battens and framing question

Discussion in 'Wooden Boat Building and Restoration' started by wudenbote, Sep 7, 2009.

  1. wudenbote
    Joined: Aug 2008
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Middleville Mi

    wudenbote Junior Member

    On most boat plans it appears that the battens are merely fastened onto the frames rather than inletting the frames to accept the battens. (talking about inner battens here) Is there a particular reason for this or is it just to save labor? On a totally flat bottom dory such as I am building is there any reason why I can inlet (let?) the battens and keelson into the frames thus providing a flat surface overall to fasten the plywood bottom sheeting to? Thanks..your input is much appreciated!
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    There are as many building methods that "let" (notch) the battens into the frames as those that don't. There are several reasons for doing it either way. If the batten isn't notched to the frame, then you can use thinner frames (because they aren't weakened by a bunch of notches), but more importantly the frame doesn't lie against the planking. This creates natural limber and weep passages, so moisture and boarding water can travel to the drains or low spot in the hull to be pumped out. It's a lot easier to clean out a hull, when you don't have a bunch of frame bays, stringers and battens "compartmentalizing" the inside of the boat.
     
  3. wudenbote
    Joined: Aug 2008
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Middleville Mi

    wudenbote Junior Member

    Par: Thanks much for your input! Doesn't inletting them to the frames make a stronger "unitized" construction after everything is screwed and glued? I was thinking of glueing some short pieces of pvc through the frames to allow water to travel to the bilge pump. True, you would still have a more difficult time swabbing out the compartments. One other question...are the terms BATTEN and STRINGER used interchangeably and mean the same or are they completely different items? Sure would like it if you lived next door. :)
     
  4. marshmat
    Joined: Apr 2005
    Posts: 4,127
    Likes: 149, Points: 63, Legacy Rep: 2043
    Location: Ontario

    marshmat Senior Member

    If everything's going to be glassed and epoxied into a single piece, then yes, I can see where you're coming from when talking about a "unitized" construction.

    You can't just notch out frames willy-nilly, though, especially in conventional planking-on-frame construction methods. Notches in a structural member weaken it substantially and can create stress concentrations, places for rot to start, and other undesirable conditions. And if everything's been dimensioned properly at the drawings stage, the framing system shouldn't be a weak point to begin with- so more beefiness might just add weight with no real benefit.
     
  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Frames are typically used in plank (which includes plywood) over construction methods. This suggests the structure isn't monocoque and that you create stress risers, point loading, weaken futtocks, etc. if you notch things that aren't shown notched in the plans.

    Even with monocoque building methods, there's not much worse then having to take a sponge to every little nook and cranny in the boat, because water can't flow to the low point or out a drain. If you want rot fairly quickly, then make lots of little compartments on the bottom of the boat, with no natural way for these to drain easily.

    So, in the end it depends on what you're doing. What design are you building?
     
  6. wudenbote
    Joined: Aug 2008
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Middleville Mi

    wudenbote Junior Member

    Thank you for your input. The "plan" is in my head and partly on paper. I based it on the Glen L Hunky Dory design but thought that notching battens into frames would make a stronger unit. Call me a tradionalist but I have no desire to glass or encapsulate the boat. To my way of thinking, you no longer have a wood boat. :) It will be screwed (using bronze screws) and epoxied at all contact points.
     
  7. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    This boat is a overly heavy built power dory. Unless you have a good bit of designing experience, I'd recommend you just use the plans. You don't want to build an out of balance boat that doesn't do any of the things you want it to do. Why would you want to make a clearly over built boat stronger? And if you have a reasonable answer for this question, then why are you trying to make a dory do something a different type of boat may be better suited for?
     
  8. wudenbote
    Joined: Aug 2008
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Middleville Mi

    wudenbote Junior Member

    Par: the specific purpose of this boat is fishing Lake Michigan a couple miles off shore for yellow perch...mmmmmm good. From past experience I know how fast and how rough the big lake can get. I wanted something that would be in my budget and would be able to take some pounding if the weather turned on me and I had to head for shore in rough conditions. Thank you for your concern. By the way..it will be powered by an inline 4 cylinder Graymarine of 30 HP.
     
  9. boat fan
    Joined: Sep 2008
    Posts: 717
    Likes: 17, Points: 18, Legacy Rep: 435
    Location: Australia

    boat fan Senior Member

    There is an Italian builder of high end , fast power boats similar to the classic Rivas , who does not notch stringers into frames.

    He claims that tight contact of planking ( in his case plywood ) causes " hard spots " at the frame / planking interface. He states that on high powered craft this can cause weakness due to high stress concentrations after many repeated stress cycles , mainly caused by the boats pounding at speed. ( In line with PAR`s reference to point loading and stress risers etc......)

    This may not be of concern to you of course.

    Unfortunately I cannot recall who the builder was.His boats however were very high end , classic , and classy.
     

  10. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I would consider something entirely different then a modified dory for your application. I use to live in Chicago and that lake is well known to me. The dory is great if you're hauling nets of fish over the side or driving right up on the beach often. What the dory is best suited at is "settling" even with a load. By this they are designed to load down and sink uniformly with load increases, which is a handy feature when you are coming in with 2 or 3 tons of fish in a 23' boat.
     
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.