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Adrian_Morgan
15-11-02, 20:47
Which would be lighter: a 24ft hollow tapered spruce mast or a tapered aluminium mast of the same diameter (about 4 inches). Both would need to be of adequate strength of course. Some science please.

I want to go wood, but aluminium seems to have the edge in every respect.

Jacket
15-11-02, 21:06
Metal, else the racing boats would still be using wood.
Having said that, I don't think there's that much in it, as you still see competative folkboats with wooden masts.

ianwright
16-11-02, 12:08
Eh? Aluminium is lighter, carbon fiber lighter still. Why? What for? Sally 2 with a metal mast? Forget it. A nice hollow stick with double spreader rig please,,,,,, unless you were thinking about gaff rig? Good solid spruce in that case.
But you know that,,,,,,,,,,,,,,,, :)

IanW.

Vertue 203, Patience

jamesjermain
18-11-02, 12:10
Surely its gopt to be wood, Adrian - and solid and heavy too. Didn't you say that Sally has been trimmed by the stern ever since she was launched? Wouldn't a light, (and incongruous) metal mast exacerbate the situation?

JJ

Gordonmc
18-11-02, 13:28
Excuse the pun... we are in the same boat.
My Hillyard has a black anodised ali mast which is in good condition... but looks wrong. Compounding things is the timber boom which has a noticable twist.
I have been looking around for a suitable hollow wooden mast (9.4 metres) but so far I have only seen solid spruce. I prefer to go hollow because the mast is deck-stepped.
The mast is off at the moment for re-rigging and if I cant find anything suitable in the coming weeks I will put the ali one back on. Reluctance is overcome by relief from the threat to the wallet.
Where are you? I can give detail of the solid masts if you want more info.

Adrian_Morgan
18-11-02, 13:50
To clear things up re Sally. This is for a double ender I've just finished building up here at Ullapool Boat Builders. Long story. (Norwegian designer replica of original built in 1934). She's a centreboarder and has precious little initial stability. Sloop rig (that's the original rig, so don't persuade me to go gaff) thus needs to be as light as a feather. Something Uffa Fox may have built for a 14 in the 30s. But where to get such a thing? Got to be hollow, of course. And spruce (the lightest to be found). Clunky solid masts would be no problem. Even I could make one of those. This has to be high tech wood, and with an accurate idea of the finished weight. So; could I get one to weigh the 18 lbs I have been quoted for by Selden for a similar section. 3.75in diameter tapering.

That would mean some lb/cuft spruce calculations.

Any experts out there tell me what a hollow 24ft mast would weigh (without falling down).

Twister_Ken
18-11-02, 14:11
No help on weight of a timber spar I'm afraid, but if you wanted to go really light, how about laminating carbon fibre to the inside of thin spruce sections to beef up strength at minimal cost in weight?

<P ID="edit"><FONT SIZE=-1>Edited by Twister_Ken on 18/11/2002 14:12 (server time).</FONT></P>

Adrian_Morgan
18-11-02, 15:11
Ah, yes. Maybe. But building a hollow spruce spar would be hard enough without laminating carbon fibres onto the inside of each section. Do you mean carbon reinforced cloth of some sort? Or actual inidirectional fibres? The expense would be formidable and the calculations required to get the right mix complex. Are you serious? Much easier to wood veneer over a carbon tube, surely.

Thanks anyway. But there must be someone out there who's made or had to replace a hollow spruce spar for, say, an International 14 or Flying 15 and knows what weight it came out at and/or how much an aluminium one differed.

Twister_Ken
18-11-02, 15:15
&gt;Much easier to wood veneer over a carbon tube, surely.&lt;

Now you're talking! And you could make it unstayed as well to save more weight aloft

Adrian_Morgan
18-11-02, 15:23
Have put in a call to Carbospars. Will report back...

Jacket
18-11-02, 18:36
Why not talk to some of the companies who make wooden masts for classic racers? They must (hopefully) know about these things. The only company I know off the top of my head is:

http://www.matsbat.com/information.html

They're Swedish but were very helpfull when I phoned them a few years ago. But there must be similar in the UK given the number of Classic rebuilds going on. (Isn't there a british company called something like Collars who do masts for Folkboats and advertise in Classic boat most months?)

vyv_cox
19-11-02, 08:18
When Rodney Pattisson won his Olympic Gold, he had the option of either a wood or metal mast. He chose wood, on the basis that it would be lighter. However, in order to achieve this he travelled to some exotic place, forget where, personally chose the most knot-free tree available, supervised its felling, bark-stripping, storing, and ultimately its machining into a mast. Must have cost a fortune to save a few grams. But that's Olympic sailing.

For the majority of us, choosing a wooden mast inevitably means going slightly heavier to overcome the imperfections that nature incorporated into the base material.

Jaguar
20-11-02, 13:19
From an engineering point of view, aluminium is the better material. Its strength is over 3 to 4 times that of wood (2-300 MPa vs 80 MPa). It is also very tough and longer lasting. More importantly, aluminium is in the form of a tube, which is where the material does most good. From a buckling resistance and strength point of view, material in or near the centre is wasted.

JJ