-Mr. Deering wrote:

I've explored it a bit. There's at least one boat around here featuring a
hydrofoil spanning between the hulls, using the Teknicraft design from your
parts (New Zealand). My understanding is that the foil only becomes
effective at speeds exceeding 20 knots. At slower speeds the increased drag
of the foil exceeds the performance advantages of increased lift, which is
almost nonexistent at slow speeds..

Mr. Deering and Members,

We have been looking at foils as of late, and particularly, the
teknicraft hull form.  The boat near you, is that the Reel Time Charter
boat?  I am curious to what issues any owner of a foil boat have had.
How often does floating debris and line become tangled around the foil?
When it does, what type of impact does it have? I've heard of some
leaks around the fasteners at the keels on some foil boats, but this
seems to be a case more of improper design and / or a relatively new
idea needing to be fleshed out. I spoke with the owner at Teknicraft,
and he stated that lines typically are not an issue.  Up here in New
England with all the lobster pots...well an image keeps popping in my
head of a retired couple diving overboard into cold waters with a knife
in there mouth.  Perhaps its more adventure than they would want.  So
for recreational applications, I think this issue is important to learn
more about.

We run a displacement shaped hull.  Our boats are light, and they can
push nicely into the higher speeds, but maximum efficiency is achieved
at approximately 20 mph.  With Suzuk 300's, thats about 2MPG.  It drops
off to about 1.5mpg at 28 to 30 mph.  We're interested in maintaining
our ride quality, but pushing the 2mpg mark up to 30kt's would be
ideal. If foils could do that for our customers, without hurting ride
quality, that would be something. We would hate to lose our ability to
glide around under 20 knot's though. This would have a big impact on
ICW cruising, not to mention average fuel efficiency.

I do wonder about the foils affect on ride quality.  Everything we have
learned regarding ride quality is that if you want it to ride nice,
then you've got to keep it in the water.  For us our displacement hull
shape and tall tunnel is the answer.  Foils are a very different
approach to this.
Unfortunately, I don't base this guess on much, but I would imagine
that to gain all the positives of foils with fewer negatives, it would
take a hull form designed with foils from the beginning.

Alex Whopper at Alwoplast (Chile) built a Crowther boat and added foils
to it.  As I remember it, the hull form was a displacement full stern
design, certainly not designed for foils from the beginning.

Bob Deering
Juneau, AlaskaRussell Hunt, President
Multihull Development, Inc. and Buzzards Bay Catamarans
Office #: 508-403-0301
Cell #: 508-759-4111
Other #: 800-882-7083
Email us at: info@MDcats.com
Check out our website at : www.MDcats.com
http://www.yachtworld.com/multihulldevelopment/

The Husacat foil has been around for some time. It does offer higher speeds
and some ride improvement. I have heard it makes steering a little confusing
in bigger seas. The foil is made of stainless steel, and thus keeping any
bottom paint on it is almost impossible. It does nothing at lower speeds, but
it will allow the boat to plane out faster. When all is considered I think
fine displacement hulls with decent beam, low CG, light high tech
construction, and lots of bridge deck clearance ; ultimately provides the
advantages that powercats are supposed to offer, ie. improved ride and
stability, extended range and fuel economy, shoal draft and full prop
protection.
----- Original Message -----
From: Russell Huntmailto:info@mdcats.com
To:
power-catamaran@lists.samurai.commailto:power-catamaran@lists.samurai.com
Sent: Tuesday, November 17, 2009 7:02 AM
Subject: [PCW] Foils on Cats

-Mr. Deering wrote:

I've explored it a bit. There's at least one boat around here featuring a
hydrofoil spanning between the hulls, using the Teknicraft design from your
parts (New Zealand). My understanding is that the foil only becomes
effective at speeds exceeding 20 knots. At slower speeds the increased drag
of the foil exceeds the performance advantages of increased lift, which is
almost nonexistent at slow speeds..

Mr. Deering and Members,

We have been looking at foils as of late, and particularly, the
teknicraft hull form.  The boat near you, is that the Reel Time Charter
boat?  I am curious to what issues any owner of a foil boat have had.
How often does floating debris and line become tangled around the foil?
When it does, what type of impact does it have? I've heard of some
leaks around the fasteners at the keels on some foil boats, but this
seems to be a case more of improper design and / or a relatively new
idea needing to be fleshed out. I spoke with the owner at Teknicraft,
and he stated that lines typically are not an issue.  Up here in New
England with all the lobster pots...well an image keeps popping in my
head of a retired couple diving overboard into cold waters with a knife
in there mouth.  Perhaps its more adventure than they would want.  So
for recreational applications, I think this issue is important to learn
more about.

We run a displacement shaped hull.  Our boats are light, and they can
push nicely into the higher speeds, but maximum efficiency is achieved
at approximately 20 mph.  With Suzuk 300's, thats about 2MPG.  It drops
off to about 1.5mpg at 28 to 30 mph.  We're interested in maintaining
our ride quality, but pushing the 2mpg mark up to 30kt's would be
ideal. If foils could do that for our customers, without hurting ride
quality, that would be something. We would hate to lose our ability to
glide around under 20 knot's though. This would have a big impact on
ICW cruising, not to mention average fuel efficiency.

I do wonder about the foils affect on ride quality.  Everything we have
learned regarding ride quality is that if you want it to ride nice,
then you've got to keep it in the water.  For us our displacement hull
shape and tall tunnel is the answer.  Foils are a very different
approach to this.
Unfortunately, I don't base this guess on much, but I would imagine
that to gain all the positives of foils with fewer negatives, it would
take a hull form designed with foils from the beginning.

Alex Whopper at Alwoplast (Chile) built a Crowther boat and added foils
to it.  As I remember it, the hull form was a displacement full stern
design, certainly not designed for foils from the beginning.

Bob Deering
Juneau, AlaskaRussell Hunt, President
Multihull Development, Inc. and Buzzards Bay Catamarans
Office #: 508-403-0301
Cell #: 508-759-4111
Other #: 800-882-7083
Email us at: info@MDcats.commailto:info@MDcats.com
Check out our website at : www.MDcats.comhttp://www.mdcats.com/
http://www.yachtworld.com/multihulldevelopment/<http://www.yachtworld.com/m
ultihulldevelopment/>

Power-Catamaran Mailing List

Russell,

You are correct.  The boat I'm most familiar with is the Reel Time.  I've
talked to the owner and studied it closely out of the water.  I've not
ridden on it personally.  I've also visited the builder, All American
Marine, and looked at other boats they were building and talked to them at
length.

The hull is indeed built for the foil.  The primary feature of the hull is
that it is an assymetrical, semi-displacement hull, designed to maximize
separation in the tunnel, which allows for a maximum foil length.

The foil mounts about a foot above the keel(s), spanning the hulls at about
the center of gravity.  Leakage at the attachments isn't a problem - these
are welded aluminum boats, and the hull has a reinforcing plate welded on
it, then an attachment flange welded to the plate which the foil bolts to.
The flange is designed to break off before the hull would be breached in the
event of a foil impact.

The foil is stainless, as Pat states, though it seemed to be holding hull
paint when I say it come out of the water at the end of the summer.  I don't
know the grade of the allow.  The foil has to handle a pretty big bending
load when it lifts the boat, so it has to be strong.  I would think a carbon
fiber foil might do the job for a lot less weight.

I'm told the ride of the boat was fantastic at 30 kts.  It rode about a foot
higher in the water than it would without the foil, so its hulls are still
in the water.  Fuel economy was improved significantly.  Reel Time has jet
drives.  One of the challenges with foils is getting fore-aft trim right.
The Teknicraft design uses a couple of small adjustable fins inside the aft
end of the tunnel - by trimming those fins manually you can tune in the trim
of the boat.  I've thought that with outboards you could achieve that with
the outboard trim/tilt dynamically, but I don't know.

The owner didn't have any major problems with debris hanging up on it.

I had plenty of time to examine the hull - I even took measurements and
photos.  The boat was on the hard for nearly a year after connecting with
our harbor's floating, concrete breakwater doing 30 knots...in the dark...on
autopilot...with a drunk captain.  The foil may have saved the captain's
life since it lifted the boat adequately to allow it to skid to a stop on
top of the breakwater (with a big hole in one hull) - if it had been riding
a foot lower in the water it likely would have sunk on the spot after
smacking the breakwater hard.  But the captain, in his befuddled state,
backed the boat off of the breakwater...and it sunk anyway.  He got off
fine.  The poor girl with him was seriously hurt.  He went to jail.  The
boat was fixed and is still operating to this day.

Bob Deering
Juneau, Alaska

Bob, unfortunately I am sure a carbon foil would not stand up to hitting
debris or flotsam.
Pat
----- Original Message -----
From: Robert Deeringmailto:deering@ak.net
To: PCW Listmailto:power-catamaran@lists.samurai.com
Sent: Tuesday, November 17, 2009 9:34 AM
Subject: Re: [PCW] Foils on Cats

Russell,

You are correct.  The boat I'm most familiar with is the Reel Time.  I've
talked to the owner and studied it closely out of the water.  I've not
ridden on it personally.  I've also visited the builder, All American
Marine, and looked at other boats they were building and talked to them at
length.

The hull is indeed built for the foil.  The primary feature of the hull is
that it is an assymetrical, semi-displacement hull, designed to maximize
separation in the tunnel, which allows for a maximum foil length.

The foil mounts about a foot above the keel(s), spanning the hulls at about
the center of gravity.  Leakage at the attachments isn't a problem - these
are welded aluminum boats, and the hull has a reinforcing plate welded on
it, then an attachment flange welded to the plate which the foil bolts to.
The flange is designed to break off before the hull would be breached in
the
event of a foil impact.

The foil is stainless, as Pat states, though it seemed to be holding hull
paint when I say it come out of the water at the end of the summer.  I
don't
know the grade of the allow.  The foil has to handle a pretty big bending
load when it lifts the boat, so it has to be strong.  I would think a
carbon
fiber foil might do the job for a lot less weight.

I'm told the ride of the boat was fantastic at 30 kts.  It rode about a
foot
higher in the water than it would without the foil, so its hulls are still
in the water.  Fuel economy was improved significantly.  Reel Time has jet
drives.  One of the challenges with foils is getting fore-aft trim right.
The Teknicraft design uses a couple of small adjustable fins inside the aft
end of the tunnel - by trimming those fins manually you can tune in the
trim
of the boat.  I've thought that with outboards you could achieve that with
the outboard trim/tilt dynamically, but I don't know.

The owner didn't have any major problems with debris hanging up on it.

I had plenty of time to examine the hull - I even took measurements and
photos.  The boat was on the hard for nearly a year after connecting with
our harbor's floating, concrete breakwater doing 30 knots...in the
dark...on
autopilot...with a drunk captain.  The foil may have saved the captain's
life since it lifted the boat adequately to allow it to skid to a stop on
top of the breakwater (with a big hole in one hull) - if it had been riding
a foot lower in the water it likely would have sunk on the spot after
smacking the breakwater hard.  But the captain, in his befuddled state,
backed the boat off of the breakwater...and it sunk anyway.  He got off
fine.  The poor girl with him was seriously hurt.  He went to jail.  The
boat was fixed and is still operating to this day.

Bob Deering
Juneau, Alaska

Power-Catamaran Mailing List

Roger Deering,
Roger, is a very useful contributor to this chat
page over the years you are correct most of the time.

We run our 50ft catamarans electrics off 2 x 190 amp service alternators
using our 2 x 315hp main motors which then charges
our 2x 300amp service battery banks, 1 service bank set for each hull side,
Port and  Starboard.
We maintain each electrical side of the catamaran completely separate to the
other.
The separate engine motor and generator batteries are for that use only.

We have 220/110V dock hook up as we have been told by our buyers, "out on
anchor we open all the hatches, no AC, no generators.
Sometimes we need heat, just like Roger Deering mentioned.

When there is a need for cold AC the owners mention that, they are usually
at a dock or enclosed marina area and then they can hook
up to the shore power, still no generator.

As far as Foils go, they were usually fitted to very badly designed power
catamarans as an option to try and get them going, a proper
designed asymmetrical power catamaran, will and can afford all the
attributes desired of such a vessel , speed, comfort, and fuel saving.

Tim Jordaan
Aventure Catamaran