Bent mast

[Chip Hindes]

I thought about recommending a sleeve or a solid insert, but decided against it. It wouldn't work right unless it fit almost perfectly; you'd have a hard time finding one which fit almost perfectly unless you made it yourself. A sleeve couldn't interfere with the sail track, so it would have to wrap around only partially. Making it yourself wouldn't be free. It woud add to weight aloft.

Personally, I wouldn't consider any alteration or repair to the stock mast a value adder; as far as I'm concerned everytihng would be a negative. A new mast would be an adder.

[Frank C]

Prolly all wet here, but I thought I'd take a 5-foot length of spare mast, remove the track, split it lengthwise (fore-to-aft, of course) and trim as necessary. Now it's in two identical halves that can clamp around the original mast as a reinforcing jacket - likely held by 3 or 4 through-bolts.

OR;

Could one split the mast-jacket up the backside only? ... then gently spread it open to slip around the front of the main (repaired) mast, and & clamp around it? I'm thinking that's too wide to open it and then close it again.

[Catigale]

Chop off that bent section of mast and mount it in the back for a yawl configuration.....now thats a MOD!!!

[Chip Hindes]

Frank: The inside shape is different from the outside shape by at least the thickness of the section, so you wouldn't know if either of your suggested methods would work satisfactorily until you tried it. It's been awhile; do I recall from those Mac drawings which somebody discovered that the material thckness was not uniform around the periphery? Seems like it might have been thicker on the forward edge than the sides. That may be my imagination hard at work.

You're going to have to cut out part of the mast at the bend or break, so unless the cutout part can be limited to only an inch or so two, or you're prepared to go with a shorter mast by however much you have to cut out plus the patch sleeve, and shorter or relocated shrouds, forestay and backstay, you'll actually need three original, continuous, unbent and unbroken interior pieces totalling the original length. Also, one sleeve long enough to bridge all three pieces plus overlap, or two separate, shorter sleeves.

In order to work properly, the sail track in your repaired sections has to be continuous (no gaps) line up pretty well, maintain that alignment under static and wind loads, and be without kinks or gaps which would prevent you from passing either the bolt rope or sail slugs past it without damage.

So to end up with something the original length plus the sleeve, you need either a second broken donor mast, or an additional original piece of mast extrusion. Perhaps a shorter length is obtainable through the factory, or the original extrusion house (though I would guess from experieince there's a good chance that's in China).

Keep in mind that whatever you do to an existing original mast section to make a sleeve, splitting it both fore and aft, or aft only, it will never be as strong as an original, unsplit mast section, so you're accepting right up front that the repaired section will be somewhat weaker than the original.

In fact, I'm thinking your method number 1 would compromise the strength too much for comfort.

Regarding your method number 2, I was picturing that you would have a wraparound section that would would simply slide on from the top or the bottom. Aluminum is not ductile like steel and I don't believe a piece of mast section would take well to being spread that far apart without doing permanent damage.

Also, I think it would be difficult to try to fasten it only by bolting through the thickest part of the section; not only would this not spread the load adquately, and particularly if you spread it using the wraparound method the aft edges would not fit tightly but would bow out like a couple of spring wings, ready to grab and/or cut halyards, sails etcetera.

Even with all the above negativity, I have a specific scenario in which I think a repair might be warranted and a suggested best method, but this is already too long and I have to leave right now to do some real work. I'll share my additional thoughts in part two; stay tuned.

[Frank C]

I'd avoid shortening the mast at all costs - too much trouble as you cited, especially fairing the mast track and dealing with shroud lengths. I was thinking of a sleeve or jacket only as added reinforcement of the section that suffered the bend, after it has been re-straightened.

I never thought of the variable wall thickness, but if it varies as many boom sections I've studied (like .075 to .090), that seems less a problem. I also never thought of sliding the sleeve over the end - solves that problem. No.2 is clearly the better approach since it maintains integrity in the forward section (270* around the nose of the mast). Unless the inate wall thickness simply PREVENTS a nice tight fit, in which case splitting into two halves might still do an acceptable job .... and would it be a reasonable upgrade BEFORE suffering such a mast bend??

All accounts I recall of mast failure have occurred at the spreaders (~12' above deck), with the mast top falling aft, or to the side. The spreaders are clearly pushing it to failure. I felt that a sleeve along that mast segment, say from 10' up to 15' - that would be the target area for a double-thickness - also, that's likely where most bends occur.

I know, I know ... the engineer's next question is, "Once you reinforce this primary failure mode, now exactly where have you transferred it to?"

[Chip Hindes]

You got that right.

Obviously the point stress loads at the spreaders are the most probable failure point, but that's almost certainly the same for every boat with spreaders.

The idea of the possibility of repair beings to mind a friend who had an unfortunate encounter with a mast eating crane while the boat was on the trailer at Homestead, on launch day for Bimini I. He simply detached the mast, threw it under the trailer, and made the trip as a powerboat. Possibly a jury rig repair would have worked. I never got a good look, but the mast was toast anyway so it couldn't have hurt to try. Possibly he could have cut the top off to use as a sleeve, and as long as he had a full length forestay he could have run the full genny with reefed main.

He may have had some broken shrouds, which would have made it tougher; possibly it was too damaged to do anything but exactly what he did.

My plan for attaching the sleeves is to drill for and set several rows of aluminum pop rivets, and a two part epoxy filling the interface between the original mast section and the sleeve. Mix and spread it on thick so it squeezes out as you set the rivets.

[Frank C]

... but the mast was toast anyway so it couldn't have hurt to try. Possibly he could have cut the top off to use as a sleeve, and ... could have run the full genny with reefed main.

My plan for attaching the sleeves is to drill for and set several rows of aluminum pop rivets, and a two part epoxy filling the interface ...

Nice plan for affixing a sleeve ... wonder if Bill realizes we just solved his problem!

The magic words are underscored. A simple little experiment would reveal whether a sleeve would slide onto a mast and yield acceptable mating interface - uniformly tight. And, it remains to be seen how tough a job to remove the track and split the mast sleeve's spine.

• Upon reflection it seems not too difficult to fabricate a mast sleeve (assuming I could locate a scrap mast). I'd try to remove the track AND split the spine simultaneously ... i.e. by making two long cuts, one along each aft-side of the scrap mast, just below the track. That should leave me a ~340-deg. mast section with an inch-wide gap down the back of the sleeve, where the track used to be.

If all the above details worked out okay, I'd try straightening a bent mast. But I'd be reluctant to use a mast after it was bent (like the one pictured, for example) without adding a reinforcing sleeve - especially since the mast mid-section has a clearly demonstrated history of failures. Considering Rich's original estimates (around $750, predrilled?) I think it's worth a weekend's effort.

If a sleeve could be made that fits snugly, I really do believe the result might end up stronger than factory-issue. Of course the devil's in the details. You'd need to remove all that mid-mast stuff like spreader brackets, steamer light, and HOPE to re-drill blindly through the sleeve to find the same attachment holes !@! ... Nonetheless, next 5-foot scrap of Mac-mast I find is goin' under that aft berth!

... would it be a reasonable upgrade BEFORE suffering such a mast bend??

[Bill at BOATS 4 SAIL]

If you're going to "drill for and set several rows of aluminum pop rivets", I think you should stagger the holes so you don't have a potential fault line along a row.

How do I make a quote without having to type it in?

[Tony D-26X_SusieQ]

How do I make a quote without having to type it in?

Bill,
All you have to do is click on the "Quote" balloon in the upper right corner of the message box where you want to extract the quote. You then can edit the contents. Remove what you don't want. Don't remove anything in brackets at the front and end of the quote.

[Bill at BOATS 4 SAIL]

"All you have to do is click on the "Quote" balloon in the upper right corner of the message box where you want to extract the quote."

Thanks - I would hit REPLY first and then couldn't figure out what to do.

How do I do the white box around a quote?

[LOUIS B HOLUB]

How do I do the white box around a quote?[/quote]

Bill...keep trying...its easy...

[Bill at BOATS 4 SAIL]

Thanks guys. I got it right on my next post. I should have gone into electronics.

[baldbaby2000]

My severely bent Mac 25 mast was progressively straightened using 2 trees. It's still sailing after 8 years and being in 40 knot winds. A friend of mine broke his Lightening mast (actually I helped) and put the sections together by welding an aluminum sleeve on the outside.

[Frank C]

... A friend of mine broke his Lightening mast (actually I helped) and put the sections together by welding an aluminum sleeve on the outside.

Yeah, I guess there are lots of solutions. Upon further reflection though, a mast sleeve is definitely NOT a good "preventative" measure. The rig is designed to pull a nice, smooth arc into the mast, and a sleeve would definitely screw-up that arc, probably causing a bubble in the middle of the mainsail ...