Why on earth do I countersink or chamfer the deck aspect of the skins?
#1 This apply does rather a lot to stop gelcoat crazing. By feathering the sting of the gelcoat, boat hardware via the usage of countersink bit, you at the moment are a lot less likely to begin a crack or craze mark within the gelcoat. Gelcoat is an un-strengthened product. Due to this its prone to cracking. Sharp proper angle holes are a superb place for these cracks to start once you tighten the deck hardware and potentially flex the substrate. Beveling the edge of the opening or feathering it limits the flexibility of the crack to begin or start. If you cherished this article and you would like to obtain far more facts about boat hardware (from the Zenwriting blog) kindly go to our website. Because of this you typically see holes drilled into plate glass that may have beveled or rounded edges too.
#2 By making a bevel or countersunk recess in the surface of the deck the butyl tape has a cavity to fill. Without a bevel the hardware would compress the sealant to about 1/64th of an inch thick after the fasteners are tightened. Marine sealants do have some flexibility however not as a lot as you would guess. Follow me for a second; Let’s say you’ve got a marine sealant that has a ranking of 400% elongation earlier than break on a 1/64″ thick joint. Simple math shows you that 400% of 1/64″ is barely 1/16″ of whole allowable joint motion before a joint failure or leak starts. In the case of a stamped stainless steel stanchion base, 1/16″ is not much allowable motion earlier than failure.
#Three By countersinking across the bolt holes you improve the maximum thickness of the sealant, at the bevel, to roughly a 3/32″ depth at it’s deepest level. Using the same math as above 3/32″ X 400% offers you a complete joint motion before failure of 3/8″. If a mechanically fastened joint is shifting 3/8″ you could have extra problems than only a deck leak! So 1/16″ allowable movement earlier than failure at 400% without countersinking or 3/8″ allowable motion at 400% before failure with countersinking. Even a small bevel will drastically improve max allowable motion earlier than failure. Countersinking to a mere 1/16″ depth gives you 1/4″ whole motion across the bolt earlier than failure. You don’t want a deep bevel to make a big distinction between a failure and a seal. Four Countersinking is an excellent easy process. Has many many advantages. For instance, you may install the fitting and tighten it down now with no waiting and boat hardware you may seal deck hardware alone.
I am going to inject some robust opinion here so please move on to the subsequent photo if you don’t want to hear it.
I have a excessive degree of disdain the Don Casey «two step», «wait to tighten till cure and form a gasket» technique of bedding deck hardware. Believe it or not but I’m not a conspiracy theorist. I do however really feel as if Don Casey wrote that approach to ensure boatyards future revenue. (grin & wink)
This is To not say that it can’t work although. It certainly can. Does work.
«So what’s with the angst RC?»
The issue with the 2 step method & utilizing a marine sealant is that this;
Can the common DIY or yard worker get repeatable outcomes that are reliable and constant?
The answer to that’s fairly often a giant fats NO!
This isn’t about the concept of forming a layer of sealant between the fitting and deck being a nasty concept, but somewhat in regards to the EXECUTION, which will be very troublesome to perfect and get repeatable & dependable results, being the dangerous a part of the concept..
Give it some thought like this;
— If the sealant cures, to type a «gasket», and also you then transfer the bolt whereas tightening it down on the «second step»…. It may well break the seal and leak…
— When you create a gasket too thick, and then can’t get the mechanically fastened hardware tight sufficient in opposition to the deck, because of compression resistance in the new gasket, the hardware will move, and the sealant will finally fail and leak.
— If you don’t let the sealant kick/cure good, which is very troublesome, it could possibly all squeeze out and once more it can leak. Why is this so difficult with a sealant? Because mostly used marine sealants are temp and setting cured. Which means that humidity & temperature change the duration & rate of cure so it isn’t easily repeatable.
Honestly, I imply no disrespect to Mr. Casey, he writes glorious, excellent stuff and I am a huge fan. Unfortunately this method for bedding deck hardware is maybe a few of probably the most troublesome to execute advic to realize in the actual world.
I have witnessed far too many circumstances of core rot on account of each DIY & skilled «two step» bedding procedures than I might have favored to.
«But RC what makes it so onerous? The largest problem is that the majority marine sealants are moisture cured. You really haven’t any solution to know what state of cure they are in. The edges of a fitting may be at the correct state however the center of the fitting still wet & unchanged. Moisture cured sealants change states in a very unpredictable manner. With a high quality marine grade butyl it’s more of a «one step» procedure because the consistency of the product just isn’t changing states. All your doing it tightening slowly or over time to let it «displace» out from underneath the fitting to the purpose the place it stops oozing out.
So the place did I lean this countersinking methodology?
I realized this from a worker at Hinckley Yachts back in the 80’s.. Morris, Sabre and different fine quality builders have recognized this secret for years however a lot of the massive manufacturing builders are nonetheless both too low-cost, or simply don’t find out about it. This extra step takes all of about 30 seconds per stanchion however apparently it’s too much «extra» work for most builders.