Lowest speed planing

Discussion in 'Boat Design' started by yotphix, Nov 10, 2006.

  1. yotphix
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    yotphix Junior Member

    Watching the hull cleaners putting up and down Newport Bay has me wondering if there isn't a better way. Many use an 8' inflatable with a 5 or 6 hp outboard to carry themselves and two tanks around. At the harbour speed limit of 5 knots they adopt a bow up attitude and generate enough wake that the police often seem to hassle them to slow down.

    so... is there a small, light boat that could plane at say 6 or seven knots with the above load? Or is there some minimum speed at which it is possible to plane? From observation I know that mosst planing hulls don't get up on step before at least 10knots but my 240lb brother planes at lower speeds on a windsurfer so.. any chance?

    Or should these guys be using an outrigger canoe or rowing shell with an electric motor to sneek around the harbour at 6 or seven knots with virtually no wake?
     
  2. tom28571
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    tom28571 Senior Member

    A friend of mine uses an old Hobie catamaran for boating photography. Sits in a fixed chair in the middle and handles the small outboard with a long tiller extension. Almost no wake as he scoots among racing boats.

    That would be my choice and there are a lot of tired Hobies around.

    Most lubbers assume you are making a big wake if you go very fast, whether you are or not.
     
  3. yotphix
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    yotphix Junior Member

    Good call! Now that you mention it that's essentially what the rowing coaches are scootin around on. The hobies might well be the perfect light harbour workboat.
     
  4. timgoz
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    timgoz Senior Member

    My 14'4" v-hulled aluminum skiff got up on plane at a little over 7kts. Thats with a 9.9hp. A 6hp would have got her to plane, I feel, as my maximum with the 9.9hp was approx. 15.5kts.

    TGoz
     
  5. yotphix
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    yotphix Junior Member

    Do you happen to know the weight of the skiff? What was the load in it? That also begs the question would a shorter skiff plane at the same speed or lower? Thanks though, that confirms my suspicion that low speed planing is possible.
     
  6. timgoz
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    timgoz Senior Member

    I don't know the boats wieght. It was an all welded (as oppossed to the ever popular Lund riveted boats) model, Gregor comes to mind. It was slightly less robust than a comparable Lund.

    The boat was used to take me and a summers worth of gear (excluding all food but short term) to the north tip of Prince of Wales Island in SE Alaska. I started in Nakati & used a gravel road to by-pass Protection Head as I felt the seas there could prove troublesome.On the way up I had a heavy load, 215lbs. of me & all the camping and marine gear needed for the season. I think I had to get approx. 8kts. to plane with this load. To be honest, I was not in a hurry. The waters were new, area remote, and navigation tricky. I did not want to start the summer by loosing the boat, or worse.

    Once established at Port Protection Bay, and familiar with the daily route(s) reqiured to get to the areas two small settelments and other points of interest, I was able to open her up when the feeling arose.

    Most often I ran at 8-9kts. as just on plane consumes the least fuel.

    My speeds were derived from my hand-held GPS unit.

    Using the wieght of a 14' Lund my rough guess as to total load; boat, motor, fuel, gear, and myself is appro. 700lbs. About 100lbs. or more less once on site.

    TGoz
     
  7. saltflower
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    saltflower New Member

    canoe shape

    a friend of mine put a 1 1/2 hp outboard on a 16' canoe, some years ago, it could push the two of us(about 390 lbs.) along at about 9-10kts.. no wake, but harbor dept. still made us slow down::D
     
  8. gggGuest
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    gggGuest ...

    On canals in the OK I've seen a catamaran that's basically two rowing skiffs with a platform across the middle and a tiny outboard. Much more expensive to buy than the ducky, more prone to damage, but I bet cheap to run. There were some sailing catamarans built in the UK with inflatable hulls... that might be cool.
     
  9. Stephen Ditmore
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    Stephen Ditmore Senior Member

    A 15 footer should be able to go 5 knots without planing. A 21 footer, 6 knots.

    A multihull with a single hull length/beam ratio over 11 can attain a higher displacement speed (relative to its length) than those above, and will make less wake than a wider-hulled boat.

    I'm with the catamaran idea, but would favor one with symetrical hulls (the Hobie's are assymetrical).
     
  10. nordvindcrew
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    nordvindcrew Senior Member

    this brings me around to a question I asked in another forum. I do open water rowing races, and have recorded speeds of over 7 kts as we sprint at the start. A particular stretched dory seems to be trying to climb up on a plane, and I asked if this is either possible or desirable in terms of overall speed. The boat weighs about 160 pounds, two rowers @180 lbs. and oars @ 20 lbs. Bottom length about14' and maximum beam on the bottom of about 30". any thoughts or comments?
     
  11. percyff
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    percyff percyff

    Many years ago two up in a 12' inflatable (pre-RIB days) and a 20HP evinrude, we went up the River Hamble at about 6 knots (speed limit) with one over the bow and the other well forward. The engine was stiff and could be left central. We could steer by gently rolling the boat. With all the weight forward there was negligible wash. If we'd sat aft at the same (below planing) speed we'd have pulled a bloody great wave. We never dared to see how fast we could go, it was just to get to service boats up river, but to avoid being chased by the harbourmaster for speeding.
     
  12. moTthediesel
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    moTthediesel Junior Member

    I don't know if any of you subscribe to the great little publication "Messing About in Boats", but the most recent issue (Nov. 15) has a artical pertinent to this subject. It's a reprint of a story by the late Robb White about his Grumman Sport Boat.
    He claims (and who would doubt the venerable Mr. White?) that his Sport Boat would plane two adults with no wake using just a 3hp Evinrude kicker. He also says that the 16' X 54" 110# hull would plane off before ever reaching hull speed, and so would not go through the usual transition phase at all.
    This story, like all Robb White efforts, is a delightfull read, have a look if you can.
    moT
     
  13. JR-Shine
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    JR-Shine SHINE

    I would not worry about plane or not plane - what you need is long narrow boat.
     
  14. nordvindcrew
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    nordvindcrew Senior Member

    Not really worrying about planing, just general hull design. My Jersey Skiff has a VERY deep forefoot and cleaves the water, a Gloucester gull has no fore foot and tries to rises as it is rowed . I'm trying to get some input on the desireability of either general hull type as to effort required to move through the water at about 5KTS.
     

  15. jeemboNC
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    jeemboNC Junior Member

    long with no squat

    Planing is fastest with a long boat that is 'actively' loaded fore and aft (meaning you move as needed). My 3hp would plane better on my heavier, draggier 14 foot aluminum jonboat than my 8 footer. Watch a short, beamy rib or pure inflatable try to get up - it's painful unless there is gobs of power. 13' whalers with big 40s and aft loading do it with pure power, but there is major bow rise first. Somebody said it - long and narrow is best, but tippy and not a good workboat. So use two - ah, a catamaran!!
     
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