Does anyone know and can anyone advise. Frank Bethwaite seems to think that in some certain cases there maybe mileage in lighter crews using a shorter centerboard.?

I do not pretend to understand the physics nor do I really wish to study them, past reading his book (which did have me lost on many occasions!) 

It is simply that, I have a beautiful new centerboard made by Phil Milanes, which is an absolute work of art....except it was made for 2739. Making it 4 inches shorter than 3494's current board although a perfect fit everywhere else.

Any constructive (?!) advice appreciated.

Dunno about shorter, but it seems sensible that the maximum sitting out power is exactly proportional to the sideways component of the wind's thrust if the boat stays level so the lightweights need less plate area. We all use less plate when the sideways thrust is less off the wind.

put it in and try it.

nothing ventured nothing gained!

I used a short centreboard in a N12 for many years. The boat was very quick inland on rivers and lakes and at places like Salcombe but I always felt that we were not as quick upwind at sea. The centeboard case was made to fit the shorter board so that less water was carried plus there was more room in the aft end of the boat for the helm. There may be advantages tacking as well as for lighter weights in a blow but it's impossible to measure. It is fun to see your competitors run aground when you don't!. Dave C (now MR 3508)

You'll need a 'stuffer' I believe - something to pad out the inside of the case to avoid carrying that extra water!

Just like lowering the center of effort of the sail reduces heel, raising the centre of effort of the centre board has the same effect as you could logically a reverse of the sail.

a 4 inch shorter board would raise the centre off effort (by approx 2 inches, subject to all sorts of other variables in the board shape).

The best answer is 'try it and see', although I'm not sure you'll notice the difference unless you have a tuning partner you can do a bit of 2 boat tuning.

From my windsurfing experience, the bigger you are, the larger a skeg you use, especially when carrying a big sail. That was all some years ago, and looking at modern boards, they use(by old standards) huge skegs, to stand up to the 12m sails you can now set in moderate breeze.

Franks son Jullian Braitwaite used shorter boards on his B18 skiffs when the breeze got up, many 505's & FD's had devices to lift the boards vertically via there pivot bolts again to reduce the amount of board exposed without raking the board aft which obviously alters the CLR/CE relationship. 
In short it should be an advantage when overpressed,
A disadvantage in the full power/lighter wind range.
As others have stated try it and see.

Once in the distant past I crewed Jack Holt in 636 'Fiddlesticks'at Ranelagh SC, Putney. The wind was a howling north westerly against a strong flood tade making it a tough beat towards Hammersmith and a hairy run back to Putney. As we launched Jack shouted 'half plate and leave it there'. 

Apart from us virtually the whole fleet were blown over on the first beat and we were the only boat still racing by the end of the first lap (no transom flaps then). I learned a lot from Jack in that race.

Perhaps I should also add that we were the only boat to finsh.

Re Barry Watkins reply. Yes FDs and 505s did have adjustable pivot points but don't try it in Merlins, it's agin the rules

I Did realise that, it was purely for thought re shortened boards, however what about a vertical slot in the board where the bolt is; how would that be ruled on?
Just for interest sake?? Barry.

First sentence of Rule 6a - from the 2005 MR Year Book:
The Centreboard shall be raised or lowered ONLY BY ROTATION (my caps)about a pin , bush or bolt passing through the centreboard and located in the centreboard case.
Not much room for manouvre there I feel.

oh yes there is!  How about a curved slot in the centreboard such that different angles result in diferent board angles... and that could be superposed on other boad rotationas too?

Oh no there isn't!!! Read them rools , Deepy!

GGGGGGGGGGGG

What about a pin that happens to be shaped like a crank, so it rotates the centreboard as normal, but you can also wiggle it to raise/lower by an inch or two? Heh heh...

Don't understand....

On Garry's boat (111) the board is on a kind of sliding sort of free-in-the-slot kind of affair,

Sorry about the bad description, perhaps Gaz will help...........

Sorry...  Was slightly addled last night, and my description doesn't really make sense to even me this morning.  I'm sure there must be a way around this rule though!?

As the original cause of the this centreboard rule (I had built a Merlin Rocket with a daggerplate)I would love to see if any of the great brains in the class could get round this rule which has stinted the design of boats for over 20 years. This rule was foisted on the class within 3 weeks when an Extra special meeting was held to discuss how to stop this particular avenue of developement. Come on, there must be a way around it!

I think Jon is absolutely right about 111.  The metal centreboard slides forward and up, or back and down in a greatly lengthened case which extends some distance under the fore deck.  The forward edge of the slot acts as a pivot point for the forward edge of the plate to slide on, but it certainly doesn't pass through the plate.

we have a similar rule in the 12, our interpretation is that hatchet boards are legal.

I doesn't say that the bush or bolt must be fixed - Sure the board must rotate around it but maybe the position of the bolt may be tweaked, up-down/fore-aft. Did After Hours have a movable board? (It had everything else).

The 12's got in a right tizz about dagger-boards back in the late 70's. The worst of it was several boats were built before they were banned then there was a lot of "discussion"!!! For a while the few daggerboard boats were saught-aftr and lots of people felt it was unfair that a select few were legal. The dagger boards were faster mainly because of the reduced turbulence and wight carried in the plate case but it was also felt that not moving the centre of reisitance back off wind was also an advantage. They were a real pain on rivers and lakes. One problm was do you gybe with the plate fully down or no plate at all - lots of fun in a heavy wind with a very short water-line! My advice - don't go there!!! Dave C

Can you imaging the water p*****g in through a movable bolt fixing though?

After Hours did AFAIK in it's original incarnation at the Looe Nationals in 2000 have a centreboard bolt which could be moved.  I think this was achieved with a sort of bridle thing that reached down to the pivot bolt from the top of the case and could be moved along a rack, as could everything else you could think of.

It almost completed a couple of races but spent most of the champs competing for the bimbling prize, for which the boat and Glen put in a world class effort

Surely the idea of a restricted class is to allow developement. If the rig, hull or appendages are not suitable for particular venues or conditions then the direction of that developement will not be pursued. the MR class was rushed into this particular rule to stop development. We were not able to try something that was legal within the then existng rules. A mistake,I feel!!

i've checked my facts now and After Hours completed 5 out of 6 races, but just didn't go very well because there was always something adjustable in the wrong place or jammed as well as being over 10kg overweight

Isn't this fun? Folks suggesting ways round might read rule 6a in its entirety first.
The daggerboard enthusiasts might find themselves a bit out of balance with a fully raked rig.
Also getting an ace, but well built, crew like Barry Dunning through the gap between the daggerboard and the zimmer frame in a wild reach to reach gybe might be a bit problematic.

Would't you just put the daggerplate further aft to accomodate the rake in the rig.? That would give a few more inches to allow someone of my sphelt proportons to get through the gap! Come on everyone get your thinking caps on.

Having spent my youth sailing up rocky shores with dinghys with dagger boards and seeing the damage to modern RS's these days I'm not a fan of dagger boards.
In days past we built over long (fore & aft) cases and used chocks to position the boards (yes even 30yrs ago we used shorter ones in heavy weather!)It proved to heavy .to fiddly & to time comsuming, whilst figuring it out others got on and learnt to sail there boats better. Which age tells you is usually the best option.
PS thanks Mike & G for the rule bit on rotating around a bolt etc, all pretty clear going back to the threads beginings I still believe using his short board is a good propersition in heavy air unless of course thers a rule about changing boards mid series (both being the same weight obviously

International 14's use dagger boards, do a lot of reach to reach gybing in all weathers, don't usually pull them up (much) and rarely have to adjust them fore and aft (some can, some can't). shorter board for heavy weather - yes, but pull it up and push it down - who has time?!!!

Yep Barry D you should put a dagger board back to balance a raked rig but a major selling point of them is they fit the box and don't carry water, so you shouldn't. It's hard to envisage one class carrying all the go-fast gizmo's from every other class is it not? Moths have cracked it. Keep it simple, your head out of the boat and arse out of the water!

Anyone thought about a fixed centerboard. We have fixed rudders and if the board is the right size then it shouldnt need raisng and lowering. Could be taken out for towing! If you dont raise or lower the board then it will be within the rules!

Barry you need help mate....

Dear Jon, Closed minds and all that!

Only Joking Barry!

Fixed C/B would rather prevent one from sailing at Banbury after August though!!!!!

Excellent Barry D. This can be tested cheaply. Capsize on land; stuff a pre-cut sheet of polystyrene up behind the lowered plate. Duct tape the slot. Get 6 strong men to lift boat upright and carry into 4ft deep. Try it in a race. Reverse procedure upon return. Please report back

thats when you fit alternative winter bilge keels :)

Bilge keels, now theres and idea for the east coast!

Great idea Mike. Have to make sure that the plate was of optimized size for this configuration and the board was in the right position fore and aft for both upwind and downwind sailing. Would be awkward on puddles and inshore but for open sea condtons, great! Out of interest are the new foils on the Moths fixed or do they raise and lower them? With a fixed plate does this give the Merlin the opportunity to try a foil?

Oh gawd! More sleepless nights on the forum now we are onto foils. The ideal starting point is www.rohanveal.com Rohan is the Aussie guy who moved moth foils from flaky to practical and dominated the Moth worlds in recent years. His website has lots of info and pictures and links to other sites. Interestingly two Brit blkes whose names now escape me, beat Rohan into 3rd place  in this years Moth Europeans. Their foils are on both plate and rudder and are integral with them.  but both have manual control to rock fore and aft a little, to get fore and aft trim correct for lift-off and clever automatic mini-adjusters to stay flying in waves. There was one flying in the Hayling channel whilst we were at the Nationals.

Now thats what I call development! If a Merlin had a fixed keel could that route be followed. No doubt the Merlin Commttee will be callng an emergency meeting to plug this loophole!

Done last year I believe re the rudder, use on a 'rotating around a pivot etc' centreboard not possible or logical capt'n,  time for breakfast I believe!!!!!!!!!!

As one Barry to another, do you speak Engish????

Seriously Barry I have been through the 2005 rules and can see nothing on rudders. Am I going blind? Please enlighten.

AGM Abersoch 2003 (I think) discussed worries about foils. Decided not to ban in hasty fashion but let people play, as I recall. Don't think anyone there imagined foils on a rotating centreboard in a box for obvious reasons. I believe some folk, maybe Linton Jenkins who builds Int 14s rudders amongst other interesting stuff, tried a foiled rudder, but haven't heard of anyone making it work yet. Not a whisper of anyone trying a foil on a fixed centreboard which stays down. Might work. Who can say until you try, but a Merlin is a hell of a weight to lift on foils compared to a Moth.

Hi Barry It's Barry again must admit I havent checked the bible (rule book)I'm not that keen! but I seem to remember seeing a note in a mag which if I recall was to the effect of banning winged rudders etc. Now it is more than poss that this proposal didnt go through, so that being the case firsly my apoligies for incorrect comment & secondly despite my dislike of said dagerboards I am now the proud ownwer of a carbon casette style rudder set up on my 24yr old NSM, so as my sailing(midweek only at Gurnard)has finished I might look into sprouting wings for a laugh or two.
I will of course consult said rule book and post a pic to give everyone a chuckle, before & after bitting the rocks!! all the best . 
ps before anyone else says it, no connection to Red Bull!!!!

Don't the rules say the centreboard has a max width, and must retract fully into the case?

No, it says'When fully lowered the centreboard shall not extend more than 1400mm below the keel. When fully raised the centreboard shall not extend below the keel or above the sheerline.' Nothing to stop a centreboard that doees not raise or lower. Lets see how long that loophole lasts! Long live a truly resticted developement class.

That Barry Dunning, he's not a Messiah, he just a naughty, naughty boy, stirring up trouble like that...

If it don't raise or lower, its a keel, not a centreboard, and none of us are old enough to be sailing keelboats!

GGGGGGGGG

I'm not a lawyer but, in addition to GGGG coments, the word 'shall' in the rule makes it not optional, in my opinion 'shall' is the same as 'must', otherwise it would say 'may'

"The centreboard shall be raised or lowered only by rotation about a pin,
bush or bolt passing through the centreboard and located in the
centreboard case. The location of the pin, bush or bolt shall either be a
fixed one or be adjustable only along a line parallel to the fore and aft
axis of the hull."

and if you really want to...

It�s almost worth changing rules for the opportunity to watch someone sail with a �fixed winged keel� at Salcombe.  Weed, rocks, mooring ropes, fishing lines, plastic bags, mark ground tackle� the hilarity would go on and on.  Not to mention carrying the big old lump down to the water 2 foot above their heads while trying not to knock the wings off.

The rules should be redrafted immediately, let the comedy commence.

Hydrofoling at 40 knots on a 3 sail Gurston blast, though, something to talk about in the bar afterwards.

I think that rule could be interpreted such that if the centreboard pivots, then it can indeed only rotate about a pin.  However, I don't think there is  an obligation to have a centreboard which is raised or lowered at all.  Whether a keel is allowed though is a matter of definition.

Nice try, of course a keel is allowed, infact required, the depth is an issue though - only 30mm, so no c/board just a keel would be dead fast downwind, but maybe too much leeway on the beat.

"the exposed depth of the keel,
inclusive of keel band shall be not less than 20mm or more than
30mm."

its taken half an hour to read this lot - now I understand why I didnt win many races - lack of interlect, but huge potential.

Cancel all thoughts of fitting humour promoting wings to the old NSM, my crews justed phoned hes just done a deal on Joe Richards hardly used 'Virtual Reality', So it's a new ball game!

Define centreboard!!!

I gather that Frank Bethewaite is experimenting with lee-boards next season, after closely monitoring the sea barges on a recent Dutch holiday. It seems the lack of a centreboard case can give significant structural benefits to a hull, not to mention being able to add wings to the foil and still retract it.