Tell tails don't tell tall tales!?!? :: Catamaran Sailboats at TheBeachcats.com

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Tell tails don't tell tall tales!?!?

mma600psi

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Posted: Jun 22, 2009 - 12:26 PM

Sorry had to use the play on words for the subject line.

Question: When sailing on a close reach I can get the tell tales on my main sail set fine, leeward and windward flowing even and horizontal. Traveler on main is set out about 3-5 inches.
The issue is the jib. Even with the jib haulers brought in towards the centerline of the boat and the jib is two-blocked the all of the tell tales on the windward side are floating up.

Boat type is a hobie 16. My only thought is that the mast should be raked further back. Any input?
UFgator

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Posted: Jun 22, 2009 - 02:37 PM

Good question. I can't wait to see what kind of answers this one gets.

I don't think that your mast rake is causing the differential. Sail shape due to how it's hauled in is most likely the culprit.

Hmmm?
MN3

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Posted: Jun 22, 2009 - 03:51 PM

and the answer is:

if your tale's aren't breaking at the same time you need to either move your blocks forward or aft... unless your jib is totally shot, this should handle the problem.

Btw... what do you mean your jib is 2blocked? (i hope you don't mean you have both blocks engaged... because there is NO reason i know of to have the windward block set,ever)

edited by: andrewscott, Jun 22, 2009 - 04:23 PM
HULLFLYER

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Posted: Jun 22, 2009 - 05:50 PM

I think what he means is that the jib clew block is all the way down and is touching the jib sheet block that is located on the jib traveler track. It happens on older Hobies if the mast is really raked and the tack of the jib is in the most bottom hole of the adjuster at the bridal wires. Hobie 16's only have an inboard and outboard adjustment. Try moving the tack of the jib further up the adjuster and maybe you will be able to sheet in a litle more, also move the jib travler outboard a few inches and see what that does. Is the jib back winding the main, maybe you are choking off the slot. One more thing, don't always assume that the tell tails are in the proper spot, they could have been changed by the previous owner. Maybe your jib is just blown out as Andrew says, you can always have a little cut off the clew of the jib and move the clew plate up to gain some, so when you sheet in hard you will not be block to block as you say.
MN3

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Posted: Jun 22, 2009 - 06:34 PM

gotcha... i have forgotten just about everything about rigging an h16 (i owned one for 6 years, but really didn;t know JACK back then)...
UFgator

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Posted: Jun 22, 2009 - 08:46 PM
UFgator

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Posted: Jun 22, 2009 - 08:49 PM

Bernoulli's Principle is the answer too.

You'll get if figured out. Work the sails a little bit more and you'll find the sweet spot. As tempting as it may be don't sheet in the jib too much.

Good luck.

edited by: UFgator, Jun 22, 2009 - 07:50 PM
MN3

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Posted: Jun 23, 2009 - 09:29 AM

UFgatorBernoulli's Principle is the answer too.

Yes, it is part of it...
(Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.)

BUT its allot easier to adjust your jib shape than to master hydrodynamics, friction, drag, and thermo-nuclear photon theory :)

PS i agree... don't over sheet your jib.. this closes the slot... i have found the more i open my slot.. the faster i go in MOST situations.

edited by: andrewscott, Jun 23, 2009 - 09:29 AM
UFgator

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Posted: Jun 23, 2009 - 12:56 PM

I thought you would bite at that one Andrew. I couldn't help it. The pilot in me just wanted out.

Sails are not unlike an air foil or wing. The theory applies to air flow as well. You know the Lo pressure Hi pressure issue. Sail tension changes this property as the sail shape changes. Don't want to get all technical. Keep it simple.

Like I was saying trial and error will work this out.
MN3

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Posted: Jun 23, 2009 - 01:34 PM

Yes keep it simple.. but it is interesting to learn the real dynamics behind our modern sailplan.

air flow lamination is a part of it too...

i NEVER think about the technical theory's while sailing... but one thing that is multiplied is High/low pressure and air lamination with a spinnaker....

As i head up (and heat up) i sheet in.. build apparent wind... and then fall off... all the while super gently letting out a little on the spin sheet... this helps NOT delaminate the airflow and dump power (and my apparent wind).

this can apply to jib technique as well
UFgator

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Posted: Jun 23, 2009 - 02:41 PM

Very true. Luff action on the jib reduces the power as well. One tip I've heard and used is simply listening to the sail. Sheeting in until the "motor boat" sound just stops and adjusting travel to tune the tell tails.
PDS624

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Posted: Jun 26, 2009 - 01:33 PM

do you have battens in the jib? If not, has the sail been cut down for an auto furler? Some of the big old jibs act like genoa's if you remove the battens so it could be the excess bow of the sail