Tuesday, November 27, 2012

Jacta est alea

Supposedly said by Julius Caesar on January 10, 49 BC when he crossed the river Rubicon to start the war against Pompeius. Today repeated by yours sincerely as I cut the bow off Panta Rei's starboard float.

The bow bulkhead's position was established by palpatory percussion and measurement from the beam bulkhead.  Then I drilled holes safely forward of the bulkhead to establish it's exact location.

Then I drew a line and cut the float in halves.  OUCH!

Showing current and suggested new surface contour at this location

Starting to build up a new foam blank for the elongated plumb bow.  Old and new, side by side

I've calculated the added volume from bow bulkhead to beam bulkhead to be approximately 26 litres.  I have to look closer at the difference between the two foam caps, but the added length alone should give more than 10 litres.

Saturday, November 24, 2012

Main sheet mods

I had the recommended 6:1/24:1 main sheet.  I used the Ronstan system main sheet #12. I've used a 10mm triple braid for coarse and 8mm for fine.  My focus at the time of purchase was grip and the hand of the line.  There is a lot of friction in the lines and I will change to thinner lines for that reason, at least the coarse.

I would wish for a bit more power on the coarse.  The fine has plenty of power, but very little travel.

Today I added a block to get 7:1 coarse, left the fine so 28:1 fine.  Usual crossing lines as the triples make.  I had a 50 kg load that was not able to let the line out because of friction.

After studying this set up for a while I got an idea and threaded it again. Voila! The twist was gone. No scientific results, but it felt lighter.  I also went down to 3:1 for the fine.  Will have to replace the 40 double with a single with becket. And a thinner line and I guess I'll be there.  7:1/21:1 it is now.

Mini trailer

I made this trailer to move the main hull from the road trailer to the workshop.  There is a few metres from the main gate to the workshop where there is not room to manoeuvre the road trailer.

Canting rig

The idea with a canting rig is to keep the forces from the rig working horizontal, and thus prevent the downward force created from a heeled rig.  I contacted John Franta at Colligo Marine for suggestions on the cleanest, lightest installation.

This is his suggestion:

" We have done a couple of systems now with our double static block purchase system using 5 mm dux as the running line. This is on a 44 foot Chris White Trimaran.  They claim 1-2 knots more speed from it!  It uses a safety line spliced between the chainplate distributor and the line terminator to limit travel. 
This is probably how I would do yours, lightest system you can get.  I would run the line back to the cockpit to a clutch  on each side."
I don't think I have the space for the lying cascade, not on deck anyway, but I have not got to this yet.  Anyway, a system in this direction is what I will go for.

Friday, November 23, 2012

Sailing characteristics, now what?

So, should I do something to the boat as a consequence of what I've learned?

In light air, I can not see room for any improvements, except perhaps that a partially deployed lifting foil would improve helm balance under screacher. And keeping the weight low would probably be crucial.

Upwind, the boat tends to sit on it's stern.  This is, as I have seen it from postings on the forum, a well known characteristic of the Farriers and the remedy is to move crew forward, especially in lighter wind. I think that a longer float stern, with a bit less rocker would also improve this aspect.  All in all the boat behaves and performs very well upwind.

As I mentioned in my previous post, reaching is where improvements can be made. Again, the boat is very stable and safe as long as the speed is kept under 15 -17 knots or so, but when pushing hard, more longitudinal stability is desired.

1. Water ballast.
It should be room for about 50 litres of sea water under the swim step.  This would be equal or better than one extra crew on the aft beam, and I expect this will be of significance.  I've never used any water ballast system, and can not really imagine how to operate it.  Farrier says "Fairly simple to do, by just using dinghy bailers",

but this do not make me any wiser.  I don't want to disturb him more than necessary in this stage of his production set up either.   It seems to me that such a bailer would have to be operated from inside the tank, and then it do not fit my perception of fairly simple.  Any tips/suggestions/experience with such systems are very welcome!

2. Lifting foils.
This would obviously be a nice feature.  Downsides would be weight, cost, one more thing to operate. The advantage seems, from reports from the Dutch F-32SRC, obvious, and just in the conditions I want it.
Ian will make me foils and cases, but with shipping and Norwegian taxes this will be a considerable expense.  Designing lifting foils by my self is a very uncertain project with respect to efficiency, and with the demand of accuracy in the building process in such parts, the production will be time consuming and expensive.  Jury still out on this, but if I add foils, it will be Ian's.

3. Modification to float shape.
As I had these damages to the port float, with cracks/holes in the outer laminate at at least seven places, repairs and re-fairing/re-painting of this float has to be done anyway.  Also, last year I rebuilt the net support, and this will also be happy with a round of fairing/painting.

Which have led me to start playing around with the float shape.  To be able to put any useful volume in, I find it necessary to lengthen the floats to match the main hull.  Also, make plumb bows.  Here is one suggestion, also showing my bow art

And a bit refined, with more rounded top, and also planning to add a 40mm thick rounded deck forward of the forward horn cleat, and make sure the shape will easily get back up when submerged.

The challenge here is to make modifications to improve what I want changes to, but leave the things that work very well as is.  This means no volume added all the way down, as this is what is used in light airs.  Then, when moderately pressed on a reach add all the volume possible, but not necessarily so when pressed upwind.  So, obviously impossible to get totally right.  I might end up having to add a bit at the stern as well to keep the balance right. This will also give more longitudinal righting moment, but possibly lead to a bit adverse effect on wave handling.

Possible modification of stern keel line

Here are some ideas as to where to add volume:

The bow bulkhead cross section.  10mm of foam to be added to the shape on the original plan, to the left the suggested surface shape at that station. I have not yet been able to calculate how much volume added this will be.  Did some rough calculations this afternoon, and it seems that 20 litres in the front two feet is very realistic.

Tuesday, November 20, 2012

Analysis of the sailing characteristics of the F-22RC with huge wing mast

So, I've got to sail the boat a bit now, in different conditions.  Not yet in really heavy weather, I prefer not to when possible.  Winds up to about 25-28 knots, seas up to maybe 8 - 10 feet.

I must say I am really happy with the boat.  My previous experience with multis is the old Telstar 26, the F-22 being a metre shorter, half the weight and still handles seas far better in my opinion, and of course - is a LOT faster.  The R rig is very powerful, which is very welcome in the usual 3-4 knots summer conditions, but also have to be used with care (read reefed) when the typical changing conditions in the fall dominates, or - having an experienced crew.  The latter is a problem that I'm constantly working on.  In order to do well  racing I need to have crew that know the boat.

The large mast makes a lot of difference on a bit wider angles, don't think it is a major advantage going upwind.  However, it helps produce power in light airs and choppy conditions upwind as well.

Upwind:  Under main and jib it comes alive and gives the big monos (35 - 40 ft) a fight around 12 knots of wind.  You can carry full sails up to over 20 as it is just to turn a bit up in the gusts.  Boat speed in these conditions 10 -12 knots, pointing at least 45 to true wind.  Main hull will barely touch the water which makes the ride smooth and dry (all is relative).

Reaching: Now this is the really fun part. And scary.
The boat will quite easily reach speeds of 120% of wind speed. Due to the high boat speed, it soon becomes over powered in conditions when sailing upwind is just fine.  I have reached main only in about 20 knot wind in excess of 18 knot boat speed.  Single reefed main and jib with crew of four 22,5 knot boat speed.  Crew of three and I have not dared to go further than about 19 knots.
The thing is I do not run out of pedal, but I run out of longitudinal stability.  I think these speeds are pushing the limits for what the boat was designed to do. It could probably have been pushed harder, but I like to have a bit of margin, and after experiencing the lee float deck going down and effectively throwing the brakes on a couple of times makes me hold on to that idea.
This is also where my huge mast section comes in to play, giving a lot of driving force combined with that much better aerodynamic properties than a conventional spreader mast, turning up the lift/drag ratio of the rig and demanding even more longitudinal stability from the platform.
I've discussed this with Ian a bit, and he suggests putting in water ballast, which I will do, and he has offered to make an F-22 customised set of the F-32 lifting foils.  I really want the foils, but don't think I can afford them at this time.

Downwind:  In almost any wind it seems to be the fastest to sail almost accurately 90 deg to relative wind.  this gives a boatspeed equal to the wind speed and let me gybe trough 90 degrees.  You can comfortably sail 15 knots under spinnaker for long periods. I have had the spin up in close to 20 knots of wind, but then it feels better to go a bit deeper.

Film for sailing nerds

During the last sail of this season, the "Ulabrand regatta", we had a small camera mounted to the tiller.  The wind was from nothing to about 25 knots, boat speed between nothing and 17 knots.  After turning down to a reach after one of the upwind marks, we got seriously overpowered and turned in to survival mode for a while, and did not dare to get up across "the line" until we had double reef.

This is 13 minutes of the 2 hour sailing, the whole chaotic bit with reefing and turning downwind is there for educational purposes.  In hindsight, we would probably have managed well on the reach just moving all crew aft, travelled down and perhaps rolling in the jib.

Back in the workshop

After the damages late this summer, it is necessary to make some proper repairs.  To do this I found it necessary to demount the boat and bring it back in to the workshop.