to foam or not to foam

I am the greenest of the green peas! I have been reading and learning an am now at the cross road... I am restoring an 86' nautique, and the floors are now on tap. Here is my dilemma, it seems as though there is about a 50/50 split here as to whether or not to re-foam the floor like factory or just replace and hollow the floor and use plywood. Is the hollow floor not "banging" in waves and will the foam not "refill" with moisture like the original. Which way is best?

it was very wet and very heavy. I took it all out, it probably weighed 3-400 lbs total!

i understand how to do it, either with or without the foam as either method is destinctly different. I guess I am looking to survey as many owners I can here who have done either one to see which seems to be the best.

Put new foam in. It needs to be there.

I am on the re-foam side of the aisle. I believe the foam has three usefull purposes:

1) Sound deadening.
2) Structural support against the hull oil canning.
3) Floatation in the event of mishap.

If you are going to put plywood over the foam, then use the low density stuff (recommended by me). If you are going to fiberglass directly over the foam, then use high density foam (not recommended by me as this method requires a great deal of fiberglass matt/cloth and resin).

If you go the foam route, do NOT try and place plywood or plastic over the foam as it expands, let it expand freely. If you try to keep it from expanding, it gets very dense and thus hard to shape, can bulge the bottom of the boat out and looses its bouyancy. The best method of trimming flat is to use grinders and long sanding blocks. Avoid the use of a saw as you will surely cut in a low spot.

OK, I'll be the contrarian. My '64 did not have foam from the Factory. It has plywood floors with CC markings so I can assume it's "Original".

The '72 was water logged underneath the 3/4" plywood which was also soaked and was "heavy" to say the least. I removed every bit of it and laid down plywood with no foam.

The '72 is no louder now than before.

I think the vibration others feel/hear is due to the way you align the shaft but won't get into this here since we had a lengthy post on that a while back.

Mine was saturated(wood and foam)and we opted not to refoam,it started out as a quik repair job and we eventially took the entire floor out ,front to back.What we found was poor quality glassing (from the factory)that was allowing moisture to sneak in from numerous unaccasable places.Something you may want to consider if you tear it all out, is the area forward of the skipole,it is a large void of wasted space that allowes water to slosh around,we rerouted cabling vents ect and now use the area for the battery comp,storage of tools,and an icebox that is accsesable from the drivers/observers seat.
Also we installed drain plugs for each side(thru the transome)access plates into the deck for inspection and vents to allow for expansion/contraction.

I was working alongside a qualified boat builder and the turnaround time from start to finish of the deck area alone was 12 solid days of nasty dirty work for both of us.The boat is no noisier as when it was full of waterlogged foam.

There are millions of boats out there without foam they are not unusably noisy. The hull in a correct craft is thick enough that it is not going to oil can without the foam, and all foam even the new stuff if exposed to water long enough will pick up some of the water.   
I am not against anyone adding foam if they want it for safety or a little more solid sound as they go accross the water, but it can be done without it. I am not using it on my rebuild, or any wood either...

I recently finished foaming on the 72 SN and did so for these reasons.
1. I already have the boat ready (stingers open with no floor)and might as well do it.
2. If I ever hit something in the water that puts a hole in the hull...it will not sink!
3. insullation for sound...more solid feeling.

My 2 cents worth...why not?

I had the floor in my 20 ft Southwind totally taken out as it was soft in several places, and the foam was full of water. They did not put the foam back in, just used solid wood instead of plywood(like it was originally) for the floor stringers.   It feels very solid and I don't hear any waves crashing on the hull. The boat is very quite.The guy that did mine put drain holes from each compartment so any water could drain to the center of the bilge. It stays dry everywhere.

If you have removed ALL foam..three 8 cubic ft foot kits...you won't use it all , 16 cf may not be enough...I barely got by with 16 cf , but I had to stuff some pool noodles under the bow area and faomed over them .
so...three kits or two plus noodles!

Stangs at it again, first it was frog butt shaft seals now pool noodles. The mans a creative genius.

I could'nt resist....but

Pool noodles...."what ever floats your boat"

Pun intended.....

When the floor in my 20ft Southwind was redone last year with out foam,we did put noodles in the two compartments beside the engine. This was for flotation if needed.

I keep laughing....But I'm sure alot of noodles would float a boat. The word " Noddle" used by a bunch of grown men is just funny to me