[Rhodes22-list] deck mounted chain plates

Sun Jan 11 10:08:41 EST 2015

Am I missing something here? Chainplates are designed to distribute loads
to the bulkheads and to the hull. The deck is flexible and in the case of
the R22, is pop-riveted to the hull and is not designed to take the loads
of the rig.

Those tangs on the R22 may look flimsy, but they are directing the load to
the right places.

Richard
S/V Waif

On Sun, Jan 11, 2015 at 9:32 AM, The Rhodes 22 Email List <
rhodes22-list at rhodes22.org> wrote:

> Graham,
>
> This article should give you the basics of calculating the load on the
> chainplates under sail at reasonable winds:
>
> http://www.sponbergyachtdesign.com/articlesengineering.htm
>
> The following forum posts deal with changing some of the basic dimensions
> of
> chainplate hardware and calculating the resulting changes in strength:
>
> http://www.boatdesign.net/forums/archive/t-3645.html
>
> The following article deals mostly with the process of replacement in an
> effort to avoid conditions that might lead to premature failure of properly
> sized hardware:
>
> http://www.cruisingworld.com/how/chainplates-101-inspect-and-refit
>
> I hope that this helps a bit.
>
> Mike
> s/v Wind Lass ('91)
> Nissequogue River, NY
>
>
>
> -----Original Message-----
> From: rhodes22-list-bounces at rhodes22.org
> [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of The Rhodes 22
> Email
> List
> Sent: Sunday, January 11, 2015 8:56 AM
> To: 'The Rhodes 22 Email List'
> Subject: Re: [Rhodes22-list] deck mounted chain plates
>
> Thanks Dennis. However, the question related to the maximum tension that
> the
> chainplates would need to withstand in use rather than the matter of tuning
> the rig. I just don't want to use deck mounted chainplates that are not
> sufficiently strong. That said, your reference to tension gauges will be
> helpful should my boat ever see water again.
>
> Graham Stewart
>
>
> -----Original Message-----
> From: rhodes22-list-bounces at rhodes22.org
> [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of The Rhodes 22
> Email
> List
> Sent: January-10-15 9:18 PM
> To: 'The Rhodes 22 Email List'
> Subject: Re: [Rhodes22-list] deck mounted chain plates
>
> Graham,
>
> The idea is to set the rig tension while the sails are down / furled. Take
> a
> look midway down the page at http://loosnaples.com/how-tos/tension-gauges
> to
> see Loos' suggested variation in shroud tension as the boat heels. I
> suspect
> something similar happens in the forestay / backstays.
>
> The picture shows that a rig that's too loose loses all support in the
> leeward shrouds, and notes that "The lateral stiffness of the mast and the
> fore and aft stiffness of the spreaders is reduced by a factor of 2 when
> the
> leeward shrouds go slack".
>
> Dennis
> Magic Moments
> Wondering if rig tension should be reduced in sub-zero temps.
>
>
> -----Original Message-----
> From: rhodes22-list-bounces at rhodes22.org
> [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of The Rhodes 22
> Email
> List
> Sent: Saturday, January 10, 2015 8:52 PM
> To: 'The Rhodes 22 Email List'
> Subject: Re: [Rhodes22-list] deck mounted chain plates
>
> Dennis:
>
> That is very helpful. Thanks. I would have believed you if you said the
> tension was thousands of pounds. Am I correct that the tension gauge would
> give the tension when the rig is at rest and that it might increase
> substantially in actual use - particularly when healing?
>
> Graham Stewart
>
>
> -----Original Message-----
> From: rhodes22-list-bounces at rhodes22.org
> [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of The Rhodes 22
> Email
> List
> Sent: January-10-15 8:42 PM
> To: 'The Rhodes 22 Email List'
> Subject: Re: [Rhodes22-list] deck mounted chain plates
>
> I know the use of Loos gauge data is against Rummy's religion, but...
>
> Take a look at http://loosnaples.com/how-to-use-pt-series-tension-gauges
> and
> you'll see the suggested tension for a 1 x 19 stainless steel 1/8" in
> diameter is 240 pounds. The Loos guide goes on to say "In some rigs it may
> be advantageous to carry a bit more tension in the uppers than the lowers".
> Sooo... figure 240 pounds in the lowers.
>
> Given that Loos suggests that a 1/8" forestay should carry 320 pounds of
> tension, and that my forestay is secured with a 3/16" pin, I'd guess is
> that
> your bracket should work for the lowers. Give some consideration to the
> size
> of the backing plate you'll use though.
>
> Dennis
> Magic Moments
> The glaciers have advanced back down the Detroit River. Aarrrg!
>
>
>
> -----Original Message-----
> From: rhodes22-list-bounces at rhodes22.org
> [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of The Rhodes 22
> Email
> List
> Sent: Saturday, January 10, 2015 7:04 PM
> To: 'The Rhodes 22 Email List'
> Subject: [Rhodes22-list] deck mounted chain plates
>
> During the rebuild of Agile I removed the chainplates for the lower shrouds
> with the intention of placing external chain plates on the cabin sides.
> Subsequently I changed the design doe the windows such that I now need to
> install deck mounted chainplates on the cabin top. Finding the right
> hardware has turned out to be a challenge. I found something that looks
> close to what I need but am unsure about its suitability - see attached.
> Given that the old chainplates were fairly thin tangs that were bent around
> the cabin deck core it would seem that this hardware is more than
> sufficient
> for the purpose but thought I would check the list to see if anyone has an
> opinion on these or  an alternative suggestion. Does anyone have a clue
> what
> load the lower stays place on the boat?
>
> Graham Stewart
>
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