Lengthening a sailboat

Discussion in 'Fiberglass and Composite Boat Building' started by yorktownie, Apr 29, 2009.

  1. yorktownie
    Joined: Jul 2008
    Posts: 9
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Eureka, CA

    yorktownie Junior Member

    I have a Yorktown 35 aft cockpit fiberglass sailboat. I have lived aboard it for 12 years. It is fairly well equipped and in good working order. I took it to Mexico for a season in 1998. Now I have the desire to install a pilothouse and aft cabin.
    I asked Sam Devlin (Seattle boat desgner/builder and stitch and glue guru) if it could be done and if so would he draw up the plans. I would do the work. He replied that it could be done, but he hoped I was very much in love with the Yorktown to undertake such a task. My experienced builder friends also tell me it is a great deal of work to lengthen a boat. I would say I like my boat, I am certainly not in love with it. It is just a question of economics. It would cost at least 50K to sell my boat and upgrade to a 40-45 foot boat with a pilothouse and aft cabin. Also, I would probably have to invest in the new boat, since it would probably need work. At least the Yorktown is a known evil, and there are no hidden money pits. I want the pilothouse and aft cabin to be strong and look good. They must be watertight and the boat must handle as well as it does now, or at least nearly as well. Yorktown made 35, 39 and 41 foot aft cabin, center cockpit models. I would need to move the steering pedestal 2 feet forward and remove the fore and aft cockpit benches, then add 4 feet or so to the length aft. Can somebody briefly outline the process of lengthening a fiberglass hull so I can understand why it is such a tremendous undertaking?
     
  2. Eric Sponberg
    Joined: Dec 2001
    Posts: 1,989
    Likes: 190, Points: 73, Legacy Rep: 2917
    Location: St. Augustine, FL, USA

    Eric Sponberg Senior Member

    Yorktownie,

    I checked on the internet to get a picture of a Yorktown 35--which is a transom hull with an aft cockpit. Cockpit shape is fairly simple--no complicated contours. The simplest way to extend the hull aft is to do a fair extension of the hull lines. Cut off the back of the deck through the cockpit and throw that away, and rebuild the deck with the aft cabin and accommodation inside. The cockpit will likely be shorter so that you can use some of the room close aft of the deck cut for the berths in the aft cabin. You would likely gain a lazarette area behind the cabin for storage.

    All this involves labor hours and care to get the shapes of the hull and deck house right. The cost will be whatever it takes, and a few builders might give you some ballpark ideas before you commit to hiring a designer to do design and structural drawings.

    Some other things to think about: In a fair extension like this, the added hull length and accommodation are going to be right at the aft end of the existing waterplane, and most of that weight will extend aft of there with little to no additional submerged volume in the hull to support that weight. The boat is going to trim by the stern. To compensate, therefore, the faired hull extension should actually start behind the keel so that you can pick up submerged volume to support the extra weight. You will lose a lot more hull that will have to be replaced deeper down. That's a lot more work.

    Also, The rudder, in proportion, will be too far forward and maybe too small. So the rudder and steering system will have to be redesigned, rebuilt, and positioned further aft. That's more complication and more cost.

    Those are some of the factors that will go into such an extension.

    I hope that helps.

    Eric
     
  3. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 121, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    It's about as practical as enlarging your home by 6 inches in every dimension and a good reason to get excited about a new used boat that's bigger already.
    In addition, there's a lot of talent involved in both design and building. If you do the work yourself, you will have to be a very good designer/craftsman. If not done well, the boat might be almost worthless to any future buyer.
    Those are realities, but if you already are aware of them, go for it.
     
  4. yorktownie
    Joined: Jul 2008
    Posts: 9
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Eureka, CA

    yorktownie Junior Member

    Yes, failure is not an option. The thing is, I will never get my money back out of the boat anyway. Yorktowns have low resale value, even pristine, well maintained and improved ones. I could not get more than 20K for my boat and have put at least 65K into it. I had not considered moving the rudder, and it might not be necessary. The boat has a 'fine' clipper bow. There is a 40 gallon water tank under the Vberth and the sailing performance is noticably affected when the tank is full - it can slow the boat down by a knot or more. I would think the added weight on the stern would keep the bow up a bit, and some of the fair extension would be in the water and add buoyancy. The rudder post is currently only 2 feet forward of the transom, about 1 foot aft of the cockpit deck. I don't care much about racing, only safety and comfort. Removing the entire cockpit deck and seats was not something I had planned on. That would complicate the job. I am beginning to see the magnitude of the job. I had envisioned a few main parts:
    1) Remove fore and aft cockpit seats.
    2) Move steering pedestal forward (not rudder post - it's rack and pinion).
    3) Mount pilothouse support posts.
    4) Cut off transom, embed stringers all around hull extending aft.
    5) Add sides, top and windows around this framework.
    6) Fair and finish.

    Something like that.
     
  5. RHP
    Joined: Nov 2005
    Posts: 791
    Likes: 71, Points: 28, Legacy Rep: 1183
    Location: Singapore

    RHP Senior Member

    You´re a brave man, I expect 99.9% of members of this forum would choose to purchase a larger boat - by doing extensive research you could minimise the price difference which would be recooped at time of eventual resale.
     
    1 person likes this.
  6. PAR
    Joined: Nov 2003
    Posts: 19,122
    Likes: 462, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    From a sailing lines and balance point of view, Eric is right, your best bet is to hack off the boat at the aft end of the keel, probably taking that little piece of fairbody with it. This means you'll lop off the last 1/3 of the boat and have to engineer a new, burdensome stern quarters. With so much additional hull added, you'll surely need a new rudder and hopefully the new aft quarters will offer some additional bearing area to support the bulk of the addition.

    The cost of a project like this will rival the purchase of another larger, used boat. It sounds like you want a 38 to 40' boat, like a Morgan Out Island 39'. You can find these in abundance in every condition. With the current market, deals are everywhere. You can find a fairly well dressed example with a desperate owner.
     
    1 person likes this.
  7. yorktownie
    Joined: Jul 2008
    Posts: 9
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Eureka, CA

    yorktownie Junior Member

    I am convinced. Chances are I would end up sailing in a fairly nice looking boat with a miner's shack tacked onto the stern, which the first gale would likely sweep away. I thank you all for the input. I really do want a larger boat.
     
  8. Nohona Mau
    Joined: Feb 2017
    Posts: 35
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Honolulu

    Nohona Mau S.V. Nohona Mau, Kaneohe

    Yes - I did it!

    So I was crazy enough to take a Yorktown 35' C/C sloop and add just over 4 feet onto the stern end. Actually, with this hull design, it was pretty easy - relatively speaking - by building a "form" (mold) out of 3/8" MDF that was temporarily screwed into the hull so that it extended the lines and contour of the original hull back - like wrapping a napkin around a cocktail glass - it projects the lines aft. Then I waxed up the form and laid in bi-directional Nytex 1708 fiberglass cloth (a pre-stitched set of 3/4 Oz mat and 17 Oz roving material). I ground down the original transom to remove gelcoat and expose raw glass roving so the layup would adhere to the original transom. I laid up the fist 2 layers throughout the mold and across the (original) transom, then set in a 1/2" think plywood bulkhead piece I preformed form two 1/4 Ply segments cut to the profile of the transom and glued together to match the form of the transom crown (cross sectional curvature). Attaching this with S/S screw to hold it in place, I then laid up the next 2 layers of Nytex and let it cure. Lastly, I placed S/S cartridge bolts thru the new bulkhead to give the new add-on a mechanical bond and two of them were thru-bolted to the rudder's hydraulic ram mounting plate to add structural integrity to the steering system.

    This created a "sugar scoop", and was the easy part - just peel away the MDF mold face and you have a rough casting of your extended hull shape. Note, the original transom was never breached, and the rudder and backstay chainplates remained exactly where they where originally located, so no changes to the rig itself.

    The next steps were more complicated, designing and fitting a new transom to "close in" the sugar scoop. I designed mine with a lot of curves and contours to create a void between a structural transom component and the external finished transom, so that the "finished transom" (what you see) actually is a false transom that flips down to become a swim step with a telescoping ladder which "parks" itself inside the void.

    The deck cap had to be done in a mold I designed/built, so that the original signature lines and contours of the boats hull/deck carries back to a graceful conclusion. This mold incorporated butterfly lazarette hatch openings for general storage and propane tank storage. The results turned an ugly duckling that - from a design perspective - was literally "cut short of it's prime" into a graceful swan - So many people comment "what beautiful boat" - they don't recognize it as a Yorktown. The hardtop dodger I added also complimented the look of the original hull.

    The Yorktown was designed with a reverse shear on the transom, with no overhang to extend the waterline length as it sails and sinks into the hole. Increases in hull speed was limited by the drag created by a plumb exit off the original transom. By extending the 33 foot waterline to just about 37', boat performance was significantly improved by reducing the turbulent drag present in the original design. It's faster on every point of sail, but especially on reaches and downwind runs - where 9 knots were nearly impossible to achieve, I now regularly hit the low to mid 9's in fresh Hawaiian trades of 20 to 25 knots of wind.

    Cost you ask? Let's not go there - this was crazy expensive when you take into account the time and effort - but it gave a new lease on life to a great comfortable cruising boat. Yorkies are a great foundation to build from! I love mine.....
     

    Attached Files:

    Last edited: Feb 2, 2017
  9. robwilk37
    Joined: Nov 2010
    Posts: 117
    Likes: 2, Points: 18, Legacy Rep: 24
    Location: san diego

    robwilk37 Senior Member

    mine was a bit less ambitious, the goal being to create a proper lazarette/propane locker. i left the original reverse transom in place and extended the hull lines as you can see. the simplest of molds with packing tape for a release barrier. the extension is glassed inside and out to to well-ground surfaces and all in 18oz biax/epoxy. really happy with the result, a ridiculous amount of work though...
     

    Attached Files:

    • 362.jpg
      362.jpg
      File size:
      370.9 KB
      Views:
      78
    • 372.jpg
      372.jpg
      File size:
      384.3 KB
      Views:
      147
  10. Nohona Mau
    Joined: Feb 2017
    Posts: 35
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Honolulu

    Nohona Mau S.V. Nohona Mau, Kaneohe

    :eek:
    Yes, sounds like we were both crazy enough to dive into it. Looks good, and nice to have some deck space back there. A little more on the waterline when heeling won't hurt either. Assume this was a Yorktown as well? Was it an aft cockpit model?

    Fun to keep this post alive, thanks for chiming in...

    Here's a pic of the my finished product at the Aloha Dock in Waikiki
     

    Attached Files:

    Last edited: Feb 6, 2017
  11. robwilk37
    Joined: Nov 2010
    Posts: 117
    Likes: 2, Points: 18, Legacy Rep: 24
    Location: san diego

    robwilk37 Senior Member

    yes, Y39 aft cockpit extensively modified. there where only 8 of them made as i understand it. aside from the gas lockers, it gets me increasing buoyancy in a following sea, pushes the back stay chains back for a little more main and eventually a nice fold down swim step to boot.

    cabintop mods in red...
     

    Attached Files:

    • 646.JPG
      646.JPG
      File size:
      49.5 KB
      Views:
      71
  12. Nohona Mau
    Joined: Feb 2017
    Posts: 35
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Honolulu

    Nohona Mau S.V. Nohona Mau, Kaneohe

    39 aft - I have never seen one of these.
    I like the new lines w/ the cabin change - looks like it gets you a bit more head room in the main cabin area too. Well done! Did you splash it yet?

    In previous threads they kept talking about changing the rudder position - I never understood why they thought it was necessary. The whole underbody is perfectly positioned and proportioned to allow for a significant deck level extension, and a good portion at the waterline (with an overhang). In your case, there's very little, so I wouldn't expect you'd notice any change in handling characteristics. In my case, it was quite a bit more overhang, about 2' at the waterline - but it's all flat and smooth, and it's had no negative impact on steering or handling whatsoever, but sure added to speed on off the wind and down hill runs...

    So, let's keep these old boats running... I think they are worth investing in.

    B
     
  13. Puma
    Joined: May 2018
    Posts: 1
    Likes: 0, Points: 1
    Location: Oviedo, Spain

    Puma New Member

    Hi

    Old thread, and been following this for a long time, this is my first message in this forum.

    I´d also want to lengthen my sailboat. Sails very well, but an extra meter of waterline and interior space would make it 99% perfect.

    You will say, "sell and get a bigger boat".

    There are lots of fat sailboats out there, it´s extremelly difficult to find a narrow low freeboard very low center of gravity and deep V hull, with good ballast/displacement ratio and without a huge 100% foretriangle.

    I´m in Europe, my sailboat is in pristine condition, if I sell and search for a narrow low freeboard longer sailboat it would have to be something like a S&S Swan 41 and it would cost close to 150000$ since my sailboat will only sell for 30000$, and I would still have a boat with a huge foretriangle.

    To sell and buy a Newport 41 in USA, bring it here, and leave it in excellent condition would not take much less. And again, still a too big headsail to singlehand.

    NEWPORT 41 Mk II sailboat specifications and details on sailboatdata.com http://sailboatdata.com/viewrecord.asp?class_id=2444

    For less than this money I think I can extend the length?


    PUMA 34/341 sailboat specifications and details on sailboatdata.com http://sailboatdata.com/viewrecord.asp?class_id=3664

    As you can see it´s an early IOR sailboat.

    J= 4.42 meters (14.5 feet), E = 3,35 meters (11.48 feet)....it is balanced. Mainsail size is only 230 sq feet (around 22 sqm)

    Imagine you add 1 meter of length, and finish all the lines nicely again.

    If I then just add a longer boom bringing the center of effort of the sails a little bit aft, wouldn´t I have it all again balanced?

    Since this is an IOR sailboat the mast is quite aft already.

    The 100% foretriangle size would be the same nice size for singlehanding (320 sq ft/30 sqm) just with a slightly bigger main with a longer boom ( instead of 230 sq ft let´s say 270 sq ft?).

    P is 12.10 meters (39.7 ft) and beeing E= 3.35 meters (11.48 feet) wouldn´t I have room for a longer boom with the mainsail still working properly upwind?


    The hull is 1 inch thick fiberglass, no osmosis. 20 to 25 layers of cloth depending.

    How much time would it take to make the hull cut? Is this really so difficult for a proffesional?

    For the hull it would be around 5 sq meters (54 sq feet) of new fiberglass, 1 inch thick.
    For the deck around 4 sq meters (40 sq feet) of extra fiberglass, this is around 1/2 inch thick.

    How much extra weight is this?

    For the basic structure (not just filling the gap, but bringing the 2 parts structurally together to sustain something like for example being able to be raised again via a travelift) how much time would it take for 2-3-4 professional persons working on it?


    I can do all the final finish (sanding, top coat, epoxy, completing the interior etc) by myself.

    I don´t care about the resale value as I intend to keep the sailboat for decades.


    [​IMG]
     
  14. Eric Sponberg
    Joined: Dec 2001
    Posts: 1,989
    Likes: 190, Points: 73, Legacy Rep: 2917
    Location: St. Augustine, FL, USA

    Eric Sponberg Senior Member

    What you propose is so drastic that you would change many of the design characteristics of the boat, and may end up with something that does not perform well at all. First, you will spend much more than $30,000 (your estimated value of the boat now) just to cut the boat in half and glass the hull and deck back together. And that is assuming that you can do that. By your diagram, where you propose to cut the hull, you would have a difficult time making an insert that could be properly faired to both the fore and aft sections. Then, of course, there is the interior to first rip out and then rebuild in way of the cut. Be prepared to have a naval architect advise you and prepare proper construction drawings, your builder and you will greatly appreciate it. Construction drawings give you an organized plan of what to do with technical specifications that are worked out in a good engineering way. If you do such a job without good technical advice, you'll be sure to make some critical mistakes. Consider also that after you add the extension to the middle of the hull, you rudder and keel may be undersized for the new hull shape and weight. Add modifications to those things to the overall cost of the project, they are not cheap. A naval architect can advise you in more detail. Personally, I would not recommend this kind of modification--you truly would be better off to find another boat that better suits your needs. Fair extensions at the ends of the hull are one thing, what you propose here is quite another and much more complicated than you may realize.

    To those of you who have missed my postings (few to none over the last 2 years), my wife and I are alive and well on our sailboat, Corroboree, currently in Nuku Hiva in French Polynesia. We are on our way across the Pacific Ocean bound for Tahiti next, then the Cook Islands, eventually Fiji and then New Zealand. We hope to be in NZ by the end of this year, and expect to stay there for a few months to see the country and to do a refit to Corroboree. To follow our travels, you can connect to my FaceBook page (Eric Sponberg) and read my wife Arliss' blog at The Old Woman and the Sea – Arliss Ryan https://www.arlissryan.com/blog/.
     

  15. PAR
    Joined: Nov 2003
    Posts: 19,122
    Likes: 462, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You're half way across my friend, congratulations. I hope the ride was uneventful and the boat doing well. Given our respective ages, my other half will likely take offence at the title of your wife's blog. She's not ready to concede and is still firmly in age denial, much like my baldness denial I suspect.
     
Loading...
Similar Threads
  1. DC Landis
    Replies:
    6
    Views:
    1,257
  2. ghost13
    Replies:
    9
    Views:
    2,262
  3. JustinT
    Replies:
    15
    Views:
    2,064
  4. mdem
    Replies:
    4
    Views:
    1,389
  5. jim lee
    Replies:
    0
    Views:
    1,109
  6. utatuka
    Replies:
    6
    Views:
    2,105
  7. arosental
    Replies:
    21
    Views:
    8,096
  8. mccdeuce
    Replies:
    6
    Views:
    3,815
  9. gelj34
    Replies:
    3
    Views:
    1,467
  10. pierre2mars
    Replies:
    14
    Views:
    2,440
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.