Mast base tendon breakages

JJ,
I was only thinking about this the other day. I too only use the Chinook uni (both the one above and the quick release deck plate/pin one) and always ensure that the spare tendons I purchase are authentic chinook. I went a longtime with no breakages then had a spate of them in fairly quick succession. I kept my spares in the tray of a plastic toolbox and thought that maybe off gassing or chemical reaction of the tray and tendon combined affected the tendon's mechanical / chemical properties. the toolbox never sees the light of day and stored in a fairly controlled (temp) environment so I can eliminate heat factors. Out of interest as I am a bit of a bower bird I kept all my old replaced tendons that were in one piece in the same toolbox and went to reuse when I had ran out of new spares. A light bend of the uni I quickly discovered that these old tendons had perished and easily broke apart. So I now keep my spares in paper bags - whether this has any effect I wouldn't have a clue and it'd be great to hear from a mechanical chemist on possible theories for accelerated perishing / polymer degradation.

Have you checked the edges of the machined parts as any small nick on top edges could be making small nicks in tendon when bent right over - I had to file and sand smooth the burrs on one that had clashed / rubbed together when I broke a tendon.

One other factor to consider is that doing a lot of ocean sailing would stress the tendon more so than estuary or flat water sailing.

Also totally agree with you on the formuline as it has saved me every single time I've broken one. In fact I've sailed on before oblivious to the fact the tendon had broken.

previous threads here too JJ -
www.seabreeze.com.au/forums/Windsurfing/General/Check-my-Tendon/
www.seabreeze.com.au/forums/Windsurfing/General/Tendon-Mast-Base-Euro-Style-Pin-Trouble/?page=1
www.seabreeze.com.au/forums/Windsurfing/General/Best-boge/

Snags
Interesting you've had similar problems. I don't think it's a Chinook problem as I've had failures equally quickly with other brands.
I had a look at your wounded tendons - mine look the same often after only a few sessions, then always break within a couple of months.

I'm eager to see if someone can say definitively that the polymer can degrade without correct storage.

I've checked the mast base a few times for burrs but I'll certainly have another look.

Thanks for the links - seems Vando goes through a tendon every 3 months too.

Somebody commented that the if the rope is too tight it could constrain the normal bending of the tendon and perhaps weaken it.
Mine seems to have plenty of movement, perhaps an issue though?
Clutching at straws for now.


Thanks Spurgeo
Seems like you're none the wiser for the sudden rash of breakages?

I don't feel any wiser Azymuth

I don't think I can make any conclusions on my experiences. Would ideally need to test hundreds over many seasons with set/standard conditions.

I pay more attention to maintenance of that area now, make sure the safety rope is always in good condition, physically bend and inspect the tendons regularly and if they look dodgy I'll replace them.

Windsurfing can be a bit rough on gear and body, if something is going to give, I'd rather break a few mast base tendons each season than masts, boards or the tendons in my ankles etc

Hi I used to use the skinny tendons (streamline) brand was good till it was showing stress lines ect,
Changed the tendon with in 3 sessions tendon broke,changed it again ,tendon broke ,I would have to put it down to bad batch, heat, bad chemical mix. Most of the boys use tendons and don't have any issues, go figure.
I use the hourglass bogie joint with much more success, they all break but these seem to be a bit more reliable, my 2 cents

I sail lots and use Chinook tendons mines 1.5 years old I'll replace it at the end of the season. I keep my spare in an air tight container inside a way from heat and light. I think its a bad batch, maybe they outsourced to a cheaper country, maybe Chinook needs to do their own quality control testing like putting sample ones in a machine that bends them day and night until they break. Why not email Chinook?

You guys must be windsurfing super hard and long, maybe you need more downhaul?
I use a mix of various bases and replace the tendons every 1~2 years, no breakage so far.

This year I have replaced 2 chinook tendons and had a North Tendon break while I was about 2km off shore, had to self rescue and made a mess of the deck of my board due to design of North Shox extension.

I have not broken a UJ for many years, so 3 failures in a year is shocking

I always check the condition of the tendon before sailing - the 2 Chinook tendons I replaced due to visible cracks, but they did not fail on the water. The North Tendon safety rope inside also failed.... not much of a safety feature if it is not up to the job

Bad batch!!! that was what i was told after going through the same problem,,to many bad batches for my liking, will never use tendons again. Stick with the fat boags . No excuse for bad batches!!! its a critical component that can leave you in dire situations in a breakage…Bad Batch,Blks

I simply refuse to use a Tendon.
You cannot see if it's about to shear through the holes without pulling it to bits so you might as well just replace it while you're at it.
I have seen heaps break but very few Boge style.
I used Hydrodynamix Unis for years & don't think I ever had one break and I only got the seconds that were not good enough to sell
I think I changed them out around 4 or 5 years.
When they were no longer manufactured I went to Boge & have never had one break (yet) and I can see if it is about to break quite easily.
I have heard all the arguments about how much better & stiffer the Tendons are but don't give a rats, I like security & an un-damaged board.
If the swim saver rope is not real short the broken Tendon will punch nice holes in the deck sailing home

North have a hollow Tendon with a St St wire through the centre, pretty clever but don't know how long they last or how hard it is to inspect the tendon & wire for wear.