JEM Watercraft

Hello all...
I'm new here but very impressed with the boats JEM is designing and with all of the building that is going on. There are some VERY talented craftsmen/women here.

I am seriously considering building a kayak, interested mostly in a tandem SOT or something like the Wadefish that I could take my 7 year old out fishing in... Honestly, her recent interest in fishing is just a convenient excuse for me to get out on the water in some fashion.

I am very please by many of the designs here, and by other designers as well. However, I am curious about the lack of incorporation of some form of positive buoyancy in any of the designs I am seeing. I have seen buoyancy bags for sale on some sites. But to me, these seem somewhat gimmicky and a half-measure. By adding a couple of cubic feet of closed cell foam spread throughout the deepest darkest recesses you would gain 100 or more pounds of bulletproof positive buoyancy.

So, is there a significant design reason for not including foam in these designs? Is the added weight that much of a concern?

Thanks to all...
Mksdad

because wood floats!

Seriously, that's the biggest reason. But there's nothing that says you can't add it on your own. Just be careful of the expansion force of the foam. It will burst seams if you overfill a closed in void.

Pool noodles are cheaper and easier to install. But seriously, they do work extremely well, are removable, and if water does get into the deepest darkest regions, they allow the boat to dry out. I also stuff those air pillows that are used to cushion items being shipped to my wife (constantly) from Amazon.com into the empty spaces. They are free.

Matts SOT designs I have built have built in bouancy compartments....................its not hard to do in a SOT due to double hull configuration

Thanks all for the replies...

I am not really thinking about expansion foam. It is risky and foam blocks or noodles offer some definite advantages like removability (Craiggamesh - love the noodles idea, much neater than all the foam pellet mess) .

Couple of thoughts:

Compartments are rarely as watertight as we would like. Also, allowing drainage from the buoyancy compartments would be a good thing potentially.

How much positive buoyancy do plywood kayaks typically have without watertight compartments, bladders, or supplementary foam? Will the inherent positive buoyancy of a wood kayak compensate for the typical rigging of a fishing kayak (not tackle, rods, bait - just the mounted hardware)?

My impression is that a swamped kayak would be a heck of a lot easier to recover if a sizable chunk of the interior volume was filled with foam, not water.

Maybe I am over-thinking this... however, I have fairly significant experience in small boat building (not kayaks or canoes though). A lot of foam could be added without compromising storage (laminate to underside of decks, infill between stringers and framing, inside gunwales around wells, bow and stern bitter ends...). Is this simply not a big issue given the inherent buoyancy of the hull materials and the added weight?

Pardon my ignorance... I have built wood plank-on-frame and fiberglass boats for a living. However, I have never set butt in a kayak. So this is new territory for me.

Thanks for the info!!!

Mksdad

for a plywood hull encapsulated in moderate amounts of epoxy and fiberglass:

If all openings are filled, the hull will sit right at the waters top. Now if you add rigging that isn't buoyant ( like hard plastic hatches or rod holders), then it's going to sink some. How much depends on the weight of your rigging.

A kayak , like the one I have , is 17 1/2 feet in length , both ends have watertight bulkheads and hatches to open and store camping gear in them. You could say 2/3 rd's of the boat is sealed. The only open area is the cockpit which would become flooded if I take a turn in it. If I have a splash skirt on then even that area is sealed to a degree.

No I have not rolled it to find out but I do know that on the top of the vehicle and driving in a hard rain for a couple of hours at 55 to 60 mph there was not a drop of water in it when I got home. There was a travel cover over the cockpit when it was on top of the vehicle.

I have rolled one of the wood canoes and with the ends sealed off ( a small chamber at each end) with wood and fiberglass it floated even with all of the camping gear in it, well what did not float on down river and was later retrieved.
I was thinking of packing the ends with the Styrofoam pop corn before sealing them but did not do that.

Chuck.

Thanks all, this is very helpful... so foam is not essential since a kayak (no gear or fittings) is typically approximately neutral buoyancy if fully swamped. Add some watertight compartments and/or a small amount of foam and it should remain neutral with a fair amount of gear and hardware.

Very interesting... I might just toss some noodle chunks in for good measure but my mind rests easier!

I appreciate all of your help.

Mksdad

Adding some flotation would add some insurance toward safety. You certainly could do any harm by having some.

I did something similar to Bemm on my Sabalo build. I made 3 separate water tight compartments. All three would have to be opened at once for the boat to completely flood. In my Pirogue I did as Old Sparkey and added water tight compartments at each end. I added round quarter turn inspection hatches to them so I can store valuables like a cell phone and wallet inside.