Preventing leaks from coach roof grab rails?

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steve yates

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I have butyl sealant on a roll with peel off backing tape, my question is where should I use it to prevent leaks through the roof?
Do I put a layer of it on the "feet" of the grab rail where I screw into from below, or do I wind some round the screwhead before I screw up through the coach roof into the the grab rail?
Thank you.
 
steve yates said:
Do I put a layer of it on the "feet" of the grab rail where I screw into from below, or do I wind some round the screwhead before I screw up through the coach roof into the the grab rail?
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I would say only the first.
If a leak develops, you don't want water to be trapped within the coach roof.
 
Your grab rails being leaky might be due to your use of screws from underneath to hold them down. This is not the strongest means of securing them. I would suggest that you should be using nuts and bolts with big washers. So sealant under the feet and under the head of the bolt!
 
The idea is to have a layer of it between the fitting and the surface to which it is to be attached. Some authorities advise countersinking the hole slightly so that there is more butyl in the area of the screw and that there will still be a seal, even in the event that the fitting gets screwed down so tightly that most of the butyl gets squeezed out (it never sets and always remains plastic).
It is a good idea to screw down the fitting temporarily and mask the deck around it to make the clean-up easier when you have applied the butyl and tightened the screws up to the required tightness.
Go onto the Sailrite YouTube channel and search "Atticus Update 51"
 
neil_s said:
Your grab rails being leaky might be due to your use of screws from underneath to hold them down. This is not the strongest means of securing them. I would suggest that you should be using nuts and bolts with big washers. So sealant under the feet and under the head of the bolt!
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I like the sound of that, but not sure how to do it. It's an 18ft boat, so rails are not large. Would I have to drill all the way through from the top of the rail to get a bolt all the way through to reach a nut?
 
steve yates said:
I like the sound of that, but not sure how to do it. It's an 18ft boat, so rails are not large. Would I have to drill all the way through from the top of the rail to get a bolt all the way through to reach a nut?
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Mine were originally only screwed from the inside. When replacing them, I went for A4 screw and bolt, M6. So they were first drilled right through, 6mm. Then the upper 15mm or so section of the hole was countersunk to take a large teak plug, from memory 15 or 16mm (the size needed for a M6 socket). The machine screw comes from inside, large washer under head. Nut sits under the plug.
 
BabaYaga said:
Mine were originally only screwed from the inside. When replacing them, I went for A4 screw and bolt, M6. So they were first drilled right through, 6mm. Then the upper 15mm or so section of the hole was countersunk to take a large teak plug, from memory 15 or 16mm (the size needed for a M6 socket). The machine screw comes from inside, large washer under head. Nut sits under the plug.
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This is how mine were fitted on my previous boat and I suspect is the best solution. An easier alternative, although not quite as good, is to use a hex head coach screw from underneath. You will probably need to open up the previous screw holes a little to prevent the wood from splitting. I used these to secure a tiller pilot bracket to the rudder and that takes a lot of stick.
 
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My handrails are now bolted in place using ss carriage bolts with square shank, m8 I seem to remember, with large washers and nylocs inside. Gives a smooth finish on the wood and can't easily be pulled out without breaking either the boat or wood. The rail was bedded down on butyl and I counter sunk the holes slightly to give a decent seal around the bolt as it goes through the deck.
 
steve yates said:
I like the sound of that, but not sure how to do it. It's an 18ft boat, so rails are not large. Would I have to drill all the way through from the top of the rail to get a bolt all the way through to reach a nut?
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Handrails are usually between 22-25mm wide and this allows enough space for an M6 machine screw with a 10mm countersink for a plug. Any narrower (or a larger fastening/plug) runs the risk of splitting. However many rails have tapered or rounded tops that narrow the space for the plug. I usually make my rails with almost square tops and chamfered edges so the plugs are well away from the edge.

In your situation, although you might be able to seal from the outside around the edges of the base, it is better to remove them and refix them properly. The screws from inside are OK but rather than bed in butyl fix them permanently with either thickened epoxy or an adhesive sealant like CT1 or Sika. Apply plenty of the adhesive, screw down until it squeezes out evenly, but not tight because you don't want to starve the joint, leave to cure then tighten the screws.
 
I was horrified to find my coachroof grabrails were fastened with long countersunk woodscrews driven up from underneath. The coachroof is 1/2" ply and the woodscrew heads were sunk below the surface and disguised with filler. A very weak arrangement.

I re-fastened them with 5mm s/s carriage bolts with the heads uppermost and sunk into counterbored holes in the grabrails that were later plugged with cross-grain pellets. Inside I used s/s penny washers and dome-head nuts.

I used CT1 sealant and placed a nylon washer over each bolt between the grabrail bases and the coachroof to maintain a minimum thickness of CT1.

The sides of the bolt holes in the grabrails and coachroof were coated with unthickened epoxy
 
Poignard said:
I was horrified to find my coachroof grabrails were fastened with long countersunk woodscrews driven up from underneath. The coachroof is 1/2" ply and the woodscrew heads were sunk below the surface and disguised with filler. A very weak arrangement.

I re-fastened them with 5mm s/s carriage bolts with the heads uppermost and sunk into counterbored holes in the grabrails that were later plugged with cross-grain pellets. Inside I used s/s penny washers and dome-head nuts.

I used CT1 sealant and placed a nylon washer over each bolt between the grabrail bases and the coachroof to maintain a minimum thickness of CT1.

The sides of the bolt holes in the grabrails and coachroof were coated with unthickened epoxy
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With a ply coachroof the best way of attaching them is to bond with epoxy as described in the West book. That is what I did but rather than through bolt I used No10 screws down into the ply with heads countersunk and plugged. Still firmly there after nearly 30 years. The older rails were attached as your original, but glued probably with Cascamite as used on the rest of the boat. They have been there for nearly 60 years. so perhaps not as weak as you suggest.
 
Tranona said:
With a ply coachroof the best way of attaching them is to bond with epoxy as described in the West book. That is what I did but rather than through bolt I used No10 screws down into the ply with heads countersunk and plugged. Still firmly there after nearly 30 years. The older rails were attached as your original, but glued probably with Cascamite as used on the rest of the boat. They have been there for nearly 60 years. so perhaps not as weak as you suggest.
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There's more than one way to skin a cat.

I am a great fan of epoxy but I avoid using it in situations where I might later wish to take something apart.
 
Poignard said:
There's more than one way to skin a cat.

I am a great fan of epoxy but I avoid using it in situations where I might later wish to take something apart.
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Why would you want to take grab rails off? - and the CT1 that you used is an adhesive anyway. I suppose my point really is that if you have a wood to wood joint through bolting seems unnecessary.

Different if you are attaching to GRP because of the difficulty in getting a good bond, although even then there are ways round this if, for example the deck has an inner lining making through bolting difficult you can cast threads in epoxy into the deck to take machine screws and then bond the item to the GRP. can be used for things like winches, turning blocks, organisers, as well as handrails. Pp 365-7 of the Gougeon Brothers book if you are interested.
 
Tranona said:
Why would you want to take grab rails off? - and the CT1 that you used is an adhesive anyway. I suppose my point really is that if you have a wood to wood joint through bolting seems unnecessary.

Different if you are attaching to GRP because of the difficulty in getting a good bond, although even then there are ways round this if, for example the deck has an inner lining making through bolting difficult you can cast threads in epoxy into the deck to take machine screws and then bond the item to the GRP. can be used for things like winches, turning blocks, organisers, as well as handrails. Pp 365-7 of the Gougeon Brothers book if you are interested.
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It is not a wood to wood joint .
 
Poignard said:
It is not a wood to wood joint .
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Guess your coachroof is sheathed, in which case abrade and still use epoxy - it bonds with GRP laminate in just the same way as wood. Not so good on gelcoat which is how most GRP decks are finished.
 
Tranona said:
Guess your coachroof is sheathed, [...]
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You are beginning to get the idea :rolleyes:

But, if it's all the same to you, I want to be able to remove my grabrails should I so wish and I am quite content with what I have done.

My only regret is that it does not meet with your approval.
 
Poignard said:
You are beginning to get the idea :rolleyes:

But, if it's all the same to you, I want to be able to remove my grabrails should I so wish and I am quite content with what I have done.

My only regret is that it does not meet with your approval.
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You don't need my approval - just pointing out the illogicality of using an adhesive sealant if you wish to remove it at a later date and if you did want the adhesive properties epoxy would perhaps be better. - and you did clearly state that the coachroof was ply no mention of any sheathing.

Am I right in thinking that your boat is many years old and the product of a high class builder? Did the handrails actually come off in your hand before you discovered the method of fastening? how many years had they been attached?
 
Tranona said:
You don't need my approval - just pointing out the illogicality of using an adhesive sealant if you wish to remove it at a later date and if you did want the adhesive properties epoxy would perhaps be better. - and you did clearly state that the coachroof was ply no mention of any sheathing.

Am I right in thinking that your boat is many years old and the product of a high class builder? Did the handrails actually come off in your hand before you discovered the method of fastening? how many years had they been attached?
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You are beginning to annoy me.

I know it's Sunday but if you want to preach may I suggest you go and find a church to do it in.
 
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