Can you steer in a straight line?

RIN

RIN

Well-Known Member
Joined
2 Mar 2003
Messages
3,236
Location
West Midlands
Visit site
Comming back from cherbourg in a very flat sea, I found that either using the compass or the rolling road on the GPS to help steer left me continuously having to make changes to the helm i.e. the best I could keep within was around 15 degrees either side of my intended track. Opinions on this being normal or indicating a steering problem would be welcome. Boat is twin engined 29 foot with power assisted steering traveling at 20-22 knots. No autopilot
 
that would have been my wake you were following then........

seriously I definitely find it a problem and have always found helming yachts to a 'mark' easier than steering a straight course with outdrive(s).

the only solution for me is to concentrate hard on the compass - but I find a relaxed meandering course more fun.

was going to head for Cherbourg Sat but got talked out of it as we would have been alone- nice crossing both ways?
 
Is this because the boat is wandering even though you were steering a straight course, or an inability of you to keep to a heading for extended period, as the two are different.

If the boat is wandering that much at speed, then the set up probably needs looking at.
If you are finding it hard to maintain a course by compass or gps, then don't, there is a better method. Point the boat on the correct heading, then find a suitable landmark to head towards (aiming at land this is easy) but out at sea usually just as easy, find a distant cloud formation, then just aim at it. 5 minutes later, correct heading from compass or gps, and aim at new cloud formation. It's much easier to aim at a distinctive cloud formation, or a bit off it, than to continually read compass heading, especially when compass moving a lot at sea. Using this method was only a degree or two off when doing dead reckoning runs over 10 or more miles when doing my Advanced course, and I do the same when on long runs, and gps 'bread crumb' track usually shows how accurate it is.
 
Hi Duncan

You'll be surprsied to see me on this forum but I've recently started to acquire some mobo experience in the form of working for the Auckland Coastguard. Spent this last weekend driving around:

1. A 8m RIB with single 200hp volvo diesel outdrive
2. a 8.5m RIB with twin 150hp Yamahas

Lots of exercise inc. close maneouvering and steering the twin engine boat without using helm, some high speed work in rough seas etc etc. Found that at low (non-planing) speeds the single engine was more stable than the twin o/b and less prone to wander/yawing.

Lots of fun and not my pertrol bill!

Alpha1.jpg
 
Yea, but on a good day when theres nothing to sight on, it's hard work, clear sky in the day, no stars at night /forums/images/graemlins/wink.gif
 
Duncan
only came back on Saturday - had been to Jersey previously - left at 0500 BST and wonderfully flat sea but we did have quite a bit of fog
 
Brendan
I could not keep the heading for more than a few minutes. After looking at the GPS and getting back on course, leaving the helm in that position whilst looking ahead for any likely objects in water I found I was 15 degrees or so off track very quickly (the helm had not moved). The result was a continuous series of zigzags as witnessed by my wake. It was overcast and foggy so there was no possibility of using cloud formations
 
Yes, Brendan your method works well for me as well.
Mind you I find that there's no way I can keep a straight course at displacement speeds, whatever I aim for. Why do outdrives tend to make one wander left/right/left/right ad nauseam ?
 
[ QUOTE ]
Why do outdrives tend to make one wander left/right/left/right ad nauseam ?

[/ QUOTE ]

Because they vector the thrust from the props hence any movement of the drive leg is magnified in its turning effect (inc any slack between helm wheel and outdrive).

This is why an outdrive boat will out-turn the same hull fitted with shafts, depending on your point of view outdrives are "twitchy" or "very responsive" and shafts/rudders are "stable" or "slow to respond to the helm".

Selecting full down tabs will improve the displacement wandering habits of most outdrive hulls....won't cure it though.
 
GPS will provide a track over ground, you are travelling through water and therefore are constantly taken off course by tide, that’s why you should have a cross track error / rolling road to follow, the best bet is to try and keep vessel within the margins. If you are cruising at high speed stern drive vessel on the plane will wonder side to side marginally but not enough to take you off track?
 
I was aware of the direction of tide in the channel but the boat went both to port and starboard. I did try to keep it within the XTE which was set to 0.05 Nm (yes much too small) but I couldn't. I do have twin sterndrives.
Of course it could be the helmsman...........
 
Reading your replies, yes, the boat will wander if left to its own devices. Most boats have to be actively steered unless you have autopilot. Even steering by GPS which filters gross changes in direction will allow you to keep quite a straight course, but you will have to concentrate on it, and assign someone else to lookout duties. You can keep a gps heading to within a few degrees quite successfully for over an hour or so, then the concentration becomes a bit much, and might want to hand over to someone else. This comes from practice, so might want to train family/crew in it before you need it. Can suggest some good exercises for this.
 
Thanks, that well explains how it can wander. I already use the tabs down situation. I must check to see how much slack there is in the steering.
What surprises me is that at slow speeds ours wanders to port for about 5-6secs then goes to starboard for a similar time. People who are not used to helming her tend to saw the wheel from side to side. In fact you hardly need any steering input at all as the gentle veerings seem to be largely self cancelling.
 
Even on a high speed planing boat on the Thames this was the case, at 4 knts. It would head alarmingly at one bank, then back to the other. Until you worked out that leave it alone and it would point in vaguely right direction with little input. At planing speed though, the side to wavering seen at low speeds is not evident unless there is a major problem - it's more likely to veer off gently in one direction unless waves or other disturbances affect things. Low speed side to side, but vaguely in correct direction, not the same as planing speed
 
Yup Aily's Comet going great thanks although with cooler weather it's mostly day sailing and fishing rather than extended overnighters. It's hihgly vairable - one day it can be damn chilly and another you are sitting outside eating dinner on the deck at 6pm watching the sunset. But more consistent summer-style season should be back again pretty soon.
 
[ QUOTE ]
ours wanders to port for about 5-6secs then goes to starboard for a similar time. People who are not used to helming her tend to saw the wheel from side to side. In fact you hardly need any steering input at all as the gentle veerings seem to be largely self cancelling.

[/ QUOTE ]

Ours too - nature of the beast. Makes it interesting for dinghy sailors who >think< they know where you're going.... /forums/images/graemlins/laugh.gif
 
You must log in or register to reply here.

Share this page

Top