Motivation is back, Strake, Spray rail and hull bottom question / advice

Discussion in 'Fiberglass and Composite Boat Building' started by Mark C. Schreiter, Jun 11, 2021.

  1. Mark C. Schreiter
    Joined: Nov 2020
    Posts: 69
    Likes: 12, Points: 18
    Location: Tampa, Fl

    Mark C. Schreiter Junior Member


    So I'm back to working on my 14ft foam and glass shallow vee flats fishing boat. im attempting the build it as basic as possible for the sake of simplicity and mostly at the direction of the plans that leave a lot to desire. so I have a few questions that are not addressed in my plans.

    1. I built a surfboard a while ago and the bottom outside edges at the rear of the board are very sharp or squared off and start to round off at the middle and become very rounded and soft at the nose. i guess this helps the board from slipping out when turning. should i think about this when working on the hull of my boat? currently they are relatively square. I realize that ill have to at least slightly round for the purpose of laying the fiberglass.

    2. The designer does not include strakes in the plans but does mention that you can add them. it does not mention the shape or location or anything technical though. I realize this is a bigger conversation and can be a controversial one as well so i ask with caution. although I appreciate the information Im not to interested in the science behind them. I guess im looking for a quick and dirty rule, if one even exists on size and location. Im only planning on a 15 hp motor at this time and I would like to get into the flats and pole around.

    3. Spray rails are also mentioned in my plans but again, not much detail at all. The general feeling im getting is that spray rails basically keep you from getting wet and also keep the water off the boat and therefore helping it track better. Not sure im right on all that but im am extending the deck past the hull by several inches and im wondering if its worth shaping the bottom of the deck to act as a spray rail or add them a little closer to the water line. if spray rails are only for the comfort of the crew then ill probably skip them. the deck is pretty close to the waterline so i know its gonna be a pretty wet boat either way.

    thank you in advance.

  2. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    planing boats need sharp lines at the transom, so you make rounded corners and build them back to nearly square

    Better to ask on the forum.

    Spray rails a must for me. I wear glasses.
  3. Barry
    Joined: Mar 2002
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    Barry Senior Member

    Spray rails at your discretion, will only make the ride drier

    I would not expect the strakes to give much additional lift on a shallow deadrise V hull though you have not mentioned the deadrise.
    We put 4 only 5 inch by 3 inch strakes on our 12 degree jet boats ( 21 feet- 30mph cruise) . At 12 degrees it was our feeling that we got a bit more lift. We had started with smaller strakes on our first few boats and kept increasing the size as well as turned them down maybe about 15 degrees or so off horizontal. Inboard jets, (and outboard jets for that matter) do not (normally) have any type of skeg for directional stability and a big thing for us was the increased ability to turn tight without doing a victory roll and having the boat swap ends.

    So if your hull is flat, say 10 degrees, or less and you do not need additional steering stability, and you do have the skeg of the outboard in the water, I probably would not bother.

    Re the radius of the chine, (or strakes if you go that way) should be minimized to absolutely maximize lift, but at the speeds that you are running, there would not be a recognizable difference
  4. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

  5. Mark C. Schreiter
    Joined: Nov 2020
    Posts: 69
    Likes: 12, Points: 18
    Location: Tampa, Fl

    Mark C. Schreiter Junior Member

    solid advice. sounds like the work vs reward of installing strakes might not be worth it.

    it looks like the rear of the hull is around 9-10 degrees and towards the bow it increases to maybe 12-13.

    I'm really not looking at this build as a "boat" more like a really big paddle board with a tiller motor. with a draft of 5 inches (for the plywood version and mine is the no wood foam version, so draft will potentially change) and the freeboard of around 10 inches, i expect a pretty wet ride. the deck is a few inches above the waterline as well so i will be sealing off the bilge with expanding foam and thus have all the water drain out the transom without the use of a bilge pump.

    ive rounded all the shape edges to facilitate lamination and will sharpen them back up upon finishing.

    thanks again for the tips and advice.

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