cutting down a mast?

[tomdmx]

Hi All, I am about to purchase an older steel yacht (deck length 31.5 feet) which has a wooden mast...the mast is in ok condition (its single spreaders) however I have a mast and boom from a bruce roberts 39 which is in a much better condition and is double spreaders...its a bit taller so wondering if it is ok to cut down to size (about 3 feet) and what should I watch out for...

Any feedback is much appreciated. Thanks,

 

[merlin3688]

If the mast you are buying is from a 39' Roberts then it sounds big enough and also being double spreader helps. The boat you have purchased is it a one off or do you know the design, if the design is known we can compare the mast size that would have been fitted to the new one. If you want to PM me with this detail I may be able to help.

 

[dt4134]

You don't necessarily have to cut it down. You can always adjust your sail area by other means, e.g. reef earlier.

The thing to watch out for is rolling & pitching. The new mast will have a different moment of inertia so that may affect the roll period. Similarly your boat may have different characteristics. For example if you roll faster than the Roberts 39 you might be putting more load on the mast, spreaders and standing rigging than it was designed for.

 

[merlin3688]

You will also need to check spreader length and angles compared to the old mast. I have PM you.

 

[Scotty_Tradewind]

Even though it's a steel boat,
a) is the mast usually deck stepped?
b) does the mast support beneath the deck have a king post?
c) will the mast go through deck to be stepped on the keel?

A bigger mast could be a heavier mast, although having two sets of spreaders instead of one it may be a lighter mast.
If the mast is deck stepped ensure there is plenty of support in the deck structure and beneath to take a possibly heavier mast.
My Twister had a taller than usual mast. Very handy on a run but it did mean that I had to reef or spill wind off the main earlier especially as I had a fully battened main.
A larger than usual mast can also mean that with the sail abeem or in front of the mast i tended to have weather helm which was soon solved by reefing the main.
It's all doable if you wish though and probably not detrimental to speed.

 

[tomdmx]

Thanks all thats great help indeed! Both boats/masts are deck stepped with no further support below deck which makes me think that they are probably reasonably light?...in addition to the new mast I have the complement of sails..well for the main its a 3 point reef main plus stormsail

 

[William_H]

Larger mast

It is a conundrum as to whether to go for the bigger mast and sails or to cut them down. Much depends on the weather you typically experience where and when you sail. If there is a lot of light weather then the larger area will be good. If you get a good dose of force 3 and above then a larger sail area will be a pain as you will be reefing a lot. A smaller rig is far better than a reefed rig in strong winds.
You have not said if the original or the replacement are fractional rigged. I assume they are both mast head rig.
If you want to cut the mast down in size you need to consider the fittings on the mast. It is perhaps more convenient to cut the bottom off and move the gooseneck attachment up. However You should perhaps also cut the top down also to keep the spreaders in the approximate correct place. To move the spreaders will leave holes. I presume the new mast is aluminium not wood. So it may be lighter than the original wood which is good.
If the new mast was made for a fractional rig then it will almost be necessary to use it as a mast head rig. In which case chop the top off and have the forestay attached very near the top of the mast. You may need to fit an inner forestay to provide support for the middle of the mast. Also the spreaders may need to swung closer to abeam rather than swept back as in fractonal rig. For fractional rig the mast base will be further forward and the chain plates further aft than mast head rig. All these things need to be considered. All very complicated and critical. More info needed. good luck olewill

 

[Seajet]

I'd guestimate that 3' extra mast is about one reef's worth...as steel boats tend to be relatively heavy, I think I'd keep the mast in taller form to aid light airs performance & avoid messing around with fittings, and make sure to have easy efficient reefing ( ball bearing blocks are a godsend for this ) which of course is no bad thing anyway; might well require another reef row in the main.

 

[tomdmx]

From what I gathered here I think I would keep the new mast as is without cutting down to size as long as the spreaders are ok...both rigs are mast head tops, and both have inline spreaders (straight and at 90 deg to the mast), I haven't measured them yet but will do so...

In terms of reefing the new boom also offers roller boom reefing which I guess is a bonus as that tended to work for me in the past...

 

[Searush]

Is the boom length similar? Don't forget you can seriously unbalance the sail plan if the relative sail sizes are significantly different.

 

[William_H]

From what I gathered here I think I would keep the new mast as is without cutting down to size as long as the spreaders are ok...both rigs are mast head tops, and both have inline spreaders (straight and at 90 deg to the mast), I haven't measured them yet but will do so...

In terms of reefing the new boom also offers roller boom reefing which I guess is a bonus as that tended to work for me in the past...

Don't even think about roller reefing around the boom..... olewill

 

[tomdmx]

Really? (roller boom) Why is that?

 

[Tranona]

Really? (roller boom) Why is that?

Difficult to reef and leads to a poor sail shape. Can be improved by tapering the boom to take out the bagginess. Slab reefing now almost universal as it is easier to use and gives better sail shape. Roller boom does however have the advantage of giving infinitely variable reefing.

 

[Scotty_Tradewind]

Don't even think about roller reefing around the boom..... olewill

It's one of those things that if it's what you've got and you havn't the means to change to slab reefing, then you just get on with it and it works. (with its inherent slight disadvantages )

If you get really organised on the right boat, it can be quicker and easier than tieing off a slab.

I would try it and see if it works for you before panicking.

 

[tomdmx]

Hey All,

I've had some measurements done and the alu mast is 2m (or 6'6) longer than the wooden and is also almost twice as thick...which worries me somewhat, not sure why, probably because of its size...looking at the marina the smaller yacht although just over 31 feet in length has one of the shortest masts around (in comparable yachts)

So am thinking now that perhaps I should keep the wooden mast..it is in good condition overall, gooseneck needs improvement but thats it...is that silly of me to cross an ocean or two in a wooden mast?

The other thinking is to cross the atlantic and then look for a new more suitable mast there as its a lot cheaper (central america anyway)....

 

[AntarcticPilot]

Hey All,

I've had some measurements done and the alu mast is 2m (or 6'6) longer than the wooden and is also almost twice as thick...which worries me somewhat, not sure why, probably because of its size...looking at the marina the smaller yacht although just over 31 feet in length has one of the shortest masts around (in comparable yachts)

So am thinking now that perhaps I should keep the wooden mast..it is in good condition overall, gooseneck needs improvement but thats it...is that silly of me to cross an ocean or two in a wooden mast?

The other thinking is to cross the atlantic and then look for a new more suitable mast there as its a lot cheaper (central america anyway)....

Well, wooden masts were good enough for Nelson!

 

[tomdmx]

True but I think they were a wee bit thicker and bigger and then there is a whole issue of rig but I do agree.there was wood before alu and it seemed to do the job just fine...

 

[rivonia]

This is not an easy one to give advice on as there are too many IF's.

The mast height is also relevant to the lenght of boom. This also applies to spreader width's.

Another cosideration is the type of materiel themast is made of, as it bears a greater stress factor in relation to the height. Is the wood a different type to the existing mast?

Too many inpoderables here.

Get a good shipwright if you can (maybe one on here) to advise.

Good luck

Peter