Disclosures: I do not know Greg personally and have no affiliation or financial interest in his company or the success thereof. Greg of Mantus anchors did offer me the anchor which I bought at a "pro-deal" deep discount on the condition that I post my results, good or bad, here on sailnet.
I had hoped to have the Mantus out for a true sea trial several times by now, but there is something about the birth of your first child that will slow down your boating season. Slow, I say, but not stop! We just got back from our first overnight boat trip (2 nights) with the 5 week old. For details about the kid part I'll be posting in the Cruising With Kids section of Sailnet here shortly.
Back to the anchor. Having read Maine_Sail's account of the Mantus grabbing on short scope, I thought I would try and replicate this with my experiment. The plan, with kiddo on board, was to go somewhere familiar which actually has very good holding. Since the holding is good and the wind forecast for only 10-15knots I figured we wouldn't be stressing the anchor so I might as well try the short scope thing.
Turns out I was wrong about not stressing the anchor.....
Here is our destination. Sucia island, which is my favorite boating destination. The "X" marks where we dropped the hook and (happily) where we found ourselves 2 days later. The circle is to help you find the "M" for "Mud" bottom type. The mud itself (for you connoisseurs of) is a pretty sticky and dark but not smelly. It is harder than "soft mud" and will stick to some anchors but it is not clay like and gravity will make it fall off the anchor usually. If you stick your finger in it leaves an impression and it is mixed with a few small shells.
It was a windless trip up but I was able to take some Mantus-eye-view photos from the bowsprit. This picture is a reflection of my boat as it is underway. (note the brown stuff around the anchor bolts is the manufacturer's supplied grease - not rust. Mantus has apparently already changed the color of the grease so that it doesn't look like rust!
On the way to Sucia:
Now the details. We chose a spot where the depth sounder read 35ft. Mine is 2ft below the waterline and my roller is 8 feet above the waterline. That makes our depth (for the purposes of calculating scope) 45ft. I had attempted to hit a round number with regard to scope but ended up with 100ft out give or take a foot. We have 3/8 BBB chain of 280ft length and (later) I attached our 15ft (non-stretchy) bridle which is at the waterline.
So lets see.... 100ft of scope out devided by 45 = 2.22222:1 ratio, or in round numbers 2.2 : 1 scope
How's my math so far? Good?
Okay. We backed up much quicker than normal and low and behold it set as soon as the slack was taken up. I'd say it is likely it set right where we dropped it. We proceeded to back up to an engine RPM of 3200 which is about 35HP at the prop plus there was 10kts of wind helping add some force. This stretched the chain out to an angle that was pretty far.
I also refrained from raising the mizzen for a while and allowed the bow to get blown off in the wind. This presents the boat at about a 60deg angle broadside to the wind before snatching back and "tacking" to the other side. The Mantus held fine at this scope. We stood broadside in the 10-12kts tacking back and forth for about 20minutes on the short scope. The Mantus held fine.
After "testing" the anchor I put out 160ft of chain and attached my bridle (which is right at the waterline) for the night. I also raised out 150sqft mizzen.
My scope overnight would be as follows: 160 (ft of chain) devided by 37 (remember my transducer is mounted 2ft below the waterline and was reading 35) for a total scope of 4.3:1
. Now here's the part where I'm a bit embarrased. I made a mental math error when letting out the chain. I was actually shooting for my next chain mark which is 200ft and would have given me the 5:1 that I usually shoot for. Another reason that lots of scope is good I guess because it allows for math errors.
I had expected that this would be the only real test but I was to be proven wrong. We ended up having the windiest night we have ever experienced at Sucia! It is a very protected harbor but in the harbor my wind meter was reading sustained winds of 15-18 with gusts up into the high 20s. The wind was late at night and I wasn't awake or watching the wind gauge for many of the gusts but we both estimate they were right around 30knots and they varied in direction by about 90deg or so sometimes causing us to heel sharply.
Sure enough the Mantus held us firmly in place with 15kts gusting 30kts from varying wind angles with just over 4:1 scope on a good holding bottom. The second day and night had less than 10kts of wind and wasn't an issue.
Retrieval was not difficult. It was obvious when the chain was vertical and I had to use the low gear in the windlass to break it free, but it did break free. I was pleased to see that it didn't bring up half the bottom as many Rocnas have been shown to do. Some people like that their Rocna brings up half the bottom because if makes them feel confident that the anchor dug in well. For me, it's poor design. Staying put is proof that the anchor was dug in and the extra mud is extra weight and strain on gear to haul up. This is particularly bad if bringing it up by hand.
The mantus came up with mud forward of the attachment of the shank but all the mud "aft" of it was gone. I expect from the shape that this will usually be the case, meaning a moderate amount of mud will be attached. My fortress and Bruce also bring up some mud (but not loads of it) from this anchorage.
The mud on the "ears" and hoop attachment bolts mean it was likely buried all the way in the mud. Of course holding my 30,000lb boat on 30kts would also imply this...
So far I'm impressed with the short scope setting ability. Holding power is either adequate or you're on the rocks. So far the holding power was adequate, especially considering the gusts to 30kts and the fact that my scope was shorter than expected.
I haven't yet tested one of its claimed features which is that it will set where others won't. When I get a chance to try it in a couple difficult anchorages I'll post those results here as well.