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Catalina 25 Specific Forum

1977 C25 plans, to scratch-build a model

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Scott_on_Epitome
Deckhand

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Canada
4 Posts

Initially Posted - 03/27/2004 : 01:55:37

Hello,

Does anyone know where I can acquire plans (I think they're called drafts, though I'm really not sure) of a 1977 Catalina 25, for the purpose of scratch-building a model? Any information would be greatly appreciated.

Thanks,
Scott

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 03/27/2004 : 09:20:02

Scott,
I have a friend that scratch-built a C22 model . . . I'll ask.

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tinob
Master Marine Consultant

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USA
1883 Posts

Response Posted - 03/27/2004 : 10:07:22

Scott,

This site has a brochures and manual section that you may be able to get sufficient pictorials from to scratch build a 25. Short of that you might try the factory for information. Can you garner sufficient information just from the photos attached to the many posts herewith.

Val on the hard DAGNABIT

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Scott_on_Epitome
Deckhand

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Canada
4 Posts

Response Posted - 03/27/2004 : 23:26:00

I don't think I can get enough detail from the brochure pictures, but I may be able to work with some pictures. Drafts would be the best thing, though, just to get the curve of the hull exactly right.

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Designwiz
1st Mate

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USA
59 Posts

Response Posted - 03/28/2004 : 15:49:07

Hi:
As a design engineer that has made a profession in the computer modeling and development of new products this particular post is very interesting to me. I have always wanted to model, with as much detail as possible, my 1987 C25. This may be the start of a new side project for me. How much information in the form of blueprints and engineering data is available for this particular model of the Catalina Yatch line. Software applications to be used are most likely Rhinoceros 3D for the hull shapes (already used in marine design) and either Solidworks or Pro Engineer for the deck structure and rigging. Models done in multiple platforms can be merged thru translators. Perhaps it can all be done in Rhino3D but I will have to see initially how the hull comes along. Has anyone out there already done any computer modeling on this fine sailboat and if so would you be willing to share what you have already modeled and I will pick up where you have left off?

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 03/29/2004 : 00:17:50

Scott, Designwiz, and others<blockquote id="quote">quote:<hr height="1" noshade id="quote">...to get the curve of the hull exactly right...<hr height="1" noshade id="quote"></blockquote id="quote"><blockquote id="quote">quote:<hr height="1" noshade id="quote">How much information in the form of blueprints and engineering data is available for this particular model of the Catalina Yacht line. ...Has anyone out there already done any computer modeling on this fine sailboat...?<hr height="1" noshade id="quote"></blockquote id="quote">
I think what you're looking for is called "lines drawings" or "table of offsets". They both contain the raw data required to reproduce the shape of a sailboat hull. Both are proprietary information. Some one design organizations (International Lightning for instance) are willing to share hull form data (usually for a price). A sole manufacturer (in this case Catalina Yachts) is unlikely to be cheerfully forthcoming with this info.

You might also be surprised and dissappointed to discover how little digital data ever existed regarding the shape of the C-25 hull in the first place. Remember, sailing vessel hull design is not exactly a new field of engineering. Nor is it one with a long history of enthusiastically embracing state of the art technology.

There are other ways to acquire lines & offsets data for an existing hull. If you read up on the traditional naval architecture definitions and procedures for "lofting", "lines drawings", "table of offsets", "taking of lines", "taking of offsets", and have an example hull sitting on a trailer in your driveway, I think some possibilities may occur to you. If nothing else, you'll end up with a whole new appreciation for how boats happened before computers were invented, and you'll have several new reasons to kiss your CAD system each morning.

-- Leon Sisson

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Steve Kostanich
1st Mate

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88 Posts

Response Posted - 03/29/2004 : 11:51:46

Leon,
I had always wondered how the famous sail yacht design masters, from the turn of the century (1900's+/-), created the full size sections of each frame station of a hull, and last fall I had the opportunity to visit the Nat Herreshoff museum in Bristol, R.I. There is a recreation of his design office with dozens of the half models he carved as the initial design of a given hull. Most interesting was the pantograph that was used to transfer the station contours from the model to full size. The full size hull was virtually a duplicate of the model via the pantographic enlargement. It appeared no other measurements were taken from the model, but I can't confrim that. EVERY sailer should visit this museum, it is fasinating beyond belief!!

Steve Kostanich C-25 Equinox 1119 sr/sk

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 03/29/2004 : 13:01:09

Steve,

What most amazes me is trying to picture the thought processes that must have gone on between the time a potential customer said, "I have too much money, build me a yacht", and the presentation of the resulting half model. I'm picturing some Zen-like trance in which the master craftsman holds the partially carved model in his hands, closes his eyes, and mutters to himself, "Don't just try to see the water, be the water."

I mean, now we have mind boggling computer modeling tools and tank testing facilities to guide us. What did those guys have to work with? A sharp whittling knife guided by rough hands, an experienced mind shaped by years at sea, and a depth of intuitive insight into physics I can't begin to imagine.

-- Leon Sisson

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Scott_on_Epitome
Deckhand

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Canada
4 Posts

Response Posted - 03/29/2004 : 13:44:42

How would I go about creating a table of offsets from the hull? I'm admittedly inexperienced in yacht design. If it's a rather long process to describe, can someone recommend some literature or websites where I can find the procedure?

Thanks,
Scott_on_Epitome

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svmoxie
Past Commodore

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USA
331 Posts

Response Posted - 03/29/2004 : 15:21:06

Taking lines off the hull is possible...

http://www.mysticseaport.org/library/infobulletins/ib911.html
http://www.yacht-designer.co.uk/page73.html
Boatbuilding Manual by Robert M. Steward
http://sailing.about.com/library/weekly/aa080701a.htm

but the first thing that I would do is contact Catalina Yachts and see if they will give or sell you the table of offsets for the hull. Please keep us informed of your progress and decisions as I for one would be interested in creating a half hull of my own.

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Sea Trac
Master Marine Consultant

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Vanuatu
1357 Posts

Response Posted - 03/29/2004 : 16:11:21

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Leon Sisson
 I'm picturing some Zen-like trance in which the master craftsman holds the partially carved model in his hands, closes his eyes, and mutters to himself, "Don't just try to see the water, be the water."<hr height="1" noshade id="quote"></blockquote id="quote">
Or perhaps [url="http://iws.ccccd.edu/mbailey/fibonacci_text_only.htm"]0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987...[/url]

Although, it'd make for a fairly long mantra.

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Designwiz
1st Mate

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USA
59 Posts

Response Posted - 03/30/2004 : 12:50:59

Hi Scott....
I'm going to start taking some measurments of the hull this weekend to create my series of loft lines. I hope to try and take a measurment every half inch verticaly and 1" horizontally. That will give me a collection of data points of which I will use to create the port or starboard surface model of the hull. I really only need to measure off one side of the hull since it is symetrical. Once created I'll mirror the created half hull surface over the centerline of the boat. Then join them together add my external radiuses and shell it out (to make it hollow) and give it a thickness. Assuming the thickness of the hull to be about three quarters an inch (can be adjusted later). Will let you know when and if I get the hull finished. I don't think there is a problem with this unless I try to make money off the computer models. I'm sure the designs are patented and protected in that way..

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 03/31/2004 : 00:24:21

Designwiz,<blockquote id="quote">quote:<hr height="1" noshade id="quote">I hope to try and take a measurement every half inch vertically and 1" horizontally.<hr height="1" noshade id="quote"></blockquote id="quote">I doubt you will need anywhere near that many points. Traditional lines drawings and tables of offsets typically include only 20 stations (like evenly spaced frame locations) over the entire length of the vessel, and maybe three to five waterlines and/or diagonals. For areas of rapid cross sectional transition (localized short radii, such as bow and canoe stern, keel attachment stub, faired rudder skeg, etc.), additional half-stations or other cross sections are added if needed. Displacement sailboat hulls are by their very nature mathematically predictable fair curves, so the intermediate points are easily calculated. Obviously 'most any CAD system can create a fair curve given three or more (X,Y,Z) points, so why not let the CPU do the work for you?

If you're not familiar with naval architecture drawing conventions, you might consider giving Bob Perry a shout over on either [url="http://www.cs-bb.com/forums/CSBB/index.cgi/"]CS-BB[/url] or [url="http://forum.cruisingworld.com/forums/genlmesg/"]CWBB[/url]. Bob has impeccable credentials, and is usually quite willing to discuss design theory, and can be very helpful. I'm sure he could also steer you to some reference texts that would in the not-so-long run save you time over the "measurement every half inch vertically and inch horizontally" approach.

If the thought of studying exceedingly tradtional texts on boat design drawing conventions doesn't appeal to you (some young whipper-snappers seem to be allergic to reading books written by dead people

), then perhaps you'd prefer "The Gougeon Brothers On Boat Construction, available where large quantities of WEST products are sold. (Last I heard, the Gougeon brothers were all still obove ground, and Jan was sailing at speeds up to 60MPH.

)

I hope I don't seem critical (as in discouraging). I really want you to succeed in digitizing the C-25 hull. My suggestions are offered in the spirit of helping you find the path of least frustration to your goal.

Picture yourself being able to use a CNC mill to whip out wooden half models to order as gifts for every C-25 owner out there!

-- Leon Sisson

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Scott_on_Epitome
Deckhand

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Canada
4 Posts

Response Posted - 03/31/2004 : 11:39:28

Designwiz-

Once you have got your measurements, could I get a copy of the table of offsets (or however you have tabulated your dimensions) from you? My 25 won't be out of the water for quite some time, and I'm not sure that it's worth bringing out just for measurements.

Thanks,
Scott_on_Epitome

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