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Broken bow U-bolt

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Broken bow U-bolt

Postby Rocky Mtn Sailor » Wed Jul 30, 2014 8:07 am

Not sure if others have had this happen, but in one month I have had 2 bow U-bolts break. I thought the original one might have been damaged. I replaced it with a shoreline 3500 lb rated U-bolt. The 1997 26X went through another storm anchored on a small lake. I had a chain on a danforth anchor tethered to the bow U-bolt. We checked the boat to ensure it was still ok and found it washed ashore and the U-bolt broken again. Not sure what to do about anchoring again we changed the u-bolt again, & put a tire on the chain to anchor to add some give to the tether. I have also kept the ballast open when anchored to minimize the weight. I am not sure this is the solution, if anyone else has some feedback on why the U-bolt broke I would like to hear it.
We keep the boat anchored over the summer on a small lake near shore in about 3' of water.

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Re: Broken bow U-bolt

Postby kmclemore » Wed Jul 30, 2014 9:34 am

Hmm... that's pretty unusual to break a bow U-bolt. Where are you getting them? Are they made of mild steel or ?? And how tight are you torquing them? Got any photos of the broken bolts? If so, a close up of the actual break area would be very useful.
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Re: Broken bow U-bolt

Postby RussMT » Wed Jul 30, 2014 11:00 am

Rocky Mtn Sailor wrote:I had a chain on a danforth anchor tethered to the bow U-bolt.

No actual anchor line? That could be your problem.

So many things I see wrong here if that's the case.

First, if you have all chain, you have nothing for shock absorption. In a storm, the bow will bounce and you'll jerk that eye bolt and with nothing to absorb the shock, something has to give.

I saw this years ago when a Noreaster ripped through Raritan Bay. 40% of the boats on moorings in the area broke free. Many problems were cited for the cause. During the heavy storm, the boats pitched violently in the waves. Many deck cleats ripped out from the sudden jerking stresses. Others had their pendants cut by bow anchors that came in contact with the bucking bronco boats. Still others found their pendants snap from heat fatigue of the sudden jerking.
What I learned is that the line attaching your boat to the mooring needs to be heavy and protected from contact with bow hardware like anchors etc. Any shock absorbing you can do will help.

The next problem I see with your setup is a danforth anchor. I would not sleep at night with that holding my boat. A 180 degree wind shift will pull that anchor out. It will likely reset, however one day it wont.

Your screen name is "Rocky Mtn Sailor". I sail in the Rockies in Montana. I can tell you we get some wild and dangerous T-Storms in the summer. Last year one came through and ripped our marina docks apart. One section of floating dock broke away carrying boats off until it landed on shore. You need good ground tackle if you are going to keep your boat here. I know people think lakes are small, but our mountains are big and winds get violent.

I don't know how much control you have over your mooring location, but if it were my boat, I'd secure it as best as I can. Three feet of water gives you a lot of options you can do yourself. Our lake levels change throughout the season. My boat is sitting in a slip in 28' of water. By the end of the season it might be 4'

Here is a good article on mooring systems.
http://www.westmarine.com/WestAdvisor/C ... nt-Mooring

If it were my boat in 3 feet of water, I'd jump over the side and screw one of those helix anchors into the bottom and attach all the proper swivels etc. to make a solid attachment. Then I'd have some stretchy line in the equation so it has some give in a bouncy storm.

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Re: Broken bow U-bolt

Postby Tomfoolery » Wed Jul 30, 2014 11:38 am

3 ft of water, and all-chain rode? As Russ said, there's no give in that, even with generous scope, as it'll go bar-straight too readily with that little rode out.

RussMT wrote:The next problem I see with your setup is a danforth anchor. I would not sleep at night with that holding my boat. A 180 degree wind shift will pull that anchor out. It will likely reset, however one day it wont.

And that's another problem, IMO. I'm not a fan of Danforth anchors or their knockoffs. Also as Russ said, with a change in wind direction, they'll break out, but from everything I've ever read about them, the likelihood of resetting is very small if the boat is moving, as they tend to skip along the bottom. Fine for a lunch hook, or in a steady wind and/or steady current where there's little chance of changing orientation, but I wouldn't rely on one for unattended mooring. I'm not sure I'd even trust a next-generation anchor (Rocna, Mantus, or Manson Supreme) for unattended semi-permanent mooring. That's what mooring anchors are for. Or a giant block of concrete, if it's big enough to resist the forces a Mac can generate.

I also don't see where leaving the ballast valve open does anything, since it's below the water level anyway. It might help if the ballast were totally drained, as it makes the boat 1400 lb lighter, but the buoyancy due to hull shape remains, so it will still fetch against the mooring line with waves. But at least the mass will be cut by a third.

Edit: I should add that helical screw mooring anchors are probably the state of the art these days, though I don't know much about them other than that. Worth looking into, though.
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Re: Broken bow U-bolt

Postby RussMT » Wed Jul 30, 2014 12:39 pm

That's true, a danforth will hold well but they don't always reset if caked with mud etc.
I wouldn't use any "temporary" anchor for a mooring. None will be reliable. I don't even like to leave my boat unattended at anchor with a standard anchor. How many stories of captains watching their boat drift away while they were on shore having dinner someplace.

From the link above:
Concrete Blocks: Many boats use 50-gallon drums filled with cement, concrete blocks, auto engine blocks and other types of dead weight. This type provides the least holding power, working on the principle of sheer weight, but is not reliable if pulled out of the bottom. If they drag, they will resist motion with a constant amount of force. Note that concrete loses over half of its weight when submerged in water, so a mooring designed to withstand a 500lb. pull will need 1,000lb. of concrete.

Those helix anchors are less than $100. You can easily self install it in 3' of water. Add some chain, swivel, buoy and rode and for less than $200 you can sleep knowing where your boat is.
http://mushroommoorings.com/helix-mooring-anchor/

Otherwise, I'd pull the boat out of the water if leaving it on the hook by itself.
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Re: Broken bow U-bolt

Postby Rocky Mtn Sailor » Thu Jul 31, 2014 7:24 pm

Thanks for all the input. I do also have a pile anchor, that is use in conjunction with the danforth. Last year I used the pile anchor alone and the wind worked on that one to pull it right out and put the boat on shore. So now I use the pile anchor to hold the boat against the more protected direction near shore. Due to the trees and how close I am to shore the winds and waves will not get excessive. The danforth holds the boat in position from the prevailing winds off the lake. The idea of a heavy cement anchor is good but in Alberta you are not allowed to drop anything in the lake that can't be removed. Where we are is an awesome spot to swim, and we have come across 3 underwater hazards ( homemade anchors) that have been abandoned already.
From the discussion above I do believe and hope that now I have some flex in the tether it will not break anything.

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Re: Broken bow U-bolt

Postby Rocky Mtn Sailor » Sat May 23, 2015 10:48 pm

Just in discussion with some other sailing people in the area, they say I should not be tethered to the U-bolt on the hull but the the cleats on the top. They seem a bit flimsie, is that a correct statement? I just spent $5k on hull repairs from last summer , I would love to know it won't end up on shore again. Any feed back would be appreciated .

Thanks fellow Macgregor sailors
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Re: Broken bow U-bolt

Postby Max Entropy » Sun May 24, 2015 12:03 am

Agreeing with some of the other respondents - it's probably the shock loading on the bolt from the inflexible chain rode that's the problem. What happened to the anchor anyway? If the anchor just skipped along the bottom it's hard to see how that wd cause a break, twice in two different U-bolts; more likely it held well, as did the chain, alas. All you need to hold well, really is a good anchor set and a flexible, shock absorbing rode. To keep the anchor set, attached to the stock a short length of heavy chain, or medium/light chain and a kellet to keep the stock down horizontal, then a reasonable length for the depth of flexible nylon rode and maybe a snubber to absorb shock. It's when an immoveable object meets an irresistible force that something has to give.

Max
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Re: Broken bow U-bolt

Postby seahouse » Sun May 24, 2015 1:00 am

Yeah Rocky M, the deck cleats are much more accessible, and easier to tie a line to, but are not as secure an attachment point as the bow U-bolt is (and there are more than one of them) so that is what is most often used. In an upcoming storm or rough conditions, using the U-bolt will get you a more secure connection in return for the extra inconvenience of attaching to it, though.

The angle of the rode will be more horizontal when using the U-bolt, which might not be significant, and it's easier to use a padlock (chain), or similar on the U-bolt.

Unless there is a special provision, such as a Sampson post, the U-bolt is the most robust attachment point on the boat, particularly when the loads are from a straight ahead (and not sideways) direction. There is sometimes an advantage (less wagging) to being attached off the centreline of the boat when at anchor, but that can be accommodated for in other ways when using the U-bolt as well.

A line attached to the U-bolt is easy to not see, so it would be wise to make it shorter than the length of the boat to avoid fouling the prop.

If using the bow U-bolt to secure a line is what you think needs to be done, and makes you more comfortable, then that is what you should do, especially in light of your experience with past damage, and in spite of what is more conventional-looking to others. Therefore, you know something others who question it don't, and not the other way around. :D

So there "U" have it. :wink:
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Re: Broken bow U-bolt

Postby K9Kampers » Sun May 24, 2015 4:37 am

I use the bow u-bolt only for the trailer winch and as a toe step when climbing onto the bow from the water. My experience with bigger and non-trailerable sailboats has been to secure the anchor or mooring line to the bow cleat(s).

My practice on my Mac anchor / mooring in relatively calm waters is to secure to one of the bow cleats. When the wind / current is of concern, I'll use both bow cleats with a bridle. Also, some moorings I've used have a line / loop much larger than the Mac cleats can take. I make a bridle using a length line that allows double or triple passes from cleat to cleat. The bridle passes thru the mooring line loop which is then at about the same elevation as the bow cleat.

I question using Mac bow cleats for rough service as they are just bolted thru the fiberglass hull. It would be made better by epoxying a wood or steel backing plate to help spread the load.
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Re: Broken bow U-bolt

Postby Norca » Sun May 24, 2015 7:16 am

The U-bolt is plenty strong for a straight pull, but not so much when pulling sideways.
When on a mooring, we have the famous Mac-danse where the boat moves back and forth
and it will bend the U-bolt from side to side eventually breaking it off. (metal fatigue)

For this reson I use the deck cleats to tie up to my mooring and i keep a constant eye on the rope
to check for chafe, but as long as it stay in the anchor roller the wear is minimal.
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Re: Broken bow U-bolt

Postby Spector » Sun May 24, 2015 8:54 am

When I'm on the mooring ball (anchored with 2000 lbs of concrete) my set up has 3 lines coming off a heavy swivel, two lines to the cleats and the third to the bow eye with a rubber snubber.
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Re: Broken bow U-bolt

Postby walt » Sun May 24, 2015 10:48 am

Another angle..

I used to keep my 26S on a mooring at 8600 feet (also Rocky Mountains - see the picture below) and can relate to the forces involved. The 26S likes to do the swing dance and what would happen is that the bow of the boat would swing a little to one side, the boat hull then gets lift and the boat would actually sail forward until the rear swings out and the hull lift stops. The boat drifts/accelerates backwards in the high winds and at some point the painter tightens up and WHAM!!! Then repeat this over and over. It’s the Wham that damages stuff and I ended up having attachments at both the cleats on the deck and the bow U bolt. I think the mooring might be worse than on anchor for stressing things.

I tried the anchor sail in the picture.. my opinion is that they just don’t work if the wind is very shifty like I had to deal with - maybe you also.

The initial instability comes from the mast/boat above water air drag force being forward of the boats underwater center of drag. Also if you watch the dance, the bow of the boat is very much moving all over the place in the oscillation cycle.

This may not sound intuitive.. but what I had experimented with is a underwater drag bucket that was mounted to the bow of the boat - actually to that U bolt. In theory (and I think I also observed this working), the bow drag bucket does two positive things. It moves the boats underwater center of drag forward which helps reduce the instability "gain" plus it also dampens the movement of the bow.

Also along the idea of trying to move the underwater drag forward, having the outboard plus rudder out of the water contribute to this and I think reduced the oscillation. I also was in shallow water with my mooring so the centerboard was either up or mostly up.

Like I said.. this is not really intuitive.. but I think the drag bucket off the bow (front) of the boat plus the outboard and the rudder out of the water did make the most difference. The anchor sail I tried did pretty much nothing but I don’t think it hurt anything so I left it on anyhow.

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Re: Broken bow U-bolt

Postby KootsChewt » Mon Mar 20, 2017 5:14 pm

Spector wrote:When I'm on the mooring ball (anchored with 2000 lbs of concrete) my set up has 3 lines coming off a heavy swivel, two lines to the cleats and the third to the bow eye with a rubber snubber.


Has this worked well for you? Our local marine company suggested that I use a 2,000 lb concrete block that they have 3 connection points on and run a chain up to the mooring buoy. I was planning to get one of those smaller buoys with the stick-up flag to hold the pendant, but from here wasn't sure whether to tie-off to one of the bow cleats, or some kind of locking caribiner to the u-bolt... or... we are total newbies to sailing (or owning a boat this big!), so any information here is helpful.

For context, we are on Kootenay Lake, on the west arm, just to the east of the orange bridge near Nelson. We are fairly sheltered from the howling winds that come from that direction, but we do get some days with sustained 40 km/h wind coming straight down the west arm at us (from the NE), with about 5 km of fetch and whitecaps of a few feet. Other boats are successfully moored along this shoreline already. Gusts probably up to 70 km/h or so during t-storms I would guess.
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Re: Broken bow U-bolt

Postby BOAT » Mon Mar 20, 2017 7:50 pm

Why would you anchor the boat in the water with the trailer towing eye? The trailer eye is designed to keep the boat from moving on the trailer only and also only in one direction only - if you take the towing eye and wrench it to the side it will just break right off - it's not designed to take any stress from side to side.

Why are you not using the anchor cleats? What am I missing here?

I thought all you guys complained about the "Mac Dance" all the time (although it does not seem that bad to me - but it could be that I am used to trailer boats and they ALL dance on the anchor line) which is why you NEVER use the TRAILER eye to anchor the boat because at it dances from side to side it will just rip the towing eye right off! And all other boats that are not "trailer boats" don't even HAVE a towing eye! So go figure where your supposed to tie off the bow anchor on all other boats. Your supposed to tie it off on the bow anchor cleat.

Don't use the towing eye to anchor the boat anymore - you should stop doing that.
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