Tortured Plastic Kayak.

[alexlebrit]

In THIS (http://www.boatdesign.net/forums/showthread.php?p=139756#post139756) post, I was trying to work out a way to make a cheap, expendable sit on top touring kayak for canal use. When I say expendable I mean I have a particular use in mind for which the boat will be built (pedalling the Nantes-Brest Canal) but after that it'll probably only get used a few times a year.

I've been looking at a lot of tortured ply designs, but my ply torturing skills are limited to say the least and ply here in Brittany is very expensive and hard to order.

But I did find some large 8'x4' (well 2.5m by 1.25m) sheets of PVC available in 3 or 5 or 7 mm thicknesses. It's more flexible than the equivalent plywood, but still fairly firm, however with a hot air gun it's easy to bend and you can even get gentle complex curves out of it that way.

So rather than build a stitch and glue ply boat I thought about a PVC boat. I've used Kayak Foundry to modify an existing design and to give me offsets. The plan is to make two halves, bow and stern, and then join them after.

The build goes like this:


Trace offsets onto 7mm PVC, cut out.
Lay these one on top of each other so the water line on each one is lined up.
Drill two 40mm holes through the entire stack
Drill out a more holes (see part 10)
Slide these over 40mm PVC pipe and space to give bow and stern sections.
Glue in place with PVC Cement
Bend 5mm PVC sheet over to form hulls and glue in place.
Flip over and glue 3mm PVC sheet to give deck
Tape joins
Fill inside of the hull shapes with bouyancy foam


Now I've got two halves ready to be joined. Final bulkheads (with no "foam holes" will be glued in place on the "cut" ends. To join them I simply plan to slide 32mm Aluminium tubing inside the 40mm - it's a snug fit. The bow section will have a slight overlap of "skin" and the stern section will have a small "stepped" part to correspond with this. This will prevent any up and down motion of one part to the other. To hold the two together as it's on calm water only I think I could use something as simple as velcro sheets, hooks covering one bulkhead, eyes the other.

I think it should work, it should be cheap for sure, I'll report back on what happens. If anyone can spot any major flaws in the plan, let me know.

And why two sections? Because I drive a Mini Cooper and it's 10 foot long. A 16 foot sit on top touring kayak on the top would be too much for the gendarmes to take.

[Bergalia]

Alex - like your idea. You may be interested in this item - from an Australian ABC TV show called New Inventors:

One of the inventors is Owen Griffin who came up with his 'Tryak' a canoe which can be broken down into 3 pieces (or 4 pieces - optional), making it compact enough to transport in the back of a small car.

Once you get it to the water, it takes 15 seconds to put together, thanks to the unique assembly method that does not use screws, wing nuts or require tools. It’s simply a nylon strap that runs through the hull of the kayak from back to front and does up with a ratchet. (Like a luggage tightening strap)This means it is totally self-contained and there are no parts or tools that can go missing.

The Tryak can also be assembled whilst in the water, making it possible to use with small boats that have limited deck space.The Tryak is a new design of ‘sit-on-top’ kayak, intended for calm water conditions.

For more information about Tryak, contact the following:
www.tryak.com.au

[alexlebrit]

Well look at that - isn't it always the way, you think you've come up with a great idea and someone's got there before you. That is exactly what I had in mind, especially as I've just increased the length to 7m which migh be a bit over the top on a 3m long car !!!

[Trevlyns]

Oh well done Bergalia! :D

[waikikin]

That kayak is fantastic, the tensioned wire/strap is the way to go- I read article in practicle boat owner years ago where a bloke built a "canal cruiser" out of ply, like 2 punts/john boats, trailered it as a camper trailer with 1 punt inverted & when he got to the cruising area would join 'em with a tensioned wire down the inside of the topside panels- locating "nubs" on the transoms helped locate the hulls too, a small outboard & windsurfer rig & oars were the propulsion. The system worked well for him & he cruised the UK & continent in this fashion, the tension system goes back to maybe Greek ancient time? & I think he named the boat in that regard & is still used in building of bridges & other civil works today. The 3 peice design I reckon would be much stronger than a middle join considering the paddlers weight position & the lower bouyancy of the ends being joined on, maybe it could also be paddled with out the ends as well. All the best with it Alexibrit from Jeff

[Bergalia]

Well look at that - isn't it always the way, you think you've come up with a great idea and someone's got there before you.

Hey Alex, I'm working on something I've temporarily called 'The Wheel...' I think it might be a goer.....:D

But that's what 'ideas' are for. There is (cliche to follow) very little that's new under the sun. Press on with your design - that's what boat building is all about. Find a problem - find the solution. It's your problem - and your solution. Again - good luck.:)

[alexlebrit]

Bergalia that sounds just like the solution to my problem, I've invented a thing I call "The Bicycle" but I'm finding that it doesn't move that well as the ends of the forks dig into the ground. :p . It's true there's few things that someone hasn't thought of and then out of left field - the wind up radio.

Jeff thanks for the good luck thoughts, I think three sections is really the way to go as that way I can have the seat and pedals (for it'll be pedal power) all in the one section. Two sections only and I was worried about pushing them apart with each "down stroke". And tensioned straps is just so simple and easy.

Anyway I've got the design sat here on Kayak Foundry, now to work out how to get it into something 3D so I can do those flash renderings everyone loves so much.

[Poida]

Looking at the two section kayak, it looks like it gives the occupant a waterproof seat and interior. With 3 sections this may be more difficult.

Poida

[Bergalia]

... true there's few things that someone hasn't thought of and then out of left field - the wind up radio.


Oddly Alex - I've got one - a wind-up radio. Built for the depth of PNG (Papua New Gunea). Heavy spring and you get about five minutes of scratchy voices before it needs rewinding. Found it at my usual shopping outlet (the local tip recycling shed) - cost me all of ten cents...

Now get to that kayak.....I'll be listening....:)