There’s a crack in my mast

[donradcliffe]

There appears to be no load on the crack. I would smear some epoxy in it to stop further corrosion from widening it, and go sailing. The interior corrosion may be from standing water inside the mast, so I would drill a couple of weep holes at the bottom.

[MicHughV]

My question is...how or what made the crack appear there, and again.....is it a crack or a bad weld....ie, insufficient penetration or something ? I tend to think that bottom plate was welded on. Would also like to know how long this crack has made it's presence known. Weeks, months, years ????

We've only seen pics of once side of the mast. What does the other side look like ?

Really need to see both sides before jumping to conclusions.

[Cheechako]

Originally Posted by LalaSS34

Hi all

New to the forum and currently working on my first boat - a Sparkman Stephens 34 that’s already double circumnavigated but is very much stuck on concrete at the moment

Upon getting the mast down I’ve noticed an ominous looking crack at the base

Looking into getting it welded, but how critical would you say it is?

You dont have to sleeve the inside, you can put a doubler on the outside with structural epoxy and lots of rivets.
Not a job for the amatuer much though as you need to bend the doubler to fit the curve. Or if you can find a chunk of a mast that is close to the same shape, then cut that to fit.

I had this done by 'Chesapeake Rigging' on the furling mast for my 47 footer. It looked great when done. They had used a partial piece of near identical mast extrusion and cut it to shape as a doubler and it fit intimately with the old mast. I think they got it from the extruders. Smooth edges and all was repainted as I had them rebuilding my mast. (Although people asked if I had broken my mast!)

The idiots who originally made the mast cut the big rectangle out for the in-mast furling spool leaving sharp corners on the cutout. Years later it was starting to crack a little at each corner of the cutout.

[psk125]

Originally Posted by hpeer

I was assuming, perhaps wrongly, there was a tube or bushing inside the mast.

Something more than just a hole in the mast. My 33’er has a tube.

I hat puzzles me is why BOTH a pin and a shoe? Unless the ahoe was alowed to slide. But that seems odd.

The photo does make it appear that there is a tube through the mast. Would it make sense to remove the tube, insert the sleeve, drill it and then replace the tube?

Getting the shoe off would enable a more thorough inspection for corrosion inside the mast. There might be a good deal of it if the shoe was holding water in the heel of the mast for any long period.

[LalaSS34]

Appreciate the input. Sharing more pics of other side and base. Previous owner passed away so has been sitting on hard 7yrs.

From your replies i gather: it is the shoe weld, it exists for quick dropping mast - WA design.
Shoe does not take much load. Pin is more important but having felt inside feels smooth. Rest of mast ok.

Options are either
- epoxy to stop spread
Or
- fit some form of sleeve from aluminium or even carbon fibre, then epoxy + rivet

[Tin Tin]

Yes looking at zoom in on the orange pivot it looks like re-enforced plates above it to take most of the load. The heel looks a like a crack in the weld and probably occurred when lowering whilst underway.

[MicHughV]

I'd say give it a go....I don't see anything that much out of whack here, besides some wear and tear.
Certainly, I'd epoxy fill all the little dips and doodles to prevent further damage and paint over, then just keep an eye on it.

[deblen]

Suggest you drill hole at ends of crack to help stop it spreading.

[Amouage]

My recommendation is that you do a full inspection of your rig. The mast has significant pitting corrosion issues and a crack at the base. You are running a severe risk of being dismasted when loads are increasing.

Welding is not a good option due to the pitting corrosion. Epoxy either….then its better to look the other way. I am a structural and materials engineer and do not think that since the mast is keel stepped you’re not running a risk. At the bottom end you have a lot of pressure (P=FxA) and A is long at the mast end.

Dismasting can cause a significant distress situation whilst at sea. Get it replaced.

[MicHughV]

The mast does not bear on the bottom plate...it bears on the pivot pin...where the mast walls are thickened.
Whether the bottom plate gets welded or not is immaterial.
The mast is not keel stepped either...it is deck stepped.

[hpeer]

Originally Posted by MicHughV

The mast does not bear on the bottom plate...it bears on the pivot pin...where the mast walls are thickened.
Whether the bottom plate gets welded or not is immaterial.
The mast is not keel stepped either...it is deck stepped.

From what I can see this is correct.

Again from what we can see the corrosion is NOT bad around the pivot tube.

It is had to fathom the purpose of the shoe. Perhaps the boat came originally deck stepped and was modified for the pivot. That could be concerning as the pivot construction may, or may NOT, be adequate to take the load. Although the mounting looks pretty stout and history would seem to indicate success.

If the pivot is adequately designed and up to the task you could cut off the bottom 6 inches of mast and never know the difference.

But there is no way for us here to be 100% sure.

[Amouage]

Originally Posted by MicHughV

The mast is not keel stepped either...it is deck stepped.

You're right.

Considering the state of the aluminium around base of the mast and the pivot pin, I would not rely on it. Its your rig and dismasting.....no need to explain.

[Sun and Moon]

what material is the pivot sleeve made from? Could the corrosion be galvanic corrosion from dissimilar metals?

[MicHughV]

You'll note that the rear portion of "shoe" plate is "angled" up on the rear side of the mast.....the side with the sail slot groove.
That "angle" is there to accommodate the rotation of the mast in a rearward fashion.

Without that "angle", you would not be able to rotate the mast as the shoe would catch on the mast tabernacle floor.

To Amouage, this is not my boat, merely what I see.
But seeing as you are throwing out credentials, I'll add mine to the thread.
Though this is neither here nor there, besides other skills, I'm a licensed Professional Engineer and my focus (and my career) for the past 40 odd years has been that of a structural marine engineer. Though I am retired now, I keep my Pr. Eng. license current.

Other photo's (bottom right photo above) seem to indicate the flat portion, but not the angled portion, of the shoe is also somewhat corroded or scuffed up. This would seem to suggest that when the mast is upright, the flat portion is bearing in the inside of the tabernacle, but without being there, this is difficult to ascertain. My gut feeling is that it does not provide any bearing, but probably is located very close to the bottom of the tabernacle, where it likely sits in a puddle of salt water and/or rainwater.

The photo (upper right above) also show what appears to be countersunk rivet head just below and to the right of the pivot tube. Exactly what this does, I'm not sure, but would be inclined to think it is something to keep the pivot tube locked in place, or prevent rotation.

With a bit more dimensional information, I could throw this in my AutoCad program and determine this exactly to the nth degree.

All that aside, as pointed out above by hpeer, without actually being there, it is difficult to be 100% sure, so just giving my 2c here.

[hpeer]

Well fancy that, I too am a retired Professional Engineer. But Electrical so you have me beat here. LOL.