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PostPosted: Wed Aug 10, 2011 9:48 am 
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The forward crossbar on my TI is sliding side to side under normal sailing loads. Many times when I tack, the crossbar shifts to leeward with a loud "THUNK."

This is NOT a V-frame problem because the forward crossbar is not directly tied in to the V-frame. Instead, the crossbar is only strapped to two plastic saddles that are bolted to the hull atop the V-frame. The crossbar is only bolted to the top of the mast receiver with two hex-cap screws. Nonetheless, these aren't sufficient to preclude movement, as they move with the crossbar. See sketches & pics below.

The movement has not caused any damage or problems yet, and NONE of the parts on the mast, crossbar, V-frame, etc. are showing ANY wear. Moreover, ALL components and fasteners are TIGHT... like a tiger :wink: . The V-frame, its turnbuckles, and jam nuts are NOT loose, and none of the bolt holes are elongated.




Overview Sketch of Normal Crossbar Position:
Image




Crossbar Sliding to Port and Distorting the Hull:

Image




Crossbar Sliding to Starboard and Distorting the Hull:

Image




How would YOU fix this problem? Here's a blank drawing template I'm providing if you want to make a suggestion or two. Any ideas would be GREATLY appreciated!

Image




The top of the V-frame is under these two brass blind nuts embedded in the hull. The crossbar simply rests in saddles that are bolted to these nuts. Nothing here is worn.

Image




Here's the Tie-in block and mast receiver. Nothing here is worn.

Image




Here's the underside of the crossbar, and the two hex-cap screws. Nothing here is worn.

Image



I suppose it's possible that this motion is normal and even necessary, as in the way a highway bridge must flex under load. Once a bridge stops flexing, it's dead and will soon fail. However, I suspect that this motion is in fact a problem that will only get worse with time and cause a major failure. Besides, I'm tired of listening to that "THUNK" noise when I tack.

Looking forward to ANY ideas. I'd especially like to hear what the designers at HOBIE think of all this. After all, this is a major component that's critical to the boat's function. Thanks in advance!

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Houston, TX.
2010 Golden Papaya TI, "Trifurcatus"
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PostPosted: Wed Aug 10, 2011 10:02 am 
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Should not be moving.

Your documentation is excellent. You know where all of the attachment hardware is, all should be tightened up. If still moving when tight, the clamps may not be holding properly. Both the clamps and the two bolts to the receiver cup are designed to keep the bar centered. I have copied our engineers for any input.

Windy?

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PostPosted: Wed Aug 10, 2011 11:13 am 
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Barring any support from Hobie / taking your warranty in your own hands ... the obvious shade-tree mechanic fix for this would be to "lock" both saddles on either side "pinning" it so it can not move

Image

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PostPosted: Wed Aug 10, 2011 11:19 am 
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I too am experiencing this exact same problem. In fact, RC and I were both sailing together and discussing this issue. I attempted to video this occuring from inside the hull but nothing conclusive. I did find and tighten one nut on the starboard turn buckle. I was hoping that was the problem but not able to test till Saturday.

RC, great diagrams.

My was moving this much:
Image
P1030915.jpg by PhotoByMark, on Flickr

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PostPosted: Wed Aug 10, 2011 11:20 am 
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... thinking further, are the saddles simply a compression fit on the x-bar ? and is it simply a case of the saddles not being able to compress enough for a tight enogh friction joint to hold them ?

I'd try lining the saddles, both top and bottom with a few layers of non-slip toolbox liner to build up the apparent diameter of the X-bar and also giving it some grip

Image


Of course, a few wraps of duct tape may work just as well

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'07 Hobie Adventure Island #1
'07 Hobie Adventure Island #2 Golden Papaya AI LadyJane
'06? Hobie Outback SUV


Last edited by PassWind on Wed Aug 10, 2011 11:30 am, edited 2 times in total.

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PostPosted: Wed Aug 10, 2011 11:28 am 
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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.

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PostPosted: Wed Aug 10, 2011 2:12 pm 
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georeubs :
I had a similar problem on my TI. Mine was one of the earlier units (purchased in early 2010). After a while even with the bolts tightened up the crossbar would slide back and forth.
I notice in your drawing your Harken blocks are not in the same position as what is on my boat. Mine looks just like the picture Mark posted, with one block on each side of the brace, this pretty much limits the possible motion to under 1/4 inch, if yours is like your diagram there is nothing to stop the side to side motion to the left except the friction of the clamp (which sounds like it's worn). On my boat over time the clamp must have stretched and could no longer hold the bar tight enough (the flanges on the clamp were bottomed out) (actually I think it was because the paint had worn off the bar in that area, making it smaller). You could take a file and file off a little off the bottom of the cap (where the bolts go through, it shouldn't take much). I'm thinking it was a tolerance issue on some of the earlier designs. If you don't want to file the cap, pieces of paper laid above and below the tube will trap the bar so it can't move once you tighten the bolts ( I just used pieces 3/4 inch by 1 1/4 inch printer paper, electrical tape would also work fine), never had a problem since. Checking all the bolts (both outside and inside) on the AKA's should be a periodic check (highly recommended by dealer), they do seem to work loose, I use locktite on all that stuff now (also dealer recommended). Hope this helps
Bob


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PostPosted: Thu Aug 11, 2011 7:28 am 
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Thanks for the ideas & feedback. Also, thanks to Matt for promptly forwarding the engineers.

Matt,
Can the crossbar tolerate more holes? I too thought of pinning the bar on either side of each plastic saddle (front / back / left / right), as that's one place where a lot of strength resides. I would use a total of eight #10-24 stubby screws (so they don't interfere with the akas) each inserted into a threaded hole that I can drill & tap, no problem. Drawbacks here include the possibility of weakening the crossbar. If possible, it'd be great to hear about this from the engineers.

The ideas of using paper, electrical tape, duct tape, or toolbox liner are all intriguing, as each is noninvasive. However, possible drawbacks include: 1.) forcing the plastic hold-down straps & cradles to perform as friction clamps when they don't seem designed to that purpose, and 2.) the added bulk could stress the plastic hold-down straps and cradles thereby causing them to crack.

Currently, there's NO play nor slop in the system anywhere. ALL fittings, components, etc. are TIGHT and in like-new condition.

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RC
Houston, TX.
2010 Golden Papaya TI, "Trifurcatus"
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PostPosted: Thu Aug 11, 2011 3:00 pm 
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I can't say for sure what screws would do. Possibly point load the clamps? If the clamps are carrying the lateral load anyway... either friction or the screws should work.

We are focusing on the spacer block though. The factory has over sized the screw holes to make assembly easier. This connection is supposed to be in shear, the over sized holes may be allowing lateral movement.

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PostPosted: Thu Aug 11, 2011 6:37 pm 
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Georeubs,

Ditto - Thanks for your well done post. After addressing the issue of creeping rivets from my aka joints, I've been noticing more creeking noise comming from the front crossbar of my TI. I'll have to inspect my TI if a moving crossbar is the source of the noise.

If it is, I'm thinking stainless steel hose clamps lined with a rubberized gasket mounted outside of each mount might help prevent lateral movement.

Also, thinking of installing a bulkhead (i.e. DogsLife's post - TI Bulkhead) that might help prevent the hull from distorting in the area.

I'm suspecting that this issue had something to do with SunESailor's post about a broken V-frame bolt.

Cheers,

cliffs2yak


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PostPosted: Fri Aug 12, 2011 8:50 am 
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8) This forum is GREAT! 8) These AIs & TIs are project boats, and I like that. Keeps me busy... keeps me thinking... keeps me young.

Several people seem to be suffering this problem as evidenced by other threads on this forum. The list of people includes, but is probably not limited to:

georeubs, TxYakMan, kgound, sun E sailor, cliffs2yak

I'm sure there are many more.

To anyone else reading these posts...

If you are hearing any mysterious creeking, popping, banging, thunking, etc. coming from the forward crossbar, then YOU have this problem too.

This is NOT a case of loose or sloppy hold-down clamps. The hold-down clamps are not designed to prevent lateral movement of the crossbar under load. Rather, this type of clamp can only prevent vertical movement.

Sure the crossbar clamps can handle light lateral loads, but look at the lever and fulcrum created by the mast, receiver cup bottom, and mast bearing plate. While sailing, there is tremendous lateral leverage applied directly to the mast bearing plate AND crossbar thus making it slide side-to-side.

The ultimate fix for this problem will be something that bolts/pins/screws the crossbar to the top of the V-frame. This means one thing... a minor design change is necessary. :) Until then, we will each have to clamp the crossbar with stainless steel hose clamps (thanks, cliff2yak), and/or employ other suggestions made here.

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2010 Golden Papaya TI, "Trifurcatus"
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PostPosted: Fri Aug 12, 2011 11:27 am 
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One more thought...

This sliding of the crossbar may also be causing what's known as "cold working" of the bolt at the base of the V-frame, thus causing it to fail as in the following post: http://www.hobiecat.com/forums/viewtopic.php?f=75&t=36284.

If you're wondering what "cold working" is, get a wire clothes hanger, hold a section with two hands, and start bending it back & forth until it breaks. That's cold working.

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2010 Golden Papaya TI, "Trifurcatus"
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PostPosted: Fri Aug 12, 2011 11:55 am 
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georeubs wrote:
The ultimate fix for this problem will be something that bolts/pins/screws the crossbar to the top of the V-frame. This means one thing... a minor design change is necessary.


Not our belief. As I stated:

Quote:
We are focusing on the spacer block though. The factory has over sized the screw holes to make assembly easier. This connection is supposed to be in shear, the over sized holes may be allowing lateral movement.

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Hobie Cat USA


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PostPosted: Fri Aug 12, 2011 12:42 pm 
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Georeubs:
Like Matt says this is a known problem to Hobie and they are working on a permanent fix. The temporary fix I did by adding paper shims to the outer clamps is only a bandaid fix, not fixing the root problem.
On the older 2010 boats this problem wasn't as apparent because the Harken blocks for the furling line and sail helped contain movement to under 1/4 inch. The newer hulls with the Harken blocks in a different position makes the problem more apparent.

Below is a simple fix that I am going to apply to my boat until the official fix is released (so I can go out sailing tomorrow with piece of mind). What I plan to do is tie some of the extra spectra line which I have left over from the rudder upgrade around the V posts and the center post (using cinch knots), two layers of spectra gives you nearly 1000 lbs of pull force (shouldn't break). Then buy a couple cheap cable tighteners from the hardware store (the kind with a left hand thread on one side and right hand on the other). Tie the spectra lines in (all easily reached from the front hatch), then tighten the cable tighteners so there is no play (not too tight though). If it is possible to tie the spectra up at the top of the bar (where it ties into the hull) it would be even better. This simple fix should fix the problem for under $5 and maybe 5-10 minutes work. At the very least it should do until Hobie comes up with permanent fix to the problem and more important no modifications to the boat itelf are made, and the fix is out of the way (not seen from outside). Even with this fix applied it's still important to check all the bolts in there often, and use locktite. Basically if you have a TI and all the bolts tightened up, and you still hear the clunk noise when you tack or can see the front AKA bar going backand forth (as mine does), it's probably a good idea to apply this simple fix, otherwise you will be replacing other stuff soon( the main bolt on the bottom of the V in particular) over time as stuff fatigues and breaks, It's also possible to fatigue the hull itself where it could crack around the outer braces over time if allowed to float around. Hope this helps
Bob
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PostPosted: Fri Aug 12, 2011 1:16 pm 
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I don't think that addresses the issues above the deck line. If the V brace is snug, that transfers directly through the deck to the clamp mounts. Your setup will stabilize the receiver below deck in relation to the V Brace, but if clamps slip and the spacer block bolt holes are is wallowed out or loose... the structure above the deck line is independent and able to shift laterally.

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