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527Re: Easily driven boats (and study plans ordered)

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  • Mike Dolph
    Jan 18, 2005
      Hi Lewis,

      I think you made some good choices in study plans. You will have
      some nice options and hopefully a lot of insight into the actual
      construction of the tunneldrive "ala Atkins". If if the plans are
      very instructive let us know; I'd gladly pay $10.00 to see how it's

      One caution: make sure your belt drive incorporates a thrust bearing
      to absorb the push of the propeller and impart it to the hull

      John Dolph

      --- In AtkinBoats@yahoogroups.com, "Lewis E. Gordon"
      <l_gordon_nica@y...> wrote:
      > Leo,
      > Wow, you certainly have stirred up some good responses on this
      > and the previous! I too am looking for a cruising boat to build; but
      > my cruising would be on a lake about 100 miles long by 40 miles wide
      > so the size requirements are different. However, the cost of diesel
      > fuel here in Nicaragua is high (not as high as Europe) and I am
      > looking for a very efficient hull in the 23-26 foot range. I would
      > like to use an agriculture air-cooled engine in the 6.6 to 13 HP
      > with belt drive. I can buy a 6.6 for $639 and an 11 HP was quoted at
      > about $1,300.
      > I really like the idea of a motorsailer for the assist it can give
      > well as dampening the motion in these sometimes (well lots of the
      > time) rough waters. Some of the local transportation pangas use a
      > to 15 HP outboard and a sail. So, today the check was put in the
      > for study plans of "Little Water", "Little Silver" and "Lady of the
      > Lake". Okay, I know a stern-wheeler is not efficient, but "Lady of
      > Lake" is for another project!
      > Mr. Robb White suggested "Little Water" but it is a fishing boat and
      > the cabin is minimal. Still, it looks attractive even though I don't
      > need the extreme shoal draft. (One inch draft per foot of deck
      > would be fine.) "Little Silver" is a V-bottom motor-sailor with a
      > cabin. I wish I could remember the design where the Atkins compared
      > the SeaBright Skiff based designs with V-bottom designs. For our
      > conditions, the V-bottom may be the way to go.
      > Oh, some more design considerations! Exterior plywood is almost
      > impossible to buy, and forget about marine grade! Good boatbuilding
      > woods are available but not cheap; and forget about asking for
      > quarter-sawn! There is a good wood here for steam bending (locals
      > it in water) but I haven't priced it yet. And I won't be building
      > alone. Our young carpenter working on things for the house is an
      > artist with wood and his rates are affordable!
      > I love this group!
      > Lewis
      > p.s. And I haven't entirely excluded Russell R. as a cheap option!
      > --- In AtkinBoats@yahoogroups.com, "Leo" <leochill@y...> wrote:
      > >
      > > Back when internal combustion engines were first becoming
      available –
      > > whether gas or diesel – these engines were massive chunks of cast
      > > iron and had very low HP to weight ratios. Maybe on the order of
      > > per 100 pounds. Today's engines might have 10-20 HP output per
      > > pounds of weight. Refer back to the comments about Rescue Minor
      > > how the bow acts without the motor weight that Atkin specified
      for an
      > > example.
      > >
      > > So back when Atkin was designing, motors were very underpowered
      > > the hull really needed to be "slippery" to fully take advantage
      > > the low power that was available in those days from IC engines.
      > > yes, I know I'm sorta downplaying, for now, the effect that
      > > has on turning a large propeller slowly.
      > >
      > > Based on my reading, early displacement power boat hulls evolved
      > > sailboat hulls that were "sorta" efficient. Obviously the
      science of
      > > designing efficient displacement power boat hulls progressed
      rapidly –
      > > as NA's learned what worked best and what was less desirable.
      > >
      > > It seems to me that as engines become both more powerful and the
      > > power to weight ratio improved, that the hull shapes started
      > > away from what slipped through the water easiest and began
      > > into the "fat-ish" hulls of trawlers and cargo boats and that
      > > evolution has progressed into the modern plastic floating
      > > that grace (or is that disgrace?) trade magazines and marina's
      > > world over.
      > >
      > > Having recently read a history of the Whitehall Rowing boat, I
      > > to wonder why this hull form, with its fine entry, generous mid-
      > > section and wineglass stern wasn't expanded upon for inboard
      > > What's the drawback from scaling this general design up to make
      it a
      > > 30-40 footer? Perhaps direct 1:1 scaling isn't practical, but
      > > couldn't one incorporate the fine entry, general midships section
      > > the fine stern sections into a power boat hull? To my very
      > > eye, it appears that Atkin did use some of these three design
      > > principles in several of his designs.
      > >
      > > IIRC, from Gerr's books and others, a large diameter,
      > > pitched slow turning propeller is more efficient for moving a
      > > displacement hull than a smaller less pitched propeller turning
      > > higher speeds. Or is my memory getting as gray as my hair?
      > >
      > > It seems to be a difficult task in today's world to find folks
      > > agree with this philosophy. Almost all modern (inboard diesel)
      > > propulsion systems rely on high speed engines – many with
      > > turbochargers – to turn a smaller wheel. Gear ratio's in the
      2:1 –
      > > 2.5:1 are common. This translates into prop RPM's from the low
      > > of 750 RPM to a high of 1800 RPM when the 2:1 geared engine is
      > > to 3600 RPM.
      > >
      > > Yet just a few decades ago we had engines that idled at 300-400
      > > (or less) and had an operating RPM range from 700 to 1200. These
      > > engines ran for literally tens of thousands of hours nearly
      > > free. Nowadays we often hear of inboard diesels needing
      > > in as little as 2000 operating hours. Throwaway power. Yuck!
      > >
      > > I believe that we can generally agree that 1) how/where you want
      > > go with a boat, 2) how long you want to stay aboard and 3) how
      > > much `camping' you're willing to tolerate determines what type,
      > > and amenities we'll need. And finally, 4) aesthetics. How a
      > > looks to our eye is vital. And as each of us has different needs
      > > tastes, I believe all 4 of these considerations are classic cases
      > > where Your Mileage May Vary. ;-)
      > >
      > > Addressing #1. My wife is a teacher and a decade younger – I
      want to
      > > be able to put the boat on a trailer and go for her summer
      > > to Alaska via the inside passage this summer, The Erie Canal
      next –
      > > Maine and Nova Scotia another – Trent-Severn waterway another.
      > > we're both retired then on to the Bahamas for the winter and back
      > > Alaska for an extended trip. Maybe put it aboard a freighter and
      > > ship it to France for a couple of years living on the European
      > > system.
      > >
      > > Addressing #2. At first we're only talking about 10-12 weeks at
      > > stretch. Later it could be full time for a few years – or at
      least 8-
      > > 9 months out of 12.
      > >
      > > Addressing #3. At first – we can tolerate a bit more `roughing
      > > for a few weeks, but some of the things that we will not do
      without –
      > > (not an all inclusive list) 1) space to get away from each other
      > > need to. 2) a great galley with room enough to prepare a full
      > > without contortions of the body or with the pots and pans. 3)
      > > length and width berth(s) with comfy mattresses. 4) a separate
      > > sized shower – no sopping TP! 5) an all weather pilot station –
      > > either fully enclosed or enclosable with canvas.
      > >
      > > Addressing #4. I just plain like boats that look like a classic
      > > boat. None of this plastic fantastic modern European shapes for
      > > Give me the lines of an Elco or a Lake Union Dream Boat or a
      > > ended Salmon Troller or the shape of a Whitehall. Give me a nice
      > > sheer and a plumb bow. How about bronze ports – either oval or
      > > round – and a rearward sloping windshield instead of that forward
      > > sloping monstrosity, regardless of how practical it is. Bottom
      > > line? Spare me the angular constructs that adorn so many
      > > and boat shows.
      > >
      > > Finally, I think we can all agree that petroleum products – oil,
      > > natural gas and diesel fuel – are just going to get more and more
      > > expensive. The days of a buck a gallon diesel are probably long
      > > gone. So this means that to have a boat that I can afford to
      > > operate, it must be very efficient. I'd consider 7-10 statute
      > > the minimum – this should equate to less than 1 gallon per hour
      > > running, in other words, 6-8 knots cruising speed at less than 1
      > > GPH. Better than that is just that, better. I think that this
      > > achievable in a 35'-ish boat if we don't load it down with a ton
      > > canned goods. Something less than 20,000 pounds – 15,0000 better
      > > yet - fully ready to cruise would be the goal. My preliminary
      > > investigations and calculations indicate that given the right
      > > design and using modern epoxy/ply building methods this appears
      to be
      > > an achievable goal.
      > >
      > > Finally, utilize a big ol' slow turning engine with either a VPP
      or a
      > > big-ish wheel and set it up to cruise at a V/L of about 1 to 1.15
      > > the most efficient fuel consumption RPM for the engine – probably
      > > less than 1500 RPM - and one should have a boat that one could
      > > to build and run without breaking the 401k and would be worthy of
      > > being called a Retirement Cruiser.
      > >
      > >
      > > Addressing Manfred's comments about River Belle – This would be a
      > > perfect boat for cruising the ICW and the various canals,
      > > and rivers. But would this design be suitable for an Alaska trip
      > > a trip to the Bahamas or a summer on the Great Lakes or the coast
      > > Maine and Nova Scotia and Newfoundland? Perhaps not. So I still
      > > think to go to all the various places that I'd like to visit
      before I
      > > die, I need a boat with some sort of keel and the ability to take
      > > some rough weather should the unfortunate happen.
      > >
      > > Any other suggestions?
      > >
      > > Best,
      > >
      > > Leo
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