Would anyone be willing to help me interpret chainplate plans?

[Matt Johnson]

What does it mean by 50% of roving over fasteners on the outside? Are you embedding half the machine screws? Does it show additional lamination schedule in a different set of plans?

[Chotu]

Originally Posted by Matt Johnson

What does it mean by 50% of roving over fasteners on the outside? Are you embedding half the machine screws? Does it show additional lamination schedule in a different set of plans?

My interpretation is that means you put half of the biaxial down, then you drill out the tapered holes for the machine screw heads, and then you glass over those machine screw heads with the other half of the biaxial.

Some of the stuff that I redacted shows how much biax to put down. I didn’t want to put his design online. That would have not been right. Didn’t want to give up any intellectual property that he owns.

I am envious of whatever documentation you have. This is pretty typical from my designer. He’s like, here’s something cool. But I’m not going to tell you how to make it.

My biggest complaint about the plans was that it showed the bulkheads 6 inches off in one part of the plans from the other part.

[fourlyons]

This is what I see in the plans;

The chain plate is made up of two pieces; one is half inch thick, the other quarter inch thick. They're bolted together with four half inch bolts, maybe they're welded also, but that's not in the plans that we can see here.

The larger quarter inch thick section of the chain plate is bolted to the hull with 18 half inch bolts whose heads are embedded in the woven roving.

There is no backing plate. The large bog studs are carrying a lot of the load, in shear.

Where the chain plate goes through the deck, there is a reinforcement plate there. The deck is resisting the compressive forces of the chain plates pulling inward and there is extra woven roving at the turn of the deck to help with that.

It looks quite stout to me. Though I'm not so sure I like all of that buried stainless in a place where water might be able to migrate down into it. But that's beside the point.

[fourlyons]

Originally Posted by fourlyons

This is what I see in the plans;

The chain plate is made up of two pieces; one is half inch thick, the other quarter inch thick. They're bolted together with four half inch bolts, maybe they're welded also, but that's not in the plans that we can see here.

The larger quarter inch thick section of the chain plate is bolted to the hull with 18 half inch bolts whose heads are embedded in the woven roving.

There is no backing plate. The large bog studs are carrying a lot of the load, in shear.

Where the chain plate goes through the deck, there is a reinforcement plate there. The deck is resisting the compressive forces of the chain plates pulling inward and there is extra woven roving at the turn of the deck to help with that.

It looks quite stout to me. Though I'm not so sure I like all of that buried stainless in a place where water might be able to migrate down into it. But that's beside the point.

Correction - the larger plan of the chain plate shows 20 half inch bolts holding the quarter inch plate to the hull. That's a little disturbing, the two different views of the chain plate don't quite agree.

[Chotu]

Originally Posted by fourlyons

This is what I see in the plans;

The chain plate is made up of two pieces; one is half inch thick, the other quarter inch thick. They're bolted together with four half inch bolts, maybe they're welded also, but that's not in the plans that we can see here.

The larger quarter inch thick section of the chain plate is bolted to the hull with 18 half inch bolts whose heads are embedded in the woven roving.

There is no backing plate. The large bog studs are carrying a lot of the load, in shear.

Where the chain plate goes through the deck, there is a reinforcement plate there. The deck is resisting the compressive forces of the chain plates pulling inward and there is extra woven roving at the turn of the deck to help with that.

It looks quite stout to me. Though I'm not so sure I like all of that buried stainless in a place where water might be able to migrate down into it. But that's beside the point.

Thank you for posting. That’s a really good analysis. The part with no backing plate is what got me so confused. I kept thinking the “support plate” was indeed the backing plate.

Different numbers of holes. Wow. I didn’t look that closely. Just like how the bulkheads were in different places in different pages of the plans. The guy actually designs a good boat, but what a scatterbrain. Worse than me. Ha ha

[MicHughV]

If the upper tang is to be bolted to the chainplate....the bolt heads would prevent the chain plate from laying flush with the hull, unless those bolts also go clear thru' the hull ??
Most likely.
The tang does all the heavy lifting and the chainplate distributes the load to the hull. That seems to be the idea.

The holes around the perimeter of the chainplate appear to be holes for the bolts, as well as the center row, which also connect the tang.
But I see where the confusion might be. The first pic shows 5 holes in the center, with an extra hole near the top ( 6 holes). The other pic shows 4 holes in the center with 4 under the tang....just a wild guess....but maybe the upper tang does not align with the center of the chainplate, depending on it's location on the hull, as it should orientate in line with the shroud, so only one hole is show in the first pic. Depending on the final alignment the other holes are then drilled, which could explain the next pic, and bring you back to the 8 holes shown.
Off course it could all be centered and the final assembly rotated to align with the shroud.
I tend to agree with fourlyons, that the tang is bolted (thru'bolted), not welded...
The bog studs ???...Not sure about these. They seem to be spaced very close together.

Get a six-pack, go make friends with the NA and sort it all out.

[MicHughV]

Come to think of it....a few more six-packs distributed to CF members might be in order here.
Make mine Heineken

[rslifkin]

Is there any information on how much load these chainplates are supposed to be able to handle?

[MicHughV]

come to think of it, the bog studs have a wide upper flange, so they fit inside those large holes...the actual penetration of the stud is smaller...hmmm....could be...better make that 2 six packs....for me...and two more for fourlyons...

[MicHughV]

well, you have to think of it in this way.....the turnbuckle pin that attaches the shroud to the tang is just a single pin....the tang will have 4 pins ( bolts)...I don't know the diameter of the turnbuckle pin, but a 1/2 s/s bolt has enormous shear capacity

[Chotu]

Originally Posted by rslifkin

Is there any information on how much load these chainplates are supposed to be able to handle?

Definitely. A chain plate needs to easily be able to handle lifting the boat up to flip it over by the chain plate alone.

I’ll take a stab at it but may botch it. Here goes:

So, this is a 20,000lbs boat (if I do an awful job, should be a lot lighter).

20,000lbs x 25ft beam /2 = 250,000 ftlbs

The tangs are 52.3ft up the mast.

250,000 / 52.3ft is 4,780 lbs of force at the tangs to lift a hull.

Yikes!!! I had better reef early.

I’m going to just assume the entire 4,780lbs goes right into a chain plate. I’ll also assume shock loading and wave action and safety margin and say a nice round 6000 lbs should go into the chain plate.

Then there is also the other test of chain plates. You should be able to get a crane and a spreader bar sbs pick the boat up by both of them. So that’s 10,000lbs.

[Chotu]

McHughV: the designer lives 3,371 miles away. No hanging out with him. Heineken is a good choice though!

[fourlyons]

Originally Posted by Chotu

Definitely. A chain plate needs to easily be able to handle lifting the boat up to flip it over by the chain plate alone.



I’ll take a stab at it but may botch it. Here goes:



So, this is a 20,000lbs boat (if I do an awful job, should be a lot lighter).



20,000lbs x 25ft beam /2 = 250,000 ftlbs



The tangs are 52.3ft up the mast.



250,000 / 52.3ft is 4,780 lbs of force at the tangs to lift a hull.



Yikes!!! I had better reef early.



I’m going to just assume the entire 4,780lbs goes right into a chain plate. I’ll also assume shock loading and wave action and safety margin and say a nice round 6000 lbs should go into the chain plate.



Then there is also the other test of chain plates. You should be able to get a crane and a spreader bar sbs pick the boat up by both of them. So that’s 10,000lbs.

Chotu, industry standard safety factor for cruising boats is 3x. Using your numbers a 1/4" shroud would be enough... I'm sure your plans spec something quite a bit larger.

[Chotu]

Originally Posted by fourlyons

Chotu, industry standard safety factor for cruising boats is 3x. Using your numbers a 1/4" shroud would be enough... I'm sure your plans spec something quite a bit larger.

Well I was just doing that for fun. I’m not in the industry. I’m just a guy building the boat.

I have a significantly larger set of standing rigging than that. Ha ha

But what you said about 3X makes a lot of sense. I came up with something like 4000. 3x 4000 is 12,000. The boat weighs 20,000. And the chain plates should be able to lift the boat as a pair. So that would be 10,000 on each chain plate. 12,000 would be acceptable for that type of testing.

But yeah. The rigging that came with my mast is really beefy. I’ve never seen anything so thick before.

Rslifkin Was asking a bit of a side question. So I thought I would indulge him. He has always been very insightful in my threads.

[rslifkin]

I was thinking along the lines of if the plans are hard to interpret or construct, but you know what they were trying to achieve strength-wise, you might be able to adapt them into a form that's easier to build and equal or stronger (if maybe not quite as weight efficient).