telltales ala Avrel Gentry

Moderator: GreenLake

telltales ala Avrel Gentry

Postby K.C. Walker » Tue Feb 08, 2011 11:35 am

So, following a link that Green Lake put in the thread about centerboard lift, I found out about Avrel Gentry. I found his explanation of boundary layer behavior and methods for headsail telltale tufts very interesting. http://www.arvelgentry.com/tuft.htm

Has anyone here tried this out? I know that I'm going to have to try out some of this, and I have plenty of old cassette tape. :-) I am particularly interested in the idea of more precise steering telltales.
KC Walker, DS 1 #7002
K.C. Walker
 
Posts: 1335
Joined: Sun Jul 06, 2008 10:50 pm
Location: North Stonington, Connecticut

Postby GreenLake » Wed Feb 09, 2011 2:51 pm

I think that would be a fun thing to play with. Scaled to the DS, where do you plan to put your extra telltales?
~ green ~ lake ~ ~
GreenLake
 
Posts: 7136
Joined: Mon Jun 18, 2007 3:54 am

Postby algonquin » Wed Feb 09, 2011 11:58 pm

I have been using telltales on my sails but not to the level that gentry does. Will be using your info this spring and paying closer attention to the telltales. I do also place telltales on my rigging at the spreaders as well as about 5 feet above deck on the side stays. They also help to determine sail adjustments and help in determining apparent wind and true wind directions. Great for adjusting the rudder when you have a precise destination target you are attempting to achieve. Brad
"Feather" DS1 #818
algonquin
 
Posts: 475
Joined: Sun Sep 30, 2007 9:16 pm
Location: Maine Highlands - Grand Lakes Region

Postby K.C. Walker » Thu Feb 10, 2011 9:44 am

Green Lake,

I figured I'd go with the same 3 inch length tales. It seems like scaling them down much more than that might be hard to see. I thought I'd try a couple of rows of them somewhere around where I have my steering telltales now which is about 2-3 feet up. Heck, maybe I'll make my jib furry.
KC Walker, DS 1 #7002
K.C. Walker
 
Posts: 1335
Joined: Sun Jul 06, 2008 10:50 pm
Location: North Stonington, Connecticut

Postby K.C. Walker » Thu Feb 10, 2011 9:51 am

Algonquin,

I've never tried tales by the spreaders. I do have some indicators about 5 feet up, though. The one on the masthead tends to make my neck hurt if I watch it too much. :-) I guess if I hiked out more it be easier on my neck but it seems like when the wind picks up I pay less attention to the indicators.
KC Walker, DS 1 #7002
K.C. Walker
 
Posts: 1335
Joined: Sun Jul 06, 2008 10:50 pm
Location: North Stonington, Connecticut

Postby GreenLake » Thu Feb 10, 2011 2:54 pm

K.C. Walker wrote:I figured I'd go with the same 3 inch length tales. It seems like scaling them down much more than that might be hard to see. I thought I'd try a couple of rows of them somewhere around where I have my steering telltales now which is about 2-3 feet up. Heck, maybe I'll make my jib furry.


OK, my question was imprecise. Of course, the telltales themselves don't get scaled.

As for placement, I think you don't need a furry jib - in fact it could even be counterproductive (as in TMI).

Having several vertically positioned telltales allows you to set your fairlead so that the luff breaks evenly. Those don't need to be full rows, I think, because you are comparing the change in behavior with increasing height.

What would make sense to me is a single horizontal row of telltales that augment the standard steering telltales. I might try that some time.

Currently, I'm sailing with a very experienced sailor as "crew" - which is a great learning opportunity. He's the one who insisted on adding another pair of telltales higher up, to help him fine tune the jib sheeting.

The cautionary tale is another sailor, who proudly showed me all the telltales on his sails, but then admitted he didn't know how to read them all yet. That's why I tend to go slow...
~ green ~ lake ~ ~
GreenLake
 
Posts: 7136
Joined: Mon Jun 18, 2007 3:54 am

Postby K.C. Walker » Thu Feb 10, 2011 4:17 pm

Great Lake,

Yes, the furry sails were even too much information for Gentry. I use a couple of sets of steering tails at about 1/3 up the jib and 1/3 back from the luff and another set at two thirds up about a 1/3 of the way back. This is pretty standard stuff. I know that some boats have a window in the main so that they can see the spreader tip and adjust the jib to point right at that. It is kind of hard to see the upper jib telltale. On the main the leech telltales are what I watch mostly, and now after reading Gentry I know a little better why.

I'm thinking that the Gentry tufts might help teach me how to tune the jib better with the barber haulers and close pointing.
KC Walker, DS 1 #7002
K.C. Walker
 
Posts: 1335
Joined: Sun Jul 06, 2008 10:50 pm
Location: North Stonington, Connecticut

Postby GreenLake » Thu Feb 10, 2011 6:44 pm

Not to long ago, I added the leech telltales on the main (one at each batten) but so far, I'm not sure that I've learned how to make the best use of them. I think I know what I'm supposed to look for, but I'm not always sure what I'm seeing - if you know what I mean.

Haven't had enough time to be on the water just for the purpose of playing with things. The few times I've been out this winter, the conditions were all over the map, including nearly being run down by a keelboat.

Normally, I'd leave things like they are until I've caught up with them, but you are tempting me to add two pairs of telltales around the steering telltales that came with the sail to see if those really give the "early warning" that Gentry writes about.

Thinking about this some more, I'm wondering whether there's a difference between, say a larger keelboat and a DS. The DS is rather nimble, so tentatively luffing up a bit to nose out whether the groove has shifted with the wind might be easier than on a larger boat.

But heck, why not try this out, and if I learn anything, I'll write it down here.
~ green ~ lake ~ ~
GreenLake
 
Posts: 7136
Joined: Mon Jun 18, 2007 3:54 am


Return to Racing/Performance

Who is online

Users browsing this forum: No registered users and 2 guests

cron