Flotation chamber

[Jim Dodd]

For those building a cedar strip canoe. Consider installing flotation chambers. It's true a stripper is naturally boyant. Usually the gunnels will float just above the water. But a little downward pressure will take them under the surface, quite aways. They also take a long time to resurface ! The chambers keeps the hull higher above the waterline, and when pushed down, they return immediately.

Once I started building flotation chambers, into my canoes, I won't build without them.

Here is a pic of how mine look.

 

[Canotrouge]

I don't like flotation chambers, on any canoes. It makes nesting canoe for fly in a pain, you lose cargo space, and with my longlegs, when paddling in the bow, makes for a cramped position. I don't like them. But I understand there value.

 

[Jim Dodd]

Hi Canotrouge

I understand your position !

This is a solo boat, and so leg room is not a problem. If I needed the space the flotation chambers take up so badly, I'm probably overloading my canoe.

On one of my early tandems canoes, I had the seat too far forward, and it was terribly cramped ! Lesson learned.

Jim

 

[Holmes375]

That's a very nice way to do the chambers - much more pleasing to my eye than the boxed style. And a great way to dress over my less-than-beautiful inner stems

I can also see some advantages when it comes time to 'glass the interior.

 

[stripperguy]

Here's another vote for enclosed bulkheads...I usually do those ugly boxed style ones...IMHO, bulkheads (and decks) provide a quadruple whammy -
1. Hide a multitude of sins.
2. Provide tremendous strengthening of the hull.
3. Provide floatation.
4. Provide a convenient step for ingress/egress, especially on beaver dams.

 

[Canotrouge]

But I really like the way you do them Jim, slanted like that makes for a less "aggressive" look, and it would make a place to put at least on foot in a tandem canoe...
But still don't like them...

 

[Alan Gage]

I think I'll be doing the boxed style, or something of the sort, on my current build. I agree they aren't the prettiest but I like the functionality. I've practiced solo self rescues a bit and even in my 34 pound kevlar with factory float tanks I'm unable to drain it of water and flip it without additional floatation added to the bow/stern. In my case a paddle float wedge in front of the grab handle and then inflated allowed enough flotation to completely empty the canoe of water on the flip. Doesn't seem to me most float tanks add enough flotation to do a whole lot of good and when the canoe is floating upside down they don't really do anything.

Yours look great, Jim. How do you get the pattern?

Alan

 

[Jim Dodd]

Canotrouge
That's OK ! If we all liked the same thing it would be a boring world !
It's at least something to think about.
I always finish the inside beneath the chambers, making sure they are sealed and water tight, but over sanding the inside area, is not necessary. I also glass the back side of the paddle insert to give it strength.
A small hatch could be added to access the chamber also.

Jim

 

[Canotrouge]

Hey Jim, do you fill the void with foam? I know the one I have that have chamber, are filled with foam, so if you end up puncturing/cracking the hull in the area of the tank, water would't be able to fill the cavity.

 

[Iskweo]

We built chambers into my stripper and I like them. They make the hull much more solid.

 

[Jim Dodd]

Canotrouge
I don't put foam in mine. You could, but you would also add weight, and actually lose flotation value.

I've got to say I've bounced these off rocks and trees. I've loaded trash from river cleanups. And still no leaks.
If I were to get to the point of busting up the chamber, I'm probably in over my head anyway !

Jim

 

[charlie wilson]

Float tanks have always been necessary and problematical. Sawyer and Mad River used to use foam, but WeNoNah's weight advantage by not eventually became to compelling, so almost all builders use the lightest option now: air. When Bell transitioned from glued-in, shaped foam chunks we started with flat panels, but they unfortunately minimize volume and locate that volume low in the boat. The hulls want to float like turtles, hard shell up. The ~ 90dg box raises the volume nicely but is less sightly. A nice compromise is an arched panel like Lotus, Bell, Placid, Colden and Swift now use, raises the volume in the boat but no "crease" that requires perfect placement not to seem visually wrong.

It is important to vent tanks to adjust to pressure changes due to weather fronts or altitude differentials. Mad River left the top open. Curtis bored a small vent hole, while Bell, Placid and Colden use a hollow rubber stopper, the latter two slitting the tip so the stopper "burps" with pressure variation. Swift uses a Kayak drain plug and suggests leaving it open in storage and while traveling; tightening it down when setting out on the water.

 

[Mihun09]

I must have the oddball Swift without tanks. I did see them come into being after mine was built though.

 

[Jim Dodd]

Charlie
I've wanted to install those burp plugs for a long time ! just need a source.
I have often worried about the lack of a vent, and on a few of my early canoes, I used a 5/8" bilge plug.
But beings my chambers are a lot smaller than commercial ones. I haven't had any troubles with leaks. I wonder if they might flex enough to compensate for pressure changes?
I guess the real test would be to drill a hole, and pressure test ! But to date, I haven't experienced problems. Some of my chambers date back into the mid 90s.

Thanks for your insight !!

Jim

 

[Philtrum]

Would a piece of Gore-Tex, shielded behind some kind of grate or screening, work in place of a "burp plug"?

 

[memaquay]

I don't see a great need for them with strippers. Everytime I've dumped one, including a 17.5 Winisk, I've been able to self rescue. Perhaps as I get older, this might become more problematic. I would think that installing a couple of airbags for extended whitewater trips would be prudent in any case.

 

[stripperguy]

It is important to vent tanks to adjust to pressure changes due to weather fronts or altitude differentials. Mad River left the top open. Curtis bored a small vent hole, while Bell, Placid and Colden use a hollow rubber stopper, the latter two slitting the tip so the stopper "burps" with pressure variation. Swift uses a Kayak drain plug and suggests leaving it open in storage and while traveling; tightening it down when setting out on the water.

Charlie et al,

We discussed the need for venting in another thread here or on that "other" forum.
Unless you plan to fly the hull at 40,000 ft (in unpressurized cargo space, not in a pressurized compartment) , or take the hull outside of our atmosphere, you couldn't develop enough differential pressure from atmospheric conditions alone to fail the substrate or the joint. Check to see what the lowest and highest air pressures have been during the worst weather extremes and you'll see that the potential loads due to delta P's are inconsequential compared to the strengths of the materials and the adhesives.

 

[Jim Dodd]

I agree stripperguy.

I've seen no pressure signs, no sloshing of water, and no rotted chambers, in my canoes.
Charlie have you seen any chambers blow out from pressure ?

Great discussion !

Jim

 

[Jim Dodd]

Here's a pic of a flotation "Paddle" insert. I glass both sides, for strength.

Jim

 

[Philtrum]

Charlie et al,

We discussed the need for venting in another thread here or on that "other" forum.
Unless you plan to fly the hull at 40,000 ft (in unpressurized cargo space, not in a pressurized compartment) , or take the hull outside of our atmosphere, you couldn't develop enough differential pressure from atmospheric conditions alone to fail the substrate or the joint. Check to see what the lowest and highest air pressures have been during the worst weather extremes and you'll see that the potential loads due to delta P's are inconsequential compared to the strengths of the materials and the adhesives.

At sea level, normal barometric pressure is around 30" Hg, or just under 15 psi. A change in barometric pressure of 2 psi would change the pressure on the flotation tank by 1 psi. If the tank has a surface area of, say, 100 sq. in., it would experience an additional 100 lbs of force distributed across the entire face of the tank's surface. That could be from either the inside or outside. Either way, it's intuitively apparent that stripperguy's statement about inconsequential loads might not be true.