Paradox Micro Cruisers and "Bilge Runners"

[mark_dugong]

Hi Everyone,:U
Out of curiosity,has anyone seen any "Paradox" micro cruisers which are micro coastal cruisers designed by a Matt Leyden. These small (14 ft) cruisers have even cruised to the Bahamas which seems remarkable to me for a 14 ft yacht.
Now, besides being such remarkable little vessels,they seem to resolve their lateral resistance problems with bilge runners,which are narrow horizontally extended wooden keels from the bottom of these flat bottom yachts-here is an interesting link
www.microcruising.com/ (http://www.woodworkforums.ubeaut.com.au/www.microcruising.com/)
What I am interested in, is can these bilge runners replace my somewhat cumbersome (but workable) leeboards on my lightly modified 25ft. Jesse Cooper of Bolger design?
Thus saving me some work in tacking and adjustments underway as well as losing two ropes.
Mark

[bitingmidge]

Mark,

I don't wish to be a perpetual knocker of things I haven't tried, heaven knows I do that enough with things I have! :rolleyes:

I like lots about Matt's stuff, but the bilge runners aren't one of them. WARNING: the following is just made up nonesense, the sort of thing I am often critical of others for writing:

It seems to me that when heeled the runner would present a concave face to arrest leeway, working a bit like a scoop if you like. This is both slow and inefficient. Much as I hate 'em, I think you'd do better with a long foil shaped keel as featured on so many cruising multis. Of course there goes your beachability, unless you do two of them.

I know, I know... Matt has had plenty of "racing" success, but I wonder at the quality of the opposition. I'd back myself in an identical boat with a proper foil shaped dagger board anyday!

I can't see a time when I'd have a sailing boat with a flat leeboard either mind you. I once had a Careel 18 trailer sailer, with a flat 1/2" steel swing keel. The final model of the Careel came with a foil shaped board and rudder, and despite being a huge percentage heavier than the older boat, the new model was untouchable in any conditions.... if the difference was that great in a heavy little tub like the Careel, it's hard to imagine the difference in something a bit more slippery!

Cheers,

P
:D

[mark_dugong]

Thanks BM,
Well, looking at the profile of the Paradox and the Jesse, they, like most sharpies have quite a long flat section from about 1/3 back to 2/3 back, which is where Matt has his bilge runners and I would also position the bilge runners on the Jesse there-so they would have quite a flat profile. As the side of the sharpie curves out along the line of of the chine also, that, I would imagine would also counteract the scoop effect.
I think I shall make up a rough and ready model.
I had thought of putting a long shallow keel on but I do really like the ability of the yacht to take the ground as they say-very useful for quick repairs and also the big sand flats are such interesting environments.
The race Matt Leydon won in his Paradox is quite a famous race about 350 miles long and open to all classes as long as they can be launched off the beach.
I do believe that the Paradox is quite a fast yacht for its' size and type.(although I would like to verify that), as well Matt is supposed to be a very good sailor. Apparently he also sailed somewhat offshore and used the ability to stay out overnight, whereas the other yachts and kayaks etc had to go in to camp for their rest periods.
The 'Dugong' has assymetrical foiled leeboards, however they can be difficult to adjust when under pressure and in a narrow channel.
I think I would just like the simplicity of not having to fool around with them.
Thanks again for that reply and look forward to that cup of tea sometime soon.
Mark

[Boatmik]

Howdy, was the racing success in the Everglades challenge? If so it is a rowing and sailing race over about three days. I think Matt was one of the progenitors of the event.

His division is row/sail - you can do either (or both) any time you like.

Basically it is heading down part of the intracoastal waterway, up and down a couple of rivers as well as scooting over the shallows of the Florida Keys.

In other words one of those events where rat cunning rather than outright speed can get you a big advantage. If so, It is not an open water (though part of it is) upwind downwind race by any stretch of the imagination.

I rather like his boats and have his page in amongst my bookmarks. It is a fresh and novel approach. Though having a closer look at some of the photos of boats built to his plans I worry about some of the fittings that the builders have chosen and the method of fixing.

Without further information I probably wouldn't be laying bets on the upwind performance of the boats one way or another - after all I only ever bet when it is a sure thing - and I don't know enough to say they go OK or not.

In general depth is the most important factor to get performance and the chine runners don't have that.

The second most important area is area and they don't have that either.

I did just find an article which is a bit self contradictory saying both that the small boats sailed just as well without a centreboard as without as well as saying that a sharpie with the runners "sails sluggishly" with the centreboard raised and only using the runners.

Here's the link
http://www.culturechange.org/cms/index.php?option=com_content&task=view&id=67&Itemid=33

MIK

[bitingmidge]

Well even though I'm not a betting man, I'll take you on!

I like to use the "if it's any good" they'd be doing it rule, then run off to see the 18 footers or the moths or even the America's cuppers to see if they've got them.

Nup.

No leeboards, no bilge runners. No multihulls! :oo: :oo: :oo:

Hmmmmm....

P
:D

[b.o.a.t.]

Hi Everyone,:U
Out of curiosity,has anyone seen any "Paradox" micro cruisers which are micro coastal cruisers designed by a Matt Leyden. These small (14 ft) cruisers have even cruised to the Bahamas which seems remarkable to me for a 14 ft yacht.
Mark

G'day Mark
haven't seen one, but a UK bloke who has one has been contributing this week on Openboat mail list at Yahoogroups. He says it doesn't perform as well onto the wind as a modern centreboard dinghy, but better than some old timers.
Am seriously thinking of conducting *another* experiment with my Bolger Teal to see if some bilge winglets would significantly help my too-small non-standard daggerboard. Without killing the rowing, that is. Right after I build a couple of canoes & fix the leak in the shower....

Layden races his Paradox very successfully in endurance races, but as he seems to only need a couple of hours sleep per week & quite happily runs a half marathon dragging the boat following a 20 mile scull up a river, it could just be that he outlasts the competition.
cheers
AJ

[mark_dugong]

Thank you all,
You just about convinced me out of it!
Then I found this letter from Matt Leydon on the Microcruising website-the rest of the letter is also on the website under Forum contents-so take this you unbelievers!


The data all seemed okay, but there were fluctuations of several percent from one run to the next on each leg, and the last 2 legs were complicated by the arrival of a short rain squall that made the wind a little uneven for about 30 minutes, so I would say that there is a margin of error of at least 1/10 knot in the results, I think doing much better would probably require a towing tank.I will include a copy of the raw data in case you are interested, but the short results, averaging the 3 runs for each leg, go like this:
Downwind leg VMG: 4.53 kt.
Starboard tack VMG: 3.63 kt.
Starboard tack angle made good to wind: 51 deg.
Starboard tack VMGW: 2.29 kt.
Port tack VMG: 3.49 kt.
Port tack angle made good to wind: 51 deg.
Port tack VMGW: 2.21 kt.
(VMG = Velocity Made Good along course; VMGW = Velocity Made Good to
Windward)
These results pretty much bear out what I have observed before, so I'm willing to believe them. There may be a slight improvement in the modifcation to the port runner (the difference if any is within the margin of error so I can't say for sure) What this mostly does is tell me in numerical terms that yes, she really does go to windward passably well without a centerboard, and no, the as-built chine runners are not dismally bad though they may be susceptible to improvement. It supports my experience that in real world conditions, the rare few times Paradox has been near other small shallow-draft cruising boats, she has usually sailed right past them, upwind or downwind. This of course isn't because Paradox is a particularly fast boat but because, by and large, other other small shoal cruisers are not particularly fast either.

I watched a youtube on the Little Cruiser paradox which does have a centreboard and she was doing 4-5 kts reefed in a estimated 15 kt wind admittedly it was downwind but they were fully loaded.

By the way Boatmik that website you referred to was fascinating-I think I better start preparing for the end of the world as we know it ,start growing some vegies and learn to fish-at least I have the right yacht.
I reckon you ought to go ahead and put those "bilge" or I stand corrected chine runners on the Teal after you've finished the shower,AJ.
Mark:U

[b.o.a.t.]

Thank you all,
By the way Boatmik that website you referred to was fascinating-I think I better start preparing for the end of the world as we know it ,start growing some vegies and learn to fish-at least I have the right yacht.
I reckon you ought to go ahead and put those "bilge" or I stand corrected chine runners on the Teal after you've finished the shower,AJ.
Mark:U


Not an unbeliever at all. Intrigued enough to be willing to experiment.
Got just a few things on the 'to do' list ahead of it.
By which time it may have fallen off the bottom of the list.
Or not.... ;-)
cheers
AJ

[Boatmik]

Not an unbeliever at all. Intrigued enough to be willing to experiment.
Got just a few things on the 'to do' list ahead of it.
By which time it may have fallen off the bottom of the list.
Or not.... ;-)
cheers
AJ

Howdy AJ,

It would be interesting to see how it went on the Teal!!

MIK

[Boatmik]

By the way Boatmik that website you referred to was fascinating-I think I better start preparing for the end of the world as we know it ,start growing some vegies and learn to fish-at least I have the right yacht.[/FONT]
Mark:U


A boat with a vegetable garden - OK midge - where are those links of yours!!!!

MIK

[mark_dugong]

"A boat with a vegetable garden - OK midge - where are those links of yours!!!!"

Vegetable gardens ?? On the "Dugong" !!!
Come on Mik, whaddya reckon about the Paradox sailing data. Any ideas?
Cheers
Mark :U:aro-l: i'm getting sick of this guy.

[Boatmik]

Howdy - if you want some comments .. here they are.

GPS readings are next to useless. What was the current at the time? That's what you need to know. And we don't know the windpeed or the water conditions.

2.2 as VMG upwind is OK for such a little boat, but I don't think I've sailed anywhere but at Goolwa where there is current of less than half a knot. Its almost too small to perceive if you aren't reaching or running using a transit. On my former racing grounds on Sydney Harbour a couple of knots was more common.

But bye and bye - like Peter - there doesn't seem much evidence of a performance breakthrough. I'd sure like to know how Matt's boats go with the chiny things planed off.

Part of it too might be that the microcruisers are being asked to carry a considerable displacement in a narrow and short hull making it quite deep enough to develop a good degree of lateral force itself. I wouldn't be guaranteeing that a shallower boat would show the same pointing angles.

Woudl be nice if the experiment can be done on the windsprint! Rough water will be where the performance will drop off - as it does with any boat with limited lateral plane.

But just to be clear - I REALLY LIKE MATT'S BOATS - AND I KNOW MIDGE IS A FAN TOO.

MIK

[bitingmidge]

I like lots about Matt's stuff, but the bilge runners aren't one of them.

But just to be clear - I REALLY LIKE MATT'S BOATS - AND I KNOW MIDGE IS A FAN TOO.
Just to be doubly clear! :p

I'd hate to see a theoretical discussion turn into a bagging of something that we haven't tested!

Cheers,

P
:D

[b.o.a.t.]

Part of it too might be that the microcruisers are being asked to carry a considerable displacement in a narrow and short hull making it quite deep enough to develop a good degree of lateral force itself. I wouldn't be guaranteeing that a shallower boat would show the same pointing angles.

Woudl be nice if the experiment can be done on the windsprint! Rough water will be where the performance will drop off - as it does with any boat with limited lateral plane.

But just to be clear - I REALLY LIKE MATT'S BOATS - AND I KNOW MIDGE IS A FAN TOO.
MIK

I wonder just how much parallel there is between bilge runners & Bolger's rudder plates, where he is (supposedly) getting 'bite' far out of proportion to very small rudders. I had a very small 'temporary' rudder for several years on Teal, & most of the time it was .... adequate. However, in rough water "performance dropped off" indeed !! :o

In the shallower boat, wider winglets might be a better bet, extending perhaps 4 or 5 inches outwards & 18 - 24 inches long. I don't know the maths at all but it seems to me that these would greatly reduce the tendency of the light-displacement sharpie to skate sideways. Especially when lightly loaded. Would also reduce the tendency to skid in sharp turns under oar when playing 'tag' with the kids in their canoes.
cheers
AJ

[Boatmik]

Howdy,

Yep bilge runners and Bolger's rudders are close relatives.

As are bulb keels.

Wing keels too - but you can't design effective ones without considerable computational power - otherwise they are just a high tech looking cartoon - rather than working as per the advertising. :-)

All of this is quite well known in design circles. Bolger in his books also mentions that the external chine logs of his sharpies "MAY" (his word) reduce crossflow at the chine.

The rudders do work. But the horizontal fin is large compared to the size of the rudder.

You've got to love the way Bolger is always so careful with facts. That's one of the great things for careful readers of his books - you can see what he actually thinks because of his careful use of language.

I really reckon that the hi tech yachting world owes him a debt - he was playing with canard steering yachts and publishing his thinking in one of his books not long before they tried them in 12 metres in the '80s.

The modern bunch of canting keelers might not be around if it wasn't for the 12 metre.

Interesting!

MIK

[mark_dugong]

Hi,
I think this further quote from Matt Leydens letter shows he was aware of your concerns about current and GPS Mik. Unfortunately no statement about wind strength except he did go around the marks about three times to average things out.


"I took Paradox out to a part of the Indian River ... where there is practically no current, uniformly deep water and little boat traffic, and did a series of timed runs to try to quantify her windward performance and determine if the modified chine runner on the port side was an improvement.
I tried to do what I reasonably could to keep inaccuracy from accumulating, but I don't really know how good the results are. I laid out a triangular course with legs over a mile long, using fixed channel markers and a point of land that were all on my chart, but I don't know for sure how accurately they are plotted on the chart. I took compass bearings and did some timed runs to other charted features nearby; everything checked out reasonably well, so I'll use the data as they stand, but I would really like to double check the mark positions by GPS or survey from shore some time."

Yes, it is a good point that variations of chine runners have been used in other forms such as rudders and winged keels.
My twin rudders on the 'Dugong' also have horizontal fins and I feel they do contribute to the performance of the rudders and I am very happy with them. The horizontal fins were a part of the original design of 1975 I think-(the twin rudders weren't)

Those chine runners, though, I am sorely tempted to try them out on the 'Dugong' when I get back to home port.

I am sure you are aware Bolger uses the chine runners on the Tennessee as I noted on the 'Umilgumili' over here on the Brunswick river-I think Duck Flats made up the kit for the owner of it. Anyway I saw 'Umiligumili' going into quite a sharp bend at speed with no sign of sliding at all-I was impressed!

And I do like Bolger's books and I am saving up to buy one.
Cheers
Mark

[b.o.a.t.]

Howdy AJ,
It would be interesting to see how it went on the Teal!!
MIK

Well the original shower leak is fixed (the floor-pan is now cracked, but the duct tape is holding so far..). Another kayak is built & tested (& alterations to design made). 'Eureka' looks like being a spring project due to funding issues caused by the aforementioned cactus shower base. Time to use some of the oregon rafters recovered from the neighbour's renovation & carefully stashed in the backyard under the apricot tree...

Stinker of a day - 39'C according to the thermometer on the back verandah. Moved work-site under the trees in backyard as per photo. Winglets are 1M long & 3" wide for most of their length, widening to almost 4" at rear. (Sorry about the mixed measurement systems - I'm of the changeover generation - fluent in both and neither)

Location is by guestimation, based on a fuzzy memory of how the boat had significant weather helm when last I used the 'big' lug sail. Been using a smaller but much more effective fully-battened Gunter I cooked up for my daughter's micro-catamaran for the last couple of years. But that is up for sale at the moment, so back to the lug-sail it is.

The dowels are to stop them from breaking along the grain. The epoxy securing the dowels & filling some nail holes is curing as I type. Insofar as this is planned, I will finish shaping them, coat them with epoxy, & temporarily screw them in position. Then test sail & amend location/shape, then epoxy/glass them in position. Or discard them. God willing & there still be at least some water in the lower Murray R. that could be as early as late next week. Or not...

Here's hoping...
cheers
AJ

[Boatmik]

Howdy AJ,

I would be reckoning on altering the shape once it is all glued up so the long edges are radiussed and the leading and trailing edges made more foil-like.

Leading edge shaped in a half ellipse. The trailing edge tapered down to a flat edge about 1/4" wide.

The distance of shaping for the trailing edge - maybe 5 times the timber thickness.

Are you going to just fit it on one side and have the standard leeboard on the other for comparison?

MIK

[Boatmik]

oops - I mean centreboard (looked more closely at the pics!

[b.o.a.t.]

Howdy AJ,

I would be reckoning on altering the shape once it is all glued up so the long edges are radiussed and the leading and trailing edges made more foil-like.
Leading edge shaped in a half ellipse. The trailing edge tapered down to a flat edge about 1/4" wide.
The distance of shaping for the trailing edge - maybe 5 times the timber thickness.

Are you going to just fit it on one side and have the standard leeboard on the other for comparison?

MIK

Something like that MIK. At this stage just rough-shaped & tapered to fit the hull & insert reinforcing dowels. Will do most of the shaping off the hull - rounding & tapering & etc. Hard to compare shape of the two winglets for sameness if they're on opposite sides of the hull. :rolleyes: I dare not go seriously thin with the trailing edges because of the vulnerable location of the winglets. The boat tends to get dragged sideways off the trailer & dumped chine-first onto the ground - they are presently tapered to about 16mm from about 25mm max thickness. Most Paradox's appear to be just the 3/4" or 1" thick bottom panel extended past the sides & filleted - seriously robust! The one other photo I've seen (which I cannot now find) showed more like this shape of winglet but still with a pretty solid trailing edge. And that on a boat that goes fore-and-aft on & off the trailer, not sideways & *drop* !

Anyways, there is much yet to do, including figuring out a temporary yet moveable fastening system for testing that is strong enough but doesn't let water into the boat or the winglet. The boat is 6mm gaboon with no framing. Tempting to just glue & glass it & remove bits as required to amend trim...

cheers
AJ

[b.o.a.t.]

Winglets shaped & epoxy coated. Waited until after midday to apply first coat on a cool day that wasn't warming. 20 minutes after completion and as I left for work, the sun came out & turned the shed into a sauna.

Out-gassing ..... UGH !!! Home at half past midnight, sand it all back & recoat. Bed at 2am. Only did the one. The other can wait until I know whether it is a crock or not.

Fastening is 3 holes drilled oversize near chine & back-filled with epoxy goop. Tape over them & the winglet face & put drywall screws through the tape. Should keep most of the water out, & allow movement fore-and-aft to adjust balance. Big washer and strip of ply on the inside to avoid doing the boat a mischief from concentrated stresses. Might even get to try it this weekend if the weather & other appointments co-operate.

Waved a measuring stick at it last night too for the first time since mark-out. The oregon is actually 35mm thick on the face, so there's a fair bit of taper to the ends & out to the edge (28mm in the middle).

[b.o.a.t.]

Well, weather & other appointments refused to co-operate. But the port winglet is now temporarily attached & screw holes filled ready to get wet.

Recovered a bundle of meranti slats from a set of louvered kitched cupboard doors a decade or so ago. Still finding uses for them, in this case, aligning & supporting the winglet while I drilled & screwed it.

Duct tape over the hole in the boat and over the hole in the winglet. 50mm perma-pine screws fastened through the tape with cup washers & pads inside to add support. Next weekend will be a 4-day one (shift changeover) so hopefully will get a chance to try it out.

(The micro catamaran in the background is up for sale if anyone wants an experiment that worked surprisingly well. Adelaide sthn suburbs - make me an offer!)

[b.o.a.t.]

Test sailed it today (Monday) with port winglet only temporarily attached.
The difference was simply stunning !!
For the first time ever, I was able to sail towards a target rather than crab towards it. (I may have mentioned before that the dagger board I made for my Teal is too small. Comparative pic below as to just how small (950mm x 280mm).) Using channel markers as leads I estimate close-hauled leeway was down to maybe 5deg compared with around 20deg on the opposite tack without the winglet.

Observations...
1. Lake Alexandrina is desperately low. Despite drawing only about 700mm, most of Clayton Bay & the Finniss River Junction was unusable. I had to stay in the marked channel. Even 4 months ago it wasn't that bad. Still bottomed out in parts of the channel, especially near Old Clayton point on the northern side. In the Clayton Bay Jetty pics below, the water level -should- be just above Teal's boom.

2. My recollection with this particular sail of the boat having bad weather helm was just plain wrong! The too small daggerboard means it needs heaps of lee helm to keep from blowing off down wind. Can't figure out how I ever managed to sail it down the Finniss from Knott's Landing. (narrow creek, flukey breeze)

3. The winglets on their own are not big enough to beat to windward. That's ok - they were only ever intended to supplement the too-small centreboard. They are big enough to reach, albeit with perhaps 10-20deg of leeway. Ok for skinny water & weeds. Without winglet or dagger board, Teal just slides sideways nearly as fast as she can slide forwards.

4. Despite their widest point being well aft of the CB, they actually induced weather helm, not lee helm. Pulling up the dagger board made the weather helm even more pronounced. I deduce this means that the front bit where the boat is still widening towards maximum beam is doing the lion's share of the work. Very likely, the front 1/3 is producing 80% of the result.

5. Under oars, trimmed reasonably level in a dead calm, the winglet produced neglible drag. Tested by stopping rowing & seeing which way the boat slewed. Always to port, eventually, but only gently.

Anyway, the winglets are about to become permanent fixtures.

cheers
AJ

[Boatmik]

Great work on this AJ!!!



Observations...

2. My recollection with this particular sail of the boat having bad weather helm was just plain wrong! The too small daggerboard means it needs heaps of lee helm to keep from blowing off down wind. Can't figure out how I ever managed to sail it down the Finniss from Knott's Landing. (narrow creek, flukey breeze)

Sounds like the centreboard is in the wrong place - as you suggest.


3. The winglets on their own are not big enough to beat to windward. That's ok - they were only ever intended to supplement the too-small centreboard. They are big enough to reach, albeit with perhaps 10-20deg of leeway. Ok for skinny water & weeds. Without winglet or dagger board, Teal just slides sideways nearly as fast as she can slide forwards.

This was the main bit of information I was interested to hear. There had been a lot of hype that they worked well by themselves. Perhaps with Matt's boats the greater depth of hull makes them work better still, but I would be very surprised if they were in the same category as a properly designed centreboard (or leeboard for that matter).


4. Despite their widest point being well aft of the CB, they actually induced weather helm, not lee helm. Pulling up the dagger board made the weather helm even more pronounced. I deduce this means that the front bit where the boat is still widening towards maximum beam is doing the lion's share of the work. Very likely, the front 1/3 is producing 80% of the result.

This is spot on with theory. Basically you get the most lift from where the water has to change direction the most - and most is going to be at the front end. By the way ... that's why deeper foils work better than short ones - they bend more water because they have more "front end"!

But if you don't have more water - then it is a good idea that might make sailing practical.


5. Under oars, trimmed reasonably level in a dead calm, the winglet produced neglible drag. Tested by stopping rowing & seeing which way the boat slewed. Always to port, eventually, but only gently.

That makes sense too. Generally there are two main components of appendage drag. Surface area and frontal area. Both are negligible in relation to the cross section and wetted surface of the boat. There might be more drag as the boat goes faster from wave drag effects - but I won't be betting any money as to the size of the effect.


Anyway, the winglets are about to become permanent fixtures.

cheers
AJ

It is great that this experiment has solved your problem!!!!

One extra suggestion would be the general guidance that if your lateral resistance is too small it starts to make a lot of sense to sail the boat faster upwind. Keep the sail/s eased a few degrees wider and go that little bit faster.

Best wishes
Michael

[b.o.a.t.]

G'day MIK



This was the main bit of information I was interested to hear. There had been a lot of hype that they worked well by themselves. Perhaps with Matt's boats the greater depth of hull makes them work better still, but I would be very surprised if they were in the same category as a properly designed centreboard (or leeboard for that matter).


Probably not, but I think they could be made to go close. Certainly enough to make additional gain from a vertical appendage not worth the extra engineering effort for some boats & in some applications. My winglets are very small indeed. I'd imagine if they were doubled or trebled in size (mostly length), one might get by without any leeboard at all.... most of the time.
(Someone else can try that one... too hard to retrofit to an existing boat.)



But if you don't have more water - then it is a good idea that might make sailing practical.


Perzactly ! Right at the moment, even 700mm draft is too much... from what I've read of the handling characteristics of shallow draft boats such as Chebaccos & Scruffies, horizontal appendages have got to be worth a serious look for us enforced skinny-water sailors.



That makes sense too. Generally there are two main components of appendage drag. Surface area and frontal area. Both are negligible in relation to the cross section and wetted surface of the boat. There might be more drag as the boat goes faster from wave drag effects - but I won't be betting any money as to the size of the effect.


I'd expect these little wings to be largely unaffected. Teal is pretty slow with my little sail & excess bulk... Wind speed varied from dead calm to about 12-15kts yesterday. I came in to a lee shore with a serious bone in the teeth, and rounded up in 200mm of water with no trouble at all. Try & do -that- in any other sharpie !! For this one trick alone, they are worth the effort.



It is great that this experiment has solved your problem!!!!


plus one or two that I didn't know about...



One extra suggestion would be the general guidance that if your lateral resistance is too small it starts to make a lot of sense to sail the boat faster upwind. Keep the sail/s eased a few degrees wider and go that little bit faster.


That's what I've been doing MIK. Bear away, pick up speed, when the board "bites" point up just far enough to maintain speed. Board has been operating just shy of stalling or stalled. Yesterday's trial showed this should no longer be an issue.

Thanks for the comments MIK.
cheers
AJ

[Boatmik]

Thanks for doing the work and presenting the results here AJ.

Bless your cotton socks!

I think that there are some disadvantages to the chine "wings" as they get bigger. One is that they start to become quite vulnerable to damage.

The other is that as the boat heels their effectiveness becomes greater - so there my be a tendency for bigger ones to trip the boat at speed or in a gust.

But you have an opportunity to test that - look forward for feedback in those areas too.

MIK

[b.o.a.t.]

The other is that as the boat heels their effectiveness becomes greater - so there my be a tendency for bigger ones to trip the boat at speed or in a gust.

But you have an opportunity to test that - look forward for feedback in those areas too.

MIK

Won't have opportunity to test these two things MIK. Wings too small, Teal too slow. However.... if The Midge could be prevailed upon to fit something similar to his GIS.... :U

cheers
AJ

[b.o.a.t.]

Well, the winglets are now permanently attached. Short of an angle grinder anyway. Has added a good 1 or 2 Kg to the total boat weight. Could have gone with less glass cloth but wanted to do some stiffening & reinforcing in a couple of 'soft spots'. Took opportunity to remove paint in areas where it had cracked through to the timber, dry them out, & recoat with epoxy. Evidently just 2-3 coats of epoxy is insufficient in these areas to prevent splitting along the grain. It is tempting to obtain some of this 2oz glass cloth of which Mik speaks to cure the splitting 'properly'.

Will be 6 weeks or so before I get a chance to do any more. MIK has suggested a larger sail & some knees under the mast partner, so those will be next, as per drawing. Plus a larger rudder blade. Should be a vastly more pleasant little boat to sail once all is done.

[b.o.a.t.]

http://www.freewebs.com/paradoxbuild/buildingblog.htm

just stuck the link in here for my own reference (& so I don't lose it)
good close-ups of Paradox chine runner construction

[Boatmik]

Won't have opportunity to test these two things MIK. Wings too small, Teal too slow. However.... if The Midge could be prevailed upon to fit something similar to his GIS.... :U

cheers
AJ

A follow up thought (because I have just written about this concept in another thread) ... I don't think the Paradoxes are particularly fast at that displacement and length - so the Teal is probably a reasonable approximation.

But TEAL is a very light shallow boat - so certainly does not have the hull depth of the Paradoxes.

That it still does not go REALLY well to windward using both the undersized centreboard and quite large (compared to the Paradox) runners together and only does sortof OK on runners alone indicates one of the below is true

1/ The concept of bilge runners works best on deeper heavier boats
or
2/ The deeper hull in combination with the bilge runners is an optimum use of the idea or
3/ The concept has only marginal use and it is the deeper hull providing the lateral resistance. Remember that the Paradox is a similar or similar hull depth to many centreboardless cats which can also go to windward OK without centreboards. They have more speed which helps generate lift, but also they have much, much more sail which will require much more lift anyhow.

Move to slower centreboardless catamarans like James Wharram's and you lose a lot of upwind performance. So much so that his boats are sprouting shoal keels - I remember James saying how such things were "completely unnecessary" ... but back then he also said that bridgedeck cabins were "unsafe" and that feature is appearing now in his designs -the danger of making 100% type statements for things with no theoretical base! The reality is he "likes" particular features - which is valid enough in its own terms of course.

But in a way ... which reason is correct is unimportant because the concept of Matt's Paradox boats is simply extraordinary and it is clear the the package works as a whole - whatever theoretical spin is put on "why".

Best wishes
Michael

[b.o.a.t.]

That it still does not go REALLY well to windward using both the undersized
centreboard and quite large (compared to the Paradox) runners together and only does
sortof OK on runners alone indicates one of the below is true

1/ The concept of bilge runners works best on deeper heavier boats
or
2/ The deeper hull in combination with the bilge runners is an optimum use of the idea or
3/ The concept has only marginal use and it is the deeper hull providing the lateral
resistance. Remember that the Paradox is a similar or similar hull depth to many
centreboardless cats which can also go to windward OK without centreboards. They
have more speed which helps generate lift, but also they have much, much more sail
which will require much more lift anyhow.


G'day MIK

Only thing I disagree with here is the word "or".
I think it is a combination of all 3. The runner works primarily as a chine fence turning
the whole of the deeper hull into a lifting body. Even on the light-weight Teal, the
runners make enough difference to provide manoeverability without the dagger board.
Without the runners, when rounding up, Teal just skates sideways nearly as fast as it
can go forwards.

One thing I neglected to mention earlier - my dagger board has very nearly the same immersed
surface area as Bolger's designed leeboard. It would be nice to think that the time I spent on it
attempting a NACA0012 profile makes it a more effective device than Bolger's simple flat lee-boards.
The key difference between Teal as designed & my boat is that I didn't use Bolger's double thickness
external chine logs. Since there are not heaps of reports that the as-designed Teal is a rotten sailor,
it stands to reason that I have merely replaced something provided by those chine logs.

Anyway, once I fit a decent sail (you have to admit the one on her now is pretty ordinary) I think the
higher speed will increase lift & effectiveness of both devices.



But in a way ... which reason is correct is unimportant because the concept of Matt's
Paradox boats is simply extraordinary and it is clear the the package works as a
whole - whatever theoretical spin is put on "why".


Hear, Hear !!

cheers
Alan J.

[Boatmik]

Howdy AJ,

Yes .. forgot about the sail! So we will see I guess!

MIK

[b.o.a.t.]

Howdy AJ,
Yes .. forgot about the sail! So we will see I guess!
MIK

Well, as I wrote off list to you the other day MIK, I was going to start cutting polytarp Thursday.
But it got bit busy with the wife off to the doc & a few other bits & pieces (I'm supposed to be on sick leave!!). Then I was gunna start cutting today, but got caught on long phone calls, writing stuff for CFS & cooking. SO, I'm gunna start termorrer.
Or maybe Sunday. Or maybe Monday after shuffling pianos between rooms. Or possibly Tuesday after the plumber has done the tank... Or maybe next Julember... :~

Anyways, here's the latest version. It's the largest I can squeeze into a 2.9 x 3.5M polytarp. ($11) Any bigger & I have to go to a $22 polytarp. :o 53sq.ft is as big as a Nutshell 9'9" & near double the existing 30sq.ft.
I predict a significant increase in speed, & if I fail to get reefing right, a significant increase in involuntary wetness.

By the way, Ted sent the PDR plans on Thurs am (as expected). Haven't read them all the way through yet. Might print a few pages & show them to the bloke who organizes the local 'Shed' on Sunday. Not sure if it's something he'd go for - they tend to be into *really* low-cost projects. Scrap timber stuff. But seeds will be sown, and you never know... :wink: The surgeon said last week I might be looking for "after the CFS" sooner rather than later...

cheers
AJ

[Vernr]

:wink: The surgeon said last week I might be looking for "after the CFS" sooner rather than later...


........I can really recommend the "after the CFS" bit, AJ..............there IS life after Fire Brigade!!!!

Cheers,
Vern

[b.o.a.t.]

........I can really recommend the "after the CFS" bit, AJ..............there IS life after Fire Brigade!!!!

Cheers,
Vern


Yeah, but you're a certified oldie, Sir Vern. :wink:
You've been there, done that, & rest on your laurels.
I can still pretend to be young, (at least to myself, and so long as I stay away
from mirrors & avoid genuinely young peoples' conversations !) :D
When I'm old I'll settle down to a more relaxing hobby.
cheers
AJ

[b.o.a.t.]

Well the fully modded Teal has hit the water at last, still unpainted.
Huge improvements in a number of areas.

With the bigger rudder, it turns when told to do so, not just when asked very nicely
with much coaxing and promises of ice-cream & lollies. Not in the league of Nutshell
or Tender Behind, but acceptable.

The larger sail accelerates the hull to full comfortable displacement speed quite easily.
Winds on West Lakes today were flukey 5 - 10 kts early, increasing to 10-15 kts later.
Was tempted to start reefed but glad I didn't. The low sail plan is really quite manageable
at these wind speeds. A couple of close calls, but no dunking today. Shaped the spars
loosely scaled to MIK's PDR balanced lug. Lots of flex in gusts. Yard looked close to
breaking a couple of times. Didn't tear out any grommets but the clew grommet
looked a bit strained - I built the sail edges a bit light as I was going to sew it... Not
enough power to plane, but enough to dig a big deep hole with big rolling following waves
to rock the kids doing outdoor ed in canoes. A lighter crew would go faster...

Odd behaviours... strong weather helm beating on starboard tack (sail carried to
starboard) but slight lee helm on port tack. Also seemed a little more powerful on
starboard tack.
Have added a couple of older pics of previous rigs as well as today pic at West Lakes.
cheers
AJ

[m2c1Iw]

Odd behaviours... strong weather helm beating on starboard tack (sail carried to
starboard) but slight lee helm on port tack. Also seemed a little more powerful on
starboard tack.


Look good AJ.:2tsup:

What are the tape crosses for?

Re the weather helm is this because you are acheiving a tighter sheeting angle on startboard? In any event the lug CE looks further aft but that does not explain lee helm on port, odd.

Mike

[b.o.a.t.]

Look good AJ.:2tsup:

What are the tape crosses for?

Re the weather helm is this because you are acheiving a tighter sheeting angle on startboard? In any event the lug CE looks further aft but that does not explain lee helm on port, odd.

Mike

Thanks Mike.

The tape crosses... ah yes... making a failth statement... well, not exactly...

I spent the exhorbitant sum of $11 on the polytarp at a local Mitre 10. On hoisting it in
the back yard to figure out the rigging and getting some tension into it, was alarmed to
realise I could see right through it at a number of points in a line the full height from
peak to foot. :oo:
Looks like the manufacturers cutter took a half-hearted swipe at it. Didn't notice the
cuts while it was on the lounge room floor. :doh:

Was suddenly relieved I -hadn't- been able to repair the sewing machine I acquired
to sew all the seams... Saved a lot of work on what may be a fairly temporary sail.


Logically, the lee/weather helm means the centre of sail effort is moving forward
appreciably when the mast is not interrupting the sail shape. I sheet to the tiller,
about 50mm forward of the pintle, so any sail pressure -should- induce weather helm.
Should...

Possibilities....
The light polytarp is -very- soft, & my spars are very light so there perhaps isn't
enough fore-and-aft tension in the sail to resist the mast interruption. Could be a case
made for inserting a couple of battens like MIK's "Beth". Easy done, as per the gunter
main I had on Teal before this.
I also note I drew the sail with the foot somewhat aft of where it was sitting on the day.
That might make a difference too.
And I didn't lash the boom to the mast so it sagged out maybe an inch or two on port
tack.
Combination of all 3 perhaps ?
Hopefully one day MIK will cast his jaundiced eye across it, scratch his chin, shift his
weight from foot to foot, & announce it's a crock & should be ritually burnt... :U

More fiddling next time !! And hopefully see how it performs against a PDR.

cheers
Alan

[m2c1Iw]

The tape crosses... ah yes... making a failth statement... well, not exactly...

Mm.....wondered if it was a statement about our current economic malaise:rolleyes:



Possibilities....
The light polytarp is -very- soft, & my spars are very light so there perhaps isn't
enough fore-and-aft tension in the sail to resist the mast interruption. Could be a case made for inserting a couple of battens like MIK's "Beth". Easy done, as
Hopefully one day MIK will cast his jaundiced eye across it, scratch his chin, shift his
weight from foot to foot, & announce it's a crock & should be ritually burnt... :U

Nah he's much too polite, more likely say it can be saved just needs more luff tension.:D




More fiddling next time !! And hopefully see how it performs against a PDR.



Well hopefully my PDR is not far off so a bit of comparitive data collection is on the cards soon:D

Mike

[Boatmik]

Howdy AJ,

The rig looks much more in proportion to the boat. I'll be betting it does EVERYTHING a lot better.

Nice to see that Mike is making some threatening noises!

MIK

[Clarkey]

Hello All,

Diving into this really late I know but I have always assumed that most of the windward performance of Paradox is probably due to that really big rudder hanging off the back. Combined with the 'lifting body' effect of the heeled hull shape and the relatively far aft CoE, the rudder must provide a big chunk of lift.

I guess that the chine runners help reduce leeway a bit but am inclined to believe that their main effect is to improve the steering characteristics and possibly directional stability.

Just my two-penneth worth.

Chris

[Boatmik]

I have been meditating on this ...

I think it is almost all to do with the depth of hull in the water vs the very modest sail area. The hull sides are enough of a "keel" by themselves and the rudder and "lifting body" arguments augment the effect of the deep hull.

Best wishes
MIK

[PAR]

Michael, picture one of these hulls heeled over at say 10 degrees and try to imagine the waterlines. The 'rounding tendency will be strong, so all you have to deal with is leeward slip and steerage. If the runners are well placed, much of the slip can be handled, especially if the bearing area and basic "centers" are relatively close to each other, which appears to be the case with Paradox. Of course there are shape and performance limitations with this approach, but it's valid enough to work moderately well.

[Boatmik]

Howdy Paul,

Yep, all visualised. Yes ... agreed about the moderately well (read my earlier posts about how good I think the Pardoxes are ... they really are a new type of boat in my book. There have been other micro cruisers, but the sense I get is most were real downwind machines.

I am impressed that the Paradoxes can get upwind at all ... and can see the reasons.

Just wanted to add the depth of immersed hull to the discussion because it is a major feature of the boats and that the chine lips won't be hugely effective on shallower boats.

Happily we have AJ here who is experimenting with exactly that.

Before the boat was a bit undercanvassed .. now it looks about right ... so will be interesting to see the difference it has made.

Best wishes
MIK

[b.o.a.t.]

Just wanted to add the depth of immersed hull to the discussion because it is a major feature of the boats and that the chine lips won't be hugely effective on shallower boats.

Happily we have AJ here who is experimenting with exactly that.

Before the boat was a bit undercanvassed .. now it looks about right ... so will be interesting to see the difference it has made.

Best wishes
MIK


I thought the depth of immersed hull was -always- a key part of chine runner operation.
If acting as a fence, there needs to be water trapped above it to work. The more water
trapped, the more effective.

Found last week that it was possible to "switch" the winglets on & off by varying heel
and pitch. Nose up & sailing flat, the board had to do all the work. The winglets
seemed to be neutral or even lifting. Bringing the nose down applied water pressure to
their top surface & I could beel them 'bite', albeit gently. Add a small amount of heel,
and they'd bite harder, leeway being visibly reduced.

Adding to the idea of needing hull depth, Teal is very shallow draft, even shallower
once it gets close to hull-speed & mid-ships is in a trough. At speed, Teal needs to
heel to get any significant effect from the winglets. At speed of course, the NACA foil
is at its most effective & they are less needed, although provide noticeable improvement.

cheers
AJ

[Boatmik]

Good Stuff AJ,

I was very interested to see how effective the horizontal winglets were operating by themselves rather than augmenting that centreboard. It is a bit unfair to call them bilge runners as yours are much bigger and we are both expecting will be more effective than the minimal ones on Paradox.

I was very interested to see how they went now the boat is able to go quite a bit faster with the bigger sail. Sometimes a boat with undersized lateral plane can be made to go better by sailing it faster.

My feeling when sailing your boat with the original sailplan was that it was quite underpowered and that may have been a contributing factor.

(PAR ... be aware that AJ's boat is a testbed of ideas.

Did you do any sailing with the centreboard pulled up?

If it is still weak that means that the Bilge winglets really don't work very well in terms of normal windward performance ... though they are enough in combination with the centreboard to give other advantages such as the opportunity to sail in real shallow water more.

I think that the depth of the hull and as both you, Clarkey and PAR point out it is the sail being aft and the rudder working and as I pipe in to support ... the depth of hull.

So we it looks probable the winglets ... BIG runners ... are not effective enough by themselves on a shallow boat.

So the question rises ... wonder how the deeper boat would go without them.

Paul, you caused me to wake up in the middle of the night!!! I remembered that I had not been terribly impressed by arguments about the performance enhancing characteristics of a certain range of "half entrance angle" as touted in some texts because Bolger made a comment years ago about why he keeps the stems of his boats clear of the water.

If the sides of the boat have a bluff entry angle but are clear of the water ... ie the bow entry angle is wide ... but the angle the bottom panel makes is very shallow ... then this oversimplification about half entry angles falls to bits.

I imagine it had a huge effect on Kunhardt style cutters ... where the stem goes down and down almost to the full draft of the boat.

But it is hugely irrelevant for shallow hullforms unless they too have the stem going down to the full draft of the hull body.

So I don't think the waterlines can be looked at in isolation. I know you didn't quite mean it that way. I generally dont attempt to visualise flow at all around the hull ... I know it is far too complex.

I even have doubts about the importance of eddy resistance around the chines ... the chine boats SHOULD perform much worse .. but plenty of really fast chine boats around ... and lapstrake should probably have a similar effect too to some extent and they sail fine too.

Some idea of how to visualise flow around SAILS is hugely useful as we both know on the racecourse ... but it is a simpler case.

I was already thinking from Bolger's body of work that he shows quite well that if the boat has enough lateral plane and the sail size is generous ... then if no major mistakes are made with the hull then the thing will sail remarkably well.

This has been somewhat confirmed with the PDRacers ... where I took this to heart with big centreboard (not as big as some, but still on the big side ... but much better shaped than almost all recreational boats - AJs boat has a very nice shaped but small centreboard) and a crazily huge sail (who would have thought that the original 86 sq ft would work on a 8ft boat (I certainly didn't ... I really had expectations of taking a few photos of the big rig and then cutting it and the polytarp sail down.

Best wishes
Michael Storer

[PAR]

Michael, I've done quite of bit of "visualation" about flow, including bench, tank and model observations.

Chines have both good and bad tendencies, but all seem to be geared around the S/L ratio. At low speeds, say under 1.4 S/L, chines and runners (which in my opinion are little more then chine extensions) create a fair amount of drag, enough to warrant rounding them substantially or removal if possible. At higher speeds, the eddy making resistance is mitigated to some degree by the lift they can generate, more effective lateral area (compared to round bilge of similar volume) and their effects on laminar flow around the underwater areas and appendages. It's the effect on laminar flow that is most beneficial at higher S/L's.

This is the very reason you're seeing chines appear on the big open ocean racers in the last few generations of development. A knuckle or crease can be clearly seen in the last third of the hull. This "sheering" chine is intended to permit a clean release of the laminar flow once speeds get over, say 1.5 S/L. Yes, there is some drag associated with them, but not enough to offset the benefit of increasing speed potential by releasing the flow cleanly on a crisp, well positioned chine.

This of course flies in the face of previous, well written designers that argue drag of any sort, is to be "smoothed" in design development. This is one reason the bulb fin took so long to gain acceptance. Nat Herreshoff proved the value of the bulb keel in the late 1800's, but it wasn't until a few "hair brained" designers re-introduced it in the 1960's that new defendants could take up the discussion.

Yes, the bulb isn't as "clean" as a straight fin, but the advantage of carrying considerably more rig area, at similar angles of heel, offsets the drag loses created by the bulb. The purest "flow technicians" have real problems accepting this, but testing has bore out the facts, in spite of their best argued efforts.

I suspect these chine appendages are similar in function. At low S/L they're a hindrance, but if you have enough power to push through the resistance, then they come to shine. I also believe they have a limited point of usefulness. I don't think Paradox will achieve the S/L's necessary to cause these chine appendages to reverse their usefulness, but I could see them as a problem on faster craft.

In the end, we once again have the classic (excuse me) paradox of something working well within a specific range and vessel type, but not on other types or above or below the targeted effective ranges.

Keep on stroking it AJ, you're a man after my own heart. I do a fair amount of experimenting too. You're failure rate will be higher then your success rate, but this is the cost of finding something that really works well. Once you do find a success, the failures suddenly seem like stepping stones on the rock lined path toward success, rather then the boulders you encountered along the way.

[Boatmik]

Good observations here PAR,


In the end, we once again have the classic (excuse me) paradox of something working well within a specific range and vessel type, but not on other types or above or below the targeted effective ranges.

Keep on stroking it AJ, you're a man after my own heart. I do a fair amount of experimenting too. You're failure rate will be higher then your success rate, but this is the cost of finding something that really works well. Once you do find a success, the failures suddenly seem like stepping stones on the rock lined path toward success, rather then the boulders you encountered along the way.


Hear, Hear!!!

MIK

[b.o.a.t.]

I suppose the next test is to try deeper immersion.
4 or so heavy bodies should increase draft to about 6" or so, albeit ever so
slightly illegal, & leading to arguments about whose turn it is to drive.

So.... who is for a dunking at the next SA division meet ? :U
And when can we do it ?
I'm good for the weekend of 22-23 Nov or Sun 30th.

cheers
AJ

[PAR]

Cases of beer, preferably on ice, make wonderful ballast. From this I can personally attest, though my boat's ballast/displacement ratio seems to change substantially after a long day's sail. The trials, burden and difficulties of experimentation . . .

[Boatmik]

And Paul, Some of the methods of moving such ballast to the windward side have advantages and disadvantages.

MIK

[b.o.a.t.]

Cases of beer, preferably on ice, make wonderful ballast. From this I can personally attest, though my boat's ballast/displacement ratio seems to change substantially after a long day's sail. The trials, burden and difficulties of experimentation . . .


Not sure I'd be willing to risk something as valuable as beer as ballast during
testing. It might fall out & sink in event of capsize.
Or worse, fail to fall out & sink whilst still in the boat.
Same caveat applies to sandbags.

I figure live ballast would have the good sense to exit at an appropriate time,
& probably not require the services of a diver to recover.

[PAR]

This is why the conscientious experimenter keeps their ballast in a well insulated floating cooler. No need to jeopardize the lives of the ballast, in haphazard or ill planned endeavors, it's just not right. If the cooler has a lanyard, it could save an unexpecting crew from drowning, possible acting as additional floatation in the event of a swamping or capsize. In general the usually bright colors of these coolers, could be seen by the rescue ship sent to pull your soggy butt out of the drink, if all goes down hill.

You shouldn't discount the true value of well chilled beer in a brightly painted cooler. I'd rather float to shore, clinging to one of these then any PFD I've ever seen. Besides, if you have to drown, proving a new, hair brained boat idea, wouldn't you rather be good and drunk when the end actually comes?

[Clarkey]

I finally found a decent drawing of another boat that uses its rudder for basically all lateral resistance. As I mentioned before I am pretty sure that Paradox goes quite a long way down this road.

I actually got a go in one of these a couple of years ago and they go quite well to windward - tricky to tack though, you usually have to push the boom out and back the main to bring the head round. Felt really quick on a reach, considering it is basically a marine pick-up truck (or 'Ute' here I suppose!).

Chris

[b.o.a.t.]

Besides, if you have to drown, proving a new, hair brained boat idea, wouldn't you rather be good and drunk when the end actually comes?


I intend to be conspicuous by my absence from my demise.
Or at least, that's Plan A.
Still working on Plan B.

As for the coolers, I estimate that I only have stowage room for about 120KG of home-brew bottles.
And only about 40kg of cooler stowage.
I am reluctant to place the other 80kg at such dire risk.
In any event, 120kg is far short of the 300-400kg I calculate needed to drop Teal to a reasonable depth to test the winglets properly.
I also doubt I could trust the other 200kg or so with the 120kg.

:U

AJ

[Boatmik]

Hey Clarkey,

I know what you mean of finding pics that reflect this feature.

Whenever the sail area is well back in the boat you can have some inkling that the rudder is carrying a lot of the lateral load. (In a land with WAAAAY too many palm trees)

http://www.africanclassicencounters.com/images/general/dhow-big.jpg

Or a more modern variation - they found it was faster to lean the rig back ... the boom was designed to be horizontal ...


Interesting what you say about the boat in your image that you found hard to tack. It is exactly my experience of the Bolger Cartopper.

I can sail anything, backwards, forwards, sideways ... but I found it tricky to tack because is uses the same trick to make the centreboard small and move it well forward carrying most of the load on the big rudder.

http://www.instantboats.com/images/cartopperstudyb.gif

It is an interesting idea, but seems to work better with heavier boats. That cockpit of the Cartopper is real nice though.

Michael

[PAR]

Actually, looking at where the CLP would be, including the rudder, it shows there's not much lead or possibly reversed lead (that Gozzo or whatever it is in the sail plan above), so I'd imagine it would be a bear in stays without something to pivot on.

I had the fortune to sail a tandem board cruiser some years ago. The boat above looks as if it could benefit from some sort of small "trimming" board, so it could tack. By adjusting the tandem boards, you could remove the rudder and sail along merrily without it. I remember playing with the boards, literally reducing the pressure on the helm to nothing and steering with the sails and board trim. This was a 40' cruiser so crew placement to steer wasn't an option.

I've sailed the Cartopper too and had to fall off a fair way to gain momentum to tack, then be confident about helm position so as to not kill drive through the eye. I found it an easy boat to "over sail" and never liked it much. I've repeatedly discovered that a boat that tacks, well is one that carries a healthy lead. I think you have to encourage a boat's natural tendency to round in plans development, if you want crisp maneuvering ability.

[Clarkey]

Centreboards or leeboards are almost completely unused in the upper adriatic except in very small boats. Everything from 6m to 25m in length sails just on the rudder.

Most of the boats use a what is effectively a 'forwards mizzen' (see pic) or a low aspect ratio jib to throw the head round (other pic). I should credit the pics to the Circolo Velico Casanova who have an epic flickr photostream here:

http://www.flickr.com/photos/17001721@N08/page8/

(organised into easier sections here - http://www.flickr.com/photos/17001721@N08/sets/)

Sailing the boats is strange, I expect the Cartopper is similar. The weather helm is quite meaty but never becomes really excessive, even on a reach. When you go to tack the boat flies up into the wind so fast you just can't believe that it won't go all the way round - then it stops dead in irons until you back the main (mainsail only) or the jib/mizzenesque thing. Absolutely impeccable manners when you are gybing though.

You can see that they set their lugsails very nicely and their hull forms are pretty sweet too.

Chris

[keyhavenpotter]

This picture of Matt's Enigma shows just how far back the rig is carried, the very big rudder obviously providing a lot of the resistance to leeway.
http://farm4.static.flickr.com/3280/3059378908_63d4cd52d7.jpg?v=0

Brian

[b.o.a.t.]

Another, larger Enigma hits the water. http://e460.blogspot.com/


Interesting quote from Matt Laydon building the original Enigma
http://physics.bgsu.edu/~layden/FunStuff/Boats/Matt_Boat/2005-05-22.htm

2005 May 22
"Here are a few photos of some of the less exciting details that always need to be taken care of along the way. A note to the uninitiated: The chine runners, or winglets, are small horizontally protruding fins at the chines amidship, that help the hull function as a 'lifting body' to resist leeway. A centerboard or other retractible vertical fin would do the job better, but I have a mental allergy to moving parts and complication. The runners are easy to build and they protect the hull rather than weakening it as a board does. They take up no space in the interior, always an issue in a small cruiser."

cheers
AJ

[b.o.a.t.]

More information from The Man Himself.
Interview with Matt Layden in the May/June issue of Small Craft Advisor
partly reproduced at Sven Yrvind's site.
http://www.yrvind.com/present_project.html

Combination of lifting body hull shape & large rudder.
Teal isn't deep enough to do the lifting body thing well.
However, the winglets -do- augment the daggerboard appreciably, so I'm happy with them.
cheers
AJ

[Boatmik]

Yap ...

Still a problem with the separation of the effects. Most traditional boats are "lifting bodies too", or a NA would probably talk about salient lateral area.

You need that lateral plane one way or another. I still find it hard to believe that a little lip can make so much difference and still suspect that if it wasn't there it would make little difference.

It does mean that the method only really works for heavy boats.

Norfolk Wherries - had no visible keel but had to sail upwind up rivers .. they were well regarded as upwind boats.
http://farm1.static.flickr.com/203/494698163_045a83ad61.jpg

Plank on edge cutters, pilot cutters. Also why you factor in the hull depth when you calculate the Centre of effort of heavier boats. No lip to be seen.

Best wishes
MIK

[Boatmik]

As some of you know I am staying with Chuck and Sandra of Duckworks in Texas.

I was having a look through some back issues of Small Craft Adviser and found an interview with Matt Leyden.

(ha ... just realised that AJ's link above was to the same article)

I wanted to add some to this thread.

He says the bilge runners are the most obvious and also the least important part of his system. What I read makes lots of sense.

1/ It is suitable for boats that are quite deeply laden - heavy for their length. A large part of the lateral resistance is from the depth of the hull. It won't work with shallow, lightly laden vessels. Think very tradtitional boats before the keel became an appendage and garboards became hollow.

2/ The mast and sail are set well aft and the rudder is large. This means that the boat will have an amount of weather helm that will be corrected by the rudder at all times. This means the rudder which is large and deep will be at a greater angle of attack and provide a large part of the lateral resistance. Hobie cats do this too (the ones without centreboards) the more you rake the rig aft, the more load is carried by the rudders which are much more efficient at carrying side load than the hull.
http://www.hobiecat.com/sailing/images/hobie16/gallery_06_lr.jpg

3/ the chine runner is the least important component and won't work independently of the other two. It is an attempt to reduce the crossflow slightly and increase the effectiveness of having a deep hull in the water. In a couple of the photos one of his more rounded hullshapes seems to have the chine runner at a slight angle to the way the water would naturally run over the hull. I think you would have to be very careful how you used this and Matt has chosen quite a small angle (I think).

Best wishes

MIK

[PAR]

These are pretty much the same conclusions you and I came up with, when this thread was active Michael. See, we're not as dumb, as our women attempt to convince us of.