Tacking Downwind (faster than the wind)

CT 249
Yes, prompted by your reply, I went back through a few records etc. Close to 50 on a sailboard hasn't been achieved in 20 knot breeze, although speeds in the late 30s have, in breezes of around 20 it seems. I thought that the Irish guy who held the record for quite some time had achieved it in lighter conditions but, as you say, he needed a gale! Thanks for pointing this out! Dammit, everyone will doubt my Folkboat claim now!

 

I'm not wrong at all, just realistic and objective.

Winning an odd race or two without regular repeated results in all conditions is not truly representative of a boat's performance. It is certainly possible for a Mirror Dinghy to "beat" (your tired and often used word) a Moth Hydrofoil around the track if the Moth spends lots of time upside down. That does NOT make the Mirror a faster boat! Your performance claims are based on the odd performance, not over a long time period with consistent, repeated, audited results. A useful measure of performance is the Royal Yachting Association's Portsmouth ratings based on long term race results from recorded and sanctioned events. You also use Rohan Veal as your example helm - he's a world champion, the most experienced foiler in the world, and not representative of foiling helm's ability in general. It's like using Tiger Woods as the basis for setting par on all golf courses - ridiculous.

Moths can "take off" in under ten knots, but full upwind foiling, foiling gybes and tacks and serious foiling performance is not consistent until the wind is ten knots and above. Sub ten knot foiling is far easier for people that are on the lightweight side - heavier folks foil later.

Unless the helm is seriously talented and on the heavy side, foiling in over 18-20 knots isn't child's play.

Foiling DOES have an optimal range in which it performs spectacularly. Outside of that optimal range, other platforms perform better. I'd personally rather deal with light wind on a typical dinghy, roll tacking and roll gybing than be stuck on a one foot wide Moth with huge unusable foils dragging under water for 60% of the race days (damned light wind) in my North American venue.

I think foiling is unbelievably cool, but I also think it isn't for everyone and every venue. I'm perfectly willing to concede that in the absolute right conditions, with Rohan Veal helming
a Moth foiler can be competitive with an AVERAGE helm in an 18' skiff. That does not make the Moth superior in six knots of wind, nor does it make it better in 25 knots of wind.

Anyone objective and fair that has actual sailing experience in high performance boats can reach these objective conclusions quickly. I'm willing to stand up and have my opinions judged by everyone here - are you?

 

I wouldn't call it "objective" when you deliberately misrepresent the performance window of the foiler Moth. The performances I quoted are not "odd" but are representative of the performance of the boat in many different places,times and wind conditions. The fact that the Moth takes off
in 6-7 knots of wind is not incidental but phenomenal. The fact is that the boat sails at MULTIPLES of wind speed in those under 10 knot conditions.
Why do you feel the need to talk the boat down?

 

I just noticed where you live - I pass through your area a few times a year - my parents live on Lake Huron near Tobermory, and I pass by to the north travelling between Stayner and Orillia on my trip from Ottawa a few times a year. One of the most respected naval architects in the world lives right around you - Steve Killing.

If I lived where you do, I'd probably make an effort to find Steve Killing's place and show up with a couple Tim's - and see what he thinks. He was the designer behind Fred Eaton's (yes, that Eaton family) foiling C-Class catamaran. There is no one better to talk to about this stuff than he. If I recall correctly he lives within 30 minutes of you.

Skiffs and foilers can beat the stuffing out of you - crashes are violent and can cause lots of bruises and bleeding. I'm closer to fifty than I want to admit, and I think I'll be keeping to less stressful rides once I get to your age! Stuffing your bow under water at near 20 knots (called "going down the mine" in skiff terms) and the subsequent trapeze ride and cartwheel is never fun.

Playing with foils is a balancing games - balancing drag against performance, and balancing wetted surface area against net benefit of the lift achieved. For your kayak design, I'd guess that keeping things simple is probably going to net out the best overall results.

Best of luck!

--
Bill

 

Hot ziggity! We have a conflict going between Doug and Bistros. That is entertaining as long as it does not become abusive. Let us not demean ourselves gentlemen.

Now back to the sailing kayak. The answer to the original question (down wind sailing) is resolved. Let me add that tacking down wind is a useful tactic for experienced sailors in fast boats. Kayaks are not fast boats in the general scheme of things. Yes I am a kayaker, yes the Baidarka was/is a fast kayak but only when compared to other yaks and only when propelled by super strong Aleuts. Back to the sailing thing. Tacking downwind involves the jibe maneuver. That is a pretty chancy in a skinny boat like a yak. It's a bit delicate on an International Canoe as well. The IC is skinny but much wider than a kayak and way faster too.

I suggest that you should be less concerned about ultimate downwind speed and concentrate more on the sheer pleasure of sailing sensibly on a sweet little boat. If you must go really fast on a narrow boat, then investigate the IC.

 

No conflict here at all. I go out of my way to avoid Mr. Lord, and only infrequently chime in when folks who may not know better are possibly being led down the garden path. No responsible adult would persuade a gentleman of this poster's experienced years into foiling. An IC is out of the question as well.

I've played with leeboards & sails on canoes during my youth (could not afford a real boat), and found chicken gybing (tacking around) works okay as long as you've got lots of (and then some!) room. Real speed is not an option during maneuvers, as there just isn't enough righting moment and ability to respond & move around fast enough in a kayak.

I'm willing to bet the good "ancient kayaker" is going to be able to get great speed out of his rig, although he should pay attention to developing some great basic "fail safe" maneuvers like chicken gybes, backing up to recover from being in irons and how to dump power from his rig via sail controls like a cunningham and mast rake. Although sea kayaks are pretty directionally stable, you can greatly increase turning speed by controlled heel. The lee/daggerboard creates a good pivot point, and using the lee helm (windward heel) and weather helm (heeling to leeward) makes the boat turn much faster.

--
Bill

 

Bistro: we all enjoy the conversations that occasionally strike up between Doug and youself or anyone else within reach, but maybe it's just as well you're at opposite ends of the continent! You're great blokes and a mine of info. Passion's a good thing so long as nobody gets hurt.

Steve Killing lives in Midland, about 45 minutes from me, and I am visiting that town next month so I will try to look him up for a visit. Great idea, thanks for the heads up.

Despite the temptations from the voices in the wind (or in my head) the main objective for me at my time of life is the serenity of a quiet, peaceful sail in idyllic surroundings, enjoying my dotage. One or two people have been concerned with my welfare and have been so kind as to suggest caution, and I appreciate that. I am alert to the potential of contact sailing; I don't fancy "going down the mine" although it's a colorful expression. I've been down a few real mines in my time but they were not usually quite that wet!


Nonetheless, if I can sail quietly and restfully along at terrifying speed with white water up around my ears that would be a bonus. The last kayak sailing kit I fooled around with was surprisingly brisk at times, but the whitewater only got up to my elbows, and never while sailing upwind, so there's room for improving the experience. Besides, I like to piss off the fuddy duddies in the marina.


For the kayaking project my motto is, a little bit at a time. The initial idea was a lifting lateen sail with a pair Bruce foils, something I did a few years back with a single foil. I have had a lot of help with the foil profiles. Doug contributed the idea that the foils can rotate for steering, with a simple fixed stern skeg so the hull can sort of be towed along, a kind of tractor-trailer arrangement. If I mount the mast/sail on the rotating foil assembly they can both rotate at the same time then I can change tack quickly without having to wait for the hull to come around.

That should take care of the quiet idyllic part, now for the speed. Listening to the voices again, I can maybe try a wingsail. At that point, it may feel like it wants to fly, as the foils are asymmetrical and will certainly generate lift, although I will be surprised if it's enough to "foil" the downward tendency of my my 80kg of avoirdupois. There'll have to be some serious re-building to add the necessary strength and support to the foils and a stern foil, possibly adjustable. A custom built hull may be indicated. I will have to add a helmet, elbow and shin pads and cockpit padding to my to-do list. Better update my will as well.

 

Well if foiling is in the works I would recommend looking at buying a used Moth. I have seen them for sail for about 4K rigged and ready to go, but no longer competative for racing. This may break with your desire to build it yourself, but these things are very much engineering marvels, and recreating the wheel may be more complicated than buying a working boat and copying the things you like.

If you are not worried about race ready gear the prices on these development class boats comes down radically as the fastest design gets discarded by the racers and they are just looking to get something back for their new lighter carbon boat.

 

Nah. More fun to do it meself. Besides, I likes wood.

Bistro: I didn't address the last half of your post. Gybes weren't a problem on my last rig due to sail design, but when there was room I preferred to wear ship instead of tacking as I got a lot of practice backing - damn thing seemd to go faster in reverse. Ah, the 3 point turn. I will have a loose footed sail with hand-held clew so I can just let go to turn off the power. I wasn't planning on using the sea kayak for this rig, I have a much shorter kayak that is very stable.

 

AK
You might be interested to pick up a thread on the WoodenBoat forum about `Building Beth'. Beth is basically a sailing canoe/kayak style of boat designed by an Australian. The thread has a number of interesting conversations about the advantages and potential disadvantages of these craft. The designer, Michael Storer, is very knowledgeable, helpful and informative and, I'm sure, would be interested in your project. He goes under the name MIK in the WB forum.

 

Couldn't find the thread, and I had trouble with those imaged passwords. I'm colorblind and they're like the cards the optometrists use! Too much security.

However I found several sites on the Beth design. I have plans for a 14ft John Bull sailing canoe (Nautius) which has a similar rig, stitch and glue construction, and a friend of mine has been building a sailing canoe for years, don't know if he'll ever finish! I know these boats have an impressive performance.

Currently I'm following up on some development I did a few years ago and I want to pursue it as far as it wants to go. The sailing rig can be built by anyone with half a brain and should fit on most kayaks and canoes. It leaves their paddling performance uneffected.

After that I want to undertake an update of my own design of Rushton's Wee Lassie. Then maybe I will put a sailing canoe together. I'm running out of space for all the boats however.

 

Just back after a few days absence.

Sorry AK...I was being facetious. A bad sense of humour set off by dealing with a few jerks that day and being tired of the "the old way is always the better way" mentality. Your question was exceedingly clear...and a good one.
Sometimes, even I don't get my humour.

 

Tacking downwind: Yes! Faster than the wind: Depends and possible!

It is well known that tacking downwind for max VMG is desired.

Whether it is possible to go faster than the wind depends on
1. Boat type
2. Wind speed
3. Wind direction (and what you still consider "downwind")

Look at the polar diagrams at the top of

http://yoavraz.googlepages.com/sailingboatspeedvs.windspeed

taken from the book The Symmetry of Sailing:

At 10 knots wind a tornado catamaran goes faster than the wind up to wind at 135 degrees; 18ft Skiff up to 145 degrees. Both are beyond the VMG anyhow.

The polar diagrams of a given boat (or my formulas at the WEB link above) give you the answers to these questions.

 

With respect, those polars look a bit odd. There is no way a Tornado is only about 2/3 as fast as an 18 upwind; even a "Classic" Tornado is extremely quick upwind against an 18.

The argument on comparative Tornado v Skiff performance rages even here in Sydney, which has a reasonable standard of Tornado sailing and the world's largest Skiff fleet. The two classes almost never meet head to head; last time I think the top 18s met good Ts in a race was about 1988!

The yardsticks of the classes in the UK and Australia do NOT indicate that the 18 is as fast as your polars indicate; off the top of my head they indicate that the T is faster.

At the next level down, an F16 type cat is much faster upwind in 10 knots than one of the top 16 Foot Skiffs, and significantly slower downwind when the cat hasn't got the kite up.

Tacking downwind certainly isn't always desired; it doesn't work in slower boats a lot of the time.

 

Reply to CT 249

The polars are from a 96 book. I do not have personal experience with these classes, and I cannot comment on the polars' accuracy (and the resulting approximated eta's calculated from them).

However, from your last sentence I see that we agree on the answers to the questions above. The specific polars are only used to demonstrate the point, and how to find the answers for any specific boat.