19' Flats Boat

Discussion in 'Boat Design' started by theboatbuilder, Sep 3, 2012.

  1. theboatbuilder
    Joined: Sep 2012
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    Location: Bulverde, Tx

    theboatbuilder Junior Member

    My dad and I are trying to build a 19' flats boat our own. We have part of the design that we want to build, the sides of the boat are 20", the tunnel height is 10" (the tunnel goes all the way through like a cat boat), the tunnel width is 27" and the two hulls are 34.5" each, the boat is a total of 8' wide.
    We want the layout to be similiar to the 21' Majek Redfish Line.


    My main question is does anybody know how thick to make the fiberglass hull and what kind of mat and resin to use?
     

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  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum and don't take this the wrong way, but let me see if I have it right. You are not only designing, but building a boat, that can take you father from shore then you can swim back to? Would, asking questions about CG and CB locations be silly?

    Simply put, the laminate schedule (what you're asking for) is engineered for the expected loads you'll encounter, plus a safety margin. Spending 50 - 100 bucks on a set of plans too much?

    I'm not trying to insult you, but the questions and drawings are so basic, it's like asking where to put the wheels on the car your designing and building, from my vantage point.

    To answer your question(s) we'll need a whole lot more information about the boat. Post all the information you have; weights, power requirements, target speed, crew, obviously general dimensions, etc. and we'll see where to go.
     
  3. J Feenstra
    Joined: Jan 2012
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    J Feenstra Junior Member


    to ask the same question, but differently ; what existing boat are you trying to replicate? And what's wrong with that existing boat?
     
  4. Village_Idiot
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    Village_Idiot Senior Member

    You would likely be better off building the XF20 from the Bateau website. It should run as shallow as the Majek, without all the design mystery.
     
  5. theboatbuilder
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    theboatbuilder Junior Member

    Okay guys, theres nothiing wrong with the Majek. The Majek is one of the best shallow running flats boats in Texas, the problem is the price of it. these are the specs of the boat.

    Length 21’
    Beam 94”
    Weight 1150 lbs
    Floor Width 85”
    Gunnel Height 9.25”
    Transom Height 20”
    Max Capacity 1600 lbs
    Max Horsepower 150
    Draft 8”
    Fuel Capacity 40 gal

    And PAR, I do not have a problem spending 60 - 100 bucks on a plan, I already looked at the XF20, it is a fine boat but I do not want wood on the bottom of the boat. I want it all fiberglass, and i want a 115 HP mercury pro xs on the back. Now if i order the plans for the XF20, and build the outer shell and spray the inside with tooling gelcoat and after that has dried put a mold release wax on it and then spray my gelcoat and start laying my fiberglass, will this work? I only need to make one boat
     
  6. IMP-ish
    Joined: Jan 2011
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    IMP-ish powerboater

    I did a quick look. The Majeks aren't cheap. I found used 21s at $30,000. What is the best price you've found for one used? Take that and subtract the engine cost and trailer and add up what budget you have to do this.
     
  7. theboatbuilder
    Joined: Sep 2012
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    theboatbuilder Junior Member

    I have contacted Majek and for just the boat, brand new is 25,000. And all the used ones down here are beat to hell just because people run them so shallow and I would rather build my own. My dream boat, if i had the cash, would be the SCB Stingray but those are 65,000 + with 250 Pro Xs. It will run 75 MPH tournament loaded. I will attach a pic of the Stingray
     
  8. theboatbuilder
    Joined: Sep 2012
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    Location: Bulverde, Tx

    theboatbuilder Junior Member

    Here is the SCB Stingray
     

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  9. messabout
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    messabout Senior Member

    The Mercs have expensive looking, non standard, racing style, lower units. That boat is race ready by virtue of its propulsion system, not likely because of the boat itself. I reckon that rig did cost a plenty.
     
  10. IMP-ish
    Joined: Jan 2011
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    IMP-ish powerboater

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  11. Village_Idiot
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    Village_Idiot Senior Member

    Yes, the Majeks are great boats - would be difficult to find one that will run shallower for that size and weight. But they do run wet and hard in a chop. Shoalwater, Transcats, Flatscats and others will run just as shallow, but smoother in a chop. Problem with the cat-style boats is they can't get up on plane in as shallow water as the Majek RFL.

    I've not built any 'glass boats, just wood, so can't answer your question on the 'glass layup. Maybe another forum member can do that...

    I think the trick to the Majek, as well as many of the shallow-running TX flats boats, is to keep water in the tunnel. I think they do this by having a "pre-tunnel", that is, a wide, shallow tunnel in the hull in which the main tunnel is placed in. If you look at the hull bottoms on those boats, the hull is practically split, almost catamaran-style but much less obvious, so that the outer hulls are holding the water under the boat for the "pre-tunnel" to pick up and funnel into the main tunnel. Hope all of that makes sense!

    A simpler design may be a Hickman Sea Sled-style bottom (inverted-V) feeding a tunnel, as the inverted-V gradually tapers to 0 deadrise at the transom. Either way, make the tunnel at least six feet long, but probably no longer than half of the LWL, as that may introduce air from the bow. Keep water in the tunnel and you should be able to run the prop entirely above the bottom of the boat.

    Make sure you have a water pressure gauge - if you lose too much pressure you can do the nosecone pickup, but I find it easier to install Merc's water intake racing screens. The problem I've had with the screens is lack of water pressure in reverse, but it is something I can live with - otherwise, they provide max water psi at max jackplate elevation for me. An alternate solution may be to simply lay a bead of silicone just behind the water intakes to help funnel water into the intakes at high elevation - a large cav plate or compression plate would help here. Some guys will also plug the top one or two holes on each intake to reduce air ingestion.

    Also, be sure you have a good tunnel prop (double or triple cupping). A good prop will allow you to vent the tunnel and gain an extra 3-5mph on the top end. Go with PowerTech or Baumann props and you should be good to go.
     
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  12. keysdisease
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    keysdisease Senior Member

    Sounds like you don't like wood, but is would be lighter, cheaper, faster to build, and if built right last as long as a fiberglass boat.
     
  13. rasorinc
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    rasorinc Senior Member

  14. theboatbuilder
    Joined: Sep 2012
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    theboatbuilder Junior Member

    Thanks for all the input. Last night I saw a guy in Tx that built an XF20 and he had a 115 merc pro xs on the back of it. That is all I want, I dont really want a 250. What would I have to do to be able to put a 115 on the back of it and will this boat carry five people? I do not want to paint the boat, I would rather gelcoat the boat is this possible?
     

  15. Village_Idiot
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    Village_Idiot Senior Member

    I suggest you get on the boatbuilding forum at bateau2.com and ask those questions to Jacques, the designer of the boat. He will probably balk at putting higher HP on there, but if he realizes you are serious, he may work with you. Others who have built the boat will probably chime in also. The main thing would be to bolster the transom (probably double the thickness and add additional supports between the transom and gunwales/bottom). The boats, if you build them right, are very strong. There is a pic on the web somewhere of a large CC that collided with an XF20, and the CC is sitting on top of the XF20. The XF20 was supporting all of its weight and had little to no structural damage, IIRC.
     
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