Bonus photos of evolution

more & more &more = same as before

I spent one of the last "holiday" days sailing evolution, with a rigg, in conditions above the riggs range(10-15 knots). Hiding behind a dock, where the wave was relatively small.
The reason for sailing in in a windy but waveless spot was to observe,by eye, the behaviour of the boat under lots/excessive power.
By eye it seemed that upwind the boat would sail just as fast as it would with a well trimmed b rigg, perhaps there was more drift. But i think that the same boat with both riggs would perform identically.
Downwind the boat sails fast, but even at top speed the sails stayed tense, full. Delivering power that was lost because the boat would not accelerate more.

I was pushing the a rigg to the limit.
What is this "limit"?
This is a wavemaking drag barrier.
According to mr. Edmond Bruce, author of "design for fast sailing" by AYRS, the wavemaking resistance barrier, displacement boats face when sailing close to hullspeed, is less noticable when Lenght/beam ratio of a slender hull reaches 8. This "barrier", or a steep hill in the wavemaking resistance ploted against speed graph almost disappears when a hull reaches l/b=11.

I will use this post to go back to basics and come up with two ideas for future F5g boats.
Both ideas have been realised in the "big boat" world but have not been pushed to such extremes due to structural and seaworthiness limitations.

The goal is to make a fast boat.

In order to make a fast boat we need a force to move the boat.
Here the rule is simple, the more power(sailarea) a boat has, the faster it will go.

Some will argue that if the sails are more efficient a boat with less sail will sail just as fast as boat with more less efficient sailarea. Wing theory proves that, but in the real world a boat with more sail will be the first to start reacting to wind, if there is little wind. A boat with more sailarea has more tourque powering(moving is perhaps a better term) it through waves. The boat with more sail can take the wind from the boat with less sail etc.
The above are race proven facts that are true most of the time on a race course. But there are some drawbacks of carrying lots of sails.
Since we are talking about model boats that measure less than one metre in lenght, longitudinal stability is an issue. Our models tend to sink the bow, submarine so to say. Footys and IOM boat suffer from this greatly. In f5g i have succesfuly adressed this issue with a foil attached to the rudder, the foil is inverted, so it is pulling the stern into the water.
Yes this foil increases wetted surface and induced drag, but the area of sail i can carry with this rudder is much much bigger. Example: Fila has a5500cm2 a rigg, without the foil it can carry its rigg to about 8-9knots of wind(average wind) with the foil i sailed downwind succesfully in winds of 14-15konts! Evolution can sail with more than 6000cm2 up to 15knots of wind!(it has more bow-volume and a longer keel than fila)
The second issue is transverse stability. With no moving ballasts the most effective combination is a wide hull and a long keel. The combination of both gives the boat a satisfactory counter-heeling moment.
Big sailarea requires a wide hull and/or a hevy bulb. We can fine tune this combination to give good results with the chosen sailarea.
Until now i have never asked myself how wide can a monohull be? The idea of a 750mm 400mm wide F5g scow type yacht is interesting, but hullweight will probably be the downfall of this project.
The problem with wide hulls is that they all make a deep/high wave, causing a lot of distortion over a large area. Despite the consequental high allup weight such a boat could carry lots of sails and putt other f5g boats in shade. Planning potential downwind would be good, but upwind under heel it would not sail past hull speed leaving it just in front of the rest of the fleet.

Without moving ballast i can't see another way around this dragbarrier problem caused by normal displacement hulls of our model boats.

With an aerial canting keel/ballast arm and a narrow hull with a l/b ratio of 11, the boat could reach it's speed potential. The arm extending to windward would keep it right side up sailing upwind.
A rudder foil would keep it from digging in when running. Transverse stability downwind is a challenge. Sailing downwind the arm would be recracted to the middle of the boat so that the CG of the boat be about 10% behind the LCB, this gives good rudder response and keeps the bow from dragging too much. But the ballast would be placed relatively high, on the deck.
A gyro stabilisation for downwind sailing would be needed. Or capsizes would be inevitable unless some lead would be put into the keelfinn, which has to be present anyway(not really, a fore rudder could replace it, but for regata use a fore rudder is one channel to much for my concentration, and it takes away the good feel of a well balanced boat. Just like 4wheel drive takes away the livelyness of a 2wd car)
If only possible, putting led into the keel and having movable ballast at once should be avoided.
Because if you go through all the trouble of making a movable ballast sistem work, then you want all the ballast you have to be active, for maximum efficiency. The lead in the keel would be dead ballast just sitting there to save the boat from capsizing in extreme conditions.
Dispite the above practicallity along with reliability has to have the upper hand and a boat has to be desingned so that it will complete sailing the course when sailing as hard as required with no technical issues or capsize recoveries.

This was a thought about a fast monohull, to sail in a displacement or semidisplacement mode at planning speeds. For the first time i realized that it is almost a waste of time to work on "classic" type keelboats in an open class like F5g where nearly everything is allowed. IF we take a look at iom or marblehead where the rules are much more defined and refined, well that is another story.

Getting close with Evolution

Still here in Premantura, Croatia.
The wind is ok, up to 8 or 10 knots everyday, the wave is unnoticable.
The conditions are ideal for A-rigg. Thiis are the conditios that f5g boats love.
Since these are very light boats with lots of sail-area they don't really like waves and riggs have to be change quickly.
But I desing and build my boats to suit in these prevailing conditions here on the croatian an slovene coast.
After three days of focusing on sail trimm Evolution handles like Fila only better. It has slight weather helm and points high, just like Fila. Unlike fila it's cg is far, hydrodinamicaly too far back.
Meaning that the bow likes to clear the waves, the cg position combined with a short distance between the rudder and the keel finn makes the boat happy to tack, and lively and very fun to sail.
It really feels almost skiff-like. The funnest(most fun) rc sailboat i have sailed so far!
The force from the sails seems to put the boat on the predicted waterlines as soon as there is some wind. I light airs this boat Will be probably slow, because the stern is about 7mm under when the boat is static. -as soon as you can feel the wind on your neck and the boat heels it sails beautifully.
It seems that cg far aft is a helpful tool when dealing with a boat whos' waterline is short and caries lots of sails.
to the pictures..

this is the max reasonable heel angle for this boat, above that the deck gets flooded.
That must be more than 30deg, lots of heel for such a wide-ass boat to sail normally

it points really high, with less nose down than fila!

but the wave crest is quite high, this boat definatelly won't exceed the hullspeed by much when saing upwind

the max "resonable" heel angle again, the rudder is getting some air, which offcourse is not good, but even worse the keel is already starting to show. No bubbles seem to travel down the foil..so no ventilation it seems...
the waterline is very narrow and the hull is pretty deep when sailing like this

the boat reaches speeds of up to 5km/h in such conditions with no wave, this seems to be a limit.
the rudder foil keeps the stern down, but if you look closely there is very little water unnderneath it

in a gust it just keeps going, if i don't pull the sheet in the main sail trimm goes shit, like here

too much heel, the back 15cm of the deck is getting washed.. this is a common site on most rc sailboats

when really powered up and pointing high the top of the jb depowers and interestingly the square top of the main starts fluttering so you can hear it.

bearing away...

..foil kicks in when the speed is up, and bow goes up in the next moment

 out

KARO

Karo, my second own design footy survived it's first season.
It posted a good result(7th) at the goldcup, and was the basis for classic rigg development.
It is also my first panel build boat ever, and my first boat intended for easy building(karo is winner of the richardson trophy, an award for simplicity and promotion of fun).
now the black boat was refurbished into it's original/optimised form:

the new 285g bulb seems to work best with the 1500sqcm a rigg

the paint is tired, the hooks for a classic rigg remain on the boat also a new balsa bumper is in place

all up

This is KARO's final shape, it will remain like this.
It's a competitive boat, that is oriented for windy days. I am looking forward to sail her at some future footy regatas.

a complete set of pdf plans will be free to download soon.

proto footy update

The unarigg was moved 2cm forward, now the boat has better helm balance at bigger angles of heel, and is stable while nosediving downwind.
The 200g ballast is a good choice for this hull. but a 250g bullb will be introduced, because bigger riggs(more than 1500cm2) will also be used on this boat.
I also tried it with the 350g bulb of of a KARo, but that was too much, the boat didn't want to heel, and with no grip from the chine leeway increased. Responsivnes was also compromised.
Today the wind went from 2-3 knots to some 7-8, A+ to A rigg conditions.

Autum is in full swing, later the wind blew the leaves away, luckly

The light conditions were just to demanding for my Iphone today

downwind is now stable, this boat does lose more speed than a KARO does when nosediving

reaching is good, even when overpowered.

More conclusions will be drawn when i get a chance to sail against a KARO, or other footys..
here are a couple clips:

and with the 350g bulb:

new footy prototype

Yesterday a new design went waterbourne,

It is a fat design, made out of 4 3mm depron panels for easy building.
It is placed longitudinaly and nose down into the box, 153mm wide at stern and has a 32cm lwl.
The bulb is 200g, total weight is 380g. The updated KARo a rigg is used.

The goal for this boat was to create a light weight(sub400g) boat, which is beamy, with lots of volume, so it can go over the waves(no through them like KARo does), i decided to go for the 4 panels so i can modify the hull quickly, and so that some one will decide to build it cause it is a 4h project if u already have a rigg.
templates follow.

It goes quite good already. I will shift the rigg forward tho for a more neutral helm when heeled(the 12% lead of CE to CLR is not enough, there is some weather helm, too much for my liking. The hull is very stable obviously(lots of volume is shifted forward so the entrance angle is quite bad but that doesn't seem to affect speed.
Upwind the chine bites, and the boat is shaky over the little waves, i don't like that..  ..but it seems faster upwind than a karo. Downwind it has a problem..     ..it is so light that it gets thrown over it's bow and onto its side, it takes too long to get to the old course again..   ..a possible solution to that is a longer rudder. But when not heavily overpowered it goes well.

Tomorrow it will be in the water again with the changes. There are also some leaks that have to be fixed.
After i am happy with the balance upwind and downwind is solved this proto will be taken apart for templates.

clip

New rigg for Fila

After the parts for the rigg were sanded with 600grid paper they were polished

the rigg:

10 grams of weight was added to the mast with new parts, too much, would be better of with a carbon spreader, the main benefit is the reduction in bend.

the mast bends sideways only 2-3 cm when heeled 90 deg wich is alot les compared to previous 7-8cm without the spreader

Triming the main is much easier now that the twist of the sail doesnt increase that much when in a gust

Today i checked all the sistems and marked the basic setup

The telescopic bum enables fast changes to the depth of teh jib

reaching and downwind nothing has changed, the travel of the jib was bang on for butterflies, the jib weight is missing

The 3 points of improvement on this rigg are; easier trimming of the sails, less mast bend sideways(the boat accellerates better upwind), and the looks of the clean design which is to be refined with the mast head improvement and a new main boom, comming in a months time.

Weight of the mast is to be improved, by using a carbon spreader. The lower part of shrouds will be replaced with wire(now 50kg dyneema) because the rostfrei tensioners tend to cut the rope..

The upper seam of the next jib will get some camber(now all seams are flat) to keep the jibs luff abit tighter, now it opens too much under gusts.

I am looking forward to the race on saturday, it is the last race of the season, in case of a win i can win the naitional series, but the number of competitors will play a big role due to the new scoring method.

Flaps on KARO footy and over-powering the a rigg

We had a few days of good wind here in Maribor, SLO.
The wind on the pond in the city park was gusting up to some 10-12knots and shifty.
the trimm, the pivot point of the jib was set 4cm forward.

a crappy clip:

It seems like the vertical down force created by the sails is quite big in relation to the available volume in the hull. The boat gets pushed down upwind.
Obviously a solution for the next evolution of the karo is more volume, but i have also tried flaps below:

The flaps are at an angle which would be considered stupid with normal boats but at footy speed, or at such low renolds numbers it seems to be the most effective, and by eye it doesnt hurt the speed at all!

The flaps help to keep the bow up when over-powered upwind and reduce submarining downwind.
I noticed that leeway was increased with flaps. That was because the flow separated of the flaps and the hull, and then reatached at the end of the first half of the hull.
The midle third of the hull is the part where the chine provides the most "grip" upwind, so i cut the last 3 cms of the flaps, so the flow would separate earlier(from the flaps), and reattach on the hull after the first third so the whole middle third is immersed.

the cut flaps

Below is the clip of sailing with flaps, if the flaps do any good will be confirmed when i get another chance to put both KAROs in the water.