Thoughts on hiring a naval architect....

[Manie B]

i have been reading this thread and always wondered where it would go

lascraigus i am basically already doing what your line of thinking is

my boat is a scaled down mini
look carefully at my hull lines - its a mini at 16' 7' more or less to "micro standards"

http://www.microclass.org/page.php?page=part4

all i that i have done differently is to raise the sides to give me 4' 2" sitting headroom and a flush deck with built in toe-rails like the old trawlers

i have done a sh1tload of research over the past five years, done a lot of offshore sailing and have a current January 2010 skippers license.

my sailing friends (some of whom have extensive global experience) and i are very pleased and confident how this project is going so far

you are most certainly on a good path - keep on at it
dont go too far of the line
and the advice that the guys have given here is very good

follow the links at my signature

[lascraigus]

Manie- thank you for all of this great information! I accidentally left my stick drive @ work so any further modifications made will be posted later! So glad to hear that this sort of thing is being attempted by others as well! The main thing I am worried about is after making a scale model (say roughly 4 ft in length) will it give me accurate information on real world performance? I do not want to end up like these guys(albeit different type of vessel, but STILL what were they thinking??:

http://www.woodenboat.com/forum/showthread.php?t=99253

Perm- I agree with what you say about making a scale model large enough! In my architecture schooling we would have to do the same to be able to analyze force loads and the like.......and let me tell you.......those scale models were NOT cheap but after x number of dollars who's counting....

I will certainly be researching about Reynolds numbers more in order to give me the most accurate measurements and feedback data possible. I know little about fluid dynamics but that is what the library is for (i'm a book nerd ) I figure my friends at the Mechanical/Aerospace department on campus can give me some pointers hehe. My train of thought on such design has been to "make it look as much like a fish below the waterline as you can....streamlined and smooth, not boxy." they have been quite successful....although I say that in half-jest.

[Manie B]

Seeing that you are technically / engineering minded this will help

get Freeship or Delftship that will give you resistance values of your modelled hull
very nice tool to play around with

buy the book
Principles of Yacht Design
by Larson and Eliasson
probably the most valuable asset to your library

knowledge is power - the bigger the library - often the better the hull
nothing is gauranteed in this world, but you will feel better

yacht design is a life changing science
the more you learn - the less you know
you get sucked into a vortex of continuosly wondering how this will change that
get ready for the ride of your life, for the rest of your life

[lascraigus]

Manie- thanks for the information. I will be getting a copy of The Principles of Yacht Design. I have been doing some work in Delftship with varying degrees of success. Wish there was a flag or cursor or SOMETHING!!! that says PUT KEEL HERE.......or PLACE MAST THERE. hehe. Intuition is getting the best of me. Regards.

[capt vimes]

hehe...

you want to build a boat - start number crunching...
intuion will not get you there...

manie:
intersting page there - thank's...
but i am not happy with the rule that a centerboard have to protrude the hull by 20 cm when fully pulled upwards... and that the stability requirements have to be met with the centerboard in the upward position...
thought i had a good idea, till i found this rules...

edit:
this image is just something i draw up in freeship... this crap will not sail well...

[Manie B]

Yes they do have some "odd" rules that apply to them
fortunately i am on other side of the planet and basically doing my own thing - for myself

what i just found, is the more number crunching i did, the more frustrated i got AND i ended going around in circles

I am a mini fan - just plain love it
thats why i ended up with a "mini-mini" for my purposes
nothing really new
nothing really spectacular
just proven modern design - not trying to re-invent the wheel er "boat"

as you may have seen i regularly crew on a Lavranos 36 and a Beneteau 35 for offshore racing
thats why i wanted a small light boat with good light wind performance on a run, for coastal cruising.
a comfortable lee bunk
good sitting headroom
inside steering
PARADISE

[lascraigus]

well this is a preliminary in Delftship: the hull is not faired, but I think I am getting the basics down in this program. Any thoughts, comments, concerns (of which I am sure there will be several) have at it!! There's quite the learning curve, but Manie you are correct: this is almost a disease: I go to bed thinking about how things can be changed, what would happen if I did this, added that or subtracted that so on a so forth.....It all makes me wonder how all of the design work got done by HAND, slide rules, pencils,vellum paper and sheer will back in the 30's when the big J-boats like the Endeavor were out circling the piers.

[lascraigus]

too beamy I'm sure

[Perm Stress]

"well this is a preliminary in Delftship: ..."

Congratulations with first results!


Bow and stern lines look strange... they are pinched in.


Did you look at curve of areas? It is visible in "Profile View" in "Wireframe" mode.

Did You try to use Control Curves? They are extremely useful tool in Delftship. I would say, sometimes more useful, as Gaussian curvature and Zebra shading.

I would also recommend not to model knuckled transom slope until You get really familiar with intricacies of software. The problem here is, that making a knuckle like in the hull you just posted, unavoidably create knuckle point, and this point ruin all the fairness around it. It is possible to fair a surface around such points, but is tricky and (at least, to my experience with Delftship) not friendly to later modifications of hull form. In the beginning I always make hull surface extended beyond the intended transom, knuckled deck or whatever of this kind. Only quite late in design, when it is not likely I will modify basic hull shape for more as ~0.1m (Y or Z direction) for ~60m hull, I start to introduce cknuckled transoms, stern platforms, etc. ... .

Good luck in Your efforts.

[lascraigus]

Perm- I agree the bow and stern look pinched.....couldnt figure out how to adjust it without the whole thing freaking out (read:me). I was just playing around with the extrusion tool and viola! There it was, so I kept it (its on a different layer so getting rid of it shouldn't be a prob, although I kinda like it. When it happened by happy accident I thought oh! That looks like a miniature swim platform. Ok.....now what?? Looking through the user manual I found nothing that really explains how to do this or how to do that.....it just says you can. I suppose a work in progress is still a form of progress indeed: provided my mac starts behaving better! Thanks for the advice, I think I will give it another go.

[capt vimes]

las
you will find this thread about free!ship in the software section:
Modeling boats in Freeship-The techniques of Using the sofware

while free!ship is not delftship, both programs are quite similar and might give you some ideas of how to work with this software efficiently... there are also some tutorials linked for downlaod...

i am no NA but your waterlines on that hull look... strange - for no better word... but than again... i have no experince...

[Manie B]

lascraigus what you should do with freeship first

enter your basic dimensions in the prompt box
now study what results you get - the whole bang shoot of parameters
every abc - xyz that you can see cog cof lcr and and and

now as you manipulate your "new" master piece
constantly compare your results with the "standard"

this is very very very time consuming - but you will learn that by straying off the "golden" path you dont always gain

freeship and delftship cant really cater for the modern "planing" hull ala open 60 volvo or mini's
but the values up to 6 knots gives a clear indication of where you are going with your resistance and displacements
now when you study the books many things become clearer

[luckystrike]

Hi Lascraigus,

I just found your thread and I wonder what are you doing. As this will be your first design right, will it be your first boat to be built too? What shall happen if your design is finished. Will you do it on your own or will sombody build the boat for you?

For the time and money you spend into delftship and in the modell (don't think it will be done fast and cheap) you also can buy a set of plans for the
"i 550 sportboat" from duckworksmagazine, clear your garage and start building the boat that is able for what you want.

If your new hobby ist boat design, then proceed with fun!!!!!

If your hobby is sailing or boating, then design a small dinghy or tender first and build a modell and the real boat afterwards. If you go the whole process you will understand boatdesign a lot better than on the way you are going in the moment.

Grrreetings from the North Sea Coast, Michel

[luckystrike]

Designing on Paper..... and just because you where asking

is a process that is a little slower but its more logical. First you make 1 to 3 sketches what the boat will be to put everything into the right position (cockpit, mast, cabinhouse, bridgedeck, bunks, nav table, cooking, engine, rudder keel). The design itself starts with a profile, a deckview, a cwl (waterline) and the main bulkheads (transom, bow and three bulkheads). This enables you to roughly check the displacement and the center of volume. A wheight analysis showes if you can get everything in balance with the center of flotation. Pressure points of sails and underwaterbody = the same game. Then you draw the rest of the bulkheads and make everything fair.

This design spiral is done several times until everything is ok for your mumbers and feeling. Then it goes to the workshop.

Michel

[Stephen Ditmore]

Wisdom of Olin Stephens when he spoke to my class at The Landing School:
Priorities:
1. Strong enough
2. Stable enough
3. Controlable

This next is from me, not Olin:
Concerning stable enough, a quick rule of thumb is to assume 1 pound per square foot of pressure on the sails, then calculate the heel angle and see if that's about where you want to be.