Check your mast base fasteners before lowering your mast

[David Patterson]

My mast base separated from the mast while lowering the mast for transport. No fun, but no real damage to speak of (a bent stanchion, a twisted forestay, and a few moments of cardiac acceleration). I was fortunate. On inspection I found that only one of the four machine screws holding the base and mast together was intact, the forward one, and it sheared when the strain was the greatest. My 1982 25D (#85) is new to me since a year ago, and this was the first time to lower the mast. I naively assumed the base was okay, not even knowing what to inspect, really. The pre-purchase survey missed the situation with the base, even though only one screw head would have been visible. If you have an older Cape Dory (and aren't they all?) consider inspecting the base's machine screws before raising or lowering the stick.

[Terry]

Glad you weren't injured. Thanks for the warning, too.

Regards, Terry

[rollo_cd26]

David,

You may want to post a picture of the base and the failure point. I am getting ready to test rig my 1988 26D for practice and identify any issues prior to spring 2012 launch. Your experience is particularly interesting to me, since I will be hoisting the mast up and down on the same day.

[barfwinkle]

Rollo

Are you using a crane or some kind of gen pole setup?

Fair Winds

[Steve Zwicky]

David, I'm also interested in seeing a pic of the base. I assume there's a knuckle/hook of some sort to hold the mast in place. Thanks, Steve

[David Patterson]

Sorry, I'm still back in the film age so no quick photo. I'll try to get one of my kids to help me out. The end cap of the mast, the actual base, is bolted to a heavy (5/16th inch?) stainless steel hinge, probably a one-off fabrication by the original owner in the shop of the local plutonium bomb-trigger plant, Rocky Flats, where I think he worked (our tax dollars in use?) The end cap itself is conventional for a Spartan spar, made to insert into the mast tube. It is designed to be held in place with a machine screw on each side, including one hidden in the track right above the drain hole. The PO told me my boat went through a hurricane in the Gulf of Cortez and "could take more than I could." Did the first three screws fail then, or during mast raising and lowering? May be simplest for an owner to back out the screws, one at a time, inspect and then replace them. I was using a stable gin pole arrangement when that last screw gave way, and was off to the side as the mast fell, tailing on the tackle I was using. A slow motion event, very fortunate.

[barfwinkle]

Good morning David

As I read your description it seems to me that the screws that hold the mast "shoe" (what fits in the mast tube) to the hinge failed? I have the same setup on Rhapsody and those screws are easily replaced when the mast is down.

The mate to the hinge top is through bolted and those four screws can also be checked but it a bit more of a chore and requires re-bedding the hinge base.

If the mast was up during the hurricane, then it is very unlikely that they were damaged during a storm. More likely they corroded and snapped as a result of multiple raising and lowerings.

This should be a fairly simple fix. Remove the shoe from the mast and replace the screws that hold it to the hinge. If I recall I used 1/4" x 1/2" or 3/4" (length) screws. You can't use too long of a screw of the hinge wont close all the way. Here is the best pic I can find and it shows the hinge in place and if you look you can see the base of the mast shoe.

Hope this helps.

[David Patterson]

No, Bill, the "shoe" (which I have been calling the "mast base" or "end cap") connection to the hinge plate is secured by six 1/4" bolts. No problems there. Rather it was the screws that pin the shoe into the end of the mast. Seems to me that a great amount of force was required to compromise them, or more likely a great amount of repetitive motion, with the mast section itself acting as a shear force on them. They seem typical stainless steel to me as I look at them. In your photo the port and forward screws on the sides of your mast are visible. They would be easy to back out for inspection. The shoe-to-hinged-piece bolts would require the mast to be down to inspect, with the shoe removed. By the way, does your mast hinge forward or back? Bruce Bingham, in his Sailor's Sketchbook, illustrates a simple and rationally controlled way to lower the mast forward using a longer main sheet, and the boom as the leverage. I am searching for a replacement for my mast base hinge that would allow use of his method. Know of any sources? I'll try Rigrite soon.

[barfwinkle]

David personally I would (did) use Dwyer Mast! I dont recall the part number. It'll take a couple of decades to get it from RigRite. Search this Board for rigrite.

Good luck & I'll check those screws before dropping the stick.

Fair winds.

[David Patterson]

Oops, it was the starboard screw most visible in your photo, Bill, not the port one. A sailor's joke I heard recently: the first mate of a cargo ship would watch the captain perform a ritual each morning. The Old Man would unlock a drawer, stare into it for a long and serious moment, then re-lock it. Every day. The mate, of course, was intensely curious, coming up with a variety of explanations for the odd behavior. After some prolonged years the Old Man finally retired, and the mate ascended. Following a full day of fresh duties the new captain eventually got a chance to unlock and open that mysterious drawer. Taped in the bottom was a single sheet of paper. On it he read...PORT = LEFT; STARBOARD = RIGHT!!

[Duncan]

No, Bill, the "shoe" (which I have been calling the "mast base" or "end cap") connection to the hinge plate is secured by six 1/4" bolts. No problems there. Rather it was the screws that pin the shoe into the end of the mast. Seems to me that a great amount of force was required to compromise them, or more likely a great amount of repetitive motion, with the mast section itself acting as a shear force on them.

I have been puzzled by the terminology in this discussion, as well as by the diagnosis of the accident.

The part you are referring to is generally known as the mast step. The process of raising or lowering the mast is often described as "stepping" or "unstepping" the mast. Here is the part description, for the CD 25D, from the RigRite web site

CD-3.5 Mast Step, Deck-Mount: SP-459:
Mast Step for CD-3.5 Mast Section fastens to deck, keelson, or to K-1374 Mast Hinge Assembly for use as tabernacle. Features drainage channel to prevent water build-up inside the mast. Base is (maximum) 5 1/8" long x 3 7/8" wide and projects 1 3/4" into Mast, unit attaches to deck with (4) 1/4" bolts. Cast in 356 Aluminum with clear anodized finish. LINK

This part fits snugly inside the mast section. It is difficult for it to slip out, especially because it "projects 1 3/4" into Mast". There is no mention of screws securing the mast step to the mast, since they usually aren't necessary or desirable.

If the mast is kept under control, there shouldn't be any appreciable shear force operating on the mast step. The mast and the step are initially in compression, of course. As the mast descends to a more horizontal position, shear force should be alleviated by the tilting of the mast hinge, and by making sure the mast doesn't twist or sway.

This suggests various other causes for the accident, such as:

1) An incorrect mast step being fitted to the mast and hinge

2) A corroded mast step, thus loosening the fit and possibly reducing the penetration of the step into the mast. (My mast step, of very similar design on a 27. has now corroded to the point of needing replacement before the mast goes up again next spring).

3) The mast hinge was either not released or was jammed or twisted in the process of lowering

4) Most importantly, though, it is much safer to have someone stationed at the mast base during the lowering process, to control it. The fact that the mast got loose and caused damage suggests that it was not in control during the lowering.

It is certainly possible to lower a hinged mast single-handed, but it's safer to have a helper standing by at the base.

[David Patterson]

Duncan notes:
1) An incorrect mast step being fitted to the mast and hinge

2) A corroded mast step, thus loosening the fit and possibly reducing the penetration of the step into the mast. (My mast step, of very similar design on a 27. has now corroded to the point of needing replacement before the mast goes up again next spring).

3) The mast hinge was either not released or was jammed or twisted in the process of lowering

4) Most importantly, though, it is much safer to have someone stationed at the mast base during the lowering process, to control it. The fact that the mast got loose and caused damage suggests that it was not in control during the lowering.

Three parts to the boat end of the mast: the extruded tube of the mast, with the fitting that Dwyer calls the mast step, and the step hinge. The step hinge is bolted to the cabin top and to the mast step. The mast step is (usually) pinned to the end of the mast tube with machine screws. My 25D original equipment step is uncorroded, and enters the mast tube for 1.5 inches. My mast hinge was working properly, neither jammed nor unreleased. Given my recent experience, I wouldn't have my step simply inserted into the tube without a method of keeping it there. I will carefully examine the screws in the step each time I raise or lower my mast in the future. That way, whether there is help available or not (and there often is not for me), the base of my mast won't get out of control again. That is, of course, what happened...the base did get out of control as the last functioning machine screw broke. Someone at the mast base may have shouted out a warning but could not have halted the tube's separation from the step and hinge. As for the raising and lowering, my future guide will be Bruce Bingham's carefully thought out method in his Sailor's Sketchbook. Duncan's observations and cautions are spot on. Thanks for the clarification of terminology.

[Duncan]

David

I'm glad you found my comments helped. I want to just re-emphasize that you should NOT rely on screws into your mast step, but try hard to line up a helper at the mast base. The mast hinge is not designed to hold or steady the mast, it is just there to eliminate the need for a crane.

I've seen a lot of problems stepping and unstepping masts, and I have one friend whose knee was almost destroyed in an accident. He has a foot-long scar from the surgery and walks with a limp.

The screws you are talking about are definitely a non-standard way to secure a mast and CANNOT BE RELIED UPON to keep the mast under control.

Just think about how easy it would be to twist off a little screw, when you have a big heavy 30 foot lever to do it with.

Just a word to the wise, ok?

[David Patterson]

I'll take your experiences as a word from the wise, Duncan, and add them to my own recent close miss.