[Public-List] Main Sail Track Fastening
Don Campbell
dk.campbell at sympatico.ca
Tue Oct 20 11:14:21 PDT 2009
Roger:
I suggest that there are two concerns with that big an insertion
with pop rivets. The first is the concern for strength and rigidity
without actually knowing how much force is on the track. As a part of
this is the ability of the back of the rivet to really pull tight and
not allow for unwanted play there too. There is no prize for a system
that tightens the rivets up to the bottom of the T insert and then
allows the whole of the track to move on the stem of the insert and come
to a severe shock load when it hits the compressed end of the rivet. I
am always leery of things and complex systems I cannot see! The second
is that with these surfaces you never see, you are never really sure
that you have isolated the metals since any contact will mean the
isolation attempt is a failure.
Personally on fresh water boats, where I am here in Ontario, I don't
worry too much about galvanic or acid reactions.
If I were having to look for something for this isolation, I would
be hoping to find a thin film in liquid or gel form with a chemical
attraction that would coat the metals and isolate the metals from
reactions. It only needs to be several molecules thick. As a bonus, I
would hope it prevented or reduced any red-ox reactions by excluding
air. There are some materials that the electricians use on aluminum wire
for connections from the grid (usually aluminum wire for cost
considerations) to customers systems that involve a connection to a
dissimilar metal. That is where I would start. These guys play with
electrical current all the time and know the problems only too well when
the fire department is called to put out the fire from the short circuit!
Try to keep the systems simple if you are staying up nights to sort
them out, even though sorting out the meaning of life or the universe is
never apparently simple. (I suggest that Gord once had the meaning of
life sorted out when he said, had he been a keeper of a light, that he
would have had a lot of time to chase his Caroline around the island! If
you need more suggestions you might want to read a very short but
interesting book by John Tyler Bonner of Princeton University called The
Social Amoebae. He, too, was looking for an easy solution to life and
says so very plainly at the end of his 127 page book!) However, if
whatever the system you do design does not comply with Einstein's
theories, particularly m = E/c ² as he wrote it, and relativity, then
you can be assured that design won't work for applications, be they on
boats or your day job!
Don
Roger L. Kingsland wrote:
> Don,
>
> In the wee hours of the night as I lie awake contemplating "the meaning of
> life, the universe and everything else," I often wonder why hard neoprene T
> washers like these
> http://www.acousticalsurfaces.com/mounts_springs/neoprene_isolators_hg.htm?d
> =24 aren't used to isolate dissimilar metals. If used with a rivet I
> suppose it wouldn't be good for the "bulge end" of the rivet to seat against
> the T washer. Besides, RE the mast track application, it would be difficult
> to get the washers inside the mast. So aluminum rivets would be appropriate
> with the T washer isolating the flange end of the rivet from the SS mast
> track. It would be dependant on the neoprene being rigid enough to prevent
> movement at the connection and strong enough to resist crushing from the
> compression load created by the rivet fulfilling its destiny forevermore in
> tension.
>
> Roger 148
>
> -----Original Message-----
> From: public-list-bounces at lists.alberg30.org
> [mailto:public-list-bounces at lists.alberg30.org] On Behalf Of Don Campbell
> Sent: Monday, October 19, 2009 9:34 PM
> To: Alberg 30 Public List -- open to all
> Subject: Re: [Public-List] Main Sail Track Fasetening
>
> Mick:
> So far no one has mentioned galvanic action and if you are in the ocean
> with the boat, you might want to add that to the mix. Stainless will also
> disappear with what they call crevice corrosion as the alloy ingredients
> leak out with electrical current. There is no way without compromise, it is
> just where you decide to compromise. I would have thought that round head
> machine screws with Roberson heads would have fit the slot in the low part
> of the track.
> I do know that if you use something like a Garhauer vang on the existing
> track for the gooseneck, you can put enough pressure on the gooseneck to
> strip the threads on those bolts holding that track to the mast. And then
> you will be into using coil thread fillers there. I have found that any
> attempt at backing plates even as low as the gooseneck are a difficult thing
> to align, and if one uses anything but aluminum, you are back to the
> galvanic capacity again. Steel and aluminum is not a good mix and you can
> see the results of that if you look at older highway trailers used in
> Canadian winters, hence ones that get road salt on them, where steel bolts
> and aluminum frames are in close proximity.
> The aluminum goes very soft and flaky while the bolts get very rusty.
> Even the titanium coated ones will oxidize with the acid rain we have here
> in Ontario.
> My suggestion would be to use what has worked for the first 42 years and
> be prepared to replace those sooner the next time.
> Finding the force that is actually pulling on the sail track is not
> easy, but if you use the standard sizes for sails, those forces should not
> have changed much and if you use a reefed main or a Dragon main with a short
> foot, you will not stress the track beyond design. If you are worried, then
> doubling the number of sail clips will half the force at the sail clip and
> spread the force more evenly and closer to the fasteners.
> Don
> .
>
> Michael Taylor wrote:
>
>> After painting the mast I am putting the main sail track back onto the
>>
> mast. I see that some have tapped each of the existing holes to replace the
> rivets with machine screws. The track is stainless 7/8" with 3/16th holes
> drilled. The next drill size up will just clean out the existing mast holes
> and leave sufficient room to thread either 1/4 inch or 6mm machine screws.
>
>> Having got a sample of machine screws with various heads it seems that the
>>
> heads are too big for the existing sail track (they don't seat at the base
> of the track). I assume that the only way to use machine screws is to
> either change the sail track or drill new holes which I'm not prepared to
> do.
>
>> If I can't use machine screws it will be back to aluminum rivets with a
>>
> steel mandrel as I've found strainless very difficult to remove - and
> install.
>
>> Have I missed something with machine screw fitting here?
>>
>> thanks
>>
>> Mick
>>
>> #231
>>
>>
>>
>>
>>
>>
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