jet powered canoe

Canoe design

I'm trying to select a canoe for this project and would love it if anyone who is an expert on boat hull design would give advice. I'm posting a link for a possible boat i'm looking at using but I'm just affraid from what I've heard that certain boat hulls don't channel water for jets very well at all. It would be terrible if I were to get the boat and motor put together and the jet just chugged air. I've been looking at the design on the Mokai and it appears to have a flat bottom and rounded up toward the front which is somewhat like the canoe I'm looking at. Thanks in advance for anyone who has any insite.

http://www.madrivercanoe.com/product/index/products/river/legend_series/legend_15_rx/

 

Hahahahahahaha.

What wil they patent next? Breathing.

 

Musky, that is a fine canoe for what it is intended to be, all of which makes it particularly unsuited for what you are trying to get it to do.

you want

1. A transom. Bigger the better. Like Grumman sport boat or G. 16' squareback.

2. No aft rocker. If that means you have to live with no forward rocker either, so be it. Best would be no aft rocker and about 2" forward rocker.

3. Cross sections- best to worst- Flat w/ chines. Vee with chines, Vee w/ tight radius chines, particularly staying tight near the transom. Worst would be archbottom, like the legend. Arch bottom is structually desirable for a softish material, but you loose stability at speed vs a flat panel. You wouldn't feel this at a casual paddling pace, but you will under power.

4. Materials. I've paddled damn near everything over the years. For banging around rocky streams I think aluminum is best and fiberglass is second, which may surprise you. I like it because of it's high point loading and rigidity. If you are up against a rock and under power, you need some strength and stiffness not to gouge the hull. Royalex can handle being dragged empty, but is not up to the point forces you will encounter. Mad river made a three layer poly hull marketed as TT (triple tough). It would be better, and it is repairable with a few tricks to get epoxy to stick to it. Royalex would be my last choice for the sort of duty you plan for it. It is a very good stuff for a normal canoe, but I think they have also done a good job of optimising the stuff, and there isn't much in reserve for additional abuse.

One effect of having a motor in the canoe is you can't just hop out of the boat in an instant the way you do with paddle craft (neither will the bowman). Staying in the boat longer means the potential for a lot more concentrated loads.

There have been about ten of us who have tried to get you to consider the design needed to perform with a motor. Please take a minute and reread the thread and notice the direction we are all pulling you.

 

Musky:

Is there some way to rent, borrow, or find someone who has used a Mokai to go up rapids? Just about anything will work when the rapids are deep, but going upriver AGAINST fast current and in SHALLOW rapids is another matter... Seems like jets would stall when they chugged air in the shallows and the massive weight would work against everything....

http://www.boatdesign.net/forums/inboards/prop-shaft-systems-24636-4.html Post #53 & 54

JMHO
Porta

 

I appreciate the response and like I've said I'm still in the brainstorming stage. Like you pointed out about the rocker it would be ideal if I had a 2-3inch in the front and none in the back (which I don't think exists). I was thinking that if I shortened this boat a little to put on a transom it might eliminate the rocker in the back. Your analysis on the materials really did surprise me since I've heard aluminum canoes really like to stick to rocks. I really don't have a ton of experience with canoes so I can't really say a disagree or anything. I'm not really concerned about load carrying abilities just having the option of carrying a passenger, which is why I'm not really looking at a mokai as someone had suggested although I would love to try one out. I have never been in a grumman or other 17ft canoes but image they would not handle skinny white water creeks very well.

 

I just thought I'd post a picture of one the rivers I plan to take the boat to. On a side note I recovered a smashed up white water kayak out there this weekend so I've got that project in the mean time.

 

Beautiful water, that helps a lot as to the challenges!

I have done this type of rapids with the ODC 420L float tube (8#) or Discovery Trekker by portage on my back upstream, using 1 boat per passenger. Northfork outdoors also has larger, very lightweight & high weight capacity units made from surgery fabric.

Might be possible to drag a sealed kayak upstream by attached line from the shore. Very high volume of water; an open canoe could act like a scoop and swamp or roll over instantly if it momentarily turned sideways to the flow... Precise steering & power control needed by an expert with a jetboat, because of standing waves and your high relative speed upstream to water while in the rapids...

JMHO, from years of experience....

Porta

 

I posted some links to jet kayaks on a separate thread. A couple of them do 25 to 30 ....

Two of those, and you would have more friends than you want fishing with you.

 

The canoe you posted has moderate rocker which helps maneuvering when paddling, as the canoe will pivot easier. I'm not too sure whether you need that or even want that with a jet drive hooked up, it might get sort of squirrely over and above what squirrelyness is in a jet drive canoe to begin with. I doubt you will be doing any stand up fishing in a canoe that small.

A tupperware boat is more durable that fiberglass or aluminum. Fiberglass will scratch and scrape badly, and there isn't much thickness in the hull to begin with. Any scrapes will be halfway through the skin thickness easily. Aluminum is a little more durable, but will dent and also leave aluminum fart stain type skidmarks on any rocks you contact, if that matters.

I guess a bilge pump might work in a canoe, but generally canoes tip over and fill up immediately. That's where flotation comes into play. If the canoe fills up and floats level with the water, it more or less becomes one with the water. It also weighs, or at least has the inertia of, all that water. So it's full of water and moving along with the current, if it comes up sideways against an obstacle like a rock, chances are it will wrap itself around the rock. A fiberglass canoe will be crushed and broken, an aluminum canoe will look like this



or this



A tupperware canoe will look like this



or this



Pretty much done for.

I think that for the moment it's irrelevant what would happen to this canoe.



So canoe flotation for whitewater should be full size airbags that will keep it pretty much floating on top of the water even if it's upside down or on it's side. That keeps them from getting all bent out of shape.

The tupperware Royalex canoe would be the most durable, but as far as I know nothing sticks to it, so any modifications such as lopping off the back end or making holes for jet intakes would have to be mechanically held together and sealed with flexible caulking. The transom could be wood with screws and caulk, possibly with an outside metal strap the screws would go through first to distribute forces evenly (you don't have to worry about being hydrodynamic and streamlined with a jet for power) and the intake would have an outside fitting and an inside frame that would bolt together with the hull and caulking in between.

 

samsam, I tend to agree with you about the material durability. I own both aluminum and fiberglass boats, although neither are canoes. I've chunked the fiberglass in a shallow calm creek, and the riveted aluminum boat just seems no match for impact against rocks. I was looking at aluminum canoes and most are .05 inch thickness, my boat is .07 inch thickness and seems flimsy.

 

Quality self bailing whitewater inflatable kayaks/rafts don't have any of these rough water durability issues. Small punctures are not a problem, but rare, big tears could be worse... There are large catarafts with motors used in the Grand Canyon which are very stable (non squirrely) in rough water, but I don't think they can go up some rapids...

P.

 

Let me throw out an idea that comes from 4-wheeling.
Use a spear gun to shoot a hook out in from of you, and then winch the boat up to the hook. repeat as necessary to reach destination.
Equipment need to do it would not weigh much.

 

Nimble:

Good thinking, out of the box! I haven't tried that yet. You would need a fast power winch, don't think arm power would be strong enough or give good control.

The hardest issue when going up FLOATABLE rapids is precise control required. You will be constantly buffeted about back and forth by many UNPREDICTABLE eddies of current, and must respond and correct steering and balance power INSTANTLY in response. This is a big sport in New Zealand, where there are a lot of skilled operators. Still many casualties though:

http://www.youtube.com/watch?v=Yn3lOtabSNo

Porta

 

What I gather is going upstream isn't the challenge or excitement per se, it is a practical matter of avoiding leaving the car upstream.
It wouldn't be a fun ride up.
The american river here has buses that will take you back upstream in the summer, probably not an option most places.

As that video shows, even a jetboat won't work too well in that water.

 

go for it if ur not selling them no probs. let me know what the is made from, if not sure was it roto moulded ? I can tell you about welding in more plastic work. Yes a small jet and motor will weigh about 55kg