mushroom eye wear

[coldfoot]

Does anyone have a ballpark estimate for how long it takes for the eye on a mushroom mooring to wear down to the point it should be replaced? I know there's lots of variables, but I think I'm on the light end of the wear spectrum. I put in a 200lb mushroom 7 years ago with about 15 feet of chain, swivel, etc, set in about 5 feet of water with a thick layer of soft muck on the bottom. Had an Oday 25 on it for 20 months total. Protected spot--the chain would probably lift completely out of the muck in southerly gales only. Replaced all the chain two summers ago and the eye looked good, but this summer my boatyard said they pulled and junked it because the eye was gone. Never got to see the gear and am a little suspicious.

[tommays]

3 years would be about the max safe time to check

Scrap metal went CRAZY HIGH this summer about .15 per pound BUT its back down to .1

[sailingdog]

Depends on how heavy the chain is and how often it is pulled taut and moving to abrade the eye of the mushroom anchor. If the bottom chain is heavy enough, there shouldn't be much movement between the chain and the mushroom anchor under normal conditions... so there shouldn't be much wear.

[kgs113]

I thought you were talking about glasses for fungus.

[mgmhead]

Honest to pete... I checked this blog thinking there was a new fad in sunglasses. Mushroom Eyewear indeed.

[Maine Sail]

With properly sized, read very heavy, bottom chain, that is 1.5 times the depth at MHW, there should be little to no wear. I have my old 400 pounder sitting on the dock and it was 8 years old when I went up in mushroom weight, for a new boat, and the eye has almost zero wear.

In 90% of weather the bottom chain is what's holding your boat, if it's sized appropriately. It is my guess that the majority of permanent mooring systems use drastically undersized bottom chain compared to what they should.

If you wore out your mushrooms eye your bottom chain was way to light or you have 30-40 knots fairly regularly..

Unfortunately most areas of the country really don't understand moorings like they should. In Maine we have folks who survive, via a proper mooring, on remote off shore islands, year round. What we know about moorings up here has been learned over decades in severe winter storms.. The bottom chain is but one very important component in a total system that has to work in harmony. If you wore out the eye there was something wrong It was most likely lack of sufficient bottom chain weight.

[paulk]

The eye of a mushroom anchor "wearing out" is not solely due to chafe caused by the anchor chain pulling tight and pulling on it in a once-a season (if that) storm. Even if your mushroom is made of stainless steel, it is subject to corrosion. How fast things corrode depend on a lot of factors. Lots of corrosive stuff can lie on the bottom of even a calm harbor, ready to chew up any sort of metal thrown its way. When our harbor was dredged a few years ago, some of the dredge spoils were so nasty they were required to be transported to a covered landfill for disposal. Salt water isn't known to be inert around ferrous metals either. The eye of the mushroom probably isn't buried deep in the mud, where there's little oxygen to promote oxidation, but is more likely to be lying on top of the harbor bed, in the middle of a constant bath of salt water and myriad corrosive chemicals (fish urine?) and is therefore perhaps even more likely to rust, pit and weaken than other parts of the anchor. Each harbor is different. Ours is so well-protected that over the space of 5 years it is unlikely that the mooring chains have ever been stretched taut. They get changed anyway, because of the corrosion weakening the various parts. It's a lot cheaper to change a mooring than to have to buy a new boat (and pay for the damage to the others the old one did.)

[sailingdog]

Paul-

Yes, but if your bottom chain is too light, the majority of the wear will be due to the friction between the chain and the eye. If the bottom chain is sized large enough so that it generally isn't moving, the zinc galvanization layer on the eye lasts much longer and the corrosion takes place much more slowly.

[paulk]

My point, like Tommay's, is that chafe is not the sole cause of "wear" on a mushroom's eye. I see many mushrooms that have had their stocks cut shorter and new eyes welded on because of corrosion on the end that sticks up out of the protective (non-oxygenated) mud, in situations like our harbor in which wear from chafe, even with light chain, would be next to impossible.