Small part-time job offer. Looking for someone, who could draw plans for ~5m sit on top kayak type

Discussion in 'Boat Design' started by xellz, Nov 22, 2017.

  1. kerosene
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    kerosene Senior Member

    PAR, he wants to load it up (including himself) on dry land and winch down to water on a ramp. That means realtively high point loads for the wheel mounts. I would think it is quite easy to over engineer those sufficiently but for someone without engineer's eye it is good that someone else gives 2 cents so that there is good margin and solution is robust enough.
     
  2. TANSL
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    TANSL Senior Member

    He does not need TANSL. He only wants to make a series of changes that, could imply the need to reinforce certain areas of the boat, could suppose (in fact, they suppose) an increase of weight and a variation in the trim to full load and could suppose, even, that his project is not viable or is feasible if certain considerations are taken into account. I think it is very prudent to carry out some simple calculations. If he knows how to do it, he should do it, if he does not know how to do it, it is better for someone to help him. It's as simple as that. TANSL has the ability to provide that help and no one should feel uncomfortable about it.
    Cheers.
     
  3. PAR
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    PAR Yacht Designer/Builder

    I understand the premise of the problems, but I have to assume climbing in and cranking (or whatever) down the ramp will be a one time test, before he's back at the drawing board for another approuch. It's a kayak, for God's sake and burdening it down with little more than a few aluminum tubes and a couple of wheels seem absurd, at least on the face of it. The worst thing he could do is try this get in and launch idea. If he's not physically able to hand launch, another boat would be appropriate, not a butchering of an existing design. Simply put, a light kayak is 35 - 40 pounds and if this is too much, maybe it's time for something else, like a nursing home. Hell, he's going to have to lift a 35 - 40 pound battery for his nearly equally as heavy trolling motor and place these in the boat too. Really?, Let's see, a 30 - 35 pound motor, 35+ pound battery, the 40 - 50 pound kayak itself, plus gear and himself. No one sees any issues with this 100+ pound kayak, before the gear and crew gets in, all powered by electric, concept? Sometimes the best a professional can do, is talk folks out of their ideas, before they spend a lot on things that doesn't work.
     
  4. TANSL
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    TANSL Senior Member

    A few aluminum tubes that will have to support more than 200 kg, for land full of holes and stones.
    Of course and before advising, a good professional, should find out the problems raised by the question that another, not so professional, formulates.
     
  5. rwatson
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    rwatson Senior Member

    For a project of this types, some considerate and experienced design help would be not only advisable, but end up costing less than a trial and error approach. Just to be able to do the drawings, pre-calculating balance points, loading points, sorting out dimensions is going to make the project 3 times as likely to succeed.
    The requirements of being able to transport ( possibly with the passenger) of such a heavy craft ( battery, motor, wheels and hull) and/or launch is not only possible, but highly desirable. Even bare bones light kayaks are a pain to get to the water with all the associated gear, and putting wheels on them can make life much more pleasant.
     
  6. xellz
    Joined: Jul 2017
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    xellz Junior Member

    I'm trying to make this idea real not because me or my friend can't launch usual kayak. We actually do it all the time and current kayaks are 32kg before any added rigging and batteries. My work is not that tiring usually, but for friend every day at farm is already enough physical exercise for the day, he's not young too. Some kind of propulsion would be really welcome. Time it takes to get everything ready for launching and clean-up after return is rather big on usual kayak. In winter going in water to remove wheels or search for those scupper holes to insert wheels is not fun either. Electric motor on kayak is not new and it has been done in many variations, it works well enough. Few ready solutions are also made for existing high end kayaks to fit in their rigging with little to no effort, pop it in dedicated slot and go. Although price is quite ridiculous and battery is small and can't be extended because it's single light unit.

    Polyethylene kayaks can't be stored in direct sun for long, especially if some weight is added. Can't leave them on wheels. Need to remove all gear and store it on rack away from sun. That's why want a stiff wooden kayak, that won't loose shape from being exposed to sun and when left on wheels. So we won't have to add and remove wheels, battery, gps/fishfinder, pedal drive and few other things every time. Just drag kayak out of water and leave it there with all rigging, on wheels, until next use, there is no worry about something being stolen. If can sit down in kayak before entering water, that would be really big addition to comfort and fun factor of going out to sea.

    I certainly severely underestimated how much time it takes to design even small kayak hull. But i got link for suitable plans here and after going over weight requirements, no change to size of hull is needed, even fully loaded below recommended max weight with safety margin added. Start with 1.2kw lifepo4 and leave open window to increase up to 4kw. This should allow for comfortable time on water, be it fishing or simply enjoying the ocean, even when going against tide and wind. With this i won't have to trouble TANSL too much.

    Price for the whole thing might end up even less than a hobie kayak costs in japan, it was over 4000$ per one after delivery and all we added are wheels and a fishfinder mounts.
     
  7. portacruise
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    portacruise Senior Member

    With a heavy (when fully loaded) and long kayak like what you want, it is better to position the wheels to take as much weight as possible, so that you don't have to lift the heavy weight from the back end, as well as push. The battery can be moved around to shift weight but the motor probably not.


    If the entire weight of the contents is balanced around the middle, the wheel axle will introduce extreme stress to the midsection, so it must be reinforced. This reinforcement is separate from the load rating of the kayak.

    PC
     
  8. rwatson
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    rwatson Senior Member

    The other bonus of using plywood and epoxy, is that it is much easier to add/chop/change features, than you can with Poly kayaks. I know you can get repair "goo" for poly kayaks, but with plywood and glass, you can easily add or fill say an extra hatch, extend a deck etc while adding extra strength with layers of f/glass.
    The bonus of "ready to roll" design is that you are more inclined to use it, if you don't have all the mucking around of locating and storing gear.
    Even if its just a case of being able to wheel the whole thing from the car, across a road, down a path to a boat slip, it makes the whole expedition 200% more enjoyable.
     
  9. Irie
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    Irie Junior Member

    Not a kayak, but sealegs has a 6.1m amphibious rib that might give you some ideas.

     
  10. xellz
    Joined: Jul 2017
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    xellz Junior Member

    Took a photo of launch and storage point at low tide, should be a lot easier to imagine. If sun won't make an issue and leaving on wheels won't deform kayak, can leave just beside ships with all gear, even fishing rods and lures. Battery charging can also be done in same place. Water color is due to volcanic activity, there are few other spots around the island with different color leaks. And maybe was confusing, but this kayak is for single person only. Extra weight is battery (initially 13kg 1.2kw lifepo4 up to ~40kg if necessary), brushless motor,shaft, prop etc 5-6kg?, cooler box with ice and catch can go up to 20-30kg. I'm little over 60kg, friend more, but he's not going to try to catch as much. I do sell part of my catch sometimes, best result so far is after work 2h on kayak got me a little bit over 300$ and 2-3 days worth of fish for family.

    Looks like plans will take a while to arrive, no downloadable plans and didn't even get shipping confirmation yet. Total expected load is below recommended by designer max load, the wheels system i thought of has to wait until i get plans. Hope it can be done.
     

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  11. IronPrice
    Joined: Jul 2017
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    IronPrice Junior Member

    No offense but if you want to stay dry then a sit on top kayak is not the best craft for you. That said have a look at the sea island sport from CLC boats.

    I do have some concerns about the effects of those wheels on stability and they could easily catch on stuff.

    Have you thought about a kayak trolley. The c-tug trolley by rail blaza easily disassembles for storage inside the kayak's storage hatch.

    I'm kayak fisherman and I'd like to observe there can be a difference between breathable dry-pants and breathable waders.

    Dry pants are made from soft and flexible fabric. If you fall in the water the external pressure will force the air out causing them to cling to your legs, preventing water ingress. I used to wear Palm sidewinder dry-pants to when surfing my sit on top kayak. I came off plenty of time with minimal water ingress.

    Breathable waders can be a bit stiffer and prone to filling with water.
     
  12. xellz
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    xellz Junior Member

    When there is no really strong wind i stay relatively dry even in large waves on hobie revolution 13 as long as i keep my orientation to waves, but that's not the point. Special cloth for kayaking will take even more time for preparation. Thin good rainwear over work cloth gives enough protection from water even during strong winds and breaking waves. But it's really bother to launch and retrieve kayak in such cloth without scratching hull on concrete. Never mind all preparations necessary for launching. I never fell out of my kayak by accident, but even during winter water is not that cold to be life threatening even without wet suit. Worst case would be just return early. Majority of time getting wet only feels nice, since it's hot.

    I think wheels that fit in scupper holes work better than suggested trolley. I've tried similar concept at the beginning, it's a pain to use, especially when getting out of water.

    I bought plans for sit on top kayak already, plans are on the way here. Only printable version was available. Wheels won't cause any issue for stability, not that heavy, i already keep wheels behind me in scupper holes. It's just the way wheels will be attached to kayak is different. I don't think second pair of wheels in front will make any difference to stability either, especially considering motor and ~13-25kg of battery weight will be attached to bottom of kayak. Large cooler box full of ice and fish however might be something to be concerned. Can fit only something in ~30-36L cooler box on hobie kayak. I've filled it to the brim numerous times and didn't notice much of a change to stability.

    What i'm aiming for is, electric propulsion as main, not pedal or paddle power. And always ready to launch kayak with minimal preparation time. As i've said, as long as i don't have to worry about deformation when leaving on wheels and sun exposure, i'll just leave everything near water all the time. Only will have to add some kind of housing for fishfinder and battery status display to protect from water.
     
  13. portacruise
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    portacruise Senior Member

    What I dislike most is marinating my feet for hours in salt water, fish blood and parts- how can I keep just my feet dry without waders or dry suit?

    How do you keep your kayak aligned properly with the waves, so you don't get hit broadside- especially when fighting a fish with a rod and reel? Seems like a fully hands free electric drive would be helpful if you can find a way to do it.

    PC
     
  14. xellz
    Joined: Jul 2017
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    xellz Junior Member

    That's where pedal drive and rudder matters, longer kayak also helps to keep direction and dry seat. But when water does get inside, it should drain quickly or something is wrong with design.
     

  15. IronPrice
    Joined: Jul 2017
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    IronPrice Junior Member

    How do you plan to fit your scupper wheels without beaching the kayak or getting wet? make sure you reinforce the scupper 'tubes' if you go with scupper wheels

    My stability concerns were specifically regarding your bow wheels not because of their weight but because they look buoyant and could be caught by a head seas and impart unusual forces to your kayak. But if you only go out in a calm sea that may never be an issue. I also think those wheel may catch your fishing line under some circumstances.
     
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