16ft surf launchable plywood boat

Discussion in 'Boat Design' started by Paul D, Jun 28, 2018.

  1. fredrosse
    Joined: Jan 2005
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    fredrosse USACE Steam

    "You can also graphite the bottom of any type of hull for a scratch resistant bottom."

    The use of epoxy & fiberglass coatings on plywood hulls is extensive, with many fillers available to mix with the epoxy for various purposes. The graphite option is to act as a solid "lubricant", suitable to reduce sliding friction. But that is not what is needed for a beaching condition, what is needed is a tough material that presents abrasion resistance, and for that duty white powder called "cabosil", mixed into an epoxy paste is far better than the graphite mix for enduring abrasion.

    I went through the process of putting on a heavy coating of graphite powder/epoxy on the keel of my steamer, assuming it was best for grounding, and it has been grounded and beached many times, but I replaced the graphite with cabosil/epoxy mix, very hard stuff. HARD AGROUND BRISTOL.JPG , and this holds up much better.
     
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  2. Richard Woods
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    Richard Woods Woods Designs

    Thank you Fallguy for suggesting my Skoota 20. However I would think the Skoota 18 was a better choice as the Skoota 20 folds for trailering. So, although I have launched it on a muddy/shingle beach with no slipway I don't think it is practical to do so in waves. The Skoota 18 needs no assembly and can be driven straight into the water and away

    I never like using the road trailer to launch boats - corrosion etc. I much prefer a launching trolley, just like a sailing dinghy or beach cat. On a Skoota18 you can then use a flat bed trailer as the road trailer, simpler and cheaper and has other uses.

    But a small powercat seems a very sensible idea. You cannot easily broach in waves and if you had two outboards instead of one central you can more easily correct your course when hit by big waves. Running ashore is easy with flat bottoms and using a double layer of sheathing glass will make it durable (most cruising catamarans dry out regularly). Plus all the other advantages, see article link below

    Check the Zapcats/Thundercats and Texel beach cat race to see how safely small cats can get out through surf (although obviously you are looking for something more sedate)

    A general "why a powercat" article is here
    Sailing Catamarans - The Ideal Pacific NW Cruiser (a Skoota powercat!) http://sailingcatamarans.com/index.php/articles/43-power-catamarans/478-the-ideal-pnw-cruiser20
    aimed at bigger boats but still all relevant whatever the size

    and details on the Skoota 18 here
    Sailing Catamarans - Skoota 18 trailable 8ft wide daycruising or fishing http://sailingcatamarans.com/index.php/designs-2/6-powercats/489-skoota-18

    It is similar build to the sailing version, the Chat 18, see here
    Project Catamaran Chat18 http://projectcatamaranchat18.blogspot.com/

    Hope that helps

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Your typical planing power cat is really not favoured for beach launches in this part of the world, mainly because of the height of the boat on the trailer, and the depth of water needed to float them. Unlike a vee hull, where the middle roller at the back of the trailer is pretty low down, on a cat they are way higher, the hulls sit high over the top of the wheel arches, not between them. The trailer and tow vehicle have to go rather further into the water, with the attendant risks involved.
     
  4. Paul D
    Joined: Jun 2018
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    Paul D Junior Member

    Thanks
    Thanks for your advice and time guys...im learning taking it in ...much appreciated...impressive machine you got there fredrosse....cherz for the advice mate
     
  5. Richard Woods
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    Richard Woods Woods Designs

    That's why I suggested using a launching trolley not the main trailer. But a major advantage of the trolley is that it can be turned round so the boat is launched bow first. Most "speed boats" launching stern first into surf are going to be swamped by the first wave. Same on retrieval of course

    Anther reason for going bow first is the prop is then at the back, not the front, and the leg will kick up if it hits bottom, not break off. The best would be a jet drive of course, but they are not very efficient at low speeds and sand in the intake shortens life

    (My Skoota designs aren't planing cats BTW)

    Richard Woods
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    No doubt the South Africans would disagree about the suitability of planing cats for beach launch, they seem to love the things, but the trailer is the problem, it has to be more deeply immersed.
     
  7. fallguy
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    fallguy Senior Member

    The Skoota isn't a planing hull folks.

    I think a small displacement cat designed for beaching, is a great way to go.

    If the sea got rough; what would you do in the monohull? In the Skoota, you head toward the beach and time the tide and beach the boat on outgoing tide. Try beaching the monohull...not easy and the trailer would need to accomodate a shore drag.

    Anyhow, entertain the idea a bit. The build would be fun as well.
     
  8. fallguy
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    fallguy Senior Member

    Another thing is the cabin on the Skoota 18 is probably not a structural element, so this is for Richard, but the boat can be easily tweaked for a better fishing/dive boat rather easily.

    It certainly isn't in the super affordable plan pricing, but it seems mods would be relatively straightforward and RW can also speak to this point.

    As to the graphite vs cabosil argument, the only question is UV. If you were going for some UV protection, the late PAR had advised adding ?aluminum oxide powder. A boat on a trailer with no UV protection is also a bit risky. But thanks to the fellow for mentioning it because I have been debating a strip of graphite on the vee and now I'll skip it.

    Good luck.
     
  9. Paul D
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    Paul D Junior Member

    Thanks fallguy...it would be a fun boat build bit more expensive id say but manageable over a year or two...monohull would be cheaper and a quicker built simply....but the skoota 18s an interesting boat i quite like it not something id ever thought of....they have aluminium cat power boats over here in NZ called blackdog cats i think...they are really popular boats up north....good stable platform for fishing...shallow draft etc...

    Anyway thanks mate....
     
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  10. Mr Efficiency
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    Mr Efficiency Senior Member

    I realise Richard's Skootas are not planing cats, I was merely pointing out that the geometry of boat and trailer goes against cats, as beach launch proposition, I assume Richard meant by a "trolley", a contrivance where the hull sat low upon it, and did not require to be backed in too far, to retrieve the boat. But I can't see how the trolley solves the problem, unless you virtually live right at the beach, you can't easily have a road trailer and trolley to interchange, at hand.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Another more or less mandatory requirement for a boat coming in through surf, is to be able to hold the back of the wave, you don't want to risk being caught from behind, that might become a bit marginal with a displacement cat with low power, but I do agree that cats have many advantages, and one of those, they sit level when grounded, when you are trying to wrestle something on to the trailer in beach shallows, you are relieved of the chore of having to keep it more or less upright.
     
  12. bajansailor
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    bajansailor Marine Surveyor

    Paul, I just had to google your Black Dog cats - they look interesting . A bit like a cross between a 'conventional' planing power cat and a typical pontoon boat.
    Blackdog Cat NZ Boats - The ultimate aluminium pontoon boat http://www.blackdogcat.co.nz/

    I think though that all else being equal, Richard's Skootas would be far more economical on fuel than the Black Dogs, if this is a concern.

    Re beaching or launching through surf, this reminded me of a video showing one of the RNLI Mersey class lifeboats being launched off a beach with an on shore gale creating some pretty rough conditions.
     
  13. fallguy
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    fallguy Senior Member

    Video is super cool. Can't say I expected to see them back in!

    All I will say is any open boat will have a much harder go in surf than the skoota well designed.

    There are two concerns. First if you come in fast with an open bow; you can hog into the trough. Second, if a wave breaks over the stern of a monohull; you need the water to exit fast. If you are travelling below the hump speed in a planing hull; many monohulls bow raises when you slow down and exacerbates the issue of a wabe breaking ober the stern. This is why I recommend a full height transom if you go monohull.

    If you designed the skoota 18 accomodation correctly; any stern wave can quickly exit the craft. The skiff can be made with scuppers; not the same.

    The bridgedeck of the skoota can be designed so water is not able to reside on the boat for very long.

    On my skoota build, we are putting boarding doors that double as rogue stern wave reliefs.

    I don't mean to beat a dead horse, but speed is not as important for the Skoota in the surf as it is for the open monohull.

    As for landing. A cantilever type pontoon trailer would work well I'd say.
     
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  14. Paul D
    Joined: Jun 2018
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    Paul D Junior Member

    Cool video mate thats crazy ...id be still at home on day's like that☺
    Yea i was interested in the blackdog cats a couple years ago but they were bit pricey for my income ....nice boats tho..
    I like how the skootas powered by a small outboard it will save on costs of the total build if i decide on it...i can also stretch payments out building a plywood boat instead of a the big lump sum for a new boat....
    Cherz
     
    Last edited: Jul 7, 2018

  15. Paul D
    Joined: Jun 2018
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    Paul D Junior Member

    Mate the skootas got me dreaming a bit allright.. got its good points definitely..
    What size one r you building fallguy?....
    One problem i have is my garage door is 2.3m wide and the skootas 2.5m..i know if it could be lifted somehow on an angle id get it out maybe otherwise id have to cut a 200mm hole in the wall ...
    Richard said the design of the cabin the way it is would help with a wave breaking over top...i actually like the layout of the cabin and cockpit i think it would be fine the way it is maybe bit of a squeeze for 3 fishing though but doable...

    Its got its good points and ive been entertaining the thought..but i know its guna cost a bit more than a simple monohull...lots to think about..cheers
     
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