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Stephane blanchette
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-------- Message d'origine --------
De : "Bernd@... [k-designs]"
Date : 17-12-06 17:54 (GMT-05:00)
? : k-designs@...
Objet : Re: [k-designs] Re: Leeboards
?
Hi Andrew
All the best with your broken leg and I wish you a quick recovery.
Yes it is an intersting conversation with a bitter by taste for me. Clear is, the anti vortex panels need more research, because the work. Sure for bigger boats with more draft. I was so to hear to optimistic to have them as a standard for a smaller boat
as the KD 860 is. Intersting is, that I have had only one more complaint. As you mentioned the builders lenghtened the boats for better or worse I do not know, I know only that for a selbouw project many boats are sailing. For strength, the are strong. ?we
tok the boat out the ijce by - 15 degree and nothing broke. The shape also of the panels is clearly shown on one of my pictures in my album.?
Good, I was thinking to for a solution with boards. Thank you for your information and throughts why you did it the way you decribe. Thank you for that, it is very helpful for me. The facts you descripe, give me the security that I am also on a more satisfactory
track. Dimensions, place of the board in respect to CE of the sails and the center of pressure.
It is a relativ small boat (today) and I had to find a solution without loosing inside space, I made a time ago already some sketches and drawings from a rotating dagger board mounted at the center line under the bridge deck. Some other designers use these
solution to (see photo). The board will not ventilate when it is set 3 to 4¡ã forward. Extra weight 24 kg of the daggerboard pod 22kg. Besides the construction of the daggerboard (also a NACA 0010 section) all drawings are ready. Construction like all my boards
and rudders. The easiest and quickest way to build ?such a thing. The bridge deck stringers can be ommittet and some weight gained here. Not in the cockpit area of course.The board is set with a rope from the cockpit. The board is hold down with an other rope
which can be set at an self releasing cam cleat. Interested KD builders/owners can have the drawings already. Trop me a private mail and I send the to you.
Again all the best for you Andrew and thanl you very much
See for pictures my album
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Hi Andrew
All the best with your broken leg and I wish you a quick recovery.
Yes it is an intersting conversation with a bitter by taste for me. Clear is, the anti vortex panels need more research, because the work. Sure for bigger boats with more draft. I was so to hear to optimistic to have them as a standard for a smaller boat as the KD 860 is. Intersting is, that I have had only one more complaint. As you mentioned the builders lenghtened the boats for better or worse I do not know, I know only that for a selbouw project many boats are sailing. For strength, the are strong. ?we tok the boat out the ijce by - 15 degree and nothing broke. The shape also of the panels is clearly shown on one of my pictures in my album.? Good, I was thinking to for a solution with boards. Thank you for your information and throughts why you did it the way you decribe. Thank you for that, it is very helpful for me. The facts you descripe, give me the security that I am also on a more satisfactory track. Dimensions, place of the board in respect to CE of the sails and the center of pressure. It is a relativ small boat (today) and I had to find a solution without loosing inside space, I made a time ago already some sketches and drawings from a rotating dagger board mounted at the center line under the bridge deck. Some other designers use these solution to (see photo). The board will not ventilate when it is set 3 to 4¡ã forward. Extra weight 24 kg of the daggerboard pod 22kg. Besides the construction of the daggerboard (also a NACA 0010 section) all drawings are ready. Construction like all my boards and rudders. The easiest and quickest way to build ?such a thing. The bridge deck stringers can be ommittet and some weight gained here. Not in the cockpit area of course.The board is set with a rope from the cockpit. The board is hold down with an other rope which can be set at an self releasing cam cleat. Interested KD builders/owners can have the drawings already. Trop me a private mail and I send the to you.
Again all the best for you Andrew and thanl you very much
See for pictures my album
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Hello
It's been interesting to follow this communication and nice to see
that there is good conversation although everyone doesn't share the same
opinion. Thank you all for the contribution! Great to hear your
experience Andrew, I look forward to see pictures of your daggerboard
solution. Hope your leg will be OK.
I'm one on those KD 860 builders -have been quite a while (seven
years, 1250 hours).? My anti-vortex plates are ready to install. I
really would like to see them work properly specially in shallow
archipelago here in Finland. I was considering luffboards after Bernd's
plans here in the forum, but it would be quite a hassle to alternate
luffboards in tacks in not-so-open seas. It came to mind that I could
build both anti-vortex panels and single daggerboard. I could use
daggerboard when I'm sure there's water and lift board up when unsure.
Does this make any sense?
By the way, last thing I built before winter was pivoting motor pod for single outboard.
Best regards,
Pete
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Hi Bernd. We certainly have gone the long way about this. However it looks like there are some positive outcomes here, which after all is the point of the forum. ?It would be good to here from other builders of the KD860 about there experiences as well. This is part of the reason that I have not replied at length on this subject until Know. I posted a few comments about my daggerboard modification a couple of years ago just after I did it, and did not go into great detail, just to put it out there that I experienced some problems with leeway prevention and this was the solution that I came up with that seams to work well, As I did not want to start a slinging match or alarm other builders etc. But put forward a solution incase others were having a similar problem. Also I did not want go into great detail as I am an only an amateur boat builder and am not qualified to advise others about design and structural changes to there boats. The other part of the argument is that most of the KD860's out there sailing have been modified extensively and maybe the lengthened versions have had success with the AV panels, some don't use them at all, some owners like most yacht owners these days may motor more than they sail. I just don't know for sure what others have experienced, and it seams like there is insufficient feedback to right off the concept of AV panels. ? Now back to the original question. I have dug out some scraps of paper with some basic dimensions on it for what I built. Unfortunately most of it was?in my head. I will explain in detail here my decision making process for the benefit of other interested members rather than Bernd, who obviously this is all pretty basic.
So I put the board in the port hull as this hull had less weight in it, as the galley and food are in the starboard hull. I used an 0010 profile as to my understanding that 8 - 10 % of cord is a good rule of thumb for daggerboards ( angle of attack is not greet and obviously, thiner generally means less drag) and 10% being at the thicker end of the spectrum means I did not need to use exotic materials to gain adequate strength. The board is 2.6m X 600mm.?When fully lowered that gives 1m of bury inside the boat and 1.6m sticking out to give a 2m draft. so thats 0.96m2 of projected area with an aspect ratio of around 2.66:1. I think this relates to 2.25% of projected working sail area (for my boat). But also a fairly conservative foil (low cost). ?The casing goes through the berth base and the head of the board goes down into the case to be supported by the berth base for sheer load. In this way the board could be 900mm shorter (less weight, windage when up, and cost). I think the CLR is about 4% of waterline length forward of the COE ( to allow to some degree the moving forward of the COE especially when using the code 0 / screecher. I had to angle the case back a bit to fit it in the boat. So the CLR will move forward a bit as the board is retracted. I would have liked to get the case in vertical in both directions but had to work around the interior to get the best compromise. I made both ends of the board the same in relation to angle of exit at hull, so If I damage one end, I can turn it around and use the other ( this is not a 5 minute job, but is doable).? one big advantage of having the case on the inside of the hull is that I can use the main halyard to pull it out for maintenance, with some element of control. As far as board area and aspect ratio goes, I had to reverse engineer around what size case I could fit in the boat and cost to build a dagger board if going for higher aspect ratio (having to use carbon fibre$$) but a smaller case etc, and stay within proven parameters. So I could assume that using the small rig, a smaller board could be used, and those that don't sail in light winds, could get away with something smaller as well. Also foil profile and aspect ratio effect things as well. So I made an educated guess which works well for me, but obviously Bernd has the experience and knowledge to come up with something more refined. It is totally possible to put a smaller daggerboard in each hull (outward facing) without affecting the interior, As my case does reduce the size of the berth a bit.
All the options have merit and as usual it comes down to the boring old practical considerations. so a bit long winded, but I hope is of some use.
I will take some photo's (which might make more sense) of my boat when I can get out to it, as I need assistance at the moment, as I am recovering from a broken leg /ankle and can't walk. Hence the large amount of spare time I have to post on the forum, which I do not normally have. °ä³ó±ð±ð°ù²õ¡´¡²Ô»å°ù±ð·É.
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Howard
If you are not looking to build, and still like a catamaran, you can try finding an EDELCAT28 or 33 or an Iroquis32. The later can be found in Florida no issue, and the EDELCAT in europe and caribbean. These are old boats but will save your budget and are somewhat fast. An old macgregor 32 or a gougeon32 is also another choice but these are not too rugged
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From the JRA website, I found this comment from an anonymous
member:
I think Pete just likes building boats.?
He told me last year that he was very happy with Oryx
but that he was interested in building at least one more
boat.? It will be interesting to see what it turns out to be.
?????????????????????????????????? H.W.
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Andrew:??? I read eagerly, expecting to find some clue in this as to your solution to the problem.............? You mentioned all the things you had considered, but never got around to saying what you actually did........... I can only conclude that you sold the boat and bought or built something else, or are considering it.??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? H.W.
Howard.? The latter part of this conversation seams clear to me? Or are my reading skills letting me down again.?
Have you actually spoken to Pete Hill about his boat? How do you know that he is not satisfied with it's performance? The fact that Oryx has sailed thousands of miles safely, suggests to me it is a total success. And I am sure Oryx will find a new owner that will put many more miles on her, in a safe and enjoyable manner. Andrew.
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Hello Andrew
Now I understand your frustation. A pity that you did not contact me earlier. In the course of this sometimes heaty discussion I learned a lot. There must be first a sufficient big enough underwater ship (area) to make the AV panels effective. Clearly, with a draft of only 0,4m and a length of 8,5m and the longidutional shape of the hull the area is to small to make AV panels effective. Your boat is doing now what a boat has to do, sail to your sadisfaction. Sorry for your extra work. We discussed, and I have more solutions to remedy this as was mentioned in some of the letters. Personal, I would use the luff boards which can be mounted afterwards without intervering with the interiour, or for some LAR keels could be a solution. That the do not work very effective is in the nature of the beast (hydrodynamic efficiency of a low aspect ratio). So the solution with one daggerboard works well as you state and I will adapt them as standard for the future boats. I will use the Great Barrier system from Tennant to lower them and get them up. In this way the boards are not to long and can be handled without a lot of sheaves and ropes. So I will hole you now; on which side did you mount the case? I think that it is on the port side against BH 3. ? how big is your board? I calculated for a board with the size of 420x2470mm, 12% corde section. The walk through the toilet compartment is a bit restricted but in my view the best solution. If you like, please answer and tell me your solution and what you think about mine. By the way the drawings for this solutions are ready, if Andrew has more or less the same solution, owners of the KD 860 plans can order them. But please per my normal email address
Cheers
Bernd
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Bernd:
??? I'd like to read that report.?? I'm not familiar with JSB....
Was that a typo for JRA??? Until now I could only speculate based
on what I knew.? The fact that he abandoned his original rig that
was very loosely based on Paul McKay's Aerojunk, and went to soft
wing sails, and then abandoned them, and went to a rig much closer
to Paul's Aerojunk, told me that he was not satisfied with the
performance.? Of course his very short masts can only accomplish
so much, and he was presumably trying to get the most out of what
he had.?? I also knew that he had gone to the LAR keels, and that
the AV panels simply did not work for him.?? One fell off and
according to him made no difference.? Pete writes very little,
both Annie and Carley were prolific writers, and I've enjoyed
reading Annie's books, and Carley's blog, which unfortunately read
mostly like a travelogue, lacking the technical details I was
interested in.
??? The LAR keels significantly increase draft (as a percentage),
but also have the advantage of protecting the hull bottoms, making
beaching the boat a bit more comforting, as you aren't wearing
away important materials.?? The increase from 40 cm to 91.5 cm is
a pretty significant increase in draft.? I'm the sort of guy that
spends too much time thinking about things perhaps......??
perhaps.????? If one is using an LAR keel, it makes sense to me
that it be designed in such a way that it increases the effective
aspect ratio at the same time as it increases draft.? An
engineered rudder or foil or luff board is far more effective than
a simple plank.? The LAR keel, as it's increasing wetted area /
drag, and costing draft, perhaps could benefit from some real
engineering, rendering it both smaller and more effective.??
???????????????????????????????????????????????? Howard
On 12/04/2017 09:50 AM, Bernd@... [k-designs] wrote:
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Hello Howard
So at least I know now your name. This discussion was
sometimes a bit to heaty . Why Pete is selling the ORYX
has nothing to do with the performance of the boat.
Because he made a sort of report at the JSB where it was
clear he was content with the performance. Clare could
be the reason and I would understand. During there
journay Clare and I had many contact over emails. She
was a special person.
Back to boats and in special the KD 860. I learned a
lot, sometimes between the lines why the AV panels work
not on this design but on bigger ones. It has to do with
the draft of the boats (also the aspect ratio). These
panels are an old idea from around 1980. The idea in
princip is from Paul van Denen and he made some ?sort AV
panels and the worked on his Wharram Tangaroa (same
length a the KD 860). The boat saiked much better to
windward. ?As you know the boat with his V hull has a
big draft.
From Andrew and someb ody who is also not in these
group, I heard the same complaint, otheres where happy
with the panels. I had the feeling for a long time that
Andrew was not happy with the performance of the boat,
but he never explained why. The discussion you started
got him out his corner to tell why. So I am very
grateful to start these discussion.?
Cheers
Bernd
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Hello Howard
So at least I know now your name. This discussion was sometimes a bit to heaty . Why Pete is selling the ORYX has nothing to do with the performance of the boat. Because he made a sort of report at the JSB where it was clear he was content with the performance. Clare could be the reason and I would understand. During there journay Clare and I had many contact over emails. She was a special person. Back to boats and in special the KD 860. I learned a lot, sometimes between the lines why the AV panels work not on this design but on bigger ones. It has to do with the draft of the boats (also the aspect ratio). These panels are an old idea from around 1980. The idea in princip is from Paul van Denen and he made some ?sort AV panels and the worked on his Wharram Tangaroa (same length a the KD 860). The boat saiked much better to windward. ?As you know the boat with his V hull has a big draft. From Andrew and somebody who is also not in these group, I heard the same complaint, otheres where happy with the panels. I had the feeling for a long time that Andrew was not happy with the performance of the boat, but he never explained why. The discussion you started got him out his corner to tell why. So I am very grateful to start these discussion.?
Cheers
Bernd
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Andrew:
??? It was my intent to simply drop this, as my poor communication
skills seem to have created some ill will here.?? I don't recall
suggesting that you had sold your boat or sold it because of the
AV panel issue, and reading back over my sent posts, I don't see
anything to that effect.??? Where that came from I don't know, nor
did I make any suggestion (as you kindly pointed out), that Bernd
had sold Pelican for that reason.
??? I did........ and shouldn't have suggested that I suspected
that it was at least part of why Pete is selling Oryx, but also
that losing Carly off South Africa from Oryx, left it a boat full
of memories, and that Pete likes to build boats.? He built Badger,
and I think China Moon, and of course Oryx.? What is clear from
the three different biplane rigs he has had on Oryx, is that he is
not entirely satisfied with the performance of that boat as he
built it.??
??? Again, the key is probably in the sharp corner which Bernd
emphasizes in his writing about the AV panels where he speaks of
adding material AFTER sanding so that he can get rid of the small
radius that naturally occurs.??? I haven't seen the plans, but
from what you wrote it sounds like this is not emphasized enough,
and should probably be an addendum........ assuming it is the
cause of your problem with leeway &c.??
??? To me the KD 860 and it's stretched cousins (of which there at
least two I know of), is the outstanding design of cats in that
size range? for a number of reasons.? An innovative design where
the right design choices were made for the right reasons.??
Weather or not the AV panels work as they are supposed to would
not change that a lot for me.??
??? Resolving the issue would AV panel issue is important, not
because it is a make or break feature, but because innovative
technology like this often ends up in the dustbin of history
because "it doesn't work", when in fact it actually does
work...... at least on Pellican, and presumably on some KD 860's.?
If the difference between success and failure of these rests on a
small radius left from sanding, then that is something relatively
easily corrected during construction, and not so difficult even
after the boat has been in the water.?? I would love to see this
feature copied...... successfully, by other designers.?
???? The luffboard system as Bernd designed it, offers an
excellent retrofit with minimal impact on anything, with the
advantage of folding back if it strikes something...... like a
centerboard.? It also doesn't require a case built into the
interior of the hull like a centerboard or dagger board, or reduce
draft like an LAR keel.? If I were building a KD 860, I'd probably
incorporate these from the outset, as there are probably
circumstances even with the AV panels working, where they would be
beneficial.
??? The truth is, that I don't intend to build an 860, or any
other cruising boat.? Having built boats before (smaller), I have
a good idea of how much work is involved and how much
time......... and cost, and at 62, I want to spend my time
sailing, not building while I have my health.??? I would love to
own one though, but I doubt I will find one in a price range I can
afford without breaking my cruising budget, and it remains at the
very top of my list of Cats I'd like to own.
??? I apologize again for creating ill will and
misunderstanding....... it was not my intent.
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
??? ??? ??? ??? ??? ??? ??? Howard
On 12/03/2017 04:59 PM, andrewklees@... [k-designs]
wrote:
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Hi Bernd.
Just to clarify. HW implied that I sold my boat (which I
have not) because of the AV panels, not your boat! He also
implied that is the reason that Pete Hill has his boat for
sale.
The rig on my boat is the bigger rig as per the plans.
There is nothing in my plans that suggests that the AV
panels neaded to be in a different postion when useing the
large rig.
MY mainsail is very conservative and is about 30m2 as
oposed the 36m2 on the plans and has 3 reef points of 20%
of luff lenght each. The jib is 14m2 same size as plans. I
also have a smaller jib of about 10m2 for high winds.
I sailed the boat for about 6 months with the AV panels,
and not just day sailed, went sailing for weeks at a time.
I used every sail combination eg. full main and big jib,
full main little jib, 1st reef in main with both jib
combinations, 2nd reef and small jib, main only, jib only.
Made virtualy no difference to leeway and weather helm. At
this stage I was satisfied that there was no glimer of
hope with the AV panels and I had to find another
solution.
Going for a single dagger board was the solution that
suited me best not the only solution.
After installing the daggerboard, it was like sailing a
different boat. The helm is neutral all the time and you
can let go of the tiller and nothing happens. Upwind
performance is as good or better than most other cruising
boats, which is good enough for me. Boat tacks buitifully
and very occasionally gets stuck in irons which is always
my fault not the boats ( tired or distracted). Motoring in
windy conditions and or tight turning is a massive
improvement.
Interestingly sail combination makes no difference to the
helm balance or leeway at all with the dagger board. I can
sail on the wind ( may be 50deg) with the code 0 (40+ M2
SAIL) and full main with a totaly neutral helm and 13+ kn
boat speed.
In short the boat whent from one that could not sail
itself out of a wet paper bag, to a greet little sailer
after a relatively small modification.
Having to install a daggerboard was not a disapointment at
all for me, and I thoroughly enjoyed the exercise and
learnt a lot. I am also glad that I gave the Av panels a
go.
I agree that the theory for the AV panels is sound and
would have like to have continued to experiment with them,
but just wanted to get some quality sailing in. Also
around this time I unexpectedly became a parent, and
therefore time and funds became limited.
I certainly don't mean any disrespect, my experience with
the AV is definately not a decisive test. All I can say to
others is the AV panels are easy to build and also easy to
cut off, so give them a try and tell us how you fair. In
relation to the exercise of building a boat, the AV panel
issue is a fairly trivial one.
Cheers.......Andrew.
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I thank you for raising this topic. And I would also like to note the importance of clarifying these issues for the plans.
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Hi Bernd.
Just to clarify. HW implied that I sold my boat (which I have not) because of the AV panels, not your boat! He also implied that is the reason that Pete Hill has his boat for sale.
The rig on my boat is the bigger rig as per the plans. There is nothing in my plans that suggests that the AV panels neaded to be in a different postion when useing the large rig.
MY mainsail is very conservative and is about 30m2 as oposed the 36m2 on the plans and has 3 reef points of 20% of luff lenght each. The jib is 14m2 same size as plans. I also have a smaller jib of about 10m2 for high winds.
I sailed the boat for about 6 months with the AV panels, and not just day sailed, went sailing for weeks at a time. I used every sail combination eg. full main and big jib, full main little jib, 1st reef in main with both jib combinations, 2nd reef and small jib, main only, jib only. Made virtualy no difference to leeway and weather helm. At this stage I was satisfied that there was no glimer of hope with the AV panels and I had to find another solution.
Going for a single dagger board was the solution that suited me best not the only solution.
After installing the daggerboard, it was like sailing a different boat. The helm is neutral all the time and you can let go of the tiller and nothing happens. Upwind performance is as good or better than most other cruising boats, which is good enough for me. Boat tacks buitifully and very occasionally gets stuck in irons which is always my fault not the boats ( tired or distracted). Motoring in windy conditions and or tight turning is a massive improvement.
Interestingly sail combination makes no difference to the helm balance or leeway at all with the dagger board. I can sail on the wind ( may be 50deg) with the code 0 (40+ M2 SAIL) and full main with a totaly neutral helm and 13+ kn boat speed.
In short the boat whent from one that could not sail itself out of a wet paper bag, to a greet little sailer after a relatively small modification.
Having to install a daggerboard was not a disapointment at all for me, and I thoroughly enjoyed the exercise and learnt a lot. I am also glad that I gave the Av panels a go.
I agree that the theory for the AV panels is sound and would have like to have continued to experiment with them, but just wanted to get some quality sailing in. Also around this time I unexpectedly became a parent, and therefore time and funds became limited.
I certainly don't mean any disrespect, my experience with the AV is definately not a decisive test. All I can say to others is the AV panels are easy to build and also easy to cut off, so give them a try and tell us how you fair. In relation to the exercise of building a boat, the AV panel issue is a fairly trivial one.
Cheers.......Andrew.
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Hi
Andrew and HW
My
answer was a bit harsh, because you implied that I sold the Pelican
because the anti vortex panels do not work. I have no reason to
belief you that the a-vortex panels do not work on your boat, why
should I.
It
would be necessary to make more research to get them working on
smaller boats as the Pelican. Of course I was thinking about it. HW
had a good argument with the aspect ration. My through about it is
that the underwater area in general is much smaller as on the
Pelican and the aspect ratio ?(draft KD 860 0,4m draft Pelican
0,64m) ?Waves will affect the water to air boundary less on a
bigger boat. So the UW area is better maintained on the bigger boat
and the panels have a better effect.?
By
the way, I sharp corners at the chine in trapezoidal and sharpie
hulls work in any case to lessen water resistance. I lost the photos
from a water test for big ships (it was for a tanker) As you will
know modern big ships are nothing else for a big part as sharpies
with rounded off chines. And to every bodies surprise there where
parts on a given speed the water was flowing backwards. There is
still a lot to learn.?
Andrew
you have as I can see a bigger rig and special mainsail. Then the
a-vortex panel is anyway to far forward because the CE of the sails
will be further back. This is the reason you have weathermen.
Extreme leeway same explanation.?
Shortening
the main sail. The center of effort will, which ever mainsail shape
move forward. So with ever board there will be a mismatch. I agree,
with a dagger board less. When you have only one there will be a
difference how good the boat sails to windward. Is a simple
triangulation and drawn on a piece of paper. The least effect is
with LAR's, because of the longitudinal size. Dagger board or
folding boards (lee board, or luff boards). make in the end no big
difference. Only with luff boards the boat ?gets as advantage
more stability. 1. with a board on the lee the boat can trip and as
mentioned lessens the stability of the boat.2. my luff boards start
with an angle of 4 degree or more forward. At this moment you have
some control over the CE. Precis has shown that sea going "Hoogaars"
an old Dutch fishing boat design, had never this problem when the
sail had to be shortened, also when the where partly turned back.
You are right that outside foils can have capitation and
ventilation. When turned 4 ¡ã forward the ventilation and capitation
is diminished. Can be compensated by making them a bit longer
anyway. For ?some of my designs I come back to an old idea,
having on board on the center line in a sort of pod.?
It
is a pity that many owners of the KD 860 which are sailing, special
from Hungary, Brazil, Argentina, Russia and ?so one do not
speak or write English and are no members of this group, to give
there opinion.
For
persons, where the draft is not a big problem, I have a drawing from
years ago for a LAR keel. Builders of the KD 860 which are insecure
now, drop me a letter and I send you the drawing. I have also as
draft, drawings for luff boards it is up to you.
At
last, I hope Andrew that you have still fun with your boat
Cheers
HW.
?I think that we can postpone for the time being our
discussion and wish you all the best.
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About dagger boards versus alternatives: It is my observation from my own experience that the superiority of dagger boards is true. It is a fact that of the catamarans in the racing multihull fleet here in Auckland New Zealand, all have deep twin dagger boards.
That is not to detract from approaching the issue from a point of view of practicality: lots of cruising cats have one dagger board. The? vast majority have LAR keels which do not work as well but are practical, easily maintained, not so prone to damage etc. I put the AV panels into this category. As to why they seem to work better on some boats eg Pelican vs KD860, that is beyond my level of knowledge except to say what I originally maintained: dagger boards give the best performance, but if simplicity is the most important factor, then these other systems are probably adequate.
About asymmetric hulls: yes Bernd, as a former Hobie cat sailor I know about keeping the leeward hull down. In fact I cringe when I see people sitting on a Hobie in light winds , not moving, with the windward hull deep in the water.
I am a strong fan of? asymmetric hulls, especially now with the Duo480 Jigsaw. Perhaps it is also the biplane rig helping, but the upwind performance of this boat has surprised me a bit. Rodney's KD650 Sparta was very good upwind also.
regards Bryan
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Andrew and Brian
Shuttleworth is only partly right. And we have had many discussions thogeter years ago. From the effect of the board to windard performance he is right. Only when the board is on the lee side the stability of the boat is less. Because the center of lateral resistance goes lower and the levrage to turn the boat over greater, an earier capsice can occure. Logical, this effect is less pronounced on big catamarans. By the way, we where sailing "against" a Spectra on the Mare Menot. Our Pelican with the antivortex panels was sailing at the same height to windward as the Spectra to the amacement of my self and the sailors on the Spectra. We where of course slower. The Spectra is for some meters longer, I do not know how many.
Brian you are right, the a-symmetrical hulls need some speed to work. A trick, sit on the lee side to get the lee hull deeper in the water as the windward hull and the windward performance gets better. An old Hobi 14 and 16 trick. As you observed well, antivortex panels can conly work when the boat as speed.
Cheers
Bernd? ?
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Re: Eco 5.5 Sailing Version
Congratulation Hanish
Looks great on the water as expected. Now the mast setting. The biggest problem is when the mast will swing to the one or other side. In the Netherlands some ?mount the mainstay parllel and at the height of the mast step. But with the stay as is normal on catamarans so far back this would not help. Only solution which comes quick to my mind is. Use a two ropes which lay good in your hands to grip. Fasten each rope with a sliding knot to the stays. When you setting the mast have the two ropes also in your hand. In this way you can control the sway. Not perfect, but better as nothing. I had a smile on my face with your remark about the rudder control. Is always disappointing when you come from monohull sailing. A sweap at the helm and the mono reacts direct. Think you drive your car. Gentle tiller movement will do it. Not over about 45 degree. Then the rudders stall and work only as breaks. The outboard motor has the power and the fairing which is also almost a rudder. Make a single sided connection to the rudders, makes all the difference. On the weight as you mention, nothing to do. Keep her light loaded. Have fun and keep us informed.
Cheers
Bernd
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Re: Eco 5.5 Sailing Version
Congratulations Hamish on the launch of your boat.
Obviously you will be up and away sailing over the summer holidays, great news.
You mentioned the stability of the boat when you stepped on board. This was the first thing I noticed with my boat, even though it is smaller and has substantially less buoyancy than the Eco.
Hope to hear sailing reports soon.?
PS you mentioned about the boat moving around as it came off the last little bit off the trailer into the water. That is why I mentioned bolt on guides of some sort. Maybe even removable things.? When you launch and retrieve in cross winds it can be noticeable. Anyhow, best of luck with the next stage
regards Bryan
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Re: Eco 5.5 Sailing Version
Congrats?Hamish!
Your boat looks really nice in its natural environment! Enjoy the sailing season!
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Bernd Kohler
Robert Twiss