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MitchK 09-24-2017 11:03 PM

Newport 28 mast bend
 
1 Attachment(s)
Hello all,
I recently purchased a 1982 Newport 28. All in al the boat is in great shape. As I am going over things, I noticed the mast has a pronounced bow with the top to the rear. Side to side, everything is nice and straight. I know some masts are bowed for racing and such. My boat does not have an adjustable rear stay. The two rear stays go to a plate and turnbuckle. The front just goes to a turnbuckle. What I want to know, is this the proper way the mast should be rigged? I could probably remove the bow by loosening the fore shrouds and taking up the aft shrouds, or I could adjust the rear stay out and tighten the fore stay. So again, is the mast supposed to be bowed, or should it be straight? Here is a picture looking up the mast for your reference. And yes, it is bowed that much.

RichH 09-25-2017 12:43 AM

Re: Newport 28 mast bend
 
For a single spreader rig (one set of spreaders), the 'usual' mast pre-bend should be ≈3/4" fore/aft bow ... for 'normal' sailing in normal wind/wave conditions.
For extremely windy venues, you can increase the amount of pre-bend to help flatten the mainsail; but in doing so, you 'can' break a non-tapered mast** or begin to bend the hull if the pre-bend is excessive due to the excessive rig tension. I'd suggest to 'back off' of the apparent over-bending and return the rig to 'normal' tensions and 'normal' pre-bend as described in the Seldén rigging guide. The Seldén rigging guide has a means to do this accurately without a rig tension gauge --- 'the meter stick method'.
Here's some documentation on the how and why, etc. that applies to most 'generic' masts: http://www.riggingandsails.com/pdf/selden-tuning.pdf.

FWIW - if you 'are' in an extremely windy venue, you 'can' have the luff of the sail 'recut' to enable to normally have a 'more flattened' mainsail ... instead of over tensioning and excessively 'pre-bending' the mast.


** tapered masts can withstand severe pre-bending; usually NOT found on mast-headed rig like yours. Your mast doesn't appear to be tapered.

overbored 09-25-2017 12:50 AM

Re: Newport 28 mast bend
 
Looks a bit excessive. On a mast head rig like yours. Mast bend is used to adjust sail shape, the forestay length sets the mast rake. The back stay adjusts the tension on the forestay to set the amount of luff curve to match the amount of luff curve that is designed into the foresail. The upper shrouds hold the mast straight side ways and the lower shrouds adjust the mast side ways and mast bend fore and aft.
Loosen the forward lowers first and the tighten the aft lowers to remove some of the bend. The curved mast will give you flatter sail in the mid section

RichH 09-25-2017 01:11 AM

Re: Newport 28 mast bend
 
If the boat is a Newport-II (built after about 1982) he won't have aft lowers, just forward lowers.

Outlaw7 09-25-2017 11:07 AM

Re: Newport 28 mast bend
 
I had a 1974 Newport 28 and it was fixed with a Baby Stay.

albrazzi 09-25-2017 12:07 PM

Re: Newport 28 mast bend
 
Quote:

Originally Posted by Outlaw7 (Post 2051219385)
I had a 1974 Newport 28 and it was fixed with a Baby Stay.

It does look like a Baby Stay, my CS 30 has the same rig. Im told the BS does not affect bend, BUT over tensioned with everything set right it will, no matter what you say, but that's not what its for..

OP whats your backstay tension, and if you can measure whats the fore tension.

Faster 09-25-2017 12:58 PM

Re: Newport 28 mast bend
 
I don't see a baby stay.. forward and aft lowers by the look of it.

If the mainsail is a bit 'bagged' someone may have induced that bit of bend to help with that - and/or it's possible the sail was designed for a certain amount of bend. I don't think it's excessive but could easily to tuned out by readjusting the forward and lower shrouds to bring it back into line.

I'd say it depends on how your main looks when sailing.

MitchK 09-27-2017 11:40 PM

Re: Newport 28 mast bend
 
Thanks for the responses. I do think there is too much bow to the mast. I'll loosen the front shrouds a bit and see what that does. Will probably have to tighten the rear shrouds to pull it back straight.

MitchK 10-18-2017 11:28 PM

Re: Newport 28 mast bend
 
All,
I got a chance to put my Loos PT-2 gauge to use over the weekend. I did not take any measurements on the aft stay as I could not get a useable reading on the 5/32 wires. So with that said, here are the number that I measured.

Forestay 7/32--18--250lbs--4%
starboard and port fore shrouds 3/16--14--360lbs--8%
starboard and port aft shrouds 3/16 16--420lbs--9%
starboard and port cap shrouds 7/32--21--360lbs--6%

Not sure the readings really have any meaning, but that is what the gauge read. At least it appears to have equal tension on both sides.



Mitch

albrazzi 10-19-2017 12:27 PM

Re: Newport 28 mast bend
 
With that little on the Forestay it shouldn't bow, but that's only if you have a backstay that you can tension under way. From you coments earlier you cant adjust under way but they are all adjustable at the turnbuckle. For moderate winds and some windward performance I would set the back stay at 10-12% then you would have about 15 on the headstay. Odd that you would have different size on the fore aft stays than the shrouds. Are you sure someone hasn't changed size from original.


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