[Public-List] Chainplates and caulking

Thu Sep 8 11:27:22 PDT 2016

Hi YAWL,

(sorry about that :-( )

One thing that has not been mentioned that I expect might be important 
is the side gap between the chainplate and the deck. One of the 
important aspects of any sealant is the strain it can sustain before 
tearing or debonding (ie primarily its elasticity).

A few years ago, I built my house in the Sierra, and for siding I used 
hardiplank. I had to butt the lengths, and I thought that I would have 
nice light joints that I caulked with a very stretchy caulk. The 
following summer (very dry), the planks had  shortened (due to drying, 
and I noticed that all the tight joints were open and all the caulked 
seams were split open. After a bit of cogitation, I realized that I 
should have had wide joints, allowing for a wider caulk filled slots:

Strain= Delta L/ Initial L (where L = length of the gap in this case)

So if the gap is really small (ie L is really small - say 0.01"), and 
the admissible strain is only 25% (pretty substantial for most caulks), 
then the gap can only open 0.0025" - a minuscule amount. So if the chain 
plate moves (due to temperatures, loads on the chainplate, or ???) more 
than a few thousandths of an inch, the caulk may fail (in this example). 
I know that in my boat the slots are very tight and it is hard to slide 
the chainplates out of their slots.

It may be more reasonable to use a larger gap around the chainplate and 
fill it full of your choice sealant, preferably one with a large strain 
to failure. Another advantage of such a large opening is that there 
should be very little possibility of the chainplate contacting the deck 
thereby introducing point loads where they don't belong.

This concept of strain may also be why chamfering holes and filling the 
chamfers with soft sealant works so well.

Any thoughts?

Anders

On 09/08/2016 07:21 AM, Jonathan Bresler via Public-List wrote:
> Dan,
>
> I had the same question....so its Google time.
> Found the following (
> http://www.oldhousejournal.com/the_short_course_on_caulk/magazine/1417):
>
>
> *Butyl.* Based on a man-made rubber, butyl is one of the oldest and most
> affordable caulk types. Butyl caulk is solvent-based and characteristically
> stringy, which makes it difficult to apply in a finish-quality joint, but
> its admirable adhesion and weather resistance continue to make it popular
> for sealing gutters, chimney flashings, walks, and other exterior joints.
>
> *Latex.* A general term for a rubber-based caulk that is applied as a
> liquid, latex caulks are usually water-based. Because basic latex caulks
> have the least ability to stretch (rated around 7% to 10% elasticity), they
> work best in interior applications where little movement is expected. These
> days, latex is often combined with another caulk type, such as acrylic, to
> enhance performance.
>
> *Acrylic.* In caulks, acrylics are a family of synthetic resins that are
> clear as well as water-soluble. Like latex caulks, acrylic caulks are easy
> to work with because they can be painted and cleaned up with water, making
> them good for touch-ups and for filling small gaps. *Elastomeric caulk, a
> generic term for high-performance acrylic caulk*, is designed for greater
> elasticity and is quickly becoming a favorite in a market that values ease
> and speed.
>
> Generally, acrylic and latex caulks have a life span of five to 10 years,
> depending on environmental exposure, such as temperature shifts,
> ultraviolet light, weather, and building movement. These caulks can usually
> be removed by simply pulling them up or by using a utility knife to cut
> them away. Acrylic latex hybrids might include more solids, such as butyl,
> to offer greater product strength and integrity.
>
> *Silicone.* Silicone caulk is formulated from silicone elastomers, or in
> simple terms, linear polymers of silicone oils that can be coaxed to
> cross-link in a couple of ways. For residential use, this means
> incorporating chemicals that induce the polymers to room temperature
> vulcanize or RTV. (This process releases acetic acid as a by-product,
> producing a vinegar scent.) Silicone is virtually non-porous so its big
> advantage is to make something watertight, and it's most often used in
> plumbing applications (shower and sink installations) and some glasswork.
> Silicone is extremely rubbery (50% elasticity) but does not stick as well
> as other caulking and in its pure form, can't be painted. There are now
> some hybrid silconized acrylics that offer greater elasticity and a
> paint-friendly surface; they may be worth a try in an indoor setting where
> flexibility is critical.
>
> *Polyurethane.* Polyurethane caulk, which is based on the reaction of a
> glycol with an isocyanate to form a compound, is preferred for outdoor
> applications, with high-quality products having an exterior life span of 10
> to 20 years, depending on exposure. Polyurethane products bond to most
> surfaces, including masonry and metal, hold up to heavy movement (25%
> elasticity), and can be painted. These traits also make these products
> great for filling indoor gaps in floorboards because polyurethane can take
> the high-traffic stresses of floors.
>
> The products are overkill for other indoor applications, however, because
> the material is much harder to control and takes longer to set up in
> situations where acrylic latex would be perfectly suitable. Polyurethane
> caulks have tremendous bonding ability-so much so, that they can also be
> used as adhesives in some circumstances-but this tenacity does make them
> more challenging to work with.
>
> Polyurethane is solvent-based, meaning that you must use paint thinner for
> cleanup. Early polyurethanes had to be mixed from two parts in the field
> like epoxy, but the new products come in one-part formula tubes ready to
> use. Due to their adhesive strength, removal usually involves cutting out
> or sanding off unwanted caulk.
>
> On Wed, Sep 7, 2016 at 6:16 PM, Rod via Public-List <
> public-list at lists.alberg30.org> wrote:
>
>> Dan;
>>
>> I have not heard of elastomeric caulk .
>> Do you have brand name I can watch for ?
>>
>>
>> Cheers,  Rod
>>
>> <div>-------- Original message --------</div><div>From: Daniel Sternglass
>> via Public-List <public-list at lists.alberg30.org>
>> </div><div>Date:07-09-2016  3:21 PM  (GMT-05:00) </div><div>To: Alberg-30
>> List <public-list at alberg30.org> </div><div>Subject: [Public-List]
>> Chainplates and caulking </div><div>
>> </div>Hello,
>>
>> For 30 years I have used elastomeric caulk around all seven chainplate
>> openings, with no water incursion. Admittedly all that time in fresh
>> water, but it has worked well. Easy to inspect, and just scrape it off
>> and start again if there is too much build-up.
>>
>> --Dan Sternglass
>> Watcher of the Skies, #201, 1966
>> Cayuga Lake, Ithaca, NY
>>
>> dans at stmktg.com
>> office: +1607-257-3431
>> mobile: +1607-592-8012
>>
>> Strategic Marketing Associates
>> 403 Highgate Road
>> Ithaca, NY 14850
>>
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