Cracked Mast Step

[James Moore]

Hi,

I have a 1978 C&C 34 sailboat. I race it pretty regularly. Last night as I was shifting the mast to try to improve performance I noticed that the mast step had a crack in it. The crack appears to go completely across its width but the mast is in so I can't tell for sure. The crack is full of dirt and stuff so it doesn't look like it occurred recently.

I'm guessing this crack is not a good thing and I should get the mast step replaced. It appears to be made of aluminum. I have a few questions for you folks:

1. What kind of risk am I looking at due to this crack? Can I keep sailing this season and address the problem in the winter?

2. Am I looking at an expensive repair job? What kind of structure is the step attached to?

I look forward to your advice.

[Frosty]

Is the mast above a compression post? Have you any water leaks beneath the cracked step? Do bolts attach it to the deck and if so are there bolts in both halfs? Any pics?

The main thing is if there are bolts through both, are you sure its a crack and not a two part construction.

[James Moore]

Thanks for the reply!

I do not know if the mast is above a compression post. The C&C 34's mast goes through a collar in the deck and the step is in the sole above the front of the keel.

Regarding water leaks - there was one day early in the season where I appeared to be shipping in water. The bilge had filled to the floor boards when we noticed it just before a race. We pumped it out (I discovered at that time that the float switch was not functioning - since replaced) and it stopped by race start and has never occurred again. The shipping of water occurred immediately after a fast 20 min. transit under power to pick up a racer. I suspected the stuffing box at the time but after observation of it I've seen no evidence of leaks. The source remains a mystery and it has occurred to me that it may be related to the cracked mast step but one would think a leak would reoccur. I am also unsure of the design and whether it is likely this would be a leak point. Are there any 'attachments' between the mast step and keel? (i.e. does a keel bolt pass through a mast step to the keel?) The crack looks pretty jagged so I don't think it is a two part construction. I'm sorry but I don't have any pictures yet. Next Tuesday I'll be back at the boat and I'll try to get something then.

I'm sitting on the fence right now regarding the danger of the crack and any designers input may help. On the one hand I think that the crack could lead to catastrophic failure as the pressure forward or aft could cause the foot of the mast to slip ripping the mast step apart and the rig to come tumbling down. On the other hand the shrouds, forestay and backstay all pull the mast down and the rotation forces would have to be awfully great for the mast to move at the foot. I was trying to move the mast when I noticed the crack. I had loosened everything and I was trying to shift the mast forward at the foot to get the sail plan back in an attempt to improve performance. We were using a large wrench to pry it while kicking at it to shift it. We can move it a few inches but it wouldn't go as far forward as we wanted. I'm wondering if all the prying caused the crack...

I'm just a guy with a boat so I don't really understand the forces at work so anyone's input is appreciated.

[PAR]

The collar the mast sits in is bolted to the support grid below, which transmits the compression loads to the hull for dispersal. If the collar is cracked, the heel of the mast can move around, which will not make your day when trying to harden up for a heavy slosh to windward. That collar is all that keeps the heel of the stick in place. Generally you can adjust rake at the partners (where it goes through the deck) by shimming fore or aft as desired. Moving the step wouldn't be my recommendation as the structure below needs to be in alignment with the mast column above. Look it hasn't fallen down, so you're in luck.

Yep, you'll have to yank the stick, remove and replace the step and inspect the bolt holes for elongation, indicating the loads have moved the pieces around enough to "egg" out the holes. If this is so, the holes will need repair too.

It's not that bad of a job, though pulling the pole can be intimidating.

[James Moore]

Actually we pull the stick each winter so I'm not too worried about that. I'm just wondering if I can wait until then to address the problem.

There are no cracks at the collar - all seems fine there. The metal plate of the mast step is cracked. It is a similar problem to what this person had. These are NOT pictures of my boat but his problem seems similar to mine

http://www.wbryant.com/StellaBoat/Pr...p/maststep.htm

I race in a one design fleet and a favored approach to rigging the boat is to shim the mast aft at the collar and forward at the foot. There really isn't too much room in the step to shift it about at the foot - about two inches and about three inches at the collar. Then some backstay is applied to give some prebend. More backstay is applied as one points and/or wind velocity increases.

[messabout]

Hard to tell whether you have a catastrophe in the making. I would regard this as a serious problem. If not you have missed a race or two. If it is serious, there is more danger than merely losing the rig. Personal injury is not out of the question. Better safe than sorry.

[alan white]

It might make sense to do two things: Drill stress relief holes at the ends of the crack, and add plate (s) to the top of the step to temporarily mend it.
If this is a "rest-of-season" thing, mild steel will do. Drill and thread the aluminum to accept stainless 1/4" screws and attach the plate (s) and sort it all out later in the fall.
If the plate has fractured, I would consider replacing it with a stronger thicker one, just common sense.
Maybe avoid spinnakers and big gennys, over-canvassing, etc. until you can do a proper repair.

Alan

[James Moore]

I've attached a photo of the crack.

Last Tuesday I consulted a few folks at the yacht club. One chap had suggested, like you Alan, that I attach a piece of metal as a 'band-aid' solution. I then talked with the head rigger and showed him the picture. His opinion was that screwing in a piece of metal wouldn't really help at all given that the forces involved would overwhelm the screws pretty quickly if a failure were to happen. He seemed more concerned with what had happened to cause the crack. He asked if I''d run aground. I did bounce off a rock a year ago....

He also expressed some concern as to the structural integrity underneath the step. In short he thought that it is unlikely it would fail just racing around the buoys in the harbour but high winds and heavy seas might be more of a concern. He suggested I take a good look at it under sail and see if I can detect any movement - shifting or flexing being a bad thing.

I did take a look at it under sail and while tacking and nothing seemed to move or flex though it was a pretty light air day. I'll keep checking it but I hope to replace it at seasons end.

[alan white]

I'd almost guarantee the damage was from a gounding, the keel punching up, maybe cracking it initially. Have you checked your floors also? A lot of times floors turn to mush under all that glass, especially when they are drilled through to run things. The mast makes a nice slow spigot to supply the water. Then the boat settles around the keel when layed up for winter, especially if its a relatively flat bottom.

Mast support at the step is almost entirely compression. I had a deck-stepped mast that initially sat in a 1/4" pocket, which required tight stays for sure (once it popped out, but I caught it and pulled it back in). I carry 155 sq ft of sail (keel boat). I have since extended the mast to the sole, and it sits in a 1" deep pocket.
Lateral loads are very small. Sailing out the season, it is inconceivable that anything short of a rigging failure would test the lateral component. The mast can't go up or down, so I wouldn't worry too much. But you may indeed have some structural issues below and to the sides of the step. not expensive, but time consuming if you do the work. Good yime to look at the other floors too.

Alan

[James Moore]

Thanks for the advice Alan!

[fiberglass jack]

where in T.O is the boat. I will be at R.C.Y.C tommorrow afternoon

[James Moore]

It is at the RCYC. Unfortunately I wasn't on Sunday. I take it you know a fair bit about this stuff Fiberglass Jack? Do you do the work as well?

[fiberglass jack]

Yes I do that type of repair, I will need to see the damage to see what needs to be done, I will be working on a J boat at RCYC yard at Parlament street on friday if you like we could arrange to have a look at your boat this coming Friday or on the weekend,