Sharpie River Cruiser

If you use a 40" bottom and DWl is 288", you'll have a 7 to one boat. The part that is in the water is what counts when you are doing aspect ratio calcs. Forty inches is enough chine beam if you have a disciplined and sober crew and all weights are kept as low as practical. Why not use the whole width of the ply sheet and let the chine beam be 48"? The additional eight inches will translate into more than half again better static stability. Not only that but the boat will draw less water.

Boatbuilder41 has the right idea. The outboard lets you have a reverse which is an important ability on a 24 footer. It eliminates the need for a rudder. Lots of good reasons for opting for the outboard rather than the B&S or other stationary motor. The Outboard eliminates a whole lot of problems, one of which is dealing with an exhaust system which will cost a plenty because it needs to be made of stainless with a water cooling jacket. Kohlers, Briggs, and other motors of that sort vibrate a lot more than a decent outboard and they are much, much, noisier. Think of the possibility or accidentally running over some guys trot line, pot warp, or other flotsam. With the inboard you will need to get out the scuba gear to clear the prop. With the outboard, you tilt it up, clear the mess and be on your way.

 

Outboard is the way to go, absolutely no question about that.

 

I'd like to pile on here and say the more I learn about boats the more I like outboards.

 

four stroke outboards

 

When designing narrow craft, you have to be very careful and quite hydro capable, plus engineering such structures require considerable thought as well, because you haven't the "beam" (web) depth to make her stiff, across her length. The 6:1 ratio offers a lot, but it also steals a lot, so be careful what you wish for. I have some small amount of experience, with just this type of cruiser and making her stiff on a shallow, narrow hull form, is quite difficult.

 

It's more than a bit narrow. The OP's boat has scaled a Tennessee down at a ratio of 1.25 in length and 1.5 in beam. Stability scales by the 4th power of scale ratio. So his stability is reduced by a factor of somewhere between 2.44 and 5.6. these are killer numbers. If he had done a straight LOA scale with a beam of 4' 10", the stability reduction would still be a by a factor of 2.44. This why short boats tend to get beamy.

Such a simple fact is often overlooked by many who just want to change the size of a boat they like by X amount. The real result is even worse than the numbers show because the stuff that is inside such as people do not change.

 

A low Cp will reduce stability even more.
Rather than reinvent the wheel find a plan that serves your needs and go with it.

 

Src

I suppose Sneakeasy would better suit my needs at 26' loa x 4' beam?
http://www.boats.backwater.org/Sneakeasy/

 

Even Bolger warned against overpowering Sneakeasy or expecting that it was suitable for more than very protected water. You can't escape the physics of the situation although you may be intent on trying.

 

Src

Just the opposite, I have no interest in speed. I want a low powered, low speed river cruiser with a very efficient hull. I like this arrangement for the engine. It is extremely simple, the prop is accessible for clearing debris and is fully protected.

 

Flathead, I have several "river cruiser" designs that solve the stability and other hydrodynamic issues you'll encounter. Of course, none of them are a 6:1 beam/length ratio, as simply put, you need some serious length to find any accommodations with this ratio. This is why there are no small sharpies, unless they've been altered to be a skiff. Bolger also warned (in regard to his narrow cruiser designs) that they were very weight sensitive and couldn't tolerate tall deck structure additions.

What is your idea of a low powered, efficient hull?



This is one of my riverboat designs and it hits all your requirements easily, with sufficient stability and internal volume to offer reasonable accommodations. Of course it's outboard powered, which saves a lot of internal space and decreases draft, plus greatly improves maneuverability, but you could use an inboard if desired. That 8 HP Honda would be hard pressed to do much with a contrary current and headwind, but it could putter her along on a dead flat lake. She'd really prefer more like 20 HP. Steering with an underpowered straight shaft like that will test your skippering skills too.

There are lots of designs like this available from most designers and plan houses.

 

That's a very nice boat but just too elaborate for my intentions. I am looking to build a minimalist craft with a small cabin to sleep in. I do have a 440cc engine based on the Honda GX390 that makes in excess of 20hp and weighs less than 70 lbs. Tennessee fits all my criteria except for it's size. I am willing to compromise and say that a range of 20'-24' will work. I do want a displacement or semi displacement hull with adequate rocker to keep the keel and prop tucked up out of the way. I am however wanting a boat with all the attributes of Bolger's state series designs with their plumb stems and slab sided elements. I just like the look of them. An outboard is off the table.
To keep proportions correct if Tennessee is 29' x 6' then a 24' version should have a 4.96' beam so I see that I was naive in contemplating a 4' beam. As was explained though ,scaling up or down is not advisable.

 

Src

I did some searching and found this thread. I should be able to design a hull to suit my needs as opposed to endlessly searching for a boat plan that doesn't exist. If I refine my loa to 20' it is conceivable to make my max width at the chine 4'. Allowing for some flare at the sides, my beam at the shear could be 4'-6" to 5'. Provided I could keep the stem plumb I think this would be fine and the bottom would have a calculated rocker that would perform properly as described in the thread. I have ordered Reuel Parker's "The Sharpie Book" and one of Harold Dynamite Payson's as well. Between the two I will gain the knowledge to design and build my own boat and not have to rely on plans as I never have in the past.
http://www.boatdesign.net/forums/boat-design/sharpie-skiff-chapelles-rules-29844.html

 

The 'Riverboat' concept has been developed comprehensively 'down under' , including an electric version, and an outboard version

http://www.duckflatwoodenboats.com/mainpages/gallery.php?KID=72

 

I think the OP is looking for the pop up tent version.

With a gas bike engine the engine and shaft mounted on the stern as used all over the Orient would seem the logical power installation.