Chain plate questions:

[Chotu]

Originally Posted by rslifkin

Hmm... Those knobs sound kinda like load bearing locator studs. I assume the bolts don't go through the knobs?



I don't know how practical it would be, but I'd think it would be stronger to make the knobs from G10 rod going through the hull and backing plate vs just building up thickened epoxy for them.

No. The knobs are three-quarter inch pieces. The bolts are 1/4 inch pieces. The knobs have three-quarter inch holes on the chain plate. The bolts have 1/4 inch holes on the chain plate.

I mean yeah. Lots of things we could do could make things stronger. But none of it is necessary. I have the design for the chain plates in hand. The second or third most famous Catamaran designer in the world designed these chain plates already for the boat he designed. I know we have a lot of fun coming up with new ideas, but this is not a place to do it. I just need to know how to put these together properly.

I definitely don’t want to reinvent the wheel here either because we won’t invent a better wheel. He has already put in countless hours on the computer designing all of this. He uses finite element analysis and everything is perfect. This is the lightest weight thing that is the strongest. That’s pretty much his specialty.

The entire boat was designed that way. I definitely don’t want to be changing his design work. That’s a good way to get into trouble. Or to make something awful and heavy. Either way, we aren’t going to do better than he did. Not without finite element analysis. Because that’s what he used.

Really I just need to get a handle on what materials to use for the structural filler that makes up those knobs, maybe where to get that G 10 sourced from. I need 1/4 inch ID, which hopefully 1/4 inch bolts can slide into? I don’t even know. Ordering things online kind of sucks. Because you never know what you are getting.

And then I also need to know if I can do all of these layers ahead of time, and then secondary bond those knobs on. I’m not sure. I’m not sure at all about the process of how to do this correctly. And that’s what my designer doesn’t give you. Any of the process. He gives you the drawings. The final product.

[seandepagnier]

Originally Posted by Chotu

I definitely don’t want to reinvent the wheel here either because we won’t invent a better wheel. He has already put in countless hours on the computer designing all of this. He uses finite element analysis and everything is perfect. This is the lightest weight thing that is the strongest. That’s pretty much his specialty.

compared to carbon or titanium?? both options are much lighter and stronger and from what I could find cheaper as well

1/4" bolts also seems quite small. How many per chainplate?

[Chotu]

Originally Posted by seandepagnier

compared to carbon or titanium?? both options are much lighter and stronger and from what I could find cheaper as well

1/4" bolts also seems quite small. How many per chainplate?

No, you can certainly substitute titanium in. I definitely want to do that. Where did you get your titanium for less than stainless?? You didn’t even answer the question.

He has an option for composite chain plates. I can’t make them. It’s not practical right now. If you read the rest of the thread you would notice that.

There are about 5 million 1/4 inch bolts plus the three-quarter inch knobs. That’s the best way I can describe them: knobs. But this is already all been said above. Just scroll up.

[seandepagnier]

I got from a metal repurposing place "sakinmetal" you can google for it, though I dont know you would get the thickness you desire without stacking a few. I am able to use 2x 1/8" for mine.

5 million??? You mean like 10 or 12 bolts? What is a knob? Is this a bolt too? Can you post a picture?

anyway.. I am doing all titanium, so titanium bolts and the cost ends up the same. I don't want to mix with stainless anywhere to avoid any galvanic corrosion. So I have titanium everything and the cost is about the same because high cost of titanium bolts plus the pain of cutting titanium. all the stays are heat stretched dyneema also much lighter weight.

[Pauls]

Hi Chotu,
Regarding where to order your G10, I suggest McMaster Carr. They have a large selection and they are a very reputable supplier. By the way, I second the suggestion to use G10 bushings to support your loads. The bolts holding your chainplates should be fully torqued and that is a lot of compressive load. The G10 will handle that fine, it has a high percentage fiber content. It is far superior to any sort of fill made from liquid epoxy and some filler.

Regards your question about whether the load on the chainplate is taken by the bolts or by friction, the real world answer is both. When designing this joint, an engineer would prefer to calculate the bolt clamping loads, apply a coefficient of friction to that and have a friction load carrying ability that exceeded the breaking strength of the shrouds. That's theory. In the real world, with less than perfect fiberglass surface, bedding compound, etc depending on friction for all the load carrying is iffy. I'd expect the designer to use enough bolts that they will carry all, or at least the great majority of the shroud load. This is the safest design. Friction definitely is there and the reality is loads are carried by a combination of friction and bolt shear loading.

[rslifkin]

If I'm interpreting the description correctly, the "knobs" are cylindrical studs on the hull that fit into holes in the chainplates to provide locating and shear strength beyond what the bolts provide.

[Chotu]

Originally Posted by rslifkin

If I'm interpreting the description correctly, the "knobs" are cylindrical studs on the hull that fit into holes in the chainplates to provide locating and shear strength beyond what the bolts provide.

Man, you’re good at figuring out things. That’s exactly what they are. They are cylindrical studs created from structural filler, whatever that is, That are part of the hull itself. They are created using the chain plate as a template. Squeeze the structural filler right in there.

In fact, I’m thinking those take just about all the force, and the bolts are basically there to keep it in line with them. So it can’t pop off of the cylindrical studs.

This makes it lightweight in comparison to an all metal solution.

Given that these knobs probably take the whole load, that’s why I was thinking that the structural filler should be glass fiber filler.

[Chotu]

Originally Posted by seandepagnier

I got from a metal repurposing place "sakinmetal" you can google for it, though I dont know you would get the thickness you desire without stacking a few. I am able to use 2x 1/8" for mine.

5 million??? You mean like 10 or 12 bolts? What is a knob? Is this a bolt too? Can you post a picture?

anyway.. I am doing all titanium, so titanium bolts and the cost ends up the same. I don't want to mix with stainless anywhere to avoid any galvanic corrosion. So I have titanium everything and the cost is about the same because high cost of titanium bolts plus the pain of cutting titanium. all the stays are heat stretched dyneema also much lighter weight.

Wow. That’s really nice stuff. If I had another year to just play around I would totally do what you are doing. But I don’t. I need to get this boat done before I die. Lol

The way you have it is the dream set up. For sure.

Thank you for the name of the place to look into getting that metal.

[rslifkin]

Originally Posted by Chotu

Man, you’re good at figuring out things. That’s exactly what they are. They are cylindrical studs created from structural filler, whatever that is, That are part of the hull itself. They are created using the chain plate as a template. Squeeze the structural filler right in there.

In fact, I’m thinking those take just about all the force, and the bolts are basically there to keep it in line with them. So it can’t pop off of the cylindrical studs.

This makes it lightweight in comparison to an all metal solution.

Given that these knobs probably take the whole load, that’s why I was thinking that the structural filler should be glass fiber filler.

The knobs taking the whole load is what gave me the G10 rod thought. One of those cases where I don't care if the math says the filler is strong enough, it doesn't make me warm and fuzzy. I'd probably embed slightly undersized rods all the way through and then just use the filter to get the perfect fit to the chainplate holes.

[Chotu]

Originally Posted by rslifkin

The knobs taking the whole load is what gave me the G10 rod thought. One of those cases where I don't care if the math says the filler is strong enough, it doesn't make me warm and fuzzy. I'd probably embed slightly undersized rods all the way through and then just use the filter to get the perfect fit to the chainplate holes.

I don’t think that’s how they work though. They aren’t acting like bolts.

They are just grips.

That way the whole load is spread into the biax and plywood layers below them.

Just envision the chain plate tugging in sheer on the hull. Same way composite chain plates do.

It’s not tugging on the core. Or a backing plate. It’s tugging on the hull in general

It tries to pull the big biax and plywood pad along the hull in sheer. Not happening.


The knobs are 3x wider than they are tall. 3/4” wide, 1/4” tall off the surface of the hull.

[MicHughV]

ok, gotcha.....forget about friction....not even remotely strong enuff. We are talking about loads that can be substantial, think in tons here...

If it were me, some things I would consider.......know ahead that I know little about your boat construction so may be talking off the top of my head...

1. I'd remove the inner fiberglass liner, and all the core material, in the area where the chainplate would locate, ie, if the chainplate were...say.....12" long x 6" wide, and insert a piece of teak, the same thickness as the core you removed....but wider, 12-18" wide x that in lenght, suitably epoxy coated (have someone do this for you), alternately you could consider a thick piece of structural fiberglass or other laminate. I'm reluctant to suggest this knowing your situation with epoxy. Locate the teak piece so the grain is perpendicular to the load..ie, have the grain of the wood horizontal, then glass it over. Need to be sure you have something structurally solid above this piece, like a stringer, hull/deck timber, etc...as previously mentioned, not sure how your boat is built.

I know this will require some glassing or epoxy work, so may have to have someone do it for you.


2. If, for instance, your chainplate bolts are 1/2" in diameter, I'd get some s/s tubing, with an inner diameter of around 5/8" so that it can fit over the chainplate bolt or better said, your 1/2" bolt can fit thru' this tube. Drill an appropriate size hole in the hull/teak to allow for the outside diameter of this tube. Cut the lenght of this tube to match the hull thickness. This will be your bolt sleeve. Hate to say this, but epoxy sleeves into place or use 5200. It will serve two purposes. a. It will distribute the load on the bolt over a wider area, as the sleeve diameter will be substantially larger than the bolt diameter and b. it will prevent compression of the hull. Prior to inserting the chainplate bolt, chainplate, backing plate/washer, slather some 5200 on it, so water, moisture, etc, can't find it's way in.

As mentioned above the s/s sleeves can also be fixed into place with 5200

I'm assuming here, that you will have a backing plate of some sorts, or large washers.

Again, these are suggestions. I'd love to come see your boat and put my eyes on it. Nothing like a visual to aid suggestions.

Other suggestions here are similar, so you have some options to consider.

Finally, your hull/designer may have already considered all this, in which case, you need not do anything, but I'd still recommend the s/s sleeves as outlined above.

Hope this provides some guidance.

Some other things to consider. all the bolts will be in shear. Typically, the shear value of a bolt is about 50% of it's tensile strength. I don't know what size, grade or how many bolts are in your chain plate... You can't always assume that all the bolts will be equally loaded, so careful and accurate location of your drilled holes is very important.

I will assume that your nautical architect has figured all this out for you, so the important part for you is to accurate drill bolt hole location.

Hope this answers some of your questions.

[Benz]

Chotu--structural filler is usually just colloidal silica--Cab-o-sil. The way you're describing the chainplate, and the way even the tiniest drip of Cab-o-sil, which always hardens into a sharp dagger (why is that?) has the power to tear both flesh and clothing, I'd imagine that would be what the designer wants. Glass fibers are just like bigger lengths of cab-o-sil, but they're smooth, and lack the amorphous properties that help Cab grab together. I'm not a scientist, but I think that it's the microscopic corners and angles on Cab that help it hang together so well.
If I was in jail and had to make a shiv, I'd use Cab-o-sil over glass fibers all day.

[Chotu]

Originally Posted by Benz

Chotu--structural filler is usually just colloidal silica--Cab-o-sil. The way you're describing the chainplate, and the way even the tiniest drip of Cab-o-sil, which always hardens into a sharp dagger (why is that?) has the power to tear both flesh and clothing, I'd imagine that would be what the designer wants. Glass fibers are just like bigger lengths of cab-o-sil, but they're smooth, and lack the amorphous properties that help Cab grab together. I'm not a scientist, but I think that it's the microscopic corners and angles on Cab that help it hang together so well.
If I was in jail and had to make a shiv, I'd use Cab-o-sil over glass fibers all day.

Thank you!

Thanks for coming through and answering my questions.

During the build there were places I had to add glass fiber filler for extra strength in addition to colloidal silica, for thickening. These were some areas of extra strength like where the cross beams were glassed into the hulls.

Somehow in my mind, I was thinking that’s how this would be working too.

But you’re absolutely right. A nub of colloidal silica and epoxy is not going anywhere. Ever. Not even with a grinder. Ha ha.

I’ll use neat epoxy with colloidal silica here.

One more detail:

There are several layers of plywood and biax below the chain plate anchor plate. The thing that has the 3/4” holes for the nubs and the 1/4” holes for the bolts.

This is a buildup from the hull surface. The hull itself already has non crush core in that area.

Doing this buildup, does it all need to be wet on wet and fast work all the way to the nubs? Or is a bit of secondary bonding ok?

[rslifkin]

I'd prefer wet on wet if possible. At least for the nubs to the outermost layer below them. Probably doesn't matter as much for the plywood bonds.



As long as it can all be done in a day for a single chainplate once everything is prepped, I'd expect a slow enough hardener would allow it to be done wet on wet without any craziness.

[malbert73]

Originally Posted by Chotu

Actually, I may have answered my own question.

My last post asks about bedding the chain plate. It has some large bog “bolts” as part of the design. Made with structural filler. Should I use glass fibers there? It definitely beds in bog.

Does that mean the whole thing has to go wet on wet? Or does it mean I can do the build up, then a secondary bond to put the actual chainplate on for the final bolt down?

My designer is great at coming up with light, strong things and drawing them. Not so good at letting you know how to make them. Ha ha

Then my bolts themselves are 1/4”. Can I get G10 or FRP tubing in 1/4” ID? Can i get it fast somewhere?

Need it ASAP. Anyone know where to pick it up? It’s small stuff.

Mc master carr ships quickly