External Track For Batten Cars?

[johnn33]

Hi Chotu
I assume you use https://www.boatdesign.net/threads/i...ng-mast.50612/
Please may we see some photos of your beautiful catamaran?
John

[Chotu]

We share the same goal!

Top speed is fun, but consistent speed in calm conditions is the goal I share as well.

Why not go out and travel on days when the sea is calm and beautiful? I am tired of needing a gale to make progress. This is my main reason for a catamaran.

I will send you a private message now with my contact information. Thank you!

Originally Posted by Moonskater

Chotu,
I guess i have all the data, drawings and nessesary info you might need. We just have to establish another connection so it is easier to show / send pics etc. I know it´s possible here but dont know how.
The track was of course bonded with a thick epoxy adhesive.. Sorry about your allergie! My mast pipe comes from Marstrom in Sweden and is 365x170mm. my added extrution with the sailtrack makes it a 405x17 mm wing mast. The main contributor to the added performance is larger sail area, new sails UK carbon type, and the rotation feature, in that order. My goal was not to gain higher topspeed but to improve average speed and reach 6-8 knots of boatspead sooner, as that is the speed that the boat and crew likes the best for comfort.
To sail windspeed i have a 64m2 Code0 on a prodder or with a mastheadhoisted spinnaker. Maybe i managed to attach two pics. with the spinnaker we are sailing steadu 10-11 knots there.

[Nani Kai]

Hey Chotu,

I have been following your questions, queries, proposed solutions and sometimes convoluted paths to an answer for some time now. Obviously you enjoy thought experiments and hopefully have benefited from the insight and experience of members of this forum. I for one would be very interested in seeing examples of your work so as to better appreciate the success of your experiments and trials.

I do find one thing very puzzling and that is your aversion to seeking or taking the advice of a pro. <quote: A “pro” is always just a regular person who was taught how to do some stuff. Anyone can do what they do. >

I would venture to say that everyone on this forum at one time or another has a pro horror story to tell. These stories typically center around wrong advice, incompetence, shoddy workmanship or even the occasional con job by folks calling themselves "pros".

At the same time there are lots of folks out there who know their stuff, have paid the price through education, experience and hard work and who have learned from mistakes and successes, their own as well as those of others. The best of such individuals keep up to date on technological changes, new tools and techniques. These folks may not be inherently any smarter than you but they may be light years ahead of you in practical experience and application. Disdaining such hard earned knowledge is a waste of a valuable resource as far as I'm concerned.

One last point: some of the CF members who have given the best responses to your many inquiries are themselves professionals.

Jes' sayin'.....

[Chotu]

The bullet point here is:

*I’m not going to just outsource something without knowing how to do it first.

It’s really that simple.

Yes, thought experiments are an important part of figuring out the best solutions to problems. I’m sure most people would agree. You can always copy others, but I think it’s a lot more rewarding to develop original ideas.

I had started a thread to share the final parts of my build with the forum, but it devolved into someone personally attacking me and my boat. This is not a kind of stress I’m interested in adding to me life in the middle of a pandemic, running a small business and wrapping up a boat build. Those are enough without dealing with personal attacks online at the same time.

So I broke it back into a bunch of different threads asking questions. I was hoping to have the build thread work out, but I should have known as much. The internet is an amazing resource and an amazing liability at the same time.

Originally Posted by Nani Kai

Hey Chotu,

I have been following your questions, queries, proposed solutions and sometimes convoluted paths to an answer for some time now. Obviously you enjoy thought experiments and hopefully have benefited from the insight and experience of members of this forum. I for one would be very interested in seeing examples of your work so as to better appreciate the success of your experiments and trials.

I do find one thing very puzzling and that is your aversion to seeking or taking the advice of a pro. <quote: A “pro” is always just a regular person who was taught how to do some stuff. Anyone can do what they do. >

I would venture to say that everyone on this forum at one time or another has a pro horror story to tell. These stories typically center around wrong advice, incompetence, shoddy workmanship or even the occasional con job by folks calling themselves "pros".

At the same time there are lots of folks out there who know their stuff, have paid the price through education, experience and hard work and who have learned from mistakes and successes, their own as well as those of others. The best of such individuals keep up to date on technological changes, new tools and techniques. These folks may not be inherently any smarter than you but they may be light years ahead of you in practical experience and application. Disdaining such hard earned knowledge is a waste of a valuable resource as far as I'm concerned.

One last point: some of the CF members who have given the best responses to your many inquiries are themselves professionals.

Jes' sayin'.....

[zstine]

Originally Posted by waterman46

Unfortunately, Chotu's cat probably was not designed to handle the localized stress of a free-standing mast mount.

waterman, I completely agree that Chotu is probably not going to do the many needed structural changes to go fully unstayed since his boat is not built for it. And yes, you need to add a factor of safety for the overturning moment. I oversimplified..
The Sponberg calc is easy to follow. He used a FoS of 3.0 times max overturning moment to design the mast. In addition to the bending analysis, Chotu may find helpful the information about how Sponberg determines his carbon schedule and layup of the mast. Knowing Chotu is going to have a stayed mast, I sent another post with a link to a stayed mast analysis.

[Chotu]

I’m running into some issues:

1) carbon masts vary in thickness depending on localized loading. Thicker at the base, thicker at attachment points, etc. This is not compatible with the thread idea of using a carbon pultrusion.

2) Given #1, a great deal of modification would be needed to use a pultruded carbon/epoxy tube. All these modifications would be secondary bonds and done in epoxy. Since I can’t work with epoxy, I’d have to hire them out which would be cost prohibitive. Plus, these would be secondary bonds.

It seems there are some good reasons filament winding and prepreg is used to make carbon masts. Excepting, of course, this workable hand layup method:

https://teamvmg.weebly.com/mast-building.html

EDIT: Hang on a second! In reviewing the link above, I am noticing his laminate is biax/uni/uni/biax. All one thickness. No localized changes of thickness. Maybe the secondary bonds are ok after all??

[Happ]

Originally Posted by 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!

Why not just buy a system from Harken or Tides? They’ve engineered everything nd they are simple to install right out of the box. An afternoon project. Talk to your sailmaker so you know what it will take to modify your sails.

[zstine]

Originally Posted by Chotu

I’m running into some issues:

1) carbon masts vary in thickness depending on localized loading. Thicker at the base, thicker at attachment points, etc. This is not compatible with the thread idea of using a carbon pultrusion.

2) Given #1, a great deal of modification would be needed to use a pultruded carbon/epoxy tube. All these modifications would be secondary bonds and done in epoxy. Since I can’t work with epoxy, I’d have to hire them out which would be cost prohibitive. Plus, these would be secondary bonds.

It seems there are some good reasons filament winding and prepreg is used to make carbon masts. Excepting, of course, this workable hand layup method:

https://teamvmg.weebly.com/mast-building.html

EDIT: Hang on a second! In reviewing the link above, I am noticing his laminate is biax/uni/uni/biax. All one thickness. No localized changes of thickness. Maybe the secondary bonds are ok after all??

Sponberg was designing for a DIY at=home build. So his laminate schedule is carbon 'cloth', not filament windings. His laminate schedule is thicker at the bottom and progressively thinner b/c he is designing a free standing mast (no compression load save halyard tension) and bending moment decreases linearly to zero at the mast head. In a stayed mast, the section is going to be more evenly stressed and you can select a protrusion for the area with max stress. It will be overly strong, slightly heavier, perhaps compared to a custom wound mast, but that, I expect, would have minimal impact to overall weight.
You can certainly design for secondary bonding. As long as you know the bond strength you can design the joint large enough to spread the load. But in your condition, why bother? I have seen in the early days of carbon masts, Stainless plates with an array of rivets used to spread the load for fittings on carbon masts. An SS 'sleeve' can be used to spread spreader loads. Again, its just about designing for what you can do. You can solve fastener (rivet) tear-out and shear and use rivets and/or bolts to fasten sheaves, spreader mounts, etc to the mast... I think the mast head crane in the pictures you linked is a metallic weldment.? You can clearly see the use of traditional threaded fasteners and rivets in holding a pad eye and the halyard sheave boxes.. no/minimal need for secondary bonded fittings if you don't want to. How much does and extra 10-20 lbs really mean to you?

[john manning]

Chotu, my experience in this area is not great but for what its worth I think pultrusion is the wrong approach. The carbon fibre mast builders I know of all use hand laid carbon cloth, presoaked with resin, and then apply vacuum. A critical part of this is keeping the resin level to a minimum.

The cloth layup used is configured so that each layer applies its tension strength at a different angle which increases the stiffness of the mast. This is not going to happen by pultrusion.

My experience of pultrusion is that it is a resin rich product and its strength to weight ratio is well below that of hand laid vacuum impregnated reinforced plastic.

Regards wall thickness, I have seen masts and booms in construction but they were for very large yachts. The last boom I remember was an open tube about 8m long and 500mm wide. The wall thickness was at least 20mm.

External tracks are common on both aluminium and plastic masts.

[Ken Fry]

Originally Posted by Chotu

Moment of inertia only defines the shape of the mast. It does NOT define wall thickness.

I think what you are trying to communicate is second moment of inertia, often called areal moment of inertia. If is used for beam deflection and stress calculations. It does, in fact, take into account thickness AND the distribution of thickness, as well as "shape".

Engineering a composite section is no small task, because, unlike aluminium, carbon fiber constructions are rarely (almost never) anisotropic. A pultrusion is about the least anistropic material you can find. (Give a pultrusion a good thwacking and it splits like bamboo.) A pultrusion could be incorporated into a mast, but the mast would fail spectacularly if additional structure was not there to deal with hoop stresses. Given that 10:1 or greater differences in strength and stiffness are present in pultrusions (longitudinal vs transverse) treating the material like a stronger lighter version of aluminium would be a very huge mistake.

A composite mast must be engineered.

[Ken Fry]

Originally Posted by john manning

My experience of pultrusion is that it is a resin rich product and its strength to weight ratio is well below that of hand laid vacuum impregnated reinforced plastic.

This is, in general, dramatically untrue. Carbon fiber pultrusions can have very high fiber/resin ratios, and, because all the fibers are parallel, extremely high stiffness. They are used on many exotic structures when one wants properties unattainable by virtually any other method.

When I was building the wing spar and crossbeam structure of my Windrocket, I laid up and vacuum bagged some parts of the structure to aircraft standards, using epoxy and unidirectional carbon fiber. But where I wanted really exceptional strength and stiffness in a small space, I used carbon pultrusions, which could be roughly twice as strong as careful hand layup.

Some mass-produced fiberglass pultrusions are as you have described.

[Chotu]

Originally Posted by Ken Fry

This is, in general, dramatically untrue. Carbon fiber pultrusions can have very high fiber/resin ratios, and, because all the fibers are parallel, extremely high stiffness. They are used on many exotic structures when one wants properties unattainable by virtually any other method.

When I was building the wing spar and crossbeam structure of my Windrocket, I laid up and vacuum bagged some parts of the structure to aircraft standards, using epoxy and unidirectional carbon fiber. But where I wanted really exceptional strength and stiffness in a small space, I used carbon pultrusions, which could be roughly twice as strong as careful hand layup.

Some mass-produced fiberglass pultrusions are as you have described.

Exactly. It’s an amazing process and perfect for mast building.

BUT, I have yet to find a place that will do a custom carbon pultrusion

[Ken Fry]

Originally Posted by Chotu

Exactly. It’s an amazing process and perfect for mast building.

BUT, I have yet to find a place that will do a custom carbon pultrusion

You have completely misinterpreted what I wrote. Pultrusions are not perfect for mast building.

Pultrusions, when done with carbon fiber and done for very high strength and modulus, have, by there very nature, all the fibers running in the same direction. Properly used, the result can have very useful properties. Improperly applied, the properties can lead to disaster.

Because of the process of pultrusion, the fibers are even straighter than you can make them with a very careful hand layup of unidirectional carbon fiber. This results in unmatched strength and stiffness IN ONE DIRECTION. But for the same reason, these pultrusions have fabulously low strength and stiffness in the transverse direction. (So you can split a pultrusion in the same way the you can split dry cedar. A crack at the top of the mast will propagate to the bottom in a small fraction of a second.) For that reason, a pultrusion is not a good choice for a mast: it is the opposite of perfect.

Further, a pultrusion, by its nature, is of constant cross section, just like an aluminum extrusion. Therefore, the things we like to see in really nice masts, (justifying the hideously high cost of carbon fiber) such as taper, designed-in luff curve, engineered differences in stiffness from point to point, beautifully faired in local reinforcements, etc, etc, etc, etc, etc, etc, etc, are all not easy or efficiently accomplished with a pultrusion. (One can wrap the pultrusion to gain the necessary hoop strength, and then hand layup all the necessary reinforcements, etc, etc but in so doing, you are getting away from the fundamental nature of a pultrusion: polishing a turd... lipstick on a pig.

That is why people who do this for a living, and have spent the necessary time in engineering school, do not typically build masts from carbon fiber pultrusions.

Even carbon spinnaker poles, which are much simpler than masts, (and have much simpler loading patterns) are generally not pultruded, but are instead tape wound, fiber wound, braided, or even built of cloth... because even in such a simple application, a material that is closer to anisotropic works better.

Do you have Google? There are loads of places that do custom carbon fiber pultrusions. Call one of the many, and they will be able to explain some of the issues. Try Creative Pultrusions in Pennsylvania. They pultrude light poles, so work at mast scale.

If you are serious about a carbon fiber mast, then Van Dusen can make you a really excellent one. Custom Carbon Spars & Masts, Triaxial Braided Carbon Fiber

[Chotu]

Originally Posted by Ken Fry

You have completely misinterpreted what I wrote. Pultrusions are not perfect for mast building.

Pultrusions, when done with carbon fiber and done for very high strength and modulus, have, by there very nature, all the fibers running in the same direction. Properly used, the result can have very useful properties. Improperly applied, the properties can lead to disaster.

Because of the process of pultrusion, the fibers are even straighter than you can make them with a very careful hand layup of unidirectional carbon fiber. This results in unmatched strength and stiffness IN ONE DIRECTION. But for the same reason, these pultrusions have fabulously low strength and stiffness in the transverse direction. (So you can split a pultrusion in the same way the you can split dry cedar. A crack at the top of the mast will propagate to the bottom in a small fraction of a second.) For that reason, a pultrusion is not a good choice for a mast: it is the opposite of perfect.

Further, a pultrusion, by its nature, is of constant cross section, just like an aluminum extrusion. Therefore, the things we like to see in really nice masts, (justifying the hideously high cost of carbon fiber) such as taper, designed-in luff curve, engineered differences in stiffness from point to point, beautifully faired in local reinforcements, etc, etc, etc, etc, etc, etc, etc, are all not easy or efficiently accomplished with a pultrusion. (One can wrap the pultrusion to gain the necessary hoop strength, and then hand layup all the necessary reinforcements, etc, etc but in so doing, you are getting away from the fundamental nature of a pultrusion: polishing a turd... lipstick on a pig.

That is why people who do this for a living, and have spent the necessary time in engineering school, do not typically build masts from carbon fiber pultrusions.

Even carbon spinnaker poles, which are much simpler than masts, (and have much simpler loading patterns) are generally not pultruded, but are instead tape wound, fiber wound, braided, or even built of cloth... because even in such a simple application, a material that is closer to anisotropic works better.

Do you have Google? There are loads of places that do custom carbon fiber pultrusions. Call one of the many, and they will be able to explain some of the issues. Try Creative Pultrusions in Pennsylvania. They pultrude light poles, so work at mast scale.

If you are serious about a carbon fiber mast, then Van Dusen can make you a really excellent one. Custom Carbon Spars & Masts, Triaxial Braided Carbon Fiber

They can do the hoop windings on a pultrusion in some places now so yes, it can be done.