AUSTRIAN WHARRAM CIRCLE

WHARRAMS & WIND & STABILITY

50 Years Aniversary of the epic Voyage of James Wharram when he sailed little Tangaroa from England to Spain and later acros the Atlantic - here you find areport in english language, written for the PCA magazine

        50 Years of Seagoing Wharram Coastal Trekker / Trailer Designs

        and an uncomplete list of 'epic' voyages in small Wharram Cats

Somewhere in the literature you can find the sentence:

Wharram catamarans are designed for conditions which more than 90% of the sailors will never encounter...

....nevertheless Wharram catamarans may capsize,

and they do - as we have seen 3 of them at Lake Neusiedlersee (Tiki 21 & Pahi 26 twice) find details below

Our slightly modified Wind chart

0 - 1 Bft not enough wind

2 - 5 Bft enough wind

6 Bft this is really enough now

7 - 8 Bft more than enough wind

9 Bft its getting tight

10 - 11 Bft VERY tight

12 pray

A FEW EXAMPLES OF 'WIND PICTURES'

Mediterranean:

Gerald Winkler: NE-Sardinia - within minutes the wind picked up, a little later the wind indicator showed up to 45 kts and KANANASKIS was running under storm jib only but still doing 9 kts. We reached shelter in the Gulf of Olbia,

Günther Zimmermann: The sailing season 2000 started quite windy in Greece, because we had Meltemi already in spring. Once we had a lovely anchorage on the SE Pelloponnes which was (as we had to find out) protected against the wind but not against the swell. ANNA SOPHIE was trapped there and had to fight for survival having a bow anchor and an aft land line out. Around us were plenty of reefs. After days the situation eased a bit for a short time and we managed to escape

Justus Just: Hefty gusts coming down the rocks of Gibraltar and damaged this Tehini

These pictures were taken at the Lake Neusidlersee , wind beween 15 - 25 kts.

Pahi 26 - 5-6 Beaufort at Neusiedlersee, wind gusty, boat unloaded, full sails set, leehull slightly deep (a wave in front lets you overestimate it a bit), the windward hull is also not too worrying high the cat capsized without warning, total sudden, the mast top toughes the ground and prevents from a 180 capsize (the solo sailer is standing on one hull waiting for help, note the hanging hatch (was lost later on - the only damage) uprighting her was not such a big problem, important to use the masttop to attach aux lines, this system should work also in case of a total capsize we are of the opinion that a Pahi 26 has less stability than a Tiki 26, because she is narrower and the centre of effort is higher

Tiki 21 XANTHOS (Justus Just) enjoying a fresh breeze at the Moldaustausee

Justus Just: " Last month (july 2000) was a windy one at the Moldaustausee in the Cech Republic. We sailed our Tiki 21 unreefed, wind was up to 42 km / h. we felt always safe

Meinhard and Sissi Koch are sailing their Tiki 26 with the typical setting, full jib and one reef in the main, in a breeze, resulting in a fast passage from Elba to Corsica Trailertörns 2000 im Tyrrenischen Meer

Wharrams may capsize - as any boat can

James Wharram has derived a Stability Formula, its not the full truth but a good guideline, especially to decide when to reef:

The most important input parameters are: beam, centre of gravity, sail area and total weight. Below you can find screen dumps of an old DOS program (compiled from old FORTRAN IV) giving you examples of stability calculations for a Tiki 26 with different sail plans. Dependent of the weight (655 kg empty, 855 kg weekend cruising and 1055 kg for holiday cruising) STATIC and DYNAMIC critical stability functions were computed. According to JWD gusts may increase the average wind velocity by up to 60% - this is what they call dynamic stability. Results are given in Knots and Beaufort.

The results could be seen rather 'on the safe side', but are not a bad guideline

EXAMPLE:

we sail up to 25-30 kts of wind (true) at the Lake (no wave impact) with full sails set if we are racing, but this is really at the edge sometimes, it needs three adults on the windward hull and in gusts also a fast helmsman - you can see 26's flying a hull.

this goes together pretty well with shot 1 below, which gives you 32 kt without gusts at full load which is a good approximation of having your crew at the windward hull.

usually we start reefing at around 20 kts true wind speed

maximum wind we sailed at the Lake was 8 - 9 Bft with peaks of 53 kts (hankerchief of jib and double reefed main - no waves)

	FULL SAILS Jib: 9.6 m2 Main 16.7 m2 Max Wind without gusts, loaded up to 32 Kt. (7 Bft.)
	FIRST REEF Jib: 5.2 m2 Main: 12.4 m2
	2nd REEF Jib: 2.9 m2 Main: 8.7 m2
	STORM SAILS ONLY Jib: 1.8 m2 Try: 3.2 m2 Survival Mode of a Tiki 26: 11 - 12 Bft (55 - 92 Knoten)