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Old 31-01-2013, 02:35   #1
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Hey, I know what... Let's design a yacht!

Weee don't need no steenkeeng professionals!


I actually intend to build this, as a 1/12 scale RC model. It won't be built full size unless I win the lottery or something, but it should
be BUILDABLE and PRACTICAL built full-size in case I do, or anyone else cares to. The real purpose of this exercise is to just
manipulate and massage the parameters and find the best set of compromises that will fit the following requirements:

1. A fairly fast cruiser. Speed is not the essential thing, but it is a consideration. The boat should be capable of a consistent 9kt
speed in any reasonable wind at most points of sail. Doesn't have to be a flying surfboard... then it wouldn't be a cruiser at all.

2. Living space is important, but some reasonable sacrifices can be made. The design should be practical for living aboard or
for long-term cruising for a couple or maybe a threeple, up to and including circumnavigating in a timely and comfortable fashion.
There should be room for entertaining a like number of guests at dockside or anchorage, or on a day sail.

3. Good maneuverability, especially tacking and sailing close-hauled, common weaknesses in many hardcore cruisers.

4. Length about 48 feet long LOA, a decent length that should give true bluewater performance and at least as much room down
below as a more serious 40 footer, but not so long that a slip would cost an arm and a leg and maybe another body part or two.

5. Beam just under 12', to reduce the hassles involved with trucking the hull to a launch site.

6. Reasonably shallow draft, like around 6'.

7. Air draft of under 65' to pass under most modern highway bridges in the U.S.

8. Ease of handling, particularly for single-handing. Decent tracking, easy self-steering. Lines led to cockpit for minimum
operations on deck in bad weather.

9. Low HP requirements, for motoring at 1/2 to 2/3 hull speed.

10. Survivability in a grounding, knockdown, or rollover

11. Floatation even in a massively flooded condition. Not unsinkable as in "Titanic", but unsinkable as in cut in half with a
chainsaw and both pieces still float. Flotation as in stick with the boat even if there is a 20 foot hole in the side, cause it will float
better than the life raft.

12. Economical construction, maintenance, and operation, including the greatest practical independence from fossil fuel use, and
simple fiberglass construction.

13. Self-contained independance including watermaking or catchment, alternative power generation, and simple user repairs of
essential systems.

14. Easy scaleability of design, with dimensions that can be arrived at mathematically for rapid computer assisted layout of
frames, etc. I actually envision a program that the user could use to customize the hull design after inputting and adjusting
parameters. Enter your length, beam, molded depth, tumblehome, bow flare, rocker, keel length, position, depth, sweep, overhang
at bow and stern, sheer, camber, etc and it spits out a complete set of coordinates for lofting the frames and a suggested mast
step position and weight of ballast.

15. A BIG battery bank, batteries doubling as ballast. Electric or hybrid electric propulsion would then be an option. Too many
electric boats are simply overloaded with batteries, or else the bank is too small. Plus it is just nice to have lots of batts for
household conveniences. Even dead batteries make good ballast.

16. An absence of explosive or highly flammable fuels or other substances.

17. Ease of getting ashore and getting guests or officials to the boat.

18. Security, including secure storage.

19. Good heavy duty closures. True marine grade watertight doors, hatches, windows/portholes, and vents.

As your posts come in and I read them and as consensus is reached on various details, I will compile what we have and update
our design.

The design itself will be the property of all of us, and of nobody in particular. Call it the Open Source Cruiser. (OSC) It will be there
for anyone to use, for pleasure or for profit. Think of it as the Friendship Sloop of the 21st century.

The classic cruiser of the Dreadnought/Westsail/Tahiti Ketch type is great for running free where the wind happens to be going.
They are tough as nails and will out-survive their skippers and crews. BUT... isn't it lovely to be able to point well, to make
respectable progress to windward if that is where the desired destination lies? Isn't it nice to be able to put the motor to bed and
not crank it up again until docking time? Those classic old designs are out for this project. I don't want to be somewhere and say
to myself, I would like to be THERE, but I can't get there from here unless I go all the way around the world. OTOH the modern
cruiser/racer with it's fat flat stern section really pounds, and it sucks to lose keel bulbs and stuff. They can be kinda scary surfing
down big waves. All boats are an exercise in compromise, and always have been. I want us to do the same old compromising, but
keeping in mind the lessons we have learned over the last 40 years about what has worked for us and what hasn't.

For the purpose of keeping this process organized and orderly, I am dividing the process up into steps. I hope we can hold off on
doing something in like step 26 while we are still delibarating on say step 3.

Phase 1. Overall extreme dimensions.
Phase 2. Side/profile view. Sheer, overhangs, rocker, etc.
Phase 3. Main Frame cross section, hull and deck
Phase 4. Stern cross section.
Phase 5. Keel and rudder configuration.
Phase 6. Cockpit or pilothouse configuration
Phase 7. Mast placement and a tentative sail plan, standing rigging.
Phase 8. Propulsion, power generation, and electrical distribution systems
Phase 9. Plumbing systems.
Phase 10. Ventilation systems
Phase 11. Galley and heating systems
Phase 12. Refrigeration systems
Phase 13. Tankage
Phase 14. Ballast, trim, loadlines and stability
Phase 15. Operating systems. Halyards, sheets, winches, tracks, travelers, windlass, steering, etc
Phase 16. Dinghy carriage, launching, and recovery.
Phase 17. Navigation and communications systems.
Phase 18. Safety and lifesaving systems, and compliance with applicable regulations.
Phase 19. Overall cabin layout.
Phase 20. Actual construction methods. Male mold, female mold, glass on frame, whatever.
Phase 21+ All the details we are gonna argue about after the first 20 phases.

I anticipate this process to take at least a year. I don't see how we could rush it quicker and do a good job. As we go along, I am
sure we will have to go back and re-think and adjust the results of earlier phases to accomodate the later ones.

So in the next post I will kick it off with Phase 1 preliminary overview.
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Old 31-01-2013, 02:52   #2
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Re: Hey, I know what... Let's design a yacht!

PHASE 1. OVERALL EXTREME DIMENSIONS

I started with a 48' length and 12' beam, with the main frame, the point of widest breadth, 12' from the stern, 36' from the stem. In
keeping with point 14's requirement for mathematical solutions, the plan is based on an ellipse centered at the main frame and the
centerline. The ellipse is 48' x 12'. The after 12' of the ellipse is cut off square for the stern. A line from the stem is drawn
tangential to this ellipse for the bow. I wanted some pinching off at the stern, and not a simple skiff stern, and I wanted a fine entry
at the bow, with no bluffness, no convexity. Anyway, that is what I drew, and after about two dozen trial drawings with the ellipse
longer or shorter, I found the result pleasing to the eye and intuitively, without any particular basis in knowledge of yacht design, it
seems like it would sail.

Yes, a more rounded stern I am sure would be more seaworthy. Yes, a consistent cross section from the main frame all the way aft
would make a boat that would exceed hull speed on a broad reach and outsail the wind. But this is an exercise in compromise, as
I said, and the design must be sailable in big hairy oceans as well as fast enough to get somewhere someday/sometime. Over 12'
beam and you start getting into a whole other category of road permits and escort requirements that would add greatly to the
complexity of a project for a backyard builder, especially one far from blue water. 48' seems the ideal length. But I will certainly
entertain suggestions and reasons for going longer or shorter, wider or narrower, or a bluffer entry or curvier bow. But mainly, how
does everyone like the extreme dimension lines? Should the bow have some curve, or not? Should the shoulders be brought
forward, or aft? More transom, or less? I want to keep this on the table for a couple of weeks before we call it done and move to
phase 2. Who has some input? You don't have to be an expert to contribute something, but if you are, please say so.

In the next drawing I did something a little different and went with a slightly more cruiser-ish bow. There is no straight line from
stem to an elliptical curve. Instead, the entire side is a segment of an ellipse centered 36' away from the centerline. Not quite so
slippery looking, but the convex curve shape should be stronger and slightly less prone to pounding.

In the next one, I did the same, but only offset the ellipse 12'. Notice the bow is a little rounder. Greater strength and seakeeping
ability? Slightly degraded windward performance? It looks very sailboaty to me.

Those last two drawings might benefit from a separate ellipse aft of the main frame, maybe? To pinch in the stern a bit?

Finally, I overlaid the last two together to illustrate the difference in curvature.
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Old 31-01-2013, 03:38   #3
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Re: Hey, I know what... Let's design a yacht!

Can we get charlize theron for a figurehead?
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Old 31-01-2013, 03:46   #4
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Re: Hey, I know what... Let's design a yacht!

Quote:
Originally Posted by seahag View Post
Can we get charlize theron for a figurehead?
I don't think that falls into the Phase 1 category, but sure, why not? Let's remember to discuss this when we get to figureheads.
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Old 31-01-2013, 03:58   #5
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Do you have a target cruise loaded displacement?

That full flotation requirement will be tough.
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Old 31-01-2013, 04:07   #6
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Re: Hey, I know what... Let's design a yacht!

I never was too orderly. Thanks for helping me to keep on task. Is the boat grp, ply/glass or ferro? Or, up to the builder?

When you got to " rounded stern" is where my mind drifted to c.t.
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Old 31-01-2013, 04:07   #7
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Re: Hey, I know what... Let's design a yacht!

Given your requirements, I think you should be "designing" a multihull.


Ever designed a boat? Or lofted one? Do you know how to "prove" a design drawing? What do you mean by "main frame", are you referencing a station? And how about "cross section of stern", does cross section refer to profile, plan, or half-breadth view?
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Old 31-01-2013, 04:11   #8
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Re: Hey, I know what... Let's design a yacht!

I was thinking that the floatation could be done with sprayed icynene, which would also provide incredible insulation and soundproofing. Ive only done this with houses though and floatation was not an important criterion.
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Old 31-01-2013, 04:11   #9
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Re: Hey, I know what... Let's design a yacht!

This could be interesting.
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Old 31-01-2013, 04:17   #10
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I like the second one best. I wouldn't go with the super pointy first version as i think you should have more volume in the bow to prevent nose diving in heavy seas and running downwind. But it's a faster style than the third version so you would retain your performance and windward capability.

(I am by no means "educated" in boat building) pretty sure I understand the basic concepts though

Cheers

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Old 31-01-2013, 04:23   #11
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Re: Hey, I know what... Let's design a yacht!

Quote:
Originally Posted by bengearing View Post
I like the second one best. I wouldn't go with the super pointy first version as i think you should have more volume in the bow to prevent nose diving in heavy seas and running downwind. But it's a faster style than the third version so you would retain your performance and windward capability.

(I am by no means "educated" in boat building) pretty sure I understand the basic concepts though

Cheers

Ben

But these lines tell you nothing, as it's only a single waterline in half-breadth with no reference to distance from actual waterline. You can't design a boat like this. Is this the boats intended shape at the sheer, at LWL, or somewhere on the bottom? We don't know, because there's not enough information given and it's not presented in the traditional format. NA's speak a particular language for good reason...
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Old 31-01-2013, 04:32   #12
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Re: Hey, I know what... Let's design a yacht!

from your design parameters the end result may end up being a ballasted proa!
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Old 31-01-2013, 04:33   #13
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Re: Hey, I know what... Let's design a yacht!

Quote:
Originally Posted by daddle View Post
Do you have a target cruise loaded displacement?
Nope. We are starting from scratch here.

Quote:
That full flotation requirement will be tough.
Yeah but I think it can be done. If it can't, then it can't. Tried is better than not having tried. Once we got some reasonable idea of displacement at a workable draft, we can see how much space is available for watertight storage, voids, and solid flotation, and how much more ballast we CAN have or MUST have. So I am starting with a hypothetical hull shape and going from there, knowing that it will likely not survive unchanged it's first collision with reality.
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Old 31-01-2013, 04:37   #14
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Re: Hey, I know what... Let's design a yacht!

Quote:
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I never was too orderly. Thanks for helping me to keep on task. Is the boat grp, ply/glass or ferro? Or, up to the builder?

When you got to " rounded stern" is where my mind drifted to c.t.
I am leaning towards fiberglass with no plywood, but this is a committee thing. I want to see what we can come up with. When we get to Phase 20 let's talk about it.
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Old 31-01-2013, 04:42   #15
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Re: Hey, I know what... Let's design a yacht!

Quote:
Originally Posted by minaret View Post
Given your requirements, I think you should be "designing" a multihull.


Ever designed a boat? Or lofted one? Do you know how to "prove" a design drawing? What do you mean by "main frame", are you referencing a station? And how about "cross section of stern", does cross section refer to profile, plan, or half-breadth view?
Only designed or built plywood skiffs. Never anything like this. By main frame I mean the frame at widest extreme breadth, which is a handy datum for referencing things.
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