Would anyone be willing to help me interpret chainplate plans?

[Chotu]

Originally Posted by MicHughV

Yep, that would be an awesome idea.....would love to see your boat one day. I've sailed on a few cats, but none that big.
Ya, some good guys on this forum, for sure.

And probably none with this sail area to displacement ratio either.

Things are very light. And there’s a pretty big mast!

It should be a lot of fun actually.

[Chotu]

So, I think I have had enough time today to study all of this, I thank you for all of the input on this thread.

But I have to make an executive decision.

The executive decision is the composite chain plates are just plain easier. There is no doubt about them working. There are no drips or leaks. There is nothing negative about them at all actually. Just have to get them laminated well.

I’ve been talking to some other people in the background that have done composite chain plates, and they’re not too bad. Nothing to be afraid of doing. Slow Hardner is the key.

So, I guess this thread has come to an end. There were some great ideas in here. However, getting them off the ground will probably take longer than the composite chain plates because I already know how to do the composite chain plates. There are no questions about them. They are straightforward. The designers plan for the composite chain plates is very clear. There’s no room for interpretation or ambiguity.

So, that’s the way we’re going to go.

It’s the most simple.

[Rumpi]

Originally Posted by Chotu

1) In the drawings of the chain plate and support plate, it is very difficult to tell how far up the support plate is supposed to go. Do you have any idea from the plans? Does it go all the way up into the deck lamination?


2) How do the bolts that hold together the chain plate and the support plate work? They are not shown at all in the drawings. Do they go all the way through the hull? Or do they end inside the boat?

3) what exactly is the reinforced deck plate? And how do you install it? What are the specific layers of glass to go there?

4) The hull isn’t flat like you had mentioned. So, how do I put the flat pieces of plywood on there? Do I fill the gap? You talked about grinding, but that takes away the skin and leaves a very thin core left. There would be just core showing after that.

5) to be double and triple clear, there is nothing but some machine screws holding it to the outside of the boat. Correct? Just beef up the glass a little bit like it describes, put in the machine screws, then glass them over? That’s it?

1. It goes trough the deck, right to the "reinforced deck plate" ("exits cabinside")
2. All bolts go trough the hull ("typical")
3. A steel or fiberglass plate, formed to the hull, it seals the opening, it mounts with 4 screws into the deck. It's a normal detail seen on most internal chainplates.
4. The designer wants you to bend the plate (that's what "break formed" means), but you can just add ply over his layup and grind it flat. You do the grinding before the last layer of glass.
5. Yes, that's it, and that's why so many screws, to guarantee none will pull trough. Plus of course his bog filled holes.

I read you decided to do composite ones, but anyway, the plans are actually clear.

[Chotu]

Originally Posted by Rumpi

1. It goes trough the deck, right to the "reinforced deck plate" ("exits cabinside")
2. All bolts go trough the hull ("typical")
3. A steel or fiberglass plate, formed to the hull, it seals the opening, it mounts with 4 screws into the deck. It's a normal detail seen on most internal chainplates.
4. The designer wants you to bend the plate (that's what "break formed" means), but you can just add ply over his layup and grind it flat. You do the grinding before the last layer of glass.
5. Yes, that's it, and that's why so many screws, to guarantee none will pull trough. Plus of course his bog filled holes.

I read you decided to do composite ones, but anyway, the plans are actually clear.

Sir, I have to hand it to you. You are a genius. You are above the rest of us in intelligence. Because none of us could figure the plans out except you. And what you said makes total sense. I have already gone ahead and ordered all the fiberglass for the composite chain plates and got everything rolling in that direction already. They certainly don’t appear to be more work than these chain plates. So, it’s probably the best decision anyway.
But thank you very much for translating these plans. I can’t believe you figured all that out. Have you built one of these before or something?

[rmlarson1098]

Originally Posted by Chotu

I’m getting the steel work done.

I’m trying to describe exactly what I need for the chain plates and send the plans to the fabricator. But I can’t understand the plans as is often the case.

I can’t post the plans publicly, but I certainly can share them privately. I was wondering if anybody might help me interpret the plans. From what I see, installing the chain plates internally, the plans don’t show a backing plate. So I’m very confused.

Can anyone take a look at them with me and see if you think there is some kind of backing plate on the outside of the hull?

Edit: I’m just going to post the plans here with a lot of information redacted so I’m not giving up intellectual property.

Ok, here's a thought. Is the boat completed to the point where you can't weld (without starting a fire) on the deck? Or hull? If not, scrap the plans and weld a doubler plate on the deck, with a pad-eye on top of that, for each chainplate. Or to the hull if you can live with them outboard. Build from there. Think of where Moitessier sailed, with galvanized cable, eyes made with cable clamps, and turnbuckles. And telephone poles for his masts. As they say in the trades, we ain't building Bulova's here.

[captlloyd]

It’s all there if you study and read carefully. An extra glass build up on hull exterior, a plywood/ fiberglass triple (3) build up on interior. All looks fine to me. 1/2 inch chain plate with 1/4 inch stainless back up on interior. As I can’t see the bolt pattern drawing I can’t determine the bolt layout. The drawing shows interior glass layup, looks like it is tied into frame also.

[captnknopf]

I had a similar problem with the chain plates on a 39 foot tri I built. I think what Kurt is saying is to remove all core in a big area around the chain plates and glass the heck out of it. I prefer uni to wr at all times. Because the force on the bolts is in shear, adding outside plates if the core is solid does not add any strength. I do not care for the glassing over part tho. Putting a quarter inch or even eighth inch plate outside to act as a big washer would make sense but it is just to reinforce the head of the bolt. The glass area next to the chainplate on the inside needs to be really dense. I would love to drive over to talk about it with you. I am about two hours away.

[Manateeman]

The manatee crew can vouch for the credentials of Captain K...
A true gentleman and fine boatbuilder.

[Chotu]

Ah. It is indeed a small world!

Why do the ice-breaking, polar bear proof, deadhead busting northern manatees socialize with all the speedy multihull types?

It would make for an interesting nature documentary. These are some very non-biased manatees. Allowing others from different tribes into their realm.

The executive decision was made and all materials are on their way for assembly.

[smj]

Originally Posted by Chotu

Ah. It is indeed a small world!

Why do the ice-breaking, polar bear proof, deadhead busting northern manatees socialize with all the speedy multihull types?

It would make for an interesting nature documentary. These are some very non-biased manatees. Allowing others from different tribes into their realm.

The executive decision was made and all materials are on their way for assembly.

The manatees always have beer and pizza so the multihullers reluctantly let them into their circle.[emoji16]
Anyone that has a boat built out of recycled Budweiser cans has to have some redeeming qualities? [emoji23]

[Kim Klaka]

Those are some of the most inadequate drawings I have ever seen in my many decades as a naval architect, including years of teaching yacht design. Tear those drawings up and find a qualified naval architect with yacht design experience to design you some chainplates. Whatever their fee, it will surely be much cheaper than losing the rig.

[Dieseldude]

Originally Posted by Chotu

I’m getting the steel work done.

I’m trying to describe exactly what I need for the chain plates and send the plans to the fabricator. But I can’t understand the plans as is often the case.

I can’t post the plans publicly, but I certainly can share them privately. I was wondering if anybody might help me interpret the plans. From what I see, installing the chain plates internally, the plans don’t show a backing plate. So I’m very confused.

Can anyone take a look at them with me and see if you think there is some kind of backing plate on the outside of the hull?

Edit: I’m just going to post the plans here with a lot of information redacted so I’m not giving up intellectual property.

These drawings do not seem to show all the required information. I do not see a specification for the fasteners. The hole spacings are not defined, and they look like they are too close. The cross sectional drawing seems to show the plate as two overlapping pieces, yet the plane view shows one piece. If the plate is in fact two pieces, the weld beads are not shown, and no weld specification is given. Of course for welding stainless, the correct alloy for the parent metal and electrode must be chosen to prevent chromium depletion and corrosion.


At the upper end, nothing is clear about the re-enforced deck plate and roving. What is the material? How is it secured and sealed? The fastening arrangement of the chain plate itself looks weak. I see no external backing plate. It is doubtful that the fastener arrangement illustrated will be strong enough with no backing plate or even large washers to spread the stress load beyond the screw heads. Fiberglass hull material is quite brittle to concentrated stress of threaded fasteners. Even the internal nut arrangement is unclear. Are these to be welded on or to be "free floating". It might be better to tap the holes rather than use nuts. The loose spec of fastener size of 1/2 inch or 12 mm is not acceptable. What allow should they be? What thread pitch should they be?



It seems that your designer has some sort of a personal quarrel against you. If he refuses to supply the needed info, go to a metal fabricator or boat shop, and ask them to write a missing specification list to give to the designer to back your demand. Have the fabricator make some notes on the drawing that note missing info. The designer might back down based upon such an authoritative demand. Maybe if you have the fabricator make the request for the missing info directly, he will cooperate with them.


If the designer will not support the supplied drawing with complete information, you should demand a refund. It seems that a fabricator or boat shop would not be able to do the job based upon this drawing. This is quite a costly and critical job that leaves no room for guessing and misinterpretation. Costly fabrication and holes drilled in the hull would not be easy to correct if done wrong. At worst, hull damage could result if the arrangement cannot support the stress load. The fabricator and fitter require all information to do a satisfactory job.

[Bunnellr]

I really don't like the design. Strain is placed on the upper, through-hull screws, into the sides, then the deck. Also the other thoughts above. Fire your designer. It's too important.
Bob
Webb Institute '77

[fishead]

When I was looking for a designer for my last boat, I spoke to one with the same initials for fifteen minutes. That was all it took for me to go to someone else with CW initials. Sorry for all your troubles. If you had more time I know someone in the Coco Beach area who could build composite chainplates for you.

[cohort]

Are these replacement chainplates? Going on a 50ft. Cat? If replacement, can you just use the current chainplates as templates for the new ones? I'm no expert, but the design looks overly complicated. I replaced 12 chainplates on my 48ft Ketch a few years ago. To insure I was getting what I wanted I only provided the manufacturer two chainplates at a time to produce. In addition to a chance to QC the product, I also only had to remove two at a time, thus keeping the rigging intact. My last thought, if the designer isn't willing to discuss and explain what he is doing and why, find someone else to do it.