Wednesday, July 24, 2013

Where the rg65 at?

The idea to have the rg65 in the water by this weekend fell into water, because of the KARO riggs...
But the project is making some progress:
this finnbox is made of 1x80g carbon, 1mm balsa and 1x80g carbon + 1x25g glass sandwich

this is the switch/battery/reciever lid, the yellow thing is the thread, the hole on the red lid itself will be covered by a patch to save weight

this is the 1gram rudder mount
this is the current state of the hull, the finnbox is aligned, the pen will be replaced by an aluminum tube, glued in at a 5 degree rake, this will be the fixed mast rake for this boat.

Tommorow's plan is to make the sheeting servo mount(it will be mounted behind the finnbox laying down), the radiogear tray and glue on the deck, the mast tube will be glued afterwards.

Friday, July 19, 2013

KARO, the big rigg

The biggest rigg since my footy affair was tested, it is a 2000sqcm rigg, the mast height is 75 cm, the AR of the main sail is somewhere around 2.6 and jib AR is 3.

the vang is simplified as much as possible, 4 hole tensioners were made because three hole ones(both made of 2mm plexi glass) were releasing tension

The problem to solve is the mast crane, it is preventing the upper 3-4cms of sail to open properly

Today i was sailing on the pond in the park, where shifty conditions prevail. Acceleretaion of the boat is nearly instant, upwind there is a bit of weatherhelm, maybe too much for my taste but totaly sailable.The mast has to be bend forward as the luff pocket on the main has no curve. Heeling is logically increased with the sailarea, but the boat handles it well, the problem is the vertical downforce sinking the boat alot, thats about 4cm at bow, sort of increasing the displacement drastically, i will write more about that in the upcoming hull design post. Nosediving, today some 10+ knot gusts were present and it seems that the classic rigg only sinks the bow to a certain degree and no more, and thats superb! it means that i can easily sail a heavily overpowered footy.
Below is a crappy clip, the white sails and the bright sun make the phone to over-expose the boat...

The plan for the weekend is to make a new main with a shorter foot, reducing the weather helm.
And testing the big rigg in real(not so pondy, shifty and unfair)conditions to se the real performance.

Wednesday, July 17, 2013

Riggs, high aspect

Today the new main was tested, even with no comparison to other boats the difference was obvious.
The rudder was way more responsive, it is really touchy now.
After a tack the boats gets to speed alot quicker.
Now the boat also sails itself, with less side force aft of the mast(from a wide sail with little twist) it reads the gusts better as it heels and speed increases, instead of pushing the boat sideways.
this is the best trim i found
The main is set quite flat but twists under gusts
Here is quick clip

So far so good!
I am happy with the current rigg, but if there is less than 7-8 knots of constant wind this 540g KARO is underpowered with 1300cm2 of sail.
Below is a sketch of the bigger rigg, drawn in the same way as the ICE/BUG/AWK riggs are.
But as i always get such good results with higher AR sails this won't be the new rigg.
Instead a 2000cm2 rigg with an AR of 2.5 or higher will be introduced.(stollery main AR: 2.0)

Tuesday, July 16, 2013

Footy, rigg evolution, step 2

Over the past days i've been sailing the re-rigged karo, sadly noone who can sail and lives close by is available at the moment to do a rigg comparison.
Some good progress has been made tho.
On the photo is the rigg as sailed, the total surface is now 1300cm2, a new jib was introduced with a higher aspect ratio, and made of icarex, it can be easily set up to have good twist, and pull the boat through the waves and downwind.
The low aspect main is the current inconvinience. It must be set with quite alot of twist, to get the boat moving(at least that's how it appears to be done on the ice boats) but if i set it like that the boat looses angle upwind, if it's set like on the photo above(less twist) leeway increases..
the two photos above have the same setting.

This is the best setting i have found, giving the main quite alot of belly helps  it to twist giving the best speed/angle compromise, or at least so it seems

Below some more photos:

the classic rigg sinks the boat and drags it alog, the rudder rarelly comes out of the water, when running una riggs the rudder was allover the air.
This is about as nose down as the karo will go with this rigg
Here are a the clips, sailing with different settings:

Tomorrow's plan is to test the new higher AR main(has the same area, but the CE raises for 5cm with this sail):

Here the difference between the new main and a Stollerymain can be seen

I expect it to give less leeway, and produce more speed: so sheeting out and bearing away after a tack can be reduced, as it was with the introduction of high AR unarigs my footys have been using until now.

Thursday, July 11, 2013

Karo, rigg evolution

After returning from the footy goldcup i was super inspired, went straight to work, improving the Karo.
(I will write my report on the race as soon as i can catch my father for the photos)

In france i realized that the next step in my footy development will be a new type of rigg.
My unariggs had some drawbacks, which became visible on the race course, sailing against other boats and in "crowdy" conditions.

The first was that my higher aspect ratios did not carry as much sail as competitors with two sails, they produce the same speed, but don't accelerate the boat as quickly as a classic rigg does.
The centre of effort is higher, so the single high sail provides quite a lot of heel.

The second thing was they were to stiff, sort of hammering the boat when not under power, and loosing speed through tacks, so a softer material has to be found

The third thing was the damn backstay, i got caught numerous times while sailing at the front of the fleet or at start.

On the way back I went through the sketches i had made for the classic rigg.

Today the rigg was finished, it has funny geometry, sporting a Stollery mainsail, and a 450cm2 jib, with a combined area of 1400cm2.

The mainsail is made of icarex, kite material. For now the jib is kimoto foil(it is to stiff)
The main thing is no backstay, i am sure that the chance of getting tangeld with the shrouds is way smaller, on this rigg they provide forestay tension.

The main benefit is probably lowering the CE for 12cm.  
The jib was provisorically attached, so i could take the boat for a spin, a removable swivel will be introduced so jibs can be raplaced easily.
Todays impression was superb, i managed to put the overall CE about 2cm further behind than with the unarigg. The boat sails way more responsively than before, and nosediving seems to be reduced.
For the first try the performance is very satisfying.
Tomorrow i plan on taking both Karos to the pond, and hopefully finding someone to sail one of them for comparison.
Clips follow.

The plans for this rigg:
1. Make a 1800cm2 version
2. Make a 1000cm2 version
3. Compare on water performance to the unariggs
4. try:  moving mast aft & changing sailarea ratios(bigger % jib),  getting lift from the jib

I will put down my thoughts about the new hull design in another post.

Friday, July 5, 2013

Off to Le Havre for footy gold cup

Yesterday we set sail via our car from home(maribor, Slo) to france. The 13h drive went smoothly.
My father and i will be sailing at the footy gold cup. My mother who came as a turist will be sightseeing, and my girlfriend had to stay at home for some exams, sadly.
At 7pm today we threw the footys into the water and started sailing with the italians.(the two Steri footys)
In a dying breeze i was struggling to keep up with their bigger sails, but managed to, hardly tho.
But more wind is to come for tomorrows racing, and windy days are what karo was build for and performs best in.

Monday, July 1, 2013

KARO performing

Today the wind seemed strong enough for a C-rigg party, sadly it wasn't strong enough so b rigg and  later a rigg were sailed.
I took the black boat to the pond, this is SLO 03 the boat i will be sailing at le Havre in 4 days.
My girlfriend was escorting me, taking pictures and sunbathing.
Anyway here are the clips:


overpowered a rigg

On the last clip the boat was seriously overpowered but the tip of the long rudder remains in the water to provide enough control.
I really like how the boat sails upwind when heeled. It is very well balanced, going over the waves in a steadily oscilating motion combined with responsive rudder control, the boat gives a reliable feel and very fine corrections are possible. Other than that it goes upwind more or less neutral, but still "reading" the gusts.
Tacks are super snappy, but can be also slow, carrying the speed trough.
To sum up the photos,
1. it seems that the vertical downforce created by the sails is very large for footys, as the boat goes sort of submarine upwind. Spade the old model suffered of this phenomena greatly, and even KARO with lots of reserve volume seems to get pushed down by the sails. But making up the needed extra volume would be irracional as the hull would get somehow to big.
2. The boat still has no bow bumper.
3. Sailing upwind the bow picks up water(photos 3, 4). That is uneccessary, for the future developments a , chine or perhaps a deflector should be introduced, such a device has to be located as close to the waterline as posibble, not to increase the air drag(note: the wave drag should be taken into acount)
4. Sailing downwind, a huge depression is created when the bow is pushed into the water(can be seen on older posts). This depression is no good for drag. My thoughts are to narrow the bow, but that would mean taking away lots of necessary volume. I guess a depron prototype is the way to try out a narrow bow.

BUT, in footys we have an unlimited supply of power(sail area is not restricted) the challange is to deliver that power to the hull in a proper way.

An una-rigg is definetly not the way.(although it brings the boat up to hullspeed, it can't surpass it)

It has a big forward force component, high above the deck, which results in a big leaver pushing the bow down(sort of rotating the boat).
I tried 200g ballasts in the stern and it won't help(ofcourse not the sail force must be bigger, and a simple calculation proves that) the best trick is to add a lot of volume in the front(like british ice, ant, supabug footys), or devise a high piercing bow(like sui 42 "BOX", or "breithorn" and karo), it's also much easier to add 200cm3 of volume to the hull, than to put 200 extra grams on a boat that has to be balanced.

British ices run a very thin mast wich bends alot(even downwind) depowering the sails. but the rotating force remains.
The una riggs are a good compromise for upwind performance, as they provide little drag, the mast bends to depower the sail.

The future riggs are delta and classic riggs, if enough lift can be gotten. The challange will be creating more lift, than drive, and being able to have sails that will be able to produce enough drive for upwind sailing.

There is still much more to say about the riggs. Maybe more next time.