Uniflite hull extension

Discussion in 'Boat Design' started by AK-uniflite, Jan 24, 2007.

  1. AK-uniflite
    Joined: Jan 2007
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    Location: Ester, Alaska

    AK-uniflite Junior Member

    Hello everyone,

    I am new to this forum, and I wanted to get some opinions and ideas on a project I have. I own a '74 Uniflite 31' Sport Sedan, she has been partially submerged and is in need of a complete refit. While I absolutly love boats, I am not financially able to drop $50K for new Yanmars or Cummins, and a billion other parts for the cabin, etc, and THEN be able to afford to fill the tank on a weekly basis, probably getting around 1 MPG while I am out. So my idea is this; I have already decided on raising the front half of the cabin to a foward sloping pilothouse type design, the old Uni's did not have great visibility from the helm. (Note, my boat is one of the very few of this model that did not come with a flybridge on the roof) This part will be pretty easy. What I really need ideas on is the hull and the power. I am considering extending the hull 8-10 feet to make a large rear deck, more storage, fuel capacity for longer range cruising, and a more efficient hull. I would like to power this as a displacement hull, with maybe a single 5.9 Cummins. If possible, I would like to round out the hull extension to make the hull more efficient. The original 31' hull is a planing V hull, not sure of the deadrise out of memory. Beam is about 10'5". Is this a ridiculous idea? How would the boat handle? (assuming a good design on the ext.) What kind of material is the most economical (and strong) to use. Uniflites are a very heavy, thick, fiberglass construction. I am still very much in the idea phase, and looking to start making more of a plan for it. Another note, the boat as it sits has cost me $5000, so I am not risking a lot to start. Thanks a lot for any tips, ideas, etc..
     
  2. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    I am not a great fan of hull extensions. They tend to exxagerate any flaws that the boat already has. It has been done many times successfully by companies such as Hatteras, but they have a large design staff and experienced technicians to do the work. And typically when a a boat builder adds an extension it is not to an existing boat. They just build a new boat that is so many feet longer but is based on the shorter design. They don't normall just tack a few feet on an existing boat. This is because it adds new stresses, changes the centers of gravity and buoyancy, changes the pitch roll and yaw chacteristics, and the stress is concentrated at the poitn where the extension was added.

    I spent almost three years corresponding with a boat owner and the boat manufacturer over a boat that had been extended only 2 feet. The extension was literally falling off, and it was also causing big structural problems with the rest of the hull. Eventually the boat had to be scrapped and over 200 identical boats had to recalled by the manufacturer.

    The Coast Guard has a fleet 110 foot patrol boats 10 of which they had extended 13 feet. This was designed by professional naval architects, and done in a professional shipyard. Now the bows are falling off and they had had to tie those 10 boats to the dock until they can figure out what to do with them. (your tax dollars going to waste)

    So I suppose you can see why I am not a big fan of hull extensions.

    However, I am sure there are others on this forum who will disagree.
     
  3. AK-uniflite
    Joined: Jan 2007
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    Location: Ester, Alaska

    AK-uniflite Junior Member

    I can certainly see where you are coming from. I am not terribily worried about structural issues at this point, perhaps because I don't have a clue tho. I am figuring on leaving the existing transom in place as a sort of bulkhead, and by sistering up to the exisiting stringers (2x8 I think) I think I can keep the boat rock solid IF I use the right materials. Once again, I am only planning on running at displacement speeds as well. I have heard of Padden Creek Marine doing many extensions on the 42 and 48 foot Uniflites with no problems. They also cost a ton of $$ though.
     
  4. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    AK, Just find another Uniflite 31 and bolt them togather at the transom. I believe they have a warped hull, so with a little fairing in the "middle" you could have a perfect canoe. A single engine should easily drive it at displacement speed, and you could have 3 spares. Dont let anybody tell you that it cant be done, and remember that brute force and ignorance will always prevail over intelligence and planning...
    Seriously, though, I think an extension of 5 feet of less and a tunnel for the single prop might make an economical cruiser out of that hull. The cost of the project is another matter. You could probably buy a lot of fuel for the cost of the mods.
     
  5. AK-uniflite
    Joined: Jan 2007
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    Location: Ester, Alaska

    AK-uniflite Junior Member

    What kind of materials would be best to do this with? I was thinking a plywood core with glass???
     
  6. scott steffe
    Joined: Jan 2007
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    Location: port charlotte fl

    scott steffe Junior Member

    you need to use way better stuff than wood
    arora matt core and penski board stringers or a composite of 10 lb density
    24 lb for transums
    uniflights has a huge delamination history not worth all the effort in my opinon
    they tried some years ago to develope a fire retarded gel-coat that never worked very well
    you should look for another hull entirely
     
  7. AK-uniflite
    Joined: Jan 2007
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    Location: Ester, Alaska

    AK-uniflite Junior Member

    Not any delam problems with this boat. And it is prior to the years when they started having problems with the fire retardant in the resin. Although, I am starting to think about getting rid of it and start building a steel Diesel Duck 48.
     
  8. charmc
    Joined: Jan 2007
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    Location: FL, USA

    charmc Senior Member

    Had a little experience replacing a rotted transom that was plywood core. Most definitely forget the plywood; there are marine rated composites for core material, as suggested above. I admire your courage in taking on the project. Without discouraging you, though, I must point out that there are 36' Uniflites available on the West Coast in reportedly good condition that can be bought in the thirty thousand dollar range (Try everyboat.com, for example). Careful inspection and some judicious negotiating might get you a boat in good condition in the size range you want and within your total budget. Running at displacement speeds will give you years of use, good fuel economy, and the option to run at speed from developing bad weather.

    At the end of the day, your project would take a Uniflite 31 and turn it into a home-built. Not automatically bad, but be sure you really want to take on that responsibility.... and if you do, be rigorous in seeking out and using only the best materials and procedures. Good luck!
     
    Last edited: Jan 30, 2007
  9. bspmarine
    Joined: Jul 2007
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    Location: California

    bspmarine New Member

    I love this Uniflite

    Are you still considering selling your Uniflite? The model you have is an awesome boat just as it is. You made a small mention of getting rid of it. If that's what it comes to, please let me know. These 31's aren't that easy to find. Thanks,
    Brian
    bspmarine@gmail.com
     

  10. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

     
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