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Old 09-12-2011, 16:20   #16
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Re: Seacock Question

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Originally Posted by shamrock View Post
Thanks everyone for the great info!

Cotemar, Can you tell me more about azek? this stuff solves the sealant issue with Starboard?

Thanks!

Seems to me it's filled PVC, which will sort of bond with epoxy. Why not precast FRP, tapered off on the edges and epoxied (thickened) to the hull? It will then be as permanent as the boat.
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Old 09-12-2011, 18:31   #17
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Re: Seacock Question

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Originally Posted by shamrock View Post
Thanks everyone for the great info!

Cotemar, Can you tell me more about azek? this stuff solves the sealant issue with Starboard?

Thanks!
Basically (its composite decking) the same stuff I used to build up a cap rail on a hull/deck joint. Epoxy sticks so well that one can not pull it apart w/o destroying the material. Although it is brittle in the since that if you drive a screw too close to the edge, it will crack like wood. Or if it's bent too much it'll brake, but not sliver.
It can take a hit with a hammer fairly well in relation to it's thickness and it dries out really quick. You do need a metal type jigsaw blade when cutting. It has recycled materials in it.
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Old 09-12-2011, 19:15   #18
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Re: Seacock Question

shamrock,
Yes, Azek solves the Starboard bonding problem.
Azek can be bonded just like PVC piping or use epoxy or silicone.
Cuts, drill, planes, sands and routers just like wood.
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Old 09-12-2011, 19:59   #19
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Re: Seacock Question

You might want to consider using a Groco Flanged Adapter and ball valve instead of a one piece seacock. It could make things easier in the future.
Groco Flanged Adapter IBVF
I visited a friends sign shop and asked about Azek board as they said on their website that it was used in the sign industry. He didn't have Azek board but he said there were a number of PVC board brands available. He gave me about a square foot of 1/2" to play with. When I get the chance I'll try some different goops on it and see what sticks.
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Old 09-12-2011, 20:27   #20
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Re: Seacock Question

Personal opinion, but I don't think Azek board (PVC) or King Starboard or Kingboard (HDPE) are suitable for through hull backing plates. I would prefer encapsulated marine plywood or better, I made my backings for through hulls from epoxy and phenolic spheres and fiberglass "short hair."

To quickly find out what something is made of - go to the MSDS harzard sheets. They have to list what the stuff is made of -
Azek material - http://www.azek.com/pics/reference_d...Trimboards.pdf

King Starboard/ King board - "High Density Polyethylene (HDPE) plastic"
Adhesives for King Starboard/ King Board - "Using Adhesive with King StarBoard King StarBoard®, King StarBoard® ST, King ColorCore®, King ColorBoard® and King CuttingBoard® can not be glued using standard adhesives. Products like 3M’s 5200 work well as a water sealing caulk but will not adhere King StarBoard® to itself or other materials in a permanent bond. It is preferable to mechanically fasten or weld King StarBoard®, but when an adhesive is necessary you can use a product called #7540-AB or 3M’s Scotch-Weld DP-8005. We do not represent these products, make any claims about their abilities or accept liability for them."

http://www.kingplastic.com/2011/06/using-adhesive-with-king-starboard-2/

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Old 09-12-2011, 20:31   #21
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Re: Seacock Question

The problem I found with wood, is if there is the slightest leak in the thruhull sealant the wood swells and/or delaminates. Which makes it leak even worse.
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Old 10-12-2011, 04:17   #22
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Re: Seacock Question

Anybody ever usen Mahogany board,I have a backing plate on my Thru hull for my paddle wheel made of Mahogany been there for 20 years no sign of failing.The other thru hulls were all backed with plywood all have detoriated and are being replaced,they were glassed over where the Mahogany wasn't.
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Old 10-12-2011, 06:35   #23
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Re: Seacock Question

I suspect with most organic woods keeping water away from them is the secret to long life. However that is a rather difficult endeavor on a boat especially an ocean voyaging boat.
- - Many techniques have been tried but I have seen the most success with marine plywood (plywood with waterproof glued layers) that has be soaked with thinned epoxy and then attached to the hull with layers of fiberglass cloth.
- - However, the mounting screws for the seacock need to be properly coated in adhesive sealant like 5200. And if ever those screws are removed the holes need to be properly sealed against water.
- - All of which adds up to a lot of work and time to do the job properly. Synthetics - (e.g., plastics) are normally imperious to deterioration by water but do naturally "dry" out and become brittle or just flat out crumble with age.
- - I wanted to use and did use Marelon flanged base seacocks and through hulls so I through-bolted the seacocks to the hull and built a temporary mold frame that kept the seacock about 1/2 inch off the inner surface of the hull. Then I made a putty of resin, phenolic spheres and fiberglass short hair and filled the mold. When it had finished curing I had an absolute flat fit for the seacock to the hull. In other words, I cast a backing pad to the flanged seacock. There is no stress at all to the through hull fittings that are then screwed in from the outside of the hull.
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Old 10-12-2011, 07:55   #24
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Re: Seacock Question

Another option to deal with this is creating epoxy plugs for the fasteners. Coat the plywood backing plate with epoxy and in place with epoxy. Now fit the thru-hull fitting and seacock or flange adapter and mark it's position and the holes for the fasteners. Remove the seacock again. Now you have the exact positions for the three fasteners. Use a 3/4" speed drill into those three positions, removing all plywood but stop when touching the fiberglass below of course. Fill these three holes with a syrup consistency epoxy mixed with micro fibers. Even before this cures you can put the fiberglass over it, doing all the finishing. Now, when you drill the holes for the fasteners you do not open the plywood to moisture.

cheers,
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Old 10-12-2011, 09:18   #25
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Re: Seacock Question

If your hull is FRP and more than 1/4" thick there is no need for a backup block at all. If thinner I would use a FRP backup plate. Polyurethane (5200) or Polysulfide (boatlife) make good sealants. Back up blocks were used in wood boats because a hole in a plank would weaken that plank. With FRP this is not a problem and in my experience backup blocks cause more problems than they solve. The only reason they are used is because it has always been done that way. You hace to use a Thru hull that is treaded all the way to the bottom but these are common today. Use Bronze UL approved for marine use only and a Flanged seacock, a ball valve on a thru hull is not a seacock it is a valve on a thru hull.
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Old 10-12-2011, 11:10   #26
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Re: Seacock Question

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If your hull is FRP and more than 1/4" thick there is no need for a backup block at all.
I agree, but with a cored hull, you often need to correct the different orientation of inner vs outer skins.

Here's my experiment bronze vs marelon seacocks; I selected this particular spot for not needing any extra work, other than replacing core with solid:

No backing plates and the fasteners only go into inner skin and core, not through the outer skin.

ciao!
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Old 10-12-2011, 11:16   #27
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Re: Seacock Question

Agreed cored hulls require different treatment. I would remove the core and inner skin in the area of the thru hull bevel the edges and add several layers of glass to reinforce. This way the core is completely isolated from and possibility of moisture. Once again no back up block needed. I am not clear about how you did this installation? Did you remove the core and how did you get the fasteners into the inner core only?
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Old 10-12-2011, 11:49   #28
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Re: Seacock Question

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Agreed cored hulls require different treatment. I would remove the core and inner skin in the area of the thru hull bevel the edges and add several layers of glass to reinforce. This way the core is completely isolated from and possibility of moisture. Once again no back up block needed. I am not clear about how you did this installation? Did you remove the core and how did you get the fasteners into the inner core only?
I remove the core from between the skins. This is practical for holes 3/4" or bigger. Dremel with drum sander followed by flapper sander works well for my 1" thick balsa core. There is always resin in between the balsa blocks to deal with of course.

When core is removed for 1/2" or more, vacuum it to remove all dust and fill with thick epoxy + colloidal silica mixture. To get the epoxy in between the skins requires practice; there should be no voids. The best tool is the black plastic spatulas from West System. After cure it needs the hole saw again.

The inner skin here is 1/4" thick, so I tapped it for the fastener. If the inner skin is too thin for that, I replace the core with epoxy before tapping. In that case I cast epoxy after removing a little more core than the diameter of hole in inner skin (bent nail in drill) This means the plug after cure is bigger than that hole. After that it's tapping for the fastener again.

I have one seacock in a position where it is remotely possible than one can step on it. I have through-bolted it but must say I don't like it. Next haul out I need to remove the bolts and replace sealant but I probably close the holes and tap again.

ciao!
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Old 10-12-2011, 13:56   #29
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Re: Seacock Question

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I remove the core from between the skins. This is practical for holes 3/4" or bigger. Dremel with drum sander followed by flapper sander works well for my 1" thick balsa core. There is always resin in between the balsa blocks to deal with of course.
Nick,

This is how Morris Yachts does it from the factory. They completely isolate the seacocks from the core..
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Old 10-12-2011, 14:08   #30
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Quote:
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This is how Morris Yachts does it from the factory. They completely isolate the seacocks from the core..
Yes, that looks very good... I assume they must still drill the holes for the fasteners? Also, what is the material used within that square?

The single seacock that was fitted from the factory on Jedi (= TPI Newport) was in a section of solid fiberglass. The hull has many parts where the balsa core is tapered away to solid glass, like around the keel, chainplates, deck-hull joint etc. The thru hulls in the photo above are additional ones, so I had to deal with the core.

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