There seems little advantage in using the main sheet last bit of travel to tighten the main leach vs presetting the vang.
Several reasons, but main one is that the vang needs to be quite firm at close hauled for correct twist as the main tends to twist a bit more open as the sheet goes to full out (caused by the pressure changes on the rig going down wind). If the vang is not at correct setting for close hauled, it will be too open for offwind. So the vang should already be at the max desired setting, and there should be no need to go even tighter on the leach (from the main sheet).
Other reason is that main twist is a very critical setting and you cannot see it accurately enough while sailing to have it adjustable, via the main sheet. Better to set it up on shore with the vang, and adjust the vang between races for fine tuning.
Using a servo controlled traveller that can be hitched up to weather is a do-able option on classes that allow it. But the sheeting post is lighter, easier (KISS at work).
The main sheeting position is determined by adding a certain percentage to the radius of the jib sheeting position.
Personally, I am very happy with the position as it has the perfect balance between sheeting speed and ability to control the main twist.
There is enough power in the winch to close the leach even with the sheeting position as it is.
Small step closer… laced up the rig and testing a new prototype rigging material… Spectra.
Early days yet but the whole rig is rigged with composites. Forestay is technora, shrouds and backstay in spectra.
0.3mm and 45kg breaking strain are pretty impressive stats.
If you do go down this road, make sure your yacht is stiff… I had to tension this baby a heck of a lot more than wire… but doing so removes the initial stretch and once that is gone the shrouds perform better than wire, well 0.3mm wire would have busted long ago.
The second picture shows the top of the rig lays off nicely which will open the head of the main and de-power in the gusts.
The last shows the backstay attachment, using the compression tube as the ‘dog bone’.
Looking forward to the road test…
I have been experimenting with an “offset” in my vang, to compensate for the mast prebend I use. You set the vang tension to get the amount of leech tension you want when going DOWNWIND. Then adjust the ANGLE of the vang/gooseneck to get the amount of leech tension you want when going UPWIND. I have used spacers between the mast and vang mounting at the boom to make the vang softer as the boom goes out, and the spacer at the bottom to make the leech tighter as the boom goes out. On my small boat, the vang/gooseneck is epoxied in place with a slight angle permanently fixed.
I have even seen some assemblies that are screw adjustable to set the angle. This could be particularly useful with a rectangular mast section that is stiffer fore and aft than it is sideways. It will need more vang as the boom goes out and the top of the mast falls off and slackens the leech, especially when the wind speed varies.
I Have a couple more pictures to add, The boom is nearly finished, all carbon with titanium vang…
Thanks for the suggestion Hew, but I had already come some way with the current arrangement, so I will see how this goes.
I have plans for a second ‘race boom’ One that looks like a space frame!.. so any mods will be included in that.
Wow I think I understood maybe 25% of all that. I suspect someday when I get my boat on the water, I will end up with a floppy mis-shapen sail that moves the boat at about 1/2 knot. How discouraging.
I just thought it was really cool the way Jim’s boom vang nut was built in to the boom itself. Nice.
I’ve been fooling with these for a couple of years and am just getting some ideas. The speed differences are really pretty minor, and can be made up with good driving and going “the right way”. Of course a slower boat that goes the wrong way too… I’ve been there also!
I wouldn’t worry, this is the first time I have experimented with a self adjusting cunningham as well & thanks for the complement on the vang adjuster.
Its another KISS = lightweight approach! No point in getting too complicated.
I bought the Ti rod on eBay for €1.50 and modded it with a Ti fastner and a Delrin thumbwheel I spun up on the lathe.
You are doing a great work!
Have a precise idea regard the final weight ready to sail with all accesories, including paint and decals?
Have you chosen the sindicate? Desafio?
Absolutely I know the final weight - 4501g!.. But I’m guessing you want to know the weight before correctors?
Perhaps you can tell me how much correction is in SUI102?
I will weigh the yacht in its sailing configuration tomorrow. Before I do I know its not quite as light as I intended because I chose to take a weight penalty painting using epoxy based paint instead of aerosol’s. +175g but this will be the last model yacht I will build for a while now so I wanted to have a showpiece as well. before paint and with everything on the yacht I just weighed in around 4050g ish…
She is a copy of her big sister SWE 96, so mine will bear that sail number and hopefully the 2007 Louis Vuitton challenger series hull graphics/sail logos,
The last piece of the jigsaw was collected today from the post office, the batteries are on charge and all being well I might get the maiden voyage in tomorrow
This is how close!..
Just got to put in the new steering servo, fix in the access hatch and finish the sheeting.
Just hoping for a nice day with not too much wind!
Thank you for info, I like really A LOT your boat!After this last image, I like also mainsail and rudder shape. The SUI-102 weight it depends on accessories weight (electronic and mainmast principally) and on the lowest configuration ready to sail complite of painting and decals is nearby 4080g, but normally I prefer a much more heavy package so the total weight is higher, I didn’t found real advantage with a very light weight boat, experience has taught me that it is better to have more reliability with a middle weight boat.
I hope to see in Ravenna 2011 or earlier you boat in water!
I have to agree, You could go lighter but in the end the yacht will suffer… Its a shame we cant put all that hard work saving weight back where it should be - in the bulb!
Out of interest what height are the SUI logos on your main… I am trying to figure out a good height for the sail number
The experience in races taught us that if you could choose between two way very very close as performance in water, but one with very expensive boats, high risk of failures or damages cause contact in regatta, or accidental damages, and another way with a very little bit less performances but very cheap boats, strong and enough easy for all to build them, it is better the second way. I think that class to have success need to be inexpensive, nice looking, fast in water, easy to transport and enough technical to be interesting for designer and skippers, and I think that IACC120 is all that.
Well,
Mother nature had the last say… Zero wind today… When the wind blows from the west, the America’s cup basin is totally sheltered…
As a final flourish, and as this boat will be “Swedish”… I placed a 1kr coin in the bottom of the yacht. This is an old tradition … no idea why but all I know is that if you want to win, you need a coin!
I did a refit on The Stenbeck modern six meter and placed a 50 ore coin under the mast step, and she 1st won the Worlds 2009, then the Europeans 2010. I get a kick out of a multi millionaire getting luck from the lowest denomination coin Sweden has to offer.
I was able to do a float test and that was it… Gutted! But I did weigh the new girl right before.
4175g in a ready to go, sailing state…
Got to say that I am happy, it looks great just sat there and I don’t feel embarrassed to show it to anyone. I love knowing it looks 100%
Cant wait for some breeze now!
Hi Mattias,
The reason is -
The 1050g was the best estimated weight before paint…
Then, I chose to take a weight penalty by using epoxy based paints (175g). I know this because I weighed the yacht before and after painting.
I will be wet sanding the hull at some stage which will liberate a few g’s, and I will also remove the adjustable jib track recess once I have found the race mode for the yacht… There is some “dieting” still to happen like a space frame race boom etc…
That’s what is great about this class… Its limits are your imagination. (and that damn 3000kg max fin & bulb weight…)
Vids and pics will indeed follow!
Weather still not looking that great for the next few days either, maybe a window for ‘dock off’ tomorrow around 18:00 as long as the light lasts.
Cheers, Jim
