Mast stiffness

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colin brown
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Joined: Tue Aug 12, 2003 12:29 pm
Location: United Kingdom

Mast stiffness

Post by colin brown » Tue Sep 23, 2014 7:51 pm

Can anyone advise me on the effect of mast stiffness, if I change from a hog stepped mast with the gooseneck mounted about 400mm from its heel to a decked stepped mast ( on a USA stump?) with the boom mounted on that stump. Will the mast appear and react as if it was stiffer or remain the same?
What are the advantages to deck/stump stepping the mast? Some UK canoes just deck step the mast without the stump.Am I missing a trick here? Sensible replies please.

Colin Brown GBR 319 - SKY
colin brown

jimc
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Re: Mast stiffness

Post by jimc » Tue Sep 23, 2014 10:33 pm

I think I may have been first with the stump on an IC (first sail Feb 2008), but I used it in Cherubs previously having got the idea from Twelve Foot skiffs. The big advantage to my mind is that it completely eliminates mast bend caused by kicking strap loads pushing forward at the gooseneck (unless you have a push kicker of course). This means there are no lowers so the bottom of the mast can move a bit if you want it to - for absorbing luff round for instance.

In practice I have a mast which is stiffer below the spreaders than above with extra reinforcement from heel to spreaders and tapering off from there to the hounds, although I need to glue some more carbon on as its now too soft for my expanding waistline.

So if you move from hog stepped to a stump you will probably loose low down mast bend induced by the inward load from the kicker, to an extent determined by how much your lowers (if you have them) control it. Disadvantage is perhaps that with no lowers you have less adjustment potential for mast bend, and its more important that the tube is just right, which is why I really need to raise the enthusiasm to glue more carbon on my spar and get the bend just right for when I get a new one.

Another way of controlling mast bend of course is halyard locks or 2:1 halyards to take out compression loads.

Dreamcatcher
Posts: 262
Joined: Sun Dec 28, 2008 10:07 pm

Re: Mast stiffness

Post by Dreamcatcher » Wed Sep 24, 2014 6:20 pm

I thought that a hog stepped mast that is controlled tightly at deck level behaved stiffer than the same mast that was deck stepped. But I have been known to be wrong before! :lol:

Dreamcatcher
Posts: 262
Joined: Sun Dec 28, 2008 10:07 pm

Re: Mast stiffness

Post by Dreamcatcher » Wed Sep 24, 2014 6:21 pm

Also, the mast will behave stiffer with the compression loads removed......get a halyard lock!

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