Now here's a really bad idea

[CoastalEddie]

I ran across this page (Seacock Backing Plates / Alternate Method / No Through Bolts Photo Gallery by Compass Marine at pbase.com) the other day and realized that the method described is downright dangerous. Not only is it inherently much weaker than proper thru-bolting, but, more importantly, it gives the illusion of the job being properly done.

First, this method relies upon the adhesion between the inside surface of the hull and the new resin (acting as a "glue"), and the strength of a few millimeters of threaded fiberglass, rather than real honest thru-bolts. One doesn't have to be an engineer or naval architect to see the problem here. One sharp blow administered to the inboard end of the seacock is likely to pop the hull-resin junction apart (or rip the studs out of the backing plate), leaving only the thru-hull to hold the whole mess together.

But, more importantly (and insidiously), once a seacock has been installed via this method, there really isn't any way to tell that the job was not properly done w/o carefully inspecting the outside of the installation. Even then, a layer or two of bottom paint is bound to obscure the heads of thru-bolts, so unless one inspects the outside of the hull very carefully (and how many of us have seen surveyors who were FAR from careful in their inspections) this method will look like the Real McCoy.

I pointed this out in the comments section of Compass Marine's website and they simply deleted my post. I posted another comment, chiding them for the deletion, and they said "This is not a forum." I guess they really don't care about how dangerous their method actually is.

[mitiempo]

Eddie
The mushroom is threaded into the flanged adapter plate. The adapter plate is not able to spin. It also will never come off after being threaded into 5/8" (just shy of 16 millimeters) G10 or fiberglass pad which is then attached to a properly prepared surface with thickened epoxy. The epoxy will not come off the hull surface without ripping a piece of hull off with it. Looks fine to me. If only the manufacturer did as good a job.

[BubbleheadMd]

I'm inclined to agree w/MiTiempo.

I've been looking to replace my seacocks and thru-hulls and have examined several methods. The non-thrubolt method is only less secure by what I consider to be an inconsequential margin. Especially with today's modern epoxies. It's hardly "a few millimeters" of backing. The whole affair is quite thick.

On top of this, if you store unsecured, heavy gear or equipment next to a seacock where it can bang against it in a heavy sea, you deserve what you get in my opinion. In fact, the author of that article states that that's what happened to him: A spare, heavy alternator banged against the seacock, fracturing it and causing a leak. Although a seacock should be installed as securely as possible, it should never see more stress than what is generated by opening/closing the valve. It's not a load-bearing member.

Lastly, the author (who posts here), is just contributing his own solution to a common problem like we all do. He, like everyone else, isn't warrantying the procedure, or claiming that his is the only proper procedure. Heck, he even states openly that this procedure isn't quite as good as the thru-bolt method. We're all adults here, and it's up to us to analyze the freeinformation we receive here and decide if it's safe to use. If you don't like it, don't use it.

[Maine Sail]

Originally Posted by CoastalEddie

I ran across this page (Seacock Backing Plates / Alternate Method / No Through Bolts Photo Gallery by Compass Marine at pbase.com) the other day and realized that the method described is downright dangerous. Not only is it inherently much weaker than proper thru-bolting, but, more importantly, it gives the illusion of the job being properly done.

First, this method relies upon the adhesion between the inside surface of the hull and the new resin (acting as a "glue"), and the strength of a few millimeters of threaded fiberglass, rather than real honest thru-bolts. One doesn't have to be an engineer or naval architect to see the problem here. One sharp blow administered to the inboard end of the seacock is likely to pop the hull-resin junction apart (or rip the studs out of the backing plate), leaving only the thru-hull to hold the whole mess together.

But, more importantly (and insidiously), once a seacock has been installed via this method, there really isn't any way to tell that the job was not properly done w/o carefully inspecting the outside of the installation. Even then, a layer or two of bottom paint is bound to obscure the heads of thru-bolts, so unless one inspects the outside of the hull very carefully (and how many of us have seen surveyors who were FAR from careful in their inspections) this method will look like the Real McCoy.

I pointed this out in the comments section of Compass Marine's website and they simply deleted my post. I posted another comment, chiding them for the deletion, and they said "This is not a forum." I guess they really don't care about how dangerous their method actually is.

Edie,

I show this as a OPTIONAL type of installation and clearly state that this is LESS strong than proper through-bolting. This does not mean it is not strong though. This is for the boat owner who has a thin laminate or one whom is paranoid about through-bolting or adding extra holes to the hull.

Originally Posted by CoastalEddie

I pointed this out in the comments section of Compass Marine's website and they simply deleted my post. I posted another comment, chiding them for the deletion, and they said "This is not a forum." I guess they really don't care about how dangerous their method actually is.

Eddie, let's not play games here I said and asked more than just "this is not a forum". You've left out the part about me asking your for an email address, and then posting mine in the response, so we could discuss your points and "converse".

You refused to supply me with any contact information and even though I gave you my email address you still refused to write to me. (EDITED: as of 10:55 am EST you have still not responded to my email request) I do not allow ANY comments, pro or con on my site without email addresses, this is only fair to the readers so they know the comments are from real people/readers. Your comment was deleted because it lacked an email address.


Firstly though, before we go any further, I would like you to present some engineering data to back up your claims of "A really bad idea"....

For other Sailnet readers I have included below the quotes from Eddie, that were posted on my site, without an email address:

Originally Posted by CoastalEddie

Anchoring studs into your backing plate, rather than thru-bolting, isn't that great an idea.

It's also not that bad an idea and one that is multiples stronger than the millions of "valve on a thru-hull" installations out there. Manufacturers, including Groco & Forespar recommend simply screwing into wood, bedded with marine sealant! This installation meets or exceeds the ABYC standard.

I can assure you that a threaded 5/8" thick solid glass backing block has more strength than simple lag screws into wood backing plates. How do I know? Like anything, I tested it before posting the article..

Originally Posted by CoastalEddie

Seacocks are thru-bolted to assure that they are secured to the hull independent of the thru-hull fitting.

Yes many seacocks are through bolted to hulls but the vast majority, perhaps millions, of seacocks are simply a valve threaded directly to a thru-hull. Even a flange without any bolts is significantly stronger than just a valve on a thru-hull as any lever force is applied to both a flange to help distribute load, and the thru-hull fitting.

Forespar, who makes the Series 93 OEM seacocks, does not even accommodate a spot for through bolting. I can't even begin to count the number of builders including some very, very high quality ones, supplying boats with the Series 93 seacocks, suffice it to say there are lots. All of these valves, despite having no screws, tappings or through bolts pass the ABYC standard. I have yet to hear of one of them failing. Even builders such as Morris Yachts use the Series 93.

Perhaps you can cite for us some actual instances where a screwed only, flanged seacock failed because the thru-hull was the "only" thing holding it? I know there are many thousands of these out there, so if your assertions are correct, there must be a fair number of failures you can point to? Links would be good..

Originally Posted by CoastalEddie

Your method relies upon: a) the threads in a quarter-inch (or so) of fiberglass backing plate;

Let's examine this. First, the backing plates I suggest should be a minimum of 5/8" thick. I have had the engineering data run and a 5/16" bolt threaded into a 5/8" backing block exceeds the strength of a lag threaded into 5/8" marine ply or 3/4", which is a suggested installation by both Forespar and Groco that will meet ABYC standards even when bedded with marine sealant.

I might suggest that you email and educate Forespar, Groco and the ABYC about these inherent flaws. Any wood will peel and fail from the bond faster than solid fiberglass will. Peel up a backing block bedded with 5200 and you leave wood on the hull. Epoxy a solid glass backing block to a polyester hull and let us know how it comes off..?

Originally Posted by CoastalEddie

and b) the tensile strength of the bond between the new resin and the hull. Neither of these is a particularly secure way to affix a seacock.

Perhaps you can quote for us the tensile strength of both epoxy and polyester resin, as a secondary bond, per sq. inch? The backing plates are 5.75" in diameter with a 1 1/8" hole in the center. I know the bond strength of the plates as I have run the calculations. Ever install I have done has been done with epoxy. I only suggest polyester so someone does not smear a 1/2" gap of epoxy and have an exothermic melt down.

Originally Posted by CoastalEddie

Thru-bolting assures that a tangental force applied to the seacock will be transmitted to the hull, rather than the thru-hull fitting.

Perhaps you have not considered skin thickness of some of the newer boats or the fact that boats with cored hulls have skins to thin to properly countersink the head of a 5/16" machine screw into and leaving enough skin thickness for the fairing the bolt head.

Originally Posted by CoastalEddie

Your method may look neater, but I'm willing to bet that a good sharp force applied to the inside end of the seacock is likely to pop the backing plate off of the hull and/or pull the studs out of the threaded fiberglass.

Really? I guess that depends on what you define "sharp blow" as? Remember, Marelon PLASTIC through hulls can support a 500 pound static load applied for 30 seconds to the innermost hard fitting. Surely you are not saying 3M 4200 is as strong as epoxy, which is all that is holding many Series 93 valves on. Run the numbers on the epoxy and you'll see that the hull lamination would peel before the epoxy. Pretty basic stuff.

Originally Posted by CoastalEddie

This might not be noticeable at first, but it would leave the thru-hull as the ONLY thing keeping the seacock in place, and eventually lead to a leak around the thru-hull.

The thru-hull is the ONLY thing, other than some marine sealant, holding millions of seacocks into boats, and that is without a flange, or tapped 5/16" bolts into a 5/8" solid glass backing block, then epoxied to the hull with thousands of PSI adhesion. Leak really? I'll let you know when the fist one leaks..

[SVPrairieRose]

Check And Mate!

[tommays]

The through hull with a nut and a seacock stacked on top worked without issue for 40 years on my Cal

Yes i will be using Mainsails guide to inprove them as there old and do not neet the new stndard BUT my big issue is removeing them as there so dam strong

[imagine2frolic]

I guess I shouldn't take my boat away from the dock? The whole damned boat is glued together with epoxy... ........i2f

[gtod25]

advice in the past I would suggest you should have paused a moment before jumping in with both feet and stating "Now here's a really bad idea". Naturally you are free to ignore the advice or even propose your own solution. You state;

Originally Posted by CoastalEddie

One doesn't have to be an engineer or naval architect to see the problem here.

but it would be really nice if you were. As MS says how about some data, or is that passe in our brave new world.

I submit a video of one of my favorite comedians to lighten the mood, but take note of the comment at minute 1.

YouTube - Homeopathy & Nutritionists vs Real Science!

[MC1]

Interesting discussion as my thinking in general on this has been influenced by Nigel Calder and others making a strong case for the thru-bolted installations, but there's always room for other ideas if one can show objective evidence that they work as well or better. I guess we're dealing with a matter of degree here - what stength is obtained using the various approaches vs. what is actually needed in real world usage. If thru-bolting is stonger, perhaps it only matters in 1 in 1000 failure opportunities, thus we'll have strong anecdotal evidence that thru-bolting is not needed. On the other hand, those that are very risk averse may want the extra insurance. Am I thinking of this in a reasonable way?

Gtod25 - Great YouTube link, three thumbs up!

[SailorNate]

Im not a fan of thru bolts, I I like the alternative method you have shown, I had not thought of using studs rather than counter sunk bolts in case of damage (in hindsight an obvious question with a soft metal).

Another technique I like is it to try and locate my thru hulls in a locker that I can make watertight up to the water line (above actually). I may not be able to do it for each, but I do it where I can.