Thread: Man overboard!!! Learning to sail PDRs and others in stronger wind.

Howdy Nick, I am amazed the boat didn't capsize.

One thing that is useful is always to have the mainsheet in your hand. When the wind is stronger it is risky to let the boom out to 90 degrees to port, because the top of the sail will go past that and give you heeling force to starboard. Or vice versa.

So in lighter winds it is OK to ease the boom out to 90 degrees, but in stronger winds only ease it out until the TOP part of the sail is at 90 degrees. With a tight downhaul and good halyard this might be with the boom at around 70 degrees eased with the lug rig.

With the sprit rig - which resists twist better (assuming the snotter is tight) maybe you can ease out to about 80 degrees.

In other words in stronger winds it is important to watch the top part of the sail when going downwind.

This also means you have to have the mainsheet in your hand. Holding it means that even if the boat gets away it will capsize.

Because everything works so well in the little boat it will still sail really well reefed down one or two reefs and will be heaps easier to handle.

Another good rule is if you are thinking where to go ... head upwind first (unless sure of a wind change later). That way you can usually get back to where you left more easily.

Good work ... you survived and learned something.

Glad you are getting some sailing in.

MIK

Nick,
I have experienced the same hysterical event although I didn't get dropped in the drink.......well not yet.

The main cause of what happened is having the centreboard up when going downwind the size of the lug simply takes over from the rudder. Think of flying a kite, the rudder has no turning moment with the CB up. The other phenomenon you experienced was the dreaded death role caused by the yard being further forward than the boom when it is set square thereby forcing the boat to heel to windward.

Both very exciting conditions.

I would play with the boom/yard position relative to the mast before changing the rake that will have much more influence on weather helm or lack of it. As for nose diving anticipate the puffs and lean back easy really.

Keep at it.

In the second pic you can see the bow going under..

Video: [ame=http://www.youtube.com/watch?v=ngfqwetp7o4]YouTube - PD Racer[/ame]

It always impresses me how far the bow of a PDR can go down and the boat not do anything silly.

If it was almost any other sort of boat with a bow this deeply immersed the result would be very different.

MIK

But why does that happen? Too much forward rake?? too little downhaul?

Mik, is there a way for you to measure the distance from the tip of the mast to the stern in the cad program? in order for me to calculate of the rake is correct? Ideas?

Originally Posted by m2c1Iw

The main cause of what happened is having the centreboard up when going downwind the size of the lug simply takes over from the rudder. Think of flying a kite, the rudder has no turning moment with the CB up.

The other phenomenon you experienced was the dreaded death role caused by the yard being further forward than the boom when set it is square thereby forcing the boat to heel to windward.

That's very interesting. I have never quite understood the final light downwind capsize I suffered in RAID41. The death roll issue was not involved, I suffered that 35 years ago. trapped under the hull. never again.

However, your point about having the dagger board up, and the rudder having nothing to steer against sounds like it could have been the problem. These very light flat bottomed boats have nothing in the water, especially no keel to grip the water, so possibly the dagger becomes essential at all times. even down wind.

When I was racing downwind, the first lap was fine, dagger down, but the Solo dinghies were passing me. So on the second lap, I raised the dagger to increase downwind speed. When I gybed in these light wind the boat just rounded, the hull slid up from under me, the rig heeled over and capsized. Everyone amazed and a shocked me in the water.

Perhaps there's an important lesson here about very light flat bottomed boats downwind?

Brian

Hi Nick, glad your ok, as we were saying - so much to learn! Your lug rig looks really nice. I would like to talk about this photo though,



See how the boom is lifting. The mainsheet just pulls almost horizontally with no downward force on the boom as it does on a reach or upwind. this allows the wind forces to lift the boom. Although the downhaul helps a bit to prevent this, it can be clearly seen at this angle, in this wind it cannot hold the boom down.

So the boom lifts and the top of the sail moves further forward, twisting off more than the boom. When you sail even further off wind, a dangerous situation occures. With the boom less than 90 degree out, the wind on the lower half of the sail may still be flowing from the leach to the mast, but the upper section starts to flow from the mast to the leach. As you let the sail out a bit more suddenly all the ind is going from mast to leach and you are sitting on the wrong side of the boat. All the forces have changed around, and sitting where you were before when the wind was going leach to mast, means now that the forces have swapped you are sitting on the wrong side of the boat and your own weight capsizes the boat.

It's hard to write this, but the conclusions are simple.

1) never let the sail out past 75/80 degrees. Never 90, because the top of the sail will be already past 90 and the wind will be going mast to leach.

2) always use a kicker/preventer/vang. After being trapped under a hull all those years ago, I never want it to happen again. using a simple 2:1 kicker prevents the boom from lifting and prevents the top of the sail twisting off, the starting process of a death roll. For me, i cannot contemplate sailing without a kicker and believe that one is needed. This pictures show clearly that a kicker is needed.

Good sailing

Brian

Hi Brian,
To expand, on my first real outing when down at Goolwa Mik, Ted, AJ and I decided on a little race around the flats exposed by the very low river.

My duck with the lug was quick in the light breeze so I managed to get out in front on the windward and reaching legs then downwind I started to relax leaned back for a leisurely win. Well I looked back a one point to see Mik hunting me down (I think he had prayed to the wind Gods).
So first thing we racers do is raise the CB on a dinghy downwind which I did but then I promptly let the mainsheet slip so with the boom well forward of the mast I suddenly found there was no steering control at all. With the rudder trying to resist the extreme leehelm not to mention the roll to windward I was left to contemplate my next move and it would be carried out very gingerly as I didn't want to embarrass myself by a capsize in front of the designer.
Just as well the breeze was light because I managed to sail for some distance essentially sideways, very entertaining.

OK I admit it took me a while to realise what the problem was but I eventually pushed down the board which returned some control. The difficult part then was the sheet as each time I hauled it in it induced strange affects on both hull direction and stability. These lug rigs are a strange beasts.

So I too can vouch that a flat bottomed lug will side slip remarkably well.

Cheers
Mike

Mike, that's exactly what it felt like to me, great description...

Originally Posted by keyhavenpotter

See how the boom is lifting. The mainsheet just pulls almost horizontally with no downward force on the boom as it does on a reach or upwind. this allows the wind forces to lift the boom. Although the downhaul helps a bit to prevent this, it can be clearly seen at this angle, in this wind it cannot hold the boom down.

I was thinking of running the block free on the traveller line in an attempt to improve the downwind sheeting angle at the expense of upwind but

2) always use a kicker/preventer/vang. After being trapped under a hull all those years ago, I never want it to happen again. using a simple 2:1 kicker prevents the boom from lifting and prevents the top of the sail twisting off, the starting process of a death roll. For me, i cannot contemplate sailing without a kicker and believe that one is needed. This pictures show clearly that a kicker is needed.

a kicker perhaps even adjustable would be much better.

Thanks Brian
Mike

Thanks to every one for the advice and input! It is so great ot be able to draw on so many skilled and experienced people for information!

Ok, to check out my mast rake I have printed off the side view picture on the lug rig plans onto an over head transparrancy. I wil setup the boat with just the mast and then stand back, hold up the OHT and align the boat's hull with the OHT picture and then check the mast rake. I know its not awefully accurate, but it will get me close I think...

I have also photochopped a pic of the boat and the lug layout see below. Its pretty clear the mast is raked forward!

Cheers.

Hi Nick,

I would be inclined to try the kicking strap ( at least it will help when going downwind - and it will not adversely affect performance at any other times ), and tie a temporary knot in the mainsheet that limits the boom travel to just 70 degrees from the hull centreline, just to be safe, I would just see how that works, before considering making any change to the mast partner to alter the mast rake.

My sailing experience os mostly with RC Model Yachts, with racing sails, and many modelers actually deliberately rake their masts forwards, as they claim it makes the boat faster, I have no experience with this aspect, but based on this, your accidental raking forward of the mast may actually improve the speed of your boat.

My advice would be to ask Michael if he knows anything about adverse, or other affects on performance by changing the rake of your mast, with a lug rig, before commiting to make any changes to your mast partner.

Hi Nick, the lug rig is so adjustable on positioning depending on where you fix the halyard and downhaul and how you pull the downhaul and mainsheets on that I am not sure the mast rake is a problem. It's fairly easy to move forward or backwards, my moves loads just by pulling on the kicker first or the downhaul first. I spend all my time getting it as far forward as possible on my Scow!

Guess MIK will know if he feels there is a problem, but to me the capsize was related to the issues we have covered, such as boom angle and boom lift, rather than mast rake.

I would try these other suggestions first before cutting the boat about.

Brian



Brian

Howdy Nick,

The rake will make very little difference to the situation. It is common to all PDRs. Just move about a foot further back in the boat and you will find the boat accelerates and the bow goes way up in the air once it accelerates.

With practice this becomes little more than a leaning back in the boat when you see a gust about to hit and then leaning forward as the bow pops out. Then when the gust ends you sit upright again.

The thing to realise is that in any other boat in those conditions, you as a first time sailor would have had very little control and probably multiple capsizes, but you almost survived in a PDR. Mostly because it has such large lateral stability and that it usually likes going in a straight line even when excessively loaded up by wind pressure.

There are three main lessons out of this. In light winds you can happily have the boom out at 90 degrees, but in stronger winds just make sure the top of the sail is only out at 90 or a bit less - and be brutal with the downhaul.

The other is to move further back when the bow goes under. You do have to go quite a bit further back than normal sailing position if the bow is already in deep, but you can prevent it from going in if you pre-empt the gusts.

Finally keep the mainsheet in hand in case the boat runs away from you. I always make sure one foot is under the toe straps as well - if the boat starts going over, then go over with it - in this situation, the boat sounds like it started to go over and you went over only attached by the tiller extension. The toestrap method is not 100% like holding onto the mainsheet,but it can be helpful at times - as many of the more experienced racing sailors know.

Also some reefing would have made sense on the day.

Keep going, there is nothing too wrong about your boat and the rake won't make much difference at all going downwind. It might change the helm balance a bit going cross wind or upwind, but the balance with a lug is quite good because there is sail either side of the mast so the drive is balanced. With a Laser or other conventional sail, everything is on one side of the mast so does provide quite a bit of pressure for the boat to turn.

I will just get a measurement for the mast rake off my drawing - but I really don't think it is a problem.

Best wishes
MIK