Dave:

Bulkhead replacement isn't that tough, as long as you are organized from the work.

Agreed.
First, the boat must be properly stabilized so removal of the old bulkhead will not end up changing the shape of the hull.

In an FRP boat, a bulkhead **DOES NOT** serve as a means to hold hull shape... The hull is molded and the major item in holding the molded shape is the *deck*, by holding the upper edges of the hull in its molded form.
In wood (with the exception of "cold molded") and metal boats the bulkhead definitely is used as the medium over which the hull is shaped, but not FRP. The old bulkhead was just "tabbed" to the hull with one or more layers of mat and cloth.
Make a note of this statement Fred, because you contradict yourself later.

Use a grinder with a saw blade to remove. Duplicate the old bulkhead out of new plywood. Rough an area 4" from the of the plywood where it will be bonded to hull. ( use rough sanding disk) Mask the rest of the ply to avoid getting resin on it.

Grind the Hull for 6" on either side of the bulkhead line just to remove old tabs, paint and to rough up surface, don't get carried away. Hint: keep a shop-> vac on deck with the hose below deck to collect all grindings. The hull must be clean!!!!

All good stuff.

Place the new bulkhead in position and use a small batch of resin and strips of glass in a few locations, just to get it positioned. let this kick off.

Yup.
Next use a fairing compound ( I use West Microlight ) and make a putty/paste. Apply this in the joint between hull/ deck and new bulkhead. Use old toilet paper rolls as shapers to get a consistent radius. > let this kick., then do a light sand/smothing > operation as you will never get it perfect ( It also > tends to sag )

Error #1... Microlight is, as you say, a **fairing** compound and is not for any other use. It has absolute minimal strength... It is meant to be used as a skimming compound only (one of the reasons for its "sagging" properties).

Error #2... A bulkhead in an FRP boat is **NEVER** fully bonded to the hull. FRP hulls flex much more than other building mediums and the bond between bulkheads and hull must in itself be flexible to prevent "hard spots" from forming in the hull. Go back to your earlier statement about original tabbing... Did the original have a filler between the bulkhead and the hull???? No way Jose !!!!! So why use it now???

In a subsequent message you wrote:
I would not recommend a rubber strip.. The fairing compound and glass tape help spread the load. A rubber joint would allow the bulkhead to move, and eventually the glass tape would fail from the motion.

As I said, **wrong wrong wrong**... There is meant to be movement between the bulkhead and the hull... You would be amazed at just how flexible a glass tabbed joint is... Of all the older boats I've seen/worked on, the only failure in a bulkhead tabbed joint has been the bond failure between the glass tabbing and the wood bulkhead, and this is a common fault (another problem with using polyester, it doesn't reliably adhere to wood).
The one *huge* difference between epoxy formulated for the marine industry and other epoxies is that the marine formulation is **flexible**, compared to the others.
Hard spots are formed when the bulkhead is pulled against the hull, often the result of a bad bulkhead fit and/or a bad job of fairing compound. This combined with a hot batch of resin and laying on to much glass at once and the bulkhead is forced against the hull as this cure.
Again you contradict yourself.. Initially you are saying to bond the bulkhead to the hull, now you are saying (correctly I might add) that hard spot in the hull are caused where the bulkhead is in contact with the hull.

As for "the bulkhead is forced against the hull as this cure".... Pure, unadulterated, gumph...
Multiple, wet-on-wet, layers do not shrink during cure any more than a single layer does (and that is zilch).

If you want to prevent sagging of the glass, use a piece of foam between the bulkhead and hull... Form this to a fillet shape, and glass over that. The reason for a fillet shape is that glass does not like to form a sharp angle and, even if you can get it to do so, a sharp angle is very weak structurally.
But again, if you use glass tape you can easily apply it to form a natural curved transition between the bulkhead and hull.

Next set up a wet-out table somewhere in the cabin for presoaking the bonding strips.
Great idea, as long as "pre-soaking" doesn't mean excessive saturation... You only need sufficient resin to turn the glass material clear... Any more is excessive and just serves to weaken the overall structure.

I have used a variety of materials here, everything from mat and cloth to the more convenient roll materials available from some of the suppliers. The very best material to use for tabbing is one of the many weight/width combinations of glass tape... The selvage edge allows you easy placement and results in a neat finish.
It is also much easier to apply multiple layers, wet-on-wet, without messing up the prior layers. BTW, additional layers should *overlap* the prior layers...

I have used both conventional polyester laminating resins and West epoxy. Prefer epoxy as it is supposed to have better secondary bond strength, and is easier to live with in enclosed area.

Anyone who uses other than epoxy is just wasting their time/money... It is a well documented fact that Polyester resin does not reliably adhere to old polyester, no matter how fastidious you are in preparations.

Use "Peelply" over the lamination after you lay the glass down. Peelply is a great product, it keeps you from mushing the glass around, and after the resin kicks it peels up to give you a near perfect finish. This is a waste of money... If the glass has been correctly "wet-out" and the hull/bulkhead surfaces have been pre-coated, the tape goes on "licketty-split"... No "mushing" is required... If you want to fill the weave of the glass further, you just apply another coat of epoxy once the initial coat has set-up.

"Peel Ply"'s main usage is to prevent an FRP product from adhering to a mold/form, or in the technique of "vacuum bagging".. Certainly some use it to provide a somewhat smooth final finish, but with tabbing this is overkill.

BTW, a wonderful substitute for "peel ply" is Nylon Taffeta.... Much lower in cost and equally as effective... Another good source, if you only want a small amount, is the nylon linings in dress/sports coats... I often buy a coat, or two, at the local thrift for a couple of bucks, tear the lining out and throw the rest away.
Use additional Microlight to create an easy sand surface over the glass work. Sand and paint.

If you are going to do this, the peel ply is positively overkill. For your safety use a respirator, and gloves when working with the goo, it's not good for you.
Certainly wear gloves to prevent "epoxy sensitivity", but a respirator is not need with epoxy... IT HAS NO VOCs.

Keep plenty of rags and acetone on hand to help clean up.
Cleanup is even easier, and less dangerous, with white vinegar.
Cover everything before you get started.

On Other Issues:

2. I don't care for fabric materials glued to the hull or overhead. Once wet they tend to stay wet. That all depends on what you use... I use a 100% synthetic high quality Indoor-Outdoor ($6.00 a yard) carpet that is guaranteed not to propogate mold/mildew or any of those nasty critters...
In tests I've done, water drains from it in a couple of minutes, leaving the material totally dry. This is not "fake grass", it is a good looking short-nap carpet similar, in appearance, to what a lot of you probably have in your homes. It is a great sound insulator and certainly gives a cozy feeling to the below decks.

Look for a vinyl textured wall paper. Have seen this done on several old Cals and it looks quite nice. It can also be wiped down.

How long does it last though.
BC