bent striker rod

i was making a righting pole for my hobie 16 and when it was on its side i noticed a slight bend on the dolphin striker rod. is the bend going to cause it to break? should i get a new one? thanks




--
Angelo
1983 Hobie 16 Cat fever #55697
2008 laser 4.7/radial #190471
SARASOTA, FLORIDA
S.S.S
S.Y.S.P
--
http://i1198.photobucket.com/albums/aa460/optikid/20130414_135907_zpsd5c5d6a5.jpg
http://i1198.photobucket.com/albums/aa460/optikid/20130414_135830_zpse3bcd731.jpg
http://i1198.photobucket.com/albums/aa460/optikid/20130414_135900_zps45a85bb2.jpg

--
Angelo
1983 Hobie 16 Cat fever #55697
2008 laser 4.7/radial #190471
SARASOTA, FLORIDA
S.S.S
S.Y.S.P
--
It's probably fine, I would gently try to straighten it. I've had several boats with bent rods like that from people tying them to a trailer or other object. I just used my foot to gently straighten them all and was good to go.

--
Greenville SC

Offering sails and other go fast parts for A-class catamarans
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If that doesn't work, a stainless rod is easy enough to come by.

--
Rob
OKC
Pile of Nacra parts..
--
I agree, doesn't look too bad. I've sailed on worse. It should probably be replaced at some time but you can probably use it for a season or two.

--
Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
--
i can get one easily but if its not bad i was just going to use it.

--
Angelo
1983 Hobie 16 Cat fever #55697
2008 laser 4.7/radial #190471
SARASOTA, FLORIDA
S.S.S
S.Y.S.P
--
http://www.thebeachcats.com/pictures/?g2_itemId=102531
Hey guys, how bad does this look? Can I use it for the rest of the season? Seems like trying to straighten it will just weaken it more. Looks like a real pain to replace and I just want to sail this thing.
Sorry, I have an hour trying to get the image in the post... this is the best I could do.

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=102534&g2_serialNumber=3

Is this your image?

Looks like someone de-masted with the pin in.

--
Ron
Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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i'd be tempted to leave it on and NOT try to straighten it

as taking it off looks like it's going to be messy...
nacra55http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=102534&g2_serialNumber=3

Is this your image?

Looks like someone de-masted with the pin in.


Yep, Guilty. I must have missed that memo.
Ron, What do you think of sailing it for a season? I'm no racer.

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
The downside Scott, is the mast ball will sit on an angle. If you analyze the forces, they will no longer be pushing the ball straight down onto the pin. The mast will not ride on the top, but biased to the side of the ball.
Am I correct in thinking that is a 9/16" rod, with a 1 1/2" ball?
I have a spare rod that I could lend you for the season, but shipping it back & forth is probably 1/2 the cost of a new one.
I would straighten it, you can bend 304 SS that amount with little loss of strength. Then use it for the summer, & have new one built...see my album here. (By the way, to post an image, right click the image then select "copy image location". Then click the 3rd tab, (IMAGE) just below where you are typing the post. That will insert a couple of brackets & IMG into your post. Put the cursor right between them & paste the link from the photo that you copied, voila!)
http://www.thebeachcats.c…ictures/?g2_itemId=73301
There are 2 ways to straighten, on or off the boat. The album shows how to get it off. If you elect to do it on the boat, you will need 2 extra nuts, & I mean the ones on the rod! They are 9/16" NF, I believe it is 18 threads/inch. Thread them on, & turn them down to 1/4" above the start of the bend. Line them up so you can place a deep socket over both of them. Place a long extension into the socket for leverage. Now comes the tricky part, you will need someone strong underneath to positively hold the rod, you should not use the beam alone to hold it. Go a little at a time, you don't want to overbend it, & don't look for perfection. It will bend to within a millimeter or two of true.
When you do go to replace the rod, you will most likely have to cut it. If the rod straightens OK, you MIGHT be able to turn the nuts off the top, but generally it takes very little bend to prevent that. There are most likely only threads 1/2 way down the bottom of the rod, so they won't come off that way.
If you get in a real bind, let me know,& we'll look into a loaner.



Edited by Edchris177 on Jun 04, 2013 - 08:11 AM.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--
QuoteYep, Guilty. I must have missed that memo.

Did you dismast while sailing, or was it while lowering the mast?
Remember, when lowering YOU MUST ROTATE THE MAST 90* SO THE DS ROD LINES UP WITH THE SLOT.
This photo shows my mast lowered correctly,notice I was an idiot & turned it 90* the wrong way, making removal of my ghetto mast pin(bolt) impossible. I said screw it, & got the bolt cutters.
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=80849&g2_serialNumber=4

In this photo you can clearly see why dropping the mast in any position but 90* results in a bent rod.
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=76386&g2_serialNumber=4

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--
Had this happen on a 5.8 couple weeks ago. The skipper just came back next morning with a 4' long hollow steel tube that fit perfectly over threaded rod. Took 10 seconds to bend it back upright. Pete
Thanks for the quick comments and your time.
BIG disappointment here, I was rigging it for the first time in the driveway to confirm it was all here and I could make it work. I was lowering the mast.
I was well aware of the 90 degree rule and thought I was following it.... my best guess is that it was a combination of the mast a couple degrees off center and not quite turned 90 degrees. There was a lot going on, watching the mast, watching my feet coming near the rear beam, the whole tramp/trailer hitch rocking moment, and the thing feels heavier than I expected, leverage I expect. I had plenty of help. No excuses just stupid here.
The old style foot does not leave much room for a mistake.
Yes, 1 1/2" ball. I even remembered to start the pin on the correct side.
I'm headed to the hardware for nuts and a try at straightening.
Thanks again comrades. I'll let you know how it goes.

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
I had two extra front 16 racks but just scrapped out one. I did not want two sitting around. If you want one let me know.

My sailing buddy Lance keep a boat at Anna Marie and he travels down your way often. icon_cool

Bill Kent



Edited by bill40421SE on Jun 04, 2013 - 03:55 PM.

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Bill 404 21SE
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Good call Pete.
As Pete said above, if you have a tube that will fit snugly onto the rod, it is a very easy job. If the pipe doesn't fit well, it is easy to screw the threads. Then you run into problems with threading the ball back on, or moving the nut on top of the beam.
You can use two lengths of pipe. If you have a short piece that fits well, place that on the rod, then slide any piece of pipe over the first piece.
If you do queer up the threads, they are easy to fix, assuming you haven't really destroyed them, & have a 9/16" NF die. Just turn it down the rod, though it won't go beyond the bend. It will jam there, & you screw the die.



Edited by Edchris177 on Jun 04, 2013 - 06:07 PM.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--
I've bent a rod like that twice now. Yes I'm an idiot, however I think inevitably everyone forgets to rotate the darn thing at some time, usually when you are lowering rather than raising.

The first time I just bashed it back into place by hammering the ball with a hammer wrapped in a rag. The second time I was fed up and just sailed with it, and its still bent. As long as the mast can still rotate it should be fine just leaving it bent.

--
Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
--
bill40421SEI had two extra front 16 racks but just scrapped out one. I did not want two sitting around. If you want one let me know.

My sailing buddy Lance keep a boat at Anna Marie and he travels down your way often. icon_cool

Bill KentEdited by bill40421SE on Jun 04, 2013 - 03:55 PM.
I will take it. thanks Angelo



Edited by optikid on Jun 04, 2013 - 07:48 PM.

--
Angelo
1983 Hobie 16 Cat fever #55697
2008 laser 4.7/radial #190471
SARASOTA, FLORIDA
S.S.S
S.Y.S.P
--
Ed and Pete:
I read Ed's album on the repair before I posted here. Excellent.
Pete, I got a power right system from you a couple weeks ago and I've been watching your store here, thanks.
I found that it is 9/16 w/ 18 threads and picked up two galvanized nuts. I'm looking for pipe to fit over the nuts so the threads are protected. Interesting that it will take 4' of leverage to do the job. I'm thinking big channel locks padded on the rod below and a two hundred pounder holding it to keep from twisting the beam. I'm going to try to gently bend it back to close.
Thanks for everything guys. Maybe I can get onto the water this weekend after all.

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
We didn't hold the striker below or worry about the beam, and had nothing over the threads. Ball screwed right back on. The skipper was so stoked after his first sail, then dropped me off to head north. Got a call hour later he tried to go under a bridge, hit abuttment & split bow 3' crack. He was a bit depressed, but I talked him into fixing it himself. Couple days later, he called super stoked about the fix & now a very confident sailor! Pete
I got the image in!

http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=102555&g2_serialNumber=3
New vs Old mast foot for a N5.7.
A bit more clearance probably would have gotten me by.
The boat came with a New one ready to install. Man, those Stainless pop rivets are tough.

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
The reason I suggested the nuts/deep socket, is that it gives you fine control over where the re-bend will occur.
It is not like folding a piece of paper, on 9/16" material, a short bend will occur over about 1/4", a long bend, say 90* will take over an inch. Hence if you leave the nuts 1/4" above the center of the present bend, that is pretty close to where it will re-bend.
Even if the socket drops somewhat further, the nuts will create the fulcrum.
IF you slip a pipe over, just be sure not to drop the pipe all the way down to the beam. The bottom edge of the pipe becomes the fulcrum, & you will bend it at that point.
Looking again at your photo, I see there are no threads on the top 1/4", so as Pete said, you won't have problems threading the ball back on.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--
This is after I banged on it with a wrench to straighten it up some.

https://lh4.googleusercontent.com/-pVB03P69-3Q/TIrfZA1tMFI/AAAAAAAAEy4/XDeOxBLwcgI/s800/IMAG0065.jpg

And it probably proves Ed's point above.

I had no Ed, though, so I took a hacksaw and cut the top off, then removed the bar (and left a large screwdriver through the hole to keep the compression tube in place.) Then went to metal supermarkets and bought a stainless round stock (maybe 5' long or so...) and cut it into a few pieces, then paid a buddy at a machine shop to thread the rods with a die. He did it by hand, which didn't make he straightest threads in the world (they kind of spiral and give the illusion that the rod isn't straight, but it's really just the threading on the rod) but I took the best looking one and had a working dolphin striker/mast step in no time.

The (lack of) rounded top of the stock rod was an issue for the ball, though, and I don't remember what I did to get around it. I probably should have just dremeled it but I don't think I did.

--
Rob
OKC
Pile of Nacra parts..
--
QuoteWe didn't hold the striker below or worry about the beam, and had nothing over the threads. Ball screwed right back on. The skipper was so stoked after his first sail, then dropped me off to head north. Got a call hour later he tried to go under a bridge, hit abuttment & split bow 3' crack. He was a bit depressed, but I talked him into fixing it himself. Couple days later, he called super stoked about the fix & now a very confident sailor! Pete


I love this. Nothing inspires (over?) confidence like breaking and fixing your boat.

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Rob
OKC
Pile of Nacra parts..
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QuoteMan, those Stainless pop rivets are tough.


Tough to remove or install? Right tool for the job and they're not that bad, although certainly quite a bit stronger than aluminum.

--
Rob
OKC
Pile of Nacra parts..
--
Quick question on this topic. I just purchased a Nacra 5.5sl. Only thing wrong with it was the dolphin striker being bent. I purchased a new one from Murrays. Their directions indicated putting silicon on the threads as well as on the support casting. Is the silicon necessary? Is there anything special needed to lock the nuts. Any help on this is appreciated. Btw not trying to hijack the thread. The question seemed relevant to the topic. If I should have started a new thread let me know. More dumb questions regarding my purchase will be on their way.

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Gary
Stevenson Ranch, CA
Nacra 5.5sl
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I imagine that they recommend the silicone b/c the rod and bolts are stainless, while everything else is aluminum. They'll corrode the aluminum in salt water or coastal regions if they're touching.


I don't think you need to bother with anything to lock the nuts, but that's just IMO, others may disagree.

Congrats on the 5.5. That's a fun boat.

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Rob
OKC
Pile of Nacra parts..
--
As Yurdle said, it prevents galvanic corrosion between aluminum & SS. By silicon, I would use silicon grease, or any other thick grease if you don't have it. Coat the portion of the rod that sits inside the compression sleeve, inside the beam.
I have never worried about the support casting. The casting is aluminum, the rod just sits in a depression, there are no threads or fine tolerances to seize. Anything you put there will wash out pretty quick.
I had aircraft lock nuts,(nylock?) on 2 of the rods, the others were plain. I would not use Loctite etc. I have not ever seen them back off, they are not subject to much vibration. I have never used any grease or anti seize in that area as it is SS to SS.
Be sure to pretension the beam 3/8". Then turn the top nut down snug against the beam,I mean "snug", not gorilla force. Occaisionally give an upwards yank on the V brace strap, it shouldn't move more than 1/4". If it does, tension the beam a bit. don't forget the big washer top & bottom, or you'll crunch the beam

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--
Edchris177/yurdle thank you for the response and the very complete explanation. Very much appreciated. Believe me there will be more questions to come and it is nice to know that there is a knowledgeable group willing to share their experience/knowledge. I am looking forward to getting the 5.5 out on the water.

--
Gary
Stevenson Ranch, CA
Nacra 5.5sl
--
Edchris177The reason I suggested the nuts/deep socket, is that it gives you fine control over where the re-bend will occur.
It is not like folding a piece of paper, on 9/16" material, a short bend will occur over about 1/4", a long bend, say 90* will take over an inch. Hence if you leave the nuts 1/4" above the center of the present bend, that is pretty close to where it will re-bend.
Even if the socket drops somewhat further, the nuts will create the fulcrum.
IF you slip a pipe over, just be sure not to drop the pipe all the way down to the beam. The bottom edge of the pipe becomes the fulcrum, & you will bend it at that point.
Looking again at your photo, I see there are no threads on the top 1/4", so as Pete said, you won't have problems threading the ball back on.


Thanks Comrades. I used to bend my sons steel axels to adjust camber and caster on a soap box derby car. Ed's info was a good refresher. Here is the repair and my tools. I used two nuts for better control. I read Ed's album here: http://www.thebeachcats.com/pictures/?g2_itemId=73301 Excellent primer, nice work.

https://mail.google.com/mail/u/0/?ui=2&ik=e6d55c8fd5&view=att&th=13f26b2e39612a27&attid=0.1&disp=inline&realattid=1437329046044147712-1&safe=1&zw

May not be perfect but I expect it to get me through the season.

https://mail.google.com/mail/u/0/?ui=2&ik=e6d55c8fd5&view=att&th=13f26b2e39612a27&attid=0.3&disp=inline&realattid=1437329046044147712-3&safe=1&zw

Hoping I did not hijack the thread either.

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
yurdle
QuoteMan, those Stainless pop rivets are tough.


Tough to remove or install? Right tool for the job and they're not that bad, although certainly quite a bit stronger than aluminum.


Install.....I have not used stainless pop rivets before. I have what I thought was a decent tool, but apparently it is lacking leverage. It took everything in my old arthritic hands to snap those rivets.

Thanks again guys!

yurdle
QuoteWe didn't hold the striker below or worry about the beam, and had nothing over the threads. Ball screwed right back on. The skipper was so stoked after his first sail, then dropped me off to head north. Got a call hour later he tried to go under a bridge, hit abuttment & split bow 3' crack. He was a bit depressed, but I talked him into fixing it himself. Couple days later, he called super stoked about the fix & now a very confident sailor! Pete


I love this. Nothing inspires (over?) confidence like breaking and fixing your boat.


Confidence increasing, over-confidence on the way!

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
Go to Harbor Freight and get yourself a wishbone type pop riveter (Princess Auto in Canada). Best $15 you will spend on your boat, the normal riveters just don't have enough leverage for normal people to pop more than one stainless rivet per day or so and you might break them.

--
Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
--
WolfmanGo to Harbor Freight and get yourself a wishbone type pop riveter (Princess Auto in Canada). Best $15 you will spend on your boat, the normal riveters just don't have enough leverage for normal people to pop more than one stainless rivet per day or so and you might break them.

http://www.harborfreight.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/i/m/image_16310.jpg

Is this it? Looks a bit more substantial.
Mine is an Ace Hardware and looks pretty standard. You are right about the limited number per day. I didn't think I could do any more than three a day with it. My Power right system is going to take about ten rivets and I didn't know how I would get it done? So, this is the answer?
Scott

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
klemensIs the silicon necessary?
Gary

Yes. Here's why . . .
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29659&g2_serialNumber=4
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29658&g2_serialNumber=4

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Philip
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QuoteBe sure to pretension the beam 3/8". Then turn the top nut down snug against the beam,I mean "snug", not gorilla force. Occaisionally give an upwards yank on the V brace strap, it shouldn't move more than 1/4". If it does, tension the beam a bit.

It seems obvious, but I know people have forgotten this, I should have added, BE SURE TO BACK OFF ON THE TOP NUT BEFORE TURNING THE BOTTOM ONE UPWARDS!

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--
scotts1w
Thanks Comrades. I used to bend my sons steel axels to adjust camber and caster on a soap box derby car. Ed's info was a good refresher. Here is the repair and my tools. I used two nuts for better control. I read Ed's album here: http://www.thebeachcats.com/pictures/?g2_itemId=73301 Excellent primer, nice work.

https://mail.google.com/mail/u/0/?ui=2&ik=e6d55c8fd5&view=att&th=13f26b2e39612a27&attid=0.1&disp=inline&realattid=1437329046044147712-1&safe=1&zw

May not be perfect but I expect it to get me through the season.


Your pictures didn't work, it looks like you tried to link to a picture in a Gmail email message. So you can see it but nobody else can. To share photos on here you'll need to either create a photo album (Beachcats Technical for this) or upload them to something like Photobucket.

--
Damon Linkous
1992 Hobie 18
Memphis, TN

How To Create Your Signature

How To Create Your Own Cool Avatar

How To Display Pictures In The Forums.
--
mummp
klemensIs the silicon necessary?
Gary

Yes. Here's why . . .
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29659&g2_serialNumber=4
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29658&g2_serialNumber=4


Is this an issue on fresh water boats as well?

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
mummp
klemensIs the silicon necessary?
Gary

Yes. Here's why . . .
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29659&g2_serialNumber=4
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29658&g2_serialNumber=4


Is the repair for this a new beam?

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
scotts1w
mummp
klemensIs the silicon necessary?
Gary

Yes. Here's why . . .
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29659&g2_serialNumber=4
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29658&g2_serialNumber=4


Is the repair for this a new beam?



If you want to do it right, yes a whole new beam is the only way to go... I too did this repair and when I reassembled it I used some anti seize bronze paste mixed with some waterproof axle grease..

After that every year I would take it apart, clean all the components, and reassemble with the goop I mixed up.. Never had a sign of electrolysis after that.

--
John Schwartz
Ventura, CA
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scotts1w
mummp
klemensIs the silicon necessary?
Gary

Yes. Here's why . . .
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29659&g2_serialNumber=4
http://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=29658&g2_serialNumber=4


Is the repair for this a new beam?

In this particular case it was. If you have galvanic corrosion like this in one spot, you can bet that you have it in other areas. In my case, the SS dolphin striker V-bar beam bolts had caused similar excessive corrosion, not an area you want issues. Also, the aluminum compression tube inside the beam (that the dolphin striker rod goes through), was totally seized to the rod and you could no longer adjust pre-bend to the main beam. If you have a boat with these issues, you will also likely have frozen beam bolts, and if the mast is original to the boat, your tang rivets and hound rivets will also have caused corrosion to the alum they are seated in. Food for thought. . .

Two important maintenance items:
1) isolate dissimilar metals (marine grease and silicone for rivots)
2) and for those of you who have been around from the days of the old site, as John S. so eloquently stated "make sure to exercise your nuts"

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Philip
--
I understood that it is not as apt to happen in fresh water.
But stray current in a marina can trigger a problem in fresh water.... Is this correct?
What should we watch for? Just inspect? By the time one finds a problem damage has probably occurred, right?

--
Mooched Beachcats in the past
Time to try ownership with Nacra 5.7
Port Clinton, Lake Erie Islands, Ohio
--
scotts1wI understood that it is not as apt to happen in fresh water.
But stray current in a marina can trigger a problem in fresh water.... Is this correct?
What should we watch for? Just inspect? By the time one finds a problem damage has probably occurred, right?


It can happen in fresh water too...may take longer

--
John Schwartz
Ventura, CA
--
You have several things in your favour Scott, freshwater, & Ohio,(the season is much shorter, & the off season is cold).
The corrosion in the photos is a result of ion migration between metals with different electrical potentials. In very simple terms, if two dissimilar metals, in close proximity to one another, are connected by an electrolyte, ions migrate from the less noble metal. The "loser" is the anode, the more noble, or "winner" is the cathode.
In our case, aluminum is the anode (less noble). In fact it is one of the least noble metals, the only commons ones that are worse are zinc & magnesium, & it should dissolve quicker than a tin can. (I once witnessed the resurrection of a Japanese Zero, the wing spars were magnesium, & could be flaked away with your fingernail).
Interestingly, aluminum "rusts"(oxidizes)very, very quickly, so, why don't our masts & beams dissolve quicker than a common nail? The saving grace is that the result,(aluminum oxide) is a very good barrier.
Another major consideration, is the relative sizes of each piece of metal, also known as the ratio of Cathode to Anode (C/A). Many will remember the chemistry lab, where you covered a steel tray containing common salty foods with aluminum foil. The foil was pushed down onto the food with a pencil point, resulting in a few very small contact areas. This served to concentrate the electrical potential in a very small area. The foil was quickly eaten with "moth holes"at these points.
Consider the following two situations. Case A, an aluminum plate,(anode) containing an SS rivet. The rivet is more noble,(cathode), BUT it is very small in comparison to the aluminum plate, making for a small C/A. Corrosion will occur from the aluminum plate, but it will be slow, & this is what we use on our Cats, large aluminum extrusions, with small SS rivets. Incidentally, monel rivets possess the same potential as passive 304 SS.
Case B, an SS plate,(cathode) containing an aluminum rivet,(anode). In this case the C/A ratio is high, & corrosion of the the aluminum rivet will be severe, even though the electrical potential,(difference), was the same in both cases.
What lessons can we glean from all this?
Best, keep the parts out of an electrolytic substance, not possible in our case.
Better, eliminate areas where the C/A is high,(small aluminum in proximity to large SS).
Good, prevent the current from flowing between the dissimilar pieces, achieved with a barrier, ESPECIALLY WHERE THE CONTACT POINTS ARE CONCENTRATED.
This works well for the portion inside the compression tube, not so well where the rod exits the beam. The grease is quickly squished out of the way, & the contact point is concentrated against the thin wall of the beam. The problem is exacerbated by the use of the large SS washers directly against the aluminum beam. Some grease on the inside of the washers would help.
Take a close look at Philips photo, the worst corrosion is where the rod touches the beam walls. A cure could be had by enclosing the rod in a very thin plastic tube, but such a tube would not last long, the beams edges would soon cut through it.
Ultimately, what we are depending on is Case A, above. A large anode(beam) vs a relatively small cathode (rod).
In your case, the fresh water makes a much weaker electrolyte, hence less current, resulting in little or very slow corrosion. There are differences, depending on the pH value & hardness of the water, but it is much less than sea water. I personally have not greased my 5.7 in 4 years,(freshwater), I doubt if the PO ever did, & it shows zero effect,as can be seen from the album photos.
For those operating in corrosive environments, it would be an interesting experiment to utilize sacrificial anodic protection. A small zinc strip,(even better would be some magnesium wire) attached to both the rod & beam should work. It must be connected to both, then the zinc, being less noble than aluminum should become the anode. Someone should try it & report back.



Edited by Edchris177 on Jun 10, 2013 - 11:42 PM.

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