Hi!

The guys from Shanghai had a nice sunday on the frosty water [its not by incident called 'frostbite regattas' ;-)]seeing first time four 4.9 with spi in singlehanded mode sametime. course was very short so a lot of manouvers held us warm and tension up!

so we finally managed also to get closer to our jibfree trampoline idea by measuring some essentials.

what we think can be a possible 'window' for a new jib design would be like this:

leech: 5.20 m
luff: 5.30 m
base: 1.30 m

I would like to compare our proposal with what are the sizes of the selftacking jib you might be using on a taipan 4.9 in F16 set up?

would be great!

thanks!

Naturally I have a Taipan platform that was converted to full F16 mode. This means that more fore triangle (mast, fore stay, spi pole) is still the same as on your standard Taipans. My jib luff does however move passed the bridle plate and along the strut down to the spi pole.

The measurements of my jib are :
Op voorlijk (lijkt langst)

Luff length jib = 5480 mm
Leech length jib = 5300 mm
Foot = 1220 mm (measured from farthest point forward on luff to the virtual intersection point of foot and leech)

Distance sheet corner to luff measured along a line perpendicular to the luff : 1180 mm

My leech in concave and the max deviation of the straight line through the top and the clew is 60 mm. (The leech is curving towards the mast)

I have 3 full battens in the jib.

The surface area is = 0.5 * 5,48 * 1,18 + 2/3 * 5.30 * 0.06 = 6.4664 / 2 + 0,212 = 3.2332 + 0,212 = 3.4452 v.m. = 3.45 v.m.

In summary : 3.45 sq. mtrs.

The jib fits very well inside the fore triangle and it alles ample room for the selftacking rail, car and block system.

I would not make the leech bend more towards the mast as the leech is just touching the spreader arms when sailing upwind.

It does look however that the fore triangle will allow a little more luff length and even more leech length than that.

Right now I'm pulling my jib all the way down to the pole so that my 390 mm spreader arms are not poking in my jib, But the standard taipans all have 350 mm spreaders arms. I used to sail with my jib higher on the forestay in the beginning, even 50 or more higher. That is how I know than longer luff/leech lengths are possible. I would not move the leech further back on the penalty to the spreader arms pushing against the leech and disturbing the curvature of the jib there. I would go into details but the pushing action is NOT dependent on spreader arm length.

My advice would be to let the jib move passed the strut all the way down to the spi pole. Have an 5500 mm luff, a 5350 mtr leech and a 1220 mm foot and a concave leech with 0.06 deviation at max ;if you are going to fit a selftacking rail. If not that a longer foot will be necessary to reach the blocks on the mainbeam.

I hope this helps,


Wouter

hi wouter!

thank you very much!

very detailed and very helpful answer! specialy mentioning the spreaders is an issue we did not really think about!

I am alittle surprised by you luff lenght, as we measured something around 5.10 m from the jib halyard block at the mast till the point where the conventional triangle starts and the additional distance to the spinnaker pole varies between 30-40 cm depending on what boat, so basically if we leave a margin of 10 cm we have no more space than 5.30-5.40 m... I am amazed that with a luff lenght of 5.48m you was still able to set up the jib 10 cm higher!!??

anyhow, I think this measure we have to adapt to what we have measured and the other suggestions given regarding base and details we will consider!

If anyone has simular or very different numbers, please let us know!

regards

dirk

Dirk,

I feel that your measurement is incorrect.

I reach this conclusion buy looking at the data I know about the Taipan design. I've also quickly remeasured my jib for you, read on. My halyard block for the jib is on a little pigtale that is 150 mm long. The pigtale is actually just the forestay wire that has been run through the thimble (eye) that takes the hound shackle and that has not been cut of near the thimble but has been allowed run down and end in it own thimble.

Pretty much the hound fitting if 6050 mm above the mainbeam (mast 6000 mm mast foot being 45 mm and base section being 5 mm high)

The bridle fittings on a Taipan are at least 1.30 mtr. in front of the mainbeam. This makes for a 6188 mm distance between the hound fitting and the virtual horizontal line connecting the bridle fittings if the mast is prefectly straight up, which it really isn't (there is noticeable rake there). This length is taken up by about 650 mm of the bridle strop (Bridle triangle) leaving still at least some 5538 mm for the forestay length itself. On my boat the top of the mainbeam is about 65 mm higher then the bridle fitting tops. But indeed my mainbeam was raised by 25 mm relative to the standard Taipan. But still this will add about 40 mm to the forestay length, making it (on the Standard Taipan) 5580 mm if the mast is straight up. By raking the mast back by 700 mm (pretty normal for a Taipan) you gain another 100 mm on the forestay, arriving at 5680 mm in total between bridle strop and hound fitting. My pole sits 350 mm below the bridle strop leaving only 5480 - 350 mm = 5130 of the jib to sit on the forestay allowing some 5680-5130 = 550 mm = say 500 mm distance between the hound fitting and the top of the jib.

And that is exactly how it looks on the pics of my boat. I will post a couple of them. Please note that my bridle strop is actually at 700 mm up from the bridle fitting on the hull. I increased the strop height as my boat is wider than the standard Taipan 4.9 and I wanted to maintain the garanteed angle of the bridle force on my bows.


I've taken out my jib from its bag layed it out flat in my room and quickly remeasured it. Note that the data given earlier was all measured when the luff was pulled very tight to take all wrinkles and stretch out. The quick remeasuring came out at 5430 mm. 50 mm shorter then when measured with a good deal of tension on the luff. The luff was fully untensioned this time. I'm absolutely convinced that I can pull the addition 50 mm out of it with some normal tension. Note that this is the exact same jib as shown in the pics below.

Especially when looking at the pic on the bottom it is quite clear how much margin there still is near the hound fitting. Either I'm making a huge blunder somewhere or the Taipan fore triangle with spi pole strut will take 5500 mm luff, 3.5 sq. mtr. selftacking jib.

I would venture to suggest that you check your measurements. Somewhere there is a mistake, will be interesting to find out where.


Here as I was using it in april 2004 : relatively high on the forestay, see the space between foot and spi pole




Here as I'm using it right now (and during 2005), tack corner is much closer to the spi pole. It is actually almost right on it but I've already detached it here so the wind is blowing the tack back and away from the spi pole



Wouter

.

I'm leaving the jib lay on my floor for now so I can remeasure anything you want on the jib. That is as long as you keep it simple. I would like to roll it up and put it back in its back by wednesday.

Wouter

hi wouter,

many thanks again for your intense support and help!

I think the difference in size we measured is based that we measured the distance by hoisting a rope to our current jib-topblock (which indeed is significantly several cm below the mainmastfitting) till down to where the spinnaker pole sits and measured the legth inbetween. we measured this distance twice.

i think (not sure I understood all your explenations, but will reread it with more time tonight) you top-solution might be difference... still your images are quite convincing...

anyhow, I think you can empty your floor again :-) as I don't think we need more data from your jib!

after seeing you fullbattened triradial cut mylar jib, do you think a crosscut dacron jib, not fully battened can also do the job [surely less optimal] or are all selftacking jibs fullbattened nowadays?

regards

dirk

You are very welcome Dirk. I love technical boat talk. I'm looking forward to having alot more time to do that when my time as chairman has passed. Won't be long now.





Roger.





All racing selftacking jibs are fully battened and nowadays. But I really believe that a cross cut jib without battens can be made to work well. After all the F18's are still using jibs like these as they are not allowed to have fully battened jibs. Although more and more F18's are using pentex and mylar now. Personally I believe dacron to be the better material for a jib when not fully battened jib and jibs without a selftacking rail. These jib do flap about more and dacron is far more resistent to that abuse. With the introduction of fully selftacking systems and fully battened jibs the jibs hardly flap at all and so laminated that delaminate quickly when left flapping can now be used with good life expectencies. That is about it.

I'm convinced that performance from a jib comes 80 % from its luff curve with 17 % coming from the draft placement and the shape of the leech, foot etc. The remaining 3% is material, diagonal cut etc. A good dacron jib should be able to get 95 or 97 % or the mylar jib performance when it is still relatively new. Cross cut maybe a little less but hardly noticeably. I would just go for and get a dacron cross cut jib sheeted of the main beam. Your preformance increase from having a clear tramp will more then make up for the lost drive. If you go with a selftacker rail (I know a few ways to make one yourself out of a square tube of aluminium, a stainless steel plate, 2 pins, 4 small plastic disks and 4 bolts. ) then the performance gain of not having to mind the jib at all will make you noticeable faster in manouvres, sufficiently so to compete for any loses that are incurred by having a dacron cross cut jib. Go for it and feed your experiences back into this forum and the F16 class.

Wouter

Dirk, why do you consider a non-battened jib? Adding batten pockets is easy and cheap. I would not go without battens if I could add them.
If you are going to do this at home, and use a crosscut layout, it's fast and easy to use the cloth overlap between panels as batten pockets. Instead of 10 or 20mm seam allowance, you use e.g 55mm for a 30mm batten.

There is special dacron cloth for high-aspect ratio crosscut sails available, but the sail will not be as stable as a tri-radial layout is. There is also mylar cloth available (Maxx from Contender) with fiber reinforcements especially developed for cross cut. It's pricey, but easy to work with and the resulting sail is stable and nice.

There is a performance loss in going for a cross-cut layout, there is also a loss in choosing the wrong cloth whatever the layout of panels in a sail. The question is what recourses you have available and at what level you are racing/sailing. For club racing, crosscut and dacron can be perfectly OK. But I would not have gone to the nationals or an international event with a crosscut sail if I had serious intentions.

You would do well to add a selftacker, thats a real improvement in boathandling. If you are going for a non-overlapping jib, I would definately add the selftacker!


Just for fun, I entered the measurements Wouter gave into Sailcut, scaled down the luff curve from our Tornado jib and gave it a 10% draft. Sailcut calculated surface area to be 3.32m2. The file is available for download if you want to play with it.
http://www.tornado-norge.org/sails/F16-jib-24-01-06.saildef
http://www.tornado-norge.org/sails/F16-jib-24-01-06.dxf

Wouter,

I am very interested in what ideas you have for building a selftacker setup out of aluminium square tubing. I have a friend with zero budget who wants to upgrade his classic Tornado, and I am due for a new selftacker myself.

rolf, I agree we also would appreciate Wouters creativity :-)

2.
regarding the jib, tanks very much, rolf! would it also be possible to give me a dxf file with a crosscut jib layout?

3.
what is yet not clear picture to me is what kind of drawing and measurement now a sailmaker [persumably not working with a pc and cutting by hand] would actually need to produce such a sail?

Dirk,

Of course I can fix a DXF with a crosscut layout instead, no problem. But if you are going to make a sail from it, I would like to have a look at the luff once more, as I suspect that the percentwise length of the forestay/compression strut is different between the Tornado and the F-16's.

Sailcut can output a manual cutsheet. That is some sheets with X-Y coordinates that describes the different outlines of the panels. Connect the points with a fair line (using a batten), and you get the line you cut to. It's fairly straight forward once you get to it. Build a table of 1.5m by 3m and make a large carpenters square with the vertical edge longer than the width of your cloth. Tape a measurement tape to the vertical edge, and another tape along the bottom edge of the table, and you can relatively fast plot crosscut panels.

A sailmaker should be able to build you some decent sails without much help
Seriously, with the cutsheets he can not do too large mistakes. If he is more enterprising, he just need some pointers to the luff curve and depth (-1.1% at 70% up, 10% depth at 34% was what I used), the rest is relatively straight forward if supplied with measurements of the basic geometry. With that information, he should be able to build a sail using his regular lofting technique.

hi rolf,

finally we found a sailmaker in HK and will build a first jib.

I tried with sailmaker but still seems i miss certain informations.

can you provide your sailcut drawing (*.sc3-file) you once produced?

thanks a lot!

regards

dirk

Dirk, the *.sc3 files are for SailCut v.3, which is an older version than the one I am using. If you download SailCut CAD from http://sourceforge.net/projects/sailcut/ I can send you the design file.