Foils for Cats by Morelli and Melvin

T

thataway

Active member
This is a U Tube video by Pete Melvin of the the yacht design team of Morelli and Melvin on the Aquila 36 Catamaran.

I have long criticized the Tom Cat 255 as having the bridge or wing deck too close to the water and the tunnel closed when at rest or lower speeds. This affects both performance and ride in the boat--and somewhat limits its capability as the seas build. The hulls should be about 6" deeper (or the bridge deck 6" higher). I attribute some of this to the same basic hulls being used in the Tom Cat 24 (which was the mold that the 255 hulls were taken from) and increased weight on the 255. The Tom Cat 30 (Black Feather Marine 30 or Chil Kat30) had an open tunnel and is a better performer--probably would be ideal for conversion to a foiling cat.

Morelli and Melvin have been one of the premier design teams on both catamarans and more recently on the foils for many boats, including the most recent American's cup sailing boats.

In this video they discuss the foil advantage (35% fuel savings) in the 36' Aquila catamaran. If this concept could be taken to the Tom Cat, it would be a huge plus. in ride and efficiency. Unfortunately it would not help the issues at rest or low speed. Also trailering could present a challenge with the foil.

Now all we need is someone with a lot of extra dollars and a Tom Cat they wanted to chop up--or buy a hull from the factory, and make it higher, and add a foil, then drop the standard cabin and interior on the boat. Probably would require extra long shaft outboards also-
 
Fun, but in PNW waters, scary, (hard, bumpy things in the water).

Might be the next boat for Jason :lol:

That 35% fuel savings sure sounds great.

Harvey
SleepyC :moon
 
Years ago, this team put a foil on a Corsair catamaran powerboat. I thought that it would certainly do very well on the market, but it just never did, as most boaters with power, were still focused on monohulls.
Ten years ago, I was involved in a design of a new boat for the USACOE and it was going to also have a foil between the hulls, similar to the Corsair. I retired from that job and they turned the project over to a commercial team to develop and the foil was not used. Sad, as it would have allowed the boat to plane at a much lower speed, burning a lot less fuel.
http://www.morrellimelvin.com/corsairfoiler/
 
Thanks for that information Steve--Nice boat--rarely on market.

gallery-corsairfoiler-07.jpg


Note the tunnel clearance in the Corsair foiler. Most likely the foils designed for the corsair (or similar, brought up to date) would work well on the Tom Cat.

Also note the anti slamming nacelle which runs all of the way from the bow to the stern, along with arched tunnel for a better ride.

Steve do you have any idea how much the foils cost?

Harvey the debris strike is addressed in one of the M & M videos. It can be a problem, but they think no more than a prop strike--and the foil is very beefy, much thicker than a prop blade. Also this foil does not protrude far from the surface of the hulls, as many of the side foils do.

Before I left S. Cal. in the 1990's there was a foiling navy frigate which was powered by turbines doing runs off the coast and speeds were in the 50 knot range. The Pegasus class patrol boat was used 1977 through 1993. These hydrofoils carried the designation "PHM" for "Patrol, Hydrofoil, Missile. There are apparently a number of other foil designs currently on the drawing boards or in build stage for the Navy.

Now that we see foiling surf boards, wake boards, all manor of small to medium size sailing boats are being retrofitted with foils, I suspect we will see more foiling power cats.
 
Dr. Bob,
The foil that I wanted on the Corps boat, basically, did not protrude below the bottom of the center of the two hulls. It was more of a wing, between the hulls, then what you see today on the Moths. I do not remember the cost, but it would have been made up quickly in fuel savings.
Back in my law enforcement days in the early 80’s, I got several rides on the Navy’s PHM’s. Very fast indeed, but the foils were not only a maintenance problem, but also caused one boat to crumple like a beer can, when it hit a whale. Another grounded and had significant damage as well.
Steve Baum
Homeport of Portsmouth, VA
OSPREY (Ex Mister Sea) 2000 22 C-Dory 2010 - Sold 3/19
OSPREY (Ex ADITI) 2007 26 Cape Cruiser 2018
 
ssobol":229f1scc said:
Foils on a Tomcat will make trailering and launching a bit more difficult.
Click to expand...

Agree if we use the current set up it would be almost impossible If we eliminate the inner hull guides and box, and use only outer hulls, with the rollers or bunks just outside of the foil, I believe a trailer could be made which would launch in the same depth of water. There even could be hydraulic pads which come in place under the entire transom if necessary. Hydraulic trailers are used often by boat transport companies to haul large vessels out at a ramp, transport across country and launch again at the destination.

Ideally you if you could get a set of just the hulls laid up to the wing deck line, and add on, with curved arch wing/bridge deck--making a custom wing deck, with both the hull and deck re-inforced for the foils. Companies used to sell hulls for private completion back in the 70's. Maybe the next recession someone will be adventurous enough to try it. Also this would allow a full length nacelle, as well as modification of the bows and built in engine brackets, instead of the bolt on bracket.
 
hardee":iz2ksk4r said:
Fun, but in PNW waters, scary, (hard, bumpy things in the water).

Might be the next boat for Jason :lol:

That 35% fuel savings sure sounds great.

Harvey
SleepyC :moon
Click to expand...

Harvey, I like the Aquila and the fact that they're outboard powered....but that open bow design wouldn't work for my needs in Mass. That boat has Florida written all over it.
Lol
 
Jason, it just seems like the timing was right for a new post from you :wink:

I totally agree about the open bow. Notvanything I would consider, even in Florida.

Harvey
SleepyC :moon
 
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