Shortening Mast to remove base corrosion

eebygum

eebygum

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The nearly 40 year old mast base on my proctor mast (off Contessa 26) shows some corrosion and a lost rivot:

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The rest of the mast looks ok. I've read that it's possible to cut off a few cms, refix the base and shorten the standing rigging accordingly. Since I'm looking to replace the standing rigging anyway (it's 13years old) thats not an issue.

Is this job achievable by a competent DIY or strictly a riggers job (would it invalidate my insurance if I did it?) - if a riggers job how much would be reasonable ?

If I did it I was assuming:

- Cut off at 5 cms
- Clean
- Put in new drainage hole
- Trim base to fit
- Use Zinc paste and Monal rivets
- Order new standard rigging 5 cms shorter (I know this is not exact but on a 26fy boat that's not an issue)

I'm planning to do a lot more offshore sailing, is 5 cms less mast going to make any noticable difference, good or bad ?

Thanks in advice for your help.

Cheers
 
I'd cut off as little as necessary - shouldn't need to be more than 1-2cm.

Yes, lots of Zinc Cromate paste, and Monel rivets.

Other than tidying it up, you won't need to do any work to the base as the mast section is constant.
 
Can you have your mast foot extended or replaced with a slightly longer one to make up for the bit you cut off the mast .
Or maybe raise the mast cup that the foot fits into to keep rigging standard.
Pete
 
Yes you should have no problems shortening the mast. Note the boom will be 5cms lower unless you move the gooseneck fitting higher and then you may run out of track for the mainsail at the top. If you lower the boom then the boom vang may become less effective due to poorer angle of pull.
You will need to cut off at least the depth of the Al plug fitting as almost certainly it will not slide out. But you will be able to peel the mast metal off the plug. Hopefully it will be reusable.
Yes it is a fairly simple DIY job or at least by my estimations.
If you have to replace the mast foot fitting why not go the whole way and fit a hinging mast base so you can lower the mast yourself for mainntenance or bridges. good luck olewiill
 
There is no problem whatsoever in shortening the mast.
As has been said use plenty of zinc chromate.

Cut the mast back until you have a sound foundation to refix the heel.

Don't worry too much about how much you remove. As long as you know how much.

When you have sorted the mast, then remove the mast step and refit it with a hardwood spacer plate.

This plate should be the same thickness as the length which you removed from the mast.

I would use iroko for the plate. Easy enough to find and fairly rigid.

By doing this all your rigging will remain the same length and the boom will be at the same height.

If you decide against raising the mast step then do not move the gooseneck up or you may not be able to hoist your main fully and your genoa sheeting will have to be moved slightly foreward. In this case having the boom slightly lower would probably not cause any real problems.

Iain
 
Spot-on answer from Ian. I have shortened mine and also replaced the corroded alloy mast step with a home made Tufnol one, and some years & very many sea miles later, all is absolutely fine.

Consider a Tufnol spacer, that will require no maintenance (unlike wood).
 
Tufnol

Thanks for that fluff, I was feeling fine until you posted that, now I am going to die.

Yes, there is a very slight risk associated with Tufnol, but working outside in the fresh air with a P3 face mask on, makes this an acceptable risk exercise.
 
[ QUOTE ]
It's just a shame that you're not allowed to machine Tufnol anymore due to 'carsenogenic effects', apparantly...

[/ QUOTE ]And just where did you hear that rumour?. Please post a link to the definitive legislation.
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"Artificial intelligence is no match for natural stupidity"
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Re: Tufnol

Just a shame, as it's a fantastic material and those tufnol blocks made by the now-deceased (can't remember the name) company were really nice.
 
Standard Tufnol issued HSDA but I still cannot see where it says "that you're not allowed to machine Tufnol anymore" - There always was a dust "problem" working with Tufnol but fluffc's statement "It's just a shame that you're not allowed to machine Tufnol anymore due to 'carsenogenic effects', apparantly... " is news to me. It is more worrying as I am frequently in factories where machining of tufnol is carried out hence my desire for a definitive link to where fluffc picked up this info. /forums/images/graemlins/grin.gif Perhaps it is just a rumour as I cannot find any regulation prohibiting (not allowing) the machining of Tufnol.
--------------------
hammer.thumb.gif
"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>
 
Re: Tufnol

If you dont like Tufnol, because it might cause your legs to drop off if you machine it, it worth trying Delrin, which is slightly easier to work, but just a tough in compression as Tufnol. I buy mine from a local friendly engineering company as "Offcuts", and these are in nice metric thickness sheets, when they started. So if you chop off 50mm of mast, you have an almost ready 50mm spacer, out of the waste bin!
 
What this actually says is:

DUST: Machining causes dust. Inhalation of small quantities of dust need not be a cause for concern. Occupational exposure limits apply to the inhalation of all types of dust.

DUST: In the United Kingdom, no special exposure limit is assigned to this particular type of dust. Personal exposure to dust should be kept below both 10 mg/cu.m 8 hour TWA total inhalable dust and 4 mg/cu.m 8 hour TWA respirable dust. (Refer to HSE Guidance Note EH 40.) Different limits may apply elsewhere.

That's hardly a ban, more a reminder to take sensible precautions.
 
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