: Hi Guys,

: Paul, I will not completely rule out foam bulkhead compartments. It would be
: easier then what I would be doing in building solid flotation the way I
: would be doing it.

Not to be too confusing here, but I am suggesting solid bulkheads of wood (built up strips or a plywood panel) covered with glass cloth and permanently mounted to the interior. There are some people who cut a piece of thick minicell foam to the approximate shape of the interior, and force it in, where this "foam bulkhead" holds by (either) the modest pressure it exerts on the boat or some adhesive mastic applied to the edge.

: What I don't like about the bulkhead method is that I
: have to vent the compartments from the heat build up to prevent possible
: damage from unequal air pressure. A cork in a tapered hole in the foam
: bulkhead that would blow out would be one easy safty measure and if placed
: at the top of the bulkhead, the compartment could be a drain if the yak
: somehow got water into the compartment, by turning the yak over and
: tipping it up. Sealed in fiberglassed foam, it seems to me wouldn't get
: any more moisture in it then would our sealed in yak strips, but if it
: did, it would have to be torn our and re-done. Ugg!

Your foam is probably 95% or more of trapped air. Once you seal it inside a waterproof layer of glass cloth and epoxy resin you have almost exactly the same problem ( 95% ofthe problem?) as any other sealed air space: when the temperature changes the air inside expands or contracts. Yor ig problem is with added heat. The small percentage of solid plastic that makes up the foam will flex and each little foam bubble will expand as the temperature increases.

How do you plan to vent the foam-filled area? Even if your vent is capped while you ae on the ater, when you pull the boat out at night any vent hole will allow moist evening air to move in when the temperature drops. That moisture will be difficult to drain out. The foam will hold it like a sponge.

I'm moving the next part of your note out of order:

: If too much floation is in the bow and stern it might hold the yak
: too high in the water when flooded and allow to yak to roll when I try to
: enter. And if there isn't enough floatation then the bow and stern may be
: unstable and allow the ends to dip too easlily and destablize the yak. So
: the idea of making a solid foam floatation is because I can put it in the
: water and test the yak and then adjust the floatation as needed.

Exactly. so don't put ANY flotation in the bow and stern until you see what is needed. If you put in too much it is a mess to pull it out. "Adjusting" this usually means adding a bit more until you get what you want. It is easier to add than subtract.

Now, the basic problem here seems to be that you want your boat to be more stable when it is capsized. so you can get back in by swimming in over the side.

: But my reasoning goes
: beyound that and this may be completely faulty thinking, the amount of
: floatation in the stern and bow may need to be adjusted if my side
: floatation compartments are to work for self rescue as I envision it. As I
: see it, the yak needs to be flooded quite abit with water for the side
: floation to bite and keep the yak from rolling when I craw in from the
: side.

OK, imagine a 20 foot long telephone pole floating in a swimming pool. Just by the nature of how it grew there will be one spot that is denser or heavier and off balance, and that pole will rotate until that heaviest spot is underwater. Now, if you play lumberjack and step on that floating pole the difference in density that makes one part of the log float, and the other sink, is not going to mean much. That pole will roll. Now consider two more possibilities: Same size pole, but made from foam. and same size pole but waterlogged. OK, what is the difference if you step on either? as long as the outside shape is the same they both roll just as easily.

If you want it to be stable with your weight applied to the side, you are going to need to add a weighted keel to the telephone pole, or something similar, to keep that thing from revolving around its axis. Or, you are going to need to apply some element that will resist the twisting you will be doing. A small float attached to a paddle and stuck 3-6 feet out, because of the leverage it gets from that distance, provides a great resistance to the natural tendency of the telephone pole to roll. Even without the float, just having the paddle blade hanging out a ways provides resistance, which greatly slows down the rotation of the telephone pole.

OK, so your kayak is not a telephone pole, but it is long and relatively narrow.
If you have flotation inside the boat it will float higher simply because you won't have water inside. But the shape of the hull is going to be a prime factor in determining whether the thing rolls around so fast that you have difficulty in regaining your seat, should you fall out. Adding flotation inside the boat, along side your seat, will not change that rotation.

Suppose you fill the boat with foam. It will float nicely, but if you are outside the boat trying to get in from the side, it will rotate on its axis, and probably flip over and bop you on the head. Stability depends on hull shape, not on internal foam. If the boat is partially filled with foam and then filed with water (swamped) it will ride lower in the water. In this case the amount of hull above water will have some effect on how fast the boat rolls, but the weight of the water inside the boat will not do anything to stabilize the thing. Unlike solid ballast, which, like a keel, acts as a counterbalance, as your boat rolls the internal liquid just maintains its own level -- not helping you a bit, and certainly not significantly "biting" on your internal cockpit flotation.

:Someone
: on the board mentioned that the end floatation might hold the yak up too
: high and that really got me to thinking about it. Floatation bags are also
: a choice.

OK, if the boat is filled with foam then it won't fill with water. If the capacity of the boat is, say, 250 liters, then filled with water it sink to barely be above water level -- and you'll have to bail out about 550 pounds of water. If you put in 200 liters of foam or float bags or trapped air space then you will get only 50 liters of water in (about 110 pounds to bail) and the boat will be bobbing like a cork, and have a high edge for you to climb over if you try to enter from the side.

If this seems like a problem, why not explore other options for remounting the boat -- climbing on from the back or front, say. Or using a paddle float. Or build the kayak with low sides so you cna get on like you would with a sit-on-top?

What ever you decide, though, hold off on your built-in flotation for a while. Unless you need a bulkhead for structural reasons, you can install bulkheads and hatches anytime after the basic boat is finished. And it is not too hard to get in flotation. so, try the bare boat for your re-entries first and see if temporary flotation makes things better or worse. THEN, and only then, you can commit to a permanently mounted, foamed in place block of flotation.

But paddle the boat a bit first. You may have other modifications youwish to make (skeg, rudder, rub strips, etc.) and you cna put these all on at the same time.

Hope this helps.

PGJ

: Rick, I have never liked the idea of foam seats or foam on the floor as you
: suggested and I don't like putting foam under my seat for a good fit to
: the deck floor. My thinking is that since foam floats and if your kayak is
: flooded the foam wants to rise to the top of the water and it add an extra
: destablizing force of trying to roll the kayak upside down as it trys to
: get to the surface of the water like any piece of foam pushed under water
: would.

: If this rescue system doesn't work I will really have egg of my face.

: John