Polymer Mast

[eddyb]

Hi,

I am in the process of doing a university project on manufacturing a yatch mast from a polymer.

Unfortunatley I do not know much about boats.

The task that I have do complete is to suggest a possible polymer that a mast could be made out of for a yacht that is to sail around the world.

What would be the key service conditions that the polymer would face and therefore what porterties would it require?

I am asked to short list three possible polymers that would be suitable and suggest manufacturing techniques.

Can anyone help me with the project or suggest some recommended reading ar possible sources?

I look forward to hearing any information you may have.

Thanks.

A mast with stays is under a great deal of compression . It needs to be stiff ie not bend easily because buckling wll cause it to break .

Carbon fibre in an epoxy matrix is the only major choice here .
Often the front half and back half of the section are made in female moulds and then bonded together along their length

[Polarity]

That does not of course rule out unstayed masts - where the flexibility would assist with the twist required to account for windshear.

To attempt to answer your question though it would have to be lighter than aluminium and preferably lighter than carbon fiber - or else why bother - for the same strength. (and I use the term strength loosley!) as well as being able to be formed into a shape that will provide the required stiffness. The smaller that shape in cross sectional area the better the aerodynamics of course,

If you want it to "sail around the world" then it must be temerature stable from say -20 deg C to +50 deg C (more if it is a dark colour!), not deteriorate with UV (or be capable of being coated to resist UV), non electrically conductive would be usefull, capable of point loading (a carbon fiber difficulty I understand) for mounting of winches, cleats, the boom etc), non reactive with hot or cold salt water, hot or cold fresh water, hot or cold mild acids or alkalies. Non-work hardening.

Thats what springs to mind for the moment...

Paul

[Polarity]

In fact while I think about it, the only reason we have all that rigging is because at the moment there is not a viable material that will stand up without it! - The load spreading could be organised through the mast partners and connection to the keel. The forestay could be a rigid strut with a section that could change length (hyraulicaly for example) to move the mast head if required. How about a polymer that went from semi flexible to rigid with application of a small electric current?

Paul

[gonzo]

Bill Tritt designed and build many succesful fiberglass spars starting in 1946. His first design was called "Green Dolphin". I have built and sailed with masts built of many materials. They all work fine if the characteristics of the material are taken into account. For example, a Cheasapeake sharpie of 34' lenght will have and unstayed mast of pine. It is actually a tree with the branches cut off. I owned one for a couple of years and never had a problem. An unstayed mast has less compressive loads, however it needs to be flexible enough to depower when the wind increases. Masts, like any piece of equipment, will fail if overstressed. Polyester resin and fiberglass are adequate for spar construction,however, carbon fiber and kevlar can make a lighter structure.