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Help with measurement please - diameter of H18 furled jib.
http://www.hobie.com/forums/viewtopic.php?f=13&t=47420		 Page 1 of 1
Author:  John Lunn [ Wed May 01, 2013 6:22 am ]
Post subject:  Help with measurement please - diameter of H18 furled jib.
My jib snorkel is toast, it got shredded last Fall.
The zipper is still good, so I got some suitable fabric, and I'm getting a new snorkel built.
What diameter/width should be used?

My old one was too large a diameter, which is why it flogged itself to death.
Yes, it should not be too snug, otherwise it will 'rub' the jib as we raise the snorkel.
Someone have a jib snorkel so I can give the sailmaker some dimensions?

thanks all
Author:  srm [ Wed May 01, 2013 7:29 am ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
I can't give you a specific dimension, it is about 6" flat when doubled over (sorry, I don't have mine in front of me right now, but if I remeber, I will try to take a look later today).

But in regards to flogging... a few years ago I was using my 20 year old snorkle on our beach boat and we had a 25-30 knot nor'easter roll in which blew apart the zipper on the snorkle. This then allowed the jib to partially unfurl and get heavily flogged on the beach (requiring some minor repair).

I ended up fixing the snorkel and installing a new zipper and I also added three or four back-up velcro ties sewn to the cover that wrap around the snorkel & jib. This way if we ever have another zipper failure, the velcro will keep the jib furled. It addsd a few seconds to the snorkle hosit, but gives some added security. Just something to consider if you're having a custom snorkle made.

sm
Author:  John Lunn [ Wed May 01, 2013 7:45 am ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
Two things...
* You are the man! You have the answers.
* You are very quick with responses.

thank you very much

I'll go down at lunch time to get a quote.
Author:  presto13031 [ Wed May 01, 2013 9:00 am ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
srm wrote:
I can't give you a specific dimension, it is about 6" flat when doubled over (sorry, I don't have mine in front of me right now, but if I remeber, I will try to take a look later today).

That makes the Diameter approx. 7 5/8"
Author:  srm [ Wed May 01, 2013 9:18 am ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
presto13031 wrote:
srm wrote:
I can't give you a specific dimension, it is about 6" flat when doubled over (sorry, I don't have mine in front of me right now, but if I remeber, I will try to take a look later today).

That makes the Diameter approx. 7 5/8"


First off, for the record, I said I didn't have an exact number, but it is roughly 6" across when doubled over. The snorkle is just a flat piece of cloth which is doubled over (like a taco shell) with a zipper installed on the sides to form a tube. A doubled over measurement of 6" means the panel would be 12" wide (after hems), so a 12" circumfrence, or a 3-3/4" diameter.

sm
Author:  presto13031 [ Wed May 01, 2013 12:21 pm ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
srm wrote:
presto13031 wrote:
srm wrote:
I can't give you a specific dimension, it is about 6" flat when doubled over (sorry, I don't have mine in front of me right now, but if I remeber, I will try to take a look later today).

That makes the Diameter approx. 7 5/8"


First off, for the record, I said I didn't have an exact number, but it is roughly 6" across when doubled over. The snorkle is just a flat piece of cloth which is doubled over (like a taco shell) with a zipper installed on the sides to form a tube. A doubled over measurement of 6" means the panel would be 12" wide (after hems), so a 12" circumfrence, or a 3-3/4" diameter.

sm

PLEASE dont tell anyone that I am an engineer!!!! :D I realized I used the 2*PI*D (DIA=circ/pi) instead of PI*D when backing out to get the diameter about ten minutes ago and came in here to correct it. Taken from a proper frame of reference 3.75 is APPROXIMATELY 7.625.

ETA: I didnt mean any disrespect with the capital "D" in diameter, "Diameter" is how I see the word 95% of the time. I just did the math (incorrectly BTW) because I didn't know how comfortable Mr. Lunn is with numbers... 8)
Author:  presto13031 [ Wed May 01, 2013 12:28 pm ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
See John Lunn's Signature....
Author:  OlderBowman [ Wed May 01, 2013 12:34 pm ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
John,
over the years, I've seen lots of problems with jib snorkels of all kinds. from too-large ones flogging (which also caused abrasion to sails... not good), too small ones that are a PITA to hoist, to zippers that pull out or pull off.

if your boat spends a lot of time sitting with the jib/snorkel raised, then add tabs with turn buttons at regular intervals as a backup to the zipper. velcro will not last in a blow. make sure your sailmaker backs up the tabs inside with a second tab and sews them securely. I've seen them pull out too.

of course the best medicine is to take down the sail and stow it if its gonna blow really hard.
Author:  John Lunn [ Wed May 01, 2013 3:10 pm ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
thanks guys, and my sailmaker guy is sooo busy right now, he can't even look at it for another 10 days.

the real point of a H18 snorkel is to protect the jib from the damaging UV rays of sunshine.

I'll speak to him about velcro and snap tabs etc, however, I also don't want to build a Titanic!

Especially as I'm far more focused on mounting the new spin!

cheers and thanks
Author:  srm [ Wed May 01, 2013 3:19 pm ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
I measured my Murrays snorkle and it is 11" across in the flat, so 5.5" when zipped in half. It is a little snug to install, so I would probably recommend 12" across in the flat.

I would also add that I live close enough to the beach where I keep my boat that I can easily go and drop the jib if a strong storm is expected. If you're depending on the snorkle for all weather protection, you may be better off just dropping the jib after each sail. Messing with the snorkle takes almost as much effort as just raising and lowering the jib.

sm
Author:  SNovak [ Wed May 01, 2013 9:28 pm ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
John,
I can't help on diameter, but you could talk to your sailmaker about doing something like this:
Image

Basically, after you hoist the snorkel, you pull on the lines that criss-cross up the snorkel- this cinches the snorkel around the jib so it can't flog/chafe. I've used them on larger boats and they work pretty well.

Good luck!
Steve
Author:  Little Wing [ Thu May 02, 2013 6:17 am ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
I have a murrays snorkel and it takes a fraction of the time to pull up than to rig and derig the jib! Also a new jib is much fatter rolled than and old jib .
Author:  Q18 [ Thu May 02, 2013 10:15 am ]
Post subject:  Re: Help with measurement please - diameter of H18 furled ji
Last year I took a piece of 3" thin wall PVC grey it's used in underground conduit applications.Then I cut a slot about 2" down one side.Then you drill 2 holes on each side of the top.Set the tip of the conduit over the rolled jib put a line through the 2 holes .Then you slide the PVC up the jib with the line hanging down when it gets to the top you tie it at the jib lines tightening the line that goes up to hold the top.The conduit needs to be thin to flex to tighten and open a little for the jib.This worked good for one spot all the time not much good for moving around though.
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