will a wooden power boat float

[sdowney717]

if it had no engines, heavy metal parts and is swamped?
or is the wood too water saturated to give it the bouyancy needed.
If it will, then if you wanted to make a wood boat unsinkable you would only need to overcome the weight of the engines and other items heavier than water?
I have been wondering about this, I assume the old wooden sailing ships that sink had too much ballast in the keel and that weight overwhelmed the bouyancy of the wood.

[Gary E]

will a wooden power boat float I have see little cabin crusiers floating, even with a inboard engine in them, but ususally it's is bow pointed up and probably trapped air holding it up...

I would not count on it though.. and as for some sorta life jacket for the boat, I think good inspection and maintenance is all you need.

How biga life jacket would ya need for that Egg?... King Kong dont wear one that big... :D

[ssor]

Drift wood floats for months. I would think that the top half of the boat is not too wet, so probably you could find it and drag it to shallow water. A wooden row boat will float when swamped.

[sdowney717]

I keep toying with the idea. After spending so much energy and time on it, I would like to make sure the boat would float even if it got holed.

I have one side completely finished. The other side is replanked and only needs the last 7 planks put back on. I must say I have gotten a lot of respect from those that rebuild boats at the yard, more than I will ever get off this site, but you can never truly appraise a job until you actually see it for yourself. But its starting to get cold, I can still work outside in the 40's as long as the sun is shining.

[Andrew S/Y Rocquette]

Think Archimedes - as soon as there is sufficient water within the hull to overcome the buoyancy created by the displacement of water by the hull and its contents, it will sink, regardless of material of manufacture.

A wooden dinghy will generally float even when swamped, as the mass of the volume of water displaced by the hull itself is more than the mass of the hull: the hull is less dense than the displaced water therefore it has positive buoyancy, and QED it floats.

Similarly RMS Titanic would have floated, had the damage been less extensive as the sealed compartments would have had a positive buoyancy...but too many of them were ruptured (or were not truly water-tight), so the overall mass of the hull and contents was more than that of the displaced water by the said hull.

That's about it, really...hope this helps!

Cheers

Andrew

[sdowney717]

I had no doubt I would have to create enough water displacement to keep the boat floating no matter what happened.
I have wondered about blue or pink extruded polystyrene foam (XEPS a closed-cell foam insulation similar to MEPS) 4' by 8' sheets you can buy at the home centers. Cut them up into strips wide enough to fit between the floors and long enough to run up the sides filling the cavities under the sole. That way they could be pulled out for bilge inspection
Though it may be really impractical to attempt this.
All you really need is enough displacement to keep the boat up not at the normal waterline say but perhaps having only the sole a little wet.

[Andrew S/Y Rocquette]

I'm no expert, but I believe some of these foams very easily themselves get waterlogged extremely easily - so you need to get the right stuff!

A

[sdowney717]

yes, the polyurethane foams do waterlog easily.
The little looking I have done told me the polystyrene sheets dont absorb much water. Some claimed only 1 to 3%.
So I took a piece of pink foam (Owens Corning makes pink, Dow makes blue) and put it in water, after a week still seems dry and I cant squeeze water out of it.

[Andrew S/Y Rocquette]

so...assume the wood parts of your boat will have positive buoyancy (some woods sink, but fewer than float), calculate the amount of weight of the "sinky" bits like engines, get a fixed amount of your foam and weigh it down in the bath 'til it sinks so you know the amount of foam per poiund/kilo...fresh water slightly less buoyant than salt, and factor in a safety margin!

Should be able to sort out how much you need...rough and ready but accurate-ish.

[Gary E]

Your doing a fine job on that Egg, I can tell just from your posting and persistance. It would not surprize me to find that you will need a 5 gal bucket of water tossed in the bilge to see if the pump works. Your boat will be fine... you worry to much....

[neptoon]

not for ever

[ken.bryant]

If it were all wood (for most woods, anyway) it would float, marginally, no matter how waterlogged. So an approach to guesstimating would be this: Calculate how much flotation you need to offset the weight of the metal bits; then what's left would act more or less like a log. So say, for example, that there's a 500 lb. engine that occupies 2 cubic feet of volume (I have no idea how realistic that is). Two cubic feet of water weighs about 125 lb. So the floatation needed to offset the engine weight is 500 - 125, or 375 lb. Divide that by 62, and you get about 6 -- that is, you'd need about 6 cubic feet of flotation (assuming that flotation weighed nothing at all -- close enough, for a closed-cell foam) to offset the weight of the engine.

So if you can roughly estimate (a) the weight of all the non-wood bits, and (b) the volume they occupy (as they corrode and seize and turn to mush...), you can then estimate what volume of foam you'd need...and see whether it's realistic to seal up/fill with foam that much space.