shallow water oars

Discussion in 'Boat Design' started by river runner, Aug 9, 2011.

  1. river runner
    Joined: Jul 2011
    Posts: 172
    Likes: 6, Points: 0, Legacy Rep: 91
    Location: Colorado

    river runner baker

    In my opinion, people who operate row boats in shallow water, such as drift boats and jon boats, worry too much about the draft of their boat and not enough about how much water their oars need to get a purchase. A better design for shallow water, than the traditional oar, would be to have the blade out of line with the shaft. The shaft coming in at the upper inside corner of the rectangular blade. Racing shells actually use a blade like this, though more squarish than the long thin rectangle I'm picturing. It is more efficient this way, even in deep water, because you can get the whole blade area in and out of the water with less up and down motion.
    I'm making a simple version for my river dory by taking oversize plastic blades and cutting off the lower outside corner. The blade area should be about the same as standard blades, but you will be able to get more blade area in the water, when it is shallow, than you can with un-modified standard blades.
     
  2. wayne nicol
    Joined: Dec 2009
    Posts: 139
    Likes: 4, Points: 18, Legacy Rep: 34
    Location: Queen Charlotte islands, B.C.

    wayne nicol Senior Member

    we used to use assymmetric kayak blades for all our white water kayak applications- and we built and designed our own- this function varies a bit as our blades had a dihedral cross sectional shape( for a bunch of reasons- but mainly to reduce flutter in the hand- this in turn allowed for a "looser" grip- and ultimately better control!)

    but back to the point- the surface area of the blade either side of the centerline( of the shaft) needs to be the same- otherwise you will have incredible flutter- and it will be hard to hold onto the shafts under load.
    as the water pressure is applied to the blade- it needs to be even , otherwise the blade will twist in your hand- the harder you pull the greater the twist.- and as the water sheds from the blade under pressure- it will do so unevenly- causing flutter.
    if this vague description is a bit confusing- i will do a hand sketch this evening and post it here.
    unless of course you are using fixed rowlocks- but the twist will still place incredible- and unneccesary torque on the rowlocks on the boat
     
  3. Stumble
    Joined: Oct 2008
    Posts: 1,896
    Likes: 71, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    Wayne,

    Instead of using a L shaped paddle with the blade angled out, what would you think about a balanced design, where it is shaped more like a T?

    No idea personally. Paddles to me at just part of what the coast guard mandates I have.
     
  4. river runner
    Joined: Jul 2011
    Posts: 172
    Likes: 6, Points: 0, Legacy Rep: 91
    Location: Colorado

    river runner baker

    I am familiar with assymetrical kakyak paddles, as I have a few. A couple Werner's and an Epic. The design I mention goes along with this thinking and actually gives a better balance of pressure, the same as with a touring kayak paddle. A standard oar has more pressure on the lower half of the blade because more of the lower half of the blade is in the water. By cutting off the lower outside corner, which is basically what they do on touring paddles, you even out the pressure.
    Stumble: I'm not picturing what you mean by a T shaped oar, but it sounds like it would actually make the problem worse. You want the long dimension of the blade to be parallel with the surface of the water.
     
  5. portacruise
    Joined: Jun 2009
    Posts: 1,137
    Likes: 40, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Oars are not practical in shallow water if it is for extended distances like where I do my boating. It is difficult to keep from hitting bottom or protruding rocks with severe consequences when using a fixed pivot on a heavy boat. There is a lot of PORTAging if you don't have an extremely shallow draft boat of 4" or less, even though the water averages from 12" to 24" punctuated by 6' deeper holes. So the best craft is a lightweight pontoon kick style boat where one can push off bottom, hop on or off instantly and use a kayak paddle to keep you away from the banks. You let the river current do the work of propulsion and simply stand up or paddle to the bank if you want explore an area.


    Porta
     

  6. wayne nicol
    Joined: Dec 2009
    Posts: 139
    Likes: 4, Points: 18, Legacy Rep: 34
    Location: Queen Charlotte islands, B.C.

    wayne nicol Senior Member

    yup, youre spot on RR.
    absolute best of luck with your project.
    tight lines!!!
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.