Thread: Is that a 12' GIS I see hull down on your horizon

Originally Posted by Boatmik

HI Bruce, your photo of the leeward wind made me laugh. Just how does that person stand up!?

Wonder if they realise that the downforce will increase the hull displacement. The more downforce the deeper she goes.

Also if a sudden gust hits without any speed on, she'll fall over. Not to mention that the foil just below the surface will create a significant wave train.

Let's see what happens when it is more than a sketch on a computer with a person standing at a funny angle!

I think the argument against the leeward wing is similar to the one I made here.
Boat designs influenced by rules? Why Victorian Plank on Edge Cutters show canting keel maxi yachts are stupid and multihulls, smart

Multihulls can get the weight for stability near to a boat length to windwardeffectively more than half the beam if you are not so expert at flying hulls. And it is a stable configuration at any speed.

MIK

Hi MIK

I have seen these leeward wing foils appear on various boats for testing, including dinghies. No doubt the testing brings conclusive results in line with your thoughts, so that is why we don't yet see them as serious fixtures.

Multihulls... Agree that they make sense. Just that they make for very ordinary sailing. Pure straight line speed, and hitting the corners upwind is just a yawn for the skipper and spectator. For proof, just watch the Extreme sailing series or the AC 45s. Tactics and advanced manoeuvres are just non existent. Advanced sailing tactics and boat handling are just not possible with multihulls.

Originally Posted by woodeneye

Tactics and advanced manoeuvres are just non existent. Advanced sailing tactics and boat handling are just not possible with multihulls.

Interesting perspective. It raises the question, which comes first: the technology or the tactics? (There's no right answer of course, other than, "it depends.")

This reminds me of my former work with small caliber weapons (ah... those were the days...) The skills and tactics required for bolt action rifles (or--dare I say--flintlock muzzle loaders?) are not required/non-existent when employing today's gas-driven semi-auto/automatic assault rifles. But one would have a hard time defending the use of muzzle-loaders simply because assault rifles are too easy to use and don't require shoulder-to-shoulder formations.

However, one has to draw the line somewhere to decide what is the purpose of the sport. If it is simply covering distance over water by the fastest means possible, sailing is no longer the technology of choice I suppose.

Dave

I'm not really concerned with the technology aspect. There is no doubt that the multi has the speed edge and the boats that hold all the speed records are multis. Just that the skill sets required to sail a multihull at the highest levels of competition are lower than the skill sets required to sail a mono at the highest levels.

This doesn't mean that top level multihull teams in competitions like the Americas Cup and Extreme 40's won't still seek out the top sailors to crew their boats. The sailors they seek out are all successful monohull skippers, simply because they have far better skills, and are better sailors. Go through the crews on the top boats and you'll find that this is the case, 99% of the time.

A quick scenario by way of example. You are sailing upwind, and the gust you are in dies. You are headed 2 degrees. If you are skippering a monohull dinghy, you need to know if the header was a velocity shift or a genuine header. What you do next is crucial. If you tack on a velocity header you lose 3 boatlengths on your rival who does not tack. If it is a genuine windshift, you must tack, because if you don't you lose 2 boatlengths on your opposition if they tack. What do you do if you are skippering a cat? Well, simply you don't care about a 2 degree shift, it's simply nowhere near enough of a shift to gain from tacking, because it takes you 20-30 seconds to tack and regain full speed on the new tack. Either way you lose 50m in distance, therefore you don't need to know how to recognise the difference between a windshift and a velocity header. You just have to keep going at full speed on a lousy tack.

The statement "Multihull sailing is mostly about who has the faster boat, not who has the better crew" is roughly 90% true.

Edit:
PS. I realised that some readers may not know what a "velocity header" is. Simply it is a change in the apparent wind direction as your boat slows as a result of the gust you are in dying. As you slow down, your apparent wind moves forward, so you are "headed".

The opposite of a velocity header is a velocity lift. When a gust hits, your boat speed increases and your apparent wind moves aft, ie. you are lifted. Velocity headers and velocity lifts are called velocity shifts. A velocity shift occurs because of an apparent wind shift, but in reality the wind hasn't changed direction at all.

Originally Posted by woodeneye

Hi MIK

Advanced sailing tactics and boat handling are just not possible with multihulls.

I would certainly agree with that. But the closer you make monos to multi performance you start to have the same problem with big speed losses when you tack or gybe. Canting keels, banana boards, water ballast or 18ft skiff trapezing racks all impede tacking and increase straightline speed. Not to mention Moth Hydrofoils, though they are getting pretty good at carving turns without dropping down off the foils.

[ame=http://www.youtube.com/watch?v=3BZwM2LDCb4]Rohan's Foiling Tacks, Lake Garda, June 2007 - YouTube[/ame]

Modern tris and cats do tack a lot better than a couple of decades ago but you just have to be on a bigger racecourse.

The first thing I ever read about big multis offshore ... or written in a gut wrenching style was by then Olympic sailor Cam Lewis who sailed with one of the Peyrons on a big multi in a channel race ... we went round the top buoy off leHavre and set off in a cloud of spray at 32 knots toward Spain ... we couldn't see forwards so we steered looking backwards at the wake.

Biting Midge who bought the first GIS plans used to be the Queensland multihull offshore champion. I did a sail with him on a 24 foot tri on Moreton bay. Quite a big course ... and the boats covered it well and because of the long distances the tactics came into it again. Even if I couldn't grasp being so far from the startline with 15 secs to go .. we screamed down on a beam reach whipped around the committee boat and headed off upwind hitting 12s occasionally. Some miles away was the top mark. When we got round that we were off at 20s to 25s. I started to understand the place of multihulls for some sorts of cruising. You can get across the Gulf of st vincent in a couple of hours instead of 5 or 6 when you might get exposed to big weather changes.

I'd say Bruce, if you ever get the chance to do a coastal race in a multi, snap it up. There is really interesting potential for small boat type strategy and tactics because of the bigger distances.

MIK

Multis do offer excellent an excellent solution for cruising. As you say, they are fast, but they can also traverse very shallow water. Moreton Bay is a good example. There are lots of multis there because the Bay is so shallow, too shallow for most racing keelboats which have deep keels. Multis are also very smooth and comfortable by comparison, so below decks they can be much more pleasant than a mono which is heeled over at a crazy angle. The new cruising cat designs are simply fabulous. I recently saw one under construction in South Africa and was surprised by the headroom and space available.
Back to the Moth video. The Moth is definitely on my bucket list and I’d like to have one, one day. What an awesome toy to have! MIK, you will remember well watching the Moth Worlds on Belmont Bay early last year. There were not very many who could tack as fast as Beale does in that previous video and 90% of the fleet would drop the hull and stop while executing their tacks. Gybing was a different story with most skippers able to keep the hull flying through their gybes. I keep half an eye open for second hand Moths, which sometimes go for quite little money. Being mostly carbon, they are so easy and cheap to fix up if you have the basic layup skills.

Hmmm .. when you get one ... give me a couple of months to get fitter and I would love to spend some time on a warm summer arvo with an onshore wind!!!

MIK

Any progress being made?

Well .. I am a bit more settled in Malaysia after a couple of crazy weeks in Manila.

Weather is cooler. I have been thinking more.

Have a website problem I have to resolve first though ... no thumbnails on main pages.

MIK

I'm happy to announce progress.

Basically I have a set of preliminary plans and have sent them off to Rick Landreville in Canada who is building the prototype.

After some building problems are checked ... particularly the true shape of a rather strangely shaped forward bulkhead ... the plans will be released.

It's not the Son of Goat.

The Son of Goat was to have the GIS heritage. Sail well with our without extra body/s, rowable and some motorable with a traditionalish rig.

This one is much simpler. It won't row or power and will carry extra weight but there is no real margin for it in the displacement.

This one is really optimised for a singlehanded adult. And supposed to sail efficiently around a race course or for fun day sailing - no trouble getting upwind in any normal conditions. I'm wondering how much cheaper than a Laser it will be.



It is intended to fit in some of the space the Laser fitted into when it was introduced. Almost like a fun boat you could stick on your roof and go sailing in without need for too much help. Enough space for sandwiches and an extra crewperson (but don't assume the same speed as one up).

The fat head sail is to keep the mast short. The mast is not sorted yet but the bulkhead each side of the mast location will suit deck stepped sticks with rigging or freestanding ones.

Sail area is modest. A little bit smaller than the laser, but it is a bit higher up and the boat is only 12ft opposed to the Laser's almost 14.

Hoping there will be a substantial weight advantage over the Laser too. I'll be happy with a genuine 120 lbs hull but it might be somewhat lighter. 2 sheets 6mm, four sheets 4mm gaboon.

That is 28/36ths of the plywood weight of the goat. (adding up the total ply thickness of a stack ... so a very rough calc shows a total of 100 to 116lbs cf the Goat).

It's kindof self jigging with the cockpit faces near parallel to the centreline allowing that area to be set up easily ... hull sides added with a few cable ties then bottom taped on Quick Canoe style. Then inside glass taped or filleted - remove tape and then glass tape outside.

So actual plans are a month or so away. Rick starts building next week all being well.

MIK

Well, this is great. It definitely has that unmistakable Storer look too. You know, the kind of look that says this is a little weird, but hey, doesn't it look quick?!

I think I would build this boat, but maybe would use my Laser rig to save costs. Mast may need to be repositioned, but that looks like no problem. Then again, this sail shape looks very cool and makes it look so modern and appealing.

Yay, it has lost the rear tank!

Way cool!!!

Knowing that Rick is a very fast builder, I am confident that test sails will happen soon.

This looks very promising! I like the fathead sail with its modern look: a good match for the boat. It will indeed also keep the spars short which is good.

Can't wait to see the prototype on the water and reading the reports on how she performs.

Joost

Rick's going to need a low cost trial sail pretty soon so if it helps I have drawn up a sail in SailCut4. By using a 4 panel horizontal cut layout the 3 panel seams can be overlapped at 50mm giving enough room to use the overlap as batten pockets.

just a first trial layout to show what can be done very easily using SailCut4.

I have uploaded the files to Google Docs .

Overall sail drawing. Cannot quite do the leech shape but close.

https://docs.google.com/file/d/0B4Bi...g4MGNPVzQ/edit

Panel development drawings

https://docs.google.com/file/d/0B4Bi...tzVGcyeTg/edit

Screen dump showing the sail shape looking from the rear of the sail. The program allows for head twist which can just be seen.

https://docs.google.com/file/d/0B4Bi...hXa0JlZlE/edit

Boat looks like a lot of fun, especially for teenagers . I make the mast about 5.20m. Some windsurfing mast come that length. Two piece mast be be very useful. Very cheap and excellent two piece mast could be done with a lower larger section and and an upper smaller section which just slides inside lower section. Available everywhere, very low cost, very light and very quick. Same for the boom.

Brian

Gosh you are fluent with that now Brian!

I have a sail with no broadseaming drawn up from the luff offsets I have used for other boats.

I'm thinking of just giving it to a sailmaker to make as is.

MIK

I guess if you are using a sailmaker, then he will be able to make you a lovely sail, which is important to properly evaluate the hull performance. Should think he will combine luff round and broadseaming to make a powerful stable upwind sail.

When sails were made for the OK dinghy I had 35 years ago, each sail was made to order by putting a weight on the mast end and measuring deflection, plus the helmsman's weight. So your sailmaker will need mast deflection numbers?

If she uses the PDR foils, is the PDR mast long enough. Guess it's easy enough to make the length 17' for the new boat. Forgetting the original PDR sail was set on the mast and not a lug, so you know the luffl round suits the mast bend. Sorted!

I have a canoe sail designed that combines luff round and broadseaming. This uses 80mm luff round at 30% up the mast. So, perhaps design something later on for home sailmakers.

Here's the standard canoe sail

https://docs.google.com/file/d/0B4Bi...NFdmMxR3M/edit

and my favourite, laid back 5.0m canoe sail designed for my 4.65m carbon windsurfing mast.

https://docs.google.com/file/d/0B4Bi...Zza1hvQmM/edit

Brian