[Public-List] Main Sail Track Fastening
Roger L. Kingsland
r.kingsland at ksba.com
Tue Oct 20 13:08:14 PDT 2009
Thanks Don for your usual thoughtful remarks. I think I have an alternate
solution; I plan to order a stainless steel mast that I can polish weekly to
a high sheen visible for miles (boat name: "Sparkle Stick"). All the best,
Roger
-----Original Message-----
From: public-list-bounces at lists.alberg30.org
[mailto:public-list-bounces at lists.alberg30.org] On Behalf Of Don Campbell
Sent: Tuesday, October 20, 2009 2:14 PM
To: Alberg 30 Public List -- open to all
Subject: Re: [Public-List] Main Sail Track Fastening
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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