Contact info: Catmando2, Dave ?

At 250kg dry that is quite heavy... The Mercedes 1400cc diesel from their "smart car" and used in several home-built aircraft in USA (several fixed wing experimental) & Eu (Ramphos) weighs 75Kg and delivers 75 ~ 100 hp...

 

1400cc, thats about as much power as what, an electric toothbrush or blender?
How many million RPM does it spin, who marinises them and what gearbox does one use?
Found some details on what I think is the same motor

Thats not very good ^^

Where do I get them worked on in remote locations?

At the end of the day I wanted reliability and parts wherever I went

I wanted something that was slow spinning, high torque and high displacement that would last, just like the Gardners, JD's etc, but they are to large and very heavy.

lightweight fast spinners I don't believe would last.
I definitely didn't want little black computerised boxes or turbochargers to cause me additional problems

The Cummins stacks up fine if comparing to a
yanmar 2 litre 75 hp turbocharged at 237kg that spins at 3200rpm

or an Isuzu 69hp Turbocharged at 320kg?

or a Nanni/Kubota Turbo at 85hp and 285kg These only came in a 2L 60hp or 2.5L 85hp.

or perhaps a John Deere 84 hp at 437kg



edit: Catmando2 was my old user name, I forgot the password (but fluked it again recently) and opened a new ac. as sabahcat a while back if anyone was wondering.

 

http://www.ramphos.com/e/03_s.html the middle image on the left is the "smart turbo" diesel engine from the 1400cc 4 door "smart series" Mercedes cars... http://www.dieselveg.com/smart.htm is the 800cc engined Mercedes car conversion to burn veg-oil, the 4 door version of that car uses a 1500cc turbocharged engine and can be chipped to deliver 100hp in car form, but detuned to 75hp and weighing naked some 75kg worthy of a look? I was looking at it for a 15 knot 40 ft power-cat before I felt I could not do without sail... Also difficulties turbo+ watercooled manifold and wet exhaust...

 

I'm thinking I needed some weight in the bum as the tip of the prop is churning away about 250 mm below DWL

I would still be worried about longevity of those lightweight fast spinning electronically controlled low torque engines.

 

It had sufficient torque for my concept as that is also the 'aircraft needs' criteria, (1200rpm at the propellor in the water) but surface piercing/ventilating at displacement (15 knots max) was not resolved as draft & beam wl were 750mm with 7500kg displacement on 40ft lwl (12m) Earlier stages with Rick were looking appealing but too many issues that needed resolving...

Sorry I am distracting discussion from the original objectives - I will but out...

 

Dave,

Thanks for the info about your engine's choice.

Masalay,
Quote:
* Foreign Affair *:

- LOA: 14.25m
- LWL: 14.00m
- BOA: 6.75m
- L/B ratio: 16:1.
- Power: 2x100hp Yanmar 4JH3. 4 blade 19x19" props.
- Fuel tankage/range: 2000L diesel. Av consumption over 22,000nm is
1.1 L/nm. So with 10% reserve, at 12-13kts, range is 1600nm.
- Top speed: 20kts.
- Cruise fast : 15kts @ 1.3 L/NM.
- Range: No figures but estimate less than 1 L/NM. So range 1800.

Hull/fuel efficient!

Cheers.
Sinclair

Sinclair

 

Sinclair,
That sounds about right, The statistics I had relied on the data at the "ice-cat challenge" website which is now closed... That was where the original "sea-trial" for Foreign Affair was documented... A well designed boat... Thanks for the info...

 

Foreign Affair

Masalay,

Bill who commisisoned this motor cat around 2003
gave me those datae yesterday.
So very close to my specs.

Sinclair

 

And please DO NOT put a flybridge on it... That would spoil the lines and is totally un-necessary... I would hope the Robin Chamberlin design is your choice?

 

Mas,

- Fly: Nope, thank you! No wedding cake!
Would even like this one to be more integrated somehow.

- Design: 20000 + nm. later...
Bill told me he would not change much to his original requirements:
less steps, details really.

He also recommends Jeff Shionning who has a similar approach to motor cat.
But i definately like Robin's design more than the Prowlers i saw with flys in yachtworld.com
Weeks ago Jeff told me to get a good look at his Alaskan models:
http://www.schionningdesigns.com.au/www/page.cfm?pageID=206
Perhaps stretching the hulls of the 41' to 50', just the hulls not the deck,
I do not know;
then his 52' is too big, could he shrihk it some?


Getting close.
Sinclair

 

Depends on where you plan to cruise

You will appreciate the raised position and superior visibility if traveling in hot reef strewn areas, where the inside helm station will be severely lacking in visibility and steering from behind those sloped surfaces can be like being baked in a hot oven.

If your cruising grounds will be somewhere it is predominately wet , cold and windy, I agree the inside position is more appealing.

I will have both.
Up top with a wheel and Autopilot remote for the hot calm days enjoying the superior view and a cold beverage and less pleasant days and cooler nights when on passage inside with secondary engine controls and just an autopilot for steerage.

I recently helped on a powercat delivery to Vanuatu and the whole trip, due to leaking hydraulics at the wheel, were done using the Autopilot control head for steerage and it worked a treat.

Thankfully its helm position was about 3 metres from the front windows, so the heat was manageable.

When approaching reef, a higher vantage point would have been invaluable.

 

BAR is blade area ratio. The ratio of the area of the blades to the area of the disc swept by the blades.

Wageningen is a well known series of water propellers that has a large amount of test data in the form of charts that allows you to work out what a particular propeller will achieve in open water conditions.

The simplest way to get an idea of the best prop to suit your application is to use JavaProp. It is quite easy to use and can be run from this web site:
http://www.mh-aerotools.de/airfoils/javaprop.htm
Click on "The Applet" and it will start a jave application. I can tell you how to set the parameters similar to what your cat requirements are per attached.

This allows you to quickly appreciate the interaction of the variables. For example what is the sensitivity to diameter and RPM. You need to check that the resulting shape will have the required strength. Also at higher speed, cavaitation can be a factor and JavaProp does not cater for this condition.

In the past there was not a lot of attention paid to efficiency on recreational power craft but that is shifting. The hull design you are chasing will be reasonably easily driven. The best prop is likely quite different to what is regarded as typical.

The props I make for my own little craft and design for, or recommend to, others are able to get efficiencies well over 80%. This is a recent example of one:
http://www.youtube.com/watch?v=jh_RhkejWLw
Not too shabby for less than 1HP.

Denny also posted some interesting test data at post #252 on this thread:
http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996-17.html
It compares a model aircraft prop with a standard Minn Kota prop along with a few other efficiency improvements not directly related to the prop. However anything you do that can improve efficiency can have indirect benefits like reduced power, lower engine weight, less drag from lower engine/gearbox weight and so it goes on.

Low hull weight is desirable where it does not compromise integrity as it will reduce overall costs up to the point where you start to use exotic materials or spend more money on designing detail than just sticking with something more robust.

More exotic reinforcements like carbon fibre that I use on my boats can save significant weight but they come at a high price. I doubt that you would want to go to these. Some of the weights being achieved with large boat hulls amaze me but they cost a king's ransom.

One last thing - interesting that Foreign Affair has a beam of 6.75m - close to GODZILLA result.

Rick W

 

Managua,
Rick,

My apologies for answering your last post a tad late, discovered it now!

Thanks for the infos: BAR, Wageningen,
"Javaprop" in which i will dwell soon;
80 % effiency: what an achievement and a saving in all aspects.

Similarities: Beam of Foreign Affair and your results for my project, Thanks again.

Safe byci-cat!
Sinclair