an even bigger Tolman skiff

Discussion in 'Powerboats' started by Westfield 11, Jan 23, 2014.

  1. Westfield 11
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    Westfield 11 Senior Member

    I am working on a modification of the Great Alaskan version of the Tolman skiff and have a couple of questions.

    I am able to change the width of the chine flats and the dead rise during construction, the stock boat has 5" chine flats and 13* dead rise at the transom. I plan on adding a couple of inches to the chine flats on each side to give a bit wider beam for living space, but I am concerned about the boat pounding with the wider chines, would a bit more dead rise help smooth the ride in a chop?

    Will, say a 2* increase to 15* in dead rise increase buoyancy to a noticeable degree when I am already adding 4"s to the beam? The boat would be normally loaded on the heavier side of the spectrum with cruising gear and stores, etc. And I would like it to plane easily but still ride well...... A compromise, I know.
     
  2. tom28571
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    tom28571 Senior Member

    Transom deadrise does not have a great effect on the ride of a boat. Deadrise where the bottom hits the water is the important thing but low transom deadrise in this case means more twist to the bottom panels in order to maintain the same deadrise at the water entry at speed. Increased beam requires greater draft to maintain the same deadrise. If you want the topside immersion to remain at the same height, and you should, the weight must increase to match the greater volume.

    As for ease of planing, more deadrise and greater weight are both negative factors and power must increase. On the other hand bottom loading may be greater or less with the greater waterplane. Its the design spiral that you must go through several times to match the compromised you are satisfied with.

    All planing boats will pound and its a matter of conditions and at what speed.
     
  3. Milehog
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    Milehog Clever Quip

    You are opening a can of worms, IMO.
    Have you seen the Olga 28?
    Prolly not enough boat for you but it has some ideas which you may like.
     
  4. Westfield 11
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    Westfield 11 Senior Member

    Thanks for the response, I was thinking of altering the molds a couple of degrees at each location. This would give a 2* deeper vee amidships as well. I could always change only one mold leaving the transom angle the same and not altering the draft or the buoyancy.

    The beam increase would come from the chines, not the bottom so I would hope not to change the draft in that manner. I am aware that that will also change the volume and thus the draft for a given load compared to a stock design.
     
  5. tom28571
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    tom28571 Senior Member

    Don't understand?
     
  6. Westfield 11
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    Westfield 11 Senior Member

    The chine flats would be made two inches wider on each side. The vee bottom would stay the same width.
     
  7. tom28571
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    tom28571 Senior Member

    This is where you confused me. Adding width to only the chine flats will not increase interior living space.
     
  8. Westfield 11
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    Westfield 11 Senior Member

    Now I am confused, wouldn't adding 2" to each chine flat move the sides 4" farther apart? Given a 4" wider floor, how does interior volume stay the same? Or is it a practical matter of the interior width increase not being noticeable?

    FYI, the stock boat has 5" wide chine flats, I propose making them 7" or 8" wide on each side.
     
  9. tom28571
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    tom28571 Senior Member

    OK, now I see what you wish to do. Its certainly possible and easy enough to do. One drawback to wider chines is noise, both underway and especially at anchor. Can we assume that you intend to taper the width toward the bow? You have to be careful how a wide chine is built to have a robust construction. I carry the topside all the way down to the flat edge and then add the flat to inclose the triangle. That is very rigid and strong.
     
  10. Westfield 11
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    Westfield 11 Senior Member

    Tom, if I get you right, you rest the hull side on the chine flat then use liquid joinery and tape on the inside and tape on the outside? As opposed to laying the sides against the chine and trimming them flush with the bottom and then doing the putty and tape as before? It would be the easiest way for an upright build, but the classic Tolman method is to build upside down and lay the sides up against the bottom. If done that way it is easier to scribe the sides flush with the chine bottom.

    I am planning that the chine flats, which I will taper towards the bow, will enter the water down by the foot of the berth and not at the head!
     

  11. tom28571
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    tom28571 Senior Member

    I do build right side up and lay in the inside chine filet first just as you suppose. Much of the interior is built prior to first turnover. Turning over boats of this size is easy so two turns is no problem. I admire Renn and his boats although they are not best for what I do. I prefer more bottom waterplane for interior room and efficiency which is where you seem to be headed.
     
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