IOM question

Yesturday I took my latest winter project for a sail. After a little tweeking (so it did not have lots of weather helm) it stated to track real nice. But when it got to the upper limit of its A rig, it would not want to turn down wind when I wanted it to? I was able to turn it when there was a lull, then it would go real nice done wind. Is this a common thing with IOM’s or any RC sailboat? Is there a somthing I can do to fix this or am I doing somthing wrong?

This may sound like completely stupid comment, but I take it you did let off the sheets.
You mentioned that there had been weather helm at the start of your ‘tweeking’, so have you completely eliminated that or not. What is your rudder throw. It should be in the region of 35-40 deg each way. What design is it and has it been constructed to the drawings.


thanks for the quick reply. Yes I did let off the sheets. The boat is a Noux, and built to the best of my ability to the shadows found off the net. I am using a regular rudder servo that comes with the radio and i think it throws 90 degrees so half each way? The weather helm was fixed, had to bring the center of effort forward.


Small thought! You say that your rudder throw is 45deg each way. That is getting into the realms of rudder stall if it is thrown over as much as that. Try reducing the throw a bit by reducing the pitch diameter on the servo horn and/or increasing the pitch diameter on the tiller arm, or adjust the end points on the transmitter if you have one of those fancy all singing all dancing ones. An IOM should turn on a dime if set up, no matter the wind. Has the keel and rig been installed at the proper fore and aft position. Did you get the proper distance aft of the bow for the keel and rig off the ‘net’ or just the shadows? Centre of lateral resistance of the hull vis a vis the keel fin is very important.

More importantly, keep experimenting.



You are right experimenting will be the best. I was only on the water for 1 hour so I have lots of work to do. I just found that when the boat was healed lots (top end of A rig) I found that there was not enought rudder in the water to turn?

Revert to comment in post#2

At the top of the A range, the boat will be heeling a lot going to weather. If you apply rudder at high heel angles, the rudder does little to turn the boat; it is too sideways, and so tends to lift or depress the stern. It stalls very easily and is overpowered by the sails.

In stong winds, let the sail off first and the boat will come upright. Now the rudder will turn the boat. With practice, easing the sail and starting to apply the rudder become more integrated.

If the sails do not go out far enough, that could make turning down wind much hader. Make sure that your sails go out to 90 degrees. In other words, at full out, does the boom hit the shrouds?

Thanks John,

Couldn’t have said it better myself.


I have a different take on rudder throw. Under ‘normal’ conditions, as you turn the rudder the boat begins to turn. You then progressively increase rudder throw and the boat turn increases. When you are skilled, you can have a rudder throw of 60 degrees and not stall the boat. The reason is that the rudder is never making more than a 15 degree angle to the local water flow (ie is not ‘stalled’), provided you match your throw to the boat’s turning. My suggestion is that you should set up an IOM with a minimum of 55 degrees throw, preferably 60 degrees, and practice your tacking skills. The issue isn’t ‘how much throw’; rather, it is ‘how are you using your throw’…

Hi Lester,
I was visualising a rudder being snapped full over with a mainsail still pinned in for on the wind at top of the range. Unfortunately (maybe thankfully) I am not a theorist. I am the type who do’s what works for me. Next time I am in top of range conditions, I will do a bit of experimenting and increase my rudder throw on my not quite all singing all dancing TX and see what happens.



While it may (or may not) be a comparable - new multihull owners experience similar issues when trying to tack. Having experience of a single hull boat quickly responding to a “snap tack” or “hard rudder throw” they often find themselves not tacking or caught in irons - head to wind.

A slower rudder throw, and following Lester’s example of steering through a turn “following” your boat, rather than forcing it through a turn is often a quick fix. Letting sails out and footing off slightly also aids in getting a nice “turn” of a multihull, and those same techniques might favor a better tack - working on practice and knowing how the boat will respond.

By starting out and tacking slowly, easy rudder movements, sheeting out the sails and turning through the turn should get a boat from one tack to the next.

We can actually stop a multihull by applying the brakes when too early to a starting line by rapid and hard rudder movements - and with their light weight and absense of lead keel, they accelerate as quickly as they stop.

For practice try making a much larger radius turn and try to time your tack to coincide with wave patterns. Use the waves if you can to help push the bow over and onto the opposite tack. As you get experienced, you will find the optimum rudder throw, sail position and speed of the boat to allow a nice tack. Only a suggestion, but a couple of areas where you might focus on.

Thank you for all the idea’s, now i just have to find time between kid stuff and wife stuff to get out sailing. My main problem was turning down wind from really healed over. If I let the sails out they hit the water and the boat rounds up. So as per my first post is this a common thing with rc sailboats?

Does it do this if you try going off a broad, deep reach first? (i.e. - not directly downwind, but maybe 30-40 degrees angle to directly downwind).

If you are reaching instead of beating, can you steer downwind from a reach, or does the same thing happen?

Possibly the rudder has stalled out or is nearly stalled. If boat steers well in light to medium wind and you can transition to downwind, I am thinking the rudder - in conjunction with the sail let completely out and trying to turn may be a possible cause. When you get back on the water and heeled over, let sails out only slightly, bear off from the wind slightly, and then try making your turn with the rudder more vertical in the water. If both jib and main are on same side of boat downwind, there is more of a rig imbalance than if the sails are on opposite sides. This can “contribute” to a tendency of the boat to round up. Finally, verify center of effort on sails compared to center of lateral resistance on keel/hull. If CoE is quite a ways behind the CLR it will cause a tendency to have lots of weather helm - but that should be noticeable when sailing upwind - you have to keep steering away from the wind in order to go to windward.

What you describe should not happen if the boat is trimmed correctly. It may be possible that your comment of top of A rig was an understatement and that the wind was stronger and you were really overpowered. Were you heeling more than 45 degrees? If you were at 50 or more, then you were overrigged and there will be control problems.

If your sails hit the water, you may be letting them out too fast.

If you let them out and yet round up, then the jib may be going out faster than the main.

In top A conditions to bear away around a mark, I start easing the sails as I come into the mark and gradually feed in rudder as I continue to ease the sails. This keeps boat speed and the rudder does not stall.


I think you are right the boat was healed over 45 and more in the gusts. My first IOM had a Hitec drum winch, so it let the sails out slow, this IOM has a Hiteck 815 sail arm so things go a lot faster. I will try more things when I get out next, I will also look at making a B rig.
It is hard to know how the boat is to perform because I am the only one at the pond and have never seen a RC sailboat live only on You Tube.


You might try this link. Go down the page to Canada. There is some contact numbers and stuff for the Calgary Model Sailing Club.

Thanks Don,

That is a old number, I talked to the guy a couple of years ago an he was not sailing anymore. I am trying to find people that moved from the coast or live here and like to sail, I plan on having both boats out to let people try. Maybe build a little fleet.