Kayak Trimaran Concept Help...

WU! first post

So for some time know ive been having the idea of turning my kayak into a trimaran for limited ocean use. im harboring the idea the doing this will add significant amounts of stability as well as increased weight capacity. Only real problem is i have no real experiences with boat design and am wondering if my expectations are unreasonable.

so a here is a little more info on what i have in mind.

I have a Ocean Kayak Prowler 13. which looks like this


which is a pretty nifty kayak. it holds ~ 450 lbs of weight and is know to be fairly usable in the ocean granted its not a that bad of a day out. i find my self not using the kayak because im not a big fan of hanging around streams, mangrove areas/ flats etc. i know alot of people do go out into the a fair way out into the sea ~ 3-6 miles on kayaks, but a flimsy kayak in a sudden weather change in not a very appealing idea for me especially that far out. so i wanna turn that sucker into a trimaran.

there is actually a commercially available kayak with this idea in mind tho its over price like crazy IMO.



its nice and defiantly sea worthy getting somewhere around 12 -15 knots with that sail. its a 18 footer with like 600 lbs of weight capacity.

i wanted to make something similar to this with my 13 footer. it doesnt seem that hard to do. i was planing on just using some aluminum pipe similar to this.



the person that made that used what i think is a cut in half long surf board or a wind surf board to make the outrigger floats. long boards like that are kinda price so i was thinking of using 2 caped 8 inch diameter 10 foot long PVC pipes. i believe that 1 foot of 8 inch pvc floats 20.8 lbs fully submerged so a 10 ft peace holds 208 lbs. divide that in half considering the float will be half way out of the water - 56 lb which is what the pipe weighs it would hold 48 lbs with no weight on it and 152 lbs fully under 2 floats would hold a max of 312 lbs if both where fully submerged (dough that happens with this design) so at most the boat should hold 762 lbs if i distribute weight properly
606 if i put most all on one side.

my goal for this project would be to be boat to be able to carry at least 2 ppl with maybe an added 3.5 hp engine in the back, with maybe a cooler and some other gear. idk if i want to add a sail or not.


my concerns are so far.

1. is the boat 13ft to small for the suggested mods.

2. is my conceptualization of the added outrigger weight capacity correct?

3. how do i securely attach the support beams to the kayak with out them ripping off in turbulent water. 2- at the very very most 3ft of waves.

anyone have advice or have anything to add tho what im thinking? maybe some important faces i over looked?


thanks

 

Making a trimaran out of a kayak for sailing is a pretty good idea. Making a trimaran out of a kayak for carrying weight and gas power is a bad idea -poor cost/weight, poor drag at speed, not seaworthy, poor setup time, poor resale...

Before you start counting the displacement of the ama you need to make it streamlined at that displacement and consider the drag. I don't even think the kayak can carry 450# because at speed waves will break over top and run the full length.

If you want to carry 600# with 3.5hp motor you would be far better off trading your kayak for a square back canoe 17ft+....faster, simpler, more seaworthy...

 

You should be able to find old Windsurfer hulls on Craigslist for FREE. Just gotta keep checking and be read to pounce.

I've found entire complete working windsurfers, and bare or damaged hulls much easier. Ditto with surf boards.


Instead of a tri, have you considered ringing the boats gunnels with 'pool noodles'?

 

When the ama cannot hold more than a cubic foot of air, you cannot expect to carry extra weight.

13'?

That is bare minimum for a one person kayak, unless it is being used for stunts.

Ocean going? Decked canoes do better for that than 'most' kayaks. Most kayaks are designed to get and stay wet, not what true kayaks are for, they were intended to keep you dry and alive - wet anywhere near freezing usually means painful death.

 

Here is a good article about CLC's slow evolution of their trimaran kayak, everything from concern about over-stressing a kayak designed for lower speeds, to which of their kayak models are great as trimarans - note: they chose really long kayaks first.

http://www.clcboats.com/life-of-boats-blog/kayak-sail-fun-evolution-of-a-kayak-sailing-rig.html

wayne

 

Welcome to the forum.

the forces on the beams can be quite large and if you do this it is important to back up the inside of the hull where it attaches to spread the load out. A piece of plywood or fiberglass laminate glued in place with polyurethane glue, where you pass the bolts through would be a good idea.

I would skip the motor and just make or buy a small sail and enjoy it as a micro trimaran.

You can make amas or outriggers pretty cheap out of AC plywood and deck screws, use caulk at the joints. or even better, go skin-on-frame. It should not cost you more than about $60 in materials to make wood or skin-on-frame outriggers.

make them triangluar in cross section and run a stringer at each corner, curve the bottom or keel stringer and bring each end to a point and the front and back. It will make a perfectly good outrigger with a fairly low drag shape. 1x2 stringers, about 8 ft long would be good, about one foot on a side. cover with 8 or 10 oz canvas or polyester fabric (use rust proof stables) and seal it with polyurethane floor finish or oil based paint (5 to 7 coats).

you might look at how this all wood catamaran hulls are built for ideas (free plans at link below). some would cover the plywood hull with 4 or 6 oz fiberglass, which will improve durability, but not really necessary to just take it out and have fun with it.

http://svensons.com/boat/?p=SailBoats/Hobby_Kat

good luck

 

Also look at: http://homepages.paradise.net.nz/garyd/Tamanu.html

and

http://smalltrimarans.com/blog/

 

Schedule 80 plastic perimeter (4-6 in) drain type pipe can be steamed, believe it or not. One could cheaply experiment with it and "form" it into a better float shape than a straight one and into one with an upward curvature.
I learned this when I steamed wood in such a pipe. I wondered how hard it would be to make a wood form that the piece would slowly be forced into. PVC becomes quite malleable at relatively low temperatures.
You would feed live steam from a tea ketttle into a sealed pipe with a plastic tube.

 

im really hesitant in thinking of wooden hulls. i know that this is one of the roughs i can take but i fear not having the skill or know how to make them and 2 unless i can make them with a saw, drill, hammer, screws and adhesive i feel im pretty unequipped to make them.

the pvc pipe thing was just because the ease of sealing and making. pretty much buy put the caps one the ends with sealant and boom it floats . defiantly not most hydrodynamic.

why is the engine that bad of an idea? some ppl put them on just normal kayaks with out anything else on it

http://www.youtube.com/watch?v=WOjs4HpkOAg

http://www.youtube.com/watch?v=Dnubsg3FRq0

 

ermaclob

You want to take a 13' kayak on an ocean going trip .... easy.

Put it on a 30' sail boat as your one person lifeboat.

Just because you saw it on youtube, or tv does not mean it will work in bad weather at sea.

 

which is precisly why i come asking questions before further planing.

i feel we might have different interpretation of ocean going...

i want no more then 2-4 miles at most of shore in nice calm water. with some reliability to run back to shore if weather gets ugly quick.

or is this to ambitious?

 

No. "WE" do not, you do.

There is no 'run back' if the weather gets ugly. If it gets ugly, you have to ride out the weather. In an overloaded plastic kayak?

Keep your PFD's on .... and at least an upper body wet suit, people die from hypothermia in Florida in the water, if the sharks don't get them.

 

Ok, so if my expectations are unreasonable to you how would u build such a craft and what limits would you uphold? keeping in mind im going to use a 13ft foundation

how would you modify my outlook on the situation / goals to be more suitable?

im not here to argue anything just get the right perspective. as far as boats are concerned anyone here knows more then me.

 

I know it sounds like all I am trying to do is throw ice water on your dream.

Well.

I grew up on the water in a skiff. And I, sometimes my brother and I, or sometimes with our father, rowed home in a hurry as the South Texas weather changed in just few minutes.

I regularly rowed a half mile each way.

But, when the chop went from smooth to 9 inches, rowing quickly became work - for a half mile. Wet, and miserable quick. Makes it real difficult to stay focused, and to stay paddling.

You will NOT have that nice option in the the Atlantic riding the Gulf Stream.

If you get stuck in 4 to 6 foot swells, YOU WILL NOT SEE LAND. And in a squall? You won't see 40 feet.

Cold rain, wet, miserable, hoping your sail would help you, as your undersized kayak continues to swamp with you and the extra person, you now realize you should not have brought along, the extra person, or the sail.

You begin to think about tossing overboard the worthless sail, because the wind is blowing away from land.

A very common occurrence between a land mass and a large water mass.

And then the 3.5 hp outboard begins to sputter, you realize you might have water in the gas .....

Now you realize the outboard is just a big anchor, and time to donate it to Davy Jones' Locker. And you hope you can do the same thing with the extra 100 pounds of sail, that you thought would be a good idea with the now seriously undersized amas (floats).

Ambitious?

Maybe.

But, not only is Florida the capital of shark attacks, it is also the capital of quickly changing bad weather, lightening strikes, and tornados. Water spouts when over water.

Once you are more than about 50 yards from shore, there is no such thing as you controlling the weather long enough to paddle in.

Rip tides are always present, and just when you think you know the beach well enough to push your 4 mile limit, you find there is a new rip tide, taking you the wrong way at 4 to 6 kts.

And then you might remember one thing.

Do NOT FIGHT THE RIP, TRY TO MOVE WITH IT .... It will take longer to get to shore, but you can get to shore after 10 miles of rip current, or never get to shore trying to fight it.

Most people find the rip will take them out when they try to fight it. A few heroes get lucky and on lives the crazy idea you can fight a rip current swimming or in an undersized boat.

 

If you want to go with 13 foot, do not try to carry a passenger.

But, your only real option is to trade up to a more sea worthy kayak, or a decked canoe.

And never leave your PFD's and wet suit at home ....