Mini - something.......

Discussion in 'Boatbuilding' started by Firemanjim, Jun 20, 2016.

  1. Firemanjim
    Joined: Jun 2016
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    Location: Houston

    Firemanjim Junior Member

    Afternoon gentlemen. First post. First attempt to build a boat. Please bare with me.....
    I decided to try building a mini speed boat with my kids. I looked at pics and kits, and the like. I have settled on a design similar to a Minimost. It is of my own idea, and I know nothing about boats for xcept.... Water outside the boat is good.... Water inside the boat..... Bad.......
    My plan is a small wooden speed boat, built of 1/8th inch ply and wooden frame strips, covered in a multi directional fiberglass cloth for strength. I'm looking for it to be light as possible so my kids can man-handle it in and out of water. I'm going to use a small block Honda gx160 that puts out about 12hp @ 6200 rpm.... (stock is 5.5 HP @3600 rpm. I build these engines myself. )Yes, it's a go kart motor. Horizontal shaft....... I'm not looking to break speed records, just letting the kids feel like they are...... However, if this works good, I will build a slightly larger one for me , with twin 8 HP blocks putting out 16+ HP each , driving one shaft and prop.
    Not new to building or designing stuff, as I'm a 30+ year go kart nut. Currently building a 1932 Ford bodied adult go kart powered by a 26+hp 200cc 5 speed dirt bike engine. It's geared for over 100 mph..... Old Bendix brand automotive drum brake.... It will be cool when done.
    Converted a kick start bike engine to a "pull start from drivers seat " engine.... I love to Tinker and build....
    Gonna grab a camera and post a pic of the oilboard boat I made last night, to give you an idea of what I'm doing, and to get feed back early in the design. That way I can make corrections before I waste any money. I have marked green stripes on the bottom of the hull as to where the chines, and rails will be.
    Am I on the right track? Any and all help is appreciated.....
    Thank you, firemanjim.....
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    I have no doubt you can build a little pocket rocket for your kids, but there's a good bit of stuff you'll need to know (hydrodynamics, engineering, etc.) before you should feel good, about having your kids putter out in a self designed boat.

    The inboard idea you have has been done, though not as simple as it might seem at first blush. The engine has to remain completely open to the air, or it will experience a gas fume explosion. This is why we have marine versions of engines. All the usual leak points (throttle shaft holes, bowel and tank vents, starters, etc.) are sealed or have spark arrestors installed to prevent these nasty occurrences (which use to be very common place).

    Compared to an outboard, an inboard needs a longer boat, mostly because in small sizes, you need to sit on or around the engine, which is uncomfortable, so you mount it forward or aft of the driver, requiring more boat length, compaired to an outboard. Also, steering in an inboard requires a rudder or a jet. A jet steers much like an outboard, but a rudder is a whole different animal and truly sucks in comparison to an outboard or jet.

    Then there's the actual boat shapes thing, which can be equally as daunting. I'm sure you could design a boat looking thing (put the pointy end toward the front), but will it be too heavy for the strength and stiffness you need, will in handle properly or just be a twitchy beast that scares the crap out of your kids, will it turn predictably or tend to flip over, etc.

    I'd recommend you get a set of plans:

    [​IMG]

    This is the 11' DynoJet by Glen-L and though intended for a jet, which is a good choice, as there's plenty of bashed up jetskis available, you could figure out how to get a straight shaft and your Honda in it.

    [​IMG]
    [​IMG]

    Above is the 12' Tiny Might, from the same plans house. It's designed for a straight shaft setup, in front of the driver. You can see the rudder and shaft angle, but the engine would need to be marinized, if enclosed as both of these examples are. Both of these designs also could be converted to an outboard, which would be much easier and steering would be greatly improved over a rudder setup.

    Below is the XP-8 and an 8' boat. The outboard is dinky, but because the boat is so small and light, it'll scoot pretty good, without having to sacrifice 3' of interior volume for the drive train. If you're really industrious, get an old 15 HP outboard leg and mount your Honda engine on top. You'd get the benefit of outboard power and steering, plus the room they save in the boat and you can tinker with a hot rodded vertical shaft Honda engine.

    If you really want to scoot:

    [​IMG]

    Again, consider some plans and build something that will (guaranteed) to scare the crap out of your kids (and you, if you have the balls to climb in it). These can be had in various sizes and are a lot of fun. I raced these as a kid, back in the days when blowing up was just part of the game.
     
  3. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    I will second Par's suggestion. Buy a good set of plans and build to them.

    You may be one of the few who has posted here that could actually tackle a full marinization of a gass engine, but it isn't simple or cheap. Do it wrong and there is a serious risk of the boat exploding. If you decide to go down this route then be very sure to research how to do it correctly.
     
  4. Firemanjim
    Joined: Jun 2016
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    Firemanjim Junior Member

    Not thinking my idea/design is bad, I'm gonna go ahead and do a boat from plans instead. Although I did not think about gas fumes and explosions, I did plan for an open engine area due to my engines running on the rich side. I planned on only a large top splash plate and maybe some for the sides, at a 45...
    Now then, I'm looking at the plans for the El Cid from svensons. The build list calls for spruce or cedar for the framing. Plans say to use it for it's strength and resistance to water rot and bugs. And that you should put three layers of paint or varnish. Well, I want to put at least one layer of glass and resin..... Do I still need to use spruce or can I just use pine? Apparently, I would have to order spruce or cedar, cuz I can't seem to find what I need here in Houston.....
     
  5. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    You can get cedar at Home Depot or Lowes, you just have to pick thru the stack of lumber to get something good. You will have to cut out the knots, so there will be lots of waste.
    But, it will be a lot cheaper even so, than ordering lumber you won't know how good it is.
    Another place is a fencing company or a decking company.

    At Home Depot, I usually get 1 or 2 boards per trip, so it takes some dedication.
     
  6. Firemanjim
    Joined: Jun 2016
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    Firemanjim Junior Member

    I refuse to go to Lowe's..... Didn't think about a fencing company..... I need to look around so more tomorrow, for wood shops. They would have good quality stock, would hope anyway.....

    I'll look at homedepot tomorrow, just to see what I can find. I'll need a few boards planed
     
  7. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Here in Ft. Worth, the regular lumber yards have nothing better than Home depot or Lowes.
    My favorite had 6 2x4's last time I asked and they were all full of knots.

    At least at the Big Box I can look thru a rick of 100+ 2x4's and every 2-3 days there is a new supply.

    Good luck.

    If you get something like 4x4's, rough cut, they will not be dry. You will need to either let them dry for months, or cut them down (a little oversized) and let them dry for a week +.

    I've been trying to find good Cedar for about 4 years.
    Don't cut your nose off to spite.......
     
  8. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    There is more than one good lumber yard in Houston, I would be pretty amazed if one of them didn't stock cedar and marine ply, which are really the only two things that you would need.
     
  9. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Being amazed is one thing, knowing it is another.
    Stocking Cedar doesn't mean it would be clear.
    DFW is pretty big and I go to Austin to get marine ply.

    I was offered the opportunity to buy a semi-trailer load of Cedar. It was to be clear - but "Of course there will be knots".
     
  10. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Fireman,

    I don't know what size finished pieces you need.
    When I do kayak strips (1/4") I just cut them on the tablesaw.
    I never use the planer any more. But my stuff is pretty small.
     
  11. Firemanjim
    Joined: Jun 2016
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    Firemanjim Junior Member

    I haven't done my introduction yet, so you guys don't know that I'm a cnc machinist and shop supervisor, , in the oilfield..... So, with that being said, not having much, if any, money for a summer boat project with my kids. I think I was trying for too much, on a first boat build. Kart motor propulsion, shaft logs, strut....... Probably a bit much for now........
    And thank you to you all, who responded in this post.... Your help , knowledge, and kindness was appreciated. A mini speed boat just isn't a doable idea at the moment. Don't think I gave up on building a boat though.... Far from it..... Been searching for "IT"..... and I found it.... The perfect boat to build WITH my kids, for my kids..... (and me :)
    I have found what must be the perfect, OSS boat build, for a beginner boat builder! And FREE complete plans!! By myself, I could build this to completion in a single 8-10 hour day. With my kids, stretch it over the course of this week, then maiden float , this upcoming Friday... ! No problem with the bread to build it because it only cost me $45.51 in wood, glue, and some "purty" brass screws..... All I need to buy now is some resin, because I prefer the natural wood look more than a painted wood. Resin I can probably get donated to me by my boss or neighbor, both of whom would have some just laying around. If not, I can buy it, it's not much..... Im SO EXCITED! I was up till after 6am this morning, building an "outboard motor " out of a couple different weed eaters..... It's a ryobi 25cc , cut down to a 2' OAL shaft length, with a Echo head piece. Mounted to this little boat, it should be perfect.
    Here is a link to the boat we are going to build. http://web.archive.org/web/20070402225118/http://www3.sympatico.ca/herbert.mcleod/skiff.htm

    It has 2 links, one for the plans, and one for instructions. I'm downloaded another guys drawings though, cuz they were cleaner. That link is on the same page as well... Maybe by posting the link, and someone seeing us build one, will give another prospect the courage to try......
    I'll post a pic of our "outboard motor " later....
    First day of build, starts tomorrow..... So check back frequently, as I'll be adding pics as we go, from start to o finish.....
     
  12. Firemanjim
    Joined: Jun 2016
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    Firemanjim Junior Member

    :idea:
    Work week was rough and it rained every day AFTER I got off.... :mad:
    Working on the boat today. The designer said he could build one in 8 hours or less. Hmmmmmph.... I got about 5 hours into this build and probably another 4-5 to go.... I'm taking random pics as I go, and will post everything as soon as its complete. Already got a silver dollar size blister on my palm from putting in the little brass screws. .. Not sure how, cuz my hand is pretty thick with calluses..... :confused:
     
  13. Firemanjim
    Joined: Jun 2016
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    Firemanjim Junior Member

    I guess you can only load 2 pics at a time ?
     

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  14. Firemanjim
    Joined: Jun 2016
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    Location: Houston

    Firemanjim Junior Member

    Here's a couple more. ..I'll post more tomorrow. .....
     

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  15. Firemanjim
    Joined: Jun 2016
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    Location: Houston

    Firemanjim Junior Member

    Not done yet but pretty close. One of my daughters is going to her birth father's for the summer , and I was trying to get this done before she left today.... Got in a hurry and started doing sloppy work. I tried though.... She is cool with it. She gave me a extra big hug and told me it was ok, and that she loved me and can't wait to get back home so we can get the boat wet.....
    2 of my little ones are being a bit impatient though it seems..... They are all excited!!
    And so now you see, it wasn't just about building a boat, but building memories with my kids. It's about the quality time spent with family..... After working 12's at work and 12's at the station for so long, I missed a lot.... Now I'm getting it all back......
    I'll post more pics as we get to completion. I've made a couple changes to the boat, from the plans, but only aesthetically. ...... Have a good weekend. .....
     

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