Mast-bend - setting-up & when sailing

Daydream believer said:
So apologies to the OP. Perhaps we should get back to his bent mast.
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Not at all , it's refreshing to have drifts which are entertaining and troll-free :encouragement:

I especially liked the bit about the Dunkirk Sands and the resulting mirth in the bar later - reminds me of dear old Benbecula "finding" the shallow bit in the middle of the Fal Estuary on Regatta Day.
The whole Regatta fleet sailed round us and later enquired if we had decided to take a breather................ :o
 
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Javelin said:
On a frac rig with diamonds as per your photos the mast will bend around the point of your steaming light.
The diamonds will hold the top section straight but from the lower hounds to the spreaders the mast is free to flex.

You set the mast up to suit the cut of the sail and conditions however on the customers yachts that have this setup I normally set the diamonds with a little negative prebend first, which is normally taken out with the weight of the boom/mainsail.
I found if you didn't do this the top section of mainsail would be too flat.
Often the top batten will be full length to induce camber but you don't have a lot of control over the top third other than leech tension/twist, when sailing.
Also when you take a reef in, due to the lower mast bent the top section can be very flat and if too much mast bend you will have issues keeping leach tension which will effect pointing and power.

Will all the rigs the best way to see what is happening is to sight up the mast track.
If you sight up and get someone to pull on the backstay, mainsheet, kicker and the cunningham you can see the effect of each.

Just had another look at your photos - its interesting that there is a sleave and mast join just below the center of mast bend.
Also, it might be due to the photo angle but it looks like the main spreaders are too flat and the ends need to be lifted by 3 or 4" to better bisect the cap shroud angle.
If you find you have issues reducing forestay sag you might find adding a set of running back stays would help.
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Hi Javalin ,
Thank you for your advice much appreciated. we could do with a thank you Tab on the forum.

Steveeasy

S
 
An update:
My mast is lying across three trestles about three feet above ground; one each end and one a third up from the foot.
I jacked-up the top trestle by about fifteen centimetres and at the cross-tree point hung a 80kg weight (me!)
As far as I could see there was no deflection whatsoever.

Does the team think 80kg at the cross-tree point would equate to anything like a good winding-up of the backstay?
Or is my mast so tough it will not significantly bend whatever the force?
 
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If your rig is correctly set up for a masthead rig at 15% of the breaking strain of the wire, then 80Kg is a light weight. Not sure of your rigging size so these are the most likely sizes.
5mm 1x19 breaking strain is 2100Kg so 15% is 315Kg.
6mm 1x19 breaking strain is 3030Kg so 15% is 455Kg.
So under load on the wind, the rig will be exerting a greater load than 15%. So, hence 80Kg is a light weight.

The design of the mast section will certainly be stiff, but still can be bent with a high loading. Your keel stepped mast has the additional possibility of stiffening it by chocking it at deck level.

Being a keel stepped mast, what would concern me more is where the exits for internal halyards are on the mast as these substantially weaken the mast section. How do I know? My parent's race boat lost a mast due to a manufacturing error where exit slots on the sides of the mast should have had a 12" solid section between the bottom of the upper one and the top of the lower one on the opposite side of the mast. The end result was the mast folded across the faulty section in about 18 knots true wind speed, so the mast was replaced by the manufacturer for free.
 
Ahhhhh. Good news/bad news.

Good news: I'm referred to as a lightweight at 80kg :)
Bad news: Only 7" between top/bottom on opposing sides :(

Backstay and Cap-shrouds 7mm. Forestay and Lowers 6mm.

As far as I know the mast is the original late 1970s design and supply (first used 1982).

Rigging about 10 years old - so probably time to renew. Ouch! :(:(:(
 
You don't have raked spreaders so rig tension on caps and lowers should be set at 10% and not 15% break strain, even so your 80kg is light.
The angle on the fore stay and backstay is a lot larger than the caps and lowers so the static tension required is a lot less.

For the new wires I would expect a bill in the region of £1500, including the often forgotten forestay.
 
Javelin said:
For the new wires I would expect a bill in the region of £1500, including the often forgotten forestay.
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If that cost is for mast crane out/professional riggers/mast back in and tune up than maybe the price is about right. OK it was 5 years ago and a slightly smaller boat but I had new rigging and Stalok chromed bronze turnbuckles made and self fitted for closer to £600. That included a rigger to take apart a seized up Rotostay and replacement forestay.
 
Robert Wilson said:
I was thinking that at the end of this season, after haul-out and mast removal I would send all my rigging away to be copied. Is this the most practical way to "re-rig" or is it necessary for the rigger to "come to site" ?
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That is exactly how I did mine. I got several quotes and delivered the wires to the rigger. I did need a specialist to come on site to remove the old and insert a new forestay for the roller reefing, I was unable to get the thing apart and the rigger had the requisite tools.
Incidentally, if you remove the mast every year, get one of those cheap digital callipers. Get the rig set up as you want it. With the callipers measure the distance between the two ends of the turnbuckle pins and make a note of them. Next season you can go straight back to the last season's settings without having to re-tune. I've been doing that for many years now and it saves a lot of messing.
 
Just one caveat... I replaced Gladys mast a few years back, and so the "send the old rigging off" wasn't an option. And I was glad, because the old mast had been rigged with a lot of aft rake, and the boat was transformed when rigged with the mast "plumbish" (i.e. out of the book masthead starting point). Copying the rigging you may be maintaining an error from years ago... Just a thought...
 
alahol2 said:
Incidentally, if you remove the mast every year, get one of those cheap digital callipers. Get the rig set up as you want it. With the callipers measure the distance between the two ends of the turnbuckle pins and make a note of them.
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Or you could do what I do and simply wrap a piece of insulating tape around the thread at the point it meets the turnbuckle.
 
Triassic said:
Or you could do what I do and simply wrap a piece of insulating tape around the thread at the point it meets the turnbuckle.
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Always used to do it that way but frequently forgot to replace tape at the end of the season so got left with scrappy tape or found the tape had fallen off. Also relies on getting the same number of 'starter' turns on the turnbuckle as the previous year.
I just find the callipers easier and more accurate, I'm not evangelical about it:).
 
Javelin said:
Looking at the pickies of the Javelin it appears they have a single set of spreaders, forward and aft lowers.
You also mention its keel stepped.
Based on that the rig is a set up and forget.
Saying that it assumes you have the correct rake set, fixed by the lowers.
Adjusting the rake will effect the amount of weather helm for instance.

Moving onto the backstay.
On your rig the above comments are correct that the main effect will be on forestay sag, especially when reefed.
When sailing with a full main upwind the mainsheet tension will assist on forestay sag, given the boom is close to centreline.

My lowers are in the same line as the caps so backstay tension will bend the mast forward flattening the mainsail.
Your rig however has fore and aft lowers so extra tension on the backstay has little, if any effect on mast bend, it will just increase compression.

Be sparing with grease on turnbuckles as grease will tend to pick up grit and dirt with a risk of causing exactly what you were trying to avoid.
Also please don't cover them with tape or plastic covers as moisture and dirt will work its way in.
Far better to leave them uncovered and allow the sea and rain to wash them, plus you can see and inspect them easily.

Same goes for spreader end caps. I've condemned two lots of rigging this year alone due to stainless/alloy corrosion caused in part by these plastic spreader end caps.
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I thought the role of tape was to protect the sheets from the ends of the the split pins inside the bottle screw. Am I wrong?
However I was instructed not to tape so as to close the cavity so letting water get out

TudorSailor
 
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