246 rebuild live from Delmarva!

[4shore]

Stupid question then. Does a water tight compartment then not have the same displacement as a foam filled cavity? Obviously the drawback here would be if it then became not water tight like you were saying.

I just cringe at the thought of clogging up the below decks drainage with foam hence the thought of putting in between the gunwales and the outer hull where drainage is less than an issue.

[gran398]

All the foam does is hold air... the same as a watertight compartment. Actually less, due to the displacement of air by the material (styrene) itself.

I'm with Dave, if you don't need it, you don't need it. Throw some foam block under the deck after the  routing is completed and call it good. Save that time, effort and money for other things....and trust me, there will be a TON of stuff to spend (or as my wife says, waste)  extra money on

[Georgie]

X3

Foam helps these boats only in two ways:

1) it provides a filler for the stringers which makes them stronger than they'd be if they were air filled.
2) it will provide an additional measure of safety and help prevent/slow the rate of sinking ONLY if the airloc of a compartment with the foam isbreached (b/c the closed cell foam prevents the entire chamber from filling with water, therefore preserving some of the buoyancy).

Under normal everyday operating conditions the fact that you do or do not have foam under your deck will NOT come into play, and as Scotty mentioned

All the foam does is hold air... the same as a watertight compartment. Actually less, due to the displacement of air by the material (styrene) itself.

it actually is quite a bit heavier than air even when not saturated.

You can achieve the same buoyancy assistance that foam provides by constructing a grid system of sealed compartments under the deck such that if your boat is broadsided and the starboard hull is breached, all of the compartments on the port side the at maintain their integrity will still be airtight and therefore buoyant.

In essence, the more foam in boat the lower it will sit in the water, but the safer it will be in an accident.  :eye:

[saltfly]

Well there is this, put as much flotation in as feasible. more life jackets then you need. Stored it out of the way places, add to the flotation. Then use it have fun and just don’t swamp in to find out if it works or not. :twisted:    

[4shore]

Hey saltfly. I may or may not get out there to work on the boat tomorrow but will definitely be out there Thursday and Friday if u are in the area

[dburr]

Stupid question then. Does a water tight compartment then not have the same displacement as a foam filled cavity?

No such thing here!!!

Displacement is the total volume of water that the 246 will displace at it's design waterline.  In that volume (hole in the water) is all the crap you have in the boat, the boat included..  It could be foam or beer, when you put an equal WEIGHT of each in the hull she will sink the same amount..

The displacement volume of an enclosed space does not change regardless of what is inside the space, the object with something in it will however will have a greater mass and sit lower in the water and ironically be less buoyant..  It makes a big difference how much lower it will sit based on the shape.

Hope this helps...

[Capt. Bob]

Buoyancy is based on the weight of the volume of the medium it displaces. In this case we are talking water (seawater I'm guessing) and designers have to take into account the density of the water. For the most part, a boat that floats in seawater will also float in fresh water. The same design hull will however ride lower in fresh water because of the variance in density between the two. Hull shape does not change and by design, will displace a given weight of fluid. Seawater is denser than fresh so the actual volume displaced changes but the weight remains constant. This is based on forces acting on the surface of the hull pushing it down (gravity) and compression of the water column pushing it up (pressure change at each end).

Hull design is therefore based not only on its weight but all the crap you place inside (as Dave stated). Thus the hull must displace more medium (in this case water) by weight than all your stuff in order to remain afloat. Altering its shape or adding more than its designed displacement weight and you and Davey Jones are shakin' hands.

Like so many things in science, it's a concept that for me, takes a leap of faith. Then again it could be Neptune's pinky under there holding it afloat.

Whatever it takes.

Good luck.

[wingtime]

If I remember correctly seawater weighs 64 lbs per cubic foot.   So if you take one cubic foot of something and it weighs less than 64lbs it will float in sea water.  For example a plastic one foot cube that weighs 30 lbs will float in sea water since it weighs less than the cubic foot of water is displaces....  in fact it will have 34 lbs of buoyancy.

[4shore]

Let's play"who has the most awesome wife ever???!!!!"

[dburr]

        !!!!!!!!

Wow, authorized the purchase and then works on it too...  

[RickK]

Hard to beat that  

[4shore]

What's the deal with the wood core? How far does this go?

[Callyb]

What's the deal with the wood core? How far does this go?

That sucks.  Sorry, I don't have an answer. I just feel your pain.

Is it wet?

[4shore]

Port side is dry starboard isn't. I'm not sure it is even structural. I think it may have been cored for I/O purposes

[RickK]

Port side is dry starboard isn't. I'm not sure it is even structural. I think it may have been cored for I/O purposes

Makes sense although that thin layer doesn't look like it would beef it up much.