Outboard Dory Project

Nordski. Why to waste time reinventing the wheel? Your SOR is fulfilled by dozens of cheap plans with details, scantlings, list of materials in lots of different materials, plywood being the most common. All you risk drawing your own plans is to draw a lemon. For example Bow tanks are NEVER a good idea. Gas tanks vary greatly in weight so it's far better to place them close to the center of gravity. If you want to put weight on the bow for trimming use a useful weight that never changes like a small anchor, a few meters of chain, good ropes, brief the mooring which is a security. Trimming a small dory is a breeze, as the outboard itself can be trimmed (I counsel you to make the expense of an outboard with electric trim) and you have plenty of living and trimming ballast, ie the passengers.
Better to spend your time building than trying to get distant design advises in a forum for such a simple boat...The savings on the plans will be ridiculously small, but the savings of time truly huge. If the boat does not stay on the water and is protected from the weather under roof when not used, it can be made cheaply and fastly in good quality exterior plywood, polyurethane glue, pine wood and a few screws, painted with an alkid. It will last years and years.
No need to think over it during months, build it. It's just a small boat which has been made by thousands.
Although I'm myself perfectly able to calculate, draw and design such a boat I've never bothered to do that on my own small boats. It's wasted time as it has been already done. I buy a plan I like from a good NA, using a building method as simple as possible, with minimal structure, using basic tools. Thousands of motor dories had been made since 90 years, so the design is mature.
I prefer to make it at my taste with the small improvements I love, as truly comfortable seats, "dryness" and ability to get rid in seconds of the water inside the boat, well fixed tanks and battery (not like in the last pic), a good anti skid (not like in the last pic), good lights for if you are coming back a bit too late, ice box, waterproof box for clothes and papers, supports for my fishing rods etc. All these small but so convenient details will take already a lot of time.

 

+1 re all of Ilan's comments above - just buy a set of plans for the boat which is closest to what you have in mind, and start to build it.
The plans might even give you the true shapes of the plywood panels, to save you having to offer up plywood to the frames, marking it off and then cutting it out (with consequent risk of error).

 

Thank you for the input. I’m in my 40th year of boatbuilding and for me nothing in the process is a waste of time, every discussion has some value or entertainment. I reached out to this group for a discussion on “design” and I do realize that any advise I receive from this forum has the exact value of what I paid. Jeff Spira has designs that are very similar to the one I’m proposing, in fact he drew a boat for me several years ago and I built the one featured on his web site.... “Avila”. Most outboard dories have floor framing or a raised deck, the only one I’ve seen without is "Long Point” so I know that it can be accomplished. Regarding bow tanks, they must be used often because tank manufactures sell them by the thousands. I’ve never had a boat with one so I’m not familiar but I do know that as the fuel is consumed the trim will change, it was just a thought but maybe not worth the effort.

 

Bow tanks are used on sailboats from my reading; to avoid slosh and to keep dynamic loads centered when heeling.

There is nothing spectacular about modifying a hull bottom to fully flat. You need the bottom to be thicker which can also be done with a sole and thin stringers.

You would be amazed at the stiffness of plascore 1" with 44 ounces of glass on each side.

And the horsepower needs here are pretty low.

I have not built one, but I believe many drift boats are built this way.

Here is a plascore panel layup. The only negative is you must realize this is a thirsty layup using plascore. A marine foam layup with vac would end up lighter.

This is a catamaran bottom; designed to pound if needed; hoping not.

plascore will bend in one direction, but not two for laying up rocker

plascore also comes 5'x10'; so good sizes which was what I really liked

Not sure about the sides as I was unable to open your pdfs? My Phone acting up maybe?

But you need some stiff sides; perhaps ?4" frames on a gutcheck

Plascore is cheap, too.

Do remember my warning. Their hand laminating product is thirsty to do right. I tested it here and we prewetted their veil and then laid wetted fabric on. I am sure we are at 55-60% resin..but it isn't coming apart

 

I have suppressed a lot of bow tanks, a true nuisance. You do not place a variable weight in a place with maximal polar inertia, ie far from the center of gravity. The worst bow tank was one on a diving boat made in Florida USA with a diesel engine which in choppy sea sucked air so the engine stopped and the fuel line had to be purged, very funny with 20 divers getting sea sick with the nice smells of diesel.
This boat was a miracle of bad design. When the bow tank was full, the boat was a heavy nose submarine, when empty the bow was pointing to the sun, and I loved the vibrating Cummins directly bolted to a steel frame glued to the GRP hull with chopped mat and resin. The vibrations were able to make jump out the dental fillings and contact lenses.
After hard work for correcting these flaws, plus the electric circuit and reinforcing the flimsy cigarette style hull that became a pretty nice diving boat.

 

Nordski, I totally support your build/project.
Years of experience are colliding with years of experience.
You couldn't pay me to install a bow tank.
For me it's a horrible idea I couldn't live with.
Constantly moving stuff around (including people, which isn't so bad)
to compensate for varying loads and trim.
Then there are all the other problems associated with it.
I once drove a new, Zodiac style rescue boat with a bow tank.
In rough water/weather, it would vent gasoline and it would spray in your face!

Have all your builds been self designed or have you built any to plan?
Pictures?

 

Thank you for the info on plascore, might be a good application for what I'm working on.

 

Thank you. I appreciate the feedback on the bow tank, I now plan to install the tank under the splash well. Unfortunately I lost everything some years back and have only photos of some recent builds. My first project as a teen was "Paper Tiger" I lived in Everett at the time and David Roberts sold me some material and gave me good advise. I've build mostly small craft (canoe, kayak, skiffs) Some of my own design and some from purchased plans. I saw one of my boats at the local harbor the other day still going strong although modified a bit and not well maintained (O'Brien "Voyager"). See attached Tolman Jumbo and Spira "Avila"

 

Redmond "Bluegill"