Hunter sinks at Catalina due to bow cleat failure

[smackdaddy]

Originally Posted by transmitterdan

I am not crazy about the idea of burying a backing plate inside the laminate and then bolting the sandwich together. In my opinion (and based on experience with bolting laminates) this goes a ways toward defeating some of the purpose of the backing plate. The backing plate is supposed to make it harder to pull the bolts through the laminate. At first glance an embedded backing plate would seem to do that. But the way a backing plate is supposed achieve that is by reducing the pressure and thus fracturing. An embedded plate does not do that. The nut and washer are still applying high pressure directly on the laminate in a small area same as if the backing plate did not exist. Once laminate starts fracturing then complete failure becomes more and more likely over time.

Additionally, laminate will "cold flow" more without a backing plate to reduce the pressure. High and low temperature excursions can cause expansion fracturing too. The symptom of this would be a cleat that keeps coming loose and the nuts have to be tightened every spring. This can also lead to laminate failure.

So even if there is a metal plate embedded in the laminate there should also be a similar size plate between the nuts and the laminate in my opinion. And there should be load bearing bedding material under the backing plate to evenly pressurize the laminate to minimize the chance of fracturing.

I don't know if you watched the Hunter video posted earlier, but I think you're misunderstanding how it's done. After the full lay-up of the deck is finished, they come back and glue the backing place to underside of the deck. They then place a couple more layers over the backing plate.

So nothing is really sacrificed at all. The second layer seems to be only for additional bonding of the plate and maybe metals separation.

(Oops - I just noticed that Neil already addressed this.)

The thing I'm wondering about in this case is the plywood core material in the deck. As Cole mentioned on his boat, the core is left off the hardware areas, and they lay up full glass in that spot. I don't know if Hunter does this or not (wasn't clear from the vid). But if not, then I could see where it might be weaker.

On the other hand, you look at the photos that Jon posted earlier and there is an indention of the rail/deck at the area of the cleat. So they may very well leave the core off and fully glass this. I guess we won't know until we see the hole left by the cleat - if we can ever get that.

[neilpride]

Smack, its your Legend deck ply cored???

[transmitterdan]

Originally Posted by smackdaddy

I don't know if you watched the Hunter video posted earlier, but I think you're misunderstanding how it's done. After the full lay-up of the deck is finished, they come back and glue the backing place to underside of the deck. They then place a couple more layers over the backing plate.

It would be interesting to know the exact stackup. But in many industries it's a big no-no to run a structurally sensitive high load nut and washer stackup directly on a laminate. FRP has too high a coefficient of expansion and eventually the laminate will "crush" itself during expansion (or the bolt will stretch) and the nut is then loose after contraction. Once the nut is loose it's a pretty rapid slide down hill from there. I can't see the benefit in putting laminate layers over the backing plate. Would be interested if someone can explain the presumed benefit.

[neilpride]

Originally Posted by transmitterdan

It would be interesting to know the exact stackup. But in many industries it's a big no-no to run a structurally sensitive high load nut and washer stackup directly on a laminate. FRP has too high a coefficient of expansion and eventually the laminate will "crush" itself during expansion (or the bolt will stretch) and the nut is then loose after contraction. Once the nut is loose it's a pretty rapid slide down hill from there. I can't see the benefit in putting laminate layers over the backing plate. Would be interested if someone can explain the presumed benefit.

Ohh you hit the nail, no benefit at all and some drawbacks, corrosión the main isue..

[Jim Cate]

Would be interested if someone can explain the presumed benefit.

Since the embedded plates are aluminium, perhaps they are trying to minimize dissimilar metal corrosion issues.

Seems that if the caulking for the bolts fails and salt water intrudes to the Al plate area, the expanding corrosion products will fracture the laminate, and because it is buried, no one will know until (or if) it fails structurally. Even worse than cored deck issues from through bolts!

I for one would be happier if the alloy backing plates were external to ALL the laminate.

Jim

[smackdaddy]

Originally Posted by neilpride

Smack, its your Legend deck ply cored???

I honestly don't know what the core material is. I'll be rebedding the forward hatch in a few weeks so I'll let you know.

[Exile]

Originally Posted by smackdaddy

I got this far then my eyes glazed over and I started drooling as you began your life-lessons. I just couldn't continue.

It'll be all right. There will be clean bibs you can wear for the drool, and you can always try again tomorrow.

Anyway, yes - the backing plate did rip out of the Hunter in question in this thread according to the report from the owner. Is that a serious failure that shouldn't have happened? Well, it was a failure for sure. But, given the circumstances of 8' breaking waves and the mooring from a single cleat, I'm certainly not ready to call it "weak laminate" or "poor build quality", etc. Just not enough facts yet to determine that I don't think.

I have absolutely no idea whether anything attributable to the boat's build quality contributed to the cleat yanking out, and given all the variables and forces at play, I haven't read where anyone else has rendered any sort of definitive conclusion either. All I read is that the entire cleat assembly came out intact, tearing out the laminate along with it. Hopefully you won't attack anyone for suggesting possible scenarios, even if they don't cheer for your favorite team.

So, I'll keep reading.

I'm sure you will, along with distorting, confusing & misconstruing other posters' comments.

Before you succumb to another rush of indignation & drool, I think I read somewhere that Hunter's may have bronze through-hulls. Feel better now?

[Brob2]

Originally Posted by transmitterdan

It would be interesting to know the exact stackup. But in many industries it's a big no-no to run a structurally sensitive high load nut and washer stackup directly on a laminate. FRP has too high a coefficient of expansion and eventually the laminate will "crush" itself during expansion (or the bolt will stretch) and the nut is then loose after contraction. Once the nut is loose it's a pretty rapid slide down hill from there. I can't see the benefit in putting laminate layers over the backing plate. Would be interested if someone can explain the presumed benefit.

Originally Posted by neilpride

Ohh you hit the nail, no benefit at all and some drawbacks, corrosión the main isue..

Originally Posted by Jim Cate

Since the embedded plates are aluminium, perhaps they are trying to minimize dissimilar metal corrosion issues.

Seems that if the caulking for the bolts fails and salt water intrudes to the Al plate area, the expanding corrosion products will fracture the laminate, and because it is buried, no one will know until (or if) it fails structurally. Even worse than cored deck issues from through bolts!

I for one would be happier if the alloy backing plates were external to ALL the laminate.

Jim

I'm not sure what is being suggested as the wisest approach. Are we saying hardware and backing plate over laminate over backing plate with nuts exposed under the deck? But still the nuts will loosen over time as the FRP expands and contracts? I'm missing something.

[smackdaddy]

Originally Posted by Brob2

I'm not sure what is being suggested as the wisest approach. Are we saying hardware and backing plate over laminate over backing plate with nuts exposed under the deck? But still the nuts will loosen over time as the FRP expands and contracts? I'm missing something.

It's a Hunter.

[Robin3]

Originally Posted by CarinaPDX

Robin3-

When I first got to the UK (1997) I noticed a few boats tied to the dock with chain, thought it a bit odd but didn't give it another thought until I arrived in a marina that explicitly banned chain tie-ups. So I asked why and was told of the excessive damage, which included both wear and high impact loading. After that I did observe a fair amount of cleat damage from chains on cleats. Of course it matters how the chain is attached - as you note using a shackle or hook will not have the side-to-side wear that other schemes would. My reaction was to your idea that the chain would be attached to line on either side, which in turn was attached to the cleats. The two sides will never stretch exactly in tandem so there will be some grinding action. Initially it will only have a minor impact, of removing the zinc galvanizing and thus starting corrosion to the steel. My concern is for the long-term extra wear. In any event the chain-only or mostly-chain approach will reduce even more the snubbing action of the pendant and thus increase the impact loading on the rest of the system (including the cleats of such interest here).

I normally pick up a mooring with bow lines looped through the eye and then back to the same cleats ("in slips" as the Brits say) which is great for making a quick gettaway if the situation deteriorates. But for holding in a blow (a situation I would go to extremes to avoid) then the previously recommended way of using separate lines firmly attached to the ring will effectively eliminate chafing at the ring which otherwise could become quite dangerous.

I share your view of moorings - when transient it is impossible to know the condition of the moorings short of inspection with scuba gear. Some harbormasters (as yourself apparently) are careful about inspection and maintenance, others less so. Sometimes the moorings are simply placed too close together to be safe in a blow (I am reminded of the mooring field at St. Marys in the Isles of Scilly - I hope they have spread them out since I was there). Sometimes they are simply inadequate to hold a heavy cruising boat (a certain anchorage in the Med that banned anchoring and provided undersized moorings comes to mind - it took 3 moorings to finally hold my little boat in F6 in the lee). Personally I avoid moorings if at all possible; I would rather trust my own anchoring than someone else's mooring. Sometimes that is not possible, as anchorages are being converted to moorings everywhere. There are good reasons, such as more boats being able to enjoy a place, and less damage from anchors and less damage from dragged yachts. There are bad reasons too: deny anchorages to transients so that they must pay either for the mooring or a nearby marina (you gotta love the Med for that).

Greg

I think we are talking about different scenarios here Greg because I would never suggest mooring to a dock or marina pontoon by doubling a line with included chain through a cleat and never saw that done. However, lots of folk, me included, made up permanent dock lines specifically for our home berth/slip and shackled these to a very short length of chain threaded through the cleat, simply because a single shackle to fit the cleat would need to be huge and likely too big for a hard eye in a mooring dockline. This was in place of simply tying off the line or cow hitching a spliced loop to the cleat. The chain length in a doubled line procedure was used only for mooring buoys or balls which had top rings and were not provided with proper pendants for the visitor to pick up. Some places did provide buoys with pendants and pickup buoys to aid grabbing them and taking them on board, but often the pendant was far to big for the boat's bow roller and/ or would not fit over the boats deck cleats so many places that put down moorings for visitors just had the ubiquitous white buoy with a ring on top. We would use a detachable snaphook line on a boathook to initially attach to the ring and then use a 'happy hooker' line threader device to feed a line through to which we tied our chain length then jiggling this line/chain to get the chain in the ring and taking the load whilst taking chafe of the line out of the equation. as previously mentioned we would in exposed places even haul this up to place chain over our bow roller to prevent potential chafe there also. on departure it was an easy task to pull the chain/line through and untie the line ends from the chain length and slip the line and move off. I wish I had pics or diagrams I coul post to explain better but I don't and I know my wordy explanation is difficult to follow.

So in simple terms to get back to the original disaster situation, I would not have been there if I had expected the conditions described to arise and if I had been there unsuspectingly but later thought it a possibility would likely have moved away somewhere safer.[/smug mode]

Robin.

PS I never once used provided moorings in the scillies.

[BobH260]

Originally Posted by smackdaddy

You're really focused on this "fuse" thing. First, in the case of the cleat construction described by Bob, the fender washers are really not spreading any real load to speak of - other than ensuring a larger surface area across the glass lam over the backing plate than just the nut on the glass.

I think Bob's point is that if someone that was uninformed just looked up underneath the deck and took a pic - they would probably just see two fnder washers over laminate. Then they would post that pic on a forum and talk about how flimsy Hunters are built with Micky Mouse Washers - not understanding that there is, indeed, a substantial backing plate under those washers, and under the laminate they see in their photo.

Now, on this point, I will admit that up until Ralph talked about the glassed in backing plates on the Hunter, and based ONLY on what I'd seen and heard in these various threads on CF, I likely would have been one of those that thought my cleats were only held in place by fender washers. I would have been concerned. And I would have been just as wrong as everyone else criticizing Hunter.

Finally, the "fuse" thing. I never said such a fuse would be a good idea for a cleat. I said there are some cases where it might be a good idea based on the particular design and construction of that item and that area. Simply not seeing a backing plate in a specific area certainly does NOT mean it's poorly engineered or built.

I think this is becoming clear now.

I think when a boat is built to comply with ABYC standards and the manufacturer uses a cleat for say a 1/2" or 5/8" line then that cleat can not pull out at less than the breaking strength of that size of line.

Some folks do like to up-grade the cleats on their boats but some times don't consider increasing the size of the backing plates that might be needed.

Bob

[Exile]

Originally Posted by SV THIRD DAY

Sing along...

31 Pages of worthless Thread on the wall
31 pages of Thread.
You take one down, pass it around, 32 pages of Thread on the wall....

Now about that "list" of yours . . . .

[BobH260]

I have drilled a couple of holes where the aluminum deck plates are in a Hunter. Solid glass then the aluminum plate.
Our boat was built in Florida, lived 5 years up north and now 5 years in Florida. A fair bit of thermal cycling there I think. Never had to tighten any cleats, line stoppers or anything else mounted on the deck. The holes in the aluminum plates are threaded not sure if that makes a difference. Lots of Hunters in Canada, temps go from 90* in the summers to -30* in the winter, never heard of a cleat coming loose.
The Hunter coring I've seen is wood, appeared to me to be balsa, 2" squares, each one sealed with resin. I've not seen any plywood used in the laminates. These boats were all 2000 or newer.

Bob

[autumnbreeze27]

http://www.cruisersforum.com/forums/...el-139308.html

Looks like there's a hunter being cut up for salvage after the skipper tangled with a bridge; if any of you hunter owners need parts.

[transmitterdan]

Threading the embedded plate would make a difference. It means the nut on the inside of the boat isn't structural and is acting more as a locking device. As long as the stainless bolt that screws into the aluminum plate as lots of anti-seize it is probably as good as any other system. But drilling out the threads in a repair scenario would create the need for a new properly bedded backing plate on the inside in my opinion.