Glassed or bolted/screwed?

[ebb]

roythomas, Let's see... if the deck down in the cabin is a single layer from the mast to
the companionway -- without a buildup -- as it is in the Ariel -- it is 3/4" fir plywood
that is tabbed onto the hull with strips of fiberglass mat, cloth or roving. If you see
indications of mechanical screws or furniture like construction than it may have been
added by the DFO. Dreaded Former Owner.

Since the cabin deck bears on the hull, there is no opportunity for mechanical fasteners.
The deck may have cross pieces, separating the bilge into compartments. Cross pieces
that would act as support. They may have a cleat to which the cross piece, assuming
it's plywood, is attached. There you will find screws. The furniture in the cabin, if you
look inside it, probably is framed with cleats. A shelf will probably be held in a cabinet
with a couple cleats* on either side of the suspended shelf. Common construction.
*Cleat is a woodworker's term for projecting strips in casework to support panels and
shelving. Versus the mariner's cleat which is a projecting device for attaching line.

There is no way of knowing what you got there without a photo. DFO could have
changed everything with his own constructions.

If you want to remove the rotted wood, cut out the wood with a short blade, keeping
away from the hull. Once you can see what you got, you can use the oscillating tool
to pare back the remaining wood upto the plastic tabbing (the build-out that glued the
plywood down.) There probably is no tabbing under the plywood deck, making it easy
to guide your dogleg blade, up along the hull from the bilge, to cut the frozen snot
away. If you are able, first make a stiff white paper pattern of what you are removing,
before you dig in, so that you can cut the replacement and chamfer it into where it
originally was. After you've removed the offending plywood and the tabbing, Before
you start any grinding or smoothing, it's a good idea to solvent clean the area first.
So that you're not creating mini grooves to collect oil, and who knows what other
gunge, ground into the hull surface.
Once you've got the new piece to fit, cover both sides and all edges with epoxy.
Let it set, then tab it into place with thickened epoxy. Imco.
(least lethal solvent: 91% isopropyl alcohol -- from drugstore.)
You want a single level, no obstruction, 'deck' in the cabin that takes water directly
and straight to the bilge, where it gets pumped out. Never leave water in the bilge.

Polyester hulls absorb water, constant bilge water helps with that, and water captured
in the encapsulated ballast add to the weight of the boat. Over time boot-tops rise.
If the DFO left water in the bilge under the cockpit, and then changed the WL...
can't get a handle on that!
Sounds like you have an OB motor well, maybe DFO had a short shaft OB and had
to weigh the stern down?? Don't want to go there either! Motor well should be well
above the waterline, otherwise it becomes a scoop. Ariel & Commander drawings
in the Manual are not clear, but seem to show the lower edge of the well about
5" above the WL.

Look around the Forum here. There are dozens of Commanders worthy of every
page and every post. Gorgeous restorations and upgrades. There may be clues to
find and ways to approach your problem. There must be a photo or two in their
pages you can refer us to.

If you are new to plastic classics and 2-part epoxy, the only way is to start, and
get your little ship fixed up! Why not look over what other Commander guys
have pulled off!
(ebb's extremely opinionated and probably the wrong nut to offer advice for the
Commander...)