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PostPosted: Fri Aug 12, 2011 1:40 pm 
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Agree - everything below deck might not move - but AKA bar could still slide back and forth.

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PostPosted: Fri Aug 12, 2011 2:08 pm 
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/agree with Miller. The picture that Mark posted clearly shows marks of the cross beam slipping within its mounts.

My engineering judgment of the internal bracing based on the pictures above is this: The lateral forces on the crossbar are intended to transmit though the two clamps. From there the force is transmitted to the diagonal brace. What this in effect does is makes the combinations of the mast, crossbar, diagonal braces into a miniature truss just like on a bridge. Or to be more specific, two triangular cells of a truss. It is a ridged structure and the forces are balanced inside that structure. This means the truss structure does not need other outside forces to be a ridged unit. Forces applied to any point of that truss (the amas, the mast, etc) are evenly spread to all points the truss contacts (4 evenly spaced points of the hull).
Why am I saying all this? The ridge truss does not NEED the hull there to be a secure ridged structure. And as long as the truss IS a ridge structure the hull will absorb forces at 4 points more or less evenly.
You proposed 'fix' will caused all the lateral force to be instead transmitted through the mast. Then from the mast the force is transmitted to your extra piece and then from there to the diagonal brace. The tension of tightening your extra piece will be transmitting from the diagonal brace to the HULL. That, as you know, is bad. You want all the forces to balance out in the metal bits and not put undue force on the hull.

Your best bet is to add some extra friction inside the clamp as others have suggested. This will caused the camps to absorb the lateral forces of the crossbar, as they are intended.


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PostPosted: Fri Aug 12, 2011 4:37 pm 
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Matt:
Looking at it again, you are correct, thats all assuming the block where the 2 screws in the center is wallowing back and forth allowing the AKA brace in relation to the block to move laterally ( I'm contending that at least in my situation it's my entire top deck thats flexing back and forth).
Before doing any changes I will scribe a line on the back of the block and AKA brace and when I go out tomorrow. I will remove my temporary paper shims from the outer braces and monitor to see if there is any lateral movement at the center block in relation to the AKA top bar and try to see where the movement occurs and will report back.
Bob


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PostPosted: Fri Aug 12, 2011 5:43 pm 
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TxYackMan wrote:
I considered increasing the diameter of the bar (via duct tape or some other means) but I am wondering why this started happening in the first place.


May I ask, how long have you used this boat (hours if possible)?

Those fittings will loosen off with time as do the turnbuckles, (based on the sea conditions and use) A check with an allen wrench might all that is needed to ensure there is no slop in the fittings. You may also consider larger area washers (if they will fit) to backup the 4 bolts on the crossbars.
If this does not resolve the issue, machining down the crossbar brackets may be required to ensure that you can get a solid fit.
Duct tape will deteriorate and loose it's thickness as the heat melts out the adhesive eventualy.
If the 'buckles' loosen off over time, it will cause a twisting motion on the front crossbar. (Considering also the extra stress placed on the fore crossbar mounting bolts added to by the motion of the mast in normal use.)
Remember there is a relatively thin plastic hull that can get thinner as the fittings work against each other.

If I were in your shoes I'd take a set of calipers to the thickness of the deck at the bolt on points for the crossbars and check it against the hull thickness from a far less stressed area.

I know we try to be as careful about maint as we can. However, considering the potential stress that is placed on 4 bolts to hold the front of the boat together, it seems more carefull checks are needed

Tropical conditions may also make a difference here as plastic, and metal contracts and swells at different rates within a very hot sealed deck in the day, and a large temp drop at night (or even in the shade).

Also consider the fact that the flat black fittings (that I saw in the photo closeups), when salt had crystalized on them, make up the crossbar and aka system in this case. (Flat black is way more heat absorbing than semi-gloss or high gloss black).

Regards
Fred

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PostPosted: Fri Aug 12, 2011 6:49 pm 
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It is a 2010 - lots of use - all freshwater.
I have checked and tightened all related fittings.
Going out tomorrow - will report back anything relevant.

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PostPosted: Fri Aug 12, 2011 7:08 pm 
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TxYackMan wrote:
It is a 2010 - lots of use - all freshwater.
I have checked and tightened all related fittings.
Going out tomorrow - will report back anything relevant.


Sorry to hear about your problems, Man. Your tag says
I'd rather be sailing,
Mark.
Yah I read you loud and clear.

If it is fresh water then your issues are less, hopefully.
First thing, I`d do is to check both of your turnbuckles. If they are lose leave them as is.
Check the Allen bolts on the crossbar fittings. If they are loose, leave them and simply put a marker on all the gear with nail polish (if your wife uses it)

This gives you the benchmark for what you are starting with. If the slop between the 2 sets of bolts is way different, I`d really suggest you get this job done by Hobie Pros or a rigging pro.
If you are doing it yourself, you will need those markers so you can equalize the load evenly on both sets of crossbar bolts, turnbuckles (counting the turns on all fittings as you adjust them). If you have a torque wrench, a simple call to Hobie should have them give you the required amount of foot pounds needed on the bolts.
However, if you need to check the hull thickness as the last possible cause, that last step will be useless if you undo the threads on the bolts, as you`ll loose the color markers.
Yah, better to take it to a rigger and let them do their magic.

I`m sure your boat`s well worth it

Kind Regards
Fred

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PostPosted: Sat Aug 13, 2011 5:00 am 
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Thanks Fred for all the suggestions.

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PostPosted: Sat Aug 13, 2011 5:10 am 
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I heard this "thunk" coming from my brand-spanking- new TI yesterday. :(


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PostPosted: Sat Aug 13, 2011 4:41 pm 
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WTF?
I can understand a 4 year old doing this, but in terms of a new boat, this bites the big one.
Yes, I read the thread that M. Miller posted that Loctite must be used at the factory level (well yah, of course seing as the major stress load is on the foredeck crossbar (even with the other brackets to support the mast)
If quality control has slipped to the point on a new boat, we have a very serious issue for any new boat owner.
If not, well consider it as a solvable problem that I'm sure will be rectified by Hobie to maintain their status as prolly one of the best builders of Sailyak in the biz.
May I respectfully ask that we give this thread a rest until we hear more from the pilots involved with this issue (new or from 4 years ago).
That is only fair for all parties involved.
May I also remind you, that due dilligence is required with any mechanical vessel that is simply a combination of surface area held together by various bolt/nut combos and careful inspection on you as the boat owner (based on very careful reading of the manual to ensure your experience will be safe, fun, and protective of your investment. (Does anyone ever bother to read manuals anymore??)
A friend of mine who owns his own Cessna prolly put it best:
Once you're launched into the air, there is rarely ever a highway shoulder to pull over to.
Come to think of it, neither does any boat unless you are sitting right in front of a Marina tied to the dock.

As Matt Miller said, this has become a Priority One for their Engineers. I have never heard any untruth from Mr. Miller or Hobie. I expect that this policy of honesty will always be supported not just for their dear customers but their own proven dedication to produce a seaworthy vessel that they would have no problem taking their own families out on.

Respects
Fred

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PostPosted: Sun Aug 14, 2011 7:37 am 
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Respectfully, we snould NOT give this thread a rest. :) There is FANTASTIC communication going on here, and we're hot on the heels of a problem that several people are having. Great ideas are being passed around, and we're all learning a lot about our boats.

20 years ago, I was a U.S. Navy helicopter mechanic. As such, I maintain my TI as though it was one of those helicopters. My boat is just over one year old, I sail in salt and fresh waters, and yet it looks brand new 'cause I routinely and thoroughly maintain it.

All of that is significant because I've been hearing this "thunk" since the FIRST TIME my boat was put to water. That first sail was releatively short, 'cause I thought for sure something had broken. Later, in my post sail maintenance routine, I found nothing out of place and was left scratching my head, wondering.

I have been wondering about that thunking/creeking/popping noise for the last year, and now, I finally know what it is and what's causing it. All that's needed is a good temporary fix, and with time, a permanent fix from Hobie. I have EVERY confidence that both will come, but only if we all keep communicating.

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2010 Golden Papaya TI, "Trifurcatus"
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PostPosted: Sun Aug 14, 2011 8:02 am 
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We're talking about lateral forces here. This means one thing. In its current design, the crossbar is, in effect, a "T". Sure, it looks like a pair of triangles, but in reality, it's a "PSEUDO TRIANGLE". That is, the CENTER of the crossbar is bolted ONLY to the mast receiver cup, and that's it. (I'll get to why the hold-down clamps don't matter.) When talking about vertical forces, this is reasonably strong. However, we're talking about lateral forces. There's practically NO lateral strength (rigidity) in a "T".

Because we're talking about lateral forces, the crossbar hold-down clamps don't play a role beyond what little friction they can contribute. Once the coefficient of friction is overwhelmed, the crossbar hold-down clamps can do nothing to prevent lateral movement. Simply put, given the tremendous lateral force from the sail, a friction clamp just can't provide the requisite friction.

What's needed is a GENUINE triangle (technically, a pair of triangles). NOTHING else will be better than that.

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PostPosted: Sun Aug 14, 2011 6:09 pm 
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I think I see your point georeubs. Is so, my question is, how far could the crossbar travel, and will it lead to the failure of any component (cracking the hull or mast bearing plate for instance).

I was out having a zesty sail on a friends 2010 TI yesterday and kept an ear out for this. Did not notice any noises on the water under stress. :twisted:

http://gallery.me.com/huipro#100109/DSC ... olor=black

Checked it on land and noticed minor slippage (maybe 3/16") to one side.

If it gets worse, I could see it becoming an issue. But I wonder if a neatly drilling a hole on top of the brace clamp and using a rivet or bolt would not easily solve this side slip problem.

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PostPosted: Mon Aug 15, 2011 6:57 am 
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NOHUHU:
If your friend has an older TI (2010) then it's likely the harken block for the sail is on the outside of the plastic outside AKA brace, and the sail reefing cleat is right next to it on the inside. (like TxYackMan's picture earlier in this post).

If his bar looks like this then the simplest quick fix might be to just put wire pull ties (also called electrical zip ties, available at Home Depot) around the cross bar on each side of the plastic outer brace. This will completely stop any side to side motion of the AKA crossbar until Hobie comes up with permanant fix.

And better yet you are not violating the hypocritic oath (make no changes to the boat itself, just like doctors LOL). If you get black pull ties, then they will blend in with the cross bar and people won't be pointing and laughing at your cobble work, (just kidding). The reason you always want black is they use 'carbon black' to color the plastic which blocks UV naturally. White or natural plastic is the worst color of all in sunlight since it allows the UV to penetrate the plastic and break down it's molecules.

Obviously the pull ties can't stop any lateral force, they are only filling the space between the AKA plastic outer clamp and the Harken blocks preventing the bar from sliding. On the new hulls, your SOL, unless you want to move your harken blocks (now in a new position on 2011 boats) to the old positions. Anything that fills the space will obviously work, a couple dots of marine epoxy would probably also work fine, I just thought the zip ties would be cheap and easy.

All the above assumes everyone is checking all the bolts and nuts in the cross bar assembly, using locktite, and checking everything regularly.

Hope this helps.
Bob


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PostPosted: Mon Aug 15, 2011 8:04 am 
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I look forward Hobie's fix of this important issue.

The lateral movement in the forward crossbar could also cause your mast collar to snap off the forward crossbar.

See http://www.hobiecat.com/forums/viewtopic.php?f=75&t=33638

This issue has been experienced by Stringy, myself, and several other TI owners. Thank you, Hobie, for promptly sending my dealer a replacement front crossbar. This was very much appreciated.

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PostPosted: Mon Aug 15, 2011 2:51 pm 
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Omigawd Bob, you just cracked me up! Hypocritic oath!?!

Is this the same guy talking who tweaked the "ultimate TI" complete with hydrofoils and spinnaker? :lol: :roll: :D And do I recall a weighted daggerboard/keel??

But yes - it has the older style blocks. And thanks, I'll mention it to my pal.

Anything solid, (used as a wedge), should be a decent temporary fix, though tiewraps do flex and would only address the issue on one side. The gaps appear to be different sizes as well, but I am going just from pictures now.

But as you suggest, for the older hulls it's uber cheap, easily removable and does not interfere with design. Those are my favorite goals. :mrgreen:

Unless Hobie engineered these bars to slide a bit, then it would seem that pinning the clamp to the bar is the long range solution.

I can't check inside the bars right now, but would this interfere with inserting the Aka retainer clips?

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