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companionway ladder
Posted by: paul.silverman@umontana.edu (IP Logged)
Date: February 7, 2019 07:23PM
Category:

I'm working on various winter boat projects. One is to convert the companionway ladder to the hinged version that can be fixed to the inside cabin top. I'm cutting hand-holds to lighten it but it still is very heavy (constructed of 4/4 teak or mahogany). If you have one of these, how do you hook it to the cabin top in a secure way? If the damn thing fell, it could kill someone! Photos would be appreciated.

Re: companionway ladder
Posted by: Bil (IP Logged)
Date: February 8, 2019 02:33AM
Category:

Paul: Hi!

I've puzzled over how to answer your question. The hardware on Zygote's hinged ladder is just the sort of magic that Sam L. Morse Co. (meaning, in Z's case, the team of Dick McComb and Tommie Whisler, with input and executive function from Roger Olson) did and which I take for granted. I've looked through my photo file, and the few that show the companionway ladder do not show detail.

Let's start with a few advantages of the SLM Co. hinged ladder:

* it's removable when needed (the hinge pins are toggle pins aka drop-nose pins, and so can quickly be withdrawn) but also locked in place (see below);
* in the up position, it acts as a security device, impeding entry into the cabin by the ill-intentioned;
* in the up position, you have full access to the engine room etc.

To control the weight of the ladder (and for other advantages) the ladder on Z does not run full length to the cabin sole. Instead the ladder only runs to the top of a battery box. That box holds (in Z's case) two of Z's five Lifeline AGMs).

To get to the fixings:

* on the overhead, in just the right place, is a bronze eye strap. Held to the overhead by two bronze fasteners that I've not undone. I assume they are screws that bite firmly into the coachroof. I don't think they are through-bolts.

* on the outboard side of the starboard foot of the ladder is another bronze eye strap that

* captures a bronze swivel-eye boat snap for which I do not know a better technical name (so I'll instead point you to the West Marine page: [www.westmarine.com] Should you know the name for that particular boat snap, who designed it, and if it was patented, please tell me!)

* and a sliding bar latch (which I have also taken for granted and so for which I do not have a clear technical name) that locks the ladder to the top of the battery box (so that, should Z be unlucky enough to be inverted, the ladder stays locked in place).

Lifting and lowering the hinged ladder are practised moves after 19 years. Unlatch the ladder, lift it up, trigger open the boat snap, and let jaws of the boat snap close around the overhead eye strap. Reverse. Repeat.

Couldn't live without it.

HTH



BCC 116 Zygote,
Scarborough Marina, Moreton Bay, Queensland, Australia

Re: companionway ladder
Posted by: Bil (IP Logged)
Date: February 8, 2019 03:06AM
Category:

Bil Wrote:
-------------------------------------------------------

> * captures a bronze swivel-eye boat snap for which
> I do not know a better technical name (so I'll
> instead point you to the West Marine page: Should
> you know the name for that particular boat snap,
> who designed it, and if it was patented, please
> tell me!)

Downwind Marine sells a similar but different product, manufactured by Sea-Dog, called a trigger snap. See: [www.downwindmarine.com]

West Marine abbreviates the name of the manufacturer of its bronze swivel eye boat snap to SFHAR. Any clue as to the full name of that manufacturer?



BCC 116 Zygote,
Scarborough Marina, Moreton Bay, Queensland, Australia

Re: companionway ladder
Posted by: Bil (IP Logged)
Date: February 8, 2019 03:30AM
Category:


> * it's removable when needed (the hinge pins are
> toggle pins aka drop-nose pins, and so can quickly
> be withdrawn)


The hinges for the ladder are "hatch hinges with removable pins," as also used (at least on Zygote) for the skylight and the scuttle hatch.

See attached graphic (from the Sea-Dog) catalogue.

BCC 116 Zygote,
Scarborough Marina, Moreton Bay, Queensland, Australia

Attachments: Hatch hinge.JPG (90kB)  
Re: companionway ladder
Posted by: paul.silverman@umontana.edu (IP Logged)
Date: February 8, 2019 05:56AM
Category:

Thank you all! That was very helpful. I had been thinking of reproducing what looks like a brass or bronze rod hinge that runs through holes in the sides of the ladder and is attached to the the bulkhead by small bronze end caps. I hadn't thought of the disadvantage that the ladder cannot be easily removed from the hinge rod.Regarding screws for the eye strap, does anyone know what the actual thikness is for fiberglass cabin top?

Re: companionway ladder
Posted by: Bil (IP Logged)
Date: February 9, 2019 08:35AM
Category:

Paul:

I've never drilled or cut into the coachroof, so I don't know how thick it is.

Take a look at Roger Olson's 9-page BCC Construction Materials spreadsheet, part of which is reproduced as text in the BCC Construction Manual. The companionway ladder is mentioned on page 7 of the spreadsheet (about page 118 of the *.pdf, which of course you can download from the website).

That West Marine bronze boat snap shows up as Port Supply part #116103.

The hatch hinges that SLM Co used were bronze (not the stainless steel hinges from Sea-Dog). The bronze hinges look to have come from tehe now-defunct ABI (A & B Industries).

I'll have to look again at the overhead fitting on Z, to see if it fits the materials listed as "Ceiling Plate" from "Nimo Machine" (?there was - and even might still be - a Nimmo Machine in Costa Mesa fabricating metal parts for petrolheads). I'm not sure how we ought read the details for the "ceiling plate". Could it be that what I described as the eye strap on the overhead is held in place by two 3/4" slot head screws?

See the attachment (BCC Construction Manual - Materials Spreadsheet - companionway ladder.jpg, about 66 KB ) if you haven't yet downloaded and printed out a BCC Construction Manual for yourself. It's not essential, but better to have one and not need it than need one and not have it.

Edited to kill the emoticon!





Edited 1 times. Last edit at 02/09/19 08:38AM by Bil.

Attachments: BCC Construction Manual - Materials Spreadsheet - companionway ladder.jpg (66kB)  
Re: companionway ladder
Posted by: Bil (IP Logged)
Date: February 9, 2019 09:55AM
Category:

> I'll have to look again at the overhead fitting on
> Z, to see if it fits the materials listed as
> "Ceiling Plate" from "Nimo Machine" (?there was -
> and even might still be - a Nimmo Machine in Costa
> Mesa fabricating metal parts for petrolheads). I'm
> not sure how we ought read the details for the
> "ceiling plate". Could it be that what I described
> as the eye strap on the overhead is held in place
> by two 3/4" slot head screws?

I've discounted that idea.

For one, I don't think ex-USN Roger Olson would ever have uttered the non-nautical use of "ceiling" to mean the overhead.

So I reckon the ceiling plate is ?teak trim? and ?a reinforcing plate? on which the hatch hinges are mounted. A hinged ladder creates different forces compared to a stationary ladder, so the ceiling plate is I think likely to deal with the forces (some goodly proportion of the mass of the ladder).

BCC 116 Zygote,
Scarborough Marina, Moreton Bay, Queensland, Australia



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