Asym sizing - SailNet Community
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post #1 of 7 Old 05-09-2015 Thread Starter
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Asym sizing

We have an opportunity to pick up an asym and sock at a good price, but it is for a 45' boat with a 45' stick. We have an I of about 58 feet.
I know nothing about asyms except they don't require a pole, which is why we are interested.
Would this 45' asym be too small for our boat to be of value in light air?
Thanks.

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post #2 of 7 Old 05-09-2015
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Re: Asym sizing

Hey capta here is a idea, get that asym. and use it on your mizzen . Of coarse you will have to get another asym. for your main mast to fly as well . And don't
forget to pole out that jenny to weather.
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post #3 of 7 Old 05-09-2015
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Re: Asym sizing

Your J is ~19ft.
Your I is 58.ft
A proper Asymm for the P53 will be in the 'range' of 160-170% LP =
= 19 x 58 x (.75) x 1.65 = approx. 1360 sq. ft.


An average sloop 45'er
J= 16'
I = 45
Asymm @ 160-170% LP
16 X 45 X (.75) X 1.65 = ~890 sq. ft.

890 / 1360 = .65 ... the asymm from the 45'er will be approx. 2/3 the area of what you need. With the head of the 45'er asymm '2-blocked' to the top of the mast, there will be an approx. 14 ft. 'gap' between the tack and the stem fitting on a P53. OR, flying an 890 sq. ft. asymm pinned to the stem, there will 14 ft. 'gap' between the head and the mast ...... and that would make for one 'squirrelly and unstable' asymm, as spinns not only 'drive the boat forward' but also tend to 'lift' them out of the water!

Rx: tooooo small area, and the luff will be toooooo short. Suggest a 'Pass'.

If your have a 'decent' (metal geared?) 'dressmakers' sewing machine .... have you looked into sewing up your own spinn????
Building your own Asymm from a 'kit' is quite easy for a first time DIYer, no sailmakers sewing machine required.
http://fabric-calculator.sailrite.co...20(ketch%20rig)

;-)
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Last edited by RichH; 05-09-2015 at 04:14 PM.
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post #4 of 7 Old 05-09-2015 Thread Starter
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Re: Asym sizing

Quote:
Originally Posted by RichH View Post
Your J is ~19ft.
Your I is 58.ft
A proper Asymm for the P53 will be in the 'range' of 160-170% LP =
= 19 x 58 x (.75) x 1.65 = approx. 1360 sq. ft.


An average sloop 45'er
J= 16'
I = 45
Asymm @ 160-170% LP
16 X 45 X (.75) X 1.65 = ~890 sq. ft.

890 / 1360 = .65 ... the asymm from the 45'er will be approx. 2/3 the area of what you need. With the head of the 45'er asymm '2-blocked' to the top of the mast, there will be an approx. 14 ft. 'gap' between the tack and the stem fitting on a P53. OR, flying an 890 sq. ft. asymm pinned to the stem, there will 14 ft. 'gap' between the head and the mast ...... and that would make for one 'squirrelly and unstable' asymm, as spinns not only 'drive the boat forward' but also tend to 'lift' them out of the water!

Rx: tooooo small area, and the luff will be toooooo short. Suggest a 'Pass'.

If your have a 'decent' (metal geared?) 'dressmakers' sewing machine .... have you looked into sewing up your own spinn????
Building your own Asymm from a 'kit' is quite easy for a first time DIYer, no sailmakers sewing machine required.
Pearson 530 (ketch rig) Sailboat SailPlan Data and Sail Quoting System)

;-)
Thank you very much. I'll certainly check out the kit sail as well. We have a conventional spinnaker (but no dowser/sock), but our pole is the extending type so it might not handle the chute?
I'm wondering if a better answer would be a code zero for our use; we so rarely get light air down this way, and we are almost always beating. I still haven't had to hank on the 130 genoa in 5 years. It would be really nice to have an easy to set, light air sail for those few days a month.

Markwesti; We have a really sweet mizzen staysail, so I'm not sure the asym would be any better, but thanks. It would actually fit the mizzen pretty nicely, I think.

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post #5 of 7 Old 05-09-2015
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Re: Asym sizing

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Originally Posted by capta View Post
we so rarely get light air down this way, and we are almost always beating.
Why is it that in the trade winds zones, that the 'turney-pointy thing' on top of the mast is the DESTINATION FINDER ??????? :-o

Take heart, as with the present advent of damn few to a rare cyclical minimum of 'sunspots', thus declining solar output; lowering planet temperatures ... those damn trade winds historically will INCREASE. .... and have been doing so for the past ~3+ years. If this continues you wont need a asymm spinnaker. ;-)
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post #6 of 7 Old 05-10-2015
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Re: Asym sizing

Capta we've had asym's and on current boat a code zero, and we've come to prefer the code zero. When you are behind one of those islands blocking the trades on a light day, and reaching, I think you'd be very happy, and it's nice to roll up the window shade if things pipe up.

Looks like your boat has a sprit. Need to get the code zero in front of everything and tension the halyard for the roller to work right. Fractional rig with a sprit is a great solution to this, I think you could get in front enough with a mast head rig and a sprit, but I'd check this before diving in.
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post #7 of 7 Old 05-10-2015
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Re: Asym sizing

I'm with Rich. Where do I want to go? That's where the wind is coming from. The fastest current point of sail . . . dirctly to the closest reef, rock or promontory. And all this time I thought it was just me.
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