Bent top section!

M

macwas16

New Member
Hi,

While sailing in some really windy (18 knot) conditions at the Hyannis Regatta this past weekend I bent the top section of my Radial rig. I always let my vang off at the top mark but it could have been from death rolling a few times as well. Either way, it is bent pretty nicely.

How can I fix the bend? If I put the bent end in a vice and try to bend back the other end will it straighten it? Would you suggest end for ending the upper section and sailing with it a few times?

Any suggestions are welcome because I want to get it fixed before the Buzzard's Bay Regatta this weekend. Plus it looks really goofy too. Thanks.
 
There are a number of methods, the more common ones I've used are to put the top section in such that the bend is opposite the gooseneck, then go sailing, mainsheet and vang will slowly straighten the bend out (and work harden the section at the same time)

The other is to put the mast together, brace the butt and top and with the bend facing the topside, slowly press down (you may need another person to help push if you don't weigh enough) at the point of the max bend.

There's plent of info about these and other methods in the email archives - a good search term is "bent mast"Laser list achives

drLaser has an article also in the maintainence section, but for some reason it's not allowing access to it, even with the proper user/password combo...
 
Dont stick it in a vice, it may crease where the vice grips the mast. Was it a new top section? They can take a while to work harden and if it is bent like a banana I would straighten it, I find the fork of a tree good for the job, the soft bark protects the mast, sorry greenies, just work it back into shape a bit at a time, you will be surprised at the force you have to use.
If it is bent severely at the collar, you might have cracked it through the rivet, particularly if it is old and corroded, if you reverse it next time you sail in a breeze it may break. Best option if you suspect a crack is drill the rivet out and eyeball it, end for end the spar if it is cracked, otherwise you can straighten it then refit the collar.
Let us know how you get on.
Darryn
169711
 
The boat and top section are new (as of July of this year) and it doesn't look like the collor nor rivet have been damaged. The point of maximum bend apears to be some six inches above the point where the upper and lower mast sections connect.

Thank you both for some wonderful methods and hopefully I'll be able to bend it back!
 
Darryn said:
Was it a new top section? They can take a while to work harden
Click to expand...

So how long does it take for a spar to 'work harden'? Do people in the know buy spars a year in advance, and let them age somewhere like fine wine before they use them? (I'm visualizing a 'spar cellar' in some Olympic wannabee's basement) My mast broke this spring, I bought a new spar (full rig lower) and that thing was bent in 2 days. Granted, it was blowing 20 kts, but still...Now I'm using a 15 or 20 year old lower that is incredibly stiff and probably will be up until the point it snaps completely.

Also, if they do need to cure for awhile, why are they sold before they are ready to use?
 
Michelle said:
... if they do need to cure for awhile, why are they sold before they are ready to use?
Click to expand...
Work hardening isn't a time thing, but results from repeated flexing. Hence the suggestion to reverse the top section after it's bent. At a clinic this spring, Ben Richardson suggested turning the mast sections 180 degrees every time you go sailing. This has the effect of bending the section back and forth slightly and accelerates the work hardening.

Cheers,

Geoff S.
 
For the lower section work hardening you can do repeated mainsheet trim/ease and vang trim/ease. You can do this with the boat out of the water. A couple of hours, besides giving you a good workout, is worth the trouble.
 
Just out of curiosity, is there anyone out there (metallurgists?) who can tell us how many bending cycles (and how much deflection per cycle) are required to adequately work harden a Laser mast?

Cheers,

Geoff S.
 
Thanks for the info, guys! I've been wondering about this work hardening for awhile now. I'll try to break in my next spar better.
 
Why would you want to work-harden your spar? Work hardening metal makes it brittle, and prone to failure during bending cycles. The spar will get work-hardened over time just by using it.

It seems to me that artificially work hardening the spar will cause a pre-mature failure.

Am I missing something?
 
I'm not a Mechinical Engineer, but my understanding after talking to one and reading up on tempering, aging, strain/work hardening is along these lines:

A brand new aluminum tube, aka mast section or boom, that has not been used is going to bend more easily, bend more in absolute measurement and be more likely to suffer a permanent bend than one that has aged ( just sitting around for a couple of years or more) -and/or- one that has been work/strain hardened.

Taking that a step further in simple logic, it would seem to follow that going out w/ a brand new section in very windy conditions, and sailing with super vang tension is likely to result in a bent section. Throw in a high speed capsize or two under the same conditions only increases the odds.

Age and strain/work hardening stregthen the alloy as far as resistance to bending, but do indeed make the alloy more brittle as Scott pointed out.

Does it explain why older spars seem stiffer in use then new ones ?
Why new spars suffer perm. bends more often then older spars ?
Why old spars break more often then new spars ?
Which is the lesser of two evils ?
 
Hello,

Well, I am an engineer, and have some materials expertese. Also, I have 25+ yrs in Lasers, but all without the recent bending problems. I do think the older spars were better (stiffer at least), but it's not quite apples-to-apples since we didn't have the supervang etc. all of those years. I do also believe that the Max. stress on spars is whacking it on a death roll, dragging the vanged boom by heeling too much, or rushing a righting when the main is full of water. All relatively avoidable situations.

I don't believe ageing alone has any effect on aluminum. Work-hardening might help, as it is a known cause of stiffening (with the resulting brittleness eventually). The best example is an (old fashioned) steel coat-hanger. You can bend one of these back and forth about 5-6 times and break it.

If your only option is work hardening, I think you should know the difference between elastic and plastic deformation. Elastic is the normal bending that returns to the original (straight) state. Plastic deformation results in a failure to return to straight. I believe that work hardening can only occur from plastic deformation. So, repeated vang workouts won't do it. But reversing a slightly bend top and "sailing it back to straight" would actually result in a stiffer section, with brittleness as the (eventual) trade-off. Also, the logic of reversing it often is good, although the radial bottom folks with problem aren't helped by this.

I am very suprised to hear McKensis speak of a bend 6" above the joint? There is no logic that explains this, as the stresses have to be maxed at the top of the bottom section? This would seem to be caused by a "weak" spot caused by thin wall, or some pollution in the alloy. I'd guess that "sailing this back to straight" will result in a bend somewhere else, probably lower down.

Aluminum is the most recycled metal in the world, and the alloying is a bit more imprecise due to this these days, I believe, but this spar problem seems much greater than occasional alloy pollution. I'll bounce this theory off a Laser sailor whose company makes the Alum. casting machinery.

This is a class problem, as well as Vanguards, as noone wants to buy a new boat that can fail in a windy weekend? Or two or three tops in a year? That's rediculous for a 30 yr old class. As I have mentioned before, we seldom hear about this from people with boats 148xxx or older.

Let's keep digging on this,

Al Russell 66451
 
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