Re: [AtkinBoats] Re: Tolman's adaptation
- Hi Ken & Group, I should have been more clear (my bad). Here's hoping I get it right this time. The change involves the bottom of the box keel only. Any change to the stern would be to raise bottom of transom center a maximum of half in. but not top of tunnel over prop changing the angle of descent, any cavitation would happen at slowest speeds.
The increase in draft isn't really that important. The Potomac's channel is on average 25' plus deep & wide, the in-town Naval base on the Anacostia River is 10-15 blocks (maybe less than that) from Capital building and for city's security it must be able to handle war ships 2oo ft plus. The shallow parts are full of quickly shifting sand bars some Rescue Minor would have trouble clearing.
My real interest is River Belle as in-town on the Potomac live aboard retirement & economical large distance cruising. My interest Rescue Minor was sparked by Robb Whites article in WB mag.#189 and thoughts of Rescue Minor as day tripper with friends.
--- On Mon, 4/7/08, Kenneth Grome <bagacayboatworks@...> wrote:
> From: Kenneth Grome <bagacayboatworks@...>
> Subject: Re: [AtkinBoats] Re: Tolman's adaptation
> To: AtkinBoats@yahoogroups.com
> Date: Monday, April 7, 2008, 11:32 AM
> > My idea would be to incorporate & blend a
> > V into the forward half only, leaving last half
> > flat for a softer ride in the rougher water of
> > the Potomac & Cheasapeake.
> I would like to understand what you're suggesting here,
> and I'm not sure
> I 'get it' just yet ...
> Do you mean to design the front half of the boat more or
> less like the
> Tolman Seabright skiff is designed now -- but instead of
> twisting the
> garboard panels so that they become an inverted vee in the
> aft tunnel
> section behind the end of the box keel, these garboard
> panels would
> instead twist only enough so that they will end up
> horizontal in the
> athwartship direction -- possibly while retaining the
> downward 'hook'
> of the bottom at the transom?
> If this is what you mean, the aft chines will remain above
> the water
> when the boat is at rest, offering no lateral stability
> over what the
> pirogue-shaped box keel and the center / front portion of
> the hull
> provides -- which is not much relatively speaking. The
> simple solution
> here is to reduce the height of the box keel, or better yet
> narrow it
> so it loses some of its buoyancy and allows the chines to
> be submerged,
> at least a little. Narrowing the box keel is the preferred
> solution of
> course because it will provide greater fuel efficiency and
> not require
> a smaller diameter propeller.
> I've experimented (on the computer) with this concept
> before, and this
> design is likely to work well if the hook in the aft bottom
> is not too
> extreme, and if the goal of shallow draft is relaxed enough
> to accept a
> hull that drafts 14-15 inches rather than 6-7 inches. But
> my design
> goal has always been to retain the very shallow draft, so
> I've not
> developed this concept further. But outboards require this
> much draft,
> so maybe this concept is worth a second look.
> With a protected propeller and rudder, a boat that drafts
> 15 inches
> might still be a desirable boat, especially if it can be as
> driven (fuel efficient) as some of these tunnel-stern
> Seabright boats
> seem to be. There is every possibility that such a boat
> might be even
> more fuel efficient than the Atkin designs, since they
> would use a
> narrower box keel and not have to pump water up into a
> tunnel pocket.
> I don't think speeds in excess of 20 or 25 knots are
> going to be
> practical and fuel efficient at the same time in a boat
> like this, but
> these speeds may be possible -- and when it comes to
> "running for
> cover" speed seems to take precedence over fuel
> Ken Grome
> Bagacay Boatworks
> No flaming, cursing, politics, religion or public mopery.
> Please be polite.
> If you set out to build an Atkin boat, please do not modify
> the plans. If you stray from the plans you do so at your own
> risk and Atkin & Co. will take no responsibility for the
> performance of the resulting boat.
> The current Atkin boat plans catalog is online at
> Yahoo! Groups Links
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