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Author Topic: Flying Jib on a model  (Read 597 times)

roycv

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Flying Jib on a model
« on: July 20, 2018, 11:59:51 PM »

Hi all, I was pondering the question of the flying jib this afternoon sailing a newly built gaff rigged model.  I have a running line for the fore jib not under RC and I adjust with a bowsie.
 
The lines to the fore jib go through an eye and lie either side of the jib, the problem here is that the jib itself is restricted by the fore jib sheets.  There is a definite difference when the fore jib is 'pulling' against not quite crossing over the jib and it upsets the balance of the yacht.

I am thinking to introduce a second servo to adjust the amount of sheet line available to the fore jib.  I don't want to have a track system as Robbe have done.
Any suggestions welcome, I have looked at all the previously mentioned material  but they do not resolve the free movement of the jib.  One system involving taking a sheet to the front of the jib and then to the fore jib I cannot see how the fore jib will be controlled, i.e. it will not be set correctly.
Regards Roy


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tigertiger

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Re: Flying Jib on a model
« Reply #1 on: July 21, 2018, 02:48:17 AM »

If sounds like the fore jib is fouling against the fore stay (assuming the jib is a stay sail). If the sails are as standard in a kit, they should fit and adjustment might be possible, to the jib and fore jib. If it was designed as a working model. See pic


OR if you cut the sails yourself, recut until the fore jib clears the stay


Or rig it as a genoa sail would be rigged. Discussion here http://www.modelboatmayhem.co.uk/forum/index.php?topic=61255.0;topicseen


The only other possibility that I can think of is if the control sheets on the fore jib are under tension, and this is making the jib sail taught and unable to pass over the fore stay. If that is the case allow some slack in the sheets.
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tigertiger

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Re: Flying Jib on a model
« Reply #2 on: July 21, 2018, 03:11:43 AM »

The alternative is to cheat, like I did http://www.modelboatmayhem.co.uk/forum/index.php/topic,2716.msg26949.html#msg26949
Replies #14 and #15.
This is nowhere near an actual sail pattern, but could be adjusted/cut to make it look more authentic. However, it works very well.
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roycv

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Re: Flying Jib on a model
« Reply #3 on: July 21, 2018, 06:05:02 AM »

Hi TT. thanks for your thoughts.  I designed the sail gaff rig pattern to replace the Bermuda one which was the kit design with the intention of having just enough overlap from the stay sail so that when tacking and the sails fluttering it would come across. The centre of effort of the new sails are ballanced across the CLR of the hull and she stays on a tack without recourse to rudder, so that part has been successful.  That took me a couple of days with tracing paper cut outs and reworking how the c of e was moving.
 As an experiment on this boat I had the staysail sheets come back to behind the mast so they were at right angles to the wire stay.The thing I was not expecting was the sheet which is a loop either side of the jib, now contains the jib and restricts movement.  The staysail flies very well, it is the jib which is the problem.
I think it all needs another think and probably moving the staysail sheets to be controlled from a point on the deck much further forward allowing the jib a greater angle of movement.  Much as the drawing you did in building M J Ward.  I think I might add in a standard servo to adjust the staysail sheet lengths.  I have on order some 180 degree movement servos (3 for less thn 10) which should do the job.

I changed the sails as firstly I like that rig and lowering the centre of effort of the sails has also meant I could increase the total sail area.  I had to do this as she did not look right otherwise.  She ghosts along in the lightest of winds and although I have made provision for a detachable shall we say Headsail, (to fly between mast and gaff) I do not think I will need it now.  She is incredibly maneouverable and spins on a sixpence.  That does reveal my age!  And today is my birthday, never thought I would make 80 feeling fit and well!  Still got lots more boats to build!
kind regards
 Roy





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roycv

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Re: Flying Jib on a model
« Reply #4 on: July 21, 2018, 06:19:21 AM »

Hi  TT on another point I wanted to use nylon covered wire fishing line as stays and shrouds but it does not work very well in a bowsie.  I have used turnbuckles before on another yacht but they are rather fiddly.  I use Dyneema fishing line which is OK.  I have used a heavy spring at the base of the mast to tension the stays, but it also has its drawbacks.  This is about the sixteenth yacht I have worked on and you learn something new every time.  Eight are with their owners I have the rest.

Any thoughts?
regards Roy

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tigertiger

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Re: Flying Jib on a model
« Reply #5 on: July 21, 2018, 08:11:42 AM »

I have used braided fishing line, but mainly use Dacron chord shown in reply #74 here http://www.modelboatmayhem.co.uk/forum/index.php/topic,2716.50.html


Although it is white it stains well with black or brown boot polish. The black is probably better as the brown tends to fade pink, and the black fades to grey.
I bought my Dacron cord from these guys http://www.sailsetc2.com/store/index.php/products-by-category/spars-rigging/running-rigging.html It comes in two breaking strains. I use the 25Kg for running rigging and 60kg for standing rigging.
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roycv

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Re: Flying Jib on a model
« Reply #6 on: September 28, 2018, 09:23:05 PM »

Hi I have been a bit late with this but I ended up by keeping the flying jib separate from the sail winch system.  I have put the jib on a running line tethered at one end with an adjuster bowsie.  The other end goes to an extended arm servo which can tighten the line as required, this flattens the sail and has a positive effect on the speed.
It does need a 3rd. channel and I use an old Hitec Tx. that has the third channel next to my right thumb and so is positioned as required.
regards Roy
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tigertiger

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Re: Flying Jib on a model
« Reply #7 on: September 29, 2018, 02:20:21 AM »

If you do not need independent control of the servos, but just a different range of motion, you could could look at the ACTion Electronics Servo Morph. If memory serves it allows you to have more than one servo on the same radio channel, and you can adjust the range of motion on one of them using the servo morph.
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JerryTodd

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Re: Flying Jib on a model
« Reply #8 on: October 03, 2018, 01:33:42 PM »

I use a "semaphore-arm" sheeting system on my over-lapping sails.  It allows sheet adjustments out to running, and "casts-off" the lee-sheet when coming about so there's not constant tension on the sheet to drag over the stay.  I don't sheet to the center-line unless that's where the prototype was sheeted.You only really require constant tension on the sheet if you're using a winch.Another method is a sliding-sheet.  The sheet runs from the end of a servo arm through the clew grommet of the jib and back to the other arm of the servo.  Knots, beads, or some sort of stoppers on the sheet on either side of the jib catch the sail and pull it along.  When tacking, the sheet runs through until the other stopper pulls the sail over.  This set-up also casts-off the sheet when tacking and allows for sheeting out more realistically.

roycv

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Re: Flying Jib on a model
« Reply #9 on: October 06, 2018, 01:58:11 PM »

Hi Jerry, after a long look I realised how your semaphore system worked.  Simple, Clever, I shall have a think about that and see if I can adapt it to one of my yachts.
Thanks

Roy
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JerryTodd

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Re: Flying Jib on a model
« Reply #10 on: October 06, 2018, 02:23:55 PM »

You'll find most boats sheet the heads'ls out-board, not to the center-line.  Even clubbed jibs and stays'ls that do sheet to the center-line actually sheet to a block on a traveler.    Sheeting to the center-line often is too much, and will stall the sail and cause problems trying to tack. 
In the case of the semaphore-sheeter, routing the sheets out to the rails separates them below deck helping prevent them from tangling together.

roycv

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Re: Flying Jib on a model
« Reply #11 on: October 06, 2018, 02:59:38 PM »

Hi Jerry thanks for the ideas, I am used to full size sailing so appreciate the points you make.
I am working on 3 yachts at the moment, so hands full!
regards,Roy

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