Strength of Seacocks, Are Yours Strong Enough?

[jibes138]

Re: Load Testing A Seacock/Thru-Hull To Failure

To brace the right angle fitting all you need to do is measure the gap and then put a piece of PVC split pipe of the right thickness over the fitting to impede the motion if stepped on. The thru hull fitting will have some amount of elasticity so it will bend a little before breaking (elastic modulus can be found on a stress strain diagram for that material type) up to the yield point of the metal. Seems like a good cheap way to reduce or eliminate the risk.

 

[Maine Sail]

To brace the right angle fitting all you need to do is measure the gap and then put a piece of PVC split pipe of the right thickness over the fitting to impede the motion if stepped on. The thru hull fitting will have some amount of elasticity so it will bend a little before breaking (elastic modulus can be found on a stress strain diagram for that material type) up to the yield point of the metal. Seems like a good cheap way to reduce or eliminate the risk.

You pay for the thru-hull, I'll supply the PVC, and I'll still bet it fails before 500 pounds for 30 seconds...

 

[jibes138]

Re: Load Testing A Seacock/Thru-Hull To Failure

Hey,
I'm talking about your photo of the installation in the actual boat of a thru hull with a right angle fitting then a ball valve. If stepped on it will bend down to the floor and break. If you put a piece of plastic pipe around the fitting it will not bend down to the floor as much and won't break. Time should not be a factor in shock loading. Time is a big factor in a static load on a ductile material in excess of the yield strength as the material slowly deforms, work hardens, and eventually breaks. See my note about your batteries.

 

[Ralph Johnstone]

From What We've Seen in this Demonstration ..........

............... and in reference to ABYC H-27 27.6.1

27.6.1 A seacock shall be securely mounted so that the assembly will withstand a 500 pound (227 Kg) "static force applied for 30 seconds" to the inboard end of the assembly, without the assembly failing to stop the ingress of water.

we are dealing with a static load, not a shock load as you have described. Remember this is bronze, a brittle material, so very little plastic deformation, no work hardening, no warning, just SNAP.

 

[Maine Sail]

............... and in reference to ABYC H-27 27.6.1

27.6.1 A seacock shall be securely mounted so that the assembly will withstand a 500 pound (227 Kg) "static force applied for 30 seconds" to the inboard end of the assembly, without the assembly failing to stop the ingress of water.

we are dealing with a static load, not a shock load as you have described. Remember this is bronze, a brittle material, so very little plastic deformation, no work hardening, no warning, just SNAP.

The static load test is to ensure that human beings, gear, loose tankage, a scuba tank etc. could land on a seacock and it should hold. The idea is that this static test is above what the expected load whether shock or gradual may be on a thru-hull. All one can do is test to see if the available products out there meet the existing minimum standards, which I did..

The load I applied was done gradually, just as the industry does when testing to this standard. I consulted with both Groco and ABYC before doing it to make sure it was done as close to what they suggest/do as possible. It is very difficult to get to a "static load" of 500 pounds without shock loading the fitting if you don't apply it gradually. I cranked the winch gradually just as Groco does it.

This 500 pounds for 30 seconds is what the ABYC landed on as a test for seacocks meeting the minimum safety standard. Brian at ABYC is looking into the origins of it for me but it takes time to go through all the PTC data. All I know now, from the ABYC is that extensive testing was done to come to that test figure. I did not create the test and can't change it. The ABYC standard is also voluntary, so if you're comfortable with an in-line valve then keep it. According to ABYC builders building to NMMA standards are supposed be building their vessels to have 100% compliance in H-27, among other standards.

In speaking with Groco my findings are right in-line with their own in-house H-27 test findings. This is to say that in-line valves threaded to a thru-hull, in multiple sizes, do not meet ABYC H-27 standards. They were finding a 3/4" thru-hull failing in the mid to low 300's. I was an 1 3/8" below top hard piping and hit 404 pounds but this was with a Conbraco thru-hull not a Groco. Could have been less with a Groco but I have not yet tested one.

Groco tech support/engineering suggests using an in-line valve on a thru-hull only for above waterline use. They used to state this in their catalog but a big customer got "upset" so they removed the big red circle with the red line through it, placed over an in-line valve on a thru-hull.

It becomes frustrating to me to go to boat shows and see brand new boats built to NMMA standards, which includes compliance in ABYC H-27, with these installations. Many of these boats are being sold for 200k +/- with below waterline fittings that simply do not meet the minimum standards, when they are sold and labeled as NMMA / ABYC etc. etc...

And yes, the concern here is as you stated, "just SNAP " but I guess it could also be "Carpe Diem" when buying a new 6 figure vessel.......

 

[jibes138]

Re: Load Testing A Seacock/Thru-Hull To Failure

For this picture all I am suggesting is slit a piece of PVC pipe and wrap it around the mess so it won't bend down to the hull and break, basically a simple way to limit the motion. No question the installation is horrendous. But I have a similar installation for my raw water valve in my O'Day. Been meaning to put in a real seacock but never seem to get around to it. I'm really surprised that MaineSail didn't say a word about the lack of backing plates for these installations, or the very small diameter of them if they exist at all?? Maine did a nice piece on making laminated backing plates a while ago and these don't even llok like they have plywood under them. What's up with that MaineSail??

 

[Maine Sail]

For this picture all I am suggesting is slit a piece of PVC pipe and wrap it around the mess so it won't bend down to the hull and break, basically a simple way to limit the motion. No question the installation is horrendous. But I have a similar installation for my raw water valve in my O'Day. Been meaning to put in a real seacock but never seem to get around to it. I'm really surprised that MaineSail didn't say a word about the lack of backing plates for these installations, or the very small diameter of them if they exist at all?? Maine did a nice piece on making laminated backing plates a while ago and these don't even llok like they have plywood under them. What's up with that MaineSail??

What is there was un-coated plywood. This is in a area of the hull directly behind the trailing edge of the keel and on a boat this big the hull is probably 1/2" thick at that point, or more. May not even need a backing block though the backer in this type of installation acts to reduce the exposed height of the thru-hull threads.. A simple block of wood glued to the hull and wedged under the valve at the outboard end of the fitting would help too.. Another interesting thing is that the hose adapter closest to us appears to be yellow brass and the one in the distance a plastic..

 

[Maine Sail]

Just an update. I have edited the original post to add the latest testing which I will also add here....

I finally got around to testing a 3/4" Marelon valve on a 3/4" Marelon thru-hull with a 90 degree Marelon male adapter.

The load or pull point with the Marelon set up was applied at 4 1/4" off the bench. The load or pull point for the bronze set up was 4 3/4" off the bench. This was a 1/2" difference in FAVOR of Marelon yet it still failed at less than half the applied load.

I left the video unedited from start to finish.. Please ignore the commentary as that was not planned. I was however shocked at the low failure load and apparently could not help editorializing.....

Please remember that in order for a builder to put the ABYC or NMMA logo on a boat using this set up, as many do, the seacock needs to hold 500 pounds for 30 seconds at the inner most hard piping or the innermost portion of a male adapter.. These loads were applied well below what is often found on boats...

These are very typical installations and it is safe to say that as installed, valve on a thru-hull, in the 3/4" size, it does not even come close to meeting the MINIMUM ABYC safety standards....

 

[Kettlewell]

Very interesting! Thanks for the test results. It would be great to be able to build one's own boat in order to be able to better locate things like seacocks so they were inherently protected by their location in the first place, and also easy to access. Not easy to do, but I think with a bit of planning builders could do better. How often do you look at a new boat where some of the seacocks are nearly impossible to reach?

 

[Maine Sail]

Very interesting! Thanks for the test results. It would be great to be able to build one's own boat in order to be able to better locate things like seacocks so they were inherently protected by their location in the first place, and also easy to access. Not easy to do, but I think with a bit of planning builders could do better. How often do you look at a new boat where some of the seacocks are nearly impossible to reach?

It is actually part of ABYC & NMMA standards that they be easy to get to. I just spent a good deal of time at the New England boat show looking at installations, including access. There are many builders, both power & sail, who do not meet the "easy to access" definition and even more whose seacock installations do not meet the strength requirements..

Imagine a scuba tank sliding into one of these Marelon valve on a thru-hull installs...?

 

[Kettlewell]

I'll never forget reading about the sinking of Arthur Beiser's new boat (a Nicholson 70) on its maiden voyage. He was the author of the Proper Yacht, which was a bible "in the day" of how to build a great boat. Unfortunately, his European-built dream boat had something like 25 through hulls and apparently one of them let go or the hose broke or something because out of the blue the boat just started taking on water and despite the frantic efforts of the crew they couldn't locate the source of the incoming water and down she went. He later attributed it to too many through hulls in too many inaccessible places.

 

[Blitz]

It is actually part of ABYC & NMMA standards that they be easy to get to. I just spent a good deal of time at the New England boat show looking at installations, including access. There are many builders, both power & sail, who do not meet the "easy to access" definition and even more whose seacock installations do not meet the strength requirements..

How is this controlled if they don't meet the definition of easy access and still have the ABYC sticker on the side of their displays? Is a matter of self compliance for these manufacturers?

I seen the same thing with thru hulls and also with writing sizing at a recent boat show. I guess with the thru hulls if you can see it, it's easy access. Doesn't matter if there is no way to reach them.

 

[Maine Sail]

How is this controlled if they don't meet the definition of easy access and still have the ABYC sticker on the side of their displays? Is a matter of self compliance for these manufacturers?

I seen the same thing with thru hulls and also with writing sizing at a recent boat show. I guess with the thru hulls if you can see it, it's easy access. Doesn't matter if there is no way to reach them.

It is for the most part self policed though, as I understand it, the ABYC does do spot inspections as does the NMMA. If another manufacturer or anyone else reports it they could likely get audited and inspected. Much of the ABYC standards however are voluntary and only a few areas, like nav light installations, are federal law.

The strength is an "installed" strength and it is left up to the builders to do that testing to be sure it meets H-27. Clearly they don't or have not.

This is likely because they ABYC defines that a seacock CAN be a valve on a thru-hull. The builder likely "extrapolates", that because the ABYC says it is okay, and the parts are UL Marine, everything meets spec. It clearly does not in certain sizes!!!

Perhaps in a 1.5" valve/thru-hull it MAY meet the 500 pound test for 30 seconds but, in 3/4" we KNOW it does not, and in 3/4" in Marelon it does not even begin to come close. A Marelon valve/thru-hull in 3/4" fails at far less than half the specified load and did so at a shorter pull/lever point than the bronze..

3/4" is one of the most common thru-hull sizes.

 

[FastOlson]

It depends.....

It is actually part of ABYC & NMMA standards that they be easy to get to. I just spent a good deal of time at the New England boat show looking at installations, including access. There are many builders, both power & sail, who do not meet the "easy to access" definition and even more whose seacock installations do not meet the strength requirements..

Imagine a scuba tank sliding into one of these Marelon valve on a thru-hull installs...?

Evocative description, but overlooks the current "OEM" model of Marelon sea cocks that would fend off a veritable raft of hostile scuba tanks.
There's really no comparison with the original RC Marine valve production that Forespar bought up and then produced here.
Our boat has the later model Forespar sea cocks, installed about a decade ago. Ours are epoxied to the backing plates and would likely withstand an assault with a demented sledge hammer...


I agree that access is the other "forgotten" factor on all these thru hull installations. I once did a multi-day delivery down the west coast on a boat where the engine intake was only accessable by reaching down thru an access panel where you could not actually see the valve you were to turn! (Sigh)

LB

 

[FastOlson]

Very interesting! Thanks for the test results. It would be great to be able to build one's own boat in order to be able to better locate things like seacocks so they were inherently protected by their location in the first place, and also easy to access. Not easy to do, but I think with a bit of planning builders could do better. How often do you look at a new boat where some of the seacocks are nearly impossible to reach?

You are probably "preaching to the choir" here, but I can only add another Amen!!

 

[Kettlewell]

It really is amazing what builders will do. I owned a boat once where the only way to access the stern gland was by removing various things from the top of the engine so I could jam my body in prone between the top of the engine and the cockpit sole. The problem is that I would get wedged in there and had to be pulled out backwards by my feet. If I had been a few pounds heavier there would have been no access without removing the engine.

 

[Maine Sail]

Evocative description, but overlooks the current "OEM" model of Marelon sea cocks that would fend off a veritable raft of hostile scuba tanks.
There's really no comparison with the original RC Marine valve production that Forespar bought up and then produced here.
Our boat has the later model Forespar sea cocks, installed about a decade ago. Ours are epoxied to the backing plates and would likely withstand an assault with a demented sledge hammer...


I agree that access is the other "forgotten" factor on all these thru hull installations. I once did a multi-day delivery down the west coast on a boat where the engine intake was only accessable by reaching down thru an access panel where you could not actually see the valve you were to turn! (Sigh)

LB

The OEM models are very different valves but not widely available to the mass market because they use a very specific thru-hull fitting that is specific only to the OEM series. Forespar does not want end users picking the wrong thru-hull because the strength of that design relies on the use of the correct thru-hull fitting.

Both Catalina and Morris are two builders at opposite ends of the spectrum using the OEM valves and they are a very good product.

Not all builders do however and there are still examples of boats with Marelon valves slapped on thru-hulls plus the many thousands of existing boats, Ericson's and earlier Catalina's being but two brands, that have seacocks than could potentially fail at less than 200 pounds...

I do plan to test the tri-flange Marelon "seacock" too and will let you know how they fair compared to H-27 standards..

 

[Maine Sail]

I have uploaded a new video to add to this testing. Forespar sent me a 3/4" OEM Series 93 seacock and thru hull to load test. The valve passed with flying colors. These are the valves that come standard on the vast majority of boats today as factory installed seacocks.

Unfortunately Forespar has not made them easily available to end users as they use a completely different thru-hull fitting and threads. Suffice it to say that if you have these valves they are VERY, VERY robust!

 

[onecoolair]

I have uploaded a new video to add to this testing. Forespar sent me a 3/4" OEM Series 93 seacock and thru hull to load test. The valve passed with flying colors. These are the valves that come standard on the vast majority of boats today as factory installed seacocks.

Unfortunately Forespar has not made them easily available to end users as they use a completely different thru-hull fitting and threads. Suffice it to say that if you have these valves they are VERY, VERY robust!

<a href="http://www.youtube.com/watch?v=SLvLKnzop-0">YouTube Link</a>

Mainsail thanks for the information. This will come in handy as I prepare for my next haulout were I plan to replace all my thru hull fittings. Thanks Mon......Is this seacock made of a upvc or a cpvc type composite material ?
Now here is something to ponder. What if this test were done on hull section of say a h356? In fact I bet I all ready know what would happen. So what should one do when hull is much thinner then the hull test section you used for the test? How much larger should emergency plugs need to be that I would need too keep on board?

 

[Maine Sail]

Mainsail thanks for the information. This will come in handy as I prepare for my next haulout were I plan to replace all my thru hull fittings. Thanks Mon......Is this seacock made of a upvc or a cpvc type composite material ?
Now here is something to ponder. What if this test were done on hull section of say a h356? In fact I bet I all ready know what would happen. So what should one do when hull is much thinner then the hull test section you used for the test? How much larger should emergency plugs need to be that I would need too keep on board?

If you stick with "plastic" valves I would recommend the OEM 93 Series. Once you know your sizes any chandler that sells Forespar can order them. I've got some more testing to do so may just grab a white valve with red handle to see how it does....