What are the differences between say a barn door rudder, a blade and a balanced foil, other than the obvious shapes?
If one wished to covert say from a barn door rudder to a balanced design, are there tables or formula to refer to?
Basic rule of thumb though, take 2% of your profile underwater area, and this is the size, area, of rudder you'll need. Location: Eustis, FL Nothing personal, but if you have to ask, you're probably not qualified to make this change without some direction. Location: Sydney Australia Rudder design is critical for speed and design in many dinghies. A barn door rudder can make a high performance boat basically impossible to sail; try sailing a fast cat with the rudders up to give the barn-door effect. I am doing this because I like to experiment and breathe new life into abandoned (sail)boats.
The rudder change to a kick-up is a purely practical decision, but experimenting with aspect etc cannot hurt. May even mess with the dagger board a bit to create more lift, but that will be second to last step, after the bow tipping, if I decide to go that route.
Location: Australia I'd say you've got a reasonable chance of success in swapping the tasar blade for the traditional one. I recently put a B14 blade on the back of a sailing canoe that had always had unpleasant weather helm from the significanly raked traditional style rudder.
When the two rudders are side-by-side, they are the same height; however, the Laser II is a true foil. I believe the new foil will be much more efficient with less working surface, and the balanced configuration should also ease feel and help eliminate the terrible weather helm the door rudder produced. The only added surface, I have decided, will be the leading edge portion to secure a balanced foil, at least right now, and may taper it a bit to the bottom edge. The entire top of the lead edge will be underwater on plane downwind, so that should reduce problems in that area. When heeling to weather, normal effects are expected due to foil being hung behind and not under hull.
I planned to use wood for the new leading edge, maybe mahogany, clear, and fixed it to current foil via SS fasteners or wood dowels, epoxied in place, then finished with glass cloth and fair it it to match current leading edge, maybe a hair finer edge. Location: Sydney Australia I'm not sure whether the L2 rudder is exactly the same as the Tasar one, but it looks pretty close.
If you wanted to add more balance, changing the rake of the foil in the rudder box would be a lot easier. Sorry about the typos earlier, and Jim's estimate of the typical IC rudder size is no doubt more accurate than mine.
I am guessing the different hull shape and weight (added 30#) will require a bit more rudder surface, but I do not plan to touch the blade until I sail it first.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. The rudder and tiller on your boat are pretty important pieces of kit - you may have sails full of wind, but without a rudder and tiller, you'll be hard pushed to get the boat to go in the direction you want. Taking care of your rudder and tiller should be a priority - this one had been through a few scrapes.


If you need to straighten an extension, the best way is to just bend it, carefully and slowly. Unfortunately, once we got the tiller extension straightened (Photo 5), we realised the tiller itself is bent (Photo 6). Next, there was no way to secure the tiller and extension into the rudder; hence, the first time we took the boat sailing the tiller kept coming out of the rudder. At the end of the rope where it would go around the cleat on the tiller, we have attached a length of shock cord as a handle.
Finally, as you can see in Photo 12, there is a length of yellow rope attached to the rudder stock - the other end of this is attached to the bung from the back of the boat, which has a small hole drilled through the handle; this bung is secured to the rudder, so we'll never be missing the bung! They could do with a light sand and a varnish to have them shining again, but otherwise they're totally fine.
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It will carry 90 square feet of sail (original was 78 sq ft on wood flex Finn-like mast, not practical to replace or refurbish. I'd leave it out of the box until I'd tried it: balanced rudders are very unusual on dinghies of that size and have some potential downsides. If rotated at the correct angle, the center of pressure of the tasar blade will be closer to the pintles and should give less helm. I have to agree with the previous observation that I too found the narrow blades on Laser II and Tasars puzzling, but the science seems to be in the foil shape and aspect. The rudder blade itself is in great condition, with only a tiny nick in it where the back of it comes up and meets the rudder stock, which is too small for us to bother doing anything with. The first idea was to put the extension in a vice, with the bent part of the tiller in the vice, and tighten it up slowly, thinking the vice would straighten it out - unfortunately it won't, it will simply crush the extension at that point. Tighten the end up in a vice (wrap it in a towel or tissue to minimise scraping, Photo 3), and carefully apply force in the required direction to straighten it. It appears that at some point, the downhaul rope from the rudder was secured onto the cleat on the tiller very tightly, when the rudder hit something at some speed, attempted to kick back up, couldn't, pulled on the cleat, stressed the metal around the cleat, and bent the tiller slightly. Many insurers actually have a clause in your terms and conditions that say you have to specifically ensure the rudder is secured to the boat or your insurance is invalidated if it falls off and you lose it.


We lined up the tiller into the stock as far as it would go under normal conditions, and drilled a small pilot hole (Photo 8). So, a small length of cord-thickness rope now secures the split pin to the rudder stock, and the pin secures the rudder stock to the tiller extension (Photo 11).
It was an old piece of fraying rope, not particularly nice to the fingers (Photo 12), so we replaced it with similar thickness 12-braid polypropylene rope (actually rock climbing rope, so it should be strong enough!), using a plain overhand knot as the stopper into the rudder blade (Photos 13, 14, 15, 16 and 17). Packaging should be the same as what is found in a retail store, unless the item is handmade or was packaged by the manufacturer in non-retail packaging, such as an unprinted box or plastic bag.
Import charges previously quoted are subject to change if you increase you maximum bid amount. On the Tasar, the amount of balance is just right to make a delightfully light helm that still has great feel. At some point, we believe the universal joint had been in an awkward position, and the extension been under too much pressure, and it bent it pretty badly (see Photos 1 and 2).
Depending on the bend in the metal you may need to rotate it in different directions (Photo 4).
It's not bent enough to be a problem, or enough to significantly weaken the metal, and it's not bent enough to warrant doing something about, other than to ensure it doesn't happen again (more on that later). The rudder stock itself had a small hole in the top (Photo 7), but the tiller did not have a matching hole. We then worked our way up with gradually larger drill bits (Photo 9), until a cotter pin of sufficient size to fill the hole would fit all the way through (Photo 10). Because of the way the tiller fits under the traveller on a Laser 2, it's unlikely that the rudder will come off the boat and become lost with the tiller attached to it - there's also the level in between the two pintles on the back of the boat that the rudder fits to - but now we're sure it won't go anywhere. The shockcord handle will allow easy downhauling of the rudder blade, but also have some elasticity and "give" in the cord to allow the rudder to pop up a small amount if it hits anything, and not put as much stress on the tiller as plain rope cleated off would (Photo 18).
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If I don't have line drawings on it and basic spec's I'm sure someone here does and a new rudder design recommended to suit your needs. A racer will attempt to get the least amount of drag with the most efficient shapes and the lightest structure for the loads expected.
The Laser is somewhere in between and has a heavy helm, even when sailed well enough to win titles, because it is raked whereas the Tasar and Canoe rudders are vertical and have the rudder post effectively about 30mm and 40mm behind the leading edge.
Of course - this will only work on metal tiller extensions, if you need to bend a carbon tiller extension you've got much worse problems (since carbon fibre won't bend). A shoal cruiser may have no need for this level of expense, draft, complication, contrivance or efficiency, so a barndoor could be installed, though this would usually be seen on an era piece, like a cat boat. Typically, small craft have to address shoal requirements, so the rudder may have a kickup feature, which can be engineered in a few different ways as well.



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