Hobie Hulls (buyer's remorse)

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

  1. fallguy
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    fallguy Senior Member

    there is nothing to power sand, if power I sand, I will remove the 6 oz glass I used to enclose the amas, a light hand sanding of any chalking might be done if I decide to paint them someday soon; I just shared so you can see a basic concept, you can google for more

    Obviously, you need larger floats, but some Dierking has made are pretty large. I think he may have used a piece of plywood up the middle of the long ones to give them some rigidity and a backbone for connections. They basically would take about a week to build, longer if you want to fair them nice. And you could easily calculate the weight long before building and see if they would compete with strips

    afa the thread, if you are unhappy with the Hobie hulls, then all the rest of us can offer is options, perhaps the Hobies use a different foam than Boston Whalers...the Whalers do become saturated...wet foam is a lost cause
     
  2. upchurchmr
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    upchurchmr Senior Member

    You can patch up anything.
    You will have no idea just how strong what is left will be.

    You might as well have made your own hull of a similar shape.

    Good luck, again.

    PS, I have cut up several Hobies, using masts, etc for other boats.
    The foam does not soak up water - no matter what other boats have used.
    Anyone else actually cut up a Hobie and found soaked form? The foam in the hull lamination.

    I agree, wet foam is a lost cause.
     
  3. trip the light fandango
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    trip the light fandango Senior Member

    Hobie uses polyurethane foam ,it's easy to shape, polyester adheres to it and it does dry out. Mud or salt could get in if saturated long enough and that could add some weight ,but there would have to be some delam one would think. The inner skin is only just wetted out and could be porous in places , repeatedly scrubbing or flushing the inside may eventually lighten the hulls overall, when they've completely dried out. The beach cat forum may be the best place to get well informed answers..
     
  4. trip the light fandango
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    trip the light fandango Senior Member

    I have found slightly damp foam,it will dry out. Considering the longevity of polyester and polyurethane foam that is in good condition [no delam in critical structural areas ] the hulls will be as strong as they were when they were new, slightly harder with slightly less flex I'd wager.
     
  5. Owly
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    Owly Senior Member

    I've handled the hulls quite a bit, and not detected any soft spots.......... Looking at the photo I posted, the hull layup appears that it might have a foam core.......... The foam inside the hull is a different thing entirely, and that foam is essentially garbage as far as I'm concerned, and being expanded polystyrene per the photo, will suck up water over time if it has the opportunity. Core foam is entirely different material, and as you say, if it delaminates the hull is garbage. I haven't gone over it with a mallet looking for delamination signs. Structural core foam and floatation foam are two separate issues.

    H.W.
     
  6. Owly
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    Owly Senior Member

    There seems to be a miscommunication or misunderstanding here about foam..............Core foam and flotation foam are completely different things, and entirely different foams. In the photo I posted you can see what looks like a thin core foam....... and also a big block of EPS flotation foam. The core foam in structural, and that is not what I'm concerned about, The cheap EPS flotation foam is able to easily absorb water, and has no value to me anyway, as it clearly is not structural. That should be obvious from the photo...... assuming my hull is built the same as the one in the photo.
     
  7. Owly
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    Owly Senior Member

    Structural engineering 101...........
     
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  8. trip the light fandango
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    trip the light fandango Senior Member

    If[ a big if] you could dissolve it the matt and resin will still hold it together and it is a higher density polyurethane block I think...?, I doubt very much that you would need to increase the length of your rudders, less sail area, load , more width will increase their ability and less weight. I wonder if others would agree with that last statement though, don't try and remove the foam sandwich, you will have wasted the drive and money. The hobie hulls will sit higher than usual [less drag] because your centre hull will be in the water, which brings up the question of dihedral, do you want the drag of 3 hulls in the water or will you flop from side to side a little when you move abeam? You might consider selling the hulls before you wreck them for other peoples purposes, they seem big and heavy for a canoe and your requirements, Someone will use them for a dive platform maybe. I think they are ok for your use though..Edit
    the floatation foam you are talking about is polystyrene and wont absorb water until it is floating in it for days, because it isn't sealed it will dry out and weighs next to nothing and stops the hull from sinking if you get a hole and fill with water, I was referring to the block at the bottom of the post. I've misunderstood which foam you been talking about , a couple of times , sorry
     
  9. Owly
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    Owly Senior Member

    I clearly was wrong about soft spots........ not knowing that the hull was cored. I examined them carefully this afternoon and they clearly are suffering from a case of delamination I can push on the sides of the hulls with my foot, and feel and hear the fiberglass tearing free from the foam core as it flexes, and it does not take much pressure. As they are, they are adequate for my use....temporarily. An inner and an outer skin not working in concert through a bond to a core is kind of useless structurally. Removing the inner layer of glass, and the core would leave a flimsy thin shell. And of course that is not realistic anyway, as the entire deck would probably need to be removed. Any direction I look, I see work and cost for questionable results at best. I have a couple of ideas, none of which is really practical. Any investment of time and / or money is at this point in the category of throwing good money after bad ;-(. The best course is probably to proceed with my build with the hulls as they are, removing the pylons as I intended, and get a season of sailing out of it while planning the build of the new hulls.......... The title of this thread is becoming more appropriate ;-(............ A season of sailing it will give me a good idea of what I want in hulls, as opposed to building hulls and finding out that they are not optimal.

    H.W.
     
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  10. Owly
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    Owly Senior Member

    It was my error, as I didn't realize that the hulls were cored until I found the cutaway I posted today........ Core foam obviously is not dissoveable, and you are right about EPS not absorbing water until it sits in it for a considerable amount of time. I don't consider the hulls to be of any value to anybody under the circumstances.... unless like myself they are ignorant about the construction. I had assumed that the flexing of the skin to be normal flexing of a fiberglass skin..... until today. As it stands the rudders and hardware are the value here, not the hulls. I could not begin to build rudders for what I paid for the works. The engineering, and hardware, etc were well worth my hundred bucks. There is no way to come out smelling like a rose at this point.......a pair of rudders and hardware, and a lesson............. that's worth something.

    H.W.
     
  11. trip the light fandango
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    trip the light fandango Senior Member

    Owly if you pushed on the sides of new hulls you might hear tearing, the inner skin is designed lighter and wont tolerate that, you are creating more work, anyway good luck with it .
     
  12. Corley
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    Corley epoxy coated

    You can clean the old core foam out and vacuum bag new foam onto the outer hull shell from the inside. It's neither quick nor easy though and nearly as much work as building a new hull. The positive is that you keep the shape of the outside of the hull so you do have a faired outer shell to work from and your inside glass work only has to be structurally adequate not aesthetically pleasing.
     
    Last edited: Feb 23, 2020
  13. Owly
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    Owly Senior Member

    Sounds like a lot of work and expense to me. It does bring up one important point, and that is retaining the finished exterior. These hulls are over strength and over weight for what I want to do. Removing the decks could be a substantial challenge........ I have no idea what adhesive they use, or if it could be loosened. The cut away shows some sort of orange goop, and it looks like they applied it to the inverted decks generously, then plopped the hulls down into it. Boat builders are famous for poorly bonded decks........ but what is the chance of being able to separate this without destroying something? One alternative solution might be to remove the inner layer of glass and foam, and bond some stringers and lightweight bulkheads perhaps raw XPS to hold it's shape, creating a sort of skin on frame construction from the outside in......The question is how much stiffness do I need for this application, and is it possible to reduce weight significantly.
    I don't consider the hulls in this condition to have any significant value at this point...... I'd probably give them to someone if they expressed interest. It was not the bargain I imagined it to be a the time of purchase. The treasure of course is the rudder assemblies, and that is no small thing. The hulls as they are will serve for the initial build, as a starting point. If I destroy them, I have nothing. The pylons are coming out shortly, as they are useless weight to me, not a suitable structure to connect the way I want. The hulls are outside right now, and the weather sucks, so today I'll take one into the shop and play with the hull deck join a bit to see if it will yield without destroying hull or deck. I'll also cut out around the pylons, and remove them...... or at least try.

    H.W.
     
  14. trip the light fandango
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    trip the light fandango Senior Member

    Dont try and separate the deck and hull join, you seem to have missed this post

    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. You also missed most of the strength is in the flange , use this to secure your beams .
    The surgery requires a careful approach with an angle grinder and thin disk and a sabre saw, perhaps use lanolin as a cutting compound. leave some of the block looking tidy, it's not worth the delicate operation to extract.
     

  15. fallguy
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    fallguy Senior Member

    Say what?

    How does that not get even heavier?
     
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