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-   -   Pearson 30 Mast Bend Info ? (http://www.sailnet.com/forums/pearson/82563-pearson-30-mast-bend-info.html)

Brettms 01-09-2012 11:41 PM

Pearson 30 Mast Bend Info ?
 
Does anyone have an idea of how much you can bend a P30 mast? I am trying to take some draft out of the mainsail I'm using and have been able to bend it about two inches measured from a taut halyard about mid mast. However, that is the end of travel on the backstay turnbuckle. I've also tightened the topping lift/mainsheet to get the two inches. I'm wondering if there is any point to getting a shorter backstay for some more bend.

The mast was straight when I started.

Thanks.

RichH 01-10-2012 12:01 AM

Max. prebend for the typical single spreader rig such as what you have on the P30 should be 3/4" max. .... although when I was hard racing my old P30 I would crank on to about 1" max. prebend bow if the conditions were 'blammo'.

If you really need to flatten the main, then have some luff hollow re-cut into the leading luff edge of the sail to remove the excess draft. If this is to correct so-called 'weather helm' or to correct the boat from aggressively heeling over, then Id suggest first that you properly raise the main with proper 'halyard' and cunningham tension applied, first.
Here's a short version of how to set up a dacron mainsail for 'best' shape and 'best' weather helm; the P30 if set up and sails shaped correctly by correct luff/halyard, etc. tensions should only require light finger-tip pressure on the tiller to allow it to sail like a 'raped ape' and with the keel 'lifting to weather'!!!!: How to properly RAISE a woven dacron mainsail - SailboatOwners.com

You really have to be quite careful with extreme mast (compression) loads and forestay/backstay loads on a P30 as this thin-hull layup is 'floppy' and is easily "reverse hogged" and elastically deformed .... you dont want to 'break the boat' by unnecessary overtension of the rigging, etc.

Brettms 01-10-2012 10:49 AM

Rich,

That's a great reply. Thank you.

My interest arises from replacing a very old heavy main with a shrunken bolt rope with something newer, lighter and used from an Etchells 22. The E22 sail seems to have quite a bit more draft. I hoped I wouldn't have to have it cut to take out some of the luff curve.

My basic problem with the boat has been pointing in club races. The pointing isn't the problem as much as it didn't track where it was pointing.

My reading on mast bend had left me with the impression I might get 4-6" where I'm measuring. We have plenty of 30' Catalinas, Ericsons and Newports around here that have backstay adjusters that I thought the P30 might be suitable unless the mast is just too stiff.

The way it is rigged I didn't expect very much "prebend" but I did hope to get a bit more bend while sailing to windward.

Thanks again!

RichH 01-10-2012 02:20 PM

Quote:

Originally Posted by Brettms (Post 815129)

My basic problem with the boat has been pointing in club races. The pointing isn't the problem as much as it didn't track where it was pointing. Thanks again!

From what you describe, you probably have adverse leeward 'slip' of the keel, caused possibly by excess draft and draft-aft mainsail *shape* .... AND .... If the wake from the stern of the boat isnt trailing back almost 'straight back' (~ about 3 off of straight back), the keel wont 'lift/fly to weather' and you can easily begin to 'skid' off to leeward.
Skidding off to leeward is more a function of forestay tension than adverse mainsail shape, etc.
Once you get the proper mainsail tensions/shape, then Id suggest you concentrate on forestay tension .... and you really dont need a backstay tensioner to do this but it helps. Proper forestay tension will correct side skid and correct a LOT of what appears to be (so-called) 'weather helm'. Here's how to assure proper forestay tension (if you cant clearly read this, IM me and Ill send a PDF): MatchingLuffHollow.gif picture by svAquila - Photobucket
..... then and only then you can 'futz' around with mast rake to correct for minor helm imbalances, etc. .... but the sail shapes and forestay tension should be 'dead on' before you do any 'mast-raking'.

Once you get the proper mainsail shape and forestay tensions, then I heartily suggest: ArvelGentry.com ---> magazine articles --> (a 'sequence' of sail shaping articles):
Checking Trim on the Wind, November 1973
Achieving Proper Balance, December 1973
Sailing to Windward, January 1974
Are You at Optimum Trim?, March 1974

A properly set up P30 with properly 'shaped' sails should leave those Etchells and Catalina 30s .... way back in the dust.

Id opt for a mainsail to exact P30 dimensions if you want to eventually 'dominate' your fleet as the optimum mainsail size and shape is what makes the 'flow' over and around the jib on masthead rig so 'efficient' .... if you have a 'sub-optimum' mainsail or sub-optimum mainsail shape, the jib will never develop its optimum 'aerodynamics' ... and this is valid for 'any' masthead boat !!!!!!!!

;-)

Brettms 01-10-2012 07:03 PM

Rich,

Thanks again. There is lots of good info in your reply.

I'd still like to hear from anyone who has bent a P30 mast more than an inch or two
before I go any further or spend more money.

Brett

Faster 01-10-2012 07:46 PM

Brett, Rich H is one of our better advisers on things sailtrim and esp Pearson boats... You're unlikely to get better information - even if it's what you want to hear.

Keep in mind, too, that even if you're able to 'induce' such bend in a masthead rig through backstay tension, for example, that means the rig is also becoming shorter.. ie the masthead is closer to the deck.. that slackens your shrouds. Given that the Pearson hulls are known for flexibility, all of this seems a bad idea.

Get the right sails for your boat, esp if you're serious about fleet/club racing.

RichH 01-10-2012 09:49 PM

Thanks for the kudos, Faster. You do bring up a very important point.

I race ILYA scow boats with extreme on the fly mast rake and radical mast bending ... and you are absolutely right with extreme bowing of the mast the cap shrouds can become soooo loose as a result, that the only way such boats can keep the mast 'straight up' is to use bodacious mast wedges in the the mast's 'deck hole'.

Something else along the same line of Faster's post/info is to consider is that to accomplish more than an inch or two of mast prebend on a single spreader non-tapered mast one is definitely going to have to massively 'crank up' some of the rig tension. Anytime that the tension in any shroud or stay goes much beyond 30% of ultimate strength .... you become *very* vulnerable to accelerate premature 'fatigue failure' .... and I have lost a few masts because of this ..... very unpleasant, and I now take it easy and only 'normal' tension a rig; its less expensive than replacing a mast, etc. :-o

sailingfool 01-11-2012 08:17 AM

The masts on these old '70s boats are built like telephone poles, and are not designed to bend, so dont put too much effort into bending it. Sounds like you've got as much bend as it wants to permit. Definitely do not tension the topping lift to try to add bend, you may break something, especially if you have a mid-boom mainsheet. The mainsheet needs to be tensioning the mainsail, not restricted by the topping lift.

Brettms 01-11-2012 10:30 AM

Sailingfool,

Thanks for the comments. I was kind of struggling with your conclusion when I started this thread. It just didn't seem to want to bend in spite of many other things I had read. Seems to be a pretty unanimous conclusion at least for the P30 masts.

Thanks to all for the comments.

zedboy 01-11-2012 12:37 PM

Quote:

Originally Posted by RichH (Post 815198)
.... If the wake from the stern of the boat isnt trailing back almost 'straight back' (~ about 3 off of straight back), the keel wont 'lift/fly to weather' and you can easily begin to 'skid' off to leeward.

Rich I always enjoy your detailed comments on sail trim, it's quite an education!

Can you elaborate on what you mean by the keel "lifting to weather" and affecting whether the boat tracks or skids off to lee? The wake not trailing straight back means you are already skidding off, right? Is all you mean that if the jib shape isn't good (because the forestay is sagging) the jib will cause excessive heel which makes the keel less effective at keeping you on track?

One of the big goals for this coming season is improving windward performance :D

Thanks for the Arvel Gentry link, amazing stuff. Started on it a little last night, will go further during lunch...


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