Crack Discovered on Cast Aluminum Masthead - What to do?

[Doug in Lakeview]

Hi all,

Last weekend we unstepped the mast from our 1984 Beneteau First 38. Upon inspection of the mast at grade level we noted that the front part of the masthead aluminum casting was cracked. The crack is on the portion of the masthead to which the headstay is connected. The stemball fitting (which is located in the cast aluminum fitting & is free to articulate) has a toggle at the end of the stemball fitting to which the headsail furler is attached. There is a slight chance that the area where the crack is does not support any loads.

Questions…..

Has anyone else experienced this problem? Can this crack be TIG or MIG welded? Or do I need to replace the front section of the mast head. Any other suggestions?

I will be contacting Rig-Rite Inc, 63 Centerville Rd Warwick, RI (www.rigrite.com) and also SPARCRAFT - US (Charleston Spar), 3901 Pine Grove Circle, Charlotte, NC (www.sparcraft-us.com) looking for advice and replacement parts. The masthead is welded to the mast and the weld will need to be ground out to install a new piece – if available.

Mast still had the original manufacturer logo and serial number label. Serial number is “62906”. Per SPARCRAFT website they have access to the original “as built” files from ISOMAT & KENYON. We shall see.

Mast: ISOMAT NG 60 <- confirmed by measurements & Beneteau brochure
Masthead: ISOMAT NGII <- confirmed from dated ISOMAT catalogue

Doug in Lakeview
1984 Beneteau First 38 – Hull #178
Belmont Harbor – Chicago

 

[Mike B1026]

I would first try to figure why it cracked. Any idea?

 

[Doug in Lakeview]

Hi Mike,

We have only had the boat for 7 months and did not push her hard this season so I doubt if it was done this season with us newbies sailing. We did have a survey done when we bought the boat but did not have the masthead inspected at that time. I was not present when the mast was unstepped this past week but could envision that if the base of the roller furling was swung away from the mast (while the top was still connected to the masthead) that excessive force could have been put on the casting and that it might have cracked. But, in my opinion, it would take a lot of force to crack a 1/2 inch thick aluminum casting. Also, the guys who did the unstepping are pros.

She is 28 years old and if the cracked area does not support any loads (as I suspect) it may have been cracked for a long time.

If a new front section of the masthead is still available, we will have the damaged one removed and a new section welded in. If not, a good full penetration weld to repair the crack is our next best option.

Doug in Lakeview
1984 Beneteau First 38 – Hull #178
Belmont Harbor – Chicago

 

[Allan12210]

Look inside the crack if possible with a magnifying glass. If old, it should appear dull or oxidized to the same level as the outside. If shiny, then it could have happened during demounting.

Its hard to say from the photo, but the crack doesn't appear to be from the normal direction of the forestay stress (unless too much rake?). It almost looks like it happened with side loading of the forestay against the casting like twisting while the forestay was still attached and could come up tight. Or the mast falling but then caught during removal with the forestay still attached at the bottom. Look up inside and see if there are fresh witness marks from contact being made on the toggle or the cast surface.

Perhaps the crack can be welded.

 

[kloudie1]

I agree with Allan. The crack does not look to be in the load path of the forestay, and the crack is not in a normal force direction. Twisting in the past from a jammed roller furler that was winched? seems a bit for fetched.. more likely a side pull during a mount or dismount of the mast in the past. I don't think I'd replace the entire section, rather inspect it very closely for more small cracks that may be in the forestsay load path.. if none are noted, a quick weld should be OK. If ya see more cracks, then think seriously about replacing the whole front.

 

[rufus1138]

the crack is not structural (not close enough to the flange where the stay rides in the fitting), it can be welded. i can say with near certianty that it was cracked in the manner you suggested, sideways deflection at the headstay union under that collar/skirt that is cracked, whether in the yard or due to improper headstay tension/excessive headstay sag is impossible to say but it happened regardless and its not structural, if it were me i would opt to trim the skirt back to allow access to the terminal in case you have to go up there in an emergency.

 

[Doug in Lakeview]

Thanks for all the comments/suggestions. I will be at the yard this weekend and will be carefullly looking at the crack for color/discoloration in an attempt to determine how long the masthead has been cracked. Bright flashlight and magnifing glass will help to see what it looks like. I may even try getting some closeup pics and ask one of the metallurgists at work to give me his opinion.

 

[Sandy Stone]

The masthead of our First 375 is very similar, in that it also has a cast 'hood' over the headstay connection, I believe to help keep the spinnaker from fouling there. And in fact when we went to step the mast after delivery to our hometown, we found a very similar crack. It looked like what other people have said, side loading while stepping/unstepping the mast at some point, not structural at all. I went ahead and faired it out with epoxy putty to keep from snagging the spinnaker on sharp edges, stepped the mast, and haven't had any problems since. (2-1/2 years)

 

[jibes138]

Maybe you could just cut the whole section off to just past the crack and then alodine (aka conversion coat) the cut section of exposed aluminum? The stemball fitting is spherical and the loading is at the top of the masthead so that section looks unstructural and as someone noted may be to prevent tangling halyards or sailcloth. Maybe some shrink fit tubing would work over the connection of the headstay to prevent tangling? You might want to pay a rigger 50 bucks to take a look and give you some advice. The fracture looks from the pictures like the headstay angle to the masthead was increased in a forward direction but why it would fracture on only one side is unclear, perhaps the material had an inclusion or other anomaly at that location?

 

[jibes138]

The problem with welding it is you will get a large heat effected zone that will drastically weaken the material surrounding it. Aluminum solution heat treated and tempered can be quite strong but in an annealed condition not so much. The close proximity of the sheaves would also suggest those would need to be removed to attempt welding. Another option if it isn't causing any problems is leave it alone and let it eat at your mind while you're trying to get to sleep at night. :>)

 

[Apex]

to my eye, looks like the entire forestay is shoved upward into the fitting..... The second picture shows the top rod should drive down into the pocket. I agree, it appears the shackle driven up into the masthead casting likely caused the crack. I don't believe the rest of teh fitting has been compromised. Aluminum doesn't like to be flexed, so clean up in place, perhaps weld, then grind to clean up the look.

 

[hewebb]

If it were on my boat; I would have it welded then re heat treated/aged to eliminate any stress areas related to the weld. Check with a metallurgist to insure what process should be used. The heat treat facility should also know how to handle. Some distortion will occur during welding. Typically alum will shrink.

 

[Scott T-Bird]

If it were mine, I wouldn't think twice about it ... I'd replace it and end all concern.

http://www.rigrite.com/Spars/Isomat_Spars/NG2_Masthead.html

These people are in business to solve this kind of problem.