New Mast Tangs
- Thread starter Roger Long
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Absolutely. Neither the existing nor the proposed tangs are simply bolted to the mast. There are single bolts running right through with closely fitting compression tubes.
Which brings up an important point. Compression tubes are often lost when owners or yard workers pull a bolt to paint or inspect tangs. The tube then rattles around inside the mast until it's hoisted up for stepping. Someone in the yard picks it up and wonders, "What's this?" The owner later wonders, "Why did my mast fall down?"
The bolt and compression tube carry the stress right through to the tang on the other side with it's contact area distributing the force on the other side of the extrusion so both sides are working to resist the shroud forces.
My take on your original design is that it is more than twice as thick as the old tang design was so the stress would be lower than it was in the original. The original design guaranteed flexing in the top leg at the higher stress level. You didn't have a failure yet due to fatigue. so it follows that the original new design should last longer than the original tangs.. The fatigue curve is an exponential so less stress gets you to higher cycles fast.. at some low stress level, you fall below the fatigue curve and there is no fatigue failure.. Either one will last a LONG time and in both cases, the mast connection is the weakest part.
Its stood the test of 40 years and shows no worse for the wear and its not like you going to soemthing that was not already a standard way of doing it
Now whats wrong with this t-ball picture PLENTY and Hall Spars became my Peter Kennedy trying to tell me it was OK until they finally fessed up and admitted they had used the wrong angle t-ball and replaced the rigging
People used to traverse oceans in open wooden boats with hemp rope for stays and shrouds. There is a point of over-engineering the tang. This isn't new science or anything. If somebody brake forms this for you, make sure they don't try to get away with using the knife die that's sitting in the press. You probably already know but make sure the radius is 2 X the thickness or 3/4" to avoid stress fractures. OH . . . the stories I could tell!
Strange, your tangs show the same sharp bend line, nearly a groove, as mine. I thought mine were just bent improperly. Everything I know about engineering says they should fail at that line but, like you said, they have lasted 40 years.
The safety factor on most old boat stuff is so massive you have kind of small 3/16 uppers on the Cal puling on that giant tang 
I see the 3/16 upper on the Cal29 as small because it is the same size as the J24 uppers BUT it seems to be plenty strong other than common sense replacing as it gets old
I see the 3/16 upper on the Cal29 as small because it is the same size as the J24 uppers BUT it seems to be plenty strong other than common sense replacing as it gets old
A question if i may? What is your mast made of Roger?
If you like the second tang design I saw on the post I would point out that with a blocked eye tang you have the advantage that it is more forgiving as to shroud angle deviation than the strap tang. The bend angle on a strap needs to be very very close to the pull angle of the shroud to prevent stress as most of your force is applied onto the closest fastener to the shroud attachment and the blocked eye version is almost self angling (just need to make sure the angle of the shroud falls BETWEEN the anchor points to spread force equally).
If you like the second tang design I saw on the post I would point out that with a blocked eye tang you have the advantage that it is more forgiving as to shroud angle deviation than the strap tang. The bend angle on a strap needs to be very very close to the pull angle of the shroud to prevent stress as most of your force is applied onto the closest fastener to the shroud attachment and the blocked eye version is almost self angling (just need to make sure the angle of the shroud falls BETWEEN the anchor points to spread force equally).
Anyone here ever heard of a Westsail 32 losing it's rig? Supposedly it is the ultimate production blue water cruiser with decades of service history. I was looking at the tangs of one having its rig disassembled today and was shocked by the geometry and how light they were. If there is a real world problem with my proposed simple 3/8" bent tangs then there ought to be Westsail 32 rigs all over the bottom of the ocean
You are correct, Roger.. My post #23 says that between the lines.. no problem with your original design.
The problem with asking Ingun-Ears a question is that lots of times they've had to explain a design to their boss.. No design is ever optimal, but you have to stop when it is sufficient!
The problem with asking Ingun-Ears a question is that lots of times they've had to explain a design to their boss.. No design is ever optimal, but you have to stop when it is sufficient!
Monel steel?????
regards
woody
why not use 1/4 inch thick monel insted of stainless steel ?......
regards
woody
Not to extend this already overwrought thread but for the sake of my learning - what about cast tangs with the bend in the casting? For those in the know - is there a difference in the stress patterns between a SS bent tang and a cast bent tang? Can you even cast SS? Monel? What about Bronze?
I'm not asking about the cost factor, or if its practical. I'm just curious about the metallurgy involved. So you "in-jun-eaerz", please enlighten me.
I'm not asking about the cost factor, or if its practical. I'm just curious about the metallurgy involved. So you "in-jun-eaerz", please enlighten me.
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