J Class Yacht Design

Hey guys, new to the form, and new to investigating the possibility of building my own boat. I have for the past few days been trying to find schematics for a J Class sailing Yacht in the 50ft range of size, for single handed sailing. Which leads to my first question, has anyone ever stumbled across such a thing? Preferably a fiberglass build.

If not, any suggestions on which hull design program would be best to design a hull of this type that is not going to break the bank? I found some crude layouts of a few of the J class yachts, more or less want to use them for a basic design to build from, and adjust the scale.

 

J class boats are much longer than 50 feet. The smaller ones are about 120 feet. If you are worrying about not breaking the bank, this is not a viable project; unless you have a few million in that account.

 

Is there a particular reason why you couldn't take the overall design of the ship and downsize it? I understand the reason for the length of the J classes that are made now. But in the past they were made in significantly smaller lengths for different race classes.

 

Welcome to the forum.

Down sizing a little (say up to 15%) is safe, but more than this, and you need to reevaluate the design criteria. The J's were the playthings of the society classes and not anything remotely inexpensive. The class was folded because of the costs associated with their construction and operation. So, if you have literally 10's of millions laying around with nothing better to do . . .

Now a 50' J class watanabe is possible. Have a look at the "W" class and see if it'll spark the same emotions. If so, I know of a 48' W class for sale, built in 2014 and a mere 1.2 million.

 

You can have a look at Hoek design and Leonardo yachts, specialised in "J class look" yachts, meaning Jclass overhangs, modern appendages inc. inverted T keel bulb :
Hoek Design » Josephine II https://www.hoekdesign.com/yacht/josephine-ii. , a 36´
Leonardo Yachts - eagle36 http://www.leonardoyachts.com/en/eagle36.html
Leonardo Yachts - eagle44 http://www.leonardoyachts.com/en/eagle44.html
Leonardo Yachts - eagle54 http://www.leonardoyachts.com/en/eagle54.html
.... and if you are a wealthy man :
Hoek Design » Firefly https://www.hoekdesign.com/yacht/firefly1 , a 115´

 

Something like this:
1926 Classic Yacht R Class Racing Yacht Sail Boat For Sale - http://www.yachtworld.com/boats/1926/Classic-Yacht-R-Class-Racing-Yacht-3106109/Newport/RI/United-States

?

 

heres one of the j classes I designed, it can be reduced in size
Stern | Boat Design Net https://www.boatdesign.net/gallery/stern.23487/

 

There were no significantly smaller Js. The Js were one of a range of different sized yachts built to the Universal Rule. The classes ran something in decreasing size from J down to S, with some gaps. Each class was determined by rating and as the classes developed, each got longer. A 50 foot boat built to that rule is either a "Q Class" (as of about 1928 they were around 46-47ft long) or a P Class (which were around 54 feet long).

If you want to build a 50 footer that is like a baby J Class, look for a Universal Rule Q or P Class and there'll be designs from legends like Herreshoff, Gardner, Burgess, etc. If you just shrink a J you'll run into all sort of problems of scale; for one, it will be too low in freeboard. The Qs and Ps were often more advanced design than the Js, because the new ideas tend to come from smaller boats were experiments are less costly.

Another option is to look for an 8 Metre, which is of similar general style and length. That way you have the support of an active class.

If you go to archive.org or hathi trust you can find old copies of Rudder magazine, full of plans of old Universal Rule boats.

 

MattyB, the J Class yachts inspire many people... myself included. Without question we can agree they are the most beautiful yachts ever built. I would encourage you to look at the Universal Rule and understand the rating (wiki article is a good start; Universal rule - Wikipedia https://en.wikipedia.org/wiki/Universal_rule ) Some of the more seasoned designers or engineers here will correct me if I'm not using the right words here, but essentially to maximize the potential of the rating rule is why the J class yachts ended up so large and with so much sail area. For my limited ability in actual design but roughly understanding the principles, yes a J class can be scaled down BUT it could a) not look right, or b) not meet the Universal Rule. There were many other yachts built to the Universal Rule and they still have the look of a J. Google Larchmont O Class and you will see an example that is 60 ft LOA, 12 ft Beam and very pretty.
If sticking to racing rules does not matter to you, and you are looking for the pleasing lines and emulating sheer beauty of the J class at a more realistic build/up-keep cost then you should look at classic designs in general. Try going to the Sparkman & Stephens blog and look at the design drawings in the 40-60ft range. The lower the design number the older the design... in the low design numbers you will find many beautiful examples of classic yachts will long overhangs fore and aft.
Good luck finding what you are looking for! I have been doing the same thing for the last 5 years... no rush, I have learned a ton and it's far better reading than sitting through hours of brain-dead TV.