infos and tips

 

MPS or Blister

 
Seamanship
Nautical Handbook 		The sail MPS or Blister D
Downwind sails General 1

Spinnakers

Everyone knows that the spinnaker gives the fastest sail performance for a yacht on off-wind courses and up to approx. 70 degrees on the wind.

The spinnaker is an absolute must for the regatta sailor, but even nowadays, many cruising sailors seldom use it.

Especially in light wind conditions, it is the relatively heavy cruising and charter yachts which could most benefit from the power of the spinnaker. But all too often the motor is started and the spi stays in the sack.

WHY ? The reason is that the classical symmetrical spinnaker has the reputation for not being the most manageable of sails. The development of the spi sock has mead the spi easier to handle, especially for small crews, but the setting of the spinnaker pole remains.

The Blister or MPS, the asymmetrical spinnaker, is an alternative.


Starcut


Tri-Radia l 		The asymmetrical spinnaker was developed about 20 years ago by a number of sailmakers and was given a range of names accordingly. Thus, the asymmetrical spinnaker may be called a cruising chute, blister, splister, gennaker, etc.
At Rolly Tasker Sails we refer to this all-round sail as a Multi Purpose Spinnaker or MPS.

We have three basic designs :

Radial Head, Tri-Radial and Starcut.

The Starcut is generally a flatter cut and can be used for more reaching courses.

The Radial Head and the Tri-Radial are fuller cuts and, with their wider shoulders, can be flown well for more downwind courses like a traditional spinnaker, but with the advantage of not having to use a spi pole. In dead downwind courses or with a swell one can also use a pole to stabilise the sail.

The Tri-Radial MPS is a real all-round spinnaker, with a sailing range from 70 to 180 degrees. From fairly onwind courses to broad reaches to downwind, the sail can easily be trimmed, giving an optimal performance, comfort and speed.


Radial-Head

Especially in areas like the Mediterranean, with its often light summer winds, the joys of spinnaker sailing should not be missed !

 
Seamanship
Nautical Handbook 		The Sail MPS or Blister D
Downwind sails Sail setting 2

Setting an MPS

1. The MPS, or blister, is a free-flying sail, normally used without a pole.

The sail is controlled using a spi halyard, a sheet and a downhaul guy.

2. The downhaul guy can be led to the cockpit via a block which should be attached fore of the forestay.

3. Shorthanded crews should adopt a rule of lowering the MPS when the apparent wind reaches 15 knots.

The MPS tack downhaul guy, instead of being led back to a cockpit winch, can be led through a block and tackle system using a cam cleat stopper on the lower block, or tied down to a cleat on the foreship deck.
The downhaul guy is attached to the tack of the MPS using a bowline.
The downhaul guy
is led to a winch in
the cockpit via
turning blocks
(the block fore of the forestay being a swivel block).

The MPS sheet is attached to the clew using a bowline.

The hauling point for the MPS sheet should be between the hauling point for the Genoa No.1 and the stern.
Using appropriate blocks, the sheet is then led to awinch.

Seamanship
Nautical Handbook 		The sail MPS or Blister D
Downwind sails Sail setting 3

Spi or MPS Sock

1. The spi- or MPS-sock is particularly useful for shorthanded crews.
Using a sock and a good autopilot, it is even relatively easy to set and lower and MPS singlehanded.

2. Using bowlines, attach the downhaul guy to
the tack and the sheet to the clew.

The sock pull-line should be
tied down to a clamp on
deck so that the sock
cannot open on its
own whilst raising
the sock with the
halyard. Fig.2.

3. The spi halyard is attached to the stainless steel ring at the top of the sock. The sock should be hoisted in lee of a flying genoa or, as shown in Fig. 1, with the genoa already furled.
Fig.3 shows the inside layout of the upper part of the sock.
Seamanship
Nautical Handbook 		The sail MPS or Blister D
Downwind sails Sail setting 4

Setting an MPS with sock

1. The sock, with its pull-line, is hoisted with the spinnaker halyard. If not carrying out this manoeuvre singlehanded using an autopilot, then the sheet and tack downhaul guy can simultaneously be prepared in the cockpit.

2. It is advisable, especially with wind over 10 knots, to lead the sock pull-line around a cleat on deck.

Thus, when the wind starts to fill the lower part of the MPS and pusheds the sock upwards on its own,(especially with fresher winds), the pull-line is fed out automatically.

3. If the MPS is set to leeward of the genoa (unfurled), then there is less wind pressure in the sail during raising.

4. Whilst raising and lowering the MPS in the sock, especially in fresher winds, it is advisable to wear gloves.

Seamanship
Nautical Handbook 		The sail MPS or Blister D
Downwind sails Sail setting 5

The MPS is set

1. The sock is raised completely. The sail is set.

2. The sock pull-line must be tied down on a cleat on deck.

3. Trim the sail on a downwind course and enjoy life !

Seamanship
Nautical Handbook 		The sail MPS or Blister D
Downwind sails Sailhandling 6

Gybing an MPS

1. Sail a downwind course apprx. 30º off the wind.

2. Release the sheet and let the MPS fly out afore.

3. Whilst the helmsman gybes, bringing the stern through the wind and to approx. 30º off the wind on the other tack, the loose sheet is brought around afore of the forestay and brought back on lee through a block to the lee winch. Fig.1, Fig. 2a and Fig.3.

4. Trim the MPS anew according to the desired course.

If using a sock (shown yellow), it can be lowered partly or completely whilst the sheet is brought around the forestay and back to the lee winch. Fig 2b.

MPS or Blister as PDF printing file