can a boat be a canoe, kayak and sliding seat rower?

And do all those without much compromise?

I don't see why not but I've not seen that exactly. I guess to be a decent kayak and canoe it would be bit light on canoe cargo carrying and be a rather slender canoe, as well as being a bit of a big wide open deck kayak, maybe covered decks at extreme bow and stern with provision to add fabric decks to extend coverage. To bridge canoe/kayak paddling you might need a removable center seat for somewhat elevated kayak paddling but that is more comfortable than fully seated "L" position.

I'm thinking about 17ft by 33"

 

Could you have a decked over canoe shaped hull with a sliding seat rig? Yes, and many of the "expedition" rowboats are like this. Not really good for a spray skirt though. Google "cross ocean rowing boat" for some representative pictures.

 

Also see "Four months in a Sneakbox" to see where all the extreme small boat voyaging began.

 

Not by the traditional definition. Canoes are open boats with thwarts to seat above the waterline and paddle. Kayaks are decked over boats that are barely wider than the person's hips, who sits below the waterline to paddle. Boats with sliding seats may be partially decked, have outriggers and a large open area for the sliding seat. They can also be beamy boats that don't need outriggers.

 

Yes, there's no problem. Something like this Expedition Rowboat https://angusrowboats.com/pages/expedition-rowboat could be just as well used with a single or double paddle. SUP's are also readily converted to rowing, there are strap on kits available.

 

My version.

 

some say a Rob Roy is defined as "one man canoe" but slightly larger hull seems to be about right. Seems they are mostly cross between kayak and canoe with lower freeboard than normal canoe and mostly short decked fore and aft, and the big cockpit could accommodate a sliding rowing rig.
I'm thinking I'm thinking instead of a compromise that is not particularly good at anything it could be more of a goldilocks Where it would be a Minimalist fast flat water Canoe for 2 paddlers or a roomy stable kayak for a single paddler Or a rowing show more stable and cargo friendly than an Alden but a lot faster than a Wherry or Stretched Light Dory and still able to be carried and car topped by one man.

 

Do you refer to the original Rob Roy, or to one of the many boats sold under that name?

 

Some canoes do not have seats, and are paddled while kneeling. Some canoeists kneel while paddling even when the canoe has seats. While not common it is possible and sometimes very effective to paddle a traditional canoe with a double paddle.

@Squidly-Diddly Why not throw sailing into the mix. Both canoes and kayaks can be sailed.

 

Canoeing, kayaking and rowing are propulsion methods. So a single boat could be a canoe, kayak or row boat.

 

Yes, entirely possible, just a lot of conversion gear to take with you, adding to weight, if you want to be able to combine all 3 in a single trip.
With carefully thought out placement of crossbeams and outrigger hulls, a trimaran layout can enable a very slender hulls and good performance. A pickle fork layout with short stabilising hulls up at the bow that do not interfere with any of the propulsion options is seen quite often and would probably be achievable with a 17 ft loa.

 

My fave feature of my old Aquaterra Prism SOT was that I discovered I could paddle sitting up on rear deck or up on my knees. Sitting up on rear deck became preferred for easy cruising on dead calm lakes. Really helps to change up the muscle-motion a bit.
One of its drawbacks was no baked in way to mount a rudder (or motor) so I'm thinking a vestigial transom to make adding a rudder/skeg would be nice. Make it just big enough to accept the smallest standard outboard. Rowing sculls will have diff size skegs depending on EXPECTED conditions but the skegs are mostly glued in with silicon so they aren't something that can be quick and easy to change out.

Before I got my first 1 hour shell rowing lesson I was set on adding stabilizing pontoons to the rowing rigs outer arms. Wrong thinking like training wheels on a bike, but maybe something could be done to integrate them as supports for lee-boards.

So overall I'm thinking of a boat kayak,shell,canoe shaped hull with some flat bottom like canoe and small transom pocket. Small water tight bulkheads fore and aft, maybe the aft one would include a seating position for a canoe style paddler. Then a baked-in provision to add fabric decking as needed all the way to a spray skirt around a single kayak paddler.

 

Those are the approximate dimensions of an Old Towne "Loon", a two person Rob Roy style hull sold as a kayak. They are quite popular and I buy one for anyone who will let me park it on their waterfront. My parents returned the one I gave them when they sold their lake house, and I sold it because the 150 yards to my water is enough that I never used it. I have 4 kayaks from 10 to 20 ft that are all preferred.
If you see a Loon come up for sale, buy it. The seats mount on rails to slide for different uses and trims. You could make them quick release and swap out to accommodate your needs.
IMHO you can use it in all those ways (and as a SUP like I did). If you know how and compare to purpose-built craft, you can find faults. To new users with no comparison, it will be fine.
The only answer to your question that matters is your opinion.

 

Had a single seat Loon but sold it after one use because my big feet felt cramped under the deck. I guess what I'm really looking for is a rowing shell that CAN be used like a kayak and/or canoe or even sailing canoe, mostly because while sliding seat rower is preferred, your typical rowing shell is completely locked into that mode. So I guess I'm also wanting a rowing rig that can quickly self store along with the big oars and allow the boat to function as kayak and/or canoe, mostly during launching or landing or short trips.

 

Of course, people often call small open boats and surf skis "kayaks". I.E., in modern termnology a boat can be called either one. The only obvious distinction would be using a 1 or 2 bladed paddle. So keep one in your hands, one bungeed on the deck.

Likewise, many closed deck "C1's" now are simply K1's in which the seat is replaced by a "saddle" on which you kneel.

For that matter, if you want to stay with the traditional closed deck=kayak, open deck=canoe definitions, you can add a top skin to a canoe to make it a kayak. Voila.

Almost any boat can have a removable sliding seat system installed, and you could use a removable system. The simplest system is a slippery plastic garbage bag, which some kayakers and canoeists have used, but you could use something with rollers.

I can also imagine a folding skin-on-frame, in which the top parts can point up, or fold together (and seal with Velcro or a zipper) to make a top skin.

Like Jakeeeef mentioned, the more options you add, the more weight you get. In addition, multi-purpose designs tend to be less efficient than single-purpose designs. But while you are at it, you could always add a fold-down mast or kite to make it a sailboat - and a small motor to make it a motorboat. Add drop down wheels and a mechanism to turn it into a tricycle while you are at it. Very inefficient, but it will do whatever you like.

But what's the point? Or do you only have space for one boat, and what to do all things badly, rather than one thing well?