This might seem like a silly question, but the daggerboard/centreboard is moveable for a reason. However, after a couple of inversions where the daggerboard dropped completely out of the slot, I have started to sail my boat with the board fully down on all points of sail. I've checked my speed using GPS, and can't find much appreciable difference with the board fully down, or otherwise.

Training tells us that the board should be fully down when beating, half way up when reaching and up when running. Long established classes such as the Wayfarer (and especially Laser) for example, seem to follow these rules.

But, I've looked into this further and found that some more modern classes (e.g. RS, especially those with bungee which goes over the top of the daggerboard when it's fully down) don't seem to bother raising the daggerboard once the water is deep enough after launching. My current race training has also highlighted that the daggerboard should be lowered *before* the gybe mark - something that I've never had the nerve to do, but so far I haven't had any bad experiences!

1. So, is gybing with the board down a bad idea?
2. Stability on the run is improved, but as for the boat "tripping over" the board as it gybes, does this really happen?
3. Is it really worth moving the board up and down for different points of sail? The increase in drag can't be that much, can it?

Any thoughts/suggestions please!

In a Topper, lifting the daggerboard in a reach and a run makes a big difference in light to medium winds.
In a top force 4 and above (18knts upwards), I leave the daggerboard down at all times.
Might not be the right technique, but every time I tried lifting it for the run of a gybe, I ended up pushed here and there by the waves and straight in the drink.

I'm sure you're going to have plenty of various answers depending on type of boats, usual sailing conditions and sailing skills.

It really does depend on the class of boat that you sail.

In a laser when its really blowing I usually leave the board 3/4 down to make it easer to keep it flat on the beat.

In anything assy i never take the centreboard up (mostly due to lack of arms/ability to keep the boat flat) but i have seen it done in RS400s

Apart from that i normally follow the guidelines

The 300 foils are really too big for the boat. I raise the board as the "guidelines". However, when sailing in a stiff breeze, due to the size of the board it is a must to have it up 9-12 inches on the beat as it makes sailing the boat up right a lot easier.

As said, at the level where it begins to make enough of a difference to your performance, it really depends upon the boat. Skiff-type boats tend to leave it down for several reasons:

1. Not enough time/too much sideways pressure to adjust it during bearaways and round-ups
2. different sideways forces may require the board to be down
3. less for crew to get caught on- not so much space on an RS800 especially once you figure in the centre main sheet and traditional kicker

as far as I can figure out, anyway. Sone do have levels to bring the board up a bit in high winds (at faster speeds, the losses of lift are offset against less adverse righting moment for overall greater efficiency) especially on flat water- in waves, there's more chance of stalling the foil.

Raising a centreboard does different things to raising a daggerboard. Raising a centreboard moves the pivot point of the boat aftwards. What this does is increase lee-helm. This helps the boat point deeper downwind more efficiently- very useful with a traditional spinnaker or the canting bow-sprit of the RS400*. Raising a daggerboard significantly (like on a Laser or Topper) does do this somewhat as well, though not to the same degree.

If you find you have a problem with the daggerboard falling out on capsizing- do you have a bit of elastic pulling it forward? On a Laser, you should have a length taught through the front of the board and round the front eye on the boat, running either side of the mast. On a Topper, there's a single line that should go round the mast and clip to itself. On both, this holds the top of the board forward in the case, meaning it shouldn't drop down when there's no side-load on it. That should stop it falling out when inverted, or at least leave enough sticking out for you to grab and pull the rest out.

As for speed- absolute speed is not the key in racing, it's what's variously reffered to as Speed to the Mark, Speed Made Good or Velocity Made Good (VMG). Two boats at the same absolute speed can have very different VMG.

I'm bound to be corrected on some technical points here, and look forward to being so. We all never stop learning.

*had a go on one last week for the first time- they point scarily deep. It's just un-natural if you're used to more conventional systems...

in my feva (aesametric gennaker) i dont actually go on a run for long and so i generally only go as low as a broad reach.

because of this i need the board down .

also as the bow is out when planing you lose the "grip" so the board keeps in contact with the water so the bow doesnt swing back on to the run

any RYA trining teaches you to have the board as suggested. however in the 600 i only bother to raise it on dead runs in the light stuff, otherwise there isn't enough time, and the boat gets even less stable, and its harder to bring the boat upright after you do piss it in.

As for centreplates, im not really sure about why but i know when i used to crew in a fireball when it got windy we swung the board back more for upwind to match raking the rig back i think.

in high winds i actually have the board deeper in the water during the run than on a tight reach simply because it makes the boat more stable. in windy stuff then raise the board upwind in order to stop the boat 'tripping' in the gusts. in an assymetric i would never raise the board unless i was going downwind without the kite or something.

gybing with the board down is fine aslong as your timing etc is right. if your timing isnt up to it then a raised board with make it more forgiving by reducing the heeling force after the gybe. personally i always leave the board in the 300 as without it the boat is just so much more unstable....

Think you might want to edit that para, Jim ("daggerboard up.... wetted area....increases" - eh?)

But I think we agree that you don't need so much board area offwind to achieve the same leeway angle?

So one question in light-moderate weather is: assuming the helm balance is still acceptable, does the drag reduction achieved by raising the board offwind justify the distraction of raising it? I'd tentatively suggest the answer is: only if the leg being sailed is a long one and you've nothing better to do (e.g. no kite to trim).

In windy weather, Frank Bethwaite advocates raising the board whatever (though probably not that much in percentage terms) in order to raise the centre of effort to enable more thrust. But when you think that the lever arm is from a couple of metres up the mast down to half a metre below the waterline, will a few centimetres really reduce the heeling moment appreciably? Isn't it more a case of making the handling/gust response more forgiving?

I've tried it in many classes and I can't honestly say i've noticed any benefit one way or the other; but then maybe I'm insensitive to such subtleties. There was one occasion, however, when I was sailing a Laser on a reach and it was not planing; I hoiked up the board and suddenly the bow rose and the boat shot forward onto the plane (but maybe I just cleared some rubbish off the board?!)

In summary, as people have suggested, there are many factors against raising the board: - helm balance, boat stability, space in the boat, and time/hands available. On the other hand there are potential benefits of drag reduction, and boat handling and (maybe) increased thrust in a blow. Whether the pros outweigh the cons will depend on the class and the conditions. So I'd suggest that people new to a class or sailing in general look at what the top guys in their class are doing and do the same - one of them will surely have tried doing it differently and at least found there was no significant advantage.

Thanks to all for your input, all of your comments and discussions have gone a long way to proving what I was suspecting - that there is no straightforward "method" of using the daggerboard!

To quote Medway Manic: "In summary, as people have suggested, there are many factors against raising the board: - helm balance, boat stability, space in the boat, and time/hands available. On the other hand there are potential benefits of drag reduction, and boat handling and (maybe) increased thrust in a blow. Whether the pros outweigh the cons will depend on the class and the conditions. So I'd suggest that people new to a class or sailing in general look at what the top guys in their class are doing and do the same - one of them will surely have tried doing it differently and at least found there was no significant advantage."

I would say that this is most definitely the case; RYA training teaches "the basics" in a classic way and, as sailors progress, then boat handling does become more specific. Personally, I have noticed that various boat handling techniques adopted by Class Associations are usually the preferred or even fashionable way of sailing a particular class. In at least one case, I didn't follow a Class Association guideline and subsequently found a faster, easier method of sailing the boat.

This brings me back to my initial view that maybe it's best to watch what the fastest guys are doing in their boats, but also to experiment out on the water to find whatever method works best in different conditions. Trial and error (lots of it)...

GRF:

I think one major problem with getting rid of the board on a dinghy would be that suddenly you would find you couldn't steer the boat. A board with only a fin is steered by carving on the rails, I'm not entirely convinced that the chines on a dinghy would be sufficient to provide a similar effect. I'm sure you've noticed in your sailing that tipping a boat creates steering in the opposite direction you get from tipping a board the same way, wether this is to do with hull shape or something i haven't a clue. I know that untill i worked out that I had to equate windsurfing to snowboarding not sailing in terms of steering i couldn't get the board to go the way i wanted it to go, so I'm not sure how you will steer a boat without a board using only the rudder.

I would be very interested to see the results of putting a sliding mast foot on a dinghy and trying your theory but it would be a lot of engineering. The only way i can see of doing it would be to slide mast, stays, and sheet lead positions all together, basically have a sliding frame with all the gubbins on it inside a hull to float the whole lot. If you ever do get round to it I would love to see the results.

So, now Captain Morgan is totally confused (he won't install a sliding mast foot or apply so much amount of rake on a Wayfarer), it's time to give a quick update.

If you're sailing in a club where there are other boats of the same class, ask the good guys and do what they're doing. Once you get the hang of it, you can decide to be radical...

(Sorry, I'm not far from being a total beginner and I got lost by the end of page 1).

Doesn't a windsurfer "carve" when planing due to the rocker of the board rather than due to the lack of a centre board?  Thought you put the board up to reduce the lift rather than change the steering characteristics.

I'd love a dinghy that carved round corners like skis or a snowboard, but I guess it would need a very flat bottom, lots of rocker and the ability to come very high out the water when planing ........... or hydrofoils even.

.

GRF, I'm sure the effects of introducing sweep or not into a centreboard on a sailboard are just as you claim, but your explanation of why it works doesn't fit in with any aero-, hydro-dynamic theory that I'm aware of.

The fundamental difference between the way sailboards and boats steer when the hull is canted (heeled), is surely that in the case of a dinghy the rig heels too, while in the case of a board the angle of the rig is independent of the heel of the hull.

People always go on about a dinghy hull steering a boat when it heels 'because the chines dig in' or whatever, but at least at low speeds the steering effect is entirely explicable because of the movement of the centre and line of effort of the rig in relation to the location and direction of the drag. Imho, the steering effect of a dinghy hull is very much secondary to the rig effects, at least until very high speeds when the hull forces possibly increase in significance.

Sorry GRF, I didn't mean to sound as though I was complaining or implying that a beginner was bereft of basic intelligence. I was only trying to put the conversation into perspective and bring an easy solution to Captain Morgan's puzzlement when he's next on the water.

All this debate about friction and wetted area etc. is nothing short of fascinating but I was just being practical. If someone's lacking intelligence, it must be me. Spare me the acerbic comments, I won't understand them anyway.   

GRF if the boards stall when the bottom of the plate is further forewards than the top, why is it that all GP14's sail upwind with the board canted forewards? that is their 'fully down' position.

by the way this is an honest question, im sure someone can present a suitable answer as to why this is different from windsurfers (are they different?) the only thing i can think of is that the boat balances better this way. but then if what GRF says is true surely it would have been so much better to simply move the whole board and slot a few cm further forewards in the boat?

the best way to demonstrate hull steering on a dinghy is to try to bear away with the boat heeled to leeward (away from you, then try the same thing with the boat heeled to windward with all the controls the same. Unless something very wierd happens with the Alto you should notice that it is significantly easier when heeled on top of you.

This is what i was on about with windsurfers using "hull" steering the opposite way to dinghies.

Just getting back to the part of the topic about moving the board back.  An alternative is to move the rig forward!  The 4000 as with most skiffs do this by putting up another sail - often at least as big again and all forward of the mast.

With the 4000 its easy to get lee-helm so you wouldn't want to bring the board back any further.

From my (basic) understanding of aerodynamics I cant think how sweeping the foil forward by 5 degrees would be significantly different to sweeping it aft by 5 degrees.

With the aft swept foil there is likely to be slightly more spanwise flow but this would make the foil less efficient. The spanwise flow contribution from the sweep is likely to be small compared to that from the pressure differential at the tip of the foil.

Sweep on aircraft is usually about reducing the drag at transonic speeds.

Forward swept wings on aircraft would be equally good at reducing the the drag at transonic speeds but due to flexing can cause all sorts of control problems, partiularly as the ailerons are at the tips and can cause the tips to flex even more leading to control reversal.

I think the problem seen is more to do with the forward raked foil twisting, increasing angle of attack and stalling. If you could build it stiff enough I do not think this would happen.

What were your windurf fins made from?

I guess you've seen the "T" foil rudders used on some I14 and Cherubs. 

As for rake angle - I have experimented with this myself.  Its not so good with a forward raked foil.  I have no evidence for this but it didn't feel good if it stalled.  I surmise that when the foil stalls the turbulence starts at the tip and works up the foil.  I imagined the turbulence was "washed" up the foil if the rake was forward.  If however the foil was raked aft the turbulence was "washed" downwards and so it didn't stall so suddenly and the stall seemd to be released quickly if the angle of attack was quickly reduced.