Deck mounted chainplates on a cal 20

[Adelie]

Originally Posted by tkeithlu

That's one hell of a good design for the load transfer to the hull, and overcomes the OMG problem I have with the idea that the builder used the deck/hull rivets to do the job. I had visions of the deck and hull parting company when you jibed. Spoil your whole day. Go for it!

If your hull/deck attachment is similar to the drawing - joined on the outside of the hull, then using external plates would be difficult. The design you've got achieves the same end - the plates are internal rather than external. It is a bit complicated. If you want to simplify it, consider fabricating a strap that does the job of the turnbuckle and the plate against the hull.

The designer was Bill Lapworth and my copy has lasted 54yr without ripping apart the deck & joint.

I recall that the Rule of thumb is that all the shrouds on one side have strength equal to the weight of the boat. For single spreader rig it’s a 60-lowers/40-uppers split. I’d have to check Vigor when I get home in 36hr.

It’s a 2000lb boat.

[cyrano138]

Originally Posted by Adelie

The designer was Bill Lapworth and my copy has lasted 54yr without ripping apart the deck & joint.

I recall that the Rule of thumb is that all the shrouds on one side have strength equal to the weight of the boat. For single spreader rig it’s a 60-lowers/40-uppers split. I’d have to check Vigor when I get home in 36hr.

It’s a 2000lb boat.

The boat plus gear, stores, and crew. That's how I got to the 5/32" size, using his chart in Seaworthy Offshore Sailboat.



I spoke with Steve Seals several times. Very helpful guy. For the record, unlike Vigor (who recommended it specifically for the Cal 20 in an article he wrote about it), he's against sizing up because of the added weight aloft.

[BBill]

Interesting design. Expensive but better in spreading loads. I like the bronze but knowing quality is everything. Silicon bronze is less brittle than regular cast bronze and more appropriate for this application so that might be the price difference.
I changed ss ubolts in the deck to external chainplates on a 20' x 2400lb brittish twin keeler. All I did was glass internal backing plates. Bought strap ss bar strap and cut it to size.

About the oversize rigging. Go for it. Its more about a safety margin than "required" strength that leaves less for wear or damage. There's great comfort knowing a strand or two can break and you have it covered when offshore. Do NOT tighten it at the same tension the way wire gauges do to tune rigs...they measure a section of wire to see how much play is in that sectin instead of wire pull. Otherwise you may damage something and it won't be the wire. It naturally has to be a little more slack feeling.

Also, don't overthink this and get hung up on what ifs. Do the math on what the actual added weight of 1/32 oversize wire adds and weight aloft is so small you probably won't be able to tell the difference. I oversized two boats (28' x 10k ketch and 32' x 12k sloop) and couldn't tell the difference.

[BBill]

[QOTE=Bowdrie;3751183]In many areas the term "mil-spec" has no special meaning.
The military buys millions of things/items from "normal" civilian manufacture and they assign a # to the item.
Not all that much different from a civilian ordering a specific part number from a wholesaler/manufacturer.[/QUOTE]

I worked 23+ yrs in the semiconductor mfg industry for a company that made mil spec parts (aka High Rel) for the USA military. Lots of "normal" vendors do mil spec but it isn't just a number added to a product. Mil Spec is basically about reliabilty, which ends up meaning the best engineering, best mfg, best quality control and best testing possible. Military Spec in the electronics industry means the product is as good as technology allows...and non mil spec parts are technically not equal. The parts that don't meet mil spec testing are normally used in high end domestic products. Mil Spec bolts totally eliminate the risk of buying cheap inferior parts. AN aircraft grade hardware is similar.

[thomm225]

Originally Posted by BBill

[QOTE=Bowdrie;3751183]In many areas the term "mil-spec" has no special meaning.
The military buys millions of things/items from "normal" civilian manufacture and they assign a # to the item.
Not all that much different from a civilian ordering a specific part number from a wholesaler/manufacturer.

I worked 23+ yrs in the semiconductor mfg industry for a company that made mil spec parts (aka High Rel) for the USA military. Lots of "normal" vendors do mil spec but it isn't just a number added to a product. Mil Spec is basically about reliabilty, which ends up meaning the best engineering, best mfg, best quality control and best testing possible. Military Spec in the electronics industry means the product is as good as technology allows...and non mil spec parts are technically not equal. The parts that don't meet mil spec testing are normally used in high end domestic products. Mil Spec bolts totally eliminate the risk of buying cheap inferior parts. AN aircraft grade hardware is similar.[/QUOTE]

All you have to do is see a few mil-spec parts as compared to normal vendor parts and you can quickly see the different especially with electronics.

Mil-spec plugs for example are so well made as compared to "normal" plugs there's no comparison.

Circuit cards after they are built then have conformal coating applied for even greater protection.
__________________________________________________ _______
What is MIL-I-46058C spec?
MIL-I-46058C, MILITARY SPECIFICATION: INSULATING COMPOUND, ELECTRICAL (FOR COATING PRINTED CIRCUIT ASSEMBLIES) (07 JUL 1972) [NO S/S DOCUMENT]., This specification covers conformal coatings which are suitable for application to printed circuit assemblies by dipping, brushing, spraying, or vacuum deposition.
__________________________________________________ __________

Those boards used to be a pain to work on back when we use to troubleshoot to the component level then have to change the component which would include capacitors, diodes, resistors, transistors, transformers, chips, diode bridges, etc.

The USA's military budget tells you a lot.

Even still the Mil-spec parts can be crazy expensive

[BBill]

how did my name get on that bogus quote? I was responding to it.

[Bowdrie]

We're not talking about the special "mil-spec" bolts for an F22 or a reactor in a sub, and it sure ain't rocket science.
And it's ludicrous and silly to be chasing down rabbit trails talking about sophisticated electronic components as having any relevance whatsoever.
It's just a d**n bolt to hold a bronze pad eye for rigging.
Scores of places all over the country have high quality/high grade US made fasteners of just about any material you want or need.
Looking at the Spartan part?
Ask Spartan about the bolts.
Ask them about the suitability of the product for the intended usage.
Not for one instant would I worry about the suitability and strength of anything Spartan makes when used for its intended purposes.
They are good people to deal with, I've been getting stuff from them for over 30 years.
A tempest in a teapot.

[thomm225]

Originally Posted by Bowdrie

We're not talking about the special "mil-spec" bolts for an F22 or a reactor in a sub, and it sure ain't rocket science.
And it's ludicrous and silly to be chasing down rabbit trails talking about sophisticated electronic components as having any relevance whatsoever.
It's just a d**n bolt to hold a bronze pad eye for rigging.
Scores of places all over the country have high quality/high grade US made fasteners of just about any material you want or need.
Looking at the Spartan part?
Ask Spartan about the bolts.
Ask them about the suitability of the product for the intended usage.
Not for one instant would I worry about the suitability and strength of anything Spartan makes when used for its intended purposes.
They are good people to deal with, I've been getting stuff from them for over 30 years.
A tempest in a teapot.

In my case, a friend knew a place to get the superior military grade bolts cheaper than the ordinary bolts I was going to buy at the local hardware store so I was like sure pick those up and I'll pay you back.

If others want to pay more for a lessor grade bolt that's fine.

Go that route.

[wyb2]

Originally Posted by BBill

how did my name get on that bogus quote? I was responding to it.

Because a ‘U’ got dropped from the syntax when you first quoted it

[QOTE=Bowdrie;3751183]yada yada yada [/QUOTE]

Vs

[QUOTE=Bowdrie;3751183 ]yada yada yada[/QUOTE]

Which shows up as:

Originally Posted by Bowdrie

yada yada yada

[BBill]

Originally Posted by Bowdrie

We're not talking about the special "mil-spec" bolts for an F22 or a reactor in a sub, and it sure ain't rocket science.
And it's ludicrous and silly to be chasing down rabbit trails talking about sophisticated electronic components as having any relevance whatsoever.
It's just a d**n bolt to hold a bronze pad eye for rigging.
Scores of places all over the country have high quality/high grade US made fasteners of just about any material you want or need.
Looking at the Spartan part?
Ask Spartan about the bolts.
Ask them about the suitability of the product for the intended usage.
Not for one instant would I worry about the suitability and strength of anything Spartan makes when used for its intended purposes.
They are good people to deal with, I've been getting stuff from them for over 30 years.
A tempest in a teapot.

You obviously don't understand what mil spec means. It isnt specific to electronics or any other industry or product. If someone wants the best repeatable reliabilty and quality they buy a mil spec product...nothing more, nothing less. You started digging the rabbit hole by posting that mil spec is just a number assigned to a product...which is absolutely incorrect and misleading.

[Bowdrie]

Originally Posted by BBill

You obviously don't understand what mil spec means. It isnt specific to electronics or any other industry or product. If someone wants the best repeatable reliabilty and quality they buy a mil spec product...nothing more, nothing less. You started digging the rabbit hole by posting that mil spec is just a number assigned to a product...which is absolutely incorrect and misleading.

I spent a fair amount of time working with "TAERS", The Army Equipment Records System.
Yes, there are "mil-spec" requirements for mess trays and wrenches too, (and even shoelaces,) and whether they or many other things labelled as such are always the "best" is open to debate.

[BBill]

Originally Posted by Bowdrie

I spent a fair amount of time working with "TAERS", The Army Equipment Records System.
Yes, there are "mil-spec" requirements for mess trays and wrenches too, and whether they or many other things labelled as such are always the "best" is open to debate.

Go study and learn what mil spec really means. Mil spec products have less defects than non mil spec products. That doesn"t mean the govt speced high end mess trays or tools but as quality goes they will have the least number of defects compared to non mil spec. Other than that it isn't just a number given to any common off the shelf product. It's not rocket science.