Baltic Circumnavigation

What does your design brief look like? What are your requirements for the boat? What do you want to use it for? What does your budget look like?
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Manik
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Baltic Circumnavigation

Post by Manik » 08 Jun 2016, 13:44

Hey guys,

I've been trying to figure out what kind of vaka to build ever since my project kind of flopped last year. I put a large amount of time into designing a 9.2m vaka which all around, I was really happy with. The problem presented itself though when I did a cost estimate for the boat: it came in at around 12,000€, with the ama and quite a bit of epoxy already on hand (see this post on my blog). So, back to the drawing board -- but first, I need a really clear design brief, so that feature creep doesn't get the better of me again! This topic is all about what I need; ideas on how to address those requirements will come in the 'Concept' thread later on. This thread draws heavily on my earlier design brief here.

The goals / must-haves are as follows:
  1. Single-handed circumnavigation of the Baltic Sea in summertime
  2. Ability to sail it solo non-stop on the way up (I hope it's possible on such a small boat!)
  3. Cost to completion, including equipment: 5000-6000€, or if that's impossible, at least get it to day-sailing state within that budget
  4. Buildable in a garage w/ a temporary extension
  5. Seaworthy enough to survive if caught out
  6. Sitting headroom (i.e. >105cm) when seated on the floor
  7. Sustained average speed of ~80-90NM/day (sailing time: 15-16 h/day)
  8. Avoid having to pay harbor fees (tender maybe?)
  9. Daysailable with 2 people
  10. Suitable for the temperatures of the northern Baltic (summer averages: 10°C water, 15°C air)
  11. Interior which stays dry (spray & condensation)
  12. EPIRB
  13. Basic instruments
Some nice-to-haves:
  1. Camper cruiser for 2 people
  2. Capacity for enough stores for 2 weeks of single-handing
  3. Normal sitting headroom of 135-150cm
  4. Battery, VHF, AIS, solar panels
What I don't need:
  1. Any pretenses of ocean crossing, you need a 35 footer for that
  2. Comfortable interior seating for two
With these requirements in hand, it's clear the boat can't be very large, ~6m to ~9m. Since I only have a garage with a temporary extension as a workshop, keeping construction time low will be very important. I do have a 5.8 meter ama on hand, almost ready.

Cheers,
-- Marco
Last edited by Manik on 13 Jun 2016, 19:37, edited 2 times in total.
"Man's mind and spirit grow with the space in which they are allowed to operate." - Krafft A. Ehricke, rocket pioneer
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Manik
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Re: Baltic Circumnavigation

Post by Manik » 08 Jun 2016, 14:14

I have a provisional mass estimate which allocates 350kg of loading, including the stores, anything and everything that goes into the boat, and my own bodyweight. Do you guys think that's realistic? It seems a bit light to me, others have said to me that somewhere over 400kg is probably more realistic, 500 if you are weekending with two people. I'm not sure if I have underestimated some items (such as personal gear), or if there are a bunch of things I have simply forgotten... What do you guys think?
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Loading list for the boat
"Man's mind and spirit grow with the space in which they are allowed to operate." - Krafft A. Ehricke, rocket pioneer
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alexander
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Re: Baltic Circumnavigation

Post by alexander » 08 Jun 2016, 20:33

Hi Manik
Maybe you could live with less batterie power and solar cells if you used a white LED light with built in solar cells as you can buy cheap in a garden center as position light. Also for your mobile phone and laptop there are small solar chargers. Cheap and light. Then you don't need batteries, solar cells and wiring. What else do you need electric power for? Do you really need an autopilot (electric?) when you are two aboard? That again would save money.
3.5 liters of water is not a lot for a day. O.k. when you are alone, but with a (girl-)friend washing would be nice. But then you have to go ashore once in a while anyway an fill up. And then you will eat there sometimes and go shopping. So you don't need all supply for the whole trip. Saves weight.
I think with your weight calculation you can go on. And money you can save on the expensive parts like electric and electronics.
Alex
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Manik
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Re: Baltic Circumnavigation

Post by Manik » 08 Jun 2016, 23:05

Thabks for the feedback, those are some good points! The electronics definitely make up a noticeable fraction of the cost, and add notable complexity (especially when building) and weight to the boat. A friend of mine already suggested leaving out the VHF to save weight and and money, and to cut down on power consumption, which saves more weight and money on batteries and solar panels. Alternatively I could take a VHF along but leave it off, unless I really need it. Of course that means no AIS , which is d definitely nice to have when singlehanding. I think there is almost no way around an electric autopilot unfortunately, it's the only thing that'll get the job done, on a fast boat.

I like the idea of having a few separate inexpensive solar chargers. It could save money and creates a bit of redundancy, which is good if something breaks.
"Man's mind and spirit grow with the space in which they are allowed to operate." - Krafft A. Ehricke, rocket pioneer
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Skip
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Re: Baltic Circumnavigation

Post by Skip » 09 Jun 2016, 13:31

My gut reaction is the weight allowances are fine. FWIW my standard for a 5 day canoe camping trip, all gear, food, water etc; everything that goes in the boat except yours truly is 80# (37kg). It is minimalist but has worked many times.
Loading up for 5 days on the Texas 200 comes in at about the same thing. Nomad's not making the trip, two floods in less than a month hindered preparations enough that John Wright and I are going in his 23' skiff actually more of a sailing canoe.

Skip
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cpcanoesailor
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Re: Baltic Circumnavigation

Post by cpcanoesailor » 09 Jun 2016, 16:07

With VHF and AIS, transmitting needs way more energy than receiving. Could you get by with a hand-held VHF? AIS receiver only? Or maybe just a radar reflector? With batteries, lead acid are cheap, but very heavy. LFP have up to 4x the energy density, but are expensive. Flexible solar panels are much lighter, but more expensive than framed panels. MPPT charge controllers are more efficient, but more expensive than PWM. These are all tradeoffs: $$ for less weight, more capability.

A proa with no electronics is the lightest and cheapest of all. But the Baltic is not the south Pacific. :)
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Rob Zabukovec
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Re: Baltic Circumnavigation

Post by Rob Zabukovec » 09 Jun 2016, 17:13

Marco,

In your weight estimates, your payload estimates seem to be in the right ball park, but in the overall assessment of loaded displacement your spreadsheet should also include rig weight and a fittings and sheets allowance. I guess around 45 kilos.

Assuming your all in loaded displacement is around 700 kilos, then using a 21.58m2 Tornado rig, for a 7m long vaka, your Base Speed or average flat water speed should be around 8.7 knots. If you stretched the vaka to 9 metres long, even if you added 80 kg to the bare hull weight to do it, then your average speed would be 9.6 knots. If you added 16m2 light weather jib/gennaker/screecher on a roller, then your average speeds would go up to 10.5 and 11.6 knots respectively.

Another thing which is important, is the ability of your boat to carry sail, ie, Sail Carrying Power as defined by Frank Bethwaite, which ultimately boils down to the ratio of righting arm to heeling arm. Righting arm is best calculated from your spreadsheet locating all the items in their normal sailing position and doing moments for them all. Heeling arm is the vertical distance between CE and CLR. I reckon if your Proa is less than 0.30, then it will be too tender. Sidecar in its worst case scenario is 0.33 and with light weather jib up is 0.37. Bucket List, depending on what weights and displacements you want to believe is around 0.38. A Tornado cat with 2 on the trapeze is around 0.42. Pure & Wild for example to achieve 0.30 means that both crew had to be sitting on the ama, thereby rendering off watch rest and therefore the cuddy pod to leeward useless and exacerbating.

Rig height and how much sail is hanging off a mast is important. Again, to use P & W as an example, carrys 33m2 of sail on a 10.5 m mast. Sidecar (nearly double the displacement and over 2m longer) carrys 43 m2 on a 10.3m mast. With light weather jib, it is 56m2. And P & W's mast is a lot heavier (almost double) as well. This also explains why you never see any una sail rigs in serious racing, because the rig and CE heights are excessive with pitching and pitch pole consequences as well, plus you are dragging around a lot of unused mast in the worst possible place once you start shortening sail.

BTW I understand that P & W has now increased its ama weight and shortened it rig.

And FWIW I have attached an overlay of a Tornado rig on P & W's rig.

Rob
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Last edited by Rob Zabukovec on 09 Jun 2016, 23:05, edited 2 times in total.
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Manik
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How fast does it have to be?

Post by Manik » 09 Jun 2016, 22:57

The goal for me is a really streamlined process: 6h sleep, a total of 1h for anchoring, getting the sails down + getting going again the next day, and 17h sailing time. If we take a more cautious 16 hours per day as sailing time, then 100 NM/d requires an average speed of 6.25 knots, including the time not sailing due to strong breeze & calms.
pilot_baltic_july.png
Extract from a North Atlantic Pilot Chart from the NGA, for the month of July
Looking at the pilot charts for July and August, the average windspeed in the the southern 2/3rds of the Baltic are 3-4Bft (7-16 knots), commonly westerlies, with 4% calms. In the very north of the Baltic it's more like 2-3Bft (4-10 knots) and wind from pretty much from any which way, with 10% calms. The chance of gales at that time of year is 1-2% over the entire area. I will have to stop sailing much earlier than force 8, so it will be more than those 1-2% which is lost to too much wind, let's say 5% overall. That gives me 91% sailing time in the south and 85% in the north. If we use the 85% for further computations, then the average speed I need to be doing when I'm actually sailing is:

(100/0.85)/16 = 7.4 kn

So I need ~7.4kn all the way, or slightly less because the fraction of calms in the south is lower. When you look at Ryan Finn's daily runs with Jzerro it becomes clear that this won't be easy. For the dataset he posted (no calms), he averaged 198 miles per day (24h) or 8.26 knots, in mostly 3-4 Bft of wind, with a 36ft boat. That makes an average Froude number (see this table) of just over >0.4, which is pretty good. Assuming I can also manage Fn=0.4, in the conditions in the Baltic, when actually sailing, then a 7m vaka would get me to 6.4 knots, or a 9m vaka to 7.3 knots.

This really crude analysis indicates a 9m vaka may just and just reach 100NM per 16h-day, with 15% downtime for strong breeze & calms included, whereas a 7m vaka would make about 90NM.

@Rob: Your numbers for flat water speed seem plausible. How are you arriving at those estimates, especially with regard to the sail areas? :)

Cheers,
Marco
Last edited by Manik on 09 Jun 2016, 23:15, edited 2 times in total.
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Rob Zabukovec
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Re: How fast does it have to be?

Post by Rob Zabukovec » 10 Jun 2016, 00:03

Manik wrote: ......This really crude analysis indicates a 9m vaka may just and just reach 100NM per 16h-day, with 15% downtime for storms & calms included, whereas a 7m vaka would make about 90NM.

@Rob: Your numbers for flat water speed seem plausible. How are you arriving at those estimates, especially with regard to the sail areas? :)
Marco, I use Multihull Dynamic's Base Speed formula, which I have put on the forum before, but here it is again:
http://www.multihulldynamics.com/news_a ... icleID=226
I also have my own formula, which includes SCP, but it isn't proven and still needs work on it, but for the most part, comes up with slightly lower numbers than Base Speed.

Sail areas are either given or deduced from screen dumping rig plans into AutoCad, scaling and then tracing them Then turn them into regions which you can interrogate for the exact area and centroid of the tracing. It is all fag packet stuff and comes with a health warning.

If you find a better way, please let me know. In some cases you can also extract the basic information off Texel, OMR and MOCRA rating listings which are real and not the designers aspirations.

I also have to say, that you will not do 100 miles a day on average, and as much as you would like to drop anchor anywhere at exactly the 100 Nm spot, it won't work that way.....tides, wind or the lack thereof, over sleeping, fog etc will affect you.

I also have a healthy wariness for digital charting, it is too easy for the hardware to get damaged, miss a danger because you had the wrong zoom or delete all sorts of stuff because you were too tired or exhausted to think, or the boat lurched at the wrong time. I have done lots of sailing, some singlehanded, across and along the English Channel, down to Spain and Portugal and up into the Baltic as far as Warnemunde using 2 identical handheld GPS's, both programmed and updated with the same waypoints and info, and paper charts. It is a good discipline to put yourself on paper every hour, see where you are and what is coming and fills up time. No matter how much you like sailing, it gets to you sometimes.

Rob
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Manik
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Re: Baltic Circumnavigation

Post by Manik » 10 Jun 2016, 10:18

Thanks, I hadn't seen that formula before! :)
Rob Zabukovec wrote:I also have to say, that you will not do 100 miles a day on average, and as much as you would like to drop anchor anywhere at exactly the 100 Nm spot, it won't work that way.....tides, wind or the lack thereof, over sleeping, fog etc will affect you.
Except for Denmark, there are no tides in the Baltic. The opening is too small for any significant amount of water to get in or out of the Baltic in 6 hours so the tide is on the order of centimeters. ;) In the estimate of conditions I did forget fog though, and perhaps 5% for 6Bft and above is too little. I need a proper pilot chart for the Baltic! If assume say an average of 80% of the available 16 hours can actually be spent sailing, then to get 100 NM per day on average would require:

100 / 0.80 = 125 NM/d (on a day without fog, calms, or too strong winds)
125 NM / 16h = 7.8 knots

That's not going to happen, Jzerro did 8.3kn on the way to Panama. I think 7kn or a little above may be achievable though, so with 16h that makes 112 NM, 80% of that is 90 NM. If I lose another hour of sailing time to anchoring etc and only sail (effectively) for 15h/day, then that makes 105 NM, 80% of that is 84NM. So with this extra reserve, 80-90 miles per day averaged over the whole trip (excluding harbor days) seems more realistic.

I do think that the 16 hours should be achievable. 6h sleep is sufficient for me for longer periods, supplemented with powernaps it'd be more sleep than I'm averaging now, so that's not an issue provided the sailing is not physically exhausting all the time. To really get a high fraction of effective sailing time, the accommodations need to have everything set up (bunk, nav, cooking), maybe just affixed with bungees, so that the amount of stowing/unstowing of gear, needed to hunker down for the night or get moving again, is minimal.

All that said, I think even that average of 80-90 miles will require at least an 8 meter hull, and probably more like 8.5 to 9.0 meters. That could be quite difficult to reconcile with the the 5000-6000€ budget and 5.5 meter long workshop.
"Man's mind and spirit grow with the space in which they are allowed to operate." - Krafft A. Ehricke, rocket pioneer
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