Thread: solving a mystery

The word "vang" is not actually the correct one, in the context of what is needed.

A vang is adjustable, needs blocks and cleats and pulls downwards on something.

What is need is just a preventer. That is something that just stops the boom lifting. Not actually pulling down in a vang way, but just stooping the boom lifting and the sail twisting.

A simple line fixed to the boom, say about 2' back from the mast position, taken down to the mast at deck level. No adjustment needed once set.

On the wind, the mainsheet pulls down more than the vang anyway. It always goes loose upwind.

So, raise the sail, and just clip the preventer on an eye at the mast/deck.

This will do everything that's needed for a lug and cost pence.

Brian

Originally Posted by b.o.a.t.

Watching vids of Lasers gybing, they seem to make a radical turn towards the sail to start the gybe,
then an equally radical one the other way as the sail swings across. Little or no apparent effort made
to soften the gybing boom. I'm guessing that this is, as MIK? commented earlier, to steer the boat under
the mast & stay upright.
Maybe GIS & Raid both need to be handled in this way ?

just thinking out loud....
AJ

That's spot on. There is another reason for this technique, which is due to no central sheeting to grab to facilitate the gybe. (The sheeting arrangement is the same on a GIS, but RAID41 has a central sheet). Bearing away or "turning toward the sail" as you put it slows you down a lot, so that the boom comes across very hard and you have to bear away hard on the other tack to compensate. Another possible reason that Laser sailors don't worry too much about the sail coming across hard is because the sails are quite small. I've been sailing a Laser a bit lately, and it's a bit of a toy really after sailing the Goat.

Not being able to grab a bunch of central sheeting makes it very easy to "miss the moment" and a less than perfect gybe results. Grabbing a handful of central sheeting while going nice and fast is much quicker, especially when you have boats all around you as well. I've been thinking about central sheeting for the Goat for a while, together with a traveler along the rear edge of the seat. Last year MIK suggested I try this when were discussing this very subject on another thread. Gybing will be made easier and there is no mainsheet hanging under the boom to get hooked up on either. I'll have to give it a try very soon, as the end of the season is approaching with some rapidity!

Originally Posted by keyhavenpotter

The word "vang" is not actually the correct one, in the context of what is needed.

A vang is adjustable, needs blocks and cleats and pulls downwards on something.

What is need is just a preventer. That is something that just stops the boom lifting. Not actually pulling down in a vang way, but just stooping the boom lifting and the sail twisting.

A simple line fixed to the boom, say about 2' back from the mast position, taken down to the mast at deck level. No adjustment needed once set.

On the wind, the mainsheet pulls down more than the vang anyway. It always goes loose upwind.

So, raise the sail, and just clip the preventer on an eye at the mast/deck.

This will do everything that's needed for a lug and cost pence.

Brian

I have to disagree with you on this Brian. If anything, a vang (kicker) is even more important on the 4-sided lugsail in order to control twist. My reason is illustrated in the pic below. Here, Mik was maneuvering for the camera, so the vang wasn't on nearly as hard as it would normally be, as it was set up for beating (the boom pulled back). Look at how much of the sail is ahead of the mast compared to the position of the boom, and he wasn't even running square yet.
Attachment 164912

I normally control this by sliding the boom forward a quite a lot and applying enough vang when running and broad reaching.

Might be a terminology mis-match thing happening here.

In Oz, anything holding the boom from lifting is a vang. Or kicker.

A preventer in Oz-speak is a Big Boat thing of which I have no experience, but
I think it leads forward from a boom to stop it gybing when you don't want to.

Agree that the balanced lug isn't totally self-vanging, however it is so to some
degree compared with a gaff or bermudan. Logically, it becomes more
so, as more sail is allowed forward of the mast and luff & leech tensions are
equalised. A square sail is the extreme example.

I disagree that there was significant boom lift in John's video. I think it is
parallax 'error' / perspective in the fairly wide-angle picture. Had the boom
lifted, and air spilled leewards from the sail top, the capsize would have been
to starboard, not port.

So, other than accentuated impact of air-flow across the sail, perhaps there
is little commonality between John's GIS capsize, & Brian's Raid capsize.

Oh, and the incredibly clean wake of both. (see https://www.woodworkforums.com/f169/g...ml#post1225336)

Actually, in that clip of Bryan (USA) zipping along, it is easy to imagine water
banking up against the bow, causing tripping.

cheers
AJ

Originally Posted by woodeneye

I have to disagree with you on this Brian.

I also agree with you!!!

I would not be without an adjustable vang. No way.

It's just that MIk is so against them that I thought by suggesting a simple preventer at least the boom would be stopped from lifting.

Brian

Originally Posted by b.o.a.t.

A preventer in Oz-speak is a Big Boat thing of which I have no experience, AJ

I raced on an OOD34 for many years in the 80's.

In strong winds, when sailing hard pressed downwind with a huge masthead kite up, we would always rig a preventer to the boom. This was fixed from the alloy toerail up to the boom vertically. Remember the boom already had a powerfull sheet winched vang. The lifting forces are so great, and all control would be lost if not used.

On the smaller Dehler Sprinta Sport in recent years, we would barber haul the sheet and guy much further forward to pin down the spinnaker when racing in strong winds. The Sprinta is such a great boat in those conditions, we would often be the only boat with it's spinnaker up in heavy air.

After such experiences, not using any sort of vang just seems unbelievable.

Brian

Originally Posted by b.o.a.t.

so, returning to page 1 of this thread (which has wandered OT just a little...)

As I understand it, the thinking is that R41 capsize was likely a combination of
slab side of the fine bow 'tripping' on the water, multiplied by narrow bottom
plus high crew weight, happening well forward of a really grippy centreboard.
And probably some other factors like rudder lift opposing the broach vector,
but actually assisting the capsize vector.

I am always surprised by the knowledge that everyone brings to bear in this forum. So many good sailors and nice minds! This is a great posting AJ - nice to have a really different perspective

Theory is then, using OH&S principles, eliminating one or more of the
contributors is likely to reduce/eliminate the problem. Can't do much about
the high crew weight due to needing dry sleeping space, so...

I think you have described the cascades of the design decisions really nicely here. The way the RAID ended up was because of the original design decisions - dry sleeping space, rowing geometry (in a better than minimal way), self draining from capsize or any slopped aboard water.

I think on paper the boat is a really nice solution to a lot of those problems, but the biggest weakness for me was the way they conspired to make the build very complicated. That thinking was positive because it led to the duct taping of the Quick Canoe as a way all the filleting could be done in one hit and that no internal timber need to be cut and shaped.

Once launched some weaknesses appeared quite quickly. The problem with the analysis is that we don't really know which of them combine (I was going to write "conspire") to give the type of result we are talking about.

Also some of the possible causes might have been eliminated by careful experimentation - something that neither I or the two prototype builders really had the heart for at the time. We were all pretty miserable.

One example is either the grippiness or non grip from the centreboard - that can be adjusted pretty easily. Or the light weight hull's stability being overcome by the crew weight being so high - that could have been adjusted with smaller water ballast in Bryan's American boat.

So i think the analysis of factors is a flawed process because we don't know enough to decide which ones are really responsible.

As the drawing I put up a few weeks ago shows - the RAID hullshape is not really substantively different from the Goat and apart from the stern, not too different from BETH.

Possibilities...
1. A Rainbow scow style pram bow changes the bow dynamics - brings the
tripping hazard aft to where it is negated by the centreboard, but keeps the
simplicity of concept. Also increases stability forward. Penalty is a shorter
waterline length, and a noisier, wetter ride in slop. Also noisier to sleep in but
hey, if it doesn't fall over... Sleep-time noise-cancelling by warping a sheet of
foam or carpet under the bow ?

This is a nice one for something I have wanted to mention for a long time. The Bolger Propensity for having the bow out of the water (something modern offshore raceboats followed some decades later) means the sharpie starts to approximate the nice straight lines of a scow. This probably means less drag and less tendency for the water to push the boat around making it hard to control. A close relative of this is having the hullshape reasonably symmetrical in terms of volume. Despite the Goat being sailed by a lot of different people in a wide range of conditions - it is very unusual amongst small boats that it goes where it is steered - it doesn't decide where to go and leave the skipper struggling to push it back on course.

2. A fuller bow to float better, resisting diving, & hopefully less prone to tripping?

My understanding of this is completely different. It was demonstrated by the problems that the Australian scow Moths had with nosediving downwind. They tried all sorts of things with the bows of the boats and found the solution in reducing the width of the sterns. This was emphasised by my sailing of BETH - which can scream along at a really high pace on a broad reach, but where a little bit of oversheeting on the mizzen can stall the tiny rudder.

The little rudder was a risk in the design - but it is interesting what happens when it stalls - usually instant death in a conventional racing dinghy at those speeds - the canoe shaped hull just continues straight because heeling doesn't really affect the direction the hull wants to go.

I took a lot of trouble with the Goat to try and get this affect too - something that seems to have worked very well in practice.

The R41 was, in my mind, much more conservative than the Goat - adding some features to help keep the bow out of the water as the boat goes faster (it is done with the stern) and also to help stability a bit more when the crew goes forward and to make sure the bow doesn't drop in as the boat heels.

We ended up with something unexpected though!

3. A wider bottom increases static stability, and creates a fuller bow which-may- float rather than dig-in. BUT loses the ease of on-land handling. And
does nothing to assist re-boarding, which IIRC is why the project was canned.

That was done - fuller compared to the Goat - and the Goat doesn't display any similar characteristics.

4. A 45degree chine panel tapering from 0" near midships up to maybe 3-6" high at the bow complicates the build, but would make it vastly less likely to
dig-in. Would need to make the bow above it fuller, and reduce rocker below
it to compensate for loss of volume. Both of these might be good things?

Vastly complicates the build as the panel has to be highly twisted as per most bilge panels and lose the simplicity of the chine.

5. Bring the main mast aft a foot or two & aim for a more "balanced" balanced lug to reduce broaching thrust vectors ?

Again a really interesting one because of what it suggests. I am wondering if the cat rig of the Goat might be providing some nice effects to keep the boat on line on different points of sail.

The Goat is very nicely balanced - but with the cat rig the sail all moves to the front of the boat - well in front of the centreboard when the boat is broad reaching or running - so so it tends to keep the boat on line.

With the ketch/yawl rig of BETH (I think most of you know my reasons for combining those terms) the rudder can be stalled by oversheeting the mizzen, but nothing much happens because of the symmetrical hullshape. it is just the tiny rudder cannot sustain much side load - but it doesn't matter as the hull won't do anything strange.

6. A bigger rudder might resist a tripping bow better, but would also 'lift' the bottom in the direction of capsize... possibly the two cancel out completely
yielding no benefit. so...

That's been one possibility - relating to the BETH rudder stalling - I suppose it would be interesting to get a RAID out in high winds and see if the rudder stalls and if reefing the mizzen reduces the tendency.

7. taking a leaf out of Bolger's "Dart" and "Cartopper" desgns - move the CB
forward & reduce its size, compensating for reduced 'lift' with a larger rudder.
see attachments below.
Result as noted by Bolger in the case of Dart, is a very unconventionally handling vessel.
May not work without also applying one or more of opts 1, 2, 4 or 5,

I have sailed the Cartopper several times and it is a real cow. It doesn't have anything like the instant responsiveness that good sailors expect. It stalls halfway through tacks and ends up sitting stably head to wind. I once bought a second hand moth with a tax refund and found I similarly couldn't tack it without hanging up. The problem was the centreboard swung too far forward. Making sure that didn't happen made it into a really nice sailing boat.

That crisp instant response to control inputs is something I think is essential to my style of boat. In some ways I am not a great experimenter like Bolger. I am pretty conservative and tend to choose things that I know work well on the racecourse. I like to try to combine them with some of the things that make traditional boats and rigs so nice as well. Those two worlds are not quite as far away from each other as many people think - for example the stern volume problem leading to tricky handling being impossible in trad boats and solved in racing Moth scows because of the same methods.

Which my gut feel are the best options anyway.

Does any of this make sense regarding the actual capsize Brian?

Do any of these (or combinations thereof) make sense to you Michael ?
What would least harm the performance?
You are the one who knows the numbers.
I'm just feeling the 'vibe' of the thing... Mabo & The Castle & all that.

Still got to figure out the re-boarding.

cheers
AJ

Like I said - a great contribution AJ!

MIK

Mr. Goodman's capsize was not the result of twist at the top of his sail. He is on starboard tack and capsized to port.

The wind blew him over as would be expected. If the absence of a vang caused what I call a "reverse airfoil" at the top of the mast his capsize would have been to the unexpected side--starboard.

I won't argue the pluses and minuses of a vang but, having experienced a death roll in a Force 5 many years ago I can recognize one (or not, in this instance) when I see one.

Howdy

It is absolutely rubbish that the lug is self vanging. The boom will always just pivot about the downhaul attachment point. the further back along the boom the moor it will act as a vang. But it is not and never can be a vang.

Not absolute rubbish - it depends on what you are comparing to.

(added much later on a pic of a Goat Island Skiff running in light/moderate wind with vanging effect quite obvious)



If you compare to a traditional gaff rig or standing lug the balance lug looks really good in comparison.

But if you compare to something with a purpose made vang then the balance lug really doesn't look that good - but it is way better than the alternatives/comparatives. A single line control that controls the twist to a reasonable extent.

In practice the gybing of a balance lug is very mild indeed compared to something with no vanging effect.

The overall winner for vanging effect is the sprit boom rig - which prevents twist in a way that is exactly comparable with the detwisted conventional vanged rigs above. But difficulties of reefing start to be important with boats meant for a wide range of use rather than racecourses.

It's just that MIk is so against them that I thought by suggesting a simple preventer at least the boom would be stopped from lifting.

Not true! I make the assumption that most people who want to build my boats will know very little about sailing or boat building. So the single, simple downhaul is the most rational approach for a boat that can sail very well and handle very well.

Most of the people discussing here are good enough sailors and smart enough to work out their own methods - and I accept that they will.

But the standard will always be the single downhaul - part because it is so simple and works OK, but also because a downhaul plus a vang requires knowledgeable setup and adjustment. You can do it Brian, as can most people discussing here - but you have to think of those without your background.

The sailing experience is that the single line works well enough if it is adjusted properly - in terms of real boats in real handling in real winds. That's always the guide.

If you look at the information included on the WIKI it is very difficult to support the argument that I am "so against" a vang. I just don't want it to become the standard method.

Best wishes
MIK

(Brian - sometimes posts on a forum seem more harsh than they are meant - so I want to add this note that I am not angry - just making the points clearly - always look forward to your contributions here - and I have learned a lot. Also you comments above are positive in that they allow me to show my perspective on the question. Thanks!!

Howdy,

Just wanted to add something.

The single most important determinant of rig performance, once the sails are attached to the spars properly is the amount of twist in the sail.

In the 1900s the balance lug was the premier small boat racing rig in the UK. This was because it handles twist better than an unvanged gaff rig - which was the main competitor at the time.

Then along came the bermudan rig and gunter lug - I can't be quite so categorical about why it was better than the earlier alternatives for small boats. Maybe the rig could be taller and higher aspect without adding to heeling force in the way a squarish sail would.

But when vangs first appeared at POW week in the international 14s - they showed clearly that the biggest speed determinant is controlling twist, particularly as the sail is eased.

Modern boats of course regularly have vanging systems that are 12 or 16 to 1 - so a 40lb input gives you about 480lbs of vang less the frictional losses.

The trend is really clear. But the open question is how much vang is necessary from a handling perspective as opposed to a speed one.

MIK

Originally Posted by woodeneye

Not being able to grab a bunch of central sheeting makes it very easy to "miss the moment" and a less than perfect gybe results. Grabbing a handful of central sheeting while going nice and fast is much quicker, especially when you have boats all around you as well. I've been thinking about central sheeting for the Goat for a while, together with a traveler along the rear edge of the seat. Last year MIK suggested I try this when were discussing this very subject on another thread. Gybing will be made easier and there is no mainsheet hanging under the boom to get hooked up on either. I'll have to give it a try very soon, as the end of the season is approaching with some rapidity!

A handfull of main sheet is what I am use to from sailing my Tornado. Gybes were done while facing aft, holding the tiller cross bar, grabbing a handfull of mainsheet and throwing the boom and lower part of the sail onto the other gybe while the upper part of the sail would follow a second later, but by then you where sitting on the windward hull and steering the boat. The crew would come aft just a little to bring those long sharp bows out of the water. There is no place to grab the main sheet on a GIS. The cental sheeting idea I like.

Now while rethinking the orginal question of this thread, How did the RAID41 capsize?

I may be confused here and have misunderstood, but I was always taught that all corners were done facing forward and turned aft and then around was not how to go to the other side in gybes or tacks because you lose orientaton, sight of other boats and cant see what the sail is doing.

G'day MIK
Glad you popped into the thread eventually.
Only one clarification re the angled chine panel - wasn't thinking of twisting it
into the plumb stem at all - just maintaining some angle all the way forward,
into an angled fore-foot. Probably only about 3" high at the stem. Might even
be able to get the ply out of the off-cuts from the sides panels. Maybe even
round off the angle transition from the plumb stem to hide the fact that it
is in all other respects a square boat.

Anyways.... jumping ahead a few steps in the logic here...
Probably the final analysis is that this long narrow square hull is the wrong
basis for a high-set permanent dry sleeping floor. A cat boat's proportions
are probably the more practical basis for that interior.

So, ditching the raised floor, finishing up with a more "boaty" Oz Racer might
perhaps be a more workable boat. Simpler build too. A system of removable
boards between rails along the side compartments could provide a dry
platform for those of us who want to sleep aboard. Something like what Mike
Monies did with Laguna for last year's Everglades Challenge.

My gut feel, rightly or wrongly, is that there is still a fast single-handed touring
boat lurking in there somewhere, for all of the dimensional reasons you
offered in the original proposal. Given that we now know that there are
things we don't know, and are not totally sure of what we do know, is it
worth the effort of trying to tease the beastie out of its lair ?...

Now that Teal is more or less sorted into something which sails reliably, (only
taken 10 years in between other projects..), I'd be up for some experimenting.
eg, following on from your comment the cat rig stability in GIS, add a third
mast step for a single sail in a Raid, as part of an on-water work-up.
Might be a bit of fun.
Once I get the gutters, eaves & fascias painted anyway.
cheers
AJ

Originally Posted by keyhavenpotter

I also agree with you!!!

I would not be without an adjustable vang. No way.

It's just that MIk is so against them that I thought by suggesting a simple preventer at least the boom would be stopped from lifting.

Brian

Phew, for a moment you had me worried that you had defected to the dark side!

I don't think Mik is against the vang idea at all. The basic set-up is nice and simple for most people who will build his boats. For those who like to tweak things a bit, Mik is only too happy for them to have a go and come up with something that works well. In a way, the GIS and OzRacer are development boats. (Hopefully one they will get class status!) Some of the mods being done on them, while far from extreme, cannot be done on most racing classes, so it's a bit of a fun factor really. What's really great is that he's around to offer advice so us builders can have even more fun with his boats. Where else do you get that?