Julian Bethwaite's Skiff Tips

This is extracted from an article Julian wrote for the 29er web site, edited to remove a considerable amount of tuning information which is largely 29er specific in detail, although most of the same principles apply. The original article it is here and is worth a read if you're thinking more deeply about tuning principles
[tuning detail skipped, additions in brackets, Cherub editorial comment in italics]

Body stance in the boat

"When we went sailing 29ers out of San Francisco Yacht Club, it was quite fresh, big seas, all in all quite challenging. [Like Cherubs] 29ers are light but highly powered, but light means that if they hit a wave the wrong way or are trimmed (boat wise) and plug into the back of a wave they will stop. A youngish girl who was normally a skipper but was crewing in this instance, whose name was Molly and whose surname I won't go into details, was just fantastic, she was moving forward and aft, in tune with the waves and punching this boat over the difficult seas to the point that even though there was not much of her, they were going upwind higher and at the same sort of speed as their heavier rivals.
So what do I mean? Going to get a bit technical now. A 29er with a 140kg (308 lbs) crew on board plus the boat sails foils spars and the rest of the paraphernalia weighs in at around 230-235 kgs ((500-520 lbs). It is design to float a static weight when it hits it mark of about 180kgs (400 lbs) so when the boat is stationary it sinks about 12-20mm (1/2 - 3/4 ") further into the water than it should. [This is pretty much the same for a Cherub, except the boat is rather lighter, and the static immersion probably greater - Cherub Ed]. This is no problem because as soon as the boat gets any way on it can easily dynamically support the extra weight, well before planing.
So in light winds when there is not much wind about it is important to understand that you have to optimise the boat for those conditions. If you sit in the boat where you normally would sit in normal conditions then you will sink the transom, so go forward young man (or girl). [On the 29er]... we supply the non skid on the gunwale so it goes well in-front of the shroud and so should you. [and on your Cherub the non-slip needs to go in front of the shroud too].
...God was very nice to sailors and gave them ears and eyes, if you see or hear the bubbles or wake from the transom then you are too far aft. Very simple indubitable rule.
[On the 29er] You can push the bow down 100-180mm (4-7") without significant drag increase in light wind and low hull speeds, the boat has been designed to sail well like this, for those who read my fathers pontifications* this is what he calls the 4th mode. [This applies just as much to modern Cherubs if not more so]
The reason it works is that the increase in drag from pushing the bow further down is greatly outweighed by the reduction in drag from a reduction in surface area and reduction in form drag from having the transom driven too deeply down. Obviously as the wind picks up, you come aft, but the crew can quite feasibly still be in front of the shrouds up to 10 knots. And then as the boat moves faster and faster the further aft you move. This holds for upwind as well as downwind and as you tend to move faster downwind, you will be moving further aft downwind for a given wind speed than you will be upwind.
To say that X immersion of the bow is correct is obviously a impossible statement because it will depend so much on hull speed but a 29er floating on its marks would have the toe of the stem immersed 40-45mm (1 1/2 - 1 3/4 ") and the transom submerged 12mm ( 1/2 ") at 5-6 knts.
So back to Molly. What Molly was doing was moving her body weight to lift and lower the bow as it came to each wave and also pumping the mainsheet to work the boat over each wave. In these conditions there was plenty of wind and plenty of speed so there was absolutely no risk of the transom ever sinking in. In flat water she and her skipper would have been 1/2 the way back along the boat and planning hard upwind. But because the water was lumpy, the excess drag from the bow plunging down and into a wave or from it rising too high, and the boat seeming to "stall", was overcome by Molly moving her weight to smooth out the rises and falls and keeping them in sync with the wave frequency.
This is another thing that sailing fast boats throw at you. If you move slowly across waves then there is plenty of time for the water to react with the boat and the boat naturally follows the wave contours. [True Skiffs] move way too fast for the water to have anywhere enough time to sync in and in most cases go right out of sync which results in the nose plunging into the wave face ahead.
You have to use your weight and the sails to get the boat back into sync and once you have developed a good technique then it will enhance you slow boat sailing also.
Heel
[Cherubs, like] 29ers are not round boats: they are effectively a long shaped wedge with hard corners. Those hard corners aft are what allows you to drive the boat very hard in a lot of wind and enjoy those screaming rides at speeds that you did not think where possible but they do have their drawbacks.
In light air, you need to get them out of the waters so you move forward and lift them out.
Once you start moving a bit faster and you are back in the boat then you can lift them out so you must KEEP THE BOAT FLAT!
And Flat is FLAT, +/- 5 degrees is acceptable, +/- 10 degrees is only just tolerable but by the time you get to 15 degrees then the reason you are at the back of the fleet is very obvious.
The good guys will sail the boat upwind and downwind with the boat within +/- 5 degrees all the time and most of the time if they are heeled its to windward and not to leeward.
There are some reasons for this but without getting too technical, they are:-
1 The boat is designed to be most efficient in one mode and that is upright.
2 When you heel a roundish boat, a bit like if you heel a round ball, nothing much happens but as you heel a wedge shaped hull then as you heel it more and more you screw the water line and the centres of buoyancy so that they form more and more of a curve, and it is in that direction of that curve that the boat wants to travel.
Going upwind if you heel the boat to leeward then the boat wants to round up. Heel it to windward then it wants to bear way. The reason the good guys heel their boats to windward upwind is so that they use the hull to neutralise the windward heel that you should get if the boat is properly in balance and also it make the boat crab to windward and makes the crew want to trim the mainsheet in further.
But most importantly, when a gust hits the boat, by the time the crew has eased the sheets and swung right out the boat will have moved from heeled to windward to bolt upright which is the very best position for the boat to be in and exploit the gust to the maximum capacity.
Downwind, its spooky to heel the boat to windward and you have to have a great rapport between the crew and the skipper but because you now have a spinnaker hanging out the front, it makes the boat want to bear away and therefore gain depth, but it will load up the tiller and make the helm very sensitive.
If you are trying to make a wing mark and need height, you are better off heeling the boat to leeward. The only other time that heeling the boat to leeward works is if you need gravity to fill the sails in light airs.

Julian Bethwaite, 2001

Used by permission from webmaster@29er.com Content (c) copyright 2001 29er.org/com All rights reserved.

* Julian's Fathers Frank writes in great detail on this and many other topics in his book "High Performance Sailing" If, as a Cherub sailor, you only buy one book, it should probably be this one.