I hadn't been sailing for months, if not a year, until recently. To my surprise the mast base tendon broke in two, just before I was about to launch. Luckily I had a spare, so it wasn't a drama.
So, I decided to replace the tendons on two mast bases. In doing so, I checked the other spares that I had. Of the 4 I tested by bending over, 3 of them tore in two or showed huge cracks that would have torn anyway.
So, what is the normal lifespan of these things? Is it the UV exposure, or just lifespan? In going through my spares I found a chinook boge joint and two-bolt deck plate. It looks like new. Do these fatigure the same way tendons do? (Just out of interest, one of the failures was also a Chinook tendon, so I don't think its a brand thing.)
Also, I decided to replace my NP MXT tendons with Chinook tendons. Other than the NP ones having the holes line up and the chinook ones being at 90 degrees, can anyone see a problem with these?
Every X Mas or happy holidays for me . Haven't broken one yet.
The scientific formula is : Flex revolutions x distance of flex x compression x age x sun exposure x temp X other smaller factors.
(fr)x(df)xCx(uv,T )x WTF ? 
Select to expand quoteseanhogan said..
Got one similar sitting in box of goodies, won't break in a hurry but quite harsh.
Select to expand quoteFormulaNova said..
In going through my spares I found a chinook boge joint and two-bolt deck plate. It looks like new. Do these fatigure the same way tendons do?
No they don't fatigue like Tendons & I have never used Tendons for this reason.
I used to use Hydro Unis for obvious reasons 
which would last for 5 - 7 years but now use Boge style.
The advantage is you can easily see if they are perishing or cracking, and yes they do last longer.
Just got one of the mechanical jobbies to try on the Inflatable SUP, not sure how it will go proper sailing, feels a bit clunky.
I get about 2 years out of mine .....but I have had a **** bunch that lasted 2 weeks 
..
surf and sail wa .have the good chinook tensions ..which I used to replace them ...
but I like the idea ...Of aus808..,and seahogan ... no tendon ...but they are very ridged in rough conditions .
i replace mine every year if I'm ocean sailing ...
Still don't like boge.
Forget the rubber bit and think about :
(1) with boge, if the bolt is starting to pull thru the rubber you can't see it.
With tendon, if the bolt starts to elongate the hole, when you bend it you can see the hole / tear at the edge of the cup.
(2) with boge, the failsafe device is a cordura nylon strap like your kids' school backpack has. That strap goes around the hourglass shaped rubber 360deg, and on the ends you can't see it. Furthermore it has a hole melted into it for the bolt to run thru. So it is nowhere near as strong as downhaul rope. Plus, it may have worn. How many gybes or sail pumping little rotations has that strap endured, sandwiched between a couple of washers and full of sand?
Geez, you just made a sandpaper slurry, subjected your failsafe device to it, AND can't inspect the failsafe easily.
Compared to tendon which has a bit of 500kg downhaul rope that you CAN see every time you see it......
Plus, even if that downhaul rope safety breaks you can thread spare rope thru the holes and pull the board half and sail half together. If boge rubber and strap breaks there is no way you can tie it back together on the ocean.
Tendon wins
Select to expand quoteShifu said..
Chinook Cast Stainless Europin - the king of UJs.
Even better when married to the two bolt plate, using the quick release version of that uni. Never been a fan of the single bolt version.
^^^^^ but adjustable only with Allen key? And doesn't go to full extent of the mast track? Single pin is never a problem for me.
The bottom of the UJ has a hex to adjust it. But agree that single bolt has never been an issue, and that the lack of adjustment range is a weird thing, I always wondered how the two bolt ever prevailed
Select to expand quoteMastbender said..Shifu said..
Chinook Cast Stainless Europin - the king of UJs.
Even better when married to the two bolt plate, using the quick release version of that uni. Never been a fan of the single bolt version.
2 bolt base is great, in fact I have one for sale if interested
That's some serious rope on there, wonder why you would need all that 
I'm a 2 bolt fanboy!!! Love the 2 bolt plate! How much for yours AUS 808 can never have too many 2 bolt plates. If I have to move mine just use the inbuilt bottom hex key, very rarely have to move it more than a couple of cm either way of centre.
+1 for the cast stainless steel chinook europin too!
Two bolt base is heavier,so for that reason alone its a no.
Less adjustment on a two bolt is irrelevant for me, as i only use the exact middle of the mast track.
I buy the stiffest tendons. They usually last me around three years, though i swap between the two i have.
Never tried the Chinook boge joint,but if it lasts for 7 years it makes financial sense.
Select to expand quotepetermac33 said..
Two bolt base is heavier,so for that reason alone its a no.
Less adjustment on a two bolt is irrelevant for me, as i only use the exact middle of the mast track.
I buy the stiffest tendons. They usually last me around three years, though i swap between the two i have.
Never tried the Chinook boge joint,but if it lasts for 7 years it makes financial sense.
Well that's an interesting reason, weight, which could easily be offset by whether or not you made a deposit in your porcelain bowl before going w'surfing.
I love the convenience of them, I have a two bolt plate on every one of my boards at all times, moving the rig from one board to the other only takes seconds to do.
I just go by the rule: "if it's not broken don't fix it"
I've been doing a lot of swimming and my board has a lot of dint on the deck though...
Another +1 for the chinook single bolt europin. I always switch my tendons to streamlined after first season as they are waaay tougher.
Select to expand quoteMrCranky said..
What do people think of the North iTendon system?
I've used one for the last two years (along with their Shox system) and love it. I've just noticed serious wear on the tendon today and have ordered another... pricey... but I think they're worth it. Makes sailing fast on serious chop 20% easier, and you sail faster because you're more comfortable and feel more in control.
