18 ft. Fishing Boat - strip construction

Discussion in 'Boat Design' started by Peg Leg Don, Dec 16, 2021.

  1. Peg Leg Don
    Joined: Mar 2021
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    Location: Bemidji

    Peg Leg Don New Member

    Hey!

    Looking forward to getting some feedback as I go to work on a major project.

    I’ve been into woodworking for forty plus years, and dabbled in boat building over the past 23 years. My most notable project was an 18 ft. decked canoe (cedar strip). Loved the way it turned out in both beauty and function. Having retired a few months ago, I’m looking to dive into a big job.

    This is the dream:

    18 ft.+ fishing boat - strip construction. (Do not want to do plywood for the surface of the hull! Though I’m okay with plywood for structural members.) Thinking to use strips that are ⅝ X 1 ⅝ - coved and beaded. Have a good batch of both western red cedar and northern white cedar. I would put 1 layer of 6 oz. glass fabric above the waterline and two layers below the waterline. I would put an additional layer of 6 oz. on the inside, while filleting all of the connections between hull and stations. Permanent stations would be 18 inches apart. Tunnel hull (with a 24 inch tunnel). 7 ½ ft.+ beam. Won’t ever wish to go over 35 mph., so I’m thinking 115 HP. Hoping to keep it under 1,000 lbs. before motor, though if it goes over a little, no big deal. Center console.


    Guessing that the project is going to be 700+ hours, spread out over 20 months.


    Been searching high and low for a design, but everything I’ve found in the ballpark is plywood or fiberglass.


    Thoughts?
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Well, the skins are too light based on my gut for 115hp. Unis also offer very little on the horizontal, so there are problems with the concept.

    How did you arrive at the laminate schedule?

    Honestly, that is the schedule for a canoe..not a speed boat subject to G forces.

    also, a boat like this should not be amateur designed; find a plan you like
     
  3. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I have the complete blueprints to build this 17ft skiff. The shell is made of plywood but could be done, without changing anything else, by strip planking. If it suits your needs we may be able to reach an agreement.
    Skiff Model04-6.gif
     
  4. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    115 hp seems like a lot for 35mph.
    I had a friend who had an old boat (fiberglass) that did 50+ with 60 hp.

    You can change some fiberglass boats to strip planked, but you would be better finding one designed for it.
    I'd be concerned with choosing the construction thicknesses before knowing the boat and horsepower.
    The construction you mentioned is just slightly heavier than canoes and kayaks usually use at 3mph rather than 35.

    Good luck.
     
    fallguy likes this.
  5. wet feet
    Joined: Nov 2004
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    Location: East Anglia,England

    wet feet Senior Member

    I agree with the comments regarding the need for an engine as large as 115Hp.My instinct tells me that 40-60 ought to be sufficient-unless you had a very good days fishing and need to get a vast catch home before it deteriorates in the sun.I would hope you get nowhere near 1000lbs without the motor and recommend gathering some data on both your stock of cedar and maybe weighing a few sheets of plywood.I would be surprised if the cedar skin was much over 240lbs,with around the same for the majority of the keel and gunwhales.Where would you expect the weight to come from?
    Plans are out there,but may cost some money but it will be money well spent if it lifts the quality of the boat.
     
  6. Phil_B
    Joined: Mar 2019
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    Location: New Zealand

    Phil_B Junior Member

    I'll start with an anecdote which is supposedly true.

    A Civil Engineer was visiting India and he saw a few hundred labourers digging the foundations for a building.
    "Why don't you use a mechanical excavator and get the job done in a day?" he asked.
    "Ah, you see, Sir, this is a job creation scheme and we are providing work for all these labourers for many weeks. So using shovels is actually a benefit, in this case".
    "Well, if it is to provide work for a lot of people for a long time, why are you not using teaspoons instead of shovels?"

    OK, if you are set on a strip planked boat, then it is likely to be a round bilged, displacement boat, not a hard chine planing boat. Converting a hard chine planing boat into a strip planked boat instead of using sheet plywood is the equivalent of using a shovel to excavate the foundations. You are simply making work for yourself to no good reason. But if that IS your aim, then you COULD build the boat out of matchsticks ... the teaspoon option. Ahem! Plus the weights, internal structure and scantlings would have to be recalculated as a simple "Replace 5/8ths plywood with 5/8ths strip plank" will not produce the same boat if converting from sheet ply to strip. Buy a set of plans of a boat designed around the building method you prefer.

    A round bilged displacement boat will be well suited to strip plank building and will require a much smaller HP engine which will be much cheaper than a 115 HP which means that the money can be used for other things (radio, fish finder, etc.).

    If you are willing to go up to 20 feet, then Jay Benford has a one that might suit you:

    Benford Design Group http://www.benford.us/index.html?pcty/

    (Click on the images to enlarge them).

    He recommends an 18 HP SAAB diesel or a Yanmar 4JHBE. His book "Pocket Cruisers and Tabloid Yachts" has the plans (offsets, construction and profiles) if you want to go that route, though I would recommend buying the plans from the designer for the support you may need during the build.
     
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  7. Peg Leg Don
    Joined: Mar 2021
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    Location: Bemidji

    Peg Leg Don New Member

    First, let me clarify a few things:
    - I won't be asking anyone to send their grandmother's sterling silver spoons for this project.
    - I'm not stuck on the idea of putting a 115hp engine on this boat. If a lower HP engine would get me on plane fully loaded, it would save weight, efficiency, money, etc.
    - I do wish it to plane. Top end of 35 mph is fast enough.
    - From my reading, there's no reason 5/8" thick strip planking can't be just as strong as plywood if a person adds the right layers of epoxy and glass. Just need to get a handle on what those layers need to be.
    - I'm at peace with the notion that some amount of this boat is going to be made out of plywood. Just what all is the question.
    - If someone is aware of a DIY design out there that's in the ballpark of what I'm after, send the link.

    I'm going to put up a drawing of what I have in mind. It is just a drawing! I would plug it into a boat design software before going forward.
    IMG_1423.JPG
     
  8. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Expound on the sor a bit pld.

    do you want strip so it can be a round bilge?

    do you want a flats boat or a deeper vee?

    where will the boat be used mainly?
     
  9. fallguy
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    fallguy Senior Member

  10. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    From what I can deduce from your drawing, apart from the side that, having double curvature, would make strip planking necessary, other areas of the hull, such as the bottom and the wet deck could be made of plywood. The interior parts, of course, would be made of plywood or solid wood. It's just a suggestion.
    In both cases, if fiber is added, it is fundamentally to seal the joints and to give it a better external appearance. It has no more difficulty defining the layers to wear if they are not considered as resistant elements.
    The constructive system does not produce the lightest possible hull, so do not think that planning is going to be easy.
    I don't have your project in my garage, but if you can't find someone who has already done it, I could help you design exactly the boat of your dreams.
     
  11. Peg Leg Don
    Joined: Mar 2021
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    Location: Bemidji

    Peg Leg Don New Member

    Appreciate all of your thoughts!

    Let me give you all a little more background. As for wanting to go with some strip construction, I have two reasons. I have to admit that I find it to be really beautiful. I love the way my canoe looks, and I love the way the old ChrisCrafts and Rivas look. As I've said, there shouldn't be any reason this hull won't take a beating from wind and wave if I get the right layers of epoxy/glass. I made up a panel (44" X 11") of red cedar strips, 1/2 thick, with 1 layer of 6 oz. glass and 3 coats of epoxy on one side and 2 layers of 6 oz. glass and a total of 4 coats of epoxy on the other side. I found it to be much stronger than .125" aluminum or unglassed 1/2" plywood.

    As for the hull design that I want, here is my reasoning. Tunnel hulls by reputation come up out of the hole to plane quicker, a finer entry is able to cut through the waves better giving it a smoother ride, it moves across the water more efficiently (burning less fuel). It provides a wider, more stable platform to fish off of. With a center console, a fisherman and the net guy can work 360 deg. around the boat with minimal barriers. In that the lower unit of my engine won't have to go quite as far down as a regular deep V, I can worry a little less about the rocks that can sneak up on a person in northern Minnesota or Canada. While I'm not exactly after a flats boat, managing shallower water is a plus. I'm also hoping for it to be a bit more trailerable.
     
  12. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Bemidji! I am in Minnesota as well.

    Sorry, but your rationale on the glass schedule is not considering the bigger picture of g forces. An aluminum boat is built differently, with a somewhat significant web of inside structure. A typical cedar strip boat does not get that same internal structure.

    If you ran a 6 oz woven into a Canadian shoreline which is always rocky; you'd for sure destroy the laminate.

    Every additional horsepower added increases the demands of the hull and skins.

    Most of the boats for Mn and Canada and LOW or Superior or Erie are deep vees. Not all, but great many.

    A really large boat is the C19 which I would probably build if I were to stay here.

    https://www.boatbuildercentral.com/StudyPlans/C19_STUDY.pdf

    All plywood, faster than cedar strip. We see no center consoles or few here; boats usually get a lid to help dry out cold rides.

    Any wood boat for MN/Can needs a steel cutter on the keel. It doesn't have to be fancy, but it needs to be there up front for beaching. It might save your boat if you hit anything as well.
     
  13. Peg Leg Don
    Joined: Mar 2021
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    Location: Bemidji

    Peg Leg Don New Member

    Okay ...
    Here is an updated cross section of my design. I'm at peace with the idea that much of this boat is going to be made out of plywood. With that said, I do wish for the side from the chine to the sheer to be strip construction. I'm sending along a photo. It's not to scale! I'm a little torn as to whether to use 2 layers of 8 oz. or 2 layers of 10 oz. across the bottom and through the tunnel. A steel or hardwood strip along the keel is a good thought.

    Forgive my horrible handwriting!
    boat finish cross section.jpg
     

  14. johnnythefish
    Joined: May 2016
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    johnnythefish Junior Member

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