# Watertight seal on thru-bolt deck hardware???



## SiXeVeN (Jul 7, 2007)

I have read enough info to make my eyes bleed. HELP!!

I need to bed all of my deck hardware after a complete rebuild. Ports, winches, cleats, padeyes, etc. They are all through bolted into the cabin. The deck is cored with Nomex. Before the rebuild about 50% of the bolts would leak!!! I don't want that again.

Here's the question. What should I use to seal the through bolts?

4200... Some say still too strong and won't be able to remove screws later.

Marine Silicone... Needs to be compressed. Poor adhesion so may pull away and leak.

Homedepot 'hybrid' poly-silicone for exterior windows... Apparently seals well and has some adhesive qualities. Worried it won't hold up to marine enviroment.

Any advice would be appreciated. Hands on knowledge of what had, and continues to, work well would be most helpful!!!


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## WinterRiver (Oct 20, 2006)

Butyl tape is spectacular stuff. Cheap, easy to work with, and perfect for bedding. Available at RV stores.

See Maine Sail's detailed instructions: Sealing Deck Penetrations  and Installing Ports


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## huguley3 (May 7, 2007)

I have been using butyl tape for pretty much everything. Nothing has leaked yet that was properly put together.

I put butyl on my windows and one of them we forgot to tighten down all the way. After about 2 months it started to leak and we tightened it down some more and the leaks stopped. If we had used something that cured it would mean taking the window off and cleaning the old off and applying new.

Don't get it on anything that your not willing to throw away though. It is sticky stuff.


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## SiXeVeN (Jul 7, 2007)

Where can you find butyl tape? I have been to several local places with no luck. A search on Defender's website was a negative.


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## DwayneSpeer (Oct 12, 2003)

*Butyl tape*

You get it at your local RV dealer or manufactured home dealer that also does repairs, etc. It comes in a roll of grey material. DON'T USE THE BLACK STUFF THAT AUTO DEALERS USE TO SEAL CAR WINDOWS! It's nasty stuff and you just can't get off of anything you use it on later.


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## RichH (Jul 10, 2000)

Leaks are more due to the 'geometry' of the hole than the material used to caulk. Be sure that there is enough clearance in the borehole so that there is sufficient room for caulk along the circumference of the throughbolts, there is a generous chamfer at the entrance to the hole, the parts/holes are CLEAN, and you dont tighten up the new caulk in one step --- just tighten to affect some 'squeeze-out' of the caulk then let set/cure a bit before fully tightening. Using that methodology you will have 'tighter' and less leak prone assemblies.


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## Maine Sail (Jan 6, 2003)

RichH said:


> just tighten to affect some 'squeeze-out' of the caulk then let set/cure a bit before fully tightening. Using that methodology you will have 'tighter' and less leak prone assemblies.


Rich,

With a proper bevel there really is no need for the more leak prone "Don Casey" method. There are too many risks associated with this type of tightening of the seal then there are benefits, IMHO, and in my practical experience.

Most folks can't tell when "cure a bit" occurs and many DIYers also twist the bolt shank after letting it cure way to much. Also if you let it cure to much, and actually create a gasket between the hardware and deck, you can induce room for movement from the flexibility of the gasket which in turn works the sealant until another leak happens.

I have used the bevel/tighten once method for over 23 years after learning it from a Hinckley employee and have used it many, many times even on submerged hardware that resides below the surface of the water. Not one leak but the bevel is key as well as a clean surface. Any GOOD sealant will work but there are pro's & cons to each.

This lifting point is now going on 9 years old and remains submerged when my RIB is in the water. I used 3M 101 and a countersink bit and tightened only once. Not one drop in 9 years while being submerged. If this method can work on submerged hardware useed to lift a dinghy and hold it in my davits it also works very, very well with "splash duty" hardware mounted to the deck..


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## RichH (Jul 10, 2000)

We agree that the chamfer/bevel is THE most important aspect; plus as you mentioned the possibility of the bolt etc. rotating after partial cure when torquing down can be a problem. That why I HOLD the head and tighten the nut ... and (almost) no problems in almost 40 years. For simplicity the once and done method may be best.


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## Maine Sail (Jan 6, 2003)

RichH said:


> We agree that the chamfer/bevel is THE most important aspect; plus as you mentioned the possibility of the bolt etc. rotating after partial cure when torquing down can be a problem. That why I HOLD the head and tighten the nut ... and (almost) no problems in almost 40 years. For simplicity the once and done method may be best.


Rich,

For someone like you or myself or other consummate DIY guys the two step will probably never leak as we are very careful not to spin the bolt and understand moisture cure sealants, skim vs. cure, vs. thicken but the average DIY will not put that much time into it and can really mess up a deck if done incorrectly. As you said the bevel is most important and once and done does remove most potential for error. The nice thing about butyl tape is that right off the spool it is already at the consistency you are trying to get a caulk tube sealant to with the "let it cure a bit" method so you can just bevel and tighten. Butyl is amazing stuff but admittedly is a little more tricky to work with and requires a little more common sense.

Surprisingly even today there are very few builders beveling. Bob Johnstone and his brother do it on J Boats and the Z line of MJM power boats and Hinckely was and Morris does and a few others. Amazingly Catalina and most other production boat builders still do not bevel (to costly?) and tighten only once (been to the factory and seen it first hand) and even more amazingly these seals can still last quite a while..


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## Valiente (Jun 16, 2006)

I use a combination of the grey butyl tape (I agree....it's still the best choice) and 4200. I epoxy the holes to insure isolation from the core, then drill through the "donut" and then bed with butyl and coat the "interior" threads with 4200. I also run a fine bead of 4200 along the perimeter of the backing plate...I don't use fender washers if I can avoid them.

I agree that you should keep the bolt still while dogging down the nut, and the time to dog down that nut is dependent on temperature and to a lesser extent, humidity.

I have had zero leaks in going on eight years now since I rebedded all deck gear and winches. The keel-stepped mast is another story, but that's pretty well inevitable due to water getting down the sheaves. It doesn't leak at the partners, anyway.


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## mitiempo (Sep 19, 2008)

I agree with Maine Sail. Overdrill or better yet don't overdrill and rout out core with a Dremel router bit on a flexdrive. Then fill with thickened epoxy before drilling correct size hole. Most often I drill smaller hole and tap for the fastener. I use butyl tape (grey) and bevel the hole. But I take issue with sealing the inside of the hole or backing plate. If the seal depends on the backing plate or sealed nut & washer belowdeck you've already failed in my opinion. If water were to get past the deck fitting you want to know about it quickly. If the backing plate or nut/washer is bedded the water has no place to go except into the core if it can find a way. Maine Sail didn't give a link to his excellent how-to site so I will - I haven't found a better way than this: Sealing Deck Penetrations to Prevent Core Rot Photo Gallery by Maine Sailing at pbase.com
Re-Bedding Hardware Photo Gallery by Maine Sailing at pbase.com
Brian


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## Maine Sail (Jan 6, 2003)

Valiente said:


> I use a combination of the grey butyl tape (I agree....it's still the best choice) and 4200. I epoxy the holes to insure isolation from the core, then drill through the "donut" and then bed with butyl and coat the "interior" threads with 4200. I also run a fine bead of 4200 along the perimeter of the backing plate...I don't use fender washers if I can avoid them.


It's not a really good idea to seal the inside or backing plate side even with a potted deck core. If your core is not sealed it becomes a very bad idea.

Most all of these bolts are stainless and if the deck side develops a leak but the backing plate side is sealed and not leaking; 1) you won't know you have a leak so that you can fix it. 2) The entrapped water around the bolt can eventually cause crevice corrosion and you will also not see it until it is too late and the bolt fails.

You really only want to seal the deck side. If the fitting leaks you want to know about it to avoid future problems..


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## huguley3 (May 7, 2007)

SiXeVeN said:


> Where can you find butyl tape? I have been to several local places with no luck. A search on Defender's website was a negative.


I got 2 rolls from The Original RV Wholesalers - RV Sales, RV Parts, Ohio RV Dealers RV Sales Florida RV Dealers. They don't sell the stuff I bought anymore but they sell something in a nice plastic case for quite a bit more. Also something called tacky tape that may be the same thing. But if you search for butyl on their site you will get a bunch of stuff.


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