Chain Plate Relocation Advice

[smitty56]

I’ve been a member of this forum since last fall. It’s a great forum I’ve found a lot of good information here. I bought a 1979 hunter 30 last fall. I plan on retiring in three years to sail around the Great Lakes and then head down to the gulf through Illinois, Mississippi, Tombigbee, and thehttp://en.wikipedia.org/wiki/Mississippi_River Black Warrior River to Mobile, Alabama then around the Caribbean for a few years and eventually up the east coast back to the Great Lakes.
I wasn’t looking for a hunter and from all the Hunter bashing on a lot of the other forums I had taken them off my list. Then I found this one and had to take a closer look I was surprised how well built it was compared to other boats I’ve worked on. It was also helped that it was on the hard at marina 20 minutes from my house. The boat has always been in fresh water and spent most of its life at the dock I bought it from the second owner and from looking at the rigging and talking to the marina owner he never sailed it. I don’t believe he even knew how to sail. The diesel has 250 hrs on it. The sails look like new except for the main which spent most of its time on the boom under its cover.
My plan is to make it as blue water capable as it can be; just in case. I have a long list of projects to do before I re-launch it next year. The first thing I’m planning on addressing is the chain plates. The port side center chain plate has been leaking and damaged the bulkhead as well as causing about a 6 foot section of the deck to become saturated. I plan on re-coring the deck, repairing the bulkhead, glassing the bulkheads and knees to the deck as well as glassing the hull to deck joint from the inside all with epoxy. I was going to leave the chain plates in the stock location but then I read on here that moving them to the toe rail and using U-bolts was a good alternative I like that idea and would like some more input. I’m most likely going to replace and maybe up-size the standing rigging anyway. Moving them out for added strength and eliminating the chain plate holes in the middle of the side decks seems like a good idea. I’m not worried about the sheeting angles for the genoa. I’m planning on adding a solent stay so the smaller jibs on it could be sheeted to at track mounted on the deck inside the spreaders. Just looking for more input. Thanks in advance!

 

[Paul F]

Interesting idea. The back stays are held by U-bolt "chain plates" and would seem to be under more pounds of pull than the side stays. A U-bolt is stressed by bending when made. This makes them weaker than steel plates. Also the side plates are held by five bolts rather than two end nuts and are stronger. If you are going for a stronger boat the original design may be the best.

 

[smitty56]

[FONT=&quot] Actually my back stays have flat chainplates. Navtec makes u-bolt [/FONT][FONT=&quot]chainplates so I’m assuming they would be strong enough they are used on Bristol, Cal 28, C&C LF 38, Ericson, O'Day 30, the Hobie 33, and others.[/FONT][FONT=&quot] They generally use a rod, or cable, to transmit stresses to a lower load bearing point. I would probably put backing plates and tie them in to the bulkheads with tabs similar to the existing chainplate. I’m not convinced it’s worth the effort [/FONT]

 

[Steve Dion]

If that was such a good idea, I don't know why Hunter would not have done it at the factory. They could have saved themselves a bundle of money.

I think your original idea with the repairs are the correct way to make the fix.

 

[sandpiper10471]

If you were to move the shrouds outboard then add sheeting tracks, you will end up with even more deck perforations. The only thing you will accomplish by doing so is reduced mast compression which is a good thing but the rig is tried, tested and true. Stick with the original concept and save yourself a lot of aggravation. Mounting chainplate to the topsides is a lot more complex than most people anticipate and requires a lot of structural glass work.
I suggest most of your repair work be done in polyester. It is cheaper, less toxic, faster, easier to work and more than adequately strong.

 

[DianaOfBurlington]

U-bolts through toerail

I think my suggestion has already been posted here; but I'll provide another version in case no-one wants to look up the archives.

Hunter did not go with U-bolts as chainplates in their early days until Cherubini Boat did. This was a judicious decision Lee and I made based on the advertised strength ratings of cheap commercially-available Attwood U-bolts in 316 stainless. The 1/2" ones had a mean working strength of 16,000 lbs; the 3/8" ones were 12,000 lbs. From both engineering and cost perspectives, using these was a no-brainer.

Hunter did not retro-engineer their boats to accept U-bolts after this (c. 1978-1980) because, as a rule, being a production company Hunter didn't retro-engineer anything. They did as most production concerns go; they kept making them like they had been till they moved on.

For a boat with an extruded-aluminum toerail, there is really only one reason to not go with the U-bolts mounted through the extrusion. Having shroud-attachment points out on the rail limits jib-sheeting options. For a boat with wide side decks and a narrow shroud base, like the Raider 33, this would be a serious detriment. It's really the only reason to have through-deck chainplates, as every other single factor is solved much better by bringing them to the aluminum toerail. Doing so is stronger, cheaper, and easier to install and to fix. All it takes is basic reinforcement of the toerail-attachment points, under the deck flange, and adequate hardware-selection, installation and maintenance practices.

Given any boat with relatively narrow side decks or a moderate-to-narrow beam (like our early-1970s Hunters), there is no logical reason to go to all the added expense and vulnerability of cutting holes into a cored deck and fastening major structural rigging members to pins in sheer load through plywood.

 

[Blaise]

You will regret doing this. Just the force of a snatch block will bend the toerail. JC did a great job with these boats. Don't second guess him.

 

[Ian McGain]

I considered the same question as your post and if you check the thread, received similar answers which amount to do not do it. At the end of last season, my starboard middle standing plate pulled right out of its location due to wood rot that I had missed. It was always on my list of things to do. Luck was with me, and I caught it and dropped my sails before I lost the mast. Port side was OK. On my '79- 30', the fore and back standing riggings bolts to fiberglass on both sides.

 

[Pilotocopilot]

Hey John if I understand you correctly, you don't see any issue if the attach point for the shrouds are moved outboard to the Toerail. I think I actually discussed this with you and the group, about outboard chain plates on the 37 as it's a bear moving forward. If this is true than I would seriously consider moving the forward and back lower shrouds to the sides without moving the upper. Any thoughts or concerns.

 

[DianaOfBurlington]

On U-bolts... once more

Hey John if I understand you correctly, you don't see any issue if the attach point for the shrouds are moved outboard to the Toerail. I think I actually discussed this with you and the group, about outboard chain plates on the 37 as it's a bear moving forward. If this is true than I would seriously consider moving the forward and back lower shrouds to the sides without moving the upper. Any thoughts or concerns.

Hey P2CP.

In all truth I really don't comprehend the concerns about this. It's a solidly good idea (and I am not taking credit for it). Poor Smitty56 is looking at so much extra work I worry how he's going to feel after opening up a bag of worms.

Consider:

1. The toerail is mounted to the hull flange, the strongest part of the boat because it's like an angle-iron made of fiberglass. The toerail is held in a 3-D shape, curved like the sheer, curved like the deck, and at (roughly) a 90-degree angle to the hull sides. You are not going to distort that shape with any force that won't do major damage somewhere else first.

2. The toerail is T-6066 aluminum-- spar grade. It's an extrusion, not welded. On most of our boats it may be the single piece of metal (well, two pieces of metal) that is in the best condition on the whole boat. And you are going through its flat part, not pinning to its eyeholes, so it's acting as a very long, very stationary backing plate. For the shroud attachment to fail you'd have to rip up the whole length of the toerail at once-- because, mathematically, it's not going to distort very far with all those properly-tightened bolts properly spaced apart (that's why there are so many of them).

3. Screw threads are monumentally strong. A threaded hex nut is designed to hold the full tensile load of the screw whose threads it's on (--what would be the point if it didn't?). So long as you have the full nut's height of threads engaged, and a bit more for the washers and for safety, with the proper-sized hole, a properly-tightened nut won't give up on its threads. And given a good backing plate, it won't pull through. Use of heavy-pattern flat washers is the way to ensure this. Also, nylon-insert locknuts are no less strong than regular hex nuts; they are taller to allow the nylon part as anti-vibration security but do still retain the correct quantity of threads. For this application I would purchase high-quality U-bolts, so as to have precision threads, and then replace the hex nuts with nylon-insert locknuts, as this is the perfect application for them.

4. A backing plate is easy to fabricate for this (because it will need stiffness under the hull flange) and can be made out of anything. Smitty56 would be best to reinforce the shrouds' area of the hull flange-- add a few more layers of 16- or 17-oz biaxial, for example) and then to fabricate a long narrow backing plate of 1/4" or 5/16 aluminum. Make it catch as many of the toerail bolts as possible for about 12-18" beyond the lowers' U-bolt holes. Remove all the affected toerail bolts and fasten this thing in place. A bit of 5200 couldn't hurt.

5. The 316-SS U-bolts are readily available-- actually they are becoming more popular for all sorts of things. When we bought them for C44s in the '80s we bought them as 'ski boat eyes'. They were really meant to go through the transom for tying down speedboats on trailers. The load ratings were phenomenal-- in theory two of them would lift a Cherubini 44. We instituted a policy of recommending to our boats' owners that the U-bolts get swapped out every 12 years or so. This hedges against crevice-crack corrosion (for SS never likes to be totally immersed in airless environments; the part of it that is buried will slowly rust). And each time the replacement options become proportionately cheaper and of higher quality.

6. The U-bolts, whose radius will not match that of the shroud clevis pins, will indeed distort under load. But it will take some doing! The molecular structure of 316 SS in particular makes it 'brittle' (which is a relative term) and thus unwilling to move much. In most usage it won't be seen to have moved any at all. But, should it give just a little (like if you are using U-bolts whose load rating is somewhat close to what's required, say, for example, 7000-lb U-bolts for a 10,000-lb 30-foot boat ), the molecular movement will actually work for you. Suppose, under (extreme) load, the round U-bolt distorts towards an elliptical shape by, say, .001". With 316 SS, the amount to move it the next .001" will be TEN TIMES that load amount. It will have gone ten times more brittle as well; but the numbers we're talking about are so extreme that simply oversizing the U-bolt (like me using 8-mm ones, about 9/32", on my H25 for 5/32" rigging when 3/16" stock would hold the load) should provide sufficient overkill. Remember this is a boat-- it's in water-- so whatever threatens to snap off your moderately-oversized U-bolt is more likely going to just heel the blooming thing over-- and thus reduce the load. Once the U-bolts have distorted, if you perceive any slackness in the rigging, simply retighten it. Rigging should never be allowed to slack-- even on the leeward side-- anyway. Type-316 SS doesn't like shock loads-- because it's more 'brittle' than 304 SS-- but neither does your aluminum mast. Constant tension reduces stress/unstress cycles. Keep it all in proper tune at all times and your spars, wire and U-bolts will last much longer with no problems.

As I said before the biggest drawback with this idea is losing the ability to sheet that genoa flat up against the cabinsides whilst hard on the wind. But as most of us cruise casually more than race hard-core, we've learned to be able to compensate for our modest cruising boats' performance and have probably become better sailing tacticians because of it.

You also might have to lengthen your shrouds a bit; in most cases a nice bronze toggle might be enough to resolve this. Structurally the uppers will 'stretch' over to fit; all that's lost, besides having to include a toggle, is that the spreaders, which always bisect the wire angle if left alone, will appear slightly flatter, with less 'dihedral' than before. But most people may never notice this.

Also, an upgrade of this kind might signal a good opportunity to change out the wire rope anyway; so have it all new and have fewer concerns for the near future.


Maybe I am just a Luddite but I don't like relying on technology. I prefer to rely on what can be learned and gained from learning, not on what I can buy to 'solve' all my 'problems'. I've relied on that ethic for 40 years in this business and it's only ever failed me when I've ignored it!

 

[smitty56]

DianaOfBurlington,
Thanks for your input it was your postings I was referring to. I apologize for not getting back on here sooner to thank you for your input. I’ve been traveling a lot for work lately and hadn’t had a lot of spare time. Don’t be too worried about me opening up a can of worms I’ve repaired much worse problems that what this boat has. The weather finely cooperated and I was able to spend a few days working on the boat. The interior parts that needed to be removed to allow access have been and the area’s that are going to be glassed have been sanded and are ready for glassing the bulkhead template is made. I have decided to take your advice and go with U bolts. I’m leaning towards EPCO Bow & Stern eyes however I don’t have a price on them yet. Here is their site: http://epcomarineproducts.com/bow_stern_eyes/
I plan on a couple of layers of biaxial as you suggested but I was going to use 3/8 G10 for a backing plate I have made templates for a plate 4 ft. log by approximately 2.5” wide cut to the contour of the hull and they would be glassed to the underside of the deck, the hull sides and to the existing chain plate knees and bulk heads then some large thick stainless washers on the U-bolts with double nuts. I already have nice bronze toggles that have ½” pins so I’ll probably go with ½” U-bolts. It may be over kill but as long as I’m doing it I might as well; prepping it is the worst part of the job and it’s already done. I’m also contemplating moving the life lines out to the toe rail area. This is only the beginning of the refit. Ill be posting more I appreciate all the input.

 

[sirMichaelJAM]

Re: On U-bolts... once more

DianaOfBurlington,
I remember reading your other post some time ago. I have a '76 hunter 30 and the chain plates on both fwd shrouds are broken. This has been this way since I purchased the boat last year. I have moved all the shrouds to the eyelets temporarily while I prepare to replace the 6 chain plates (Not sailing like this!). Then I remembered reading something about moving them to the toe rail. I think this is really the way i want to go because of damage to the inside wooden bulkhead where the port chain plate is attached. My question is this, if I used a 3/4" - 1" Starboard backing at a length of about 5' under the toe rail do you think there would still be a need to glass over it? I was thinking that I could cut the piece out using the toe rail as a template then pull the bolts from the toe rail section. Put 5200 on the Starboard to the inside of the boat as a backing plate. Drill the holes for the toe rail and the 316SS ubolts. Replace all the bolts. Also put a 316SS backing plates on the Ubolts.

 

[coleman]

My question is this, if I used a 3/4" - 1" Starboard backing at a length of about 5' under the toe rail do you think there would still be a need to glass over it?

Starboard is High Density Polyethylene (HDPE). This plastic is very flexible and is also known to creep under constant load. This might not be a good choice to make backing plates for your shrouds.

 

[H30Gary]

SirMichael -
I too think that HDPE (Starboard) would not be a good choice. Its too soft and flexible. A better choice in my opinion would be 1/4" to 5/16" aluminum as JC2 suggested, or 3/8" G10 as Smitty56 is planning to use. I personally would lean towards the G10, to avoid the corrosion issues with aluminum.

Either way you go, I'm not sure it is necessary to have a backing plate that extends the full length from the rear lower to the front lower. I would say a 6" or so long plate under each U-bolt would be sufficient. This would avoid having to machine the plates to match the curvature of the boat, which be a real pain with G10 (the stuff is tough as nails!)

You can get G10 online from McMaster-Carr. They carry many sizes in stock and deliver quickly for a reasonable shipping charge.

Gary

 

[jphud]

On an H37C is there a need to keep the side stays in the staggered configuration, or can all three run out to the rail?

 

[sirMichaelJAM]

Colman, thanks for the input, I didn't realize it was that flexible.

H30Gary, G10 looks like it would do the trick, what do you use to cut it and drill it. Would there be a need to still put glass over the top of it?

SirMicahel

 

[H30Gary]

Colman, thanks for the input, I didn't realize it was that flexible.

H30Gary, G10 looks like it would do the trick, what do you use to cut it and drill it. Would there be a need to still put glass over the top of it?

SirMicahel

I've cut it with a handheld electric jig saw and a high speed metal blade. Blades wear out quickly though! Same deal on drilling - high speed metal bits.

I don't know if you'd have to glass over it. Its basically fiberglass and epoxy resin. Glassing over fiberglass seems a bit redundant, except maybe for appearance. But I'm no expert, so maybe someone else can weigh in on this.

 

[sirMichaelJAM]

Hi All, I am about to order the parts I need to move from chain plates to U-bolts on my 1976 30' Hunter. Does anyone have any recommendations on what the working load should be? I was looking at 3/8" stainless U-Bolts.
Thank You
SirMichael

 

[H30Gary]

You'd want something at least as strong as the shroud wire, maybe double this strenght. Not positive of the shroud wire diameter/construction on your boat; it may be 1/4" 1x19 SST, which has a breaking strength of 8,200 lb. I'd want the u-bolt at least this strong, and as I said, maybe double this strength. Wiichard 13/32" U-bolts have a breaking strength of 15,400 lb. So I think 3/8" (12/32") should be OK. But you should check all of this math.

 

[sirMichaelJAM]

You'd want something at least as strong as the shroud wire, maybe double this strenght. Not positive of the shroud wire diameter/construction on your boat; it may be 1/4" 1x19 SST, which has a breaking strength of 8,200 lb. I'd want the u-bolt at least this strong, and as I said, maybe double this strength. Wiichard 13/32" U-bolts have a breaking strength of 15,400 lb. So I think 3/8" (12/32") should be OK. But you should check all of this math.

Hi H30Gary, the ubolts i ordered have a breaking strength od 16K lbs so they should be good. i ordered 3/8in G10 for backing. appreciate the input.

SirMichael