: Paul, my thoughts have been to put the blue foam in while the hull and deck
: after they have already been fiberglassed inside. To put the layers of
: foam together and shaped to fit the hull and deck bow and stern while its
: easy to get to in both halves and then glass the halves with tape
: together. Any mildew spores would only be against glass and wouldn't
: effect the wood. If you think it would still be necessary for some
: ventilation, perhaps a small line of expanding gorilla glue could be put
: on the shaped foam and gently set into place leaving ventilation channles
: between the boat and foam. Thinking out loud.

A few points to ponder: The main one seems to be a basic desire to stuff your boat with more flotation than needed. Way more.

Consider your flotation needs. When loaded for an expedition your boat will displace, say 500 pounds of water as it settles evenly, to a depth of about 7 inches (I'm giving some typical specs here, your exact boat should be close, but will indeed be different.) That includes the weight of the boat, some gear and the paddler. For a day trip the boat will float higher, maybe at it's design waterline, or a depth of about 4 inches, and weigh in at around 200 pounds. These two cases are probably the extremes of use.

Now, let's figure out how much water you have to put inside the boat to get it to sink for each of these cases. Once we can calculate that amount, we use the information to help us determine how much additional flotation is needed. The process is just a simple subtraction.

For example: If the boat holds 700 pounds of water, and it sinks when it weighs 690 pounds, then we just have to displace 10 pounds of water to keep the boat barely at the surface. I round things off and figure 60 pounds of water, or about 8 gallons, to a cubic foot. To displace that 10 pounds of water we need either 1/6th cubic feet of flotation ( a sealed space, or a block of foam 1 foot by 1 foot by 2 inches thick) or about 1 1/2 gallons of sealed, empty bottles.

We could calculate the volume of your boat by analyzing the plans and doing a little calculus, but there is a much simpler method: Take your boat out into shallow water of maybe 2 to 3 feet deep. Fill the boat with water and then measure how much you scoop out. If you take out 150 liters, or 150 gallons, well, that is the volume your boat holds.

But wait. Even this may give you totally useless information about flotation unless you check one very important item: When the boat is completely full of water, is it still afloat? if you built your boat of wood and covered it with glasscloth and plastic resin, then your boat probably will still be floating above the waves -- even when completely filled with water.

For the heck of it, you might want to add rocks, or an anchor or two, just to see how much MORE weight it would take to sink the thing. My guess is 15 pounds (plus or minus 5 pounds).

Now, if you want to have some real fun at the beach, after you sink your boat, slip in a piece of plastic foam and watch the boat bob back up to the surface again. If you have a 4x8 sheet of 1-inch or 2 inch-thick foam (color is unimportant) You can cut 32 pieces that are a foot on each side, and each will give you 1/12th or 1/6th of a cubic foot of flotation. That equates to about 5 pounds or 10 pounds of lift respectively. Throw in 5 pounds of lift and up it comes. Add 5 pounds of rocks and down it goes.

Now, frankly, this probably seems a bit foolish, but it leads to a lot of very vital data. To start with. once the boat is barely afloat, instead of adding rocks, slip into the open boat yourself. Does the boat sink or not? If it sinks, add flotation until it is afloat. Whatever you add is going to be the minimum amount of flotation you'll need. If you have not added any ballast or extra weight to your boat during this test, there is a chance that the boat will remain afloat without needing any additional flotation at all. A lot depends on how much of your body is above the water.

If you get into trouble on the water, in the worst case situation your boat will fill with water. That's all there is around you, so that's all you have to worry about. You won't get any added anchors, or sand, or rocks thrown inside the boat. Just water. And water makes you and your gear float, so when the boat is filled with water, the effective weight of the contents changes.

A block of foam that weighs 1/4 pound in the air, not only is weightless in the water, but has effectively got negative weight as it provides lift through displacing the heavier water around it. Your body is probably over 125 pounds in the air, but it is nearly weightless when totally submerged. ( If you want your torso to remain in the air despite the boat being filled, you need to add enough flotation to support just those parts of your body that are out of the water -- probably 60 to 70 pounds worth.)

Your gear, including the cast iron frying pan, 5 gallon water jug, and 15 pound tent may weigh, 100 pounds in the air, but if it is carefully packed it will float. If it floats then it adds bouyancy to your boat. Lets look at how:

The 5 gallons of water is about 40 pounds in the air, but it is water -- same as what you are paddling in -- and when the jug is submerged its weight zeroes out.

The other gear, if packed in a watertight bag will float depending on the volume of the bag and its weight. A lot has to do with trapped air and light objects inside the waterproof bag. The first thing we learned about packing for canoe trips in Scouts was how to wrap our sleeping bags in tarps so that water would not get in (triple fold the edges and hold them in place with a light cord wrapping the bundle like a Xmas present) The bundle would float like a cork. If you use watertight bags for your gear, or wrap it in plastic sheets or poly tarps, then your gear becomes your added flotation should water flood your boat.

Actually, things are even better than this, as it is highly unlikely that your boat will ever completely fill with water on its own. A tip onto one side -- not even a roll -- should bring one side up above water and let several gallons of water flow out of the cockpit. Straightening up leaves you floating a bit higher. A bilge pump will remove water as it comes in, and if that should break, you can use your hands to splash out a lot. You won't be dry, but you'll be afloat and maneuverable. At this point you bail.

So, you don't need a lot of flotation to do the job. On aluminum canoes they seal an area about 5 inches long near the bow and stern to provide the necessary flotation. On a wood kayak this would be a bulkhead just a few inches away from the endpours. The volume of trapped air would be rather low, and thus any expansion or contraction from temperature changes due to sunlight, or seasonal effects would be minimal. Or, you can have an open area that can easily drain, and which holds a flotation material, like your foam. If you go this way I still suggest making the area enclose your flotation securely, but in a manner that allows you to occasionally remove it.

If you don't go with foam, then clean, empty, 2 liter bottles are nice. They are cheap, easily cleaned, and you can just chuck them into the bow and stern ends before adding your bulkier gear. In a pinch you can use a few of them for storing potable water, too. Or, you add additional rescue equipment to your holds. Those padded boat cushions, and cheap PFDs are listed as Coast Guard approved flotation devices, and the discount stores have them for reasonable prices. In the event someone else is in trouble it is nice to be able to dig out some flotation you can share. You can't do that with materials you have epoxied into place.

When it comes to portaging ( I know you hate the sound of that word ) any permanently installed flotation adds to the weight you will carry. If it is removable you can take it on a second trip. Personally, I'd rather make three trips with 40 pounds of gear than break my back trying to shlep 120 pounds on one trip.

Anyhow, if you continue with your design of adding flotation in the cockpit, I think you have more than enough. Any more you can supply with an inflated drybag which is both easy to secure, and easy to remove.

Hope this helps.

PGJ