Skip to main content

Author: Rob DeWitte

Backwinding: Mainsail luff curve

Rob DeWitte Leave a comment

Yesterday when sailing on Battlewagon, I noticed that their mainsail never backwinded, even in relatively strong wind.  In particular, I noticed that is was significantly less deep than ours.  It had a shallow draft — much more shallow than on PERSPECTIVE.  There was about an inch or two of pre-bend in the mast.

And that made me think about the connection between pointing, backwinding, pre-bend and the design of the mainsail.  It seems to me that we didn’t have as big a challenge with backwinding prior to this season.  But now that the forestay is shorter and we are pointing higher (especially with the flat #2 and #3 headsails), we have this annoying backwind in the mainsail.

Intuitively, we all want to clean it up, and we believe that there is more speed to be found when we do that.  But, the steps we take to clean it up come at the expense of the mainsail leech shape, and generally we don’t gain any speed — sometimes we sail faster with a pronounced bubble in the main.

Rig tuning is clearly a factor, as I wrote recently.  But what if the mainsail is simply cut too deeply?

This morning, this idea popped into my head, and it made me think about how difficult it had been to point with the new Doyle #3 headsail before it was re-cut and the forestay shortened.  That headsail had been designed with a deep shape to give the boat lots of power, assuming that it was the only headsail the boat would have.  The main we are using now (also by Doyle) was also designed at the same time with the same designers, making the same assumption:  no overlapping genoa, therefore lots of power needed from the mainsail.  In other words, the sails were built for power, not pointing.

Before last season, Gil and I measured the Dole mainsail and headsail  and the original Quantum #3.  Sure enough, there was a huge difference in the luff curve of the two headsails.  When we switched to the original #3, we could point higher.  With that in mind, we used the Quantum #3 until it fell apart (it had been damaged by the sun during the first season — another story).  And based on that experience, I had North sails recut the Doyle #3 until it is the nice flat headsail we have today.  (and that also lead to shortening the forestay).

But we never measured the original Quantum mainsail to compare it with the current Doyle mainsail. So, this morning I did that.  Here’s the comparison:

Bingo!  The original Quantum mainsail (blue ink) has 2 1/4″ less luff curve than the newer Doyle mainsail.  It is definitely shallower than the Doyle mainsail.

I’d like to try the experiment of using this mainsail in the upcoming races to see if we can tame the backwinding without compromising speed.  Yes, we’ll need some pre-bend too, but maybe only half as much.

Some additional thoughts

  • The Quantum main is in very good shape.  Unlike the #3, it was not exposed to UV light.
  • If this works out, our standard sail plan may well be the Quantum mainsail and the #2 genoa, shifting down to deep powerful sails (main and genoa) only for very light winds, when power is more important than pointing.
  • We’re likely to have less weather helm with a flatter mainsail — better pointing, better balance, better speed.
  • I’ve noticed that Top Gun has two mainsails — a new black one for windy days, and their older transparent one for light wind days.

Let’s give it a whirl and see how it goes.

 

 

JFest aboard Battlewagon

Rob DeWitte Leave a comment

Kersplush! Kersplush!

Big waves today at Ashbridge’s Bay, as Lazy Sheet and I helped Battlewagon around the course.

Yesterday we had to wait several hours for a hint of wind and then put in two light-wind races, getting used to the boat and the ways things are done.  Good thing we had that practice.

Today in bigger wind, and very big waves (6 feet average, some as big as about 8 feet!), we all needed our wits about us and a firm hold on the boat to move around.  We had Battlewagon’s rail burried, and the spray that came as we crested a wave and splashed into the next on was like MarineLand when the killer whales breeched.

My whole world is still bobbing up and down.  Here’s a taste of what you missed:

Drifter

Rob DeWitte Leave a comment

Today the weather played every tune it knows, but it didn’t give us much wind.   The morning was gray, the early afternoon it poured, then the sun came out and the wind disappeared.  Slowly, slowly the wind built to something pleasant.  Slowly, slowly it faded away.  And slowly, slowly we sailed around the course.  It was warm and sunny and there was live music from Hamilton’s shoreline. A splendid evening, but a little more wind would have made it perfect.

Drifters like this are tricky.  It’s hard to stay focused, yet focus is needed to keep the boat moving and find the ideal trim.  And just when you’ve got the boat going, the wind shifts or fades or builds and you have to start over.  And there’s too much time to think about tactical and strategic decisions.  Too much time for second guessing, and regretting.

The race began with a fine start, leeward of Top Gun, just astern of Legacy, and we pushed far to that Hamilton shore.  Sandpiper had the same idea and pushed even further than us.  But once we tacked over onto port we had trouble building boat speed and fell into some holes.  Even so, we rounded in a good position, hoisted quickly and searched for the wind.  There were little puddles of wind here and there, too many choices, none of them great!  Battlewagon kept it simple — sailing high over toward Hamilton and jibing back to the mark.  It was the best choice.  Top Gun, Legacy and Big Yellow, jibed over toward the middle of the bay.  It was the worst choice.  We split the difference, and were able to close in on Big Yellow by the leeward mark.  In fact, there wasn’t much distance separating the fleet at that point.

As we prepared our douse, on port jibe fetching the mark.  Big Yellow approached on Starboard jibe.  I called out offering them mark room — they had a definite overlap on us — but they kept calling out Starboard, and aimed right at us.  Odd.  They were deliberately overstanding the mark, and preparing to jibe?  In typical fashion, they wanted to engage in robust dialogue while on the course, an invitation I declined.  We doused, headed across their stern rounding to windward of them, puting in a ‘quick’ tack back toward Hamilton.  Meanwhile they got stuck in a cloud of sails, as smaller boats had by now established a position between Big Yellow and the mark.

Here’s the replay

So, we were in a great position relative to our fleet, and sailing in the direction we wanted, but then the twitchy wind and the details of sail trim got us.  Slowly we lost ground to Big Yellow.  Then Sandpiper overtook us like we were standing still.  And finally, it looked like Eclipse might overtake us before the finish line.  We rallied our focus, found another half knot and made darn sure to put ourselves between Eclipse and the finish line.

With a sigh of relief we crossed ahead of them.

Drifters just prove how much we still have to learn!  Proof?  Chatting with Bob Duggan at the dock afterwards.  He had a terrific race!  I felt like young Luke Skywalker talking to Yoda.  Time to go get some power converters!

(But the engine works now!)

 

Threading the needle

Rob DeWitte 3 Comments

What an unexpected thrill ride!

And what a fantastic crew!

As we gathered at the dock on a sunny warm, calm evening we all had the same thought — not much wind, but a welcome chance to enjoy a lovely summer evening on the water.  And that’s how it began.

In fact, there was a bit more breeze at the start than we reckoned, a pleasing 7 knots or so.  Great!  We won’t struggle to keep the boat moving.  We even noticed a nice patch over on the Burlington side but none of the sharks were going for it, so we opted instead to go toward Hamilton.

Our start wasn’t bad, but a little late.  Under a cloud of canvas we opted to sail low and fast over to the better air at the Hamilton shoreline.  ReMarkable had the same idea, and pushed into the shore ahead of us, while the others tacked earlier to stay in the middle of the bay.

And then an unexpected wind shift hit us at the perfect time:  it backed just enough that when we tacked onto port, we were laying the mark!  That meant more time sailing upwind for the others in the fleet and a quick fetch for us.  The wind had also begun to build.

As we approached the windward mark, we had to cross the path of many boats that had begun their downwind leg.  It was great fun threading the needle among the beautiful spinnakers to claim our spot: we rounded just behind Top Gun.  ReMarkable had a commanding lead.  And this is how tonight’s video starts — sorry about my backside in the foreground, just focus on the periphery, where all the action is.  You’ll see us finding a line through thick traffic during which we did not have the right of way at all.

As there was no time on the layline, our hoist took a few extra moments, but then we powered up with Top Gun in our sites.  With the wind shift in place, it was a drag race to the leeward mark and the wind began to build even more, with some pretty strong gusts.  We watched the boats ahead to see where the gusts were.  One by one they nearly broached as a gust caught them unawares.  We were ready though, kept the pole nice and low, and begain to steer downwind as soon as the gust began to hit us.  As a result, we kept the boat flat and fast.  It was total concentration and great fun!

A clean douse a little early, around and back up.  It wasn’t a fetch all the way to mark #1 so we chose to tack early, and used Pandora II and Coyote to judge our line to the windward mark, splitting the difference between their choices.  Coyote had it right and we could have pushed a little further toward Hamilton, but at least there was no risk of overstanding.

Battlewagon and Sandpiper opted to stay along the Burlington shore, and we all got a lift when we needed it.  As a result, they were able to avoid the extra tacks we had done, and Battlewagon rounded before us, with Sandpiper astern.

Hoist again, clean again, and now it was a downwind drag race with Battlewagon.  We quickly came even with them as they took a bit longer to hoist and had traveled a bit further toward Hamilton.  Separated by 5-10 boat lengths we wrestled side by side down the bay.  Now they would pull ahead a bit, then we would catch a gust and gain on them.  Neck and neck the whole way.

Time to douse.  Clean for both.  They had a slightly hotter angle to the mark and pulled clear ahead.  I gave them mark room.  A shark had the inside lane on them, Chris had to give the shark mark room, and a window of opportunity opened up.  A very narrow window.  More like the eye of a needle.

As the shark doused and rounded, I swung wide before the turn, and then turned hard into the gap between the shark and Battlewagon, nearly clipping the shark’s outboard engine and squeezing into a tiny space to windward of Battelwagon.  Everyone was ready and we hardened up  just inches from Battlewagon.  Close enough to discuss world affairs.

Yup, we threaded that needle too!  (too bad the camera had been bumped, and was pointing a bit at the sky)

But with the wind up in the 12 knot range, it was really time for the #2 genoa.  The black one that is nice and flat and lets us point high.  The #1 is quite deep, and soon we could feel the effect of this.  Battlewagon pinched and pinched until we couldn’t fill our sails and we slipped gradually astern, giving us no choice but to foot off and sail for speed.  This meant an extra two tacks for us, conceding the race to Battlewagon by about 30 seconds.

Meanwhile Sandpiper crossed not far behind us.  It will be interesting to see how all this comes together after PHRF handicaps are applied.

And there are some lessons to learn in here.  Should we have changed headsails?  Could we have done it?  Should we have tacked away from Battlewagon, rather than losing the pinching match and footing off?  Was the backstay on hard enough?  Good things to ponder.

But for now, we will ponder the great thrill of threading the needle at both ends of the course!

Rig tuning and backwinding

Rob DeWitte 1 Comment

One of the ingredients of our success yesterday evening was almost certainly some renewed focus on rig tuning.  So far this year, I dialed in something approximate and have left it at that.  It was a conversation with Doug Folsetter that got me back to thinking about it.

I described to him the fact that our mainsail was getting heavily backwinded above about 8 knots of true wind speed.  First he said what others have said — that it’s okay to sail with the backwinded ‘bubble’ in the luff of the mainsail.  It can be a very fast mode.  But then he went on to describe how he’s tamed that situation on his Viper 830 — a tighter rig tuning with significant pre-bend.  After making these adjustments and fine tuning for a couple of years, they are now able to keep their mainsail powered up in conditions where it used to be ‘inside out’.

Why?  Well, I’m no expert, but here is what I’ve been able to piece together.

  • When the wind fills the genoa, the forestay pulls the mast to leeward at the hounds (where the forestay and the upper shrouds meet the mast), unless there is enough resisting tension in the upper shrouds.
  • When the wind fills the mainsail, the mast bends to leeward all along its length.
  • This effectively increases the depth of the mainsail along the mast
  • Air flow in the gap is insufficient to support that much depth in the mainsail, whereas there is plenty of air flow on the windward side and the net effect is an inverted pressure gradient near the mast, that creates the bubble.
  • The bubble extends aft until the airflow coming off the outer surface of the genoa meets the leeward face of the mainsail, and the desired pressure gradient is restored
  • Tightening the backstay in these conditions is only partly effective, because it tends to bend the mast laterally as well as forward and aft

So, to combat the mast bend to leeward, the shrouds have to be much tighter, beginning with the uppers but also including the mids and lowers to keep the mast in column laterally, when the sails are under load.  And once this is established, then the backstay adjuster will induce mast bend in the forward/aft direction, flattening the luff of the mainsail.

And, to flatten the luff of the sail, the mast should be pre-bent, using the shrouds to induce some forward and aft bend even when the backstay is loose.

Last night I tuned the rig differently than we had done previously this year:

  • very firm uppers, lowers and mids
  • no pre-bend

The results were positive — with the backstay adjuster somewhere near half stroke we could balance the boat well, even though we may have had too much headsail area, and we could remove most of the bubble most of the time using plenty of twist on the mainsail and managing gusts with the traveler.

But I want to build from this to see what happens with some pre-bend, by softening the mid and lower shrouds 5 mm each compared to last night.  I’ve built a new tuning chart that I think should accomplish this.  We’ll start applying it and keeping notes.

Fun!

Banana Split!

Rob DeWitte Leave a comment

Four guys on board on a foggy, chilly, windy night, pulled off a very satisfying 2nd place behind Top Gun. Legacy (a new J35 that sails well) finished ahead of us, but was over the line before the start and didn’t go back to make it right.  Satisfying because we came from behind after a poor start.  Satisfying because we established overlap on Big Yellow at the leeward mark, doused cleanly and kept them in our dirty air in the fetch to the finish line.  Satisfying because it secures us in second place on Thursdays (for now).  Satisfying because we had some things going wrong but recovered quickly and kept on going.  What a great night!

The only blunder we didn’t make right was failing to turn on the camera!

Close your eyes and visualize… (no wait, open them or you won’t be able to read this).  OK, so you’ll just have to imagine lots of water over the rail, Calvin taking a spill as jib sheet wraps around his leg in a tack, Mark falling onto his backside after a tack.  (I guess we were heeling a bit!), Mark facing a completely tangled spinnaker halyard at the tail end of the douse when I needed to jibe the genoa (and Calvin simply unclipping the halyard from the head of the sail and dealing with it on the foredeck) so we could complete our rounding while Big Yellow gave us inches of mark room.

Oh and I split a nail somehow on the mainsheet.

And Lifeline (David) and Lazy Sheet were like octopi managing three jobs between the two of them.  Fantastic!

Here’s how it went:

During the prestart, we had the #2 genoa set and ready.  The wind continued to build, and I was doubting our choice when we saw several of our competitors load up their #3 sails.  Hmmm, looks like we were going to be overpowered.  It was too late to change, so we opted instead to unfurl our genoa only in the final approach to the start.  That was a mistake, because I had expected more of a leap in boat speed.  This meant we were out of position for the start, and ended up smothered in bad air crossing the line at least 20 seconds after the others.   Soon though, we got some clear air and picked up speed.  Time to do something different from the others.

We were the first over on port tack, sailing high and fast in our own clear air.  We buzzed Battlewagon’s stern.  Others boats tacked right away to cover us.  Zig and zag up the course, and we shaved Big Yellow’s stern and made up some ground on Sandpiper.  Still, we were second last around the windward mark.  During our approach, we really had to pinch to make the mark, and gave up quite a bit of time getting around.

But then our hoist was clean and we quickly gained on Sandpiper, who kept their kite below decks in the big wind.  So did Battlewagon.  It was a ‘sheets and guys’ kind of night.

Time for strategy:  The mark was dead downwind (slow).  The wind was stronger toward Hamilton.  Let’s jibe quickly, get over into better air, jibe again and sail a hotter line to the leeward mark.

Good move!  Our jibes were smooth, and after the second one we really heated up the boat speed on a great line to the mark well down yonder.  Big Yellow stayed on the low and slow course and we gained on them steadily.  By holding off our douse for a few more boat lengths we got the inside lane overlapped at the leeward mark, and this was the magic ingredient.  Down came the kite — extremely smoothly for a short-handed crew on a windy night.  Big Yellow gave us mark room, but only inches to spare and there was a moment when we had to jibe, the halyard was jammed and Big Yellow was closing in.  Thanks to Squirrel’s quick thinking, and Lifeline’s quick return to take over the mainsail, we got the barky powered up onto a near fetch to the finish line.

I pinched the whole time to avoid another tack, and to avoid giving Big Yellow a passing lane to windward.  That kept them in our dirty air, so they couldn’t gain.  Their only choice would have been to foot off and tack.  Not a promising option, so they stayed astern.  With a boat length to go to the committee boat, we shot the line to finish just a boat length or two ahead of Big Yellow.  And well ahead of the others!

Bravo Thursday!

Dinghy Time

Rob DeWitte Leave a comment

What a lovely evening!  Warm, sunny, and more wind than forecast.  It was about 8 knots or so, with a few soft patches and it backed nicely right when we needed to jibe  to the leeward mark, so we got to sail high and fast with the kite up. Four of us on board handled the hoist, jibes and douse with no trouble, and we used our new GHYRA-learned algorithm to keep tweaking to get more boat speed.

Our start plan was to go for the pin end of the line on starboard and tack over to port quickly, as we saw ALL the sharks head over that way.  But on our way to the pin end, it became apparent that all the other boats had the same goal in mind, meaning we got smothered by a lot of canvas.  We opted instead to tack over onto port nearer to the boat end of the line and surge into clear air.  Great decision!  By the time we crossed our fleet, we were just behind Top Gun and ahead of everyone else.

WE SHOULD HAVE TACKED THEN TO CONSOLIDATE OUR POSITION AND STAY IN THE SAME AIR AS EVERYONE ELSE.

But we didn’t, and were punished with a light patch that saw two boats overtake us:  Remarkable and Battlewagon.  Drat!  Never mind, Eclipse and Sandpiper were well astern.

Hoist was clean, a quick jibe after it filled and we sailed a hot angle in pursuit of Remarkable.  Battlewagon had some spinnaker troubles after their jibe and we pulled away.  The wind backed, we jibed and had a quick run down to the leeward mark.  Remarkable maintained their lead, so we decided to douse early to make sure it was clean, and the last leg was a simple fetch to the finish line.

THIRD!

And why was this report called “Dinghy Time?”.  With the engine still not starting, we sailed in and out of the marina, just like dinghy’s do.  Piece of cake, thanks to great advice from Nonsuch — we left and returned under genoa alone.  Sweet!

2017 GHYRA Day SIX

Rob DeWitte Leave a comment

A short race today to finish off the series.  Going into this finale, we were tied in first with PerryEh (9 points each) and one point ahead of Tardis.  Battlewagon wasn’t in contention.  The goal was to finish far enough ahead of PerryEh to beat them after PHRF correction.  But we owed them a lot of time — we had our work cut out for us.

There was light wind (almost no wind) when we first got out of the marina, but there was a whisper on the water that was promising.  The race committee set a short course for this “around the bay” race (6S-1-11-9-8F), and as our start approached, the wind built into a lovely 8 knots, steady from the West.  It was building from the Burlington shore line, so our goal was to have room to tack right after the start.

At the start line, our timing was good, but PerryEh offered a dangerous choice.  Could we tuck in between them and the committee boat, or was it a trap?  After a moment of hesitation, we chose the conservative option, and started with them just ahead and to windward of us.  No room to tack!  The other option would have been great unless we were early — would have put us ahead and to windward of PerryEh, but they might have been able to push us over the line or — even worse — force us to do a 360 just to avoid the committee boat.

So, we chose the safe option, but had our work cut out for us.  As soon as we could, we tacked toward Burlington, nipping under PerryEh’s stern.  They tacked to cover.  At the Burlington shore, we tacked back, and just made it over their bow.  Not on the layline yet, so one more push toward the Burlington shore.  Now we had gained nicely on PerryEh, but Battlwagon came up and put a lee bow on us at the layline, slowing us down and we lost a few boat lengths.

Hoist was clean and fast.  Which way to go?  Battlewagon headed deep down to mark 11.  Should we stay on their tail?  Should we jibe over to Burlington?  Decisions.  Indecision!

In the end, we probably fiddled too much.  We sailed a hotter angle, jibed over toward Burlington, jibed again and then hunted Battlwagon to the leeward mark.  Yes we did finally close the gap on them, but meanwhile PerryEh held their ground on us sailing deep to mark #11. Hmmm.  One consolation — by this time, Tardis was well behind.

Around we went.  Good air now.  A quick reach over to the golf course and then a beat to the finish line.  Squirrel read the layline perfectly and we tacked onto it while Battlewagon overstood the mark and got tangled up with Celtic Spirit.  Nonetheless, they still finished 30 seconds ahead of us (this has got to stop!).  Looking around, we couldn’t pick out PerryEh at the finish.  Had we beat them by enough time?

Later at the awards gathering, I chatted with Clarke Perry, and we both thought the other of us had won.  He thought we were far enough ahead.  I wasn’t convinced.  Turns out I was right.  Not only  did PerryEh beat us, they also beat Battlewagon, so we took third.

It was all over in 75 minutes.  I wish we could have gone for another lap, but that was all she wrote.  After the race, we hoisted the spinnaker again and enjoyed sandwiches on board.  Back at the dock, one final apres-sail and then our band of merry men went our separate ways.

What a blast…can’t wait to do it all again next year!

2017 GHYRA Day FIVE

Rob DeWitte Leave a comment

What a wonderful day!  Spinnaker up for 3.5 hours from Port Credit yacht club to the Burlington bridge in a breeze that started off around 6-7 knots and built to 14 or so by the end. Not only did the breeze build, but the swell came on as well.  Right now while typing this, i am still swaying in my chair!

This was our first chance to try a spinnaker start — something I’ve always wanted to do, but of course, had no real concept how to do it.  We watched closely as Adrian Hanley (It’s a Conspiracy) pulled off a perfect spinnaker start in the fleet before us.  Under mainsail alone he maneuvered to a position ten boat lengths to windward of the line.  Then with 30 seconds to go, he bore off and went for the line, only hoisting with ten seconds to go.  Bingo, he accelerated and hit the line just a few seconds after the gun.

OK, I can do that (says me), but one problem…I’m near the boat end of the line and can’t accelerate under mainsail alone.  What to do? Improvise.  We just drifted up parallel to the line.  With twenty seconds to go, we were up near the pin end not far from Adrian’s spot, and we did the same thing he did.  Bingo!

Away we went, with the best start in the fleet, spinnaker full and charging away.  But something was wrong.  Smaller boats were overtaking us with their spinnakers filled.  Aha — the halyard was on the wrong side of the forestay, so our hoist wasn’t complete.  What to do.  Quick decision.  Genoa out.  Douse spinnaker. Calvin rejigs line.  I sail higher, across Battlewagon’s stern to windward of them.  Hoist.  OK, we are only a few boat lengths back, and start gathering speed.

Next mistake:  our fleet sailed out toward the middle of the lake on a high angle in search of better wind.  Rather than following  and looking for an opportunity later (maybe trim better than they do, or something like that), I chose a lower, slower course that was more of a straight shot to the finish line.  I guess, I was thinking that the breeze near the shore would grow first.  But I was putting all my eggs in one basket, and as it turned out, the bet didn’t pay off.  In fact, as our air softened, I had to sail hotter angles to keep up boat speed and after about an hour, it became apparent that we had fallen quite far behind our fleet

It was time for a bold move.  We jibed back toward shore and sailed deep again. Once again we were on the rhumb line, and now the stronger breeze supported a deep point of sail with good boat speed (nearly 7 knots, sometimes more!).  For a while it was looking good, and I learned later that we made the fleet nervous as they saw us picking up speed and sawing off a massive corner in the course.  But when we converged, Battlewagon was ahead, PerryEh crossed at the same time as us and Tardis was just behind.  Correcting for PHRF, it was a fourth place for us.

But what a great day to fly a kite!