chain plate tension

[Gary Ambrose]

We are new owners of a 1986 C34 #215 (as of mid August 04).  My wife and I had previously sailed  a C25 for the last 18 years and consistently cruised the Maine coast each summer with our three sons.

Yes, that  was a feat.  We now luxuriate in the room and stability of our  C34.  It is just terrific!

My question is, how much tension should be on the 5/8" chain plate bolts located behind the port and starboard settees?  I am assuming boat on the hard without mast up.

Many thanks for all the helpful information on the message board and the very thorough Owners Association web page.

[Ron Hill]

Gary : By C25 standards the tension on a C34 is going to be TIGHT.

My best advice to you would be to hire a rigger that's familiar with larger Catalina's.  Get yourself a tension gage (they aren't cheap-$50?) and have him give you a 1/2 hr of instruction.  That way you'll be set for the rest of the time that you own the boat.  The primary function of the tension gage is to get the opposing shrouds at the same tension.  Maybe the yard that splashes your new boat will help you with the initial tension.

The days of pulling on an outer shroud and seeing the mast bend - ARE OVER!!

[Gary Ambrose]

Thanks Ron for the reply...I am not looking for shroud tension.  Rather the chain plates as they pass through the deck are anchored inside the cabin behind the settees by 5/8" bolts to tabs secure to the hull.  They are the stainless rods that can be seen in the cabin.  It seems reasonable they should not be loose but the question is more how much torque to apply.  There really is no information in owners literature on these.  For now I have them firm, not loose, but not overly tight either.

Thanks.

Gary

[Stu Jackson]

Gary

There's no published "data" on torque for those rods.  When I re-bedded my chainplates the first time a few years ago, I disassembled the entire port shroud assembly in the cabin to see how it all worked.  There are simply two nuts on the threads at the bottom end of the rod behind the settee backs.  The second nut is a "lock" nut for the first nut.  Since these rods hold the chainplates down you want to make them snug.  It's very hard to over tighten them anyway, given the access.  I ended up buying a short handled one inch adjustable wrench to get back in there.  Keep them tight, definitely not flopping, just think again about how the whole system works.  Most people never touch 'em.

[Gary Ambrose]

Thank You Stu!  I would advise all to check the rod bolts for tension.  Most of mine were loose by a turn or two. But, most unsettling was the absence of four lock nuts out of six.  That means that over time and flex the rod bolts can become very loose.  In turn all mast effort is then carried by the deck.  Not a good idea.  We did remove and re-bed all the chain plates and while the system is adequate I am sure that induced flex there translates into water in the plywood laminate pretty easily.  Tension on the rod bolts will be essential in minimizing flex to the chain plate bedding.

Again, thanks for your helpful reply.

[Ron Hill]

Gary : The stainless rods that transmit the shroud tension to the actual chain plates that are embedded into the fiberglass hull should be TIGHT, just like the shrouds.  
Caution on tightening the two side nut/bolts on each side of the rod, as you can over tighten and "dimple" the deck (by compressing the plywood core).  A thought.  

[Roc]

Gary,
I disassembled the whole chainplate & rod system when I rebedded them last year.  If I remember correctly, the rod is connected to the chainplate at the deck (threaded into a swivel joint), and to a piece of angle iron bonded to the hull with the 5/8" nuts behind the port/SB Settees.  You want to tighten the nut just enough to take any slack out (called Gerry Douglas and he said to make them 'just snug enough').  The way it's designed, there is nothing that will stop you from tightening too much, causing the chainpate to bend away from the deck.  When I did mine, I marked how many threads where exposed behind the nut, so I could get it close to where it was originally, then I could assess how much tighter it needed to be without overtightening.  These rods are to transfer the load on the rigging to the hull and not the deck.

Also, you say your boat is on the hard.  I would do this after the boat has been in the water a couple days.

[Gary Ambrose]

H Ron,

Right, too much tension on the chain plate rods will result in deck compression.  When shrouds are attached and properly tensioned, of course, that begins to act to mitigate pressure created by the rods. A parallel question ...is pressure apt to be different in the water from being on land.  It would stand to reason that hull shape moves things around a bit just as engine shaft alignment is temporary out of the water until hull shape adjusts for final in water alignment.  I know this may be excessive concern but I am interested in the conversation on C34 dynamics.

My guess here is that "proper tension" is firm but not enough to cause deck deflection downward toward the cabin interior.

Still, I wish someone knew the torque requirements below decks to the chain plate rods.  Perhaps this thread has been useful to others that may not have examined their rods. I would love to know if anyone found overly loose rods or missing lock nuts as I did.

Gary

[Gary Ambrose]

Ho Roc,

Well, that is just the info I was looking for.  It seems we posted at almost the same time.  My reply looks weird after yours.  It is as I suspected. The tension needs to be "just right" not too much not to little, and after the boat is in the water.  It makes me wonder if the looseness I encountered may have been the correct in water adjustment.  We'll see. I will recheck after launch on Thursday.

Many thanks for the thoughtful response.

Gary

[Mike Vaccaro]

Gary,

The rod only carries the tension load of the rig.  Most of the load is borne by the hull via the nut/washer assembly at the base of the rod.  Hence the recommendation for "just snug."  Like Ron said, any extra load on the rod WILL cause deck compression.  This is evidenced by dimpling or cracked gelcoat around the chain plate.  If the deck core is sound, any minor damage of this type was caused by someone over tightening the rod nuts at some point in the past.    

A single nut and washer is sufficient for making the system work, but an additional hut serves to lock the primary nut, and additional washers may be used to simplify nut adjustment (i.e., make it more assessable.  Due to variance in construction (all of these boats are hand-built), it wouldn't be practical to develop a torque specification.  Hand tight, plus a turn or so should be sufficient--just be sure to check the deck for signs of compression during the process.  If a nut is loose, the rig load will be borne by the deck until the structure flexes to the point that the nut/washer is pulled tight.  

It's best to make rigging adjustments with the boat in the water.  The fiberglass structure of the C34 hull is flexible enough that there will be a difference when the weight of the boat is evenly supported by buoyancy vs. cradles and/or jack stands.

Best of luck,

Mike

[Ron Hill]

Gary : If you are really worried about torque, call Gerry Douglass and talk to "The Man".  

[jpaulroberts]

Hey, guys, I have taken out my chaplets and cleaned up the area. I am about to re-bed (they were all leaking). I have dried and sealed all the wood core in the area. What is the best bedding compound to use in this application? 3M 4000, 4200, or 101? Thanks, Jerry

[SteveLyle]

101 is 3M's polysulfide product.  Polysuflide is what has been traditionally used as a bedding compound, above or below the waterline.  It's likely  what was previously used on your chainplates.  It's not marketed as an adhesive, but as a sealant.  

4000 UV and 4200 are relatively new products that are weaker versions of 5200 in terms of adhesive strength (1/2 the strength).  3M markets them for adhesive/sealing, for use on non-permanent bonds (vs 5200, which is essentially permanent).  

What 3M says:
101 product uses:  3M Marine Sealant 101 may be used in typical bedding and sealing applications including fiberbglass deck to fiberglass hull, wood to fiberglass, portholes, deck fittings and moldings.  Features:  flexible; one-part cure; non-sagging formula; non-shrinking; excellent weathering resistance.

4000 UV product uses:  3M Marine Adhesive Sealant 4000 UV may be used in typical bedding and sealing applications including fiberglass deck to fiberglass hull, wood to fiberglass, porthole frames, deck fittings, moldings, thru hull and deck hardware.  Features:  superior UV resistance; exceptional sealing properties; non-shrinking; non-sagging; non-corrosive; non-cracking; fast curing.

4200 product uses:  3M Adhesive/Sealant Fast Cure 4200 is designed to allow disassembly of wood and fiberglass parts bonded together.  If a permanent bond is desired use 3M Marine Adhesive/Sealant 5200 or 3M Marine Adhesive/Sealant Fast Cure 5200.  Typical bonding and sealing applications include:  fiberglass deck to fiberglass hull; wood to fiberglass; portholes; deck fittings; moldings; trunk joints; between struts and planking;stern joints and hull planking.  Structureal bonding and sealing of:  wood; fiberglass; gelcoat; primed metal.  Sealing of: some plastics (test before assembly); glass; metals.

I'd use 101.  It's the incumbent.  4200 looks like overkill.  4000UV sounds like a potentially good candidate/alternative.  

It's your boat, good luck.

[Mike Vaccaro]

Jerry,

Steve is correct--stick with polysulfide.  Depending on how often you sail, the conditions and the rig tune, you'll end up re-bedding in the future if you keep the boat long enough.  It's not a matter of "if" but "when." A chainplate/deck interface is a dynamic assembly in the Catalina 34 due to flexing of the boat and rig.  Eventually, any seal will be broken either due to flexing or deterioration of the sealant.  Since rebedding will be required, it's best to use a good sealant that will be easy to clean up when the time comes to replace it.  Polysulfide fits the bill.

Cheers,

Mike