F-9A, F-9AX and F-9R Trimaran Designs

Dennis Neumann’s F-9A Milagro in Connecticut . Has a Marstom carbon wing mast and optional boomless mainsail

The F-9A was used as the basis for the F-31 production trimaran, which was initially built in Australia in 1991 – see Launching Report reprint. The F-31 was then implemented at Corsair Marine in 1994.

Both the F-9 and F-31 are virtually identical, with the same hulls, beams, folding system, and rig. Many F-31 parts can still be used for the F-9A, but several areas of the F-9 series have been improved over the F-31 as currently built by Corsair Marine. These include larger and more efficient Mk II floats (430lbs more buoyancy), carbon fiber chainplates, and a daggerboard rudder option (as used on the F-32/F-33).

There are three versions as follows:

F-9A – a larger, more long term performance cruiser, yet still easily trailerable for great versatility.

F-9AX – has a 15% wider center hull for even more interior room

F-9R – a higher performance version of the F-9A with a taller rotating mast.

All models can be built with different cabin versions as follows:

Aft Cabin Version

The aft cabin version has ample room for 4 or 5 adults, with standing headroom in the galley area. Galley is large and can be customized to individual taste. A chart table can be located on the starboard side (with a fold down flap).

Cabin settees are 6′ 3″ (1.9m) long and these are also used for berths, with storage areas underneath. A cabin table will easily seat four, and can fold down or away when not in use.

The aft cabin has a double berth with full sitting headroom. Access is through a hatch in the aft cabin front, or through under the cockpit.

The forward cabin has a separate toilet area on the port side which can be curtained off, a vanity unit is to starboard, and a cozy (snug) double berth, or large single is in the bow.

Wayne Gorrie and Janine Bell’s F-9A REDSHIFT

Aft Cockpit Version

The aft cockpit version has a longer main cabin, for more interior space, while the larger cockpit extends to the transom. Major advantage is a separate ‘walk in’ head and shower area besides the daggerboard case, and a very large double berth in the bow.

Both cabin versions have a 2 1/2″ (64mm) higher cabin roof option, for more standing headroom if required.


A daggerboard is used for simplicity, its case helping to support the mast. A kick-up spade rudder is housed in its own retractable rudder box in the transom.

A new transom hung rudder is recommended for either the aft cabin or aft cockpit versions, due to its lighter weight, simplicity and adjustability. If desired, the original F-9A underslung rudder still remains an option.

The fractional rig is very efficient and easy to handle in all conditions. Farrier designs do not need an oversize rig to perform well, and this coupled with the F-9A’s enormous 47,000 foot-lbs righting moment results in a very safe cruising boat. Boom is roller furling.

An outboard of 8 to 15 HP is recommended on the stern with remote controls being located in the cockpit if needed.

F-9A™ Specifications

L.O.A.30′ 10″ (9.4m)
L.W.L.30′ (9.15m)
B.O.A.22′ 5″ (6.84m)
Folded Beam8′ 2 1/2″ (2.5m)
Draft1′ 4″ (0.41m)
D/board down5′ 6″ (1.67m)
Empty weight3000-4000lbs
(depends on materials/methods)(1350-1800kg)
Mast Height Std.40′ (12.2m)
Sail Area (Main & jib)599sq.ft. (55.4sq.m.)
Height on Trailer11′ 6″ (3.5m)


Same as the F-9A but with a 15% wider center hull for considerably more interior room, a 16% higher load capacity, and 8″ (200mm) wider overall beam (23′ 1″ or 7.04m).

F-9AX aft cabin interior

The trailering width is increased to 9′ 6″ (2.9m) but this can be easily trailered in most states, and many countries without major difficulty. Usually just a written permit. Has the same options as the F-9A.

Don Schmidtke’s F-9A in San Diego


The F-9R is a very high performance version of the F-9A, with a taller rotating mast, while still retaining the same F-9A roomy interior and easy setup. It is the home builders equivalent to the F-31R which has been setting race records in both the U.S. and the U.K.

The wider F-9AX center hull can also be used to build an F-9RX, which will have very similar performance to the F-9R. The F-9RX will have less wetted surface area, for the same load, so it should be faster in light airs, and the wider center hull will encourage it to plane earlier, so it could also be faster in heavier airs.

It is recommended that the F-9R interior be kept very simple and basic, to save weight for the best performance, and it can be upgraded later if necessary, when racing days are over. A large double berth can be either in the aft cabin, or the forward cabin of the aft cockpit model. Settees run down both sides of the main cabin, with footwells aft under the cockpit for quarter berths as required. A galley unit can be fitted in several different areas, and a fully enclosed head is optional.

The rotating mast is an aluminium or carbon fiber section (wing section preferred where available). Special new mast handling systems have now also been developed to make raising or lowering a rotating mast easy and safe whether the boat is folded or unfolded.

Sail wardrobe is simple and consists of a square top main, boomed or boomless, a blade jib, plus a screacher and an asymmetric spinnaker using an extended bow pole. The roller furling screacher is one of the most versatile sails in the inventory, and can be used to windward in light airs instead of a genoa.

Construction of the F-9R must be in foam and glass to achieve the required light weight, while high tech modern fabrics such as Kevlar or carbon fiber are optional for any F-9 version.

Dean Snow’s F-9R, winner of the 2001 Marlay Point Race in Australia

F-9R™ Specifications

L.O.A.30′ 10″ (9.4m)
L.W.L.30′ (9.15m)
B.O.A.22′ 5″ (6.84m)
Folded Beam8′ 2 1/2″ (2.5m)
Draft1′ 4″ (0.41m)
D/board down5′ 6″ (1.67m)
Empty weight2700-3300lbs
(depends on materials/methods)(1230-1500kg)
Mast Height42′ 6″ (12.95m)
Sail Area (Main & jib)647sq.ft. (60sq.m.)
Height on Trailer11′ 6″ (3.5m)
Rich Richmonds F-9 TRI DREAMIN – multihull winner of 1995 Newport Ensenada, and third over the line behind Steve Fosset’s 60’ racing trimaran LAKOTA, and a Formula 40 cat. TRI DREAMIN also finished 50 minutes ahead of the fastest maxi monohull, Roy Disney’s Santa Cruz 70 PYEWACKET
The F-31R – F-9R is identical in design but it can be built lighter, and now has larger Mk II floats
F-9AX aft cabin interior – looking aft

Some more assorted F-9A interior photos (Dean Snow’s race winning F-9R FULL BORE shown):

Hank Brooks’ F-31 in Pryce Channel, Canada