Am I jinxed ??? or are U/J's not made like they used to be or maybe they are made in China !!!
Just broke my second U/J this season (the chinook straight sided ones) and this one only on the 3rd session -- mind you it was a hard landing. The previous one was about 2 months old when it decided to give up on me. You gotta love "swim savers".
I've never had anything like this before due to the fact that I ALWAYS change them before the season starts. The chinook extension I use has done about 6 seasons but if I can't find a reason for the U/J's breaking it may be destined for use as a back-up and I may have to go for one of the Boge?? Uero thingy's.
The broken U/J's were different manufacturers to each other but I'm sure I've used the first one that broke before. By the way the one that lasted 3 sails was a red one and I'm definitely never goint to get one of those again....
) goes well for silicone rubber too..i went to a local rubber co. and showed them one if they could copy it so they tested it with a hardness meter and tried to mix chemicals and make me one for sampling and in brown color worked fine but tore off the ends since i didn't have it drilled in a press but did it manually..a friend bout a meter long 'industrial' rubber from all places russia colored light brown and cut to size and up to now since a few mos. back still attached to his mastfoot and no tears
Ok If your going to use tendons you need to use the streamline ones. Why, well because they started the trend but they used a better quality rubber from the skateboard industry that has an oil in it, so that it takes a bit of time for this substance to dry out and the rubber to go brittle, the streamline ones do break just not as fast as all the other imitation ones. If speed is important tendons are great if longevity of your board is important boge is great as they soak up some of the energy and the mast box doesn't get such a pounding.
Yes the tendons are made from urethane which as one fella said, dries out, they go all powderie, i've seen most brands, they all tend to do the same, i have noticed that chinook use a more rubber based tendon in there new bases, and the new machined alloy base runs oversized pins, the more rubber based or oil based (kinda the same thing) tendons seam to out last the rest. the older orange tendons where also a good and lasted alot longer, the boge or bridgestone hourglass uni rubbers last for a hell of a long time due to the fact there made of full rubber, we just need boge to start making tendons..
In the future when you have to buy a new tendon make sure you suss it out, look for one with very small or no molding marks in them, like the chinook, as 90% of all the tendons i replace for customers have split on these points..
Although I have not snapped any uni joints recently and are happy with my Chinook joint, the reading above started me wondering.
I have access to simple tension machines as well as cyclic tension machine. I may get a Chinook joint and do a few tests on it to see how it survives.
If you have any old (or new) joint that you would like tested and cover the cost of postage to Western Australia, email me and I'll give you my postal address.
I don't want to end up in an argument with manufacturers re their uni-joints and strength/durability, more just intrigued. Thus if you sent me a s/hand joint you would need to give a bit of history of its use - ie lying in the sun for 2 years etc. I will then test and present all the data (new V s/hand and uni V tendon)
Any test would only be uni-axial as I have no way of performing 2d tests whilst cycling etc.
If any manufacturer reads this and would like to test their joint contact me feel free to email me
wayne@civil.uwa.edu.au
A bloke at a fishing/diving shop i know keeps all his stock of speargun rubbers in the fridge.Sounds wierd i know but he swore by it.Hmmm my gear spends most of the summer in the car ...rubber doesn't like heat.Might have to change my habits
But then i do change them every season.Broken UJ's are your worst nightmare when your on a reefbreak with a K to swim to shore
As A beginer i envy your knowlegde i bought a cheap kit to start it had a broken tendion if that is the rubber piece .2nd time out the plastic peice that attaches 2 board broke & apparently they dont make them like that any more so i bought new base & i will keep the old new rubber as spare .The new base does not fit my aluminum extension so i will problably have to buy a new extension thats okay as i want to upgrade slow and possibly cheap with more time and experance .So I feel a bit jinxed also
Im not having a problem with the tendons but am breaking the 4mm bolt that goes through them, I replace them often but they bend almost straight away and then shear off, I am now trying a high tensile bolt packed in grease, I know these will rust but not as quickly as I am breaking the S/S ones.
Its a horrible feeling knowing your whole rig relies on 2 x 4x40mm bolts that will break at any time.
yeah I know solution is go to bogey joints, but I'll keep going with this, hopefully someone can put me on to a quality stainless steel supplier as all I have found is crap.
Excuse my ignorance in these matters, but what's a bogey joint? I may have one, as I've been using the same uni since 2001, hence my lack of knowledge on the subject.
Pweedas - yep I agree - the joint is more often than not subjected to compressive shear loads.
Initially I simply thought of a tension test as I have a 20year old Windsurfing Hawaii joint (that I am too scared to use) and would be interested to know how it stands up against a new boge joint.
That said, I don't know if manufacturers have a testing regime that is followed to prove their rubber joints be they uni joint or tendon type. Maybe someone can enlighten me.
It would be possible to build a small rig to place the joint in a somewhat natural use state althought to my way of thinking the loading on the joint is quite random and erratic. Hence I thought an initial simple strength test.
I'm open to ideas and it may keep me occupied when there is no wind
Select to expand quote
4mm sounds a bit thin. Are you sure they are 4mm ??
Are you sure they are the right ones or did someone just put them in cos that's all they had at the time?
Can you replace them with a thicker bolt,.. like 7 or 8mm?
I would stick with the stainless rather than the high tensile.
Stainless is as strong as,.. and if that is breaking, the slightest amount of corrosion on a high tensile bolt will cause it to fail at that loading.
Yeah they are 4mm,its the only size that will fit through the brass bush on the tendon joint, If I drilled the holes bigger it would weakin the tendon, The original bolts lasted a bit longer, Im assuming the S/S is a better quality from the manufacturer,
Select to expand quotewormy said...
4mm sounds a bit thin. Are you sure they are 4mm ??
Are you sure they are the right ones or did someone just put them in cos that's all they had at the time?
Can you replace them with a thicker bolt,.. like 7 or 8mm?
I would stick with the stainless rather than the high tensile.
Stainless is as strong as,.. and if that is breaking, the slightest amount of corrosion on a high tensile bolt will cause it to fail at that loading.
Yeah they are 4mm,its the only size that will fit through the brass bush on the tendon joint, If I drilled the holes bigger it would weakin the tendon, The original bolts lasted a bit longer, Im assuming the S/S is a better quality from the manufacturer,
ask for 404 grade stainles not 416 as comonly used and dont get food grade stainles thats even softer you can get a 390 high tensile stainles but it will rust in salt water only good for fresh water
Ive heard off 304and 316 but not 404 416, is this another grade again,
I was told 316 was the strongest, maybe I should look for 404
check this out, I think I need 316 page 4http://www.atlasmetals.com.au/files/grade_chart.pdf
page 4 on that chart gives general apllications.
Ive been using 304 from the local hardware, which has been crap, but i think the local chanderley will have 316, Ill give it another go
I havn't heard of anyone supplying other grades than these,
I these fail I might chuck the lot and re-think
Thanks for your prompting my brain into action
But then i do change them every season.Broken UJ's are your worst nightmare when your on a reefbreak with a K to swim to shore
) and they usually split through the small pin or bolt hole which can't be inspected without dismantling.
I have been using tendons for years and never had any dramas. I use them both for race and wave, and am easily going onto my 4th season on my two bases.
Would a reef knot followed by a little bit of good old fire to melt string ends together be OK?
...The previous one was about 2 months old when it decided to give up on me. You gotta love "swim savers".
Is that the term for the string that will keep rig attached to board if tendon breaks? Anyway my string has untied itself, can't see what knot is used on manufacturer's site.
Would a reef knot followed by a little bit of good old fire to melt string ends together be OK?
The swim saver is either "string" or webbing on the Boge style. I always tie a reef knot - granny knot will do if you're no good at knots- but the only way I've found to stop them coming untied is to put a generous blob of superglue or Tarzans Grip etc on the actual knot.
When you replace the tendon you just cut the rope and replace it with another piece and then glue the knot -- SIMPLE hey !!!
AMEN to Boge, hypersonic and Chinook hourglass type uni joints 
last for a couple of seasons with much abuse 
unlike the one inch diameter cylindrical tendon type which is fine for the slalom sailor but not much good for durability 
Euro pins are a bit sus, so IMHO if you want the ultimate in reliability, chinook cup + boge/hypersonic/chinook hourglass tendon 
is the only way to go 
i've had 2 hourglass tendons break in 6 years of very regular sailing and they get treated fairly hard
BTW - the hourglass type tend to show obvious signs of splitting before they break, unlike the cylindrical tendons which tend to tear where the bolts pass through without any warning
haircut knows his stuff, 100% agreeance on this matter, after snapping 2 of the tendon style.
