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benny

Cartwheeling (nose diving)

33 posts in this topic

raking certainly helps alot to prevent nosediving.

What you did by steering upwind a little when the nose bury's is correct and then bring it back downwind again when the nose lifts or the windward hull starts to lift. There is a technique in this that just takes practice.... and sometimes even with lots of practice it jsut does not work smile.gif

Any reason not to use rake?

cheers !

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Thread resurrection!

I took a newbie mate out for a sail today. Sloop rigged, about 160kg all up, in about 15 knots.

He wasn't so keen on sliding back and snuggling with me on the back beam, so I was having to round up into the wind all the time to keep from submarining the downwind bow.

Then we were about to go down the mine again, on a port tack... with a couple of kids struggling to control their 420 under spinaker on starboard reach, coming down upwind of us. If I rounded up we would have gone straight through them.

Long story short, there's a whole lot of mud on my starboard bow, and my forestay snapped when we went over. I came up under the trampoline and immediately knew that something very bad had happened... the tramp shouldn't be flat on the water in a 5' deep lake :-/

Now I'm trying to read up on ways to keep the bow up. I've had suggestions of pulling more jib on, letting jib off... looking at the (dodgy) video, it looks like we had a heap of mainsail draft, and not much downhaul. I'm still learning how to use the downhaul to control sail shape, but wonder whether pulling more downhaul (and outhaul) on to flatten the sail and bring the draft forward might... uh... make things better or worse or do nothing at all?

I did have a little more baton tension than normal - I'd basically rigged for power, thinking that extra power would be handy with the extra weight on board.

Does raking the mast work to pull the bows up work when sloop rigged?

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I'd think:

1. two up and 160kgs is well over the top, not surprising you went over

2. when the breeze comes up we tend to pull everything in - outhaul, downhaul, luff tension - remember that it you tension the jib luff that'll try to pull the mast upright.

3. with rake on a cat rig you have 5.5m forestays and 5m shrouds when in doubt I'd stick to that

4. not seen anyone else fiddle with batten tension - I don't - just set and forget, leave the battens in and tied all the time, we're out of the cotton sail material now!

5. see note 1

I guess when you lose the rig then the boat will land on one side or the other - you got the short straw.

Glad you survived it all ok.

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As Brittney would sing... oops I did it again :D

Some more submarine action yesterday. Quite a bit of breeze (20 knots + gusts at Ballarat airport, about 15km away, maybe a bit more out on Lake Burrumbeet). Solo (~75kg), so I can't blame my forward hand for being too heavy this time.

I was dipping the bows all day, so I was kinda ready when it went deep the first time. Dropped the mainsheet and recovered.

Second time I was consciously trying to steer through the wind rather than depowering. I rounded up well when the bow dipped, but bore away too soon and sent it down in to the mud. Stepped over the bows when it was beyond recoverable.

It seemed to me that the bows were more prone to diving when I had too much boom lift - traveller too far in, mainsheet eased off. Dropping the traveller further out and sheeting on harder seems to pull the centre of power further aft, lifting the bows.

I rigged with a slightly longer forestay strop than usual (I made up a couple of options when I re-rigged the forestay after the incident a few posts back), so the mast is raked a bit more than I've done before (which also should have pulled the bows up, by my thinking, unless I'm getting a weird interaction with the jib slot). Lots of downhaul and outhaul on the main.

I'd also like to point out that I'm getting plenty of successful sailing in, in between these screwups :p. And I'm deliberately pushing the envelope, seeing where the limits are, so it's inevitable that I'm going to find them sometimes. I'm just very analytical and like to figure out _why_ :-)

Tim

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The photo above shows the front beam flattening, may just be camera angle, or may be that dolphin striker is way to loose, or due for replacement,

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Pretty sure that's just camera angle. My striker is tight and in good nick. But I'll triple check next time I'm rigged and tensioned just to be sure.

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Check that your dolphin striker is tight before stepping the mast.

Maricats nose dive if driven hard on a reach - that is just how it is.

You can reduce it by racking the mast and de powering by flattening the sail. In strong wind you drive the boat as hard as you are game hopefully holding it just off the nosedive then ease off or dump the main, if you bury it sometimes it will recover other times it won’t !!

Drop the traveller down.

On a reach you can sit behind the back beam this greatly increases the leverage to keep the nose up.

Can’t tell from the video but you don’t use forestays to the bows with a jib, the weight needs to be on the forestay in the jib.

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Watch a youtube on Laser sailing.  They are all over the place going downwind.  One I watched, I think it was a Worlds Gold Medal race - they never gybed going downwind always twisting and turning to get the most out of waves.  I think it was in Perth or Fremantle and Tom Slingsby won.

Not disimilar to Maricats - change direction often and whenever you look like you're going to go down a wave into the back of another one - guaranteed sphincter clenchers!

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