FYI, Soundown has two types of insulation. The foam which has a life expectancy of 10 years then turns to an oily rubber mess and they also have a Fiberglass type insulation which is fire proof and CG certified. The cost isn't much difference. We used the CG certified panels. The job wasn't easy but we do like it. Also on the standard WS 42 dinettes there is a space behind the port dinette seat  and we used standard home fiberglass insulating battens there to further insulate the heat from the engine room warming the backs of anyone using that space.

As an aside. When we inspected, cleaned and repainted (fuel only) our tanks I put back the flooring and the cabinetry with caulking and NO Epoxy. Ready for another tear out should the need arise. Also where there was glueing like on the floor I put did not glue down the flooring over the subflooring edges. And to help identify those edge pieces I used larger bungs and varnished them in in lieu of glueing them in. Also the floor is sealed with Ultimate Sole varnish (which is basically Gym floor varnish). For those that care.

Ciao

George, your questions are the same ones I wrestled with prior to making the decisions I did fr Harmony.  I'll address each in order.

Fuel & Water Tanks - My foray into this are was inspired by 2 things, dry rotted galley and a survey that stated I had a black steel fuel tank that leaked.  Anyway, since I had to gut the galley and dinette area anyway,  I removed every thing or had to because of extensive rot.  I removed everything including the decking in the galley dinette area.  I found that instead of a steel tank, the prior owner had removed the 3 steel tanks and replaced them with 1 polyethylene tank of 105 gallons mounded athwartships.  Now, the fuel tank area was designed to hold 3 separate tanks totaling 200 gallons, and I would have preferred that arrangement.  However, the cost of fabricating 3 aluminum tanks was too much for the budget.

The water tanks were just forward of the fuel tank(s) and were 3 separate stainless steel units.  The port and starboard tanks were 50 gallons each and the center was 100 gallons.  While the 18 gauge steel look great for the age, the baffles had ripped holes in the top of the tanks.  I used the old tanks as templates for the new 72 gauge 316 stainless steel tanks. 

Once I had the decking up, the removal and replacement was fairly straight forward.  The old tanks were light enough for me to lift out of the boat. However, the new tanks were much heavier and I needed a crane! 

Since the floor members were in great shape with the exception of being somewhat saturated with diesel from leaks from the old steel tanks, I just replaced the decking.  I did not glue any of the decking panels down and just used new stainless screws into beefed up supports.  Currently, I am fabricating new galley / dinette furniture.

Yanmar 4JH4-HTE - I chose Yanmar because of its reputation and the proximity of service.  The size was recommended in order to have a "reserve" of power to deal with currents and seas.  Other than a non-Yanmar option, which didn't appeal to me, I had the option of a 75HP Yanmar. In the end, I felt the extra $1500 or so was a good deal for extra heft.

Soundown Insulation - Both products are good and relatively easy to apply.  The company is responsive, too.  I fabricated mahogany studs between which I put the Soundown.  I then "paneled" the fore and aft engine room bulkheads with 3/4" merranti plywood painted white.  Upon these panels I am mounting equipment, wiring, plumbing, and etc.

   Doug                                                  

We replaced all 6 tanks on Abake (W42).  Custom tanks from a shop in NJ.  We liked the idea of having tanks that fit the space and had baffles.  Off the shelf poly tanks do not.  Obviously a trade off that is more $$, effort and time.  You're only doing this once, right?  Abake came with a Ford Lehman 80 HP.  Seems to be more than enough power.  An engine in that HP range (70-85) should do nicely.
Cheers,
Mike

Marine Liquidators in Fort Pierce, Florida has a huge selection of poly tanks salvaged from hurricane damaged boats, maybe even salvaged Westsails.   

George, I'll try to address most of your questions.  I have used Merranti Plywood, as well as traditional marine plywood in several application on Harmony.  With the Merranti being more expensive and a tad better looking, I have used it for bulkhead replacements.

Regarding your question on attaching bulkheads to the hull, I do not attach the bulkhead directly to the hull.  Even though the hull is a very stout solid glass, and won't show deflection like a foam cored hull, I put a base down before glassing the bulkhead in.  While one could use an airex like foam, I have used either kerfed 3/4" Merranti or 3/4" marine plywood.  The kerfing allows the plywood to mold to the curvature of the hull.

The kerfed board(s) are roughly 3" - 4" at the base with a 30 degree bevel on the side.  I bond these to the hull and glass them in place.  Once cured, I trace the curvature onto the bulkhead panel, cut and fit, then glass the bulkhead onto the kerfed base.  I do apply a fillet of thickened epoxy in order to give the tabbing a stronger structure.  By having the kerfed base extend an inch or so beyond the bulkhead provides me with an attachment point for ceiling strips.

Relative to the ports in the galley/dinette area, Harmony has an opening center port.  It is a very large opening port, and, when we took ownership, the gaskets were leaking like sieves.  I purchased gasket material from Bud, and fixed the leaking problem.  Our ports are tempered glass.  The other large ports show no signs of leakage.  We are glad to have the opening port, even though it will have to be watched for leakage.

Most of our water leakage and dry rot damage was sourced from (1) poorly bedded deck fills; (2) leaking galley ports; and (3) failure of the caulking on the cap rail. 

On tankage, we now have new SS water tanks.  Had I had the budget, I would have removed the poly tank and installed 3 aluminum fuel tanks.  However, this move would have been to increase the fuel storage from 105 gallons to 200 gallons.  We are satisfied with the poly tank for fuel, as it has internal baffling to prevent major sloshing.  Given the way the floor was designed to house 3 water tanks and 3 fuel tanks, I would have preferred to have the increased capacity.  My blank canvas approach would have been SS for water and Aluminum for fuel.  However, I could have gone with baffled poly for fuel, as well.

I don't have any info on what Yanmar sets as warranty issues, but will check into it.

Doug