Skin-on-Frame Surfyak ('sofistry') - Design / Build

Discussion in 'Boat and Accessory Building' started by mick_allen, Mar 2, 2007.

  1. mick_allen

    mick_allen Paddler & Moderator

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    absolutely love too! i am going to have to start searching places out. jordan river also - will need some input on when and where, etc.


    absolutely sof construction.
    but i worry that aside from being able to bend the wood to the desired curves (mostly solved), that this will be the most difficult problem to effectively pull off.

    i have a bunch of ideas that will be successively tried out but i have no idea what the end process will be. The operative word here is 'effectively' successful - ie to display and emphasize the lines of the kayak:

    • one possibility is pulling the skin more sideways that lengthways (wrt the yak)
      another is to ensure that the p/u coating adheres along all the stringer lines
      another is to employ a process like 'rib-stitching' that is used in fabric aircraft to ensure that the skin does not balloon at low pressure areas (ie wing upper surfaces)
      another is to do the complement of ribstitching and pull the fabric down halfway betw the stringers by sewing to false stringer/riblets that align w/ the stringers but go under the ribs.

    and there are a couple of other more unorthodox ideas that hopefully i wont have to employ


    .
     
  2. DarrenM

    DarrenM Paddler

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    Lots of rocks...
     
  3. mick_allen

    mick_allen Paddler & Moderator

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    nfg, if it's difficult to miss them! are there areas that can be used and yet not punch into the hard stuff?
     
  4. DarrenM

    DarrenM Paddler

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    The whole beach is round river type rock (most of the year) so that's not too bad. But if I remember correctly there are several boulder size rocks just under the surface. Plus you have to deal with the surfers.... Back in "the day" they would burn cars....

    There are other near by sandy beaches that you could hike to with a light boat.

    Better off going to long beach. Lots of space, and next to no rocks..

    just my 2cents
     
  5. DarrenM

    DarrenM Paddler

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    Or....
    You could come down and meet me here on Friday :p

    [​IMG]
     
  6. Astoriadave

    Astoriadave Paddler

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    Mick, on RC aircraft with "concave" areas, we found that using the heat-activated-adhesive on the back of the coating material to get a good stick (using an iron, not a heat gun) to the supporting framework, then applying gentle heat with the gun to shrink up the open areas of coating (mylar or polyester fabric; take your pick) was the best we could do.

    The other trick is to lay on the fabric so the bias lies across the boat, giving you the most crosswise stretch for the least lengthwise tension.

    After that, I suspect divine intervention might be goos ... :wink: :roll: :lol:
     
  7. Mark_Schilling

    Mark_Schilling Paddler

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    JR is ok - no sea stacks or large 'rock gardeny' type obstacles to speak of, but as Darren mentioned, the floor is two-fist-sized and larger rocks. I think the beach is also relatively steep, creating sets of only one or two breaking waves at a time.

    Renfrew is ok too; the beach is maybe a little less steep but sandy. The outflow of the river can create larger sets, but as with JR, a lot of the time the waves are nothing spectacular.

    If you want to almost guarantee waves big enough to surf with any degree of success, Long Beach is worth the trip (if you can make a long weekend out of it). Plus, the rock gardens around that area and more marine mammals make it the kind of place that gives you lots of paddling options, depending what you're into on any particular day.

    If you can get away for a few more days, Cow Bay on Flores is very nice, and probably much less busy (although I've heard that hard-core surfers will group up and run out there in a power boat for the day!). The bay is curved enough that there can be conditions anywhere from no breaking waves at all to huge, steep stuff at the same time just in different areas of the bay. The beach is a little steeper than Long Beach but you still get good surf and can usually carve off the wave before you hit bottom.

    Hopefully I'll know a few more ideal places after the middle of June. :wink:
     
  8. mick_allen

    mick_allen Paddler & Moderator

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    darren,
    where the heck you going? looks serene and beautiful, but the yak just can't get ready in 2 days!!!

    mark,
    good info, i am going to be looking real hard for good places and opportunities. for one thing, i need to try to get in some kind of pseudo shape!


    astoriadave:
    aaahhhhhhhhhh! you bring back old memories of my first forays into yak design. this is the 2nd or 3rd model i made during trying to design a strip built short kayak. for the model, i just built some forms and a couple of stringers and hotironed the shrink fit heat activated polyester fabric. actualy got some concaves around the foot bumps!!

    [​IMG]


    amazing, amazing stuff.


    but the problem with nylon or the poly used for skinyaks is that they do not shrink anywhere near as much, so i will have to be that much more careful.

    .
     
  9. Astoriadave

    Astoriadave Paddler

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    Yeah, the polyester fabric RC modelers use really shrinks up. I think it must be a special material, although the homebuilt aircraft supply houses may sell a heavier version that might work. The stuff used on RC models is probably too light, although maybe it would be OK on the deck (but not the hull).
     
  10. mick_allen

    mick_allen Paddler & Moderator

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    hmmm, hmmm, hmmm, hmmm.

    Daren Neufeld suggested that i use some of the 26oz i have for the hull and the lightest other cloth for the deck. This seemed like quite a provocative idea to have a more durable surface for the hull. Since weight is a big issue, it's a saw off either way.

    but the general idea of using diff cloths in diff places appeals to me in this situation AND the idea of using a highly shrinkable polyester (ceconite etc) airplane covering for the deck just might be absolutely perfect!

    one more idea in the quiver - thank you very much dave! I may not go with it, but it is certainly worth investigating.

    now, where can i get a couple of yards of this stuff to try out in the lower bc mainland (i know i can prob buy from 'aircraft spruce' etc)?


    I do think that i will probably have to stitch it down to a degree - the issue with thinner cloths is whether they are robust enough to take it.

    whatever the case, sounds great and thanks!
     
  11. Astoriadave

    Astoriadave Paddler

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    Yeah, you might have to put "backing" patches on the outside, where you stitch through, so the fabric won't tear. I think I've seen this on fabric-covered full-size aircraft. Or, I could be spaced out again! :lol:

    Sure is fun to see your project, and brainstorm solutions to these little issues. That thing is really going to turn heads, on the cartop, and on the water.
     
  12. DarrenM

    DarrenM Paddler

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    Sorry to derail your topic Mick.. Does anyone know what kind of boat this is?? Looks like it be fun in the surf.

    http://www.cesiak.org/kayak.htm
     
  13. mick_allen

    mick_allen Paddler & Moderator

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    topic? topic? there is no definitive topic in this thread - maybe the thread threading can be the topic, heh heh.

    i like both that kayak AND the double shown just below. They do look like old school ww rounded yak meets surfkayak and may therefore be a little more predictable. the short one does only look to be 9-10'.

    can't quite read the writing on the side. good one.
     
  14. Iwannapaddle

    Iwannapaddle Paddler

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    Whooo - from the photos on the "Build" pages Mick and D really had some sofistry-fun this weekend ? :lol: :lol:

    You guys are amazing - this is one exciting project
     
  15. sage

    sage New Member

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    a few qestions on the hull.

    On carbon/Kevlar and the new roto-molded surf kayaks we need to put in a foam core or a honeycomb core to stiffen the hull. The reason for this is any flex or movement in the planning portion of the hull bleeds off your speed. How do you propose to deal with this problem?

    Additionally on modern HP surf kayaks we have a 1/4 inch deep by
    2 1/2 -> 3-inch wide chine on the rails. This allows some forgiveness on your beach side rail. This will keep you from window shading (tripping) on your shoreward rail when changing rails or if there is a little chop on your green face.

    Any idea on your target weight yet? The lightest commercial boats are about 17 lb with the foam outfitting.

    There are several people on one of the forums that I hang out on that would love to take it out for a spin!

    http://www.boatertalk.com/forum/SurfZone/1241991

    Sage
     
  16. mick_allen

    mick_allen Paddler & Moderator

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    hi sage

    i/m just going to have to accept the bowing in of the skin between the rails and the stringers. Going across the width of the boathull i have the 2 rails plus 5 stringers in between. For a skin on frame that is quite a bit over the short distance - for a true surfer, it won't be optimal.

    a compromise - but that's how a sof works.

    and as well, it is an aesthetic decision - some sof's have stringers that are more wide than deep. I could have chosen that way and used 1 1/2" wide by say 1/2 deep stringers for an even flatter hull. I chose not to from the beginning because i wanted the appearance of the frame to be as unified(ie using one type of stringer) as possible.

    the stringers are just made to provide something like this. in the front part of the yak, i will make sure that the rail and first stringer provides a more forgiving condition - the bottom is more rounded. however the stern portion is dead flat.

    i have no target weight. My guess is that it will be in the low to mid 20's.

    part of the weight issue is trying to decide on cloth thickness. It will be unlike other sof's in that it will be quite stiff because i have quite consciously made a complete deep frame where virtually all the stringers run from the front of the yak to the stern unlike typical skin on frames.

    typical sof's have about 7" of struc depth over 17+ feet. this one has 12 " struc depth over 9 feet with more full length stringers. we'll just have to see how it all turns out. This kayak is quite big at 9' x 26", so it should be able to get up on some waves hopefully.

    anyway, i/m having fun building it and i think it will only get better.
     
  17. sage

    sage New Member

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    sounds good

    A bit long for a HP boat but it should perform better than most IC boats or better than most boats built before 97.

    I can't wait to see the pics of how you build and install your fin boxes.

    I wonder how a hybrid hull would work? Maybe stitch in stiff foam panels between the hull stringers? Maybe backed by door skin? I would be worried about trapped moisture with those ideas. Just a thought for the next design.

    Sage
     
  18. mick_allen

    mick_allen Paddler & Moderator

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    Yah, i don't want to go too small here. As i am a little heavy, i want all the chance i can get to get up.

    If it becomes just a 'P' boat, i'll be happy, heh heh. The 'H' will be for my other hardshell yaks, but i'll even keep them largish.

    i'll try to go as simple as possible as that is what a sof is about - but i have all kinds of ideas along the whole range of possibilities. i'll just try the simple ones. (others for the hardshell s&g's)

    note that the whole idea is to do it as a regular sof - using a skin and a ribbed frame only.
    there is no doubt that a composite kayak is more suited for this type of kayak and weight. the fun here is to see if it is possible to something that works somewhat but that also is a sof. that's the joke!

    .
     
  19. mick_allen

    mick_allen Paddler & Moderator

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    In other threads, we've talked about using syringes for various epoxy situations.

    I use syringes big time because of their ability to accurately place epoxy. But often i want to place large glue lines of thickened tinted epoxy and squeezing the thick mixture thru the tiny needle would end up with my hand shaking more and more as the epoxy started to set up in the syringe. Many aching evenings . . .

    A light bulb went on one day and i just placed the syringe (i usually use a 60cc or 2oz syringe) in a caulk gun and my all my troubles ceased immediately!

    here is an example of a tiny 10cc syringe fitting in a caulk gun with no mods! (- some will need a block inside the front with a smaller hole so the syringe wont slip thru) The best caulk guns are the cheap non ratchet type (not like the one shown) as continuous even pressure can be brought to bear as well as quickly backing off.




    [​IMG]


    this is a hot technique.




    .
     
  20. jurgenk

    jurgenk Paddler

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    Great idea Mick... I will try it the next time I am giving an injection as my thumb gets tired occasionally. Should make flushing those pesky catheter blockages easier as well. Of course I will give credit to you for the idea...

    Brad