SAILBONE® battens bow-formula technology was developed for maxi yachts and high tech ocean racing cats. The problem was simply to develop a tapered batten that was light, incredibly strong over long lengths, built in a predetermined custom flex curve to accommodate optimum performance over various wind speeds. The solution took years to develop.

The technology that led to the development of SAILBONE® originated in the late 1950's by Walter Kramer. While making archery equipment, bows in particular, it was realized that this hightensile glass fibre held together with a specially formulated resin laminated with light and strong core materials was the answer.

WHY IS SAILBONE® RECTANGULAR?

Oval, round or l-beam shapes have excellent value, but not for bows and springs. Continuous stress applied on a small number of load bearing fibres leads to early breakdown. SAILBONE® chooses the largest number of filaments to bear the load, and surrounds its spacer core completely with continuous filaments longitudinally, thus achieves the strongest life force with the minimum material usage. It is this type of structure which lends itself to easy tillering, tuning or calibration to produce matched sets of SAILBONE®.

Tension diagram

WHY DOES SAILBONE® NOT USE CARBON FIBRE OR KEVLAR?

It's simple. SAILBONE® is built to flex and flexing is accomplished by two opposing forces; tension and compression, and a core that keeps those forces from meeting up with each other. We have established that there is no measurable elongation or compression possible with carbon fibre or kevlar. Therefore, to make it work, elongation and compression is only possible with carbon or kevlar by it's arrangement of fibers, namely in woven form to be compared with a corrugated fibre, or introducing an elastic factor in it's core. This is not a reliable principle. Carbon and kevlar is ideal for shapes not intended to flex if used in it's most effective fibre-lay, namely straight filaments. Experience has proven this point to a number of my clients. Several have had to pay a high price to learn that.

WHY IS SAILBONE® NOT USING FOAM CORES?

When foam first became available I was very excited and brought in all types of urethane and other types of foam and started mixing in various densities - from 2 lbs. to the cubic foot to 20 lbs. I made it so strong that you couldn't drive a hardened screw into it without breaking the screw. I also tried a large variety of wood and found the following. When testing for break resistance and stability, only a fairly high density of foam stood up to the break tests, while the wood known as 'Obeche', a Louisiana swamp willow, and our northern Butternut, came out on the top for overall performance in weight, stability, bendability and break resistance. This coupled with grooves has served best over many years and most extreme applications.

WHY IS SAILBONE® SLIGHTLY HEAVIER THAN EQUIVALENT FIBRE & FOAM CORE COMBINATIONS?

The weight of a batten is a trade off between break resistance or it's weight. By varying the number of glass filaments and core material ratio, SAILBONE® can be made as light or lighter than equivalent weight to stiffness ratios in exotic structures. It is a question of how soon do you want your battens to break?

WHAT IS THE BEST WAY TO ATTACH BATTENS TO THE MAST?

Which ever way works best for what ever you try to accomplish. Many people have many solutions. Principally a batten should be:

Able to slide up and down a track over positive and negative curvature.

It should be firmly rooted at a hinge point (split battens are a different problem, the whole mast becomes a hinge point).
SAILBONE® should swivel to allow sail and batten to flake and stack easily without forcing a twist into the batten while stored in a sail on the boom.
Webbing is light in weight but it is limited in its performance.
So far we have a sliding hinge that swivels. How do we fasten that to the sail and to the batten? One easy method is a nylon shoe riveted or bolted just behind the guide rope. A new commercially available, the SAILBONE® boot is now being manufactured by Schaefer Marine. More information — Click here.