Hobie Hulls (buyer's remorse)

Discussion in 'Multihulls' started by Owly, Feb 22, 2020.

  1. Owly
    Joined: Oct 2016
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    Owly Senior Member

    Last summer, I concluded that the easiest way to do the amas for the canoe trimaran I'm getting ready to build....... slowly.... was to simply buy a pair of beach cat hulls. I found a pair of Hobie 14's and hauled them home...... Basically $100 for the entire Hobie without a mast or sail. The rudder assemblies alone were worth considerably more than that to me. I had quite a time knocking it apart, hundreds of miles from home, and loading it on my Outback. I cut the tramp out entirely...and left it, but hauled everything home. In the process of knocking the cross beams off the posts on the hulls, I managed to crack two of the castings... Not a big deal as I will not be using the aluminum beams, but I do need to work out an attachment. I'm pretty good at such things.
    The issue I have with these hulls is the weight. They are far heavier than I could have made them using stitch and glue or skin on frame. I'll be using them anyway......... initially at least, but I'd say they are double what I think they should be. They are not waterlogged unless they are filled with water saturated foam??? I don't know what's inside.......Anybody??? I'll probably install access ports (strategically), and try to figure a way to reduce weight. I'm not too hopeful on that front.
    ........... Suggestions anybody? Experience? Please no lecture on how I should have just built stitch and glue amas...... One sheet of plywood would be more than I paid for the whole thing. I'm having some regrets, but the reduced cost and time are significant. I expect to have it in the water as soon as the weather allows.

    H.W.
     
  2. bajansailor
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    bajansailor Marine Surveyor

  3. Owly
    Joined: Oct 2016
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    Owly Senior Member

    I'm getting 78 lbs ..... it's difficult to weigh them accurately, but that's what I just weighed one at. I'd really like to be closer to half that weight, but obviously that's unrealistic with factory hulls. I believe I could build stitch and glue hulls at around 40. It I'm happy with the boat, I'll probably eventually do that. The plan is to end up with a canoe tri sailing camper ...junk rigged, with a pair of side decks between the beams for sitting / sleeping / camping, probably made from foam and glass. The decks will overlap inside the canoe, and be built as light as I can make them. My application is far different than the original mission for these hulls, the stresses far less, so they are really a non-optimal choice. I'm wondering if I can open them up and remove the foam. While there is no indication of water... aside from weight, that weight is coming from somewhere. Weight is a killer on any multihull.........
    I'm not looking for the thrill ride most folks are after with beach cats, what I want is a more relaxed sailing on the huge inland reservoirs out here, anchoring in small bays for the night, camping under a boom tent, exploring and perhaps fishing a bit. Not that I will not push things hard for a thrill once in awhile.... do we ever outgrow that ;-) ?

    H.W.
     
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  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Have you considered making an all foam design like Dierkings? I can't imagine them weighing forty pounds wet.
     
  5. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    I agree, cut out a six inch inspection hole and get the foam/water out of there.
    Should be easy to weigh, just hold them, one at a time and then subtract your body weight, no?

    How about a cat instead of a tri?
    Same deck space.
     
  6. trip the light fandango
    Joined: Apr 2018
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    trip the light fandango Senior Member

    If the bottoms/ keels are the same as 16s they are solid glass, the foam starts about 3 inches up, that,s pretty heavy and strong , if you drilled a series of small holes in the inside skin at this point you could be sure the foam had the ability to shed water into the solid glass bilge, access to do this is problematic , The posts probably weigh 8 lbs each but removing them requires big enough access holes in the deck [one each side of each post] to do the surgery. They are probably overkill for a canoe main hull. the flange where the deck meets the hulls is the strongest point otherwise and could be used for the beam attachments[if it's the same as hobie 16/18 lay ups] . I don't think you can remove the foam without making the hulls flimsy and soft. They're a bit heavy but very tough and you have saved yourself a fair bit of work, especially if you use them as they are. try warming them up[caps off] and see if they get lighter. I hope this helps.
     
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  7. Owly
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    Owly Senior Member

    I'm not familiar with the design you mention, but yes, I've considered making floats entirely of blue XPS, assembled from vertically laid planks, one being the keel piece, and each one after that being slightly different contour like a topographical model. I'd probably lay light glass & epoxy between some of the layers.
     
  8. Owly
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    Owly Senior Member

    I actually have thought seriously about doing the surgery you describe........ but I have no idea what's inside. The posts are not convenient for what I'm doing.......... these are really beefy. I don't know how much the internal foam contributes to strength..... at least for my purposes. I'd like to not have it at all. If I dug it all out, judging by how the layup feels knocking on it, I suspect it would be plenty strong. Can you tell me what the internal structure associated with the posts is?

    H.W.
     
  9. Owly
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    Owly Senior Member

    I'm obviously not changing course at this point. The tri layout offers some things I want. There will be stowage in the main hull for camping gear, the side decks will be comfortable to sit on with your feet in the hull, when at anchor, or when sailing, just slightly hiked out on a tack. The mission as I said, is to be a sail camper for exploring, rather than racing around pylons and such.
    H.W.
     
  10. Owly
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    Owly Senior Member

    I just found a cut away photo of a Hobie 16 hull showing the block of foam, and also the pylon, giving a good view of how it's attached.... Not very impressive, and it's clear in the photo that the foam is just a block of cheap EPS (bead board), which could easily be dissolved out of the hull using solvent (gasoline for example), and offers little if any structural support, as it just lays in there, rather than being molded in EPS does become waterlogged.
    The pylons are really too close together for my purposes. Presently I'm thinking that I should just remove them, and choose my locations, simply placing plywood frames in the hull that project through the deck, one on either side of each beam (aka). These would probably be 1/4" marine plywood, and they would be tabbed into the inside of the hull using the typical method of creating a radius with thixotropic epoxy resin, and following that with glass tape as you would a bulkhead in a plywood boat. Each ama will have two short beams that will be attached to the main beam assembly in the canoe, designed to allow the ama to either be folded up over and lay on the side deck for transport, or just be removed. The beam assembly on the canoe portion will incorporate the side decks, which will be tabbed into the gunnels, and into both beams, and a longitudinal piece of wood at the outboard edge to both provide stiffness and support for the assembly and the deck itself, and block some splash.
    I was planning to make a set of leeboards that would fold up beneath these side decks to avoid having to build in a centerboard trunk.... it's tempting to use one of the rudders I got with the Hobie for that, but it's also tempting to put the rudders in their intended locations on the two hulls, and simply use the original Hobie configuration... lengthened because of the increased beam....... They are really well designed kick up rudders with a well thought out linkage and kick up mechanism. It would be a shame to reinvent the wheel so to speak......... I'm going to have to invent plenty as it is...........

    Forgive all this talk.......... I'm a guy who builds something dozens of times in my mind down to a great deal of detail before I build it in real life. It saves time, money, and frustration if the details are worked out in advance.

    H.W.

    https://www.thebeachcats.com/galler...ownloadItem&g2_itemId=10753&g2_serialNumber=7
    [​IMG]
     
  11. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    56D090F9-9FBF-4859-B80C-738E1742341D.jpeg
    I would not bother holing those. Use gravity and lean the hulls up in the air and see if any water ends up at the bottom. I doubt you will get much. Foams generally get saturated inside the open cellular structure and the water can't leave. The edges of the foam can dry, but drying the entire foam is next to impossible. I experimented with saturated styro hot tub covers. Put them in an overly heated room for a month and weighed them in and out and they lost a stunning 2 pounds, but were still far too heavy to reuse. Most of the water remains in the foam. The drying efforts are thwarted by microscopic atmospheres of damp air and tiny molecular trappings of water. Saturated foam is a lost cause.

    The Dierking designs do not require glass in between. You use foam glue; which is cheap purchased in the big gun tubes. You lay light glass on the finished part. These are fun to build, but a bit messy.

    Here is a set of 6 footers for a canoe outrigger we use to keep our canoe from tipping in 39 degree waters. I used 6oz glass and they need some paint now. I started to fair them and decided why bother adding weight.

    The xps is a bit of a pain to shape, but not impossible.
     
  12. Owly
    Joined: Oct 2016
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    Owly Senior Member

    I intend to remove the foam......... it's simply not needed. I may dissolve it out using gas. The pylons are going to be removed......period. I've reached that conclusion. They are poorly spaced for my purposes, and they are heavy.
    On further reflection, there really is no value in glass in the center of a foam construction... it offers no real strength. The foam core principle is like an I-beam, the load bearing material at the extremities where it needs to be. Foam has essentially zero structural strength, but has value as a core material. I know that, and yet tend to "backslide" for some reason.
    Your floats look fine to me......... Nothing a sander can't finish out. I'm looking at floats with the ability to support a great deal more weight, as I want to be able to step ashore via stepping on a float without sinking it. I'd like some reserve buoyancy...............

    H .W.
     
  13. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    How does that work?
     
  14. upchurchmr
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    upchurchmr Senior Member

    This a very bizzare thread.
    Hobie hulls have closed cell foam.
    Water does not "soak" into the foam.
    The foam that is used does separate from the glass with age.
    There might be water between the foam and separated foam - but if that is true, the hull is basically worthless.
    You can inject epoxy between the skin and foam to try and reattach the skin/foam at a large increase in weight.
    AND, the foam itself is degraded, so it will eventually just separate again.

    The foam is necessary for the hull to have the designed strength.
    If you removed the inner skin and the foam to reduce weight, the outer skin that is left will have a very reduced stiffness.
    You wouldn't want to have the hull fold up when out on the water.

    Just use the hulls you bought - IF there are no soft spots in the skins.
    Come back later and build the hulls you really want.

    I'd be willing to bet (sight unseen) that the hulls have soft spots. This is typical of all old Hobies.

    Good luck.
     

  15. trip the light fandango
    Joined: Apr 2018
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    trip the light fandango Senior Member

    Well having bought old hobie hulls with soft spots and spent months working on alterations , I'd disagree that they are worthless...ha. Upchurchmr is quite correct in saying if you remove the foam the hulls will go floppy and look terrible,I think. You could remove nearly all the deck by cutting away large portions about 2 inches inside the flange[see photo] leave braces[ you could glue on rubber c channel to cover your cuts] and reinforce them [the cross braces]with triple layers of the material you cut away and glass these into place , similar to your canoes thwarts, and where you will mount the beams. The braces should be strong enough to pick up the hull with or walk on, lightly glass in loops to strap in the foam blocks. Thin mixes of microballoons can help delam.
     
    Last edited: Feb 23, 2020
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