More H37C constuction questions.

[Ed Schenck]

The thread regarding the lack of coring in the H37C prompts this followup. Is it possible to describe the exact build process of our Cherubini Hunters? I have been to the factory to see the newer boats built and have a rough idea of the process. And there use to be a link to a Beneteau site where there were lots of detailed pictures of the build. But what about our older boats when f/g was still fairly new and they were overbuilt.

I understand the hull build. And then there is the inner liner and the furniture built onto that. But I am real fuzzy on how the top and headliner go together. Isn't the bottom layer of the sidedecks part of the inner liner. Then the plywood with some glass and epoxy and then the top over that? So we have three layers under the toerail, the hull flange, the inner liner, and the top?

I think it might be useful for Jim's "history" project if we could get the actual detail of the build process in there. For example we know the wiring for the lights runs inside the headliner(dumb). How do they do that?

 

[Ed A]

ED,

The hull gets laminated first.
The inner liner for the cabin ares floor ect is stet up on cradeles so both sides can be accesed, any thur hulls stringers ect that bond to the hull are installed and cabnetry that can be installed on the liner is put on. wire runs plumbing etc is istalled on the back of the liner or on the hull as appropriate.

The deck in the mold is worked on to add backing plates and wood blocks are attached usually glassed to the deck. sometimes wet out with resin by spray or roll application.

The upper liner is still in the mold to keep it stiff while similar work is done on the top side of the upper liner. light wiring ect is done wires are pulled for varous items.

Depending on the boat the keel may be installed from the inside, ie lowered in. or if hung on the outside and bolted up.

The floor liner gets glassed into the hull forming sole and slots or holes for access where they are needed. Holes are cut for access.

The liner gets pulled from the mold flipped over and droped into the hull. then is attached to the hull with glass and resin.

machinery is install in the aft sections. the hull is setup into a formed cradle, the glass is pretty green so it has to be supported in key areas to prevent distortion

The shaft tube, shaft strut, shaft, engine, on most models can go in now, there is no deck to be in the way so its pretty easy. This accounts for why is is so damn hard to take one out later but thats another episode.

at that point in most plants the bulkheads shower components , all plumbing and electrical that goes under the deck can be installed including the switch panels, pumps, breakers, waterheaters, hoses, fuel and water tanks, etc.

The deck meanwhile is pulled out of the mold and the deck hardware can be installed on a lot of models, this explains why you need to cut a hole to remove bolts on things like winches. On a lot of boats they are put on before the deck even goes on the boat.

Mean while out in the wood mill all wooden parts are cut out for assembly,
cabnet doors, cabnet fronts, counter tops, drawers, stairs, drop in lids, teak and holley soles, all trim pieces moulding tables bulkheads are cut out.

They then are assembled in as complete sub-assemblies as possible. Counter goes on the cabnets, bulkhead and all trim go to the boat for installation.
Components like the nav station and cabnets come to the boat with fronts done and no backs. they are fit in place, sometimes glassed in to the liner or hull screwed in. the deck is then lifted over the boat and lowered in place. several people guide the deck and liner down to the boat to match all the components made by the cabnet makers some again are glassed to the liner some screwed and some just fit in to clear the liner with trim molding attached. the deck gets attached to the hull and is bolted down in a bet of someting like 52OO. the often the rail is bolted down in this step.

Deck fittings rails tracks and all the deck hardware are already in place.
lets throw on some bow and stern rails, lights ect. And wire it up and you got a pretty new boat.

so thats about how it goes for most boats in this era including the Hunters Catalina, Morgan, Irwin, Island Packet, Columbia, Pearsons, and lots of others.

The process varies a lot from model to model but generally y ou will find that the industry did not know how strong this fiberglass stuff was or how long it would last. The weak points were always the wood from rot or the steel from rust. As materials have changed so have the processes.

It was a dangerous place to work, lots of ways to hurt yourself or others.

It was brutally competetive. All tried to build them cheaper and sell them for more. Few made pretty goood money. Most did not.

 

[Ed Schenck]

Thanks Ed, really glad to see your response this morning. You must have been up late, this and the "hollow" post took a lot of typing.

I followed your build description pretty well. I am still not clear on the "upper liner" to deck connection. So the deck is upside down when the side deck coring(plywood) is added? And the hardware like cabin travelers and winches is installed. But what about the hatches? How are the deck and upper liner attached?

I wish I could draw on here so I could get a picture of what the upper liner looks like.

 

[Ed A]

the deck is still in its mold when the stiffining is added, no reason to pull it yet. on some molds the area where the hatch is to be is laminated over and cut out. I would bet the hatch areas are cut out of the deck part after the part is pulled form the mold. This provides the oportunity to finish the joints between liner and deck when they are assembled, so i would thing the process used on these boats would be to put in the wood blocks in wet resin then spray them resin and drop on the liner. Some builders used a putty like resin mixture to fill some of the voids but they usually are not completly filled. Kinda sucks doesnt it. but it works well, and is strong,

When foam cores are used other techniques are used. today they can vacum bag the foam to the deck. But it was too expensive and the technology was not avalible in most plants.

This method is most visible in the boat by looking up at the bolts in the rail, you can see where the liner ends before it hits the hull. It is a bit of a puzzle to get it all to fit. sometimes cabinets that go up from sole to liner are put in last covering up some of the access to these hull deck joints.

hope that all this helps. There are a lot of ways to do it all but i know this was the way most did it.

There are lots of benifits to doing it this way. In production you could have people in the carpenters installing, the wood shop building, the mep (mechanical electrical and plumbing) guys all working in different places on the same boat. This made it easy to have 20 or 30 guys doing subassemblies at the same time, and most of them were not in the boat.
many who contribute to the build dont even work inside the hull at all.

In larger plants you could be building several boats at one time.
Specialised crews got really good at there tasks, less mistakes, less problems.

 

[Ed Schenck]

So the deck comes out of the mold with all of the plywood coring attached. Then the "upper liner", or what I think of as the headliner, is ready to epoxy into that deck. And the wiring is already run to the holes for the overhead lights? In conduits or just taped there?

That upper liner you say does not go all the way to the toerails? So it is not part of the deck to hull joint? It does obviously extend through the v-berth and through the quarterberth. But it does not go under the bridgedeck nor the bow, right? Just hard to visualize what the liner looks like before being "glued" to the deck. Especially the wiring.

 

[David in Sandusky]

On our '77 h27, the deck "sandwich" is glass, wood, glass. The two glass layers come together where the deck is married to the hull with no wood in between. The liner is a separate glass component that is not bonded to the deck, but attached at selected points. It ends with a downward lip about 3-4 inches from the deck/hull joint, giving access to the nuts on the bolts through the joint.

To me, that implies that the liner would be married to the cabin first, carrying the wiring, lights, and other components. Then the deck would be mounted on top of the liner. The two are compressed flush where they pass over a bulkhead, but I have seen no sign of an attachment even there.

 

[Ed A]

good questions. If you will remember,
If you lie on your back in the v-berth, or in the aft cabin and look up, you see the deck joint. If you put your hand up there you can feel the head liner and the hull and in some places you can feel a space in between. In the main cabin you can look up with your head in the cabinet, (hard but possible) and see the deck joint bolts and feel the same space.

If you look closely at the hatch openings you will see the liner is glassed to the deck to make a nice flange. This also makes the parts one, liner and deck. There are other places that do the same thing thru out the deck assembley. The wood stiffens the deck and the liner for that matter insuring the deck wont oil can when you walk on it.

The above post is correct in that some points, glass joints attach the deck to the liner. By installing the head liner to the deck while it is still on the mold the finish is down on the deck and the underside is up. This allows you to put the wood in or in some brands of boats the foam or balsa, while nature helps you keep it in place and you dont have resin rulling down on you from overhead. By the way the decks and liner attachment is almost never epoxy, Most boats were built with all polyester or vinylester resins. NOT epoxy. (to expensive).

Then lowering the liner over the deck and setting it in place allow easy installation while your not upside down in the boat. Gravity works with you not against you.

The deck installation procedure requires that the liner be attached to the deck! otherwise when you pick up the deck and liner with a hoist and drop it all in place they would separate. You cant put the headliner in after the boat is decked.
The liner plays an importat role too. It is not designed to be just a ceiling. The liner also provides molded in shapes to stiffen everything up, and slots, or flanges to screw against, to install cabinets or bulkheads, all kinds of shaping in the liner adds to the support and stiffness of the entire structure.

this works by creating stiff shapes where you need them. For example you can glass a paper tube to a flat pannel to stiffen up a pannel or even the hull. The paper tube gives no support but just serves as a mold for the glass to make a stiff rib on the back of the pannel. The headliner often does this stiffening in the same way, as does the hull inner liner, both are glassed into place to be a part of one big unit.

 

[Ed Schenck]

Great explanation Ed. Now I've got it. So David is correct about "The liner is a separate glass component that is not bonded to the deck, but attached at selected points." But incorrect when he writes "To me, that implies that the liner would be married to the cabin first, carrying the wiring, lights, and other components. Then the deck would be mounted on top of the liner." That did not seem plausible to me.

Thanks for taking the time.

 

[Jim Legere]

I was going to say that...

I was going to say what Ed A and David said...I'm glad they said it for me! Anyone who has replaced the original Gray ports will recall that there was glass / wood (or mush!) / glass and then the headliner. Also true if you ever replaced the deck drains thru hulls in the q-berth and the aft galley cupboard. Hunter didn't skimp on using materials in these boats. Probably one reason they are so heavy. To say that Hunter cheaped out beacuse there are some voids in the deck sandwich (another thread) shows ignorance of how the boats were built. Thanks, Ed A for taking time to explain the construction of our boats.

 

[David in Sandusky]

Thanks for the correction, Ed A

I enjoy knowing how they went together, and it could help when we maintain our boats.

 

[Ed A]

Glad to contribute a bit. I wish i still had mine!

thank you.

 

[DianaOfBurlington]

from the professional boatbuilder

Most of what people say here is correct. Early (1972-1980) Hunters were built with NO hull core. This is always better. The only reason for core is to add thickness and reduce weight and cost. No production Hunter of this era had less than about 35% of its total displacement in ballast weight (mine is over 40%!), so weight savings in the rest of the boat was not an issue. Personally I would eschew cored hulls in all but high-perf applications. It is actually more complex and costs more in labor (though the core materials are almost always cheaper than the polyester resin and cloth for an equivalent thickness). Nowadays vinylester-resin lay-ups return about another 10% weight savings and add complete water impermeability, so even today a cored hull is at best a gimmick.

Decks are another matter, because you want to save weight at such an elevation above the waterline for stability's sake alone. In most production situations the deck is finished as far as possible before being turned over to be installed on the hull. In high-volume situations the deck should be removed from the mold pronto to get another deck going into a mold. Hunter used to build one boat in each of 5 production lines per day. Nowadays someone like Catalina could probably shoot two or three decks a day.

All electrical wiring, mounting pads for deck hardware, the soft headliner, etc., gets installed with the deck upside-down. The idea in production is to advance each stage as far as possible before initiating another stage. As owners we all know how hard it is to do restoration, repair and remodeling over our heads-- did you think the builders would do that by choice?

Very few modern boatbuilders would use a plywood core. Plywood is a major sponge for water, it is heavy, it is expensive, and it needs to be treated before installation (to be done right). The foam used as cores is (supposedly) closed-cell and will not soak up water. (We've all seen how well that claim holds up.) In the '70s the favorite solution was edge-grained balsa, by nature a water sponge, except that balsa is used because it is light, cheap (imported) and floats when waterlogged. This, too, rots when allowed to stay wet. (I have written on how to fix this many times.)

At Cherubini my cousin Dave made a new deck mold for the C44 in which he included SOLID 'glass bedding blocks for major deck hardware. These require no additional backing plates. I would suspect nowadays most builders do something similar (but we never had a deck mold before and so his 'glass backing plates are a whopping new thing to me).

My 1974 boat has a flange molded on the hull about 3-4" wide, on which the deck sits. This is how my dad wanted it and is the preferred method for fastening the two parts together. Other methods are the 'shoebox method' (deck has sides that fit down over top edge of hull-- MacGregor and others do this) and the 'kissy face method' (both deck and hull flare out like frog lips and the two flared flanges are mated and covered with a metal molding-- common in cheap motorboats). With the metal toerail on my boat, the deck/flanged hull/toerail combination is absolutely unbeatable-- quick to assemble, cheap, and phenomenally strong; and with the toerail adequately bedded in 5200, it won't even leak.

I don't have experience with assembling full-interior molded liners and voted against them when I had any influence on Hunter. (I am pretty sure my dad never designed one.) I find them heavy, complicated, and prone to causing nightmares for maintenance down the line. Of course both the hull and deck liners have to go in before assembly of the hull and deck-- but I see no reason to fasten them together. Leaving an actual gap between the edge of the deck (head-) liner and the interior liner pan allows for the inevitable moisture/water to seep out. Also, unless the space between a liner and the hull or deck were filled completely with foam, it would be hard to through-bolt any bit of hardware to either side of it. At least if it were foam you could use the 'spade bitt method' (drill oversize and fill the local void with epoxy before drilling bolt holes). A total (air) gap would be, again, a nearly-unsolvable nightmare for this. Liners with air gaps also lend a rumble from vibrations that sounds like you're in living in Alex VanHalen's kick drum.

Filling this void with plywood would be heavy, expensive, and pointless; so if you're seeing plywood in a few cut-outs it may only be in very local areas (round the flange for example, or under a mast step). Even then it would not be reliable.

Owners of early H25s will be aware that the deck under the mast step is cored with foam; but the mast step sits on a fiberglass plate integral with the hatch hood and under that is plywood. (I cut off my hatch hood short, filled the foam with epoxy and added a G-10 plate on the deck for it = better.)

In the case of partial hull pans, such as in the C44, it is possible to fit all the associated equipment, engine, toilet, whatever, and so on before picking the whole thing up and installing it. But, again, full-molded pans can lead to nightmares. Cheap motorboats are made entirely in sections-- to the point where they will often have a beautiful molded cockpit pan installed over top of a fuel tank, through-hulls, fuel hoses, wiring, etc, that will never be accessible again without a pneumatic hacksaw. ('The boatbuilder is not always your friend,' I used to say to my West Marine customers.)

So I am skeptical of the use of molded interior liners when it leads to builders achieving too high a level of assembly before permanently attaching to the hull assembly. If you've ever had an inaccessible fixture below one (H37 owners, you know what I mean) you'll know why this is not the way to go. Apparently even Hunter fell prey to the 'quickly-done is quickly-paid' mentality by about 1978 as well

More and more each day I am glad my 1974 boat is essentially 'stick-built' after all.

 

[Blaise]

My 1979 37c has a partial liner that goes from the bilge to just above the settees, and forward to include the shower and v berth. The rest is stick built. That is why our boats are so strong. If you have ever been in a 20 year old Catalina or a post Cherubini hunter offshore you will notice an immediate difference. The full liners come loose and rub against the hull in heavy seas. They are basically grinding themselves to powder. By the way, all toerail bolts are accessible on my boat. I did go to the factory before I bought my boat. Back then Hunter subbed out their glass cutting. All the fiberglass arrived pre-cut in giant brown paper wrapped bales. They would be weighed prior to being opened. If they weren't with in 10 pounds of what they should be they were sent back to the sub for them to figure out what was missing. Very efficient. The keels were put on last to keep the boats as low as possible to make them easy to work on. The decks were cored with plywood, but they were 6" squares to limit water intrusion.

 

[rardiH36]

Treated Plywood Core

... plywood core.... and it needs to be treated before installation (to be done right).

I cerrtainly encountered this when I removed the top skin of the cockpit sole (on my 1980 Cherubini Hunter 36) because water instrusion had caused delamination and a repair was needed. The pedestal and pedestal guard had significant movement even with the thru-bolts cinched tight. Upon prying the top skin off, I found that the actual wood fibers were in great shape with no rot whatsoever, and the wood was still firmly adhered to the upper/lower fiberglass skins. The color of the wood was greenish, and since no rot, I presumed the plywood was pressure treated. The failure was that the plywood layers of the 6" squares had delaminated at their glue interfaces. Had I known this before I started the repair project, I think I would have instead drilled many large holes in the top skin, let the core dry out then and then would have flooded the core through the holes with thinned West Systems epoxy. Then add some vibration to encourage the epoxy to penetrate into the delaminated layers. Finally fair the holes with Colloidal Silica thickened epoxy and stipple to mimick the rest of the cockpit sole surface. Would have been a lot easier than taking the top skin off, chisling off the amazing toughly adhered wood, layering in new wood, pouring in lots of epoxy and reapplying the top skin. (However, this repair method has been a success.)

Everywhere I've delved on my boat, the construction has been robust. I have found no evidence of any area being beefed up by PO's with added braces or fiberglass. Darn good for a 30 year old vessel.

 

[rardiH36]

Toe Rail Joint

... By the way, all toerail bolts are accessible on my boat...

I recognize this is a Cherubini 37 thread, but in case some H36 Cherubini owners are lurking as I am, its the same on the my 1980 Cherubini H36. All the bolts are accessable (except for a couple). When I bought my boat 3.5 years ago, I found some water was entering during rain and also when sailing with waves sometimes over the rail. Solution was to clamp the toe rail bolt heads from the deck side with vice grips wedged against the toe rail. Then using a deep socket, various socket extension fittings, and a universal swivel attachment, tighten the nuts from underneath. The wedged vice grips kept the bolt itself from turning and breaking the caulk seal. (Would have been easier with a second person on deck with a phillips head screw driver to prevent the bolt from turning. But I didn't have a second person that day.) After tightening, the water leaks have stopped completely for the past three years. Interestingly even after 30 years since construction, still pliable caulk was forced out from under the toe rail in places. I think it was probably butyl tape.

Another benefit of tightening the toe rail bolts, and hence also the deck to hull joint: I no longer have various cracking noises when I cinch in the jib sheets tight. (Jib sheets are led through snap blocks on the toe rail)

 

[rardiH36]

Re: from the professional boatbuilder

I've been following this thread with great interest. My thanks to all the knowledgeable contributers.

 

[Ed Schenck]

Blaise, how do you reach the toerail bolts that are next to the anchor locker? There are others that I consider inaccesible like behind the nav station and over the galley.

 

[DianaOfBurlington]

re: nardi

rardi mentions the number-one reason why cockpit soles ever rot-- the working of the pedestal back and forth from normal use against its own bolts. All of this nearby plywood in the core should be epoxy-treated. Accept no substitutes.

(I strongly doubt it was pressure-treated plywood, which would have been far more expensive-- if even it were available back then-- than builder-grade or even marine plywood. In any case it should NOT be pressure-treated at all, since the pressure-treating process expends the wood's ability to adequately soak up epoxy.)

There is a very good case for removing the pedestal every 5-6 years or so to ensure that it is rebedded properly. (Also all steering cables and/or connections should be inspected and possibly replaced at such an interval as well. Remember they are 7x7 and not the more rugged 1x19; and they spend their lives bending repeatedly over tight metal sheaves and, thus, fraying and fatiguing.)

My boat has a tiller-- and the cockpit sole (which is balsa, not plywood cored) is the one spot of the whole deck that has never been violated and thus has never shown any evidence of rot or delamination. I thought of putting a padeye there for the lifeline harness tethers, but decided against it and it will go on the cockpit pan side.

I have decided on replacing all my toerail bolts' washers, as they are apparently brass (not even bronze) and perfectly green and pretty corroded as well. I will use large (probably 1") fender washers. The existing 5200 is sound, which is why I bought this boat in particular; and it does not leak in rain at all. But while I have most of the interior out I might as well get at them when they are easiest.

nardi also illustrates the value of having capable crew when doing maintenance as well as when sailing. I have two princesses (I mean daughters-- same thing) and therefore I do all work on my boat solo. I invested in a very cheap Harbor Freight vice-grip whom I call The Red Chinaman (because in Cherubini Boat Works tradition all tools manage to name themselves immediately or eventually). The Red Chinaman has proved himself an invaluable help by being my 'other hands' in plenty of jobs. But The Red Chinaman does not take much initiative; so if there were only a way to magically apparate through the skin of the hull so I didn't have to leap over the rail and dive below every time I moved on to the next bolt....

 

[rardiH36]

Blaise, how do you reach the toerail bolts that are next to the anchor locker? There are others that I consider inaccesible like behind the nav station and over the galley.

\
Ed:

Pending Blaise's response, on the H36, the anchor locker well extends downward from the deck right up there at the narrow part of the bow. Probably much the same on a 37C. From the inside, there is only a small gap between it and the interior sloping sides of the hull. Through this gap is access to the toe rail bolt nuts. This is where I found that the socket set extensions and the universal swivel attachment were necessary. I think that when I did my project I needed to piggy back both a one foot and a six inch extension to get all the way up. Also to prevent the swivel attachment from collapsing over, I wrapped some electrician's tape around it. Only enough to give it some stability but still allowing it to flex. The other issue with working in this area is that you've got to employee your contortionist proclivities to get yourself wedged up into the most restrictive part of the fore-peak. I'm not exactly a contorsionist, but at 6'4", my long arms helped.

 

[Blaise]

Ed,
On my boat the toerail bolts were accessed at the bow by a skinny friend and socket extensions. At the galley you have to unscrew some furniture. Neither difficult. By the way, Hunter initially sealed the hull/deck joint with a one inch thick bead of 3m 5200 then bolted the deck on. In 1980 they switched to butyl tape which later proved to be a mistake.