UK-Cherub Forum

Cherub Chat => Tech Chat => Topic started by: JP233 on July 11, 2016, 09:35:33 PM

Title: Jib Track Stuff
Post by: JP233 on July 11, 2016, 09:35:33 PM

Had a wonder round the boat park at castle cove with a tape measure. hopefully this is useful to someone.
I've collated this data, (i did Marmites measurements wrong, can you re measure please Paul?)
Data i took was the usable track the jib car can travel on in a straight line(so outer stopper to outer stopper) then forstay attachment to one of the jib stoppers (Not the middle, see comments about Marmite)

as you can see, Shinys jib car is quite far outboard, where as Usagi's is a lot more inboard, but further aft.

I will leave you to decide what is best.

PS. Happy to add more boats is people can measure and send me the info.

(Hopefully this one will work)

Title: Re: Jib Track Stuff
Post by: kerrgreg on July 12, 2016, 08:48:45 AM

Ill measure madge for you too

Title: Re: Jib Track Stuff
Post by: JP233 on July 12, 2016, 09:54:16 AM

Here is the raw data:

Marmite
Ear/ear 850mm
Foot length. 1600mm. WRONG!!

Poppy
840
Foot is 1840mm

Ronin
Ear to ear 810
Foot is 1800

Usagi
770
2000

EJ
800
1870

Shiny
900
1730

Title: Re: Jib Track Stuff
Post by: dave_ching on July 13, 2016, 12:21:02 PM

All I can conclude from that is it isn't as critical as you would think. I guess we all set the sails to cope with what we have.

Title: Re: Jib Track Stuff
Post by: simon_jones on July 13, 2016, 05:55:32 PM

Eleanor
835
1870

Title: Re: Jib Track Stuff
Post by: JayW on July 14, 2016, 06:55:40 AM

Can convert each of these to a sheeting angle.
So EJ (800, 1870) is 12.3 degrees (sine 400/1870)
Eleanor (835, 1870) is 12.9 degrees.

Interesting but nowhere near the whole story!

Title: Re: Jib Track Stuff
Post by: pratn0 on July 14, 2016, 09:37:15 AM

Quote from: dave_ching on July 13, 2016, 12:21:02 PM

All I can conclude from that is it isn't as critical as you would think. I guess we all set the sails to cope with what we have.

It all depends what you are trying to achieve.  a narrow slot for high mode or a wide one for low/fast mode.   on the 18's we inhaul when under powered and in high mode, keeping the leach straight. then as the we get over powered first step is to easy the in haul then if main still backing cracking the jib.

you could say that from these number the boats that tend to foot and blast more have slightly wider tracks vs those which tend to point more have narrow tracks.

As for the longer J measurement (forestay to jib car) this is some what controlled by the mast placement with the E5 having the mast a long way further back than the older designs will have a larger J (ie Andy).   Looking at the sail areas the E5 tend to have larger jib area (4.75m2 - 5m2) and smaller mains vs older boats  which are between 3.9m2 - 4.4m2 and have larger mains.

Title: Re: Jib Track Stuff
Post by: kerrgreg on July 17, 2016, 05:13:05 PM

1650 from center of forstay fitting to center of jib track stopper
685 inner edge of stopper to inner edge of stopper in straight line
740 to outer edges of stoppers

Which makes madge around 11.8deg jib angle