Transpac 52s - designers notes 2

Merfyn Owen on the OCDG/Clay Oliver TP52 PLUS details of the new Vallicelli design

Alessandro Nazareth of A. Vallicelli & Co. Yacht Designers describes their TP52:

Our office has been monitoring the TP52 class from its very beginning in the USA, mainly because it is an open class boat very similar to our designs Riviera di Rimini and Gaia Legend both water ballasted 55ft Adriatic Open Class boats launched in the late 1990s.

If you transfer their 1800 kgs of water-ballast to the keel you obtain a very similar boat to a TP52 in terms of L/DSPL ratio, BWL/LWL ratio complete with max righting moment at 20/25°.

The TP52 being a tight box rule leaves the designer free to draw hull lines as he wants. In our research to determine the best hull shape we used our VPP combined with the large amount of data recorded on the race course on Gaia (launched in 1995) and her evolution Riviera di Rimini (1998).

The VPP optimisation focussed on the following areas:

- immersed volume distribution (curve of areas, waterplane shape, Cp, LCB) on a given waterline length
- maximum effective hull length, both upright and in heeled conditions, with different transom overhang configurations
- optimum BWL with maximum form stability obtained as a function of hull wetted area.
- optimum BMax to BWL section shape with crew righting arm position
- DSPL variations within the rule range, coupled with the VCG shifting above the rule maximum
- forward volumes shapes for light wind races without neglecting planing attitude and seakeeping behaviour of the hull. The lengthening of Riviera di Rimini from 55 to 60ft helped us a lot in extreme bow section shaping.

All this optimisation work was done bearing in mind Med conditions. The best hull shapes we obtained aimed at races in the Mediterranean are quite different from the current generation of TP52s. Most of the TP52 boats already in the water where mainly designed for offshore and medium to strong wind conditions - not exactly the race scene we can foresee for next season in the Med.

CFD will be thoroughly used in final appendage design (fin keel shape and profile, bulb shape and rudder planform), different configurations for inshore/offshore races will be available (and particular attention will be paid on systems to quickly change keel/bulb/rudder before each event).

The boat will be built in pre-preg carbon fiber on a Nomex core to ABS minimum scantlings, taking advantage of state of the art construction materials and technology allowed by the rule. In the present stage of hull development we are making a detailed engineering analysis of the boat to reach the lowest VCG for highest longitudinal stiffness. The resulting updated weight analysis will allow further improvement of hull shapes.

Deck layout is designed around the cockpit with twin wheels positioned quite forward to allow good communication between helmsman and trimmers with the mainsail track well aft on the cockpit bottom.

The two wide-body primary winches are connected with a carbon pedestal drive while the central mainsail wide-body winch is connected to another carbon pedestal drive Secondary winches are mainly dedicated to backstay manoeuvre but a stopper can be used to allow their use with gennaker sheets. Quattro winches on the coachroof are used for the halyards, but you can use them also for spinnaker sheets.

Navtec 4 way hydraulics will control the vang, outhaul, forestay and code 0 rams.
All deck gear is Harken/Spinlock.

The TP52 rule fixes rigging arrangements and measures. The mast will be built in high modulus to achieve minimum rule weight and VCG. The standard two or three swept back sets of spreaders on a simplified rig (no runners and checkstays) is laid down in the rule.

Internal layout is designed to comply with minimum IMS racing division Accomodation Regulations with six berths, navigation station in a central position close to the centre of pitching, plus a small galley and enclosed head compartment with curtain.

Minimum building time we can foresee is 20/25 weeks from hull lines delivery to the shipyard.

LOA: 15.85m
LWL: 15.3m
BMax: 4.00m
Draught: 3.50m
Disp: 7.5T
Ballast: 4T
Mainsail: 91.5sqm
Jib 105%: 65sqm
Gennaker: 248sqm