Motor Boat & Yachting – May 2018

the surface in rhythm with the
light swell running through the
harbour. The sensation is strangely
anticlimactic, which can be viewed as
a positive in this context. I expected
the boat to feel more precarious, as
if it could topple off its carbon-fibre
stilts at any moment and crash back
down to sea level without warning.
This is not the case and in these calm
conditions at least, the whole process
feels entirely natural. We top out
at 32 knots without adjusting the
rake, though the team tell me that
they have achieved 42 knots in their
own tests with the thrill-seeking
Lequin at the helm.

GETTING TO GRIPS WITH FOILS
There are some handling
characteristics to be aware of,
however. Though the boat reacts
to outboard trim in the same manner
as a regular hull (trim up to raise
the bow, down to lower it), the foils
are much more sensitive to the
adjustments. Tiny changes to the
trim of the outboard engine will make
a significant difference to the running
attitude and it takes time to get the
balance correct. There isn’t a right

or wrong way of doing it; it’s about

setting the rake of the foil for the

conditions and playing with the

trim to find the most comfortable

running attitude for the conditions.

The steering is much more

sensitive at speed than it would be

on the normal Zodiac and even small

adjustments to the wheel prompt

fly-like reactions. There is so much

lateral grip generated by the foils

that you need to brace yourself for

the speed of the turn.

This is all well and good in a short

chop, where the foils allow the boat

to fly over the waves in remarkable

comfort, but how does it cope in the

rough stuff? We head outside the

harbour into the rolling swell and find

that a boat of this size can’t avoid

following the peaks and troughs

altogether, but the foils act like a pair

of shock absorbers, dramatically

reducing the vertical acceleration and

softening the landings (as you can

see in our video). As we run alongside

the regular RIB, it’s clear that its crew

are having a much harder time than

us and can’t keep up with our pace.

As well as the significantly better

ride comfort, particularly in a short

head sea, SEAir also claims an

average 30% increase in fuel

efficiency and as much as 50%

in some conditions. We weren’t

able to ratify these figures ourselves

in the time available but French

magazine Moteur Boat did manage

to take measurements on both the

standard RIB and the foiling version

fitted with an identical 115hp engine,

and have kindly agreed to let us

share their findings in the table on

the previous page. They also took

two sets of readings at a steady

speed of 20 knots and 25 knots.

In both cases, the engine on the

foiling RIB was revving 250-300rpm

slower to achieve the same speeds,

reducing fuel consumption by 28%

and 24% respectively.

The ultimate dream for the

boundlessly enthusiastic SEAir

team is for mainstream boatbuilders

to start offering a ‘foiling pack’ on

the options list that customers can

tick, just as they would an engine

upgrade or teak decking. Adapting

this foiling system from a small RIB

to a large cruising boat is fraught with

difficulties but we’ve learnt enough

from our sea trial of this remarkably

effective prototype to believe that

this could be the start of something

truly transformative.

Contact http://www.seair.fr

The foils make the boat

much more sensitive to both

trim and steering inputs. It

actually corners faster and

fl atter than a ‘normal’ RIB

A rendering of Avon’s

larger 670 RIB fi tted

with retractable foils

In rough weather, the foils

act like suspension

The boat still

fl ies off waves...

...but the foils

cushion the landing...

...before lifting

clear again

SEAir’s offi ces

are littered with

prototype sketches

BOAT MASTER NEWTECH