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Thru deck sealing.


jkeenan

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Looking for some guidance here.

Getting to the point of installing all of the non wood stuff.

Motor, plumbing, lights, radio, horn, bilge pumps, etc, etc. You get the idea.

So today while noodling where everything will be permanently mounted, it dawned

on me that I will have several items that require thru the cabin roof sealing.

What is the consensus?

Gland fittings, Butyl tape, 3M 5200 or 4000 or some other solution.

Looking forward to the discussion.

Thanks

Jim

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How about Dolfinite Bedding Compound.  I like to see en opinion on that.  

Some of the choices will depend on if the item can be easily removed for repair or whatever reason.  I will have wiring for navigation lights, horns, antennas, solar panels that have to go to the roof and also a couple of water lines for a hot water solar panel.  I plan on making a hollow base for a mast on the roof and route most of the wiring through a pvc pipe sticking up through the roof that will be covered by the mast base.

 

Egbert

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I prefer having as much of the through cabintop paths figured out ahead of time so the interior can be blocked with solid wood.  Then it is not hard to waterproof the hole with epoxy or your favorite gunk.  I like electrical paths through PVC extending past the top like Egbert suggests and mine have an elbow on the top turned aft and stuffed with foam around the wires.  The main thing with any sealing of fitting screws/bolts is that there should be chamfer at the entry so that a doughnut of flexible caulk can handle any flexing or loosening of the fastenings.  Way too many people try to seal with good caulk and then over tighten the fittings.  This squeezes out the sealant into a thin film which cannot withstand any flexing or loosening at all and therefore leaks. 

 

The answer depends a lot on what the fitting is used for.  If there will be no stress on it, a fairly thick caulk and not over tightened will usually suffice.  If there will be stress, as with stanchions, it is important to allow for some movement and the chamfer and doughnut of caulk around the hole will be best.  Belt and suspenders method will have an oversize hole, filled with epoxy and re-drilled for fastenings. 

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When tightening a fitting with caulk a practice to add a bead of caulk and only very slightly tighten the fitting.  Tighten the fitting all the way when the caulk has set up.  This prevents the caulk from squeezing out. 

 

Egbert

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When tightening a fitting with caulk a practice to add a bead of caulk and only very slightly tighten the fitting.  Tighten the fitting all the way when the caulk has set up.  This prevents the caulk from squeezing out.

 

It also breaks the bond between the goo and the fastener which can yield a leak too.  Chamfering the hole as Tom suggests above gives you the gasket and the bond to the fasteners.

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Thank you all,

Tom the blocking is in place and appropiate. The tip on chamfering the holes is pricless. I spoke with a senior RV tech and he suggested Butyl tape and Dicor. Seems (no pun) to work great on RV's exposed to very much the same conditions as a boat.

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  • 5 months later...

For flat cables, such as Ancor #6, make two measurements. The thickness and the width. Drill two holes, whose outside circumferences are slightly larger than the cable sheath width, and whose diameter is slightly larger than the thickness of the cable sheath. Make a razor cut through the rubber seal that passes from the outside, through one hole and into the second hole. With the razor, trim the two triangles of rubber that separate the two holes (open up the rubber seal and lay it out flat to facilitate the trimming). Now assemble the Cable Clam with the flat cable and you have a water-tight seal. The picture shows two separate cables, but the principle is the same.

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Epoxy bonding is the wise choice if it's on the weather decks or hull, particularly if the item is "loaded". The chamfered entry as Tom describes it, works well and is an old trick. In fact, I like to do the same thing on epoxy bond holes, using a countersink bit on both sides (of the hole), so the epoxy makes a tapered flange area, under the fastener, hardware base or a washer. I have no idea what Ballard is trying to describe.

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