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Topic: Winged Rudders Posted: 03 Jun 10 at 11:20am |
So the winged rudders on the new N12s really seem to be making a difference. Do you (N12 sailors) think there is potential for them on a one-design like the ICON, or are they a lot of hassle and expense for relatively little performance gain? Do they make tacking harder? I read that some crews are now controlling the wing angle on a near continuous basis - that seems like hassle, but on a one-design could you use a dumbed down version with a fixed angle of about 4 degrees and shift your weight to trim the boat fore and aft if desired (e.g. lightwind, bow down by 4 degrees, wing goes to zero)? I know the conventional wisdom (if you can have such a thing in a new area of development) is that the hull needs lots of rocker to get the most out of a wing, but I don't really see why. The wing presumably works in two ways, firstly by creating lift to reduce displacement and secondly (unlike on a Moth) by interfering with and cancelling the stern wave from the hull. The location, orientation, size and detail of the foil must be critical to the latter. I'd love to know your thoughts. |
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timnoyce
Really should get out more Joined: 05 Aug 04 Location: Hampshire Online Status: Offline Posts: 1991 |
Post Options Quote Reply Posted: 03 Jun 10 at 11:59am |
We have had t-foils in the Cherub fleet for a few years now, and ALL of the top boats have them. We have the difference that we move slightly faster and also can get behind the t-foil on the racks which dramatically improves performance in all but the lightest airs.
Personally I feel the speed increase is most noticeable upwind when planing, and also downwind in light airs. Not sure I see the link to the foil being more effective with rocker either. There are a variety of control systems on the boats, most have a course rope adjustment to set the angle, others have twist grip to fine tune on the fly... (at high speed you normally don't have a spare hand to adjust it all the time!). We haven't had much time in the boat in the last couple of years so tend to adjust the foil less than some. We find it quicker to set it about right, and then trim using body weight. You definitely know when it is set right as you can feel the speed increase. Downwind, we point noticeably lower with the t-foil. I have experimented with letting the foil off when trying to pinch to make a mark and it does work. Regards to making tacking harder, we find they actually make the manoeuvres easier as they make the boat much more stable. In some cases, foil wings are wider than the hull width! Just my thoughts anyway. Kevin Elway wrote an excellent piece on t-foils which was published in Y&Y which has many more numbers rather than 'thoughts'! It is available to Cherub Class members on the website. |
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BEARFOOT DESIGN
Cherub 2648 - Comfortably Numb |
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Post Options Quote Reply Posted: 03 Jun 10 at 4:57pm |
Cheers Tim. They sound almost too good to be true. What are the downsides? I guess they cost a couple of hundred quid more (not much in the scheme of things) and are a pain to put in the car when travelling. Anything else?
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charlie1019
Posting king Joined: 28 Nov 05 Online Status: Offline Posts: 173 |
Post Options Quote Reply Posted: 03 Jun 10 at 8:02pm |
In our I14 we always pulled the foil on fully upwind regardless of wind strength, with the crew moving back in the boat as the breeze built. Down wind we pulled as much foil on as the conditions allowed i.e. fully on in light winds/flat water, all off helping to lift the bow for a safer ride when honking and waves.
Biggest faff is launching. On our M12 the stock was always attached to the hull, therefore the rudder had to be inserted from below meaning the boat had to be rolled over before launching to insert and the same once sailing was finished. I always felt following a tack it took several boat lengths for the foil to start working properly - the bow would sit up - but then taking well in any boat is a skill that comes with practice. Obviously this is less of an issue with a I14 as you generally are sailing on bigger water and tacking infrequently, however N12's are likely to be sailing on smaller stretches and therefore the effect may be more noticeable? Would be interesting to see a DCB race against a fast un-winged N12 on our stretch of river to see how much tacking is slowed by the foil! |
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Post Options Quote Reply Posted: 04 Jun 10 at 9:14am |
As I understand it the DCB uses a standard pivotting rudder on a removeable stock, so should be no harder to launch than normal. I suppose the loads on an I14 would be very much higher though, hence, perhaps, the fixed stock? The 14 is also a much taller and more powerful rig, and is much faster than something like the ICON. The ICON also has a longer hull. Taken together this should mean that there is much less risk of nosediving the ICON, so there may well be no need to let the foil off. If it can be left fully on all the time then it does not need an adjustment system, and that would take out a huge part of the complexity and cost of a t-foil. |
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Merlinboy
Really should get out more Joined: 03 Jul 06 Location: United Kingdom Online Status: Offline Posts: 3169 |
Post Options Quote Reply Posted: 04 Jun 10 at 10:00am |
I think you have missed Charlies POV peaky. I crewed for Charlie in the M12 I14 what he is saying the foil took time to work after a tack, until the boat started to gather some boat speed (obvious you may think) He was asking how much advantage a DCB would have over a non T-foil 12 on a narrow river or lake where tacking every 30 seconds may be key. |
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Post Options Quote Reply Posted: 04 Jun 10 at 10:23am |
Ah, I see. Thanks Russ. Well the N12s have races on small waters, so I guess time will tell. You didn't sail the 14 at Tewksbury, surely? |
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Merlinboy
Really should get out more Joined: 03 Jul 06 Location: United Kingdom Online Status: Offline Posts: 3169 |
Post Options Quote Reply Posted: 04 Jun 10 at 10:35am |
We did try once, i managed to break both carbon tiller extensions.
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timnoyce
Really should get out more Joined: 05 Aug 04 Location: Hampshire Online Status: Offline Posts: 1991 |
Post Options Quote Reply Posted: 04 Jun 10 at 10:35am |
True, transport is a right pain. I can JUST fit my t-foil in the boot of my Ford Focus Estate but it requires packing everything in around it. Cost isn't really a biggy if you are designing the system for a new boat. A rotating gantry can be controlled using standard block and tackle. The rudder itself will obviously cost more also due to it needing to be made from carbon, but for a new boat the cost isn't that much different. In light wind they do affect performance as they are quite draggy, and also if you have it set wrong it will act a bit like a sea anchor! Saying that, I don't know of many who have a non t-foil rudder blade for use in light wind so I think that says a lot. |
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Cherub 2648 - Comfortably Numb |
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I luv Wight
Really should get out more Joined: 28 Jan 05 Location: United Kingdom Online Status: Offline Posts: 628 |
Post Options Quote Reply Posted: 04 Jun 10 at 10:54am |
When we started using T-foils on moths ( about 16 yrs ago ), I made a few that were 'double-ended' so you could use them as a normal rudder one way up, or a T foil the other way up. The plain rudders were a tiny bit faster in very light conditions and really flat water, but as soon as there were any waves ( even from another moth ) or more than drifty winds, the T-foil was faster due to the boat pitching less = the rig working better.
The moths used the foil angle fixed, or maybe 2 positions, and always giving downforce to stop nosediveing. In light winds, the effective angle was trimmed to zero by sitting forwards. Moths and (most?) Cherubs have the foil at the bottom of the blade, making launching easier than having it in the middle. The Stealth 16 cat uses T-foils too. |
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