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PostPosted: Mon May 02, 2011 2:31 am 
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Location: Hilo, Hawaii
Inspected my TI today, and it looks like I need to be added to the list of TI owners whose akas are experiencing excessive play where it's inserted into the knuckle joint due to rivets loosening.

There was previous mention of this issue in an earlier post:
http://www.hobiecat.com/forums/viewtopic.php?f=75&t=33895

Aloha,

c2y


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PostPosted: Mon May 02, 2011 4:31 am 
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I took my TI out yesterday and noticed the same thing while washing down the boat. There is play in the aka tube as it sits in the die-cast socket. I believe that there is dielectric corrosion going on between the aluminum and the stainless rivets. A better design might have been to through bolt the joint with mylar sleeve and washers to keep the metal apart.

This is one of those situations that will get worse with time. I wonder if Hobie has any recommendations???

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PostPosted: Mon May 02, 2011 9:00 am 
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My TI's "joints" seems to be getting looser also. :(

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PostPosted: Mon May 02, 2011 11:56 am 
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Location: Hilo, Hawaii
Matt,

Is this a warranty issue? I'm liking the knuckle design but the alluminum rivets doesn't seem to be holding. Please advise on a possible remedy.

Here's a short video of the issue:
http://youtu.be/W9Cj81Waev0

I'm tempted to drill them out and replace with a larger marine stainless steel screw/bolt. And utilize mylar or polyurethane washers to help prevent electrolysis and provide some buffering.

c2y


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PostPosted: Mon May 02, 2011 2:29 pm 
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Very clear video. This has been observed over here on Oahu as well.

The corrosion seems more advanced on yours, (which I am sure is an older and more used hull). But the play in the rivets has been seen, even on the newer TI's.

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PostPosted: Mon May 02, 2011 4:28 pm 
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I had this problem and due to the fact my dealer is a bit of a drive away I just bought some stainless rivets at WMarine and replaced them myself. I think they are 3/8 diameter by 1/2 long but Matt should confirm. Just use the same size drill and drill out the old and then go to Harbor Freight to get a heavy duty pop rivet puller. The one handed pullers are not up to the task of forming a stainless rivet. So far they are staying tight but I have not done as much as the EC attempt or the Everglades trip with Keith to test them. What I did see is the corrosion is the problem and I have started rinsing these out each use and hanging the akas with the joint high to allow the water to drain and dry out.


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PostPosted: Tue May 03, 2011 11:59 am 
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bosab,

Thanks for the advice on storing aka knuckle up. Researching heavy duty stainless steel rivets and tool (bolt cutter style) for now. Seems like a maintenance item we need to pay attention to since it's in an area subjected to many stresses.

cheers!

cliffs2yak


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PostPosted: Wed May 04, 2011 1:59 am 
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Location: Gippsland Lakes Victoria Australia
cliffs2yak wrote:
Matt,

Is this a warranty issue? I'm liking the knuckle design but the alluminum rivets doesn't seem to be holding. Please advise on a possible remedy.

Here's a short video of the issue:
http://youtu.be/W9Cj81Waev0

I'm tempted to drill them out and replace with a larger marine stainless steel screw/bolt. And utilize mylar or polyurethane washers to help prevent electrolysis and provide some buffering.

c2y

cliffs2yak - we are aware of this problem down here too and not only wash thoroughly, but spray liberally with WD40 in the hope we can prevent this.
Having said that, I don't think there is one of us that has not noticed that loose play is developing on our new 2011 AIs/TI.
One of my mates has just had his akas replaced due to excessive play and noticeable galvanic corrosion - after just 3 months use :shock:
Not sure that replacing the rivets with marine SS will fix this as you will have the problem of dissimilar metals.
Monel rivets may be a better solution but I would still use some form of barrier paste as well (like liquid plumbers tape - part of the loctite product range from memory). Trouble is Monel is something like 4 times dearer than SS :shock:

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PostPosted: Wed May 04, 2011 5:54 am 
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Found lots of relevant info here
http://www.finishing.com/271/67.shtml

Here's a sample:
Quote:
I have an application were I have a 1/4" thick plate of aluminum in direct contact with a sheet of 304 Stainless Steel. Also I want to use an all aluminum pop rivet (both body and mandrel made out of aluminum)which will fasten the 1/4" thick plate with stainless steel. This application will see sea coast environment (but not an underwater application). Is there a chance of galvanic corrosion especially the pop rivets weakening out? I am looking for a quick solution. I looked for similar stainless steel pop rivets, but they are not available in the time frame I need to work with.

Quote:
Aluminum in a seacoast environment is not a long term proposition. However, you may want to consider using stainless steel fasteners. The rate of galvanic corrosion is related directly to the ratio of cathode area (stainless) to anode area (aluminum). In other words a relatively small anode area like an aluminum pop rivet will be attacked much faster than a large one like the 1/4" plate. Good luck

This next quote is well worth reading too:
Quote:
Picture a conventional dry cell battery still sitting in it's original packaging. The shell is made of zinc while the center rod is carbon/graphite. The two dissimilar materials are not touching each other, but there is an electrolyte, a salty liquid path between them (the black glop). Nothing is happening so far, and the battery will have a long shelf life.

Now take the battery out of the package and, with two pieces of wire, connect a flashlight bulb to the battery. We know that the bulb will light. Here is what is happening: electrons flow out of the negative pole of the battery (the zinc side), through the wire and bulb, causing it to light, and back to the positive pole (graphite) of the battery. Inside the battery, the zinc metal at the surface has become positively charged zinc ions (zinc atoms from which one or more electrons have been removed) and they dissolve and start traveling through the electrolyte glop and meet up with their electrons once again at the graphite rod and become metallic zinc once again, depositing on the carbon. There is a balance here that allows current to flow: the wire connection provides a path for the electrons, the salty glop provides a route for the positively charged zinc ions.

Note what was required for the battery to function: the two different materials for the two electrodes (zinc and graphite), an electrical path (the wiring) and an ionic path (the salty glop). You cand also make a battery using aluminum for the negative pole, stainless steel for the positive pole, rainwater contaminated with road salt as the electrolyte through which ions can travel, and a physical connection between the aluminum and stainless for the electrons to travel. If you have all of those conditions you have a battery or a 'galvanic corrosion cell'.

If you can keep the aluminum from touching the stainless, as Tim C suggested, you have no path for the electrons and the corrosion stops, similarly to removing the wires from the battery. If you can keep the area totally dry and absolutely free of salt, you have no ionic path and the corrosion stops. But what usually happens with the stainless rivets in aluminum is you have everything you need for the aluminum to corrode away into the salt water as ions.

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PostPosted: Wed May 04, 2011 10:09 am 
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Location: South Florida
Gentlemen,

A long, long time ago, I complained bitterly on this forum about galvanic corrosion on the akas of my 2007 AI due to stainless steel pin in contact w/ the aluminum akas/crossbars. It was causing the paint to flake off extensively. Hobie generously replaced my akas/crossbars. At the time after thoroughly washing my akas/crossbars, I was storing my akas horizontally. The problem with horizontal storage is ANY SALTWATER INSIDE THE AKA is just going to sit there causing corrosion. Starting this past year, I have been hanging my akas so that they drain. Also, I spray them extensively with anticorrosion/water inhibiting spray.

To put stainless steel rivets in the enlarged holes just aggravates the problem. Of course, if you could remove the steel/aluminum contacts, you would solve much of the problem, but that is easier said than done. In the mean time, I think it is very important to be able to wash the inside as well as the outside of the aka/crossbar. I am going to drill access holes in my akas/crossbars. I will also put some drain holes in so that when the akas are hung vertically, they will drain. I store my wife’s boat and my boat (I plan to get another one) on the rails so the crossbars can also drain.

It would be nice if Hobie would come up with a solution for in-service boats, as well as future boats.

Keith

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PostPosted: Wed May 04, 2011 2:44 pm 
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Location: Hilo, Hawaii
Thanks all for your inputs.

When I flipped my akas around to store knuckle up, water came dripping out. It looks like I need to drill access holes somewhere on the opposite end to allow water to drain.

Almost afraid to disassemble the aka from the knuckle since I suspect hidden corrosion damage. But, it'll have to be done to ensure I don't experience an aka separation at a bad time.

To help minimize metal - metal contact, a protective coating on the aka before reassembly and sealant on the rivets sound like a good idea.

Researching...

cliffs2yak


Last edited by cliffs2yak on Wed May 04, 2011 9:44 pm, edited 1 time in total.

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PostPosted: Wed May 04, 2011 7:33 pm 
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Location: Palm City, Florida
I have used the Tef Gel products with good results for years on the trucks I build for my pressure cleaning business. I also used it when I assembled my Trailex Trailer where the stainless steel web hooks I made, came in contact with the aluminium cross bars. My TI is less than a year old and I have not seen the Aka rivets coming loose yet, but I did replace a few for a friend who's TI was older. The rivets I used were stainless steel, 3/16" (dia.) with a 1/2" shoulder.

Using something like Tef Gel in this situation may help somewhat in preventing this problem, but keeping the area washed out and lubricated with a anti corrosion spray is probably a good idea as well.

On line or at West Marine:
http://www.tefgel.com/contain.php?param=tefgel_price#

Information:
http://www.tefgel.com/contain.php?param=tefgel_infor

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PostPosted: Wed May 04, 2011 7:46 pm 
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Just remember that protectant or sealers can do the complete opposite to what is intended if the surface isn't completely dry and salt free. If water or salt deposites are on the rivet or surface and then covered and trapped in under a protectant, the corrosion will accelerate.

My personal method of keeping corrosion at bay is to completely wash and dry the Akas, then lick ( yes lick ) some of the rivets. If there is any salt left you will immediatly taste it and then know if it needs more washing ( it's a good idea to do this with your camera as well ). Then smear a liquid car wax over the joints and surfaces. It's less messy than RP7 or WD40, doesn't get all over everything else that touches them, smells a lot better. It also doesn't wash off as easily and the salt water also beads off better than by using the repellent sprays.

( P.S. Don't let any of your family members see you licking your Amas. No matter how much explaining you do, they will never believe you )

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PostPosted: Thu May 05, 2011 1:30 pm 
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Slaughter, that's way too much information to be sharing with the rest of us. :roll: You need counseling my friend, or at least try to find some mint flavored car wax. :P

I should have thought more about this whole rivet/corrosion issue, however I'd like to correct what I previously said about "lubricated with a anti corrosion spray is probably a good idea too"... Not! :oops:

Slaughter may have a weird love affair with his Aka's, but he's right about avoiding trapped salt deposits. In addition, spraying them with a lubricant could actually accelerate the loosening of the rivets thus contributing more to the galvanic corrosion problem.

The Aka joint is a point of great stress and movement. I'm sure Hobie must have a good reason why they're using stainless steel rivets as opposed to welding this connection tight. I counted 30 places on my cross bars where stainless steel screws go into the aluminum. I see no corrosion or loosening yet because these connections are tight and or were installed with Loctite.

Inevitably there will always be corrosion with dissimilar metals in salt water environments. I think this falls under the category of long term maintenance care. The key to the Aka rivets problem is to keep them as clean and dry as possible. When mine become loose I will replace them and use Tef Gel inside the hole before installing the rivet.

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PostPosted: Fri May 06, 2011 4:36 pm 
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Spot on sun E sailor. I never thought about the lubricant being designed to actually lubricate and if any movement is there in the joint, will only help accelerate the movement.

Also some comments about sealants. Things like 'Sealastic' should be well researched before placing on any joint due to the pH level. Some are acidic and again can cause a greater problem especially if salt water is around.

So the joint is actually Locktited as well as riveted ? Is that a certainty ? Makes sense.

sun E sailor wrote:
Slaughter may have a weird love affair with his Aka's,


I can't wait to get back from a sail. Sit down with a bottle of Tequila and a lemon, whip out the tongue, and have my own little party. 8)

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