tensioning Jumper stays

Moderator: GreenLake

Re: tensioning Jumper stays

Postby Fly4rfun » Wed Dec 09, 2020 12:29 pm

I will be careful, Ive not sailed it on anything bigger than the pond, and the jumper stays have never been on the mast as one was broken when i got it. update after the sail.

G.
"Sail Aweigh" 1966 DS1 #2675
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Re: tensioning Jumper stays

Postby GreenLake » Wed Dec 09, 2020 2:03 pm

If you keep wind-speeds in range and don't cleat your mainsheet, you should be good in the capsize prevention department.
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Re: tensioning Jumper stays

Postby tomodda » Wed Dec 09, 2020 3:01 pm

>When conditions are like this, the wetsuit comes out

Brrrr.... I'm saving up for a drysuit though, for my dreamed-of wintertime sailing. Great thing about winter sailing (back when I had a 24' keelboat), is that the air is so much HEAVIER. A 5 knot breeze at 30F will move you so much better than the same breeze at 90F. I know.. it's obvious, basic physics... but it's great fun to see it in action.
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Re: tensioning Jumper stays

Postby GreenLake » Wed Dec 09, 2020 5:57 pm

Well, it makes a 15% difference. Not shabby, but wind force varies with the square of the speed, so the way I read that is that is equivalent to a 7% increase in wind speed.
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Re: tensioning Jumper stays

Postby Fly4rfun » Wed Dec 09, 2020 6:36 pm

Same in flying, much better lift, reduced take off distance better engine performance in colder air, just stay away from icing conditions, that is not helpful for flight.

think I will stick to staying dry, can't afford a wet/dry suit.

GL. I have no intention in cleating the mainsheet unless I have very stable winds, don't want to get wet.
Last edited by Fly4rfun on Thu Dec 10, 2020 2:04 am, edited 1 time in total.
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Re: tensioning Jumper stays

Postby GreenLake » Wed Dec 09, 2020 10:42 pm

Very good. About staying dry. :)

The difference to flying is that in order to get 7% more "wind" your engine has to work that much harder. And a 7% difference in output is rather noticeable. In sailing the wind speed constantly fluctuates by more than 7%. And, for the most part, you would have to observe the effect w/o a steady reading from well-calibrated instruments (like those you have on an airplane for engine revs, airspeed, rate of climb). That makes me wonder whether the effect is in fact observable on a sailboat.
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Re: tensioning Jumper stays

Postby Fly4rfun » Thu Dec 10, 2020 2:10 am

another problem is I can't swim that well. getting back into the boat , I think would for me, be difficult with my strength loss.
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Re: tensioning Jumper stays

Postby GreenLake » Thu Dec 10, 2020 3:16 am

Looks like you need to ensure that you can stay afloat. In a capsize, you'll be even less likely than anyone to be able to do something about righting the boat. You might ponder whether that means you need a mast float (as otherwise the boat will eventually turtle after a capsize). Also to ponder is whether you'll benefit from a swim ladder. I know I can get of a pool over the side with all gear on (tried that) and feel confident that I could manage the freeboard for a DS, as that's not much higher than the edge of a pool. But not everyone can. You may have a scenario where the boat stays upright, but you've fallen out of it. Whether you rig a ladder depends on how likely you think that scenario could be.

Stay safe!
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Re: tensioning Jumper stays

Postby Fly4rfun » Thu Dec 10, 2020 12:18 pm

I plan on trying to get back into the boat this summer when it's warm. also considering a tender as not to be left if I fell overboard. I can tread water, swim a little using different strokes. but don't have a fear of water either. and will have some buoyancy with a life vest
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Re: tensioning Jumper stays

Postby GreenLake » Thu Dec 10, 2020 5:36 pm

If you haven't done that ever, or haven't done it in a while, arrange to jump into a pool, fully dressed. It might prove illuminating.

I had the chance to take part in a two-day Safety at Sea seminar a while back, which included a practice session.
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Re: tensioning Jumper stays

Postby Fly4rfun » Thu Dec 10, 2020 7:45 pm

I've been dumped by a few kayaks, and do try to swim (thrash) its the climbing back into the boat, a swim ladder dose interest me. going to put a helper strap on the top of the centerboard trunk to grab to assist me when changing sides with tacks and stuff. (old and decrepit i guess)
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Re: tensioning Jumper stays

Postby GreenLake » Thu Dec 10, 2020 8:41 pm

When we were young, and living close to a ski area, the parents made us take a "ski gymnastics" course, to limber up and strengthen some of the muscles. Sounds like you would benefit from doing your own set of exercises. Bet you know enough to be able to figure out what they should be. World famous Danish sailor Poul Elvstrøm is said to have practiced hiking on the edge of his bathtub to get a leg up on the competition in stamina. I know that as long as I keep sailing often enough, I can retain critical strength to do certain things safely and without throwing out my back (like raising a keel-stepped mast). I did injure my back the very first season, because I had developed neither the strength, nor the "knack" for that strenuous task.
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Re: tensioning Jumper stays

Postby Fly4rfun » Thu Dec 10, 2020 9:02 pm

GL, that's the plan, need to improve my balance.
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Re: tensioning Jumper stays

Postby Fly4rfun » Mon Feb 22, 2021 7:40 pm

Tom

I was rereading some posts on tensioning the standing rigging, as I just purchased a used Loos gauge and wanted some info on how taunt to make the tension. I notice this statement in one of your post. "And be advised that post-pandemic, I'm going to lure you down to the Chesapeake. DS1 to DS1 match racing on the Piankatank! "

I will definitely take you up on this. have been looking and considering going that way and doing some more aggressive sailing to improve my skills.
G.
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Re: tensioning Jumper stays

Postby tomodda » Mon Feb 22, 2021 8:41 pm

Chesapeake is truly wonderful. September, maybe? Fingers crossed. The great thing about our DS's is that we can get into places that the big boats and big stinkpots can't. Lot's of wonderful sailing.

In the meantime, wow, an affordable Loos Gauge, congratulations. I believe North Sails recommends that the port and starboard shroud be set at 300 lbs and the headstay at 250 lbs. Which is crazy tight. National Champ Dave Keran also sets his rig very tight at 200-210 at the forestay and 300-320 at the shrouds. On the other hand, Doyle Sails say 50 lbs:

https://web.archive.org/web/20150315153946/http://www.doylesails.com/onedesign/daysailer/tuning.html

and Dieball (over here):

https://web.archive.org/web/20190423161718/http://www.dieballsailing.com/content/tuning/2012%20Day%20Sailer%20Tuning%20Guide.pdf

says: " Forestay tension should be 240-250 lbs while the shrouds will be 350-400 lbs depending on the overall stiffness of both your boat and mast" Wow! Personally, I still think that strumming a Low E or an A is good enough, but enjoy experimenting with the Loos.

Why is tension important? Mast prebend, how much your mast is bent "standing still." The sailmaker should have put some curve into your luff - that's to compensate for the prebend, but actually to give you a nice draft in light air that can be flattened out with more bend in heavy air. You want to match that curve with your prebend, which you do by tensionsing the stays. Each sail and sailmaker is different, so it's a trial and error process to find correct tension values. To the point, look at what Dieball and North have to say about how much rake and prebend you should have based on the position of your mast butt. Dieball explains it all best, IMHO. Try that out, see how much tension you need to get enough prebend into your sail to eliminate any wrinkles when testing on land, no wind. That's your startpoint. Then go sailing! Log what happens if you tighten/loosen a bit, etc, etc. Before you know it, you'll be racing in the Nationals! ;-)
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