Easiest way of making attachment hardpoints on a carbon fiber mast?

Check out your nautical supplier and see if there is a horn cleat with longer toes. Mine seem to have longer base flanges than your example, giving a bigger/longer load bearing area and less chance to pull out. They are cheap rough moldings from the land of instant landfill. I never believed epoxy would stick to it, even with surface treatment, but being buried in a couple of bands would make them immovable. I have no idea of expansion coefficient differences. Your cad pic example of a blister would pull out, or deform one side I think, but a complete band top and bottom would spread the loads and reinforce, and probably be easier to do. Your cleat pictured could have the nice tapered base filed to a reverse angle, or a tread pattern , to lock them in. Going through the middle gap would add little strength regarding the leverage and pull axial to the mast, but may add strength for sideways knocks.
This is my cleat, nearly 6" / 150mm across the horns. I've never had one break unless already badly damaged. The attachment method is the weak point. I use undersized screws so I can increase screw size later if I really have to. I also rasp/file the underside concave to fit the mast more snugly, to spread loads and give support.

 

Thank you, that is some very good advice! Yeah, the way I drew it in CAD is just for visual reference, of course I would try to make these reinforcements as thick as possible. And yeah, while the cleat I have does have negative angle, the base could be wider. I'll try to find one with a wider base. One of my local suppliers has this cleat (Plastic cleat, white https://boatshop.lt/en/yacht-equipment/1050-plastic-cleat-white.html), I think it has a more suitable geometry.

Do you have any pictures of how you added fiberglass/carbon bands to your cleats?

 

No pics because I didn't do it myself, it was just a suggestion. If I did, I would look for carbon fibre tape maybe 25mm wide or a bit more for the first wrappings to get about 5-6mm, 1/4" thick bands, maybe a bit less, then some wider on top to give a nice finish and spread loads. Your white cleat looks like my black one, so it could work. Maybe a composites expert on here could give some advice about your mast fittings, and how to go about it. I only have ideas, not experience with carbon fibre.

 

I just dipped into this thread after a couple of days and I am quite surprised you don't recognise a Clamcleat.They have been around for almost sixty years and are simple,with no moving parts.They also have the virtue of no . or corners that might snag things.I use a side entry racing junior version for my main halyard- CL218 Mk1AN and the hard anodising lasts well Cam cleats are a different thing altogether and wouldn't be my choice for a halyard cleat.

 

Clamcleats are also known as jamcleats.

 

While this is true,the registered trademark and company name describes a particular piece of hardware.A traditional horn cleat can function as a jamb cleat as can a cam cleat.Using the correct term makes it harder to confuse matters,a well established nautical tradition.

 

Enough of the jam-clam pissing match.
Will glass fiber be better than carbon fiber wrapped around the cleat base??

 

If you already have a quantity of carbon on hand,why would you introduce a different material?Sticking with the same material avoids any issues with differential expansion weakening the joint over time and I realise it might take several years of extreme temperature changes for anything bad to occur but why run the risk?It isn't highly likely that there won't be some small amount of surplus carbon from the mast making process.I do foresee some practical challenges in getting the fibres-of any type-to conform to the shapes.

Since out enquirer has the ability to 3D print items,as we have seen on his rudder thread,it might not be a big challenge for him to print a mould for a mounting pad.It could feature a flat base for the cleat to attach to,with an embedded metal pad for tapping to receive the cleat fasteners.the mounting pad itself could be bonded to the mast.To guarantee that the fibres conform,he could print a pressure pad that is offset by a material thickness and clamp or weight it down until the cure has taken place.

 

I've been using cam cleats (note the separated words - not a brand name), and V cleats, and horn cleats for nearly 60 years myself, and also have seen clam cleats, and foot ware cleats. Most rope cleats could be termed jam cleats, since their main purpose is to hold / grip a line or rope, and many jam the line, eg. via a V, or via squeezing cams, (cam shaped swiveling opposing cams), or via a clamp (possibly operated by a cam or two against a squeezing plate crushing the line).
Maybe local word usage, and the accuracy of the sales descriptions and pics seen, comes into play here. Seen sales brochures and web sites lately, produced by folks who can't spell, or don't understand the items displayed ?
Rotating cams jam; V's and multiple V's jam; clamps jam; guitarists jam, and I like jam on toast. But doors jamb ? Whatever - , a horn cleat could do the task in question, along with many other options.
As I said. "I'm no expert . . ." The O.P. wants "cleat" suggestions, and related information.
Who knows about carbon fibre layups with hardware inclusions, and can assist ?
3D printed removable formers/molds could make it a neatly finished job, maybe, I don't know. Using surplus C/F seems a good idea.

 

Why not make a carbon fiber cleat?

 

All that you guys suggested here can definitely be done... It's just like I said, I'm looking for the simplest and foolproof solution that will work. So far, it seems that a hook feature on the mast + hanging clam cleat, OR plastic horn cleat glued onto the surface of the mast with lots of carbon wrapping on top, seem to be the simplest options. Molding anything from carbon, or introducing metal plates would complicate things or risk delamination unnecessarily... After all, all that I need here, really, is just a way to attach a piece of a rope at a designated location to the mast, without weakening it, that's all. I can make it work from there. I'll probably go with a horn cleat, since it both provides a hole for a rope, and a convenient way of tying off the halyard. And if floating clam cleat turns out more convenient than horn cleat, I can always cut off the horns, leaving just a loop of plastic attached to the mast... Although I don't see why not just leave it there, just in case

 

Shall we begin with the difficulty of persuading the fibres to conform to the tight curvature?A large horn cleat might have a generous enough corner radius to permit such a venture,but why would you seek to do it,other than proving a point?An off the shelf plastic cleat would secure the halyard,but I have to admit to not using any traditional pattern cleat on a racing dinghy since about 1980 as the alternatives are considerably more compact.As I posted earlier,a carbon base to fit the mast tube and provide a suitable insert for tapping wouldn't be too difficult to make and sufficient bond area wouldn't be hard to achieve.

 

I think it would be in line with someone making his own carbon fiber mast. There is less curvature than in the mast section.

 

That would be a metal hoop with welded cleats, epoxied in place.

 

Yes, except the issue of dissimilar materials (metal VS carbon composite), and their potential for delamination and electrolytic action. Also, making such a hoop is not so easy when I don't have a metal workshop... Epoxying plastic cleats directly to the mast with carbon on top seems a lot simpler, unless I'm missing something