Broken mast - Splicing

[lucaskizer]

I'm sorry about your luck. Hopefully you'll be back up and running again soon. In regards to the chainplates, I'm about half way through replacing my chainplates right now in my Slocum 43 with titanium. It takes about 2 days per side to get the four plates out and in hand. Please PM me if I can help in any way, as talking through it over the phone would probably be easiest. I have interior woodwork tips/tricks, chain plate drawings, material lists/quotes and tons of pictures. My mast is also currently down, if you need any measurements, pictures or just something to compare to, let me know.

[the dude abides]

Thank you everyone. It is interesting stuff. I also have to say that my insurance has been very supportive and when this accident happened they got onto it straight away to make sure my vessel was safe. I have actually been impressed with the service I have received to date. Cheers all.

[the dude abides]

That is really interesting. I would love to see how you went around it. There is so much teak here. Will PM - Cheers

[Timlb]

Just bought a Dufour 27 foot sailboat halfway up the mess it bends slightly to the rear of the boat is that normal or do I have a structural issue with the mess any advice would be greatly appreciated thank you

[RaymondR]

I broke my Isomat boom and found that they no longer make the section required to replace it. Since the end fittings are specific to the boom section replacing the broken boom would also require replacing all the fittings and consequently it would be excessively expensive.

I decides to attempt repairs and had a sleeve fabricated in three pieces from 3mm plate.

I used countersunk about 100 SS metal thread screws drilled and tapped into the 3 mm sleeve and when rejoined just beat the bent parts at the join back flush and screwed them down.

I suspect the repaired boom is actually now stronger than the original and .

[freynolds]

Walk around a marina and you'll notice about 1/3 of masts are sleeved near the spreaders.

The backstay broke on my C&C34 and the mast came down, breaking at the main halyard exit block about 2' above the deck. I cut off exactly 8" of damaged profile from the two segments. I worked with a mast builder who made me a splice consisting of a 4' sleeve (formed to fit the inside of the profile) and 8" of identical mast profile placed at the middle of the sleeve. I installed the sleeve using screws at about 6" OC all around and up/down the sleeve. All new rigging and now sailing again. I have a ton of photos and can describe further if interested.

[the dude abides]

Thanks for the reply. How long ago did you do this? Notice any difference in your sailing? I am in a dispute right now so have to consider all options. I am not sure it is possible with my mast as it peeled down right by the first spreaders and has cracked all the welding for the spreaders. I only have 2 left. I have been told that by the time I get that sorted it may well be the price of a new one

[MicHughV]

It appears that the mast broke at the spreaders. The spreader/mast connection is an area typically with a lot of holes due to the spreader fitting. At that area, Usually, right under the actual spreader fitting, is typically, placed a small hollow aluminum compression tube, say 1" in diameter or so,that runs right through the mast from one side to the other. Through this tube, a stainless steel bolt is inserted, which supports the lower shroud fitting/spreader fitting on either side of the mast. This is placed there, so the downward load of the lower shrouds, is placed on the mast, via the tube and bolt, and not the machine screws holding the spreader fitting.

Ok, now that we've moved past that part, it's important to recognize, that the mast should "stay in column"...perfectly straight, in other words, if the lower shrouds are tight, but the upper shrouds are loose, this is where the mast is likely to bend.....and break, due to all the holes drilled here at this location.

If you have a problem with chain plates, this is a likely source of the failure and should be investigated and rectified, as a loose chain plate leads to a loose shroud....etc...

As others have pointed out, a splice can be fabricated, but this must be done with the greatest of precision, to include all the various spreader fitting holes and tubes. The compression load on a mast can reach several 1,000's of pounds. Don't expect a machine screw(s) to take this load, the object is to clean and cut the edges of the two parts of the mast, so they are as near as damnit flush with each other.

Going at this with a hacksaw and eyeball measurements is not going to cut the mustard.

My recommendation is to remove the mast....you have to do this regardless, and take it somewhere to get spliced professionally......short of that...it would be time to shop for a new mast section...

[freynolds]

^^ A hacksaw is fine! As long as it is the right size hacksaw... Here is the one I used to cut my mast in preparation for the splice.


https://youtu.be/oLwVJE2hsUE

[MicHughV]

yep, spot on, that is the hacksaw to use, more importantly the mast is set in a jig, that assures a perfect cut perpendicular to the mast. excellent !!!

[RaymondR]

I did not know it had to be that complicated. I just sort of panel beated the boom so I could get the sleeves in and then beat and pulled the bent bits down until they matched up. It was pretty distorted, it had broken on one side and then bent double on the other.

With a mast I'd probably have needed a bigger hammer and dolly though.

[MicHughV]

a boom is not in compression like a mast is...it has no stays or shrouds trying to push it down....different loads altogether..

[RaymondR]

Originally Posted by MicHughV

a boom is not in compression like a mast is...it has no stays or shrouds trying to push it down....different loads altogether..

The OP states that the mast failure was occasioned by a chain plate problem and bent at the spreader. This implies that the upper shroud on one side released tension and since the lowers were still restraining the lower section laterally the mast bent above the spreader from lateral loading. That is that the failure resulted from a bending rather than a compressive loading.

This is most probably the case with most upper mast failures, compressive loading failures being more common at the lower section of the mast and then from a combination of compressive and bending loads.

Since the image shows the mast still standing I am assuming that it was an upper shroud failure.

Booms with vangs are also subjected to compressive loadings although in my case the failure was the result of a loose footed main sail generating large moments around the main sheet attachment point it being situated only about 5/8 of the way towards the end.

In the OPs case we are dealing with two systems of forces, those below the lower shroud attachment points and those above. In the lower case compressive loadings probably predominate. In the upper not so much. But in any case the repair does not require excessive attention to the compressive loading.

If I was doing the repair I would emulate the technique I utilized on my boom however rather than just three pieces of sleeve I would use multiple internal splints with channel sections.

I would probably use 3 or 4 mm plate with the web section about 1 1/4" wide and the flanges 1/2". I would place them side by side with the flanges firm against each other and plug weld them every 3 - 4 inches along the flanges through the mast wall. One would need to over bend the flanges to get them to nest closely around the curved internal surface.

Since I'm a belt and braces sort of bloke I'd probably put some countersunk screws through the mast wall and into the middle of the web as well.

In the case of my boom I had intended to glue the sleeves in place with an epoxy putty used for cast iron pipes which appears to have a remarkable bonding tendency with aluminium but after drilling, countersinking, tapping and installing about 100 screws I had an energy fade out and could not be bothered pulling it all apart again to put the glue in and then reassembling it. However I've done 1,000 or so nm of coastal cruising with the repair and it seems to be surviving with just the screws.

There's a lot to be said for the KISS principal.

[MicHughV]

my point was simply that the profusion of holes at the spreader location makes this an ideal spot for the mast to bend and break, as you correctly point out, I was trying to elaborate, the lowers keep the mast "in column" so to speak, but the slack uppers, due to chain plate malfunction, remove support for the mast above the spreaders, causing a bending moment, perfectly aligned with that spreader location..