Want to Rent: YOU! (Expert Epoxy Laminator) [South Florida]

[Sand crab]

Originally Posted by Chotu

Aren’t you the one that saved my life suggesting I use PLMaxPremium and Fuze-it? Those two products have been working like CRAZY keeping the most difficult things bonded. Thank you!

What do you mean by structural epoxy adhesives? Different than normal epoxy but similar? No amine hardener part?

What do you mean by “do you have any on top?” I’m confused at that part.

I am the Fuze-it guy. You're welcome.
West makes G-Flex and other types structural epoxy, System 3 has T-88 and others plus there are many other manufacturers. West products have amine blush but System 3 doesn't I think. I looked at the data on T-88 and it didn't really say.

Some boats mount the chain plates through the topsides of the hulls but near the outsides. Some do this with the metal bolted underneath but coming up thru the deck. I have seen composite chainplates on the topsides that were engineered to be lifting points for a crane. Balance may have this feature.

[jimbunyard]

Originally Posted by Chotu

Can anyone expand on this?

I have been plans for stainless chain plates, but there are a lot of extra epoxy specified laminations involved. Basically, exactly like this. A big mounting pad.

I already took care of the core of this area in anticipation of maybe using stainless. It is not the normal core. It’s a special high density core that was put in there instead.

What I have trouble picturing in my mind is the sheet on those bolts. It seems like they would pull through the fiberglass and core to me. Maybe I’m wrong.

To be done 'properly', there should be a matching inner plate (if you have CPs on the outside).

Ideally, there should be solid glass in way of the two plates; if the core you have in there now is of sufficient density, in theory that would work too.

For a cautious person like me, I would like to see some extra laminations installed there in the initial layup.

In case you're unaware, the resistance to the tensile force exerted on the CP by the shroud is pimarily provided by the friction between the plate and the hull when they're clamped together, not by the shear strength of the bolts.

If being installed on a cored hull, even with a high-density core, to avoid point loading at the bolt heads or nuts the prior statement would make a full backing plate mandatory, in my eyes...

[Sand crab]

These guys in the UK developed a system for manufacturing composite chainplates.
Chainplate – FLiNK

[Adventuresail]

This is the chainplate knee that I bonded into the hull during our complete rebuild. I used epoxy

[Manateeman]

As a builder, I’m really impressed with the Flink chainplates. I’d send them everything about your boat and get their recommendations. Maybe also ask if they have advice in your cored hull...how best to transfer the loads.
Inspecting lightning damage would be another thing I’d ask about.
Very interesting thinking in the design and I’m sure they will have some good suggestions. Great post above.
Mark

[smj]

On our TRT the core was removed and the solid glass built up where the chain plates bolt through. No backing plates just fender washers and no signs of stress in the laminate after 20 years
Being a performance cat, you would probably flip the boat before putting undue stress on then chain plate or there mountings!

[Narfi]

I know you don't mind being creative, and you can not work with epoxy, but I would still stick with the designers recommendation for something like that.

Are there no local options for composite 'experts'? I would think it would be better and cheaper to higher a local shop to do it for you.

If I was closer and could afford the time off, I would volunteer just for the chance to have a hand in your build and poke around all that you have done already. Seriously though, I would try to stick with the designers plans and higher a local shop to do the work you need to avoid.

[captnknopf]

with the right cross section of the bolt and glass the bolts are going through is should not be too difficult to calculate the sizes. One thing to think about is how much stretch there will be in the metal chain plate (assuming you would like to go as thin as possible. Using the stretch at maximum stress, you can enlarge (oval) the top holes by the amount of stretch and enlarge the lower ones less and the bottom ones not at all so at full stress all the bolts take the same load. With all the holes drilled unloaded, the top bolts take most of the load. Lots of fun calculations.

[Sand crab]

Most claim titanium chainplates are better than SS. Allied is a US manufacturer and has been making these for at least a decade that I'm aware of. They even have some in stock. And have lots of other TI boaty bits like bolts, sheaves, mast bases, turnbuckles, stanchions etc. Colligo can order them for you but I wonder if they get them from Allied? I'd definitely avoid any Chinese made ones.
https://www.alliedtitanium.com/produ...dc_Results.php
https://www.colligomarine.com/produc...um-chainplates

[jimbunyard]

Originally Posted by Narfi

I know you don't mind being creative, and you can not work with epoxy, but I would still stick with the designers recommendation for something like that.

Are there no local options for composite 'experts'? I would think it would be better and cheaper to higher a local shop to do it for you.

If I was closer and could afford the time off, I would volunteer just for the chance to have a hand in your build and poke around all that you have done already. Seriously though, I would try to stick with the designers plans and higher a local shop to do the work you need to avoid.

This is probably the best advice in the thread.

As with your thread regarding building a cabin top beam a few months ago, it is clear that some of the suggestions here are from those who have neither looked at the drawing you've supplied, nor understand the forces that are being discussed. or the subtleties involved with the design under consideration.

Again, in no particular order.

Has anyone noticed that the hull is curved? Which would require either a chainplate matching that curve or an unattractive and perhaps stress-inducing flat epoxy 'pad' be laminated onto the hull to accept a flat chainplate.

The FRP chainplates hull configuration as designed are two parts of a considered system; the tensile force of the shroud is equally distributed to each side of the 'skin' of the hull, which resists the tendency for core/skin delamination that would result from loading on only one side of the cored hull.

For similar reasons, the 'idea' of using 'fender' washers here is especially egregious; the torque necessary to clamp the chainplate tightly enough to the hull will alone (depending on the properties of the core) most likely result in an eventual loosening of the CP due to core compression. And, not to forget, the in-shear twisting of the bolts induced by the one-sided loading of the chainplate. (which a full matching backing plate will alleviate but not eliminate)

From your previous posts regarding interior fitments it is clear that both cost and weight are important considerations for you.

Weight for 8 3/8" x 2" x 18" stainless steel CP's and matching backing plates is about 62 lbs, 40 1/2" x 3" bolts and nuts adds another 10, so about 75 lbs.

Cost for the SS would probably be less than 500.00, they can be easily made and polished by you.

A similar-sized titanium plate weighs about half, but from the manufacturer listed above cost 319.00 each.

Plus, again, neither are curved, which will necessitate either more lamination work or additional expense in matching the plate to the curve of the hull.

Without knowing the laminate schedule for the existing hull, but knowing that it is designed with lightness as a primary objective, there may not be sufficient skin thickness at the location for bolted CP's. If not, this too would have to be rectified. And who makes that engineering decision anyway?


I could go on, but let's just leave it with this caveat. Making the change from laminated to bolted-on chainplates is not a simple like-for-like swap. It is a serious design change. Doing so will likely have cascading long term ill effects if the swap is not engineered and executed correctly.

[smj]

Originally Posted by jimbunyard

This is probably the best advice in the thread.

As with your thread regarding building a cabin top beam a few months ago, it is clear that some of the suggestions here are from those who have neither looked at the drawing you've supplied, nor understand the forces that are being discussed. or the subtleties involved with the design under consideration.

Again, in no particular order.

Has anyone noticed that the hull is curved? Which would require either a chainplate matching that curve or an unattractive and perhaps stress-inducing flat epoxy 'pad' be laminated onto the hull to accept a flat chainplate.

The FRP chainplates hull configuration as designed are two parts of a considered system; the tensile force of the shroud is equally distributed to each side of the 'skin' of the hull, which resists the tendency for core/skin delamination that would result from loading on only one side of the cored hull.

For similar reasons, the 'idea' of using 'fender' washers here is especially egregious; the torque necessary to clamp the chainplate tightly enough to the hull will alone (depending on the properties of the core) most likely result in an eventual loosening of the CP due to core compression. And, not to forget, the in-shear twisting of the bolts induced by the one-sided loading of the chainplate. (which a full matching backing plate will alleviate but not eliminate)

From your previous posts regarding interior fitments it is clear that both cost and weight are important considerations for you.

Weight for 8 3/8" x 2" x 18" stainless steel CP's and matching backing plates is about 62 lbs, 40 1/2" x 3" bolts and nuts adds another 10, so about 75 lbs.

Cost for the SS would probably be less than 500.00, they can be easily made and polished by you.

A similar-sized titanium plate weighs about half, but from the manufacturer listed above cost 319.00 each.

Plus, again, neither are curved, which will necessitate either more lamination work or additional expense in matching the plate to the curve of the hull.

Without knowing the laminate schedule for the existing hull, but knowing that it is designed with lightness as a primary objective, there may not be sufficient skin thickness at the location for bolted CP's. If not, this too would have to be rectified. And who makes that engineering decision anyway?


I could go on, but let's just leave it with this caveat. Making the change from laminated to bolted-on chainplates is not a simple like-for-like swap. It is a serious design change. Doing so will likely have cascading long term ill effects if the swap is not engineered and executed correctly.

How did you come up with the need for such a huge chain plate with 20 -1/2” bolts per chain plate? Way over speced.
Our chain plates are approximately 14”x1.5”x1/2” thick with 5 -3/8” bolts per plate. I looked at a Lagoon 400 and their chainplates are about 6” round with 7 bolts. And I’m pretty sure the Lagoon would see equal to or more stress as Chotus chain plate.
The fender washers that were referred to are used in a solid glass, no coring and absolutely no signs of fatigue after 20 years of mainly racing.

[Chotu]

This thread has a LOT of great information and ideas to go over. Slammed right now but will give some thought to all the alternatives and Jim, I’ll contact you within a couple days. There is epoxy work either way it goes.

[jimbunyard]

Originally Posted by smj

How did you come up with the need for such a huge chain plate with 20 -1/2” bolts per chain plate? Way over speced.
Our chain plates are approximately 14”x1.5”x1/2” thick with 5 -3/8” bolts per plate. I looked at a Lagoon 400 and their chainplates are about 6” round with 7 bolts. And I’m pretty sure the Lagoon would see equal to or more stress as Chotus chain plate.
The fender washers that were referred to are used in a solid glass, no coring and absolutely no signs of fatigue after 20 years of mainly racing.

I have no doubt that your installation is sturdy and trouble free.

We are, however, talking about Chotu's cat, which has a 1" cored hull; to modify it to fit your criteria will alone be an undertaking as 'bout as difficult as adding the FRP chainplates.

The bolts I quoted are just for reference, assuming there are 4 chainplates per side and 5 bolts per chainplate. Their actual size, bolt pattern and number would be determined by the design of the chainplate and it's installation.

The '75 lb' weight is an estimated total for all 8 SS CP's with nuts and bolts combined.

[GRIT]

Excellent points by Jimbunyard. Metal chainplates hold by friction, moreso than anything else.

Chotu's design is ready built for stainless chainplates, though they'd have to be curved slightly. The core in that area is already high density, and ready (as designed) for stainless plates.

He's decided he wants composite plates, which will not require any changes to his build, other than the chainplates themselves. I've built from the same plans, and know them well.

Someone mentioned about the chainplates being strong enough to lift the boat. They should be much stronger than that. Our plates are rated for 180,000 pounds breaking strength. I can't fathom how that is, but those are the designer's words, not mine.

As an aside, we lifted our boat with it's chainplates, and balanced it with a line going to the bow.

https://www.youtube.com/watch?v=OK7LzMabYR0

JimBunyard, the boat has two chainplates (one on either side). Unless he decides to install running backstays too.

Cheers all.
Paul.

[Sand crab]

Grit, that vid is so cool. Did you use composite plates, I don't see bolts? So, is your boat the same model as Chotus? I think I asked this before but what model/designer is it?