Carbon Fiber, and lots of it!

I got involved with a project that has sidelined kayak building for a little while. The owner of Chesapeake Light Craft, John Harris, has been building a Proa over the past 18 months. He launched it last September and it has exceeded every expectation. He found room for improvement, on the rig, during his sea trials and thus the project started.

What was needed? Several items to make hoisting the Mainsail easier. Apparently, the loads generated are far beyond your average rig. We are adding a winch post to aid in the hoisting of both jibs, asymmetrical spinnaker and of course, the mainsail. We are also converting the main halyard to a 2:1 purchase, instead of the standard straight pull. This will reduce the loads on the individual components and place it on the entire mast structure, where it belongs. To do this, a "crane" has been constructed for the top of the mast, more info later. Rope clutches are also going to be mounted, to organize the halyards and allow for a single winch to be utilized. Since none of this is an off-the-shelf part, every piece will need to be constructed from scratch.

The mount bases/sleeves

All of these components need to be mounted to the mast. Mounting a flat part to a curved surface requires a considerable amount of fabrication. Since the mast is constructed from Carbon Fiber, great care is required when putting holes in it. They would all need to be reinforced. To start, a base needed to be molded to the surface of the mast. Four sleeves were formed using the mast as the plug.

To do this, plastic sheeting was draped tightly over the mast to keep the squeeze out from fusing the whole mess together. Layer after layer, of Carbon Fiber cloth was added. Each one was saturated with epoxy resin. The excess will be squeezed out when the foam press is applied. Once sufficient layers were built up, release fabric was next. Once saturated, a final layer of plastic. Now for the tricky part, smashing the whole mess to the mast without squirting it out on to the floor. 12 to 18 layers of cloth and epoxy are a slimy mess. I wrapped the sandwich with closed cell foam and used packing tape to apply pressure. The whole mess was allowed to cure overnight. It was a tense moment the following morning. Would it turn out well? Could the sleeves be fused to the mast prematurely? It all worked according to plan and the sleeves were coaxed off of the mast without much fuss. Theses sleeves will serve as the mounting bases for the winch, clutches and sheaves.



The Crane

Unobtainium- An extremely rare, costly or impossible material, or (less commonly) device needed to fulfill a given design for a given application. The properties of any particular unobtainum depend on it's intended use. For example, a pulley made of unobtainium, might be massless and frictionless; however, if used in a nuclear rocket, unobtainium would be light and strong at high temperatures. The concept of of unobtainium is often used flippantly or humorously. 

Unobtanium is the first thing that came into my mind when presented with the material, to be used for the winch pad and crane. It was a small plate of Carbon Fiber that was originally part of a now defunct military plane. How we got it is unclear. What I do know is, there's not enough to make even the smallest mistake. To help my nerves when cutting this, I made mock ups out of cardboard. This allowed me to check the alignment of the main halyard sheave and the fit in the top of the mast.

The plate of Unobtanium with the winch

The Cardboard Mock up. I will use this to mark and cut the Carbon plate.

The two halves of the crane structure

A close up of the crane material

A bushing installed to properly space the two halves.

Applying fillets with a dowel

A home made press fro squeezing out excess resin. A total of 6 layers of Carbon cloth were added to the Crane

One I cut the parts and checked the clearance of the sheave, I glued the structure together. Three webs were placed strategically, to create an " I beam" type of structure.Afterwards, it was layered with six more layers of carbon fiber and put into the "press". The unified structure was trimmed and sections boxed, for extreme rigidity. Once it is cleaned up I will post some pictures of it. Right now it is looking fairly rough.



Rope Clutch Mounting pads

The mounting pads were a multi-step construction. First was the sleeve, then the two halves of the mounting pad. It all has to be thick enough in order to bond nuts for the mechanical fasteners. Too thick and the clutches will stand too far off the mast, thus weakening the mount. It is a fine balance, and I had to constantly  remind myself that Carbon Fiber is nearly as strong as steel.

First layer of carbon cloth pressed into the form

A total of  nine layers of cloth placed in  multiple angles for maximum strength

The male plug to ensure solid construction

The finished mounting pad ready for trimming

Part A and B of the clutch bases

Home made carbon fiber kitty hair

Kitty hair mixed in the epoxy/cabosil slurry. Looks like a high tech fur ball

Bonding part A and B together

The finished mounting pad

Once part A and B had been molded, they had to be made into one structure. The bond had to be as strong as the two halves themselves. To accomplish this, I had saved strands of carbon fiber thread. These were cut up into  1/4" to 1/2" strands. Suspended in epoxy, I would make a solid mass of twisted Carbon Fiber strands. The mix of epoxy, Cabosil and Carbon fiber looked a lot like a hairball, wretched up by a cat. It was hateful to form and shape, but well worth it for strength. Once done, the pads sound like a a solid piece of metal when tapped on a solid surface. Drilling them was also a challenge. Our light drill press flexed when punching holes for the mounting screws. They are solid and will definitely not be the weak link.

The pattern for cutting the sleeve

Sleeve with pad locations, cut and ready for bonding

A trial fit, pretty good considering I had just received the clutches!

Bonding the three pieces into one. The carbon fiber is starting to show.

All of the pieces needed to come together, straight and neatly. Two reasons, to keep the stress in perfect alignment and to make it look like a manufactured part. I used the mounting screws for alignment and to hold the bonded nuts in place. The threads were waxed to keep epoxy from sticking to them. buried deeply within the pieces, are two 1/4-20 Stainless nuts. This will allow the clutches to be removed easily, if service is ever needed. Once all there pads are mounted, another three layers of carbon fiber will wrap this entire structure, With any luck, it will exceed the design specification of being able to hold 1000+ lbs.

My next update will be soon. Construction is rapidly advancing. Next week, the two other pads will be bonded, the part wrapped and the crane installed in the mast. This has to progress quickly, the boat is scheduled to appear at our annual builders festival on May 12th. Time is ticking!