stand up walk around stability in a rowing boat

Discussion in 'Stability' started by thudpucker, Oct 12, 2008.

  1. thudpucker
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    thudpucker Senior Member

    I have a 15' Aluminum Jon boat which is pretty stable when I stand up and walk around in it. That's important for an old guy.
    It has a 25 Hp outboard (100 Lbs) which most of it is above the gunnels.

    I'm wondering if I could have a boat like that for rowing?
    I'd like the bottom to be 48" wide and the sides low enough that slight winds are not a problem.
    The Bow should have some rise to it so the bow does not try to steer the boat when rowing.
    I dont want the 'V' bottom up front. That makes a boat 'Tippy'.

    The problems show up when you need something that's just out of reach. You have to stand up and go get it. Now the boat wants to slip or roll, causing me to lose my balance and when I lean to grab something for stability, that causes the boat to go over even further.:rolleyes:
    That's the problem I'm trying to solve.

    For this prospective boat I have three other motors and I usually dont have any need for speed. Right now I can row 6 miles or so fairly easily. But in a couple years I might have to use a motor to get me to-and-from the fishing holes. I actually prefer rowing to motoring. But I want the big wide stable platform.

    So what other factors are involved in making the boat stable?
     
  2. alan white
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    alan white Senior Member

    A boat twice the length would be twice as stable, meaning you will get stability with length as well as beam.
    However, length beyond a certain point will only be efficient with greater horsepower---- if you're developing a mere 1/4 hp yourself, a shorter boat would make more sense. This also makes for more beam, which is a good thing.
    There's a limit to stability with efficiency in a monohull------ and I'm sure a few will suggest a catamaran. This might actually be a good choice for your particular needs, as a catamaran is very stable while reasonably efficient too.
    There are also flat iron skiffs, which are pretty stable due to their wide, flat bottoms. Some are very good rowing craft while also being decent power craft.
    A suggestion would be to try a flat iron skiff out and see if it suits you. Most likely, it will be a wooden boat, probably plywood. Itr is certainly about the simplest boat you could build.


    Alan
     
  3. thudpucker
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    thudpucker Senior Member

    Very good suggestions.
    I had a pram when I was younger. Even then, when I was limber I had trouble trying to reach everthing in that boat without fear of tipping.

    Getting out at the beach was the problem. I'd get close to the beach and then Row like hell and ram the prow up onto the beach. Then, as my weight shifted in the boat while getting up on my feet, the damnd thing would slip off the beach and I'd have to grab an oar and pole the thing back to the beach.
    Always I'd be getting wet and spilling stuff in the boat with all that clumsiness.

    I guess I'll google "Flat iron skiffs" and see what that is.

    I looked at one of those Small cat's. The Fiberglass pontoons with a rowing seat between them. I thought about it, and decided I'd have to have a lot more room for stuff that wouldnt let the stuff fall into the water between the pontoons. I did not try rowing one.

    As you probably know, a 12' or 13' skiff for rowing is just about optimum for one guy. Or in my opinion that's the truth.
    I wanted more width at the bottom, longer oars and my sliding seat for easy access to the front and back of me.
    I'm also gonna sit up a little higher so my legs can stretch out a bit.

    You need room for a Cooler or a live well. You need to keep fish alive for some time when the fishing is good. I dont have a pump in this little boat. I just dip out some of the old water with my bailing bucket, and then pour some fresh water into the live well.

    A Battery for Night lights and the Fish Finder. Maybe even a GPS for marking spots.
    I quit using a large deep cycle battery and went to a smaller Lawn Mower battery.
    I also need a waterproof container for my Cell Phone and my Wallet. In case I capsize or some other thing put's a lot of water in the boat. This can be clear plastic so the CellPhone can recieve.

    And the floatation for the boat.
    I was capsized in a 12' Plastic boat that didn't have any floatation.
    The Six gallon Fuel tank held that boat up, my uncle sat on the boat so it was holding him up as well, and the 10 Hp outboard was hanging by the fuel line, it was being held up by that gas tank. I was amazed.
    The Bow had a little air trapped in it, so I had a cushion under one arm and the bow under the other arm. Exciting for sure but it demonstrates the need for floatation in the boat. After that experience I wore a PFD all the time I was in one of those small boats.
     
  4. Ramona
    Joined: Feb 2007
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    Ramona Senior Member

    I picked up a 14 foot off the beach fibreglass catamaran off Ebay for just this job. Took off the tramp and will construct a rowing fishing platform. Boat had no mast or sail but on a good galvanised trailer. The lot cost $82. Picked up two windsurfer masts from the recycle shop for $5 each for the oar shafts. Probably take a small outboard too if necessary. No need to spend much. Plenty of old beach cats laying about.
     
  5. hmattos
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    hmattos Senior Member

    Here in the UK we were asked years ago to design a small and very stable tender for customers to row out to their cruisers where they have to stand in the tender to climb into the bigger boat.
    Have a look at www.explorermarine.co.uk and click on tenders. Our Explorer 225 model is only 89 inches long, but is one of the most stable types around here and can still be carried by one person down to the water. There are wheel options as well for those who want them.
    The key issue is to have a very square cross section of hull with very sharp chines. If you are looking to make one youself, take the time to make a model and test it in the bath - as we did - because that taught us a lot. Remember that the bow needs to accomodate the reduction in freeboard when the boat is being pushed forward on each rowing stroke.

    Hope this helps
    HM
     
  6. ancient kayaker
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    ancient kayaker aka Terry Haines

    These are the factors involved in stability as far as I know, although there are more knowledgeable folks on this forum:

    If the hull shape is fixed stability increases as the length; so does displacement however, so loaded weight must increase to keep the waterline at the designed level. Stability increases as the cube of the beam whereas displacement increases as the square so that's a more obvious way to increse stability. However, short fat boats are slower than long skinny ones.

    Stability also depends on the CoG. Although a wide flat bottom seems the way to go, a rounded bottom or narrow flat bottom with garboards angled up to the waterline gives you the same waterline beam with a lower CoG. Found that out the hard way ...

    The above is all about primary stability; secondary stability is different and deals with the behaviour of the boat when heeled over or when a big wave hits from abeam. High secondary stability with lower primary stability means as the boat rolls its resistance increases; a desirable thing. When primary stability exceeds secondary stability, which is easy to get with a flat bottom, the boat waits until you are off axis and then tries to throw you over the side. Been there, done that ...

    A bit of mass helps to slow the boats movement when you are moving around in it, which gives your reflexes time to kick in. Hard chine hull shapes tend to dampen the rolling motion.

    Of course you get to pay for stability, just like everything else. In a muscle driven boat that means working harder and moving slower. As a card-carrying member of the old farts brigade I'm sensitive to nuances like that.
     
  7. alan white
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    alan white Senior Member

    Finally, one method that makes for stability when stationary is a long pole with floats (mooring balls, etc.) at each end, affixed across the beam. The floats are far enough out to prevent anything more than minor tipping. The rig disconnects and goes into the boat the long way.
    This allows the advantages of a really efficient rowing craft like a banks dory, wherry, or peapod (Gloucester Gull by Bolger is a great example of a perfect rowing machine) while rowing.
    But when you're at your favorite fishing hole, those two big floats (at say, 4 ft out to each side) offer real security. A one cubic foot float would thusly support an additional 180 lbs on the gunwale of a 4 ft beam rowboat to the same angle of heel!
    This is kind of an extended sponson idea. Foam could be shaped to fit into the ends of thw boat, and the pole could be steamed or laminated to both follow the curve of the boat's side AND bow over the boat when mounted.

    Alan
     
  8. ancient kayaker
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    ancient kayaker aka Terry Haines

    Great notion. Even simpler, buy a couple of the bouyancy bags that kayakers put on the end of the paddle to make an unassisted re-entry after tipping, and attach them to the oars. Then all you need is a simple modification to a thwart to attach the oars, or a few lengths of cord will do.
     
    Last edited: Oct 13, 2008
  9. Tcubed
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    Tcubed Boat Designer

    The requirements of efficiency in pulling boats are generally incompatible with requirements of large righting moments at small angles.

    However, a considerable amount of large angle righting moment is quite natural for efficient pulling boats due to the flare. This is in the case of outriggerless pulling boats which need the flare to reconcile the need for a wide oarlock base with the need for skinny waterlines.
    This produces the characteristic feel of pulling boats with the "wobbly" feeling when upright but seemingly impossible to push the gunwale under when heeled.

    These stability curves can be somewhat optimized whilst still retaining great rowing characteristics in a pram. I'll try to post a picture of a norwegian pram so you see what i mean.

    The other obvious option is to scrap the monohull concept and go with some kind of cat or outrigger hull.

    The idea of removable floats on the oars or similar arrangement sounds good as long as it is very quick and easy to setup and remove.
     
  10. thudpucker
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    thudpucker Senior Member


    That statment identifies the problem.
    If you can row it, it aint gonna be stable to get up and walk around in!:mad:

    Over the years I've had some good boats for rowing. If they are big enough to be stable for an old guy with decrepit balance control, they are usually too big for an old guy to row.

    I have a 15' Jon boat with a 54" bottom which is a "Outboard motor only" craft.
    But it's stable.
    The Motor quit in a storm about a mile off the nearest beach.
    I sat down on the bow and paddled for a mile in waves coming up over my waist. Occasionally I'd have to go back and turn on the bilge pump to empty the boat, then go up front and paddle some more. It took me nearly an hour to do that mile.:rolleyes: It's about the wettest I've ever been when I wasnt swimming.

    That is a very stable boat. I'm sure I could never row it.
    The oars would have to 12' at least and I'd have to leave the outboard down in the water to use as a tiller.

    I dont think Removable float, outriggers or any thing else would be practical for a fishing boat. I spend too much time in the brush, near the shoreline rocks etc. I'd have my line tangled in that stuff all the time and my temper would be gone in no time.
     
  11. srimes
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    srimes Senior Member


  12. thudpucker
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    thudpucker Senior Member

    That's a good one. Thanks. It sure looks do-able for an old guy in a drafty barn.
     
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