Carbon Heron Mast

[Nick B]

Hello heron sailors. In the interests of enabling an informed decision-making process with regards to future heron mast rule changes, may I present the following brief introduction to a carbon heron mast.

Background - I purchased some bare carbon (with some glass layers) tubes a few years ago in the interests of showing that a home builder could easily fabricate a cost effective and quality carbon mast. Impetus to finally put it together was discussions about future availability of current alloy masts. The tubes were purchased for about $400 incl GST; a  straight lower tube, are tapered tip, and tube for sail track. The tapered tip was inserted into the lower and glued in to form a single piece mast. Track was epoxy glued onto trailing edge. All the fittings were transferred over from a broken alloy mast (fatigue crack through a rivet hole in the tapered section at the hounds). It came in quite light (3kg), but also too soft (measured IE of about 7x10^9 N.mm^2). The track is too small for the thicker bolt ropes, but thin bolt ropes are fine.

The second iteration of tubes has been engineered for an IE value of 9.5x10^9 N.mm^2 (close to current alloy masts without the track) and quoted at $650 + GST. The second iteration is designed to be a spigoted mast that can be single piece or 2 piece (as the class sees fit, but I like the idea of two piece and other classes successfully do this). Track will be plastic rather than carbon tube. This price includes all the reinforcement flags/wraps which I had to put on the first mast. About 1m of twill at the bottom, a foot or so each side of the joint, a foot at the hounds and another foot or so at the head. Lengths are chosen to be less than 3m for shipping (something to also consider for the rules).

The laminate is a mixture of standard modulus carbon fibre and fibreglass, hand wound onto a mandrel in an effort to make cost effective tubes. These materials are not particularly exotic, unlike higher modulus carbon fibres. This also means the masts are not exceptionally light, which I believe is beneficial for the class.

It is likely as easy to make 6 side by side as it is to make 1. Trickiest part was gluing on the tube track. I can elaborate on this if requested. Hours are difficult to estimate as I didn't keep track and did a bit of faffing about figuring some techniques out. Two hours to glue the tubes together, 3-4 hours to attach and finish the track, standard hours to fit the mast.

Stainless steel against carbon is an issue. Only the forestay pulley and side-stay backing fittings are in direct contact with carbon, although have been liberally covered with tefgel. The fasteners are all stainless bolts or screws so can be readily removed and inspected or replaced, again coated with tefgel. The use of titanium fittings is being investigated and is not expected to add too much to the cost due to how few are required. Availability does not appear to be a major issue.

The mast has sailed twice only, once at SBSC and once at the single-handed worlds. It's been noted as soft, hence the lack of use. It will be at Lake Cootharaba this weekend for anyone to look at. It may make an appearance on the course, but I'll only use it for testing in club races personally. Despite being light, it appears sturdy. It may be prudent to paint the masts, rather than clear coat, for UV protection, but they don't spend huge hours in the sun.

Personally, I don't feel as though there are any major issues with adopting a sensible carbon mast rule change in the years to come. The tubes may be more expensive than equivalent alloy ones (make sure to compare apples with apples), but I believe there could be greater longevity from carbon masts due to reduced corrosion and fatigue issues. Hopefully this post demonstrates that this is well within the capabilities of a home builder. I won't be purchasing tubes for the second iteration but happy to discuss ways forward with interested parties.

cheers,

Nick

The Hopeful Heron

10169

(Photos to come)

[Nick B]

[Nick B]

[Nick B]

[Nick B]