need advice for sea going small boat

Discussion in 'Boat Design' started by scubasteve89, Jun 10, 2012.

  1. scubasteve89
    Joined: Jun 2012
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    Location: Ireland

    scubasteve89 Junior Member

    well how is every one? i am looking for some advice on my boat, i havent a clue about boats and while id love to make a proper one i cant afford it, i made a boat using the fiberglass roof off a transit van last year. and i put a starlet engine into it and it worked grand. then my buddy crashed a tractor into it so now i have to fix it and im going wrapping the whole lot of it with 2 layers of 450gm fiberglass. what im wondering is is that enouf? and would it be ok in a mild see? because i am thinkin of doing a run down along the cost for charity as a tribut to my 15 yr old cousion who died, the run is 100 miles. the boat is 16ft by 4 1/2ft flat bottom. its 6'' below water at rear and 2'' at front, i havent started fixin it yet so any advice to make it more stable would be takn on board. thanks
     
  2. Tad
    Joined: Mar 2002
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    Location: Flattop Islands

    Tad Boat Designer

    Steve,

    What type of resin are you using to bond the new glass on? Whats the damage, is she broke clean in half or just one side crushed or just a hole?

    For the open water passage you want some positive floatation in the boat. Air bags, glassed in watertight boxes, or (best) some foam glassed in. Even sealed plastic jugs tied in will work for this......
     
  3. SamSam
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    SamSam Senior Member

    No, it is not seaworthy.
     
  4. thudpucker
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    thudpucker Senior Member

    There have been a few survivors of a similar mission. Read up on them. They will certainly point out what needs they had and how they coped.
     
  5. scubasteve89
    Joined: Jun 2012
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    scubasteve89 Junior Member

    its cray valley en30 polyester resin. yea thats a good idea tom i could fix barrels to the side of her full of foam. just one corner is all cracked but il cover the whole thing to make it stronger. also my out put rpm is 1700 at 35 hp could any one show me a pic of the kind of prop i would nead and il try copy it with some steel! she dosent have to be pretty or efficent she just has to go which probly is not what any entuest on here wants the here!
     
  6. Tad
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    Tad Boat Designer

    Oh come on guys.......Irish folk have been going to sea in marginal boats for what, 1500 years or so? http://www.ics.villanova.edu/in_saint_brendan.htm

    Steve, look for a prop roughly 15" in diameter and three bladed. ebay and craigs list are the best sources. Trying to build a workable prop is probably not worth it and will just create problems.
     
  7. scubasteve89
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    scubasteve89 Junior Member

    thanks tod! it is for the memory of my cousion after all, that was an intresting read i mite name the boat the st brenden! shur if thoes lads went to america, a 100 mile spin down the cost isnt too bad! i found a prop its a volvo penta prop 14.5x 19 would that do?
     
  8. anthonytlh
    Joined: Jun 2012
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    Location: Mashes Sands Florida

    anthonytlh Groupergiggin

    Great I dea about using the roof of a van...Coool
     
  9. davhill
    Joined: May 2012
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    davhill Junior Member

    A boat made from a van roof? Tis hard to tell if this is an utterly foolish project, or a reasonable proposition... Some photos of the thing might help. But ok, off to sea in a marginal boat we go...

    First, lets assume you want to strengthen this hull to make it more stable and seaworthy, and not just to make it survive the next encounter with your buddy's tractor. Boats are not supposed to run into tractors, so that's not one of the usual design parameters.

    Adding a couple layers of glass & resin will make it quite a lot heavier, which should make it more stable, but will also lower the freeboard and make it slower. You mentioned how deep it rides (6" at stern, 2" at bow) but how much freeboard it has (how much boat is /above/ the water at the lowest part of the rail) is probably a more important measure when you are considering seaworthiness. Its water coming over the side you have to worry about, not how deep or shallow it drafts.

    The boat may benefit from stringers and/or frames and/or bulkheads to strengthen the hull without adding thickness to the skin, especially to prevent flat expanses of fiberglass from windowpaning. You must already have some main stringers as engine beds, but more framing may be beneficial ...

    What's a "starlet" engine? From a Toyota Starlet automobile? 1000cc?

    16'x4.5' is fairly narrow for its length, for what I suppose is basically a scow hull. If you overpower this thing and turn sharply you are apt to flip it in a heartbeat. You might test its stability in turns, in calm and shallow water, before you get into any sort of sea. It should bank smoothly into a turn. If it stays flat or jumps about, its is absolutely not seaworthy. Adding a small skeg may help it track, and avoid skidding in turns.

    How does your hull react to a following sea (a wave coming up behind you)? If it rises easily to let the wave pass, you might be ok. If it poops easily (if the wave breaks over the stern) then it is NOT seaworthy.

    Fixing barrels of foam to the sides .. not quite sure if you mean -inside- or -outside-, but
    putting them outside will slow you down a lot, and putting them inside will take up a lot of room. If you can box in the spaces beneath the foredeck, side decks, and beneath the seats, and fill them with airbags or foam (in blocks or sprayed in place), then you can gain flotation without sacrificing too much space. If you can add some nicely streamlined sponsons to the outside of the rails, you may gain both stability and emergency floatation. The objective is to get enough foam on board to keep the boat from sinking when you swamp it; not to keep it dry, just to keep it from going to the bottom. "How much foam do I need", you ask? Take the all-up weight of the boat (in lbs), divide by 64 = cubic feet of foam or watertight space needed (to keep it awash but at surface.)

    Good luck.
    dave
     
  10. thudpucker
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    thudpucker Senior Member

    Just thinking about my trips across the Pacific on Troop ships. And seeing the survivors of an American P-3 landing at Sea.

    I'd think some craft you could 'right' on your own would be necessary.
    Your craft will get pitch poled, and rolled, and you'll fall off the tops of waves, and get tumbled around quite a bit.
    Anything that can come loose, and become a Missile bound to destroy your craft and batter you should be carefully and firmly stowed.

    Definitely some Air Floatation with manual pump inside with you.
    The "TOP" of your craft needs to be zipped up water proof and wind proof.
    If it's not heavy enough to stay in the water, the winds will take you off with them in whatever direction the wind is going.

    You need a way to catch rain water for drinking. Take some Light Beer with you. It wont spoil and you cannot tell from the taste whether it's contaminated.
    Your gonna sleep wet n' miserable.
    Your gonna eat Cold food. Raw Fish.

    Teeth in good shape? A tooth ache out there could really depress you.
    First Aid kit needs some drugs for Pain. Something for Sun Burn and Wind Burn and Blisters.
    At least two pair of sunglasses. Binoculars. Soap! Bathe every day to keep the Salt Itch from driving you nuts.
    You need a long handled Net. Handy for catching food.
    A life line around your craft and a life line on you every time you go overboard.
    Somehow I think your gonna need a Battery and a solar charger for it.

    A good, and well tethered Sea Anchor.
    Maybe a Harpoon to drive Sharks away.
    Probably lot's of other stuff too.
     
  11. Tad
    Joined: Mar 2002
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    Tad Boat Designer

    Good grief....it's a 100 miles, he's not crossing the Pacific. It's one long day at 8 knots..... Given a decent weather window people do this in rowboats and kayaks.

    Good advise from Davh...

    Steve, Her proper name will be St. Brendan the Navigator. :D

    I don't know what you have for a gearbox on the engine? It's important you establish shaft rotation, some engines turn clockwise (Right hand) and others turn left, the prop must be matched. It will have it's dimensions and an R or an L stamped on the hub. The Volvo prop is probably for a fast boat, which you are probably not, it will work at some RPM but not the best. Something with less pitch (second number) might be better....but I'm really guessing as we know nothing about the speed you may achieve......
     
  12. thudpucker
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    thudpucker Senior Member

    LOL, I read it wrong to start with eh?

    Your right. 100 Miles would be easy enough on a good weather day.
    Of course you cannot tell how many miles you'll travel if it turns Foggy on you.
     
  13. Saildude
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    Saildude Junior Member

    Make sure you have a compass with you - if it turns foggy turn to shore using the compass
     
  14. scubasteve89
    Joined: Jun 2012
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    Location: Ireland

    scubasteve89 Junior Member

    Thanks for the advice guys, the boat has a good steel frame all round it its well supported il put up pics after work, yea il fix barrels full of foam out side her an streamline them some bit, the back of the boat is only a foot and a half over the water line id say i will nead to ad a bit on, my shaft speed is about 1700 rpm clockwise in 4th at 5000rpm an its a toyota starlet engine with a 4spd gearbox with reverse, im modfying the back drive so the prop will be down lower and it will steer by turning the car hub its attached to, what speed would be possable /safe with 35hp an probly 1400 normal rpm
     

  15. scubasteve89
    Joined: Jun 2012
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    Location: Ireland

    scubasteve89 Junior Member

    An i can use the gears so a large pithch prob mite be ok because i plan to fly around d lake for the summer!
     
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