Let's revisit through hull installations

[KP44]

As others have said, 5200 is not suitable for through-hulls. Or much of anything else.

[Eastward ho 24]

I haven't considered the thickness of the thraded bronze you mean the adapters are a 1/16 as opposed to what on the mushroom

[Sailmonkey]

Originally Posted by Eastward ho 24

I haven't considered the thickness of the thraded bronze you mean the adapters are a 1/16 as opposed to what on the mushroom

I can’t think of a single point on the flanged adapters that are 1/16” thick.

The wall thickness on the skin fitting is near that, but that’s the case no matter if you use a nut, an adapter, or a tapered plug valve.

[Eastward ho 24]

They are 3/4 I have 3 of them

[Eastward ho 24]

Originally Posted by Scout 30

What are the sizes of the WC seacocks you're replacing. Do you want to sell them?

They are 3/4 I have three of then

[Eastward ho 24]

If not 5200 then what to use?

[hobopacket]

4200?

[rbk]

Having just completed all of mine, and having researched the topic thoroughly I came to the conclusion that the Groco flanged adaptors, thru hulls and ball valves were the way to go (or any other bronze variation). 5200 is the devil but if done properly you should never have to remove the thru hull and flanged adaptor ever again, period (hence the use of 5200). The weak link is the valve so why make the disposable part a fixed part of the system? I can now replace all my ball valves for a fraction of the cost and way less hassle. More specific to Grocco is the zerk fittings for in water greasing and winterising. If 5200 scares you, move down the scale, 4200, 4000 etc but if you ever take a grounding on a thru hull I'd want the strongest sh*t available holding that thru hull in. I debated about using through bolts for the adaptors, but in the end I did not install any...the reason being is the factory installs lasted 36 years without them or anything for that matter, so in the end I went with less holes in the hull, hit the flange up with 60 grit on the ROS and bedded in more 5200 on solid backing plates. Could have done the bolts through the backing plates but my existing solid GRP plates were apart of the hull and after taking the originals out (difficult to say the least) I felt and feel confident in my final decision.

[Eastward ho 24]

West system gflex? yes I've removed things that were bedded with 5200 basically rips the fiberglass out with it. But I've never removed it from metal. I'd sleep alot better in 1000 ft of water knowing that my through hull will need to rip my fiberglass out of the boat to come loose.

[mitiempo]

Originally Posted by Eastward ho 24

If not 5200 then what to use?

Sika Flex 291

The sealant used is to keep any water out. IT is not holding the through hull to the boat. The seacock of flanged adaptor will do that very effectively.

As far as the three through bolts used, you don't have to. Here is a link to an alternative method that doesn't require the extra 3 holes through the hull.
http://www.pbase.com/mainecruising/backing_blocks
The thread of the through hull (mushroom) into the seacock or flanged adaptor keeps everything together. The 3 bolts keep the flange from turning.

I will be replacing all my through hulls and valves next haulout. If I were to use bronze it definitely would be the Groco flanged adaptors using the alternate method linked to above.

Instead I will be using TruDesign which I have already purchased. Their valves are in my opinion better than the Forespar valves - stronger and better design. The same material is used for both.

[CarinaPDX]

I am also in the process of changing to the Groco flanges, from ball valves screwed onto the thru-hulls (thread mismatch and all). I have never had a problem with the current situation but realize that it is neither as strong nor as well sealed as a proper ball valve+flange install.

I used 5200 when the thru-hulls were originally installed, and slept very well at night, thank you. When I had a blister job done a decade ago it did create a modest problem, but how often is that done? The whole point is that the thru-hull never needs replacing in normal use (blister job notwithstanding).

I have hot-swapped a 3/4" valve in January in the river in Göteborg, Sweden - very cold and wet but also very quick - no need to dive on the outside. Just have the new valve open and ready to go, then close it once a few turns are done. If you have a strainer on the outside of the thru-hull then plugging it is not that easy. I have friends who have hot-swapped 1-1/2" valves on their boat in the Puget Sound; again, no diving necessary.

I am making my own backing plates of 1" G10/FR4 epoxy/glass sheet. The flange bolts will thread into three drilled and tapped holes in the plate, deep but not all the way through. The plan is to epoxy the backing plate to the hull, and possibly tab it all the way around. Then using Sikaflex the thru-hull and flange will be mounted more-or-less permanently. This is a bit of overkill as the internal flange and thru-hull mushroom are plenty strong enough to hold it all together. I like overkill...

Greg

[Eastward ho 24]

[QUOTE=CarinaPDX;2537188]I am also in the process of changing to the Groco flanges, from ball valves screwed onto the thru-hulls (thread mismatch and all). I have never had a problem with the current situation but realize that it is neither as strong nor as well sealed as a proper ball valve+flange install.

I used 5200 when the thru-hulls were originally installed, and slept very well at night, thank you. When I had a blister job done a decade ago it did create a modest problem, but how often is that done? The whole point is that the thru-hull never needs replacing in normal use (blister job notwithstanding).

I have hot-swapped a 3/4" valve in January in the river in Göteborg, Sweden - very cold and wet but also very quick - no need to dive on the outside. Just have the new valve open and ready to go, then close it once a few turns are done. If you have a strainer on the outside of the thru-hull then plugging it is not that easy. I have friends who have hot-swapped 1-1/2" valves on their boat in the Puget Sound; again, no diving necessary.

I am making my own backing plates of 1" G10/FR4 epoxy/glass sheet. The flange bolts will thread into three drilled and tapped holes in the plate, deep but not all the way through. The plan is to epoxy the backing plate to the hull, and possibly tab it all the way around. Then using Sikaflex the thru-hull and flange will be mounted more-or-less permanently. This is a bit of overkill as the internal flange and thru-hull mushroom are plenty strong enough to hold it all together. I like overkill...

Greg

Attachment 160577

Attachment 160578[/QUOTi


I'm thinking I'm going that route too. Why are you going with sikaflex rather then 5200 between The mushroom through hull if since the adapter and through hull will be permanent ly married together? And is your backing plate to take up the space on the mushroom threads or to spread the load, or both? I'm wondering how. Thick to make my backing plates... Also ha ha let's start making a taperd cone bronze valve to fit on the adapter and corner the market. For some reason I don't see anything that makes any argument against to do anything other then flange adapter screwed into the backing plate rather then through bolted. Maybe even take it a step further and use thickened epoxy instead of Sika or 5200. I don'ta reason I would want my through hulls " easily " removable. I want them permanent and if 60 yrs from now the mushroom head is corroded and needs fixed I won't mind haul out and a major job. Why would one want through hulls to be easily removed? From what I understand silicon bronze immersed in salt water will last a life time

[rbk]

Sika Flex 291

Same type of sealant as 5200 with slightly less tenacity somewhere between 4200 and 5200, all are polyurethane. If available I highly recommend the fast cure versions. Most take 7 days to cure, skimming over in ideal conditions in a day or so, a lot longer if not ideal. From what I found he fast cure is the same strength/adhesion as the regular stuff but you can cut excess and finish the exterior pretty much the next day and not the following month. Either way all can cure underwater if required.

[mitiempo]

Originally Posted by Eastward ho 24

I'm thinking I'm going that route too. Why are you going with sikaflex rather then 5200 between The mushroom through hull if since the adapter and through hull will be permanent ly married together? And is your backing plate to take up the space on the mushroom threads or to spread the load, or both? I'm wondering how. Thick to make my backing plates... Also ha ha let's start making a taperd cone bronze valve to fit on the adapter and corner the market. For some reason I don't see anything that makes any argument against to do anything other then flange adapter screwed into the backing plate rather then through bolted. Maybe even take it a step further and use thickened epoxy instead of Sika or 5200. I don'ta reason I would want my through hulls " easily " removable. I want them permanent and if 60 yrs from now the mushroom head is corroded and needs fixed I won't mind haul out and a major job. Why would one want through hulls to be easily removed? From what I understand silicon bronze immersed in salt water will last a life time

The backing plate is there to stiffen the area of attachment, spread the load, and provide a flat surface where there isn't one for flange attachment. It is not there to take up space on the mushroom threads. The mushroom should be cut to the correct length after careful measuring.

The adhesive properties of 5200 are not required. All the sealant does is keep water out. It has to adhere to the surfaces well enough so it handles any movement between the hull and mushroom - that's it. There should be no movement in a correct installation. This is more important for a deck fitting that can move such as a stanchion base.

Using thickened epoxy is not "taking things a step further", but a bad idea. Epoxy will not stick to the bronze through hull if there is any movement, it is not a sealant.

Sika Flex 291 is less adhesive than 4200 as far as I know.

[Eastward ho 24]

Now I'm gonna get rediculious .... Do they make ball valves with bronze balls? Or taperd cone valves to fit the adapter? I don't like plastic or disimilar metals ( the ball in the ball valves). The nice thing (in my mind) abouit the taperd cone is there's no nylon or what ever it is that creates the seal on the ball valve. And the cone is bronze to. I feel that the through hull screwed and permanently sealed into the backing plate which is epoxied into the hull with the through bolts screwed into that is pretty bullet proof. I'm thinking now the weak link is the actual ball and it's plastic gasket.