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Thread: Hydroplane

  1. #1
    Join Date
    Mar 2016
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    South Africa
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    Default Hydroplane

    I started this Super Spartan hydroplane in 2011 as a fun build. My hart was never really in the project ( I am a sailing person) and the job came to a halt in 2012.
    I have now dusted it off and over the last few days the decking has been completed. The only structural job left to do is to fit the transom/ outboard knees.
    I am planning to remove the present steering wheel bulkhead and replacing it with a full bulkhead instead. That will give the boat a good bouyancy chamber up front and also prevent the boat from getting bow-heavy in case of a slight mishap or swamping.

    My intention is to borrow the 15 hp Yamaha motor from my wife's little utility runaboat as a power source. The 15 hp motor pushes the utility boat at about 17.5 knots. The utility weighs at least 3 times more than the hydroplane so the speed should be okay for having a bit of fun.

    s spartan 2.jpg
    Last edited by Frans Loots; 03-14-2018 at 03:45 PM.

  2. #2
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    Mar 2016
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    South Africa
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    Default Re: Hydroplane

    The boat is built from plans by Glen L Boats.
    Not the greatest of quality and clarity plans. They squash everything randomly onto one piece of paper. The instructions are also just printed on one A4 size paper with fine print instructions reminding me of a bank contract.

    Compared to my other builds from Chesapeake Light Craft plans and those of Ian Farrier from who's work I built a 9 meter composite trimaran, the Glen L stuff is pretty poor and confusing.

    s spartan 1.jpg

    A big sanding session is comming up next.

  3. #3
    Join Date
    Oct 2009
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    South Puget Sound/summer Eastern carib./winter
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    Default Re: Hydroplane

    I never built owned or even drove a hydro.
    Looks like fun!

  4. #4
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    Jul 2017
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    Toodyay, Western Australia
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    626

    Default Re: Hydroplane

    Looks like something out of Star Wars.

  5. #5
    Join Date
    Jul 2000
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    N.E. Connecticut.
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    Default Re: Hydroplane

    It looks like a nice little build project. Over here they are quite popular as a sanctioned raceboat class, do some googling around A.P.B.A. (American Power Boat Association).

  6. #6
    Join Date
    Dec 1999
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    Oriental, NC USA
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    4,686

    Default Re: Hydroplane

    Depending on which 15hp it is, I'd say that 30 is not an unreasonable expectation. I have a 1953 Mercury Mark 20 that would make it fly.

    A Farrier 31 is quite a project. Did you use the balsa core strip construction?
    Tom L

  7. #7
    Join Date
    May 2004
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    Cuyahoga Falls, Ohio
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    Default Re: Hydroplane

    Does the 15hp engine need a different prop to not over rev or get the best speed out of her? Other hot rod boat people would be the the ones to answer that question.
    Sounds like the sort of fun mothers and wives dislike.

  8. #8
    Join Date
    Mar 2016
    Location
    South Africa
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    82

    Default Re: Hydroplane

    Hallo Tom,
    Regarding the Farrier F9ax. I used high density PVC foam as the core material. The panels were laid vertically in the form frames.
    If you google, Frans Loots, F9AX, latest news, you will see quite a bit about my old boat and its adventures. The hydroplane is being hatched in the same garage which hatched the trimaran.

    The engine for the hydroplane is a 2 stroke Yamaha 15 hp. Here where I am, there is pretty onerous government legislation regulating powerboats and their drivers. The legislation is applicable for any boat with an engine greater than 15 hp. Hence the reason for only fitting a 15 hp engine onto this boat. It keeps everything below the government radar.

    About the prop, it is all new territory for me. Time will tell what works best. It's gonna be bad enough stealing Mom's engine. Changing the prop while I am at it might just flip Mom's personal hydroplane so to speak.

    Regards.
    Last edited by Frans Loots; 03-14-2018 at 03:52 PM.

  9. #9
    Join Date
    Jul 2017
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    Toodyay, Western Australia
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    626

    Default Re: Hydroplane

    You don't really need the entire 15hp engine, just the cover with the stickers which say 15hp. That cover can then replace the cover of the 30hp

  10. #10
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    Mar 2016
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    South Africa
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    Default Re: Hydroplane

    Quote Originally Posted by Small boats rock View Post
    You don't really need the entire 15hp engine, just the cover with the stickers which say 15hp. That cover can then replace the cover of the 30hp
    I have so much to learn!

  11. #11
    Join Date
    May 2000
    Location
    St. Louis, MO
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    10,713

    Default Re: Hydroplane

    My dad and I built one about 1980. Fun little boat when I was younger. Actually just sold it about five years ago to another family, so that they could enjoy. Pretty sure it was a 20 horse hanging off the back of mine ... and it FLEW!!
    Nothing else matters but how I raise my children ... and their opinion of me, as a father.

  12. #12
    Join Date
    May 2004
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    Cuyahoga Falls, Ohio
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    Default Re: Hydroplane

    In wasted youth road racing a 250 cc Yamaha TD1C motorcycle there's quite a bit of stuff you can do to a 2 stroke engine to make more HP than the manufacturer intended. Merely machining everything to perfect specs and polishing the ports is a good start as is replacing the piston rings early and often, something like every 10 hours of flat out top rpm running.
    Surely there more than a few engine guys in the Land Down Under - home of the fearless.
    BTW, the difference between a 15 hp engine and a 20 hp of the same make is often some sort of limiter that is not too difficult to remove. Small Triumph bike engines had a sort of washer between the carb and the intake you could easily remove. YRMV.
    Last edited by Tom Robb; 03-16-2018 at 04:36 PM.

  13. #13
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    Jul 2017
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    Toodyay, Western Australia
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    Default Re: Hydroplane

    Well if we're talking of youth and motorcycles I must mention what a mate did (way way back)... he had yammy 250 xs (250 was the max allowed for the first year of a rider's licence, after that you apply for a big bike license) but it turned out the 400 xs was identical except for the bore. As luck would have it he found a 400 being wrecked and bought the whole engine, then he put the block and pistons along with new rings on the 250. The only way to tell that his 250 was not a 250 was to pull it apart. Pretty cool huh!

    So with this in mind I wasn't completely joking about the 15hp cover... maybe there is a way? Then the hydroplane will fang it past all those whimpy 15hp hydroplanes.

  14. #14
    Join Date
    Dec 1999
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    Default Re: Hydroplane

    One way to see if your outboard can be quickly powered up is to see if others from the same manufacturer with the same displacement are rated more powerful. Sometimes that is done with a restrictor plate behind the carburetor and you can just remove or enlarge the diameter. Others more expert might be asked about this.
    Tom L

  15. #15
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    Mar 2016
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    South Africa
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    Default Re: Hydroplane

    Quote Originally Posted by Tom Lathrop View Post
    One way to see if your outboard can be quickly powered up is to see if others from the same manufacturer with the same displacement are rated more powerful. Sometimes that is done with a restrictor plate behind the carburetor and you can just remove or enlarge the diameter. Others more expert might be asked about this.
    All the above advice for hotting up the 15hp engine is fine, except I'm a yachty by background and now North of sixty. I was quite okay cranking it up offshore on my last big boat, an Ian Farrier trimaran, but a hydroplane with a suped-up engine and my bubble within inches of the water.............dunno about that?

  16. #16
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    Mar 2016
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    South Africa
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    Default Re: Hydroplane

    hp5.jpg

    I have now cut out the original steering wheel bulkhead and replaced it with a full bulkhead. The bows will now be a bouyancy chamber. I will glue the steering cowl deck down once I have fitted the steering wheel.
    I spent the best part of the afternoon sanding the bottom. Tomorow it's the deck and cockpit.
    The plans call for drum and cable steering.
    A new steering unit will cost me as much as the boat has cost me to date. Here where I live there are no boat junk yards where I could go and look for a secondhand set either. A google search has shown afew good looking DIY drum steering units so I will give it a go and make my own.

  17. #17
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    May 2004
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    Cuyahoga Falls, Ohio
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    Default Re: Hydroplane

    To each his own.
    The proper propeller item still holds. If you want the engine to be happy the prop needs to match the boat which I'm told is true for any boat, not just hot rods.
    We'll all like to see pix of you blasting about in the Hydro, rooster tails and all. Video even better!
    Sounds like great fun.

  18. #18
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    Jul 2000
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    N.E. Connecticut.
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    Default Re: Hydroplane

    There is nothing wrong with cable steering (drum steering) as long as you understand and maintain it.

    One of the big things is NO screws, through bolt everything. If screws are used, and one the the pulleys pulls out of the wood, all tension is lost on the cable. The only thing that can happen then is for the outboard to rapidly ‘flop’ all the way to one side, toss you out of the boat and proceed to spin in circles. (You can fill in the result of that.)

    I grew up with cable steering, never had a problem, and wouldn’t hesitate to use it.

  19. #19
    Join Date
    Dec 2011
    Location
    Onancock, VA
    Posts
    963

    Default Re: Hydroplane

    My father and I built the exact same hydroplane in 1970. It had a different name but is exactly like yours. I never used it because my father wasn't really interested in buying a motor to put on it. I went away to boarding school and college and eventually sold it in the mid 80's but it never touched the water. It's a cool little boat. You should have fun with it. Being that close to the water you will feel like you are going 70 MPH.

  20. #20
    Join Date
    May 2015
    Location
    Port Elizabeth, South Africa
    Posts
    238

    Default Re: Hydroplane

    Frans, Justin Dent gets 25kts with a 15hp on his Orca 340 so I am sure your speed will be limited only by prop pitch, rpm redline and how brave you feel on the day.

    What does your hull weigh?

  21. #21
    Join Date
    Dec 1999
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    Oriental, NC USA
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    4,686

    Default Re: Hydroplane

    I have a steering drum and shaft left over from a runabout a few years ago but South Africa is a long way away. Have used cable steering off and on since 1953 with on serious issues. In addition to the "no screws" advice, make sure that the cable cannot slip past the sheaves inside the straps. This can be detected ahead of time and taken care of then. Not as bad as having the cable come loose but not good. Don't know if it has been mentioned but don't forget a crash throttle to put the engine in idle if your hand slips off. Glen L carries lots of cable steering parts but they are far off as well.
    Tom L

  22. #22
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    Jul 2017
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    Toodyay, Western Australia
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    Default Re: Hydroplane

    If you were really super creative maybe there is some way to adapt rack and pinion from a small car (if there are any wreckers around your area). I haven't thought this through, just lateral brain storming for alternative approaches.

  23. #23
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    Oct 2009
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    Default Re: Hydroplane

    Those Teleflex systems are not super cheap anyhow. It seems I have bought half a dozen replacement cables over 20 years @ a hundred or so a pop. They get tight.
    Drum steering would be in keeping with the vintage.

  24. #24
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    Jul 2017
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    Toodyay, Western Australia
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    Default Re: Hydroplane

    Drum steering... one person on the tiller, the pilot beating on the drum, one beat port, two beats starboard, three beats tiller amidships.

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