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native brookie
 Post subject: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 10:14 am 
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Location: Central Maine--Sheepscot Watershed
I'm installing vinyl gunwales on a Royalex canoe. When I purchased my gunwales, Old Town was out of rivets. They suggested I buy them from a hardware store, and gave me a sample to match.

Question: I see both stainless steel and aluminum rivets. Does it matter which I use?
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littleredcanoe
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 10:26 am 
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Location: Rattlesnake Pond ME
I would think aluminum..thats all I have ever used.

But why not call Old Town..they are not exactly that far away.

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splashdancer
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 11:15 am 
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Location: Cambridge Ontario
I seem to remember hearing that there could be a galvanic (?) reaction between aluminum and stainless? I'm not too good at scientific explanations. :doh:

Sounds like a question for....Battenkiller!

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littleredcanoe
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 11:19 am 
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I was just thinking of drilling out stainless rivets if there is another problem.. Never done it...have done it with aluminum.

hmmm

http://cr4.globalspec.com/thread/6690/G ... d-Aluminum

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native brookie
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 11:44 am 
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Location: Central Maine--Sheepscot Watershed
I don't think these rivets are going to touch anything but vinyl and Royalex, so contact with steel won't be an issue. It would be if I was installing aluminum gunwales with steel rivets. I asked Old Town when I picked up the gunwales, and had two staffers both tell me to use either aluminum or stainless.

LRC's point about drilling out steel rivets is a good one. Unless someone has a good reason to go stainless, I'm sticking with aluminum. It will save me a penny or so per rivet, too!
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splashdancer
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 12:03 pm 
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native brookie wrote:
I'm installing vinyl gunwales on a Royalex canoe.


....apparently I'm not too good at reading today either. :lol:

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Battenkiller
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 12:54 pm 
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splashdancer wrote:
I seem to remember hearing that there could be a galvanic (?) reaction between aluminum and stainless? I'm not too good at scientific explanations. :doh:

Sounds like a question for....Battenkiller!


Say what? Putting me to work, are ye? :roll: :lol:

OK, I found this link that provides a good explanation of galvanic corrosion

Galvanic corrosion is primarily a problem in marine environments, but give the large number of trippers who spend at least some of their time in saltwater, I think it is best to address it here.

Bottom line is that dissimilar metals create a galvanic cell when immersed in an electrolyte (like seawater). One becomes a cathode and the other an anode. The one that is highest on the cathodic (more noble) end of the galvanic series becomes the cathode and will corrode the least. Therefore, stainless rivets will do better in aluminum gunwales than aluminum rivets will do in stainless gunwales. The link I provided actually illustrates this exact situation:

Quote:
The approximate voltage difference for any two metals can be taken directly from Table 1. It is worth noting that marine slime films composed primarily of microscopic bacteria and diatoms can change the potentials of many of the alloys near the noble end of the Galvanic Series as indicated. The potentials of these alloys become more positive in the presence of slime films, thus increasing the voltage difference when these metals are placed in contact with more anodic alloys. This has been found to increase the corrosion rate of copper, steel, and aluminum anodes by a factor of 2 to 5, but to have no effect on the corrosion rate of zinc anodes. It may also change which metal in the couple becomes the anode.

When the two metals in a galvanic couple are close together on the series, such as manganese bronze and silicon bronze, their voltage ranges overlap, and either one can be the anode, depending on the exact exposure conditions. In this case, more detailed information than is given in this MAS Notes will be needed to predict the behavior of the couple. Several sources of additional information are listed in the Recommended Reading section.

The effect of the second factor above, the cathode-to-anode area ratio, C/A, is illustrated in Figure 1 for a rivet in a plate. In both couples A and B, aluminum is the anode, and stainless steel is the cathode. In couple A, the aluminum rivet is comparatively small, and the C/A ratio is large. In couple B, the situation is reversed: the stainless steel rivet is small, and the C/A ratio is also small. Corrosion of the aluminum rivet in couple A will be severe. However, corrosion of the large aluminum plate in couple B will be much less, even though the potential difference is the same in each case.


Since no one I know is manufacturing stainless gunwales, I think that leaves out that disastrous combo. Stainless rivets in aluminum gunwales should be fine, although there might be some corrosion of the aluminum gunwale that may or may not enlarge the hole slightly over time.

Even so, this shouldn't be a problem in gunwales as they are rarely submersed in seawater. Still, if you are forced to use stainless rivets and are paddling in a marine environment, it would be a good idea to rinse the gunwales with freshwater after a trip or before putting the boat into storage.

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native brookie
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 1:34 pm 
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Location: Central Maine--Sheepscot Watershed
Update:

Cannot find aluminum rivets in the size I need--3/16" rivet with a grip range of 11/16". I checked 3 local hardware stores and my Home Depot and only found rivets up to 1/2 inch long.

I finally located a "fastener" specialist called Fastenal. It turns out they actually supply Old Town with rivets. They can sell me stainless steel rivets, but at about a $.75 each, for a total cost of $40. Or they can sell me a box of 500 aluminum rivets for about $50. The bag of rivets that Old Town normally sells with a gunwale set sells for $14, including shipping. That's for 60 rivets.

I called Old Town back, and they are backordered and not available for "several weeks".

If anybody (or bodies) here has a use for about 420 aluminum rivets, let me know, and I'll buy the box of 500 and sell the remainder, cheap. Make me an offer. (Note: I can beat either Old Town or Fastenal on price for small lots!) :D

And please let me know if you know of a source who would sell me 70 or 80 aluminum rivets of the right size at a reasonable cost. (Perhaps some poor soul who only needed a few, and found they were only sold in lots of 500.)

Otherwise, I'll have to bite the bullet and buy the expensive stainless rivets so I can get my boat back in the water next week.

PS No worries, Splash Dancer. I enjoyed BK's research results, and now have an idea I plan to patent for recharging head lamp and GPS batteries on salt water canoe trips. I'd been working on a small water-driven turbine that ran off the boat's momentum, but this is even better.
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Battenkiller
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 2:02 pm 
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native brookie wrote:
Cannot find aluminum rivets in the size I need--3/16" rivet with a grip range of 11/16".



http://www.jamestowndistributors.com/us ... num+Rivets

Sold by the box of 100.

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“We can have great disparities of wealth or we can have democracy. But we cannot have both.” - Former Supreme Court Justice Louis Brandeis
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Canoeheadted
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 4:46 pm 
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Location: Burns Lake, BC
NB, go to an automotive supply store. They'll have aluminum ones for sure.
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woodenkayak guy
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 23rd, 2009, 5:42 pm 
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Joined: October 20th, 2006, 12:15 pm
Posts: 258
Location: calgary
"Cannot find aluminum rivets in the size I need--3/16" rivet with a grip range of 11/16". I checked 3 local hardware stores and my Home Depot and only found rivets up to 1/2 inch long."

canadian tire,pick a size thats close
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native brookie
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: September 24th, 2009, 7:55 am 
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Joined: April 11th, 2009, 9:43 am
Posts: 430
Location: Central Maine--Sheepscot Watershed
BK's tip paid off. Best on-the-phone customer service I have gotten in years. Overnight shipping for $5. Tonight's program at my house will be riveting.
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RAY1984
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: October 26th, 2009, 2:09 pm 
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Joined: August 5th, 2009, 8:34 am
Posts: 195
3/16 aluminium rivets are found at most automotovie body supply stores, or even snowmobile repair shops (their comonly used to fix hoods on sleds.) I sell them north of barrie if anyone is looking for them for around 20 cents each.
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tenboats1
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: October 31st, 2009, 2:01 pm 
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Joined: September 5th, 2006, 12:54 pm
Posts: 24
I think it has to be alloy not stainless because I reckon that the steel ones will have too high a breaking point and will lead to squashing the Rx.

That's what happened when I used steel rivets. I placed two, then had to drill them out and wait weeks to get alloy ones.

It maybe that there are different strenghts available, maybe I was unlucky with the steel ones. Anyway, I've done quite a few gunwale swaps now, and always use alloy rivets.

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erich
 Post subject: Re: Gunwale installation--stainless or aluminum rivets?
PostPosted: November 2nd, 2009, 2:30 am 
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If you were installing stainless gunnels, Monel would be the choice. However, since no one uses stainless gunnels, aluminum HAS to be the way to go. While there will be no problem with installing stainless rivets, one must also think of the potential for replacement. For canoe gunnels, aluminum is certainly strong enough. As well, drilling out an aluminum rivet is relatively easy. Drilling out a stainless one is more difficult and presents the issue of widening the hole. Monel is softer, but I would still choose aluminum.
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