"Any rotaries". In case any of you didn't know, I am the director of a
non-profit ocean research group, Pelagic-Research.org. We use our boats
to
take research groups to catch, tag and study sharks. I am working on the
design for a boat specifically for our work- It will be approximately 30
feet long, will have a removable transom and be powered by a pair of
rotary
engines shafted to jet drives. We need the jet drives so that the sharks
and researchers can't be injured by props. We need the transom removed
so
that we can pull sharks onto the deck and 3 minutes later send them back
without lifting or handling them unnecessarily.
We are collecting funding for the project, and I have a couple of hulls
picked out that can be modified for our purpose. I will post pics as the
project takes shape. I am projecting 200 HP per engine, with a pair of
engines. We are targeting next summer as the splash date.
For the question of why the rotary- here is the reasoning:
Jet drives like high speed, and run well in the 4500 to 6000 RPM range.
The engines have to fit under the deck- the rotaries are small. The
whole
package has to be compact, and produce good power with reasonable fuel
economy. For comparison we used a 250 HP 2 stroke outboard running at
4500
RPM which typically burns 14 to 15 GPH. Our goal with this boat is to be
able to get 30 knots on 15 GPH or less.
We typically spend a week or more offshore on our trips, and fuel
stations
are scarce at best. On top of that, I absolutely refuse to carry
hundreds
of gallons of gasoline in our main vessel partly because we sleep on it,
partly because we don't have gasoline tanks on our all diesel boat. The
small boat has to be able to carry it's own fuel sufficient for the
trip. The "mother ship" uses 20 gallons per hour idling and 80 gph under
way, and takes a crew of 3 just to move it. So, we will tow the smaller
boat out, use it for the running and shark tendering, and tow it back.
For those that are counting, that will be 3 engines that I intend to use
the EFI on. I really don't like carbs on a plane, and I especially don't
like them under the deck of my boat.
I am collecting parts for engines in the boat, and any spare parts that
you
have would be appreciated. We are a listed non profit in Florida, but
for
some reason it seems to be taking the IRS longer to list us as tax
exempt.
Go figure.
Kevin Alderman
I ran a few numbers to get an idea of the BSFC for the outboards.
14 GPH is 87.5 pounds per hour at 6.25 pounds per gallon.
If you divide that by 250 HP you get a BSFC of .35. Too low by a
factor of .6. Two cycle engines are usually .6 BSFC or higher.
My guess is you are only using 145 HP while you are getting that fuel
burn. What do you guess the throttle opening is on the outboard?
At full power on the outboard at .6 BSFC you would be burning 150 pounds
per hour or 24 gallons per hour.
I would nail things down a bit better by connecting a manifold pressure
gage
to one of the outboards and record that and the RPM to see the amount
of HP you are using to go X fast.
The rotary, at partial power, leaned is .47 BSFC.
Therefor the rotary at 145 HP will burn 68 to 69 pounds per hour or 11
GPH.
At full power (250 HP) and a BSFC of .5 for the rotary 20 GPH.
At full power (200 HP) and a BSFC of .5 for the rotary 16 GPH.
Here is a HP and BSFC chart for the Le mans p-port 4 rotor.
The dotted line is leaned.
I think Dave Atkins sells a Marine water cooled exhaust manifold.
Paul Lamar
As far as BSFC on the outboard, no we were not at WOT. Your guess at 140
or
so is probably about right, cruise on plane. I ran the numbers because
on
the way in we ran out of fuel. The owner of the boat said that there was
no
way that we were out, but the numbers do not lie, and upon removing the
sending unit from the top of the tank the bottom of the tank was clearly
visible. Out of gas.
We do not plan to run our research boat as a speedboat, but it is nice
to
have power available, however a 4 rotor likely wouldn't fit in the space
we
have available below the deck. Its primary use is to patrol a 2 mile
radius
around the mother ship looking for and dealing with sharks.Since much of
our time is spent at lower throttle settings just easing around (2500
rpm
or so) I will likely go with a Renesis and leave it with standard ports
and
NA.
The water cooled exhaust is always welcome :)
Kevin Alderman
I am not advocating a 4 rotor. I just used that to illustrate what BSFC
you are
likely to get. It applies to all rotaries. 1,2,3 or 4 rotors. The RX8
engine is no
better at higher power levels. It just scores well at idle and low RPM.
I thought water cooled exhaust was mandated by the Coast Guard.
Paul Lamar
Actually, water cooled exhaust is optional. We can always run a dry stack
vertically if we want. Matter of fact, the Coast Guard 47' motor lifeboat
has dry manifolds. Only wrapped with turbo insulation tape. The engines
are
Detroit Diesel 6v 92 turbo with v drives.
Kevin Alderman
Maybe it is just California lakes.
Paul Lamar
Cant speak to California, its basically another country with its own laws,
tax structure, etc.
Kevin Alderman
Kevin, I should have my EFI working by the time I am out there.
I'll bring it down and we can try it on one of your engines.
What kind of ignition coils have you decided to use?
Paul Lamar
Right now I have and will test the engine with the stock igniter coils. I
finally installed the plate under the engine and have decided to install a
spacer between the factory oil pan and the plate. I know, another place for
an oil leak but I dont have time at the moment to fabricate a new oil pan.
I have 4 factory injectors, but haven't built the intake yet either. I
needed to mount the engine so that I could determine actual cowl clearance.
Tight is an understatement.
I plan to run the engine on a pair of carbs to get some time on the engine
before we get to the end so to speak- I hate surprises.
Paul, if you get a board and make progress, I will buy one from you and
have it connected before you spend time getting all the way down here.
Remember, I live in the Keys, almost to the end of the US on this side. We
are a good 8 hours from the Orlando area, longer from anywhere else except
for Miami- which is around 2 hours away.
I do have an empty apartment under the house though if you make it down
here :)
I have part of the code for the Arduino unit, but it has not been tested at
all at this point. I had intended to buy a PSRU, but I have some people
that owe me lots of $, and their decision not to pay back what we loaned
to them last year is putting a damper on the budget. I have to find a way
to install the starter, which will only require time to make a bracket.
More time that's all.
Kevin Alderman
I don't mind driving. I actually like it. I plan on taking week ends off
anyway.
I like the keys. I'll bring my computer so I can make changes in the
program for my
EFI if necessary. If you stick with the stock 2nd gen coils that makes the
EFI much
simpler. I'll set the simple system up for them
It is easy to mount the starter with a plate and spacers.
That right front rubber bushing is subject to exhaust heat. They have been
known to
melt. :)
Paul Lamar
I am pretty sure that in the next few weeks I wont have enough done to
justify a trip down here. Too much to do, not enough time. I am planning to
have the oil pan bolted down (up?) to the bottom of the mount plate this
weekend, but getting to the starter, radiator ( I haven't bought one yet)
oil cooler (I have the OEM cooler) and getting all these parts mounted will
take more time than is available.
This pic was taken a couple of weeks ago, and the plane looks remarkably
similar today. I have been working on it, but as you know sometimes we do a
lot and it doesn't look like it. One reason I haven't started the wiring of
the engine, is that there is still uncertainty as to which way the system
will progress. I have seen some photos of installations on this board that
show a simple curved tube with the wiring run through it. I am not
comfortable with a hole that big in the firewall. I installed the engine
plug from my Viking, MIL spec, 10 pin through the firewall. I am thinking
I will need 4 to 8 more pins to get it completed with 2 spare pins.
If you are able to make some progress, let me know. It is 8 hours to Tampa
from here, I could always drive up and shake your hand! There will be a
TFR, so flying might be too much hassle!
Kevin Alderman
I won't be in Florida until Oct first. I will visit a lot of people along the way and
take a lot of pictures. Several in north and central Florida and then I will probably
be busy for the first couple of weekends. Sandy should have his Glass Goose almost
flying and Richard his one rotor.
As far as the EFI system is concerned three wires for the coils, four for the
injectors, one for the temp sensor, a shielded one for the CAS. The map sensors are
hose. I group these in separate harnesses.
The simple system I am building will have one CPU per rotor.
Paul
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