when I did some stats the numbers showed a small but just statistically significant difference. The aft main was faster. Naturally that hasn't stopped every Topper coach in the country telling the kids to get the centre main on the boats...  Its a lovely demonstration of the way people would rather believe their preconceptions than real evidence.
I don't know that space is really that much of an issue, having sailed forward hand in 12 foot boats with various centre main systems for many years, As well as centre bridles or posts (like a hoop but neater and cheaper) a common option on those boats was bridle from transom, through boom end block and along to ratchet block on mid boom, which is one less purchase than johnk recommends but was adequate with what was probably a slightly smaller and certainly higher aspect main and would certainly work well with the split tail mainsheet.
But, speaking personally, the results of that trial caused me to look very hard at aft mains again... It seems quite feasible that the results from the Topper trial have more general validity, and I would think very hard about using anything unless there are special reasons, such as the crew taking the mainsheet as on the skiff types. I should not be at all suprised if you guys are right and fashion wrong when it comes to the best sheeting arrangement for "normal" two handers of any size...

[Bim (Guest)]

There is one more option.
Have a look at August 2008 on the National Twelve calender.

Mainsheet goes from end of boom, to block on split strop on transom, back to block on end of boom, along boom to gooseneck, through block and down to heel area of mast, through block and back along one side of and under centreboard capping, up through centreboard capping to block mounted on back of thwart, to hand. 
Looks a nice arrangement but not sure how well it worked in practice, might be a bit of friction.
This topic comes up regularly and those that really hate an aft mainsheet sort something out, but over the years I think the simplicity of an aft main always wins through.
Bim
N3410

[Gareth (Guest)]

There is another factor I believe Topper coaches considered when recommending that kids switch to centre mainsheet.  This was the concern that the transom sheeting and the trend for a lot of trunk rotation to help the boats over waves when hiking had the potential to put some very lobsided strains of backs and knees.  It's certainly something I noticed when getting in the 12 with transom sheeting it did cause me to hike at some very strange angles, especially in the breeze where I always felt I was getting dragged backwards down the boat.  Having the sheet leading straight to the centre of the body certainly lets me hike in a more balanced position. 
For the speed round the course question in toppers I can believe the old way is faster, there's less sheet to play for faster sheeting and the centre system does have a  tendancy to leave the boom very banana shaped which can't be fast. 
The other question is how much time are you willing to put in learning a new technique, a fluffed tack thorugh dropped sheet or falling over is never going to be fast.
Gareth
3162 Bicycle Clips

[Crusader 3244]

A point of note is that regardless of the mainsheet setup be it transom, laser style, or conventional centre-main the sheet loads for the helm will be broadly similar for a given mechanical purchase over the mainsail loading.
Consider the instance of replacing a conventional 2:1 transom mainsheet with a centre-main. If the centre-main is now sited half way along the boom you will lose half the mechanical advantage over the transom main and so a block arrangement of 4:1 would be required to acheive the equivalent mechanical advantage, ....and there would still be the same amount of mainsheet to be sheeting in but in my experience it often SEEMS like more.
Remember, with either system, the closer the boom is sheeted the less efficient the mainsheet becomes at pulling the boom inwards (think vectors) and instead much force goes to pull the boom downwards. This effect can be accentuated with c/main and hence the need for hoop or track systems.
On bigger boats with bigger mainsails and with less efficient kicker sytems the c/main and track setup could be used advantageously to control leach tension. Equally, on boats with spinnies or gennakers the convenience of being able to cleat the mainsheet (easier in practice with c/main) to free a hand while spinnie handling could be helpful.

It seems to me distributing the crew weight correctly fore and aft is crucial in a twelve foot dinghy and so the hindrance of a centre-main is something I can well do without. If I never sailed inland with fickle breezes or if winds of more than force 3-4 were guarenteed every time, ....well, .....maybe!

[tedcordall]

 
I went to the system described by Gareth a couple of posts above. A split end goes up to the boom, along to the middle of the boom and then to hand via a serious ratchet. In theory it is only a 3:2 purchase, compared with the aft sheetings 2:1. However the advantageous sheeting angle from the boom to hand , where you are pulling the sheet towards you, rather than down, (when the boom is near the centreline) means that the 'perceived load' is very similar to aft sheeting.
 
Other advantages
- when caught by that unnoticed lull when at max hike, there is something with which to haul your a**e out of the water.
- There is no crew obstruction.
- There is less string.
- Downwind, if the crew is not paying attention while sitting on the thwart you can flick the mainsheet and clonk them on the side of the head with the ratchet block! (this requires thought in siting the block correctly in the first place):-/

[gareth (Guest)]

Must adjust the postion of the mainsheet block on my boom, I think it's a touch too far back for crew abuse.  Thanks for the handy hint Ted
Gareth
3162 Bicycle Clips

[GregPitt]

All usefull hints thanks. My consern with having a sheet led straight off the boom to the hand is that there is no way of controling leech tention with the mainsheet. this can be very important in mediun to light conditions. The only way to controll the leech tention is with kicker tention which then starts to bend the bottom part of your mast sooner than you would idealy like. Again this would be possible but needing the use of well calibrated mast rams and gooseneck shrouds. All getting a bit complicated when the big advantages in a small dinghy are going to be changing gear quickly according to shifts and gusts!
Has anyone found over tacking a problem with a centre main? The boat is 2meters wide, making a long tiller extension? limited room if the centre main comes from the transom because you can't flip the extension around the back of the boom. Thoughts?
I am in the prosses of buying a 12 and I am trying to persuade the previous 420 helm I'm going to be sailing with that a rear mainsheet with a split tail is the way forward. Althought the strange angle of hiking is something to consider, we will have to make sure we spend equal time on both tacks to keep our backs straight!!
Greg.

[broz]

You might want to look at your weight distrabution before you change, sticking a heavy bum out over the transom makes the boat very slow. If you are small you can still tack facing back as per Europe sailer.
You may also need a stiffer boom to maintain sail shape and a boom track as per Solo to control mast bend in different wind conditions. 
A c/main system that sheets in and out fast is also bad news.

[Derek]

I agree that the short tiller/long tiller extension solution gives you better leverage when fast planing by giving you a better angle between the extension and the tiller. The long extension can cause an issue if you want to use a laser type front and back system. Why is this system popular? It seems to use more space than any other.
You could try flipping the extension under the boom while you have the helm down to initiate your tack before you recentre it to make the tack nice and smooth - easier said than done.
Another solution which I saw a while ago was a hoop or traveller well behind the usual position of the thwart.
This gives the crew a bit more room but still restricts fore and aft movement.
Whichever way you go at this you are compromising space in what is admittedly a rather short boat. This is perhaps why so many of us who have sailed centre-main in other classes sail with aft main in a N12....