How mount chocks on caprail?

[malyea]

I need to mount a couple skene chocks and a couple straight chocks on my teak caprail to prevent docklines from abrading the caprail varnish (and the wood...).

IF I can align the chocks for a reasonable fair lead, will wood screws have enough holding power to secure the chocks (given that all my dock line loads are lateral and down - floating dock)?

FWIW - no way can I access under the caprail to thru-bolt....

Will I be happy with wood screws fastening my caprail mounted chocks?

Thanks!

[billknny]

Originally Posted by malyea

I need to mount a couple skene chocks and a couple straight chocks on my teak caprail to prevent docklines from abrading the caprail varnish (and the wood...).

IF I can align the chocks for a reasonable fair lead, will wood screws have enough holding power to secure the chocks (given that all my dock line loads are lateral and down - floating dock)?

FWIW - no way can I access under the caprail to thru-bolt....

Will I be happy with wood screws fastening my caprail mounted chocks?

Thanks!

The short, and unhappy, answer is: NO. Wood screws just won't cut it. The load on the chocks in a fore/aft direction are just as high as they would be on a caprail mounted cleat.

If you are talking a small, lightweight boat, always tied to a floating dock, maybe you could get away with it. But for a cruising boat? it will not be a good solution.

Sorry if that is not the answer you wanted to hear!

[malyea]

Originally Posted by billknny

The short, and unhappy, answer is: NO. Wood screws just won't cut it. The load on the chocks in a fore/aft direction are just as high as they would be on a caprail mounted cleat.

If you are talking a small, lightweight boat, always tied to a floating dock, maybe you could get away with it. But for a cruising boat? it will not be a good solution.

Sorry if that is not the answer you wanted to hear!

Yep, you’re right - not what I wanted to hear...

[Jim Cate]

An alternative is to fit s/s or bronze "half-round" strips along the cap rail, covering the whole area that the dock line might lie over whilst moored. Since there are no restraints to sliding back and forth, wood screws will easily suffice, and chafe to timber and line will be minimized.

Jim

[malyea]

Originally Posted by Jim Cate

An alternative is to fit s/s or bronze "half-round" strips along the cap rail, covering the whole area that the dock line might lie over whilst moored. Since there are no restraints to sliding back and forth, wood screws will easily suffice, and chafe to timber and line will be minimized.

Jim

Yep, I see rub strakes offered by various marine suppliers.

[techmans]

The fasteners holding those chocks in place are loaded in shear only at the interface of chock and cap rail.
Through bolted in this respect is no better than wood screws of equal strength and dimension.

So, if through-bolted would be acceptable, screws are equally so.

For what it's worth, on my 47 year old boat heavy chocks are screwed onto the cap rail and show as yet no sign of intention to depart.
But then this is a very heavy all teak boat which may not be comparable to a flimsier rail on FG boat. On the other hand the forces that have to be handled may be lighter.

My advice would be to go ahead; it will not sink the boat.

[Suijin]

Originally Posted by Jim Cate

An alternative is to fit s/s or bronze "half-round" strips along the cap rail, covering the whole area that the dock line might lie over whilst moored. Since there are no restraints to sliding back and forth, wood screws will easily suffice, and chafe to timber and line will be minimized.

Jim

+1

I have stainless rub strakes on my teak cap rail at the midships cleat. Work great.

Strakes come in two varieties; middle pieces and end pieces, allowing you to make a strake as long as you want with tapered ends.

[malyea]

Originally Posted by techmans

The fasteners holding those chocks in place are loaded in shear only at the interface of chock and cap rail.
Through bolted in this respect is no better than wood screws of equal strength and dimension.

So, if through-bolted would be acceptable, screws are equally so.

For what it's worth, on my 47 year old boat heavy chocks are screwed onto the cap rail and show as yet no sign of intention to depart.
But then this is a very heavy all teak boat which may not be comparable to a flimsier rail on FG boat. On the other hand the forces that have to be handled may be lighter.

My advice would be to go ahead; it will not sink the boat.

Interesting point. Another fellow with a 35 year old boat had basically the same response.

[Steve Bean]

I agree with techmans. The force acting on the chock will be less than that on a cleat. Is there enough thickness of the teak to allow letting the chock into the caprail? This would give more resistance to shear.

[seasick]

I too agree that vertical screws are less than ideal not so much for the shear loads but rather that they tend to be a path way for fresh water to intrude into your cap rail and rot it out.

[rhubstuff]

I know this will open a can of toredo worms, but I contend that the loads on a chock or cleat, properly and tightly fastened, are mostly opposed by friction between the base of the chock or cleat and the mounting surface, not by shear against the fastenings. To the point, I screwed bronze 4 inch chocks to the teak cap rails of our GB trawler and went through over one hundred locks and 50+ moorings using them. Then, after I sold her, the boat completed the Great Loop. To the OP, use the largest sized screws that will fit, drill the holes to that size with a properly tapered bit, caulk the base and screw holes with 5200, fasten tightly, and don't ever plan on removing them.

[malyea]

What to do...what to do...

All the marinas here in St Augustine have floating docks...when we’re cruiising we’re usually on the hook or a ball...We’re rarely (as in nearly never) tied to a fixed dock, in a big blow, with big tides...the logic of forces being lateral and down seems - logical...I can get a pretty damn fair lead from the mid ship cleat for the fore/aft spring lines...

I think that I’m pretty sure (given the insights and options I’ve received)... I think I’ll have another rum.