Here it is the Endeavour with a 3.5cm deeper keel :
…
…
Of course all the relevant shadows to scale 1 :1 shall be redrawn
As can be seen, the displacement increased 5059cm3 (+ 610cm3). This increase is actually split between the ballast and the construction.
The Ballast volume and shape still to be drawn.
ClaudioD
Hi RGb,
it is not excluded that I will be drawing one like you says, but when … !!!
Here below a drat of 208mm
It may help the righting moment, but the counterpart is a large increase of wet area. A compromise is necessary and for the time being I stick to what I have already done.
This do not exclude of course that you copy one of my drawing and retrace it yourself !
This is what would look like :
…
Cheers
ClaudioD
Another try comparing two side views :
…
I need to recalculate the option with a deeper keel. Also the bow is raised a bit.
Is a complete new design and as such require extra care at shadows level.
Calculations also needed for the wet area, the obvious increase may severely jeopardize the overall performances
ClaudioD
Claudio,
While I certainly can’t disagree about the increase in wetted surface area having an adverse effect on performance, does that not only really apply in light winds? It could also have an impact on acceleration in moderate to heavy winds but if the increase in wetted area results in a far superior righting moment can we not just say that her ideal conditions are more towards the upper wind range?
I’m well aware that your knowledge far exceeds mine - maybe the gains in righting moment just aren’t worth it - but I certainly look forward to seeing what sort of numbers you’re going to come up with for the modified hull of ‘Endeavour ll’.
Just thinking out loud really, over to you!
Cheers,
Row
Claudio
do you have to go 206 deep?
I have been looking at the canterbury J… and they went 160. My J i drew went 160…I know the 140-160 is not a big change. but it would still be an improvement…and you would get alittle more righting movement… with the less wetted surface?
Hi Row,
as you know as well : higher wet area = higher drag
Of course when the “wind power” is low the boat will have more difficulties to move. At any wind power, the wet area drag will be there anyhow to reduce performances when compared to other possible solutions I’m thinking about.
While performances ? when racing this aspect is the most wanted, of course not all modelers think in therms of “racing”
For me “righting moment” is needed to avoid to change sail every 2 knots of wind increase.
The rule of thumb says : when the boat heeling is over 30°-35° for more the 10", then is better to change Rig. This is valid when racing, but for me is a parameter that count. For a racing model is counting twice !
My intent is thus to keep the “Rig A” as long as “reasonable” … what mean reasonable ?
This is my question where I try to give answer and very probably as usual with a compromise.
Until now I found that in “theory” with a simple static formula , the so far developed models can sustain about 7knots, over that speed the model increase heel and 45° of heel is reached rather fast with 2 knots more.
Another question : what is the average wind speed in various regions of the world ?
If is only 5knots, then my designs are valid, and up to 6.5-7 knots is still acceptable ! Over that speed it become problematic and a solution “may” be needed !!
On the other end I do not like to go too deep as RGB suggested when asking for 149% that resulted in 206cm/208cm as depicted above.
These pictures are eloquent witness of what exist around, one is very interesting !
Cheers
ClaudioD
Hi cougar,
The 206mm is the answer to RGB above post where he was asking for 149% draft increase.
The Canterbury have a draft of 8" = 203cm
See : http://www.pmycsail.com/catalog_1.html
To get less Wet Area and acceptable RM is a matter of brainstorming at the moment !
Cheers
ClaudioD
Hi Claudio,
Thak you for very fast answer.
I want to build Endeavour to start in NAVIGA rules regattas. Model must be “true-to-original and close-to-original scale sailing boats in any scale”. The half of points are from “view” and half of points are from real regatta.
…“Craftsmanship …………………………………………….… max. 30 points
for the hull, including superstructure, attachments and details (relevant only
to above the waterline)
Accuracy ………………….…………………………………. max. 30 points
for accuracy of the model according to the presented documentation
Rigging ………………………………………………………… max. 30 points
for the craftsmanship and accuracy of the Rigging
Overall impression …………………………………………. max. 10 points”…
…"Allowed deviations from the original
There will be no points deducted during the models examination for the following deviations from the Original.
(1) Bigger draught – up to 150 percent in class A (Fore-and-aft bermudan rigged ships)…
(5) Jib may be attached to boom. "…
So I have to prepare close-to-original scale hull, equipment and sails and I need big righting moment (parts under water line are not judged).
Cheers
Grzegorz
HI Grzegorz,
you have not mentioned the scale of your project.
The hight righting moment can be obtained with a fin blade a bulb. This blade/bulb assembly can be sliding inside the “normal” hull keel.
The ones I’m working on are all referred to the same LOA of 127cm. Scale are of course variables.
In the J Class are around 1 : 325.
Is not my intention to deviate from my goal as often discussed in this tread. The only part that need to be finalized is the Ballast % and position !
Is this may helping you in taking a decision !! :
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In my opinion the best solution is the use of a traditional Fin/Bulb :
…
The advantage is that you can adapt the dept as function of wind speed expected for the day of racing.
Cheers
ClaudioD
Probably one of the answers is here :
http://www.wrcc.dri.edu/htmlfiles/westwind.final.html
http://www.usa.com/rank/us--average-wind-speed--state-rank.htm
http://fr.windfinder.com/forecast/nice
ClaudioD
Claudio,
Your designs make me want to build a monohull :D. I’ll have a go at Australia II when I next have the chance to build a boat. Thanks for your efforts.
Jim
Hi Jim,
I’m very please to know it.
Wish you good luck for the construction !
Cheers
ClaudioD
I went cross-checking with the Madcap design and I decided to see what can be done with the Endeavour without disturbing the Hull lines above the water. This is what I found.
I need to retrace the Curve of Areas to see where the LCB is and what will be the displacement.
The parameters I have in mind are close to : 5.2kg and 3.5kg ballast.
…
When observing the video on Madcap, the keel layout is not disturbing the overall view : http://youtu.be/YEmD4Ge1DYs
http://simbc.wetpaint.com/photo/5117126/Richard+Roger's+Vintage+Marblehead+Madcap
http://simbc.wetpaint.com/photo/5117126/Richard+Roger's+Vintage+Marblehead+Madcap
Certainly the RM is rather improved when considering a wind average speed of 5 to 7 knots !
Any comment about ?
ClaudioD
Hah
now that’s cool!
On all the various M-Class boats I’ve been associated with I have found:
100-150oz in of torque works best on a Drum Winch
300-350oz in of torque on an arm winch.
Claudio,
Don’t forget that the VM Group rules will allow you to build a boat up to 12" Maximum draft. or 304.8mm
You’ll get a real nice righting moment out of these boats if you keep the traditional hull form, and just fair the keel lines.
And if you did that you’ll also have the option to use the taller rig (Maximum headboard height 85" above deck as mentioned)
Hi Breakwater,
yes of course, but I’ll try first to reduce the wet area.
Here another example with a shorter keel close to a “normal” J Class draft.
…
It may be also possible to use different ballast keel dept and adapt the situation according to the wind speed of the day, but I need to check first the positioning variations of the LCB and CG…
The use of taller rig is not excluded by profiting of the Rules limits.
Cheers
Claudio
lol… ok now… step away from the computer… you have been burned out… why dont you have a drink and relax… you have been doing great work. but a 12 meter style J???
lol… you need a break
I’m sort of with cougar on this one. When one looks to the evolution of the 12M class one sees a distinct change from the uber traditional ‘J’ type hull of the 1950’s through to the shorter keel variants of the late 1960’s & 1970’s. I’m sure that had the J class remained the yacht of choice she would almost certainly have looked similar to these drawings at some point in her evolution.
I suppose for me a fin & skeg hull form just isn’t a ‘J’. Personally, it’s not just about those beautiful flowing lines at mild angles of heel, it’s also about the impression of immense power when viewed from the windward side and she’s seriously over pressed.
I certainly have no desire to take away from what you’re trying to achieve, it’s just that to me, a ‘J’ without a full keel just isn’t a ‘J’. Don’t misunderstand me; there is definitely a place for yachts combining graceful lines above w/l with ultra modern underwater profiles (try a google search for ‘Spirit Yachts’) but I do think we should be honest about what they actually are.
Other than that, I do think that what you’ve drawn has fabulous lines - those underwater profiles remind me of other British classics like the Rival yachts from Peter Brett and the Contessa32 from Jeremy Rodgers, all fabulous (& beautiful) in their own right.
I’ll try and think some more!!
Cheers,
Row
well, one could always think outside of the box and add Australia II’s wing keel!