Is this Crevice Corrosion or a Bad Casting?

[colemj]

BTW, if you want cleats that won't break, buy a Catana. They only order one size of cleat for all of their boat models - the size appropriate for the largest one they make (65'?). On a 43' model, those things are ridiculous!

Maybe other builders do the same?

Mark

[lateral]

Originally Posted by Ex-Calif

I wouldn't defend or condemn the design but as an engineer who has seen a lot of stuff fail, if you gave me a new one of those and asked me where it would "eventually" fail - I draw a picture of the two failure locations that have occurred.

The countersunk hole has little edge distance and it is inarguable that the c'sunk screw loads the hole in tension. The failure near the vertical is classic bending indicating that when this corrosion weakened part was being mounted the bottom was not sitting flat and because the tang that carries the bolt holes is thin and would fail, right where it did in the radius.

That was my line of thinking when purchasing cleats.
Hence the bolts through the body. (Even though m/crews reduced by 50%)
I ignored the bending moment as the distance from the deck is little. But there definitely must be an element of bending to be considered.

BTW, Mark, whats with the echo?

[Ex-Calif]

Originally Posted by colemj

Our boat is loaded with this style of 10" cleat. On ours, there is 1/4" of meat at the thinnest part at the top of the holes, and 1/2" of meat at the hole itself. The countersinks are designed to exactly fit oval or pan head 1/4x20 bolts. This fit adds to the strength in this area. The base itself is 1/4" thick.

I'm not arguing that this spot isn't where failures WOULD occur - I am arguing that most decks would rip out before the cleat itself failed.

Mark

What you are describing sounds like counterbored not countersunk.

Counterbored with panhead bolts is superior if the material thickness is sufficient for the cleat loads. The clamping load does not put tensile load on the hole and the joint is in compression.

[colemj]

Originally Posted by lateral

T
BTW, Mark, whats with the echo?

Sorry about that - we currently have the worse internet connection in the entire Caribbean (SHELTER BAY MARINA - TAKE NOTE!). For some reason, the stalls and starts are posting twice on me. I am removing them as fast as I can…

Mark

[colemj]

Originally Posted by Ex-Calif

What you are describing sounds like counterbored not countersunk.

Counterbored with panhead bolts is superior if the material thickness is sufficient for the cleat loads. The clamping load does not put tensile load on the hole and the joint is in compression.

I'm pretty sure these are countersunk - they are V-shaped and take oval-head or flat-head machine screws, not pan-head.

1/4-1/2" is a lot of meat.

Mark

[Auspicious]

Originally Posted by lateral

But the working load to the M/screws & body of the cleat is surely a combination of shear & tension force?

The machine screws would be in tension and shear (mostly shear unless you are lifting the boat by the cleats). Given pre-load in compression from the mounting the cleat will be in some stage of compression and some shear.

As others have noted cleats don't usually fail in normal service. I've seen some fail from impact.

Crevice corrosion is a possibility. So is fatigue if they are old enough.

[Ex-Calif]

Originally Posted by colemj

I'm pretty sure these are countersunk - they are V-shaped and take oval-head or flat-head machine screws, not pan-head.

1/4-1/2" is a lot of meat.

Mark

Ah... flat head countersunk bolts - got it...

Yes your cleats sound meatier than the ones in the pics above.

[Orion Jim]

Spartan Marine makes bronze Herreshoff cleats here in the U.S.A.. I'm using one right now that's as good as the day it was cast, 30+ years ago.

[sully75]

The break was really porous and jagged. It felt kind of like concrete. I think I tossed the cleat. Haven't seen it in awhile.

I have a big bronze Herreshoff cleat for my anchor line. No budget for anything else right now.


Sent from my iPhone using Cruisers Sailing Forum

[poiu]

Looks like stress corrosion cracking to me. it is not crevice corrosion as that requires an anoxic environment. A little pit starts, then the crack follows the grain boundary, pulled bigger by stress. It may have been a really sub standard spec steel. Avoid particularly 304 or 316 or other austenitic ss in a moderate load situation (>5% max tensile). Should have been better ss or bronze or much beefier.

[thinwater]

A little critical reading and thumbnail calculation make some statements a little hard to evaluate.

a. A bolt places the part in compression. Obviously not, since we have a tension failure. Moreover, it should be obvious to the casual observer that parts of the cleat are in tension and parts in compression, depending on the load angle.

b. The deck will fail before the cleat. 1/4-inch bolts are rated at ~ 2000#, depending on the grade. If the deck contains large metal inserts or backing plates (quite a few owners think they have no backing when in fact it is in the lay-up) that are larger than the cleat, pulling the cleat out would require the failure of 1-2 square inches of FRP; not likely to happen before the bolts fail.

Also it is quite possible on many tall cleats for a line to place enough tension on a boat to get failure. You can play with the geometry and leverage, considering that the line could be as much as 5x the boat strength. Exceptionally unlikely to happen if the boat is secured in a logical manner. Thus it is important to keep the line close to the deck and avoid vertical loads.

c. No images on-line of failed cleats. The result of weak Google Foo as I found many dozzens. I will agree this type of failure (most catastrophic failures) are rare. And if you Google "cleat pulled from deck" you get zero images.





It seems to me like a subject that could use some basic strength testing.

[Ex-Calif]

Originally Posted by thinwater

A little critical reading and thumbnail calculation make some statements a little hard to evaluate.

a. A bolt places the part in compression. Obviously not, since we have a tension failure. Moreover, it should be obvious to the casual observer that parts of the cleat are in tension and parts in compression, depending on the load angle.

Hey Thinwater. Don't know if you are responding in general or to this specific failure.

If you read the first post he was attaching the cleat with an impact wrench. There were no rope loads.

The failure was tension failure in the countersink caused by weak material and the wedging effect of the countersunk screw. The crack at the upright appears to be bending stress as the cleat was tightened.

Cleat loads are usually shear however my cleats actually mount on the side of the boat and the springs can put the cleat bolts in shear and the breasts can put them in tension.

I actually like these on my boat - there is a large load carrying plate and a duplicate actually a little bigger on the inside. The cleat is actually formed rod and on the inside are nuts.

I reckon the boat has to come apart before this thing fails.

[Auspicious]

Originally Posted by thinwater

a. A bolt places the part in compression. Obviously not, since we have a tension failure. Moreover, it should be obvious to the casual observer that parts of the cleat are in tension and parts in compression, depending on the load angle.

I'm a long way past college strength of materials and structures but I do remember the fundamentals. Clearly the mounting area will be in compression. For anything approximating a horizontal load from dock lines much of the cleat would be in shear. For some horizontal loads I can see a portion of the mounting flanges being in bending (tension and compression across the section).

Originally Posted by thinwater

b. The deck will fail before the cleat.

Originally Posted by thinwater

1/4-inch bolts are rated at ~ 2000#, depending on the grade. If the deck contains large metal inserts or backing plates (quite a few owners think they have no backing when in fact it is in the lay-up) that are larger than the cleat, pulling the cleat out would require the failure of 1-2 square inches of FRP; not likely to happen before the bolts fail.

I've certainly seen cleats ripped out of decks come through the glass shop. Many small to mid size boats to have only fender washers to back cleats.

Originally Posted by thinwater

It seems to me like a subject that could use some basic strength testing.

I would think some Navy or Coast Guard somewhere in the world has done some work on this.

[colemj]

Originally Posted by thinwater

A little critical reading and thumbnail calculation make some statements a little hard to evaluate.

b. The deck will fail before the cleat.

c. No images on-line of failed cleats.

Those two images you posted were not cleats of the OP's design. One was a piece of rotted wood - hardly what I would call applicable here. I have still not seen another example of that 4-bolt design failing. My point was that other posters here have been calling that a bad design.

I was the one who mentioned googling for examples, and I did not say there were none - only meant to imply they were rare.

Strangely, I found more examples of failed decks than failed cleats with a google search - four on just the first page. Perhaps the google-foo is fickle.

Mark

[Cheechako]

I've used the Herreschoff type by various manufacturers over the years on boats to 47 feet. Not had any issues... although as I said earlier I wish they were designed with a little more meat around the bolt holes. Flat head or oval head are fine, the purpose of the countersink is to keep the line from chafing on exposed head bolts.
I've never seen a failed one in service, but have seen a cracked one around the hole. (not mine)
Good point about the decks, even cheap cleats seem to pull holes in decks observing hurricane damaged boats... of course many of the boats were cheap also!