Clueless Student's Superboat Extravaganza

Discussion in 'Boat Design' started by Angfonz, Sep 28, 2008.

  1. Angfonz
    Joined: Sep 2008
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    Location: Australia

    Angfonz New Member

    So, my friends and I want to build a boat with which to conquer the high seas (read: THESE CANALS) But, we have encountered several highly problematic obstructions. They are as follows:
    1. We have no boating knowledge, whatsoever.
    2. We have an extremely limited budget.
    3. The two meter bull sharks in these canals have, on occasion, been known to eat foolhardy mariners, such as ourselves.

    Now, these issues might normally deter the less courageous sea dogs, but our resolve is strong, and our temerity is stronger! And, while I am new to boats, I am vastly familiar with elitist internet forums. I sincerely hope that my lack of experience and lighthearted outlook on this project do not inspire you to harness you inner forum-nazi, and berate me for my incompetence. I am here to learn from people who know what they are doing.

    With that said, let us get down to the proverbial 'bidnis.'

    Our budget must not exceed AU$1000 and must include:
    1. Construction Materials
    2. Engine
    3. Other Necessary Accessories (anchors/pirate wenches)

    With that said, our plan of action (so far) is this: We are going to build a sort of ghetto-fabulous trimaran out of three used canoes, such as THESE - preferably with the center canoe being slightly longer than the two on the outside. Id like very much for the 2 outer canoes to be the same model due to buoyancy issues. We then plan to attach a solid 'deck' of cured wood to the top of these three canoes. This will be covered in astro turf to add to the awesome factor, and surrounded by a railing to deter from drunken shark-swiming. With that said, the deck would be about 4 meters long, and 5-6 meters wide. As far as an engine goes, I figure a 2-10 horsepower lawnmower engine, slapped with a drive shaft and a prop could come out looking something like THIS, which would be perfect for our setup.

    But there are some things to consider. We'd like this boat to be able to comfortably fit 6 people. We will bring lawn chairs and other such seating contraptions, or perhaps build some benches along the railings. Do you think that this motor will be enough to power a boat of this size? There is a very good chance we will be carrying a lot of very stupid things with us, such as a generator, a case full of 500 beers, fishing equipment, random contraptions and gizmos, and maybe a goat. What do you suggest as an equally priced alternative?

    Are there other options besides canoes, that will perhaps reduce drag, to use as our pontoons? I see there being issues with having open canoes acting as our flotation devices. Since they will be mostly covered, if they fill with water while we are out, there will be no real way to get that water out of them without beaching the boat and tipping it over. Do you have any suggestions for something we could acquire second hand that would neither break our budget or slow us down too much? We would also like to keep the clearance relatively low, and able to be beached without too much difficulty.

    If I have missed a post similar to this in my search of the forums, pre-post, please let me know.

    Thanks in advance.
  2. BHOFM
    Joined: Jun 2008
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    Location: usa

    BHOFM Senior Member

    Sounds like you need to look for a beatup old pontoon
    boat to start with and do some reworking..

    Save a lot of time and money.

    The open canoes could be a big problem, you would
    need to fill them with foam for sure. Costly.

    Is this to be left in the water? The size seems unmanageable?
  3. Angfonz
    Joined: Sep 2008
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    Location: Australia

    Angfonz New Member

    Things deemed 'luxury' are a hell of a lot more expensive in Australia for some reason - and boats fall into this category. That pretty much rules out buying any sort of real boat. The cheapest we could find is upwards of 5000 dollars for anything that even sort of runs.

    The boat is meant to be left in the water - we have access to the school's rowing club docks, and will leave it there. That, or it carried by 6 strapping young men a short distance away to outside our on campus residence. Maybe we should reduce the size. We could probably make due by dropping the central pontoon and making a catamaran. That would bring the dimensions to somewhere along the lines of 3.5 meters across, and 4 meters long. Thats pretty cramped for 6 people, but maybe we can put the womens and a rubber dingy we pull behind - ya dig?

    Any suggestions on where we could find used / old pontoons, sans boat? Are there any pontoon replacements? Could I use old oil drums, or make heavy duty Styrofoam floats? Could I cover the canoes instead of filling them? This is where I intended to spend most of the money - the lawnmower motor will come from a junkyard, for (hopefully) under 200 bucks, and the deck / railing lumber wont cost much more than 300. That leaves 500 bucks to spend on something to keep this thing from sinking.

    Thanks again!
  4. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Well. Sounds like you have your work cut out for you :)

    Styrofoam billets are the material of choice for floating docks around here. They're not exactly cheap, though. 55-gallon drums work, IF they are watertight and clean (you can't use the kind that still have a bit of oil residue in them, this tends to damage the lake).

    An old pontoon boat would be an ideal starting point. Strapping canoes together would float, yes, but would prone to sinking when waves break over the gunwales. Look for larger, deeper hulls, or else look for sealed pontoons.

    No doubt one of the Aussies here will chip in on what licences and safety certifications your pirate ship will need to be legal in Australian waters.
  5. kengrome
    Joined: Jul 2006
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    Location: Gulf Coast USA

    kengrome Senior Member

    Other than possibly foaming the ends of the canoes for emergency flotation, I see no reason whatsoever for wasting all that valuable space in the middle of the canoe hulls by filling it with foam.

    Why don't you just make sure you get two identical canoes for the outside hulls, then build the deck so that it conforms to the profile of the gunwales of the two outside canoes -- and seal the canoe gunwales to the underside of the deck completely so water cannot get in there?

    Then you can make a couple of raised hatches in the deck over each of the outside canoes so you can get inside and bail them out if any water gets into them. And since it would be unlikely for any water to get into them anyways (except through these hatches) you can use the space inside the canoes for supplies and maybe even to sleep in.

    Ideally you should get three identical canoes so you can do the same with the middle canoe as well. As far as storage when not in use is concerned, it might be better to drag it out of the water and flip it over. Just leave the hatches open when it's upside down in storage like this so air can get inside the hulls and dry things out to prevent rot.
  6. Angfonz
    Joined: Sep 2008
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    Location: Australia

    Angfonz New Member

    At this point we have found a guy giving away old oil barrels. This seems to be the best option for us as, well, they're free.

    We are using a very simple design for the barrel raft, that I'm sure you've seen 1000 times. But, I think I'm running into issues with the buoyancy of the thing.

    From what I've read on the forums, the efficient level of flotation for something like this is 1/3 of the barrel under the water. Forgive the fact that my numbers are in a combination of systems, but here's what i have so far:

    200 liter barrel @ 2.2lbs/L = 440 pounds per barrel
    each barrel is 25lbs so a net 'floatation' (whats this called?) of 415lbs before it SINKS.
    8 barrels (4 on each side) = a sink weight of 3320lbs
    efficient level of 1/3 of that = 1106lbs
    max 'ok' weight of half the sink weight = 1660
    6 people @ an avg. weight of 180lbs = 1080lbs

    So, 1080 lbs before the frame / any gear - and we're only 100lbs off the ideal weight. I think that we will be alright if 1660lbs is an acceptable load for this thing - is it?

    If not, we can add 2-4 more barrels in the center, creating a sort of trimaran raft thing. But, I feel like this would really destabilize the entire thing. Having the tipping pivot point become the center of the boat, whereas it is the side with no central barrels, seems pretty sadface.

    Any thoughts?

    Edit: Here's a rough MSpaint picture. The additional barrels would go in the center, obviously.
  7. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    I've seen some creations from Cuba which have challenged the high seas on (I guess) much smaller budget than yours. So you guys should be able to make it.
    This was my little moral support. :D
  8. Dane Allen
    Joined: Jul 2008
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    Location: So Cal

    Dane Allen Junior Member

    I love it when words like clueless and extravaganza are used in the same sentence, what could possibly go wrong? I was with you until the subject of Bull Sharks came up and now I'm concerned that any ideas I give now I will have to reiterate under cross-examination at a later. I know the U.S. has extradition treaties with Australia.

    Anyway, What college taught me was that beer cans have a slight positive bouyancy, we would tie 6 packs to the craft and leave them to float to keep cool. Maybe you could tow a mini-boat/cooler for food & Booze.

    Might even use two canoes for the people platform and the 3rd canoe at a separate, towable storage unit. Keep the main craft as light as possible. Another crazy idea would to also store fuel in the 3rd canoe and run a fuel line to the main craft.

    You could even do the Trimaran thing and use a fourth canoe type craft as towable storage.
  9. Angfonz
    Joined: Sep 2008
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    Location: Australia

    Angfonz New Member

    I think we're set on the basic design, at this point.

    Can anyone comment on my math (above)? Do I need another row of barrels or can I run this thing at half its sink weight?

    If I add two more barrels (between barrel 1 and 5 / 4 and 8) I could get 1/3 of its sink weight up to 1383, leaving 300lbs for frame / gear after 1000lbs of people.

    If I add 4 more barrels, the 1/3 sink level is 1660lbs, which is much more workable - but we probably wont even get to that point. If the boat doesn't sit deep enough into the water wont that really make it unstable, especially with a central row of barrels?

    Adding 2 more barrels (between the 1 and 5 / 4 and 8 barrels in the above picture) brings out 1/3 sink weight to 1383 and 1/2 sink weight to 2075. We will obviously be somewhere in the middle of that. Does that sound 'okay' ?
  10. eponodyne
    Joined: Aug 2007
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    Location: Upper Midwest

    eponodyne Senior Member

    Go ahead and add another row of barrels. It won't hurt and it might help.

    When you build it, make sure that you don't have your decking resting right on top of the barrels. Run your joists and stringers so they kind of rest on the "shoulders" of the barrels, with the deck being a uniform inch or two above the barrel. Ya folla?

    Floating the barrels shallower won't make it more unstable. Maybe if you were balancing on one row of barrels, but not on 3.

    You do realize at this point you're building a raft, not a boat, right?
  11. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    For a fellow ozzie you are making things difficult with your maths,

    1 Barrel = 200 litres
    1 litre = 1 kilogram
    each barrel displaces 200 kilos.
    averager say 100 kilos per person

    this is the age of metric mate - make life easier :)
  12. diwebb
    Joined: Jun 2008
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    Location: New Zealand

    diwebb Senior Member

    if you need the additional bouyancy why not make the raft a bit narrower and longer and add extra barrels in the length. This will give the motor less work to do than adding an extra row in the middle. Also if you then trim the raft by the stern, when motoring, so that the bow barrels are only just in the water, you may be able to get enough performance to move the raft with the lawnmower motor. You may also want to look at getting an outboard with a stuffed motor and rigging this with a vertical shaft lawnmower motor of the same horsepower. This might even give you a neutral and a reverse gear!!
    Best of luck with the project, sounds like fun!!

  13. Chaogen
    Joined: Sep 2008
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    Location: South Africa

    Chaogen Mechanical Engineer

    Just as a matter of interest I quickly wanted to add n photo of a raft a mate of mine built for his civil engineering club. In total he used nine drums. Each pontoon was made using two wood poles and strapping the barrels to them with, wait for it.. cargo straps.. Rafters connected the pontoons together with nails and wood boards was nailed on top to form the floor. The dimensions if I recall was approximately 6 by 6 meters and we had about 15 people at one stage camping out on it. It was only designed to hold for a day, and it was used on a small lake. But it was disassembled and has been reassembled two times now.
    As for recommendations, definitely strengthen the structure. They did find out that putting up a sponsor banner turned it into quite a sailing yacht and caused it to float to the other side of the lake. They also found out that t is not the best water going vessel when being towed by a boat when it almost turned into submarine.
    I can’t remember what it cost. The barrels were sponsored and the wood board were the most expensive components. I’ll speak to him and find out, but that would obviously depend on your local prices.

    Best of Luck.

    By the way, It took about 3 hrs to build by two guys.

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