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

Hi, I am building a small sailing dinghy with a lug rig. As you probably know, lug rig has massive forces on the halyard and downhaul, which, if attached to the mast partner, will pull it up while trying to pierce the mast through the bottom of the boat.

In order to avoid that, I think it would be smarter to have the halyard cleat and downhaul attachment eyes on the mast itself, since it will be in compression anyway. However, these hardpoints need to be just above the mast partner, which is the most loaded part of the mast, and drilling holes in a carbon spar is a very bad idea.

Can anyone suggest what are the simplest ways to add attachment hardpoints on a carbon mast? I am a bit reluctant to glue on steel hardware with epoxy and more carbon, because these materials have different thermal expansion rates and might delaminate come winter.

Since I'm building the mast myself (3D printed male mold/permanent core, with carbon sleeve on top), I have total freedom of the shape, I can embed steel/aluminum plates on the inside of the mast, or add some carbon fiber rods that go through the mast for bolts, etc., but I'm not sure if that would help anything, since I'd still need to drill holes in the mast skin to pass the bolts through.

Any suggestions?

 

I am definitely not an expert but have two boats with balanced lug rigs. FWIW one has wooden spars, the other aluminum.
IMO you are creating more complication than you would possibly solve. The step and partner are already robust enough to take the torque from the rig. Possibly the partner may benefit from a small vertical load consideration but that would be much, much simpler than adding hard points to the mast.
The lug rig's success is largely due to its simplicity. The only add on from its traditional form that I've experienced is a well thought out lazy jack system.

 

Well, in my case the mast partner is sort of like a bridge, there is no vertical reinforcement for it. Here is a picture from CAD:



As it is, it is probably not strong enough for vertical forces. Sure, I could design them in, but I think that would be a bigger complication than simply attaching high-load fittings onto the mast itself.

 

There are two things I wouldn't be keen to do;one is to use any mechanical fastenings in the main mast tube and the other is to mix materials as carbon and the usual marine metals are likely to be galvanically active.Is there any reason why you couldn't mould a pair of carbon sections approximating 80% of a semi-circle and with a flange of perhaps 30mm projecting from the edge in a line that would pass say 12mm from the central axis of the spar?They could be bonded in place and a shackle or clevis pin could pass through both,to which you could attach a Clamcleat CL253 or similar.Pass the halyard around the sheave and into the teeth of the cleat.Some local extra reinforcement on the lugs might be sensible.If I had more drawing ability I would have sketched something to convey the idea.

A capable knot tier might use a rolling hitch and a loop on the other end of a dyneema line to achieve the same outcome.Some study of the techniques that Moth sailors use with their carbon spars might be a good starting point.

 

Regardless of your drawing ability, I'm afraid I would have to ask you to sketch what you meant there... I am trying hard to visualize your idea, but I'm really struggling...

P.S. As for the rolling hitch, I had that idea (I could make some bump/hook feature on the mast so that the hitch has no chance to slide), and that would work for the downhaul, but the halyard clear still needs something a bit more sturdy to attach to, it can't be floating on a line...

P.P.S. Oh wait, I just googled that CL253, I thought I knew that model, but it's a different one. I see that this cleat is indeed supposed to be floating on a line... Expensive as heck, but damn, maybe this is a valid solution after all...

P.P.P.S. I tested a regular cleatclam that I had lying around... The natural position isn't perfect, it looks like it should slip out, but surprisingly it does not, it holds really well.



I suppose that CL253 would be far more suited for this use case and give a better (safer) angle, but even with this camcleat it does look like a solution...

 

Or, better yet, if the halyard were to be passed through like this...





Then it is super safe, probably just as good as that CL253... Damn, simple solutions are best solutions indeed

 

The partner-bridge on a sister ship of one of my boats.



Scroll down for more images. Take note of the lazy jacks.
17' Salish Voyager — Gig Harbor Boat Works

 

I spent a little time CAD modelling what I am attempting to convey and there should be a screenshot attached.I would suggest three plies of 200gsm carbon everywhere plus 4 or 5 further plies,each about 15mm less far around the mast that the preceding ply so that there is plenty of thickness for a clevis pin or a shackle and in view of my earlier comment about elecrolytic action,I would recommend not storing the metalwork in place if the boat is to be used in salt water.An abundant bond area should easily contain any loads without any holes for fasteners.They tend to be the starting point for spar breakages.

 

That is one beautiful boat, thank you for sharing. That mast partner indeed looks well reinforced for vertical loads, with these side flanges extending so far down. I could incorporate something similar into my design, but first I'll see if there is a simpler solution.

Thank you very much for taking the time to model this, it is most useful, I now see what you had in mind. This kind of arrangement makes a lot of sense. But have you seen the photos I posted a few posts above? Was that the alternative you had in mind? Because if so, then I could indeed get away with a rolling hitch around the mast to hold the clamcleat for the halyard, and a shackle for the downhaul. Or if the rolling hitch will slip, then I could glue on a small hook on the mast, and then just use a loop of dyneema instead of a rolling hitch to do the same thing. Wouldn't that be a simpler solution?

 

Thanks. The open area forward of the partner/arch is ugly, so I had the builder make a canvas dodger-cover for it. He didn't want to, but I threatened to make my own out of blue tarp and duct tape. His talented canvas guy saved the day.

I'm following your project with great interest!

 

A couple of points to keep in mind and a question;I would be extremely cautious about using a plastic Clamcleat for your purpose and under no circumstances would I pull any line through one.The reasons being that they are intended for holding a line after it's position has been adjusted and pulling the line through them wears the edges off the jaws and even using the metal equivalent leads to the same outcome.Then we arrive at the matter of ergonomics and friction.You need to make a decision on whether it is better to pull the halyard upwards or downwards when hoisting the sail and you then aim the cleat in the correct direction for efficient use.This may mean a turning block will be needed.

The CL253 has an integral sheave,but I'm not sure how well it would stand up to several metres of rope passing through it regularly as it was originally marketed as a method of adjusting the height of a trapezing crew.Something that used to be a bit of a fad and I have always found a height that just clears most of the waves and left things there,since getting dragged through a North Sea wave in April is nobody's idea of fun.I think I would find a way to secure both ends of the cleat so that the halyard could be released one handed and it could be something as simple as a line around the mast,if one end is secured.The principal load will be vertical and if the fixed end of the cleat can't rotate,a complex piece of hardware shouldn't be necessary.

One point that I haven't seen any coverage of is whether the halyard will be routed inside or outside the mast tube,what is the plan?

 

This is a fair point, but I suppose it boils down to technique, doesn't it? I mean, when raising the halyard, I don't need to pull the rope through the teeth of the clamcleat, I can pull it at an angle so that it clears the teeth (it is more convenient like this anyway), and then push it down into the teeth only when the sail is fully raised, so there will be no wear on the teeth. But yes, it would be more convenient to have that clamcleat stay vertical and not flail around too much, so I could use both hands to pull the halyard, rather than have to hold the clamcleat still with one. A secondary rope like you suggested would probably be good enough for this though.

For me, it seems that pulling halyard down would be more convenient than pulling it up. Several reasons:
1. I wouldn't have to pass the halyard through a sheave every time I rig the boat, saving little bit of time;
2. The hanging clamcleat could be attached low at the mast, probably near the partner, rather than hang down from higher up;
3. As the halyard exits the clamcleat, it would be naturally pointing down instead of up, which means it can't jump out of the clamcleat if someone accidentally tugs on it.

I suppose that purely from pulling perspective it would be more comfortable to pull up, but the ergonomics and safety seem to suggest that pulling down is a more sensible arrangement in this particular case.

As for routing, the halyard will be routed outside. The mast top will have a dumb sheave or a little block to reduce wear from the halyard, but other than passing through that sheave hole, the halyard will be outside the mast, as in traditional lug rigs.

 

Hi Laukejas, I'm no expert but I think what you are referring to as a cam cleat, is a V cleat; a cam cleat having one or two moving/rotating jaws that clamp the line via a spring and line tension, or via a lever and/or spring. I use simple double ended horn cleats for my balanced lug masts, (I have two masts to suit 2 different boats). The horn cleats are screwed into the wood masts opposite the side where the boom lays, 200 - 300mm up from the partner/deck. Since you are doing the layup yourself, once you have your mast wall thickness to your specification, you could simply add more layup over the base lugs of a horn cleat in its position, encapsulating it in the desired position without using fasteners, virtually molding it in place with a couple of thicker bands/collars of material, so it will never pull out. Black plastic/nylon marine horn cleats are tough, and can also be used to hold a shackle through the centre hole. The horn cleat is used for the uphaul. Downhaul going from the boom, or from a rope strung under the boom, to a saddle on the partner or deck, suitably reinforced for the stress of a pulley system. Just mold a reinforced bottom into the mast so it doesn't become a hole saw over time, and also make it so it doesn't rotate, and then bed it into a thick footing, with maybe a wood or rubber/plastic sacrificial base to take the down force, and any grinding movements. If your base is good, both uphaul and downhaul could be anchored to the partner/deck/other, avoiding point side loads on your mast. Try a wood or S/H aluminium mast first to get your positioning how it works for you best, then copy it in your high tech materials, and it will be right first time. Good luck; balanced lugs are easy to sail.

 

Thank you for suggestions! Hmm, perhaps molding a horn cleat into the mast is a viable option. I do have a few of these double-ended nylon horn cleats. Here is one that I might use (120mm / 4.7" long):



Epoxy doesn't stick to nylon too well, but I suppose if I rough it up enough and make sure carbon goes over the features of the horn, it should hold. As you can see the base of the horn has some draft to it, so it should be easy enough to bury that base in carbon fiber. Maybe even pass some carbon fiber through the hole of the cleat. ?And then perhaps that cleat could be used both for the halyard and the downhaul? Something like this:



Black is the cleat, green is the carbon mast (notice the wrapping around the horn cleat base), blue is the downhaul going to the boom, and yellow is the halyard. I could also add a small clip from the mast partner to the horn cleat to hold the mast in place for when the boat capsizes, but otherwise the boat structure would not be loaded, as all the compressive forces would be contained within the mast. Do you think this would work?

P.S. As for terminology, you are right, I meant "clamcleat" instead of "camcleat" there, a typo

EDIT: I modeled the embedding in CAD:



I imagine it being done something like this, thick fillets all around to wrap the base, lots of layers of carbon fiber, some tow passed through the hole and then wrapped around the mast, and then finally peel ply and vacuuming to make everything neat (I did a vacuum test on that cleat from the photo before - the bag has no problem getting into the undercuts of the cleat, so it should be fine).

 

Wondering out loud if fiberglass might handle the tight radius turns around the base of the cleat better than carbon?