Hi Mark, thanks for your spot on (earlier) assessments/advice above

Sorry if not clear from my side. The original builder is a few countries away. Transport is relatively expensive/time consuming, so i opted to involve another, local builder. To do it well, is quite a bit of labor indeed. Labor is expensive here.

I'm fairly sure the original builder would take it back/perform the replacement if a bit easier logistics.

For me, it's about living with a suspicious mind on a taken for granted component as these experiments and/or inferior boxes will likely surface again. Your rig may not :) And, some other sailors who are out there with something not really up to loads and/or the unpredictable joys of non-composite materials fatigue.

"Swimming good, carefree carbon pole dancing better"
free after Snowball&Napoleon 1984

One day I might make it to WA, i hear the flies do not discriminate

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Doggerland said..
"Swimming good, carefree carbon pole dancing better"
free after Snowball&Napoleon 1984

yeahhhh, I dunno.
Somehow I'm still thinking eccentric nuts.

Hi, I'm a bit late to this thread, but I'm also wondering if the analysis of the problem so far is correct.

One of the issues people have with their deckplates and mast tracks is actually caused by their U/Js not rotating correctly.

There should be a rotating bearing either side of the universal joint, and if either bearing is worn or loose or seized then the U/J joint can't rotate freely in a turn or a crash. So what happens is the deckplate is instead put under leverage load or torque load it is not designed to take. (And if that is the case then it doesn't matter how many bolts your deckplate has.)

Note that people who complain their single-bolt deckplate comes undone invariably have this problem, due to the mast extension and deckplate bearings not working properly.
One way to test this on any gear is to attach the deckplate and mast extension to the board, but without the sail or mast. You then hold the board flat and try and bend the mast extension towards the rail, and then try and rotate the mast extension towards the board nose or tail. Where both bearings can't rotate freely, you'll see the deckplate being put under strain, or else the U/J joint itself tries to twist. This bearings issue is also why U/J joints can break unexpectedly.

In this case, if the bearings of the deckplate and mast extension could not rotate then any crash could result in the falling rig easily levering the deckplate from the board, breaking the mast track in that process.


Just a thought - but a common problem which many do not seem to be aware of.

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Carantoc said..

Doggerland said..
"Swimming good, carefree carbon pole dancing better"
free after Snowball&Napoleon 1984

yeahhhh, I dunno.
Somehow I'm still thinking eccentric nuts.

Undersized nuts.

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Basher said..
Hi, I'm a bit late to this thread, but I'm also wondering if the analysis of the problem so far is correct.

One of the issues people have with their deckplates and mast tracks is actually caused by their U/Js not rotating correctly.

There should be a rotating bearing either side of the universal joint, and if either bearing is worn or loose or seized then the U/J joint can't rotate freely in a turn or a crash. So what happens is the deckplate is instead put under leverage load or torque load it is not designed to take. (And if that is the case then it doesn't matter how many bolts your deckplate has.)

Note that people who complain their single-bolt deckplate comes undone invariably have this problem, due to the mast extension and deckplate bearings not working properly.
One way to test this on any gear is to attach the deckplate and mast extension to the board, but without the sail or mast. You then hold the board flat and try and bend the mast extension towards the rail, and then try and rotate the mast extension towards the board nose or tail. Where both bearings can't rotate freely, you'll see the deckplate being put under strain, or else the U/J joint itself tries to twist. This bearings issue is also why U/J joints can break unexpectedly.

In this case, if the bearings of the deckplate and mast extension could not rotate then any crash could result in the falling rig easily levering the deckplate from the board, breaking the mast track in that process.


Just a thought - but a common problem which many do not seem to be aware of.

I completely agree with Basher. I had a similar experience with my single bolt deckplate three years ago. An experience that I do not want to remember. Thanks to the kiter who dragged me back to shore holding his knee with one hand and pulling the rig with my other.. 40 howling knots. strong current, 3m swell, grey skies, grey sea... board gone, 200-250 m from land.. Swim ? With all this water boiling? Ha-ha .. gloomy and doomy.. Check your deck plates- this could save your life.

consider Occam's razor for the shiniest (UJ)nuts.

I'd like to see an engineer's take on Basher's hypothesis ..... as I just dunno.

The mast is acting like a lever, and torque applied around the bolt axis is not going to make any difference to my thinking. If the track is crap it will break. They very very rarely do, and this one was crap. So far, yes, the analysis is correct as the manufacturer said his 3D printing experiment didn't work.

(Yes longboard boxes break, and brittle rubbish boxes break in foil applications, but I'm talking about proper mast tracks on wave boards)

MSc El/Mech Engineer here (previous life but). Some lever action, ok... but good luck to anyone trying to propagate torque thru the extensions/uj clip 'n groove connection..
(to add, there used to be unipiece europin diabolos around and they were +-okay as i saw some very accomplished wavesailors put them thru the tests)

Yeah thought so

The way I see it is..... if the bearings have seized or don't spin nicely , the force of the sail flipping around the mast axis is a force. When crashing or going through the rinser and there is a levering action going on trying to rip the nut out , there can be added force generated from a seized non spinning sail which may add to , or detract from the levering force .( depending on how the sail is twisting compared to the lever action ). So if the nut is almost being levered out , the extra twist force may be the straw on the camels back. However if the lever force is enough to rip the nut out , opposite twisting force may reduce the levering , saving the day . I believe it to be a 50/50 thing. So to my thinking , on average , it doesn't matter if it spins or not in a crash situation.
A non spinning base will flog out the joint quick smart. Actually , you couldn't sail with a seized base and will break the tendon first jybe. Or unscrew the base . Or over tighten it. So if your actually sailing the thing , it must be spinning therefore not adding any force , or very little. Unless it seizes mid sail........

Just to be pedantic, there's gotta be some torque load on the box and screw.

Until North come up with a superconductor floating magnet UJ system#, then even a brand new base covered in the finest German grease isn't frictionless, so every time the mast turns (like continuously when sailing) some torque is applied to the box.

But, yeah, I'd assume that the base would have to be severely compromised (corroded solid or something that you'd notice just in the feel of the rig) for a reasonably constructed box to fail because of the torque load before something else spins. There are plenty of bits to move and not transmit much torque.


- oh yeah, for pedantics sake, if that torque (and every other load from the rig ) is applied to two bolts then each will see less load than one would. How much will depend on relative stiffness and load paths, but it would be pretty unlikely for one bolt to be always taking all the load (unless it ain't done up or something)

And if the two bolts both have a nut then the load is spread over a greater area of the box and punching or shear failure of the nut on the box slot is less likely to occur.



#the North Zero-Mu will probably only work within a couple degrees of absolute zero, so will be fine in the North sea anytime other than 4 days in August.

just to be pragmatic
I'll concede and revel in Gestalts diagram for explaining exotic windsurf beliefs.
It came up in the mighty legendary toe-in discussion and it is a great ancillary to Godwins Law

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Carantoc said..
Just to be pedantic, there's gotta be some torque load on the box and screw.

Until North come up with a superconductor floating magnet UJ system#, then even a brand new base covered in the finest German grease isn't frictionless, so every time the mast turns (like continuously when sailing) some torque is applied to the box.
...

#the North Zero-Mu will probably only work within a couple degrees of absolute zero, so will be fine in the North sea anytime other than 4 days in August.

Yea, but North won't do that...they will wait until someone else starts selling one and then they will copy it

The reason the gorilla holding the plane wing couldn't hold a steady line was because of a sticky base. The Gibbons was rotating smoothly .It's obvious now.

Yep. All that extra weight from the gorilla and the plane wing and the non rotating mast base caused this catastrophic failure, and the sketchy line.

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Imax1 said..
Undersized nuts.

The plague of speed windsurfing

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Basher said..
Hi, I'm a bit late to this thread, but I'm also wondering if the analysis of the problem so far is correct.

One of the issues people have with their deckplates and mast tracks is actually caused by their U/Js not rotating correctly.

There should be a rotating bearing either side of the universal joint, and if either bearing is worn or loose or seized then the U/J joint can't rotate freely in a turn or a crash. So what happens is the deckplate is instead put under leverage load or torque load it is not designed to take. (And if that is the case then it doesn't matter how many bolts your deckplate has.)

Note that people who complain their single-bolt deckplate comes undone invariably have this problem, due to the mast extension and deckplate bearings not working properly.
One way to test this on any gear is to attach the deckplate and mast extension to the board, but without the sail or mast. You then hold the board flat and try and bend the mast extension towards the rail, and then try and rotate the mast extension towards the board nose or tail. Where both bearings can't rotate freely, you'll see the deckplate being put under strain, or else the U/J joint itself tries to twist. This bearings issue is also why U/J joints can break unexpectedly.

In this case, if the bearings of the deckplate and mast extension could not rotate then any crash could result in the falling rig easily levering the deckplate from the board, breaking the mast track in that process.


Just a thought - but a common problem which many do not seem to be aware of.

This is not a common problem. I never experienced this in 40+ years of windsurfing.

^^^ Me either in 33yrs windsurfing, and now repairing almost every broken windsurfing board in WA.

But windsurfing isn't real big here, and WA is not a test of the gear at all. Blokes here are pretty easy on their stuff too. Waves are infrequent and small, wind averages 12-15kn in the season.

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Mark _australia said..
^^^ Me either in 33yrs windsurfing, and now repairing almost every broken windsurfing board in WA.

But windsurfing isn't real big here, and WA is not a test of the gear at all. Blokes here are pretty easy on their stuff too. Waves are infrequent and small, wind averages 12-15kn in the season.

Steady on Mark, Septic's aren't renowned for understanding sarcasm or irony.

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John340 said..

Mark _australia said..
^^^ Me either in 33yrs windsurfing, and now repairing almost every broken windsurfing board in WA.

But windsurfing isn't real big here, and WA is not a test of the gear at all. Blokes here are pretty easy on their stuff too. Waves are infrequent and small, wind averages 12-15kn in the season.

Steady on Mark, Septic's aren't renowned for understanding sarcasm or irony.

That's what makes it fun

Hi, it's me again, and with some repetition.

If ever you find your deckplate is unscrewing from the board, the chances are you think you never did it up tight enough in the first place. Some people - for whom this happens a lot - then turn to the Chinook two-bolt system.

But in some cases - not all - the issue is actually that the U/J bearings are not rotating properly.

Some people are even so naive to think you only need one bearing - and we've had threads on that - with just one bearing below the U/J, and they tie things to the U/J itself, like the sail tack strap, bridging the second bearing between the mast extension and the U/J .

I know really good sailors who thought their board deck needed regripping, because the deckplate would constantly slip or undo itself. And the real problem is often that one or both bearings are worn, so they don't rotate easily when under load.
Without two bearings, the forces on the deckplate are different.


When the rig is upright, the rig rotation is simple because both bearings are in the same plane, allowing you to sheet in and out, and to tack and gybe. The mast can rotate above the U/J or else the U/J can rotate in the deckplate, or both turn.
But when the rig is in the water, and you are setting up a water start, the U/J is stretched and both bearings are under sideways load, and that can cause them to seize up.
For example, when the rig is laid on the water, the bearing below the U/J allows you to move the mast towards the wind or to lay the mast and rig weight on the board tail for extra buoyancy. If you need to flip the rig when the mast is laying in the water, then the bearing above the U\J is needed to do that.

If either bearing cannot rotate freely, then the U/J itself has to twist - be that a tendon or Boge-type joint. And that in time causes the U/J failure we see foo often, or else at best it shortens the natural life of the joint. The joint itself splits open and then breaks.
If you have loose/sloppy bearings on your mast extension and deckplate, then replacing a broken U/J Boge joint or tendon will not take you back to a place of safety - because the U/J rubber broke because it was under abuse, and still will be.

I'm hoping this explanation will encourage everyone to check their bearings, in the way I have already described, in my earlier post in this thread.


On topic, I do understand that here, in this instance, there may be a problem with a sub-standard mast track. But my point was and is, that if your mast base bearings are not working, both of them, then your rig will be applying both TORQUE (twisting) load to the deckplate, which typically undoes a single bolt system, or else LEVERAGE to the deckplate when the rig crashes to the water.
And that is what in these circumstances can lever the deck-plate out of the track or else lever the track from the board.

Ideally, we should see pictures of the rig set up and the extension and deckplate as used, as well as pictures of the damaged board.

don't be ignorant, press play! :)

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Basher said..
Hi, it's me again, and with some repetition.

If ever you find your deckplate is unscrewing from the board, the chances are you think you never did it up tight enough in the first place. Some people - for whom this happens a lot - then turn to the Chinook two-bolt system.

But in some cases - not all - the issue is actually that the U/J bearings are not rotating properly.

Some people are even so naive to think you only need one bearing - and we've had threads on that

I think you're trying to solve a problem that doesn't really exist. The problem with 2 bolt systems is it reduces how far you can move the mast back . Yes it matters. If a mast track is weak ,2 bolts make no difference. 2 bolt systems have an extra connection point to fail.. and they do. Use whatever floats ya boat as both systems have pros n cons and different fail points

I think basher was looking to impart some knowledge re UJs
Great.

But i can't for the life of me see how it affects the scenario in this thread.
Analogy
Think about bolting a broomstick to a bit of wood, perpendicular. Then lean on the broomstick till the bit of wood breaks.
It the bit of wood has a weak point, it matters not if the bolt was finger tight, or nipped up with a spanner. .... the levering will break it.
Basher its irrelevant.

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Mark _australia said..
I think basher was looking to impart some knowledge re UJs
Great.

But i can't for the life of me see how it affects the scenario in this thread.
Analogy
Think about bolting a broomstick to a bit of wood, perpendicular. Then lean on the broomstick till the bit of wood breaks.
It the bit of wood has a weak point, it matters not if the bolt was finger tight, or nipped up with a spanner. .... the levering will break it.
Basher its irrelevant.

Correct

But a non spinning base can add leverage to your broom handle. Install your base and extension and lever it down until it hits the side of your board. Then spin the extension . Depending on the situation , that friction that you feel spinning the ext can be added or subtracted to the overall levering force. It would be minimum , but there , depending on how much friction there is.

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Mark _australia said..
But i can't for the life of me see how it affects the scenario in this thread.

Just to state the obvious ........

I took the scenario to be what Doggerland initially said it was in the question this thread commenced with :

nut of the base bolt cleanly ripped through the mastbox. Similar damage on both box sides, clearly the contour of the nut simply removed clean chunks of plastic . ... Box is likely Chinook.

The pics then appear to show exactly that - i.e. the nut has come out and ripped material from each side of the box. Yes, there is some damage clearly visible to the box coming out from the board, but from the description and photos, I took it the primary failure was nut damaging box sides, not intact box being ripped from board. Board damage could be due to box deformation as the nut wedged through it, more than a rigid box ripping from board.

Kato's photos appears to show a slightly different failure mode, more that one side of the box plastic snapped out from the slot upwards, implying simply too much total load on the plastic for it to survive, and the box remained in the board. Although, if the photo shows the damage after he has taken a grinder or router to it, then it could be anything.


So, back in the original failure, if the box is Chinook (as stated in OP) and failure was the nut ripping up and out of the slot, ripping the sides of the box but doing not much else (as stated in the OP), then failure would most likely be nut being too narrow.

Nut too narrow either because it was too narrow, orientated in such a way it became too narrow or perhaps, as Basher is indicating, was fine on installation, but then became loose due to everything else having a higher torque strength and turning, twisting, damaging box, widening a hole, then being too narrow because the rest was too sloppy.

However, as we have now learnt, the box wasn't in fact Chinook but was cheese, and Doggerland's nuts are majestically large, then I feel this issue is fairly obviously solved.

Yeah, it's a dodgy box.
But were at the end of the second page. By this stage we should be arguing and insulting each other. Its tradition.

Last thing you want is a dodgey box..

I have 3d printed quite a lot of stuff with consumer grade FDM printers.
Absolutely NONE of it is structurally good enough to make a mast box out of by itself. ie MASS printed plastic part in the style of an injection moulded chinook box. In my view this would be an absolutely terrible and unsafe idea. There are other printing processes and qualities of machines that can give much greater structural strength. I have not come across any plastics ones that can do the same strength as injection molding though, not in "practice" anyway.

That said perhaps the 3d printed part was used in conjunction with some composites to make the track- this then isn't necessarily intrinsically bad, it could be a bad implementation of a possibly successful idea.

What i have learnt, to my cost is that its a bad idea to practice on your customers, as when it goes wrong, its your stuff that looks ****.