Re: [Amel Yacht Owners] Re: re caulking of stanchion base

James Alton

Bill Kinney,

   I was originally thinking of using a non acid based silicone caulking for  bedding my stanchions but I think that you may have hit on the perfect solution using the Butyl tape to provide the required sealing. The caulking seal would have to rely on a good bond whereas the butyl should produce a good seal simply from compression and chamfering the top of the hole will increase the reliability of a compression seal.   While the butyl might not attach well to the fibreglass if some Tef-Gel is present, it will be well adhered to the inside of the stanchion base so should not try to crawl out.    You can also come back and gently tighten the bolts at a later time with Butyl which would destroy the bond and seal of a caulk.  The Butyl should reseal to the bolt in response the increased compression.  Finally, since these bolts really should be replaced and resealed as a part of a maintenance schedule the butyl is going to be easier to clean up.   I really really like your plan and will be packing some Butyl into my luggage!

   Do the holes tapped into the embedded steel bottom or pass completely through the steel?  I am thinking that if they pass thru that we can afford to be more generous with the Tef-gel since it will not be forced out of the hole to the surface.  If the holes bottom, your idea of using a bolt to apply the Tef Gel to the female threads sounds like an excellent way of applying the optimal amount of product.

   I also sometimes chamfer holes to provide a clean surface for caulking to bond to and I do think that it improves the seal.  I am sure that you will be careful to not cut away too much material but I have seen on a number of boats where the chamfering has extended pretty deep into fibreglass which can be a bad thing structurally since the shear strength is going to be reduced.  


Maramu #220 

On Aug 6, 2018, at 7:00 PM, greatketch@... [amelyachtowners] <amelyachtowners@...> wrote:


The bolts on Harmonie are Flat head machine screws, M8-1.25 x 30mm  I see no evidence that they had ever been removed since the boat was built in 1996.

We are very much on the same page with thinking about the issues/concerns in getting those bolts sealed back up.  If you read Joel's notes he does mention adding sealant under the stanchion base in addition to the tef-gel on the threads.  Done properly, that should keep the water away from the steel.

I think the combination is much better than just putting a dab of silicon on the screws as was done on my boat.

Here is my approach:
Each bolt hole will have a chamfer cut into the surface of the fiberglass with a countersink bit.

The bolts will have a thin coat of tef-gel added to the bottom couple of threads.  I might just put some down in the bolt hole to minimize contact with the upper threads--for all the reasons you expressed. Another alternative is to apply tef-gel to a screw, insert it all the way in the hole to smear the tef-gel on the female threads, then remove it and use a clean screw for final assembly.

The bottom of the stanchion base will have a layer of butyl sealing tape applied, with a little more wrapped around the bolt at the very top of the threads.

Butyl tape "flows" amazingly well.  Even if the threads of the bolts have a bit of tef-gel on them, I am confident that the butyl flowing into the chamfer I made at the top of the hole will be good enough to keep water out.

This basic technique has worked well for me in the past in similar situations. 

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA

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