Is my mast too heavy ???? - SailNet Community

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Old 04-21-2012
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Is my mast too heavy ????

Hello friends just joined sail net a few days ago.I have a bruce roberts design SPRAY 37.I am in the process of changing my 53 foot wooden mast to a alluminum one.The alluminum one is 165 pounds heavier ,do you think that is ok.I do not want to effect stability,but i do know the keel has an extra 1500 pounds of lead from original builder.thank you for all replies.
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Old 04-21-2012
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Re: Is my mast too heavy ????

On that boat I doubt it's going to be a major issue. That extra weight is distributed throughout the rig so it's not as if you'd be sailing around like you had an adult at the masthead on the old rig all the time.

If the boat's overballasted already it's unlikely you'll notice a huge difference - other than less varnishing or painting!
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Old 04-22-2012
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Re: Is my mast too heavy ????

I presume you are replacing your standing rigging at the same time. If you are really concerned about the extra weight, think about re-rigging using the new low-stretch line technology. It will save about that much weight aloft. Talk with your rigger about it. Of course, it does not last as long as stainless steel and is somewhat more expensive ...
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Old 04-22-2012
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Re: Is my mast too heavy ????

Thanks for the suggestion I haven't heard of low stretch line used as rigging before
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Re: Is my mast too heavy ????

Sure. These new rigging materials are made of Polybenzoxazole (PBO) or aramids (rather like Kevlar). They have almost no stretch but do have creep. Per pound, they are much stronger than stainless steel. Mostly, rigging using them is designed for the amount of creep they will experience over their lifetime since stretch is negligible. Racers have used this stuff for years, but the price has dropped sufficiently that it is appearing on some performance cruisers now. Gunboat uses it, for instance.

Here's a typical page from a company that uses PBO. As always, talk with your rigger and get expert advice.
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Old 04-22-2012
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Re: Is my mast too heavy ????

These high-tech lines are light but they do stretch considerably over time. I considered it when re-rigging but did not like the idea of a sharp edge being able to slice through my standing rigging. Also, I considered abrasion resistance and sun deterioration. I did use Amsteel for lifelines which has worked out fine but they are more or less static whereas standing rigging is constantly stress-cycled.
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Re: Is my mast too heavy ????

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Originally Posted by smurphny View Post
These high-tech lines are light but they do stretch considerably over time. I considered it when re-rigging but did not like the idea of a sharp edge being able to slice through my standing rigging. Also, I considered abrasion resistance and sun deterioration. I did use Amsteel for lifelines which has worked out fine but they are more or less static whereas standing rigging is constantly stress-cycled.
Hmm ... "quite a bit over time" is pretty fuzzy. It may mean something different to you than to me. The engineer in me much prefers numbers and equations.

The larger the fiber the less the creep. A rigger friend says the stuff is so strong that maximum rigging loading is on the order of 10% of breaking strength even when the stuff has degraded, which is why they design for creep (i.e. stretching over time with cycling). Normally they want creep to be just a few percent over the planned 10 year lifetime of the rigging. Here's a nice paper full of equations. Note the table on page 15. It shows creep under 1% for that particular fiber and size.

Will this stuff last 10 years? Well, it depends. Personally, I'd plan on 6 in FL, 8 - 10 in ME. As noted by others earlier, the big enemy is UV and abrasion, which is why the high strength material is used as a core around which is woven a cover that resists UV and abrasion. Regardless, it is susceptible to being sliced by a razor edge with repeated sawing, but it is harder to cut than you might think. You can tell when this stuff is getting close to replacement -- the cover becomes "fuzzy or hairy" with broken fibers sticking out.

I am no expert on these things, and certainly I'm not a rigger, but riggers frequent these boards -- anyone with some practical experience with this stuff care to comment?
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Re: Is my mast too heavy ????

The 3/8" Amsteel lifelines, approx. 30' in length, which I tension with lashing, over two years has stretched approx. 2", judging from the original length. Lifelines, of course have no where near the tension of a shroud or stay so a comparison is not possible. In any case, the 12 strand is very easy to splice a new eye into if necessary. It is mostly the ability to slice through it with a knife that bothers me when considering it for shrouds and stays. On the positive side, there is no variance in the end connection such as in poorly swaged eyes and forks. Once an eye splice is in, it is 100%. The specs. on swaged and swageless fitting are all over the place. I finally went with Suncor swageless for replacing standing rigging. I am going to rig up an inner stay and running backstays for a storm jib and WILL use high tech line for them.
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Re: Is my mast too heavy ????

The original question is in regard to a Roberts Spray 37.. putting PBO rigging on such a boat would be about the same as putting galvanized rigging and ratlines on a Pogo 12.50..
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Re: Is my mast too heavy ????

GRlEETINGS EARTHLINGS: Where on the boat is the bulkheads and is there lots of support to take the extra weight whether it be in compression post or in bulkheads you may need to ask someone to have a look for you as with that question you must be in some sort of quandry ? AS ALWAYS GO SAFE.
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