External Track For Batten Cars?

[Chotu]

I had a thought regarding rigging. I’m ordering a bunch of structural pultrusions shortly.

Had me thinking I may price out carbon fiber/epoxy mast pultrusions at the same time.

If I did this, I doubt they could do a pultrusion as complex as the attached pic without significant tooling cost.

So what if they just did me an oval and I added a track for batten cars on the outside of it?

1). Is that possible with a carbon fiber mast?

2). Is it advisable at all? Will it work or will they get jammed and stick or some other undesirable effect? We are talking large roach, flat top, full batten main.

3). How do I attach my tangs, spreaders, other hardware to a carbon fiber mast? Can I do this with fasteners somehow?

4). If I know the 2nd moment of inertia as well as an aluminum section that works for the rig, how can I specify a carbon section, given the material properties are different?
Moment of inertia only defines the shape of the mast. It does NOT define wall thickness. How do I know what wall thickness to use? The below wall thickness is for aluminum.

Thanks!

[Matt Johnson]

I don't know of a carbon mast that doesn't use an external track. Typically, they have a flat end in the profile - like your attached image - and the track gets attached there.

Matt

[Chotu]

Originally Posted by funjohnson

I don't know of a carbon mast that doesn't use an external track. Typically, they have a flat end in the profile - like your attached image - and the track gets attached there.

Matt

Thank you. I don’t know anything here so I’m trying to understand.

I just read tracks are typically put on a carbon fiber mast using adhesive rather than fasteners.

Does anyone know of a good system for an external track and cars or slides that works well with big catamaran full batten mains with a square top on a carbon mast?

Which is better? Cars or slides?

[Matt Johnson]

One other thing - If you're going carbon, and if you have the strength to really tension the rig, then think about a fixed spreaderless mast. It's what all the cool kids with performance cats are doing nowadays

Matt

[Chotu]

Originally Posted by funjohnson

One other thing - If you're going carbon, and if you have the strength to really tension the rig, then think about a fixed spreaderless mast. It's what all the cool kids with performance cats are doing nowadays

Matt

Thanks for the idea! I see one here on this Gunboat.

Anyone have any thoughts on how to get from known moments of inertia on the plans and a known working aluminum mast section to the right scantlings for a fixed spreaderless carbon mast?

[Chotu]

Looks like this is how tangs are done too. But I’d have to hire the epoxy work out which isn’t cool.

[Jim Cate]

Chotu, I have applauded many of your ideas and innovations, but this is one place where if you want to go to a custom carbon rig you really need to go to a pro rig designer, not depend upon your instincts and some internet advice.

Not so long ago you were asking how to determine if a used alloy spar would work, and that is dirt simple compared to designing a carbon rig from the ground up.

What could possibly go wrong...?

Jim

[Chotu]

Originally Posted by Jim Cate

Chotu, I have applauded many of your ideas and innovations, but this is one place where if you want to go to a custom carbon rig you really need to go to a pro rig designer, not depend upon your instincts and some internet advice.

Not so long ago you were asking how to determine if a used alloy spar would work, and that is dirt simple compared to designing a carbon rig from the ground up.

What could possibly go wrong...?

Jim

Jim,

It’s not even that complicated.

I’m looking at the used aluminum spar this week and pricing out a pultruded carbon tube with the right 2nd moment of inertia to see if I can come up with a better solution than an old used mast.

The only piece I don’t know at this point is how to reverse engineer a carbon tube’s wall thickness from a known aluminum section’s wall thickness. I think Young’s modulus is involved, but most of the data on the carbon tubes seems to give tensile strength. I have to do a little more investigating to see how to bridge that gap if no one here knows.

The only thing I’m having any issues with is that last little bit. Determining wall thickness. I have the section profile already from the 2nd moment of inertia.

Just like the other thread. No one is DESIGNING a carbon rig just like no one is DESIGNING an aluminum rig. I’m FINDING or MAKING one to fit the design.

Big difference. I hope we don’t see all the fear here like in the aluminum thread.

The level of fear of math people seem to have is strange to me. The “experts” aren’t doing anything special. They are applying engineering mechanics equations to a geometric cross section.

I like to ask questions. It’s how I learn. I don’t have a team here so it’s invigorating to bounce ideas off the crowd and see what comes back. It’s how my mind works. I process tons of different inputs to synthesize a solution. Asking forum questions is a big part of that. I don’t just come on here posting the engineering mechanics equations. I ask broad, general questions to see what kind of “outside the box” thinking people come up with.

A “pro” is always just a regular person who was taught how to do some stuff. Anyone can do what they do. You just need to figure it out.

As a group, it surprises me when sailors get all frightened of things and suggest bringing in the pros on here. We are supposed to be fiercely independent, self sufficient types. Yet the littlest fiberglass repair project and half the forum is in a panic saying to hire a “pro” who more often than not botches the job anyway.

I didn’t know how to build a boat before I successfully built a 50’ Catamarans using state of the art vacuum resin infusion.

I have never done the (not even difficult) math to calculate the proper carbon mast section from 2nd moment of inertia and a known aluminum wall thickness. But it’s sure a hell of a lot easier than building a boat. Much faster to figure out, too.

The big wildcard here is the spreaderless design thrown out above. I don’t have the proper design for that. That would involve some rules of thumb known to a rigging shop or a complete redesign of the mast by someone. But for a double diamond spreader setup with forestay and swept back shrouds with no backstay? I have that design already.

Sorry to carry on like this. My post isn’t really directed at you, personally. It’s directed at the “No one can possibly do it, better hire an ‘expert’ “ crowd that dominates a lot of discussions here.

Fact is, anyone can do anything if they try.

[Jim Cate]

Fact is, anyone can do anything if they try.

Sorry, I simply do not agree with this bold statement, Chotu.

And rig design, as you allude to at times, is more that the moment calculations for the tube. The details of attachments, tracks and other details are where many rigs fail.

I'm far more comfortable with substituting a used spar whose details were successfully designed than starting with a carbon tube... bare as a baby's bum, no matter how stiff the tube might be.

I didn’t know how to build a boat before I successfully built a 50’ Catamarans using state of the art vacuum resin infusion.

And, not wishing to sound negative, but you have perhaps built your boat but you have not yet proven that it is a successful sailing yacht. It seems to float, and that is a good start, but you have a few hurdles to jump before you can really say that you've "built a 50 foot cat".

I know how few of us have achieved as much in the way of a build as you have, but it ain't done yet. I'd sure be happier if you got some expert advice on the rig... and I'm definitely not one of the "call a pro" for everything types.

Carry on, mate!

Jim

[Chotu]

Originally Posted by Jim Cate

Sorry, I simply do not agree with this bold statement, Chotu.

And rig design, as you allude to at times, is more that the moment calculations for the tube. The details of attachments, tracks and other details are where many rigs fail.

And all that is already specified on the plans. I guess you don’t realize I bought plans to build a boat from ?? Those details are included in the rigging plan, believe it or not.

And you don’t believe anyone can do anything they set their minds to? How do you think one becomes a rigger or designer then? They have the ability from birth?

I'm far more comfortable with substituting a used spar whose details were successfully designed than starting with a carbon tube... bare as a baby's bum, no matter how stiff the tube might be.

I’m far more comfortable using the designed parameters of my boat’s ALREADY DESIGNED rig to build the rig in my plans than to substitute the rig from a similar boat. But you don’t seem to understand there is a rig specified in my plans for some reason. I may end up with the used aluminum rig anyway to save money depending on the cost of this carbon section. I’m going with the less expensive one most likely.

And, not wishing to sound negative, but you have perhaps built your boat but you have not yet proven that it is a successful sailing yacht. It seems to float, and that is a good start, but you have a few hurdles to jump before you can really say that you've "built a 50 foot cat".

This part should be reported to the mods. You are one, right? What happened to the “be kind” ethos? An attack on my boat is a personal attack in this case.

Another fact you seem not to be aware of? My boat has a little over 1500 nautical miles on it already.. Yes, I HAVE successfully built a 50’ cat as proven by sea miles. It’s not a sailboat yet and I’m still fussing over the interior and plenty of fittings but I could take it to your location to show you if we were to pretend I could store the required fuel for such a trip., or give me a chase boat carrying all the fuel. I have a fully functioning displacement cat trawler with a functioning galley, solar, fresh water, propane, generator, fuel system, auto helm, nav lights, dinghy, refrigerator/freezer, etc etc.

I’m finishing off the interior and doing some fine tuning of a few areas plus adding a rig and everything you need to support one.

The boat will sail just fine. There are discussions on here about a sistership’s sailing ability right now. I think they are doing 60-80% of wind speed without anything more than main and 100% jib. So it’s certainly going to sail well. Heck, I’ll race ya when it’s got a rig.

I know how few of us have achieved as much in the way of a build as you have, but it ain't done yet. I'd sure be happier if you got some expert advice on the rig... and I'm definitely not one of the "call a pro" for everything types.

Carry on, mate!

Jim

It’s not done yet. I’m with you there. Lots of hours left. But it’s a successfully built boat.

Let me ask you this: The rigger that is going with me to look at the used rig this week... is it so wrong for me to know what I’m talking about when I go with him? Is it really that wrong to go in there knowing full well what the section profile for mast and boom should be? What the wall thickness should be? What the length of my mast and boom should be and what my chainplate angles ought to be?

Is it also wrong for me to know the same things about potentially doing carbon tubes?

Or should I blindly hire an “expert” and hope my day isn’t the day he has a big hangover or personal problems at home? Just trusting him to get it all right without even knowing the basic parameters myself?

I used to hire “experts “ to work on my cars. I would never let one touch a vehicle I own anymore. They do the bare minimum and often do things wrong or break other things while fixing what you came in for. This is the same type of situation. You can literally learn anything. That’s the beauty of being human and motivated. You know a lot of things. I seem to remember you and I may share formal training in physics in common and have worked as physicists in the past ages ago. Do you not think you could pick this up? All the “expert” brings are rules of thumb and experience knowing what most people do. The math? It’s free and open source to all. I’ve used quite a bit of it building my boat.

[GregW1309]

Moment of Inertia is a geometric property, has nothing to do with material properties. For your mast shape if the geometry is the same (and wall thickness is a key parameter), the moment of Inertia will be the same for any monolithic material. Where material properties come into play is when you calculate stress, buckling, and failure modes. When you are dealing with devices that when failed can lead to injury or death, you need to hire an engineer, preferably one who has experience with the device / technology your dealing with. Otherwise you embark on a development process, during which you should expect some failures...

[Matt Johnson]

FYI - the used rig you are looking at is on eBay and seems to be getting a lot of looks. With the winches and everything else that's included, I'd probably hit the "buy it now" if it weren't for the fact that you're the one that clued me in to it... you have first dibs.

Go buy that thing now!

[Chotu]

Originally Posted by GregW1309

Moment of Inertia is a geometric property, has nothing to do with material properties. For your mast shape if the geometry is the same (and wall thickness is a key parameter), the moment of Inertia will be the same for any monolithic material. Where material properties come into play is when you calculate stress, buckling, and failure modes. When you are dealing with devices that when failed can lead to injury or death, you need to hire an engineer, preferably one who has experience with the device / technology your dealing with. Otherwise you embark on a development process, during which you should expect some failures...

Which is what I said earlier.

This is, at least, a rational response to the post.

Still doesn’t mean I can’t figure it all out first instead of blindly hiring someone and hoping they do a good job the day they work on mine.

[Chotu]

Originally Posted by funjohnson

FYI - the used rig you are looking at is on eBay and seems to be getting a lot of looks. With the winches and everything else that's included, I'd probably hit the "buy it now" if it weren't for the fact that you're the one that clued me in to it... you have first dibs.

Go buy that thing now!

I’m on it l! Waiting in the expert currently who hasn’t told me when he can look at the rig.

I have, however, sent him my complete rig plan, plus lots of pics of this donor rig.

[PirateFoxy]

Generally speaking IME, what makes someone a pro of this sort is not being able to do the math, it’s knowing WHICH math to do when/where, and also knowing when what the math is telling you just doesn’t look quite right and that you’ve likely made a mistake somewhere.

Given that carbon fiber and aluminum have some quite different properties, wouldn’t the original design specify or assume a specific material? If so wouldn’t it need to be properly evaluated if the material was changed, to make sure stresses are still handled correctly and so on?