Simple question

[Renique]

What does it mean when a mast is "tappered" ?

Michel

[billknny]

Originally Posted by Renique

What does it mean when a mast is "tappered" ?

Michel

Michel,

A "tapered" mast is smaller in diameter at the top then at the bottom. Reducing weight to the top of the mast can help with performence a great deal.

Typically this is done by taking a standard mast section, and cutting out a long thin triangle from each side, squeezing the the edges back together and welding the seams.

Bill Kinney

[Brion Toss]

Hello,
I'll add that a taper works because compression loads "accumulate" on the way down; there's little inclination for the mast to flex up at the top, where the loads are just starting.
The highest inclinations to deflect are typically seen about a third of the way between the deck and the lower spreaders. So it is also possible to taper the lower part of the mast, and you can see just that in some older vessels, whose wooden masts might be tapered rather radically belowdecks. This could be especially valuable on a ketch, and rather than explain why, I think I'll make it next month's Puzzler.
Fair leads,
Brion Toss

[Renique]

Thanx for the info!

[Ian McColgin]

I was not aware of any way that compression strain accumulates lower in the mast. The effect of the mast's weight, yes, but that's trivial compared to the compression from the stays.

Many wooden sticks taper from the partners down to the heel as well as from the partners up. The lower taper, unlike the upper, is fairly even. Upper taper is usually minor until the top quarter or higher. Think of it as progressivly lighter topmasts.

Well made spars taper on the sides and front only, leaving a nice straight luff.

The mast takes less strain as it gets near the top - less force from the sailarea pulling it aside. Remember that the jib and stay are really compression. So the good reason for taper is to lighten the boat aloft. Most aluminum masts just don't lighten enough to justify the expense on that ground but aesthetics mater as well.

Unstayed masts are often tapered, whether wood, aluminum or graphite, to provide some air power controled bend.

G'luck

Ian

[Brion Toss]

Hi Ian,
It isn't just that the loads accumulate on the way down -- though they do, as more wires feed in their share of compression -- but that columns have specific reactions to compression over their length, and these reactions are modified by unsupported length, end fixity, wall thickness, radius, and column material. It's a wonderful subject, central to rigging. But rather than go into that now, I'll just point everyone over to the new Puzzler (it should be up by the 5th, I hope), for one aspect of the question.
Fair leads,
Brion

[Ian McColgin]

Got it. Can't imagine why I ignored mids and lowers!! Perhaps my mind was still on the question that arose from the catamaran or trimaran strut.

Thank you.