Mast Panting

[richardbrennan]

I have a problem with mast panting on my Westerly Ocean 33 when beating to windward in winds of twenty knots and more when I have a couple of reefs in the main and six or so rolls in the genoa. This is a known issue on these boats and the rig is notoriously difficult to set up. I have now had two riggers look at the problem and the rake of the mast has been reduced and various other adjustments made to the rig and this has improved but not eliminated the problem. What caused this problem to appear is a worry; the only thing that has changed on the boat is that I had a new mainsail at the start of the season which is heavier than the one it replaced. It is a heavier cloth and has an additional batten, is it likely that the new sail iscontributing to or causing the problem?

 

[npf1]

have you though about fitting a jumper stay?

 

[sarabande]

Tightness in a few area could be contributing to this.

is the main cut tight on the leech ? When you bring in the mainsheet, that might contribute to forward pressure at the gooseneck, and aft pressure at the mast head. Can you flatten the cunningham to move the draft aft ?

IIRC both upper and lower spreaders are swept back on the 7/8 rig, so their shrouds could be too tight. Baby stay also tight ? And the back stay.

 

[30boat]

My Fulmar hada a thin section mast albeit with thick mast walls.It was too flexible and panted too much when beating to windward.After a number of years I had to fit checkstays which entirely cured the problem.They were a nuisance but the rig became much better supported.I've since replaced the mast with a lighter but wider section spar that has almost no movement under the same circumstances.My rig is a 3/4 can't remember exactly how your rig is.

 

[[2574]]

Had a similar problem, rigger advised (running) checkstays, which solved the problem. Turns out that Selden specified the rig with checkstays but an earlier owner had removed them.

 

[richardbrennan]

The rig is fractional but more like 19/20ths than that on a Fulmar and I have not seen another Ocean 33 with checkstays, which I assume are the same as running backstays, or with jumper stays

I am interested in the comments from sarabande as the only variable is the new main sail and it does seem to me that the boom is higher with the new sail which would match up with a tighter leach. It was also interesting that when I initially test sailed after the first rigger made his adjustments, I initially forgot to slacken off the topping lift and did not have the panting. Once I took the tension off the topping lift the panting started again. I do not usually use the cunningham but will try it and see if this improves things.

Many thanks for the comments

 

[richardbrennan]

Dear Sarabande

I have just realised that the cunningham will not be the key to tracking down the problem as it only manifests in stronger winds and punching into the famous "Solent Chop". However I assume if the leech is tight it would be equally problematical, perhaps more so, when reefed?

 

[TimBennet]

Is the additional batten full length at the top? If so, this will exacerbate the pumping especially when reefed at it will transfer the weight of the sail more directly to the mast.

From the pictures I can see on the internet, there doesn't appear to be much aft sweep on the spreaders on the Ocean 33, which is the only design aspect that gives your fore and aft bracing to your mast. Usually more tension gives more support, but if you've had two riggers look at it, they are obvious happy with the set up. If that's the case then more tension will only increase mast compression, which is not helpful. Mast pumping is more common in deck stepped masts because of the lack of mast bury which gives incredible stiffness to the lower half off the mast at least.

To help with your mainsail trim, make sure you have got a telltale on the outer end of your top batten. Then make sure you keep it flowing out straight when in a decent breeze. This should ensure any forward loads imparted by the leech are exactly 'normal'. Then make sure your halyard tension is enough to ensure the position of maximum draft is just forward of the mid camber of your mainsail.

If with your stays tensioned properly and your mainsail set properly, you still have a pumping mast, then you will need to think about checkstays. If you use dyneema, you should be able to have a system that is not too onerous. After all, they're not the mission critical sort you get on fractional rigged racing boats. They just help with peace of mind.

 

[30boat]

I used Dineema and it worked extremely well.

 

[skodster]

http://www.ybw.com/forums/archive/index.php/t-10391.html

 

[sarabande]

Richard

have you read Z spars excellent notes ?

http://www.zsparsuk.com/#!double-spreader-fractional-rig---aft-swe/cll6

They make specific reference to pre-bend.


On the main, do you have a good leech line ? Slacken it off to ease the leech almost to the point of inducing flapping; that may drop the boom a bit. Do you use the mainsail horse a lot ?

 

[richardbrennan]

Dear TimBennett

The sail is fully battened as was the one it replaced. However, the old sail was of lighter cloth and had four battens, the new sail, on the recommendation of the sail maker, is a heavier cloth and has five battens. I did not have this problem with the previous sail so I am tempted to think, especially as two riggers have now looked at it, that the sail is causing the problem, certainly none of the O33s that I have seen, which must have been at least half of them, have needed checkstays. I am interested in Sarabande's view that the leech may be over tight as keeping tension on the topping lift seems to ease the problem, the boom is higher than with the old sail, and the boat subjectively is carrying less weather helm.

Dear Sarabande

I am not sure what you mean by "main horse", is this possibly the vang or the traveller?

 

[TimBennet]

If the mast is set up properly with the correct stay tension and pre-bend, then the only change is the new mainsail.

Mast pumping is exacerbated by fully battened sails anyway and a heavier sail (cloth and batten hardware) will make things worse.

Leech tension (and roach size) will increase the forward loads on the battens (and hence the mast) but should be controlled by the topping lift.
It's possible that your roach has been increased slightly with the extra batten, but if you weather helm is decreased, that doesn't sound to be the problem.

Set the mainsail (halyard, vang, outhaul, sheet, etc) correctly as per any text book. In chop, use the top batten leach telltale to make sure you are not over sheeting.

At this point you know you have your mast set up correctly and the sail set correctly. If you mast doesn't have the 'stiffness' needed to resist the pumping loads with this particular boat / sail / sea combination, then something has to change. Comparisons to other O33s are pointless unless they have IDENTICAL mast / sail / rig / sea states, etc.

Your choices are:
1)Borrow another mainsail to see if that helps. If it does, then throw yours in the skip and buy one similar.
2)Fit simple check stays.

 

[charles_reed]

The rig is fractional but more like 19/20ths than that on a Fulmar and I have not seen another Ocean 33 with checkstays, which I assume are the same as running backstays, or with jumper stays

I am interested in the comments from sarabande as the only variable is the new main sail and it does seem to me that the boom is higher with the new sail which would match up with a tighter leach. It was also interesting that when I initially test sailed after the first rigger made his adjustments, I initially forgot to slacken off the topping lift and did not have the panting. Once I took the tension off the topping lift the panting started again. I do not usually use the cunningham but will try it and see if this improves things.

Many thanks for the comments

i bought a new main, in Vectran from Crusader. It definitely has far more drive than the old Dacron main, so I'd suspect that.

My boat originally had a thick-walled, bendy mast which is now acting as an example for 2nd year astro-engineers of fatigue in action.
Loic Gilbert recalculated from scratch and came up with a section 44% greater but <9% heavier.
Fitting checkstays, if you talk with competent riggers, is very much a last resort - mast manufacturers who specify that are really covering posteriors in bankerly fashion.

 

[30boat]

i bought a new main, in Vectran from Crusader. It definitely has far more drive than the old Dacron main, so I'd suspect that.

My boat originally had a thick-walled, bendy mast which is now acting as an example for 2nd year astro-engineers of fatigue in action.
Loic Gilbert recalculated from scratch and came up with a section 44% greater but <9% heavier.
Fitting checkstays, if you talk with competent riggers, is very much a last resort - mast manufacturers who specify that are really covering posteriors in bankerly fashion.

It's not just the mast ,it's the way it's rigged.

 

[Birdseye]

I have a problem with mast panting on my Westerly Ocean 33 when beating to windward in winds of twenty knots and more when I have a couple of reefs in the main and six or so rolls in the genoa. This is a known issue on these boats and the rig is notoriously difficult to set up. I have now had two riggers look at the problem and the rake of the mast has been reduced and various other adjustments made to the rig and this has improved but not eliminated the problem. What caused this problem to appear is a worry; the only thing that has changed on the boat is that I had a new mainsail at the start of the season which is heavier than the one it replaced. It is a heavier cloth and has an additional batten, is it likely that the new sail iscontributing to or causing the problem?

The mast wont pant without a mainsail hoisted so yes the sail is involved in the problem. Mast bend is, up to a point , likely to stabilise panting in the fore/aft plane, and the cut of the main as well as the battens will affect the mast bend. For example if the new sail is cut with less of an allowance for bend then to some extent it will counteract the bend that the mast has before hoisting - maybe have a word with crusader, who are very competent, and ask what mast bend they allowed for. Is it the same amount that you should have in your mast?

A really good rigger will know what to do but riggers are like many other trades - for every really good one who knows his trade there are a dozen who are pretty average and a few who should be serving tables. Is there one in your neiughbourhood who all the racers go to?

maybe the best cousre is to talk to a rig manufacturer - the guys at Z spars for example have been very helpful to me and do know what they are talking about.

 

[mrming]

I take it you have seen this thread:

http://www.ybw.com/forums/showthread.php?190933-WESTERLY-OCEAN-33

...and made an attempt to contact the rigger mentioned in the last post?

If not, that is the first thing I would do.

 

[Venus1]

A reefed mainsail is trying to invert and pump the mast, especially in a seaway. Any mainsail. I doubt that the new sail is to blame. Other posts have given useful info. But the main tool you need is lots of backstay tension. That may be all you need. Is still panting, next step is a baby stay (as previously mentioned). Unlikely to need check stays. Talking to the designer (Dubois?) might help.
Cheers,
Venus1 (lost a fractional mast when reefed - not enough backstay)

 

[richardbrennan]

Thank you for all the replies; it definitely seems that the core of the problem is almost certainly the new sail and I will speak to the sail makers this early coming week; they recommended the heavier cloth and the additional batten, which look as though they were not good choices. My first port of call was XW rigging who re-rigged the boat for me about six years ago. Ian Cochrane has now semi-retired and his son Paul has taken over the business. I have to say Selden have been spectacularly unhelpful; when you phone them you get the usual "please choose from the following options" and after several round the houses exercises, you get put through to one of their agents.

It will be interesting to see what the sail maker's reaction is; I see no alternative but a replacement sail as the one I have is clearly not fit for purpose.