Fitting mid-ship cleats.

[Sneaky Pete]

I am going to fit a couple of mid-ship cleats what should I use to seal the joint between the aluminium and the glass fibre deck. I am going to use M8 csk screws is it enough to use standard M8 StSt washer or should I use something like a small StSt plate to support the load.

 

[MoodySabre]

I assume you are using bolts not screws. I would use a plate as there can be strong snatch loads.

 

[Sneaky Pete]

I assume you are using bolts not screws. I would use a plate as there can be strong snatch loads.

Yes M8 bolts with a slotted csk head. What kind of sealant.

 

[aquaplane]

The same sealant you use on your anode?

 

[Steve Clayton]

I assume you are using bolts not screws. I would use a plate as there can be strong snatch loads.

Have you considered toe-rail cleats? eg http://www.force4.co.uk/4587/YS-Toe-Rail-Cleat.html

and more here: http://www.ybw.com/forums/showthread.php?263757-toe-rail-cleats

I'm not going to comment on "snatch loads"

 

[grievesie]

I would suggest Sikaflex 291 - or similar polyurethane sealant. Definitely not silicone as that is not reliable where the fitting is under load. Assume you mean M8 machine screws - a stainless steel backing plate would be best idea.

 

[Sneaky Pete]

Being sneaky Pete I had a sneaking suspicion that someone would say that, going to try some PU40 from Tool station it has similar properties to Silcaflex 291 but not similar price, thanks all for the advice.

I did look at the other options but since there are mid-ship fairleads there I would like to incorporate them as the force on them acts in a different direction to the toe rail ones, the jenny car ones I feel are too close to the coach roof.

 

[VicS]

Yes M8 bolts with a slotted csk head. What kind of sealant.

as pointed out by Grievesie CSK machine screws are what you mean ! ( Bolts have hexagon heads and are only partly threaded. Set screws have hex heads and are fully threaded)

What ever sealant you use make sure that the screw is compelety sealed in the hole.. If there is any gap into which water can penetrate it is likely to cause crevice corrosion.
Sikaflex 291i would be a good choice . The non-marine equivalent is Sika 221. A copolymer such as CT1 also perhaps a good choice. I'd think PU40 would also be a good choice

Fit a substantial backing pad and either a plate or penny washers to spread the load

 

[pvb]

I'd also suggest that you use Duralac or similar to prevent corrosion between the machine screws and the aluminium cleat.
.

 

[Boathook]

I am going to fit a couple of mid-ship cleats what should I use to seal the joint between the aluminium and the glass fibre deck. I am going to use M8 csk screws is it enough to use standard M8 StSt washer or should I use something like a small StSt plate to support the load.

For the sealant arbo mast br, non setting, etc. This can also be used on the s/s bolts to protect them from the aluminium.

 

[Sneaky Pete]

I'd also suggest that you use Duralac or similar to prevent corrosion between the machine screws and the aluminium cleat.
.

Thanks I had'nt considered the reaction between these two metals

 

[David2452]

Also slightly countersink the screw holes, this allows the sealent to compress around the screws on the final "nip up" and makes sure no water tracks down them.

 

[VicS]

Thanks I had'nt considered the reaction between these two metals

Provided the "joint" between the screw and the cleat is filled fully with sealant so that water cannot penetrate between the two there will no problem. Fiddling about with two sealing compounds will not be necessary!

 

[pvb]

Being sneaky Pete I had a sneaking suspicion that someone would say that, going to try some PU40 from Tool station it has similar properties to Silcaflex 291 but not similar price, thanks all for the advice.

When I replaced a couple of my cleats, which mount directly on to teak, I cut thin nitrile rubber gaskets to fit under them, to avoid the mess of sealant squelching out on the teak. I put sealant around the actual bolts where they enter the deck, and used Duralac to insulate them (again, cleaner than sealant and easier to remove if needed).

 

[Poignard]

You don't say whether or not you have a cored deck. If you do, you must create a sort of epoxy sleeve between the two GRP skins otherwise the deck will be crushed when you tighten the fastenings. Even if your deck is solid GRP, I think it's still a good idea to seal the edges exposed by drilling with epoxy resin.

This describes how to do it better than I can:

http://www.soundingsonline.com/features/technical/286533-installing-hardware-on-cored-decks

 

[Sneaky Pete]

The cleats are countersunk so should get a good seal with the sealant and the countersunk screws, the deck is only GRP no core if I were to come in a bit away from the toe rail I come onto the coach roof and cored material. My main dilemma is if I go forward of the fairlead I am almost parallel with the shrouds if I go aft I am inside the navigation panel so I see the solution as fixing the cleats next to the fairleads.

 

[junkrig]

For mid-ship cleats you also need to consider chafe from the toe-rail, the cleats may need to be raised onto timber pads.

cheers

 

[Ex-SolentBoy]

Duralac is carp. Tefgel does a much better job.

 

[charles_reed]

Provided the "joint" between the screw and the cleat is filled fully with sealant so that water cannot penetrate between the two there will no problem. Fiddling about with two sealing compounds will not be necessary!

Stainless machine screws through an aluminium cleat?

Do you really mean that?

 

[Boo2]

Stainless machine screws through an aluminium cleat?

Do you really mean that?

What on earth else would you use ?

Boo2