Weather vs Lee Helm Trim

Rcsailing.net General Discussion
1

Sailing upwind all of us want to feel a little “helm” on the wind to feel our way into groove tuning for balanced centres to have the rudder centred as much as possible to limit drag. In practice a balanced yacht just needs small rudder correction and then let the Tx quickly centre the rudder.

Over time we develop a feel for lightly using the rudder when yacht is balanced properly to “always have small amount of weather helm” so the yacht climbs slowly into the wind. With this set-up the yacht will sail close to the wind by default and climb to windward efficiently with small rudder adjustments to move the helm to track in a straight line.

Brad Gibson caught my attention with a comment about how his world winning IOM “Brit Pop” was designed intentionally for lee helm trim.:confused: Coming from big boat background this is absolute no no …but as I have slowly been learning there are subtle differences with RC yachts & this maybe another one of little gold nuggets :rolleyes:

Can someone help me understand the benefits of having Lee helm trim set-up on RC Yacht?

Cheers Alan

2

may be something to do with equator line or Bernully law !!! heheheh !!!
or just because depend on his driving style !!!
claudioD

3

I would love to read the context from which this info was derived.

These are my thoughts.

A boat can be set up in three modes; slight weather helm, neutral, slight lee helm.

Have you noticed that with slight weather helm, you apply a little helm to stop the jib luffing, but if you apply a bit more helm and drive off another couple of degrees, the boat heel angle suddenly increases and the boat accelerates.

I suspect that Brad has set his boat up so that it is slightly lee helm so that is falls off into that higher heel/drive mode. . .then as the heel angle increases the lee helm is cancelled and the boat transisitions automatically to neutral.slight weather helm. The end result is that the boat sails itself in the high drive mode for much of the time, whereas we with slight weather helm are always applying rudder to seek it and spend less time in that high drive zone.

John

4

I guess a boat set up with lee helm is less likely to suffer the effects of broaching, although like you I can’t for the life of me work out why it would give a competitive advantage. I think Claudio may have hit the nail on the head with ‘…depend on his driving style !!’.

Do you know of any web resources where he may have expanded on his comment?

Regards,

Row

Just read John’s post and it certainly has merit, although surely it could only really benefit if winds were relatively stable in terms of strength. I guess coming from big boat back grounds there’s more to learn than we initially think!

5

Generally the lee helm on real boat is avoided beacuse dangerous with high winds forces and since everybody drive with weather helm trimmed boat also because is faster.

IMO, the lee helm with heeling start deviating more and increases distance from the buoy.

Driwing style ?

ClaudioD

6

Some discussion of this in the January 2011 newsletter published by the Seattle Model Yacht Club,

http://www.seattleradiosailing.org/?page_id=29

Don’t read just that one, they are all very well done!

7

thank for th elink Hew… nice read…

make me want to rethink the weather helm… although I’ve been “pinching so long” I don’t know any other way to sail…

8

Funny this came up, we just had this discussion this weekend at our local club meeting. One of the skippers likes to sail with a slight lee helm. His rational is that it is better for the boat to bear off slightly while unattended as it keeps the boat speed up. He came to this conclusion after watching boats slowly point up and loose speed when set up with weather helm. I personally dont like lee helm as I found that without constant correction I tended to be footing a lot of the time and loosing ground to the boats that were pointing. I find it hard to determine if the boat is footing, but I can see the jib wrinkle if it heads up too much. I have good vision, so I tend to be able to read sails better than most.

9

Hew, I was looking for the forum where I was reading about it, was awhile ago and finally found it again in WCMYA site via your link thanks.

I’ve have sailed the Italian IOM champion’s AC-120 and it was best handling RC boat I ever laid hands on, sailed like it was on rails and in hindsight it is nuetral helm boat, I rarely touched the rudder at all, then later had opportunity to be on sticks of another top 120 and found I could not sail it very well at all with his set-up, had too much weather helm for my liking…but owner sails it perfectly.

Now asking myself, what type of RC sailor am I ! L-N-W helmer ? by natural instinct I do things by feel but on RC yacht 50 meters away & not feeling the wind in my face has me guessing and regularly fall off the wind with weather trimmed helm :confused: 6 months ago I started using telltales to help me read what was happening with sails, takes lot of practice to keep looking at tell-tales but slowly getting there …I think !

Reading Jerry Brower’s post now turns on my lights :roll:: he says: "I feel if you are sick and tired of rounding-up, pointing too high, slowing down and then using your brake to get powered back up, (this guys got my number;)) why not take a Flyer and tune for Lee Helm?

So, here is the philosophy about why Lee Helm is better.

As a skipper is focusing on boat speed while sailing to windward, you have to react to four related thing that are happening to the boat. Is the boat accelerating? Is the boat slowing down? Is it pinching? Or are the sails stalling? (hey that’s me) Each of these things has to do with adjusting the sails and/or deflecting the rudder.

So, if the boat with Weather Helm is pointing too high and the winch is pulled in close hauled, there is nothing you can do about the sail trim – you have to use the rudder. But if the boat is falling off and the sails are stalling, you can always crack-off and accelerate. This is a big advantage for the boats with Lee Helm."

Hmmmm … maybe time for change of mind-set, just need to find the re-set button !!

Cheers Alan

10

As far as I have read and understand, Brad optimised his boats for the expected conditions. If you were going to a championships where it was known to be windy you sensibly would set up your boat to suit those conditions. One of those might be to reduce the amount of weather helm your boat has when heeled (which might produce lee helm in very light conditions when the boat is not heeled). I would doubt that setup would work in very light conditions.

11

I’m all ears & eyes being totally new to me but from what I’ve understood, here’s my summary take-aways of what Advocates of Lee helm trim have to say:

  1. Talking about just a tiny bit of lee helm, not enough for the boat to keep falling off onto a reach, just enough for it to sail a little low by itself so that you might apply a couple of degrees of lee helm every 10 lengths or so. When the boat is left alone it will sail a straight line with the lee tell tales just starting to lift.

  2. Two boats sitting near the starting line with their sails luffing and waiting to go; one is tuned with weather helm the other with lee helm with one second left and they both sheet in. The weather helm boat immediately starts rounding up and because it isn’t moving yet can’t be prevented from doing so with the rudder, good chance it will get stuck in irons or at best make a slow start dragging the rudder along.
    The lee helm boat sails slightly below close-hauled and can be brought up to coarse gradually as the speed builds. Any amount of lift generated by the weather helm rudder will never make up for this initial loss. The lee helm boat is out in front with clear air before the weather helm boat even clears the starting line

  3. Have the boat sail a perfect coarse in the gusts and a bit low in the lulls, so that it will power through the gusts with no rudder applied but will need nudging up a bit in the lulls. When sailing with lee helm pay attention to your tell tails, as soon as the lee one starts lifting nudge her up with a little lee helm. It is a fast way to sail.

  4. As the boat reacts to an increase of wind speed or a lift in direction of the wind, the skipper with Weather Helm is trained to wait for the boat to head up. But Lee helm skipper needs to watch the leech tell tails to steer the boat to windward. The difference is between waiting for a 6 kg boat to respond or to watching a micro-gram tell tale – it’s no contest. Guess which one reacts first. In a competition dependent on hand-eye coordination, why wait for the boat to respond when you can get nearly instantaneous feedback from tell tails.

  5. Sailing to windward close hauled; when heeling the boats with Weather Helm must deflect the rudder to leeward as the boat luffs and thus disrupting the lift that the foils provide as the rudder acts like a brake. While the boats with Lee Helm must more often deflect the rudder to windward and increase the amount of lift that the foils provide. Why would you want to decrease the amount of lift if you are going to windward? In addition, as the wind increases, the Weather Helm boats have to increase the braking action of the rudder, and this is while the Lee Helm boats deflect the rudder less.

  6. The boat tacks much better and accelerates out of the tack faster, once you have tacked and the sails fill you don’t have to use any rudder to keep it from rounding up on the new tack as you do if you have any weather helm.

  7. If you are sailing in a crowd and you lose sight of your boat it won’t round up and get in irons, the boat by itself will always sail powered up and you can keep it pointing with the occasional rudder correction. If you have any weather helm at all you have to be forever using your rudder to hold the boat in the grove and any lapse in attention will result in it pinching and slowing down.

You want just enough lee helm so the boat will stabilize its coarse with the lee tell tails lifting occasionally and the boat powering along at just below its optimum heading, then you can bring it up to the groove with a very small rudder movement from time to time, but your speed will always be good & tactical choices freer with lee helm trim and you concentrate more on finding best VMG than just pure boat speed…proof is in the pudding & I’ll give it a try !

Cheers Alan

12

What are some of the weakness’?

  1. can’t sail as high, so that need to be kept in mind when trying to squeeze in the next mark
  2. As windward boat, you must keep clear…a weather helm boat underneath you will cause you to tack away at a time when you maybe did not want to tack so you are forcing yourself to always pass another boat to leeward through their dirty air… in which case the windward “weather helm” boat will not need to point/pinch as high to stay with you… which gives them the option to fall off a touch and ride with you at a better speed or out point you and gain some separation and be able to control the engagement…
  3. A weather helm boat can always bear off or let the sails out to accelerate A lee helm boat will not point up or follow a lift as easily…

I see this as a great option on a heavy air day with a long wide course… where you can make some gains on speed at the expense of up wind distance… but a small tight course I think I’d still favor the weather helm…

What others???

13

I agree Marc !
ClaudioD

14

Alan,

Not so sure about this - all full sized boats use weather helm to increase their lift (about 5 -10 degrees rudder angle seems the optimum).

An RC boat with a small amount of built in weather helm will gradually luff - the lean angle will decrease causing a reduction in weather helm - and will naturally pull away. It will sail a good course itself. A boat with inbuilt lee helm will not sail by itself.

Steering by tell tails is OK when onboard, but from 100 - 200 metres away? You would need better than 20/20 vision.

15

Hi Jon

You could well be right, I don’t know !

My problem is in light air especially with very slight weather helm trim I feel slows the boat down with reduced apparent wind speed on verge of Luffing most of the time & correcting rudder just adds the problem & if not paying full attention and forget to tap the rudder when boat is 50-100 meters away, I’m easily in irons.

Pointing is not priority in light air, momentum is and thinking can have fewer mistakes with Lee helm trim having boat head higher (even if I can’t see tell tails) than lower to what little wind there is, yacht can then always be gradually always brought up higher gradually as the speed builds… that I cannot do when luffing or in irons.

Last year in AC-120 Italian champs, all boats in the finals that finished in front of me, I “now recall” had their masts raked well forward with what I now realise was preferred Lee helm trim for light conditions.

Just wish to learn/experience the difference for myself.

Cheers Alan

16

…

This may help to appreciate how much a sailing boat of 40’ can gain in speed just by bearing away for 5°.
It’s a pity that our models don’t have polar speed graphs !
cheers
ClaudioD

17

Mini boat to skipper instrumentation … ah now there’s a dream ! and this is what I was getting at with finding best VMG.

Example: We want to sail into the wind, going upwind from A to B…

• Red track supposing the polar says: with a 30° angle to the wind, estimated speed is 5 kn. Plot the route for a specified time and then tack (-30° to the wind), to reach the shortest way to the target.

• Or plot the green route for a wind angle of 45 °. The polar gives me a speed of 8 kn.

• Then plot the Blue Route for angle of 60 ° to the wind, the polar gives me a speed of 10 Kn.

Note that the green route, although longer than the red edge has you closer to the target. The blue track, even longer, but brings too far from the target (but is still a better choice than red).

The best velocity made good VMG (speed/distance) between the 3 routes, is the one in green…with less tacks !

Cheers Alan

18

I sail with the Sailonline.org crowd. and it is taking some time to learn and understand the the VMG concept… I never had the luxury of gauges on my dinghies…

the problem we have with our small boats. are the shifts… that happen so often… on big boats its not such a drastic shift. but we get 10-15* shifts a couple times on a leg Lake winds… they are what we got…

if I’m sailing and my boat starts to lift and follow the wind. I’ll let it. if the jib starts to luff as a header comes in. I’ll tack. most boats do accelerate very quickly which allows us to follow the shifts so easily…