Extending Stern

I'm toying with the idea of extending the stern of my 56 foot Steel 1961 Chris Craft Roamer. I would like to add anywhere from 8 to 10 feet. Are there a standard set of calcualtions that can be used to determine the best length. I'm currently restoring her and was wondering what the possiblities are for this idea. I have the necessary welding equipment to perform this procedure but, just because you can does not always mean you should

 

I'm not familiar with this vessel however it will depend on the construction of the existing hull, scantlings and spacings. Usually you will find if you add this sort of length then all the frames need beefing up, this can often be accomplished by simply increasing the height of the floors but i'm afraid it is advice best sought from a local engineer.

A rough do-it-yourself guide would be Dave Gerrs 'Elements of boat strength"

 

I piloted a boat that had a full waterline extension added to stern( 57 Hatteras Motor Yacht with an added sports fish stern about 8feet, it had major problems. Props and rudders where now more at center of boat. It had tracking issues. Eventually rudders had to be increased. But it never worked right

I have a boat that built extension platform but not on waterline
checkout http://www.mydauphin.com/html/more_pictures.html
does not affect boat performance except weight. You can see where line is.

 

Also realize that laws change when you make boat longer than 65 feet, there are changes for lights, toilets, etc... i Kept mine at 64 feet eventhough it is closer to 72

 

I can imagine there would be problems. I am surprised someone would do something like that and not move all the propulsion etc. back. That could be why a lot of additions are put in the middle and all that stuff can be left as is.

 

It is really not an easy thing to do, and its should be done with the help of Marine Engineer. Moving propulsion is not easy at all and very expensive. It is probably better to sell boat and buy bigger.

 

Saw a 94ft. triple jet drive steel motor yacht at a Florida yard. The fellows has added 15-20 (?) feet mid-ships. Think they contracted to a builder.

Tim

 

the way ships are lengthened is to the middle of the ship, , your lines may not allow this, do you have lines? other than that, most of what has been offered here is dead right advise

 

whoops sorry tim, wrote same as you

 

No problem Lazeyjack. Repetition builds success!

Tim

 

Also as a boat gets bigger, dock space is more, everything cost more. I am having a heck of a time finding dockage. Very few place in Miami can handle a 70 footer, and they are charging an arm and leg. If I had to do again - I would go smaller.

 

Thanks for the information quite a few of my questions have ben answered. If I were to extend it I would also move the rudders and props as well, I assumed that to be the norm. But for now it will remain an idea. Purchasing a larger vessel would be easier