One of the guys at the lake today was sailing a Venom and I noticed that the mast seemed quite far back. When I got home I looked at Bob Sterne’s website and the pictures there show the mast as being almost right in the middle of the fin. If I had my mast that far back my boat would have uncontrollable weather helm. Can someone try to explain to me why a Venom has no mast lead and no weather helm. I could see it if it had a 60/40 jib/main ratio but this looks like a 50/50 or 40/60.
I can hear you all now,“there goes Don and his damn weather helm again”. I promise as soon as I understand it I will stop nagging

Hi Don,

This is a ‘paste’ from Bob Sternes tuning guide.

I have a basic rule that I try and remember when I am having problems with helm and/or pointing ability. THE AMOUNT OF HELM IS DEPENDENT ON THE POSITION AND SHAPE OF THE LEACH OF THE MAINSAIL. If it is too far forward, the boat won’t point. Too far aft, and there is too much weather helm. If it has a lot of twist, the angle of heel will be less, the CE will move ahead, and the mast may have to be moved back to compensate. If it is strapped down hard, the boat will heel like mad, and the CE will move aft, causing the boat to head up. The mast may have to move forward to restore balance.

I did not notice the ‘lead’ on the Venom, but I did notice that he was sailing with a huge amount of twist in his main. So his main was not contributing as much as it should and and from the paste above, he has moved his mast back to get balance.

The whole link is

and the section is #2, mast position

Agreed, that may have been the case with the boat today but from the pictures I was looking at Sterne did design the Venom with little or no lead and I don’t think he would run with that much twist. Take a look at these pictures. One is US1M and the other is a 36/600

Note the mast location


If you look at the picture of the 36, the keel is raked aft slightly, and the jib is considerably forward of the mast (quite a gap between the leech of the jib and the mast). Both these would “reduce” weather helm.


Hi again DOn.

The other thing I see in the picture is the relatively huge jib to main ratio.

The bigger the jib, the further forward the COE and so the lead increases and can even be forward of the mast. So the mast moves back to achieve balance again.

I’m getting the impression that you guys don’t think that hull shape has much to do with helm/balance. Am I right?

Hi Don,

This is my opinion.

Balance is a dynamic thing. It is only relevant when the hull is moving through the water.

When the boat is moving it is also heeling to some degree. The immersed shape of the heeled hull is asymmeric (like a lifting foil), and so generates some lift and so has an effect on lateral resistance and so causes the dynamic CLR to move.

So, Yes. The hull shape is a factor. However, once you have build the hull, it is not (readily) possible to control it. The shape is fixed. The fin is locked in its fin box and so is also fixed. But is easy to control the other variable, the rig.

Bob Sterne writes that the balance changes constanty with wind strength and therefor with heel angle. So both the CLR and COE are dynamic. Hence the need for constant ‘fiddling’ with the rig.:devil3:

There! That exhausts my knowledge of nautical engineering.:zbeer:

Sorry, I was thinking of “what do I do on my next boat” when I posted this. One other thing I noticed is that when the Venom was heeled the stern didn’t stick up in the air like my boat. It(the Venom) stayed nice and level. Is this because of more buoyancy forward?
I should have asked all this at the lake but most of it didn’t occur to me until the long drive home. Anyway this way someone else might learn something too.

I think I have figured what you are really getting at.

First, let’s talk about mast position and ‘lead’. Really, this is just ‘happen chance’. For example, take a hull. Rig it with a single sail, a mainsail only, like a Laser. The mast would be way forward of the fin for the boat to be ‘balanced’. Now take that same hull and rig it with a single sail, a large jib only. Now the mast would be quite far back and certainly, behind the fin to achieve balance.

If we took that same boat and rigged it with a small jib and big main (say 25%/75% area distribution) , say like a Star, then the mast would be forward. But take the hull and put a big jib, small main (say 60/40) and the mast would be moved aft.

So this thing we call ‘lead’ is really not relevant. It’s just where the mast needs to be to support the sail plan to get the balance right.

There is endless discussion on hull shape to affect balance. One idea goes that if we build a hull with arcs of a circle, then the immersed hull shape does not alter very much and so balance is not changed very much for increasing heel angles.

A boat with a flat bottom and sharp turn to the bilge will change its heeled profile more than a circular shape and so balance may shift more with heel angle.

Another concept is ‘canoe bow/stern’ or double ender vs a fine bow, wide transom. These have very different sailing attitudes at different heel angles. The wide transom will put its bow down at high heel angles, while the double ender will tend to track more level. The Venom is very narrow at the transom waterline.

There is no ‘right answer’. I suggest that you look for a hull that sails well in your predominant sailing conditions ie windy vs light airs. (and preferably an IOM. . .in-joke).