Newb with some preferences, few clues...

Discussion in 'Boat Design' started by Snorbitz, Jul 20, 2007.

  1. Snorbitz
    Joined: Jul 2007
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    Location: Borneo

    Snorbitz Junior Member

    Hello.

    I'm figuring if you guys know design you're probably the best peeps to ask some newb questions :)

    I'd like to build but probably buy an 18 to 19ft boat, with cuddy cabin. I suspect I need a semi-displacement hull, outboard gas motor, probably 2 stroke.

    Could such a thing be pulled on a trailer by a low-powered 4x4 and would it, within reason, be capable of scooting around the coast to get to different rivers (would spend 70% or more of its time on freshwater)?

    Also, any idea of minimum or maximum beam/width?

    What kind of horsepower would it need? Could I get away with below 50hp?

    Any idea what sort of speed at what sort of horsepower?

    Also, what kind of draft (depth below water) would such a thing have/need?

    Whilst it's easy enough to find articles telling me that no one boat can do everything and that both sail and engine, 2, 4 stroke or diesel exist, blah blah blah, it's not so easy to find such basic data.

    Ideally what I want is something easy to stick in the water, capable of sleeping 2 overnight, can handle a bit of choppy sea if caught in it but avoided whenever possible, mostly for river cruising/fishing locally but the occasional weekend trip to further rivers.

    It's hard to find such boats where I live, as they all seem to be either canoes or luxury yachts, few of the sort of little runabouts I saw in the UK. By the way, any idea of costs of having such a boat, 2nd hand, shipped to Borneo? :)


    Also, any good resources for freebies on dead reckoning and general small boating online? I already have 2 lifejackets, no boat but I have me lifejackets...

    I know enough to know I don't know much at all, so advice would be appreciated.



    S.
     
  2. Guest625101138

    Guest625101138 Previous Member

    You could have a look through this site:
    http://www.boatsonline.com.au/boatsearch.asp
    Do a search for power boats in the range 15 to 20ft. Aluminium is likely to be a bit lighter and more economical.

    Most boats like this in Australia are powered to plane. So power level usually around the 90HP mark. Semi-displacement often cost more and could be heavier. The size range you are thinking about should be easily pulled by a 4X4. I expect beam will be arounf 7ft. There would be no restriction on transporting a boat like this in Australia.

    This one is a bit smaller than you specified but it has a couple of bunks.
    http://www.boatsonline.com.au/display_gallery.asp?mid=BOL&did=PRIV&ref=wa4682
    Would be capable of coastal work if you do not venture too far from shelter and keep an eye on the weather.

    The speed is sometimes quoted. A 90HP would give maybe 30kts depending on the size of boat of course.

    You need about 2ft of water to operate safely even on the plane. More if it is a hard bottom. If draft is an issue then there is the option of a jet drive but these are more difficult to find.

    I am not sure about your reference to dead reckoning. A GPS and charts for your area of operation should be about all you need. If you get a more expensive GPS it will have charts loaded. (Although I have no idea how well charted your area of operation is.)

    Launching and retrieving a boat around 17ft is not difficult with modern trailers. Can be a one person job.

    You might find a supplier in Perth, Australia who can help with transport but our currency is high right now. Perth's economy is hot but it could mean there are a lot of people trading up. It is very popular for boating.

    Rick W.
     
  3. timgoz
    Joined: Jul 2006
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    timgoz Senior Member

    Hello S,

    Welcome to the forum.

    A good basic boating book is "Chapmans Piloting and Small Boat Handling".

    Amazon would have it I would think. Some more advanced texts would be Dutton's or The American Practical Navigator ("Bowditch").

    Even with GPS and charts it is both critical & responsible to know the basics of coastal navigation. GPS will prove a useful tool that will compliment, but never replace, a working understanding of the fundamentals of navigation.

    Take care.

    Tim
     
  4. Snorbitz
    Joined: Jul 2007
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    Location: Borneo

    Snorbitz Junior Member

    Thanks for the replies. :)

    I love GPS and was using Garmin units while most people would look blank at the initials, but was using them for driving and trekking. Currently I only have a little Garmin Gecko handheld, waterproof but no charts of any sort nor the means to load them.

    GPS is a real God-send and makes life extremely easy - but I've always tried to find additional means of navigating, if only as even in the car I've used handheld units that could be lost, relied on AA batteries etc. By the way, they don't like thick jungle cover :) Different story on the river though, with a clear line of sight.

    I believe charts are available for the coast, not so sure about the rivers, even though some are massive.

    Rick, thanks for the idea of Australia - though I'm still doubtful as to the cost of transporting to Sarawak.

    Are those prices Australian dollars?

    Actually there seems to be quite a few seagoing boats in the 12ft range. Interesting, as peeps have told me before that "20ft too small, best buy 30ft if going to the coast" - but then again they're talking about long thin open things.

    I don't see any mention of bilge pumps on any of the boats on that site that I've looked at. Do most such things, with for example a Johnson 40hp, which seems a popular choice on there, have the means to run such a pump? I'd presume, I don't know, that such an engine's electrics would have a 12v output somewhere or just connect direct to the battery?

    Tim you mention "Bowditch", I think I downloaded it the other week, but it was massive, hundred and hundreds and hundreds of pages? The Chapman thing looks very good though. Soon I shall have 2 lifejackets, a very basic GPS and a good book ;)


    OK, quick straw poll, is a 12ft boat safe in the South China Sea, off/along the coast of Sarawak, Borneo? Anyone familar with the area? I already know to avoid the rainy/storm season!


    S.
     
  5. messabout
    Joined: Jan 2006
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    messabout Senior Member

    If you are thinking in terms of a conventional power boat, a 12 foot boat is definitely too small. There are reasonably capable small keel sailboats that might survive the South China Sea. Something like a Bolger Micro is small, ugly, cheap, and proven seaworthy within limits.
     
  6. Guest625101138

    Guest625101138 Previous Member

    A small boat can be seaworthy but I would not regard a tinny as something to take offshore. It could be OK for beach launches. If you are considering something as small as 12ft then inflatable style is probably the most seaworthy. Would not be very comfortable though.

    A motor around 40HP would normally come with electric start so has alternator and needs a 12V battery. The power output will do a few auxiliaries like electric bilge pump, spot light etc if that is what you want.

    My experience is that most small planing boats don't bother with bilge pumps. If you do take in water you can get it to run out once on the plane. There are drain plugs in the back of the boat. Often a trap for new comers who forget to put the plugs in when the boat is launched off the trailer. By the time the car is parked the boat is half full of water.

    Larger boats around the 18ft mark and above often have sealed cockpit floors that are self-draining. The floor actually sits above the waterline.

    The site I referred to in the original post is Australian so prices are AUD.

    If you want to have a back-up to the GPS then a hand bearting compass is a good option:
    http://www.biasboating.com.au/compass.html
    You can play around with these on land providing you have a map with some good landmaks. You will need the magnetic correction for your area. Charts come with a compass rose that shows the magnetic correction.

    Basic coastal navigation can be done with a hand bearing compass, good chart and parallel ruler:
    http://www.videos.sailingcourse.com/parallel_ruler.htm
    It helps to have a watch as well. It is just simple geometry for the most part. Get a bit more complex when you have to allow for drift and you actually want to hold a course.

    I have a 25 year old hand bearing compass that strill works OK. I have looked after it though. In those days it was just about the most precious thing on the boat when you are in unknown waters. No batteries to worry about and it had good alignment optics.

    Rick W.
     
  7. timgoz
    Joined: Jul 2006
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    timgoz Senior Member

    I would add dividers to my minimum nav kit.

    Spent the summer of 2003 among the islands of SE Alaska. My boat was a
    14'3" all welded aluminum skiff with a 9.9 outboard. I could not go everywhere I wanted, as in rounding certain headlands or crossing wide straits. Do not know what kind of currents you will be dealing with.
    Where I was we had up to 24' of tide and the currents associated with it.

    My nav kit was a full set of paper charts, hand bearing compass, parrallel rules, dividers, and Garmin hand-held (non-cartographic) GPS . A good submersible hand-held VHF with weather capability was essential also. I kept the radio secured inside my float coat when in rough conditions.

    In smaller boats a bucket combined with adreneline makes an efficient water remover. Keep it secured with a small snap shackle or the wave that swamps you may take it overboard also.

    Tim
     
  8. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Snorbitz,
    From your original description of your needs it sounds like you've already put some thought into this.
    What you're after is not a common animal, not among mass-production boats anyway. Production powerboats in that size tend, on the whole, to be oriented for one of three things: blasting around the lake at forty knots while carrying sunbathers and skiers; blasting around the lake at forty knots to beat your buddies to the fishing grounds; or being dragged around on rocks and beaten up by kids and gear in the course of cottage/utility duty. Efficient, low-power overnighting is not something the big builders have clued in to yet.
    As long as the complete rig (including trailer) is less than about 2.5 m wide, you're probably OK for trailering in most places (check your local regs). The average small SUV can tow maybe 1.5 tonnes or so, check your owner's manual because it could be anywhere from 1 to 4 tonnes depending on your vehicle.
    Many people, when they find the new/used market just doesn't have what they want, start to think about building it themselves. If this strikes you as a possibility, get in touch with Tom Lathrop at http://bluejacketboats.com/ , his Bluejacket 20 might suit you (although it's a bit bigger than what you're looking at, it's also very light). Phil Bolger also has some excellent designs; check out http://www.instantboats.com/boats.html - the Diablo Grande can easily be modified to include a small cabin.
    I've yet to feel the need to fit a GPS in my boat. I cruise mainly familiar and/or well charted waters, and I find it easier to navigate visually using the chart and landmarks. Then again, my boat is small and I do not go far in it.
     
  9. alan white
    Joined: Mar 2007
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    alan white Senior Member

  10. timgoz
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    timgoz Senior Member

    I really like the Redwing 18 also. It would sip fuel & offer a good range for a small boat.

    Tim
     

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  11. Snorbitz
    Joined: Jul 2007
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    Location: Borneo

    Snorbitz Junior Member

    Mmm, just managed to lose my lengthy reply with some slip of the mouse. :mad:

    I explained various reasons why building my own isn't an attractive option, not least the heat/humidity, mosquitos and lack of space.

    Annoyingly, I also gave a detailed and hugely entertaining account of my first ever boat trip here in Borneo! Managed to find some gullible fool to rent me his boat for the day, so went exploring the Sarawak river. I would tell you all about it but am struggling to find the enthusiasm to type it all again!

    One disappointing thing was discovering there is a "barrage" barrier thingy on the river just past the town. Seagoing boats are on the river upstream of the thing so I presume there is some means for getting through it, indeed there is apparantly something called a "shiplock". I presume, dunno, that it's the same kind of thing as a canal lock? Sorta raises you up to the level beyond or something?

    With no radio or anything we just burbled up to the barrier, stared at it and decided to go around - then found the route blocked. Since then I've learnt it is to keep salt and silt out of the main river and to keep the river more stable, prevent floods etc. Hence blocking (at the time we figured it was some kind of toll thingy).

    Have a phone number so will phone em on Monday and find out what the procedure is for getting through it, if there is a fee involved, if it's only passable at certain times or whatever. Puts a big dent in the "freedom of the open water" image though, if one has to make an appointment and pay to go down the river. Will see.

    The boat we borrowed/rented was pretty long, I'd guess at least 20 feet, maybe 23 or so, but pretty narrow. Barely enough room for 2 people to sit beside each other. Also totally open, so one big breaking wave and nothing to hold it up.

    Spot of de jevu (sp?) as I described this incident on a similar forum last year, but my only sea boating experience was renting a little thing on holdiday in Greece many years ago. Very easy and pleasant going out, found a little cove after about an hour's gentle cruising in some little fiberglass tub. The owner of the boat rental agency came along much earlier than we were meant to return it, gestulating that we should return immediately. On the way back discovered why, as it was pretty choppy. Maybe not choppy for a larger covered boat but this little thing was really struggling, slamming into the trough behind the 3 or 4 foot waves with a mighty thud, filling with water and not in the slightest bit stable if attempting to go sideways.

    One hour at around 3/4 throttle out, 3 hours of mostly full throttle getting back, having ripped off the awning that caught the wind so hard it felt we were going to go over backwards at the peak of each wave. I had no choice bit to aim straight at the waves and ended up heading further and further from shore while trying to go up the coast. Only the zippy surging performance made it possible, upon reaching the bay, to go past it and then manage a heart-stopping mid-wave spin around to turn around and come in.

    Once in the bay the water was much calmer and it pottered to the jetty like nothing had happened, but we had no life vests, my GF at the time couldn't swim 5 yards let alone the 500 yards to shore and it put me off the sea for years.

    I should add that apart from a stiff breeze it was a lovely sunny day!

    In retrospect that boat should have never have left the lake it was designed for. Looking back it was really quite ridiculous - inadequate boat for ANY kind of waves, no life jackets or anything of that nature, "training" consisted of "turn this, go faster, push this, go backwards", no-one had any idea where we were going or what direction, just "Be back before 6pm".

    I have a great deal of respect (OK, raw fear) for the sea and know painfully well that even "little waves" on a sunny day can throw a tub around and fill it with water.

    By the way, what IS the procedure for going across rather than into waves? I just went straight up, tried zipping diagonally down and quickly turning into the next one, as the boat was tipping over alarmingly at anything else. I found the waves weren't the problem, it was the big hole in the sea BEHIND the waves that seemed to be trying to tip the boat over.

    Does a wider boat make much difference or is it necessary to have one of those pointy blade things that stick out the bottom, or what?

    I'll see if I can shrink and attack a pic of the thing we went out in this weekend, which also swayed around alarmingly at the bow-wave of another boat passing (most such incidents I again aimed straight at em, but once I tried just going straight to see what happened - can we say "rolled a lot more than I'd have liked, for such a little bump in the water"?)

    It's about the right kind of length but too narrow, no cabin or anything, though does have a canopy thing.

    By the way, the owner said it was 3 hp, I suspect he meant 30, as it was quite zippy and I doubt 3hp could shove that thing that quick? My satnav said our average speed, cruising, not flat out, was 8.6mph. It burnt up most of a large plastic fuel tank in just under 4 hours - can't say just how big that tank was pretty hefty. Surely not 3 but 30?


    S.
     

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  12. Snorbitz
    Joined: Jul 2007
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    Snorbitz Junior Member

    Kewl, reading the behavior of the Bluejacket the author describes virtually the same situation I encountered in Greece - he also explains why those "little" waves were such a hazard:

    "A 3-foot wave in the open ocean is usually not much of a bother but the same wave height in shallow inshore water can be a real bone cruncher. This is because the friction of the nearby bottom causes the waves to bunch up and shorten the wave period. The waves thus develop a steeper front that gives the boat a sharper blow at a greater frequency than in deep open water. The other factor is that these short waves move much more rapidly than open water waves of the same height or wavelength period. The shallow water will not allow really high waves to develop and as the wind increases further, the speed of the waves increases disproportionally to the height and period."

    :)


    S.
     
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  13. timgoz
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    timgoz Senior Member

    S,

    I call them square waves because of thier steep faces.

    If you had calm water going out and were going 8.6mph in a small (10-14ft. ?) boat, you did likely have a 3hp. Though 3hp sounds somewhat small to me (6hp sounds about right) a 30hp would of given alot more speed at that throttle. You do not give the boats length so the above is a guess.

    When I'm manuvering a skiff in steep short cycle waves I cut the crests at approx. a 15 - 25 degree angle, depending on conditions. It is almost like a waterborne ballet. You are constantly adjusting the boats speed, your bows heading, and many times your body's position in the boat. The later is for balance. All these skills come with time. Being along with an experienced man at the helm and watching as close as possible will accelerate this learning process.

    As you have already seen; operating small boats on big waters can be a dangerous undertaking. Small cautious steps will lead to greatly enhanced ability while keeping you healthy. The tone and content of your posts suggest to me you are on the right track.

    Take care.

    Tim
     
  14. Snorbitz
    Joined: Jul 2007
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    Snorbitz Junior Member

    I knew someone would confuse my description of Saturday's river trip with my harrowing experience in Greece :)

    My fault, should have been clearer.


    No, the boat I'm pondering the power of was around 20ft, maybe a little more. I attached a pic of it in my earlier post, the yellow thing. I admit I was surprised at how light it was when it came to moving it around docking, pulling at a sticky-up stick thing I could pull the boat around with one hand. However the sheer wake and general water disturbance at full throttle, where I'd guess the speed at around 20mph, didn't seem possible to me as being 3hp.

    Put it this way, as a youngster I had a lot of fun on 50cc bikes producing 5hp, also 125cc machines around 10 to 15hp, 250cc bikes kicking out up to 30hp - and that thing struck me as more like 30hp. I'm open to the idea I'm wrong, which is why I mention it in the first place - but I really can't believe something with less power than a moped could send me and wifey surging through the water like that.

    The entire trip was on the river, though in Borneo (see pic) "river" is a little subjective, as some bits can be over a mile across.

    The near-drowning experience in Greece, around 15 years ago now, was in a boat about the size of a large rowing boat, I'd guess, best as I recall, around 8ft long, 5ft wide, square front end (hence the wince-inducing BOOM at it fell off the previous wave into the front of the next one).

    That thing I could believe was less than 5hp.

    I'm really taken by the Bluejacket 20, that seems pretty much perfect for me.

    It strikes me as an inoffensive but sturdy, even stubborn little thing. Lovely lines and well-behaved by the sounds of it.

    Now I'm wondering on the advisability of getting the plans and trying to find a local boatbuilder who could follow them...

    I'm surprised though to see in the pics that much of the construction seems to be a matter of large sheets of plywood? I don't quite know why but I kinnda presumed one needs planks?

    Just how strong is plywood, compared to conventional planking or fiberglass?



    S.
     

  15. alan white
    Joined: Mar 2007
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    alan white Senior Member

    Using the same design, plywood ought to be equal in strength to other methods (excepting welded aluminum and steel). A good designer will attempt to come reasonably close to what another method of build would stand up to by adjusting the thickness of the ply and the size/spacing of the frames.
    This is why it is difficult to answer that last question.
    If, in adjusting scantlings, the boat becomes lighter or heavier, then cost in material and labor factor in. Is an increase in weight to achieve the same strength desirable if it lowers the cost to the builder/owner?
    Some boats are better candidates for plywood construction. Obviously, the list begins with conically developed shapes. Yet ply can be very cost effective in cold molding as well.
    In general, for a low tech (easily and quickly built) boat, plywood makes for a very strong and light hull for the money. This holds true up to a certain size range, where planks of solid wood are purchased at lower per-foot price, while ply remains closer to the low-volume price per sheet.
    Almost nothing can touch plywood as a material for building small and simple boats.
    If light weight is a big concern, there are certainly lighter methods, but cost of labor and materials will go up drastically. Racing boats pay a lot for that last 5% in performance, something real-worlders usually can do without.
    Fiberglass, uncored, is heavier than either ply or strip or planked if real life strength is considered. Solid glass might be made light by extensive framing, but at that point, it makes more sense to core between two layers and save time and complication.
    To simplify, plywood is the strongest, lightest SIMPLE way to build a certain type of boat hull.

    Alan
     
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