Hi Garry,
This is Graham Pfister from Vancouver, Canada, not quite as far North as
Bob, but still on the Pacific Coast. Sorry I'm so late buying into this but
I'm new to this site and still learning the ropes; thanks for your help
Georgs, I hope I've got it right this time.
As I see it you have planning hulls which means they operate best in smooth
water and with the right power to weight ratio it will go fast and be fairly
efficient.
The table below is for 48' vessels, but disregard all the numbers and what
it will then show you is that a planning power catamaran, correctly designed
and built, will produce a performance something similar to the blue curve.
This means you burn more fuel to get the boat up on the plane and once over
the 'hump' fuel burn drops back as speed increases. I've inserted the table
in this email, but I'm not sure if it will stay. It shows very graphically
how a planning catamaran performs, so if it doesn't appear and you want me
to send it to you drop me an email to graham@trawlercatmarine.com
Data Supplied by Len Gilbert, Diesel craft Evaluations
The problem, as I mentioned above, is that you need fairly smooth water to
stay above the hump. If you don't know what speed the boat planes at then
try it on a calm day to establish the best rpm's. Full rpm's will get you
up to the hump quickly and then as the nose starts to drop down and the boat
starts leveling out slowly back off the power. Trim tabs help you get on
the plane quicker if you have them.
Weight is the enemy of planning hulls, as is weight distribution. Big heavy
motors on the back don't make it any easier to get up on the plane. The
heavier the boat the more fuel you need to burn and the higher speed you
need to lift it all over the hump. Keeping the weight off, including the
lighter engines, will all add up to fuel saving and a lower planning speed.
Oh and don't worry about building up a bow wave, it all happens below the
hump, once you're on the plane it's clear sailing, or in this case clear
powering, without pushing a bow wave.
Pounding will depend on the conditions. If it's bumpy then it will pound
and it's a matter of how much pounding you can put up with before you pull
back the power and become a wallowing boat pushed about at the whim of the
waves.
Pounding comes in two forms. The first is when you drive into a wave and it
slams up under the deck or when the boat slams down off the top of a wave.
These can cause an unnerving shudder and should be taken seriously as it can
damage the boat. The second pounding is not actually pounding at all, its
waves slamming into the side of the hulls at the bow, especially the inside
of the leeward hull. It sounds loud and can also cause the boat to shudder
but it's mostly just a lot of noise as the hull acts like a piano sounding
board amplifying the noise. After a lot of pounding it's always a good idea
to check the under wing deck and hull joins for any stress cracks and deal
with any as soon as possible.
I hope this helps,
Cheers,
Graham
-----Original Message-----
From: power-catamaran-bounces@lists.samurai.com
[mailto:power-catamaran-bounces@lists.samurai.com] On Behalf Of
power-catamaran-request@lists.samurai.com
Sent: Thursday, September 24, 2009 9:00 PM
To: power-catamaran@lists.samurai.com
Subject: Power-Catamaran Digest, Vol 53, Issue 12
Send Power-Catamaran mailing list submissions to
power-catamaran@lists.samurai.com
To subscribe or unsubscribe via the World Wide Web, visit
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or, via email, send a message with subject or body 'help' to
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You can reach the person managing the list at
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When replying, please edit your Subject line so it is more specific
than "Re: Contents of Power-Catamaran digest..."
Today's Topics:
- Re: Outside the box or am I barking mad? (Flurohood)
Message: 1
Date: Fri, 25 Sep 2009 11:36:22 +1200
From: "Flurohood" flyingbuss@xtra.co.nz
To: "Power Catamaran List" power-catamaran@lists.samurai.com
Subject: Re: [PCW] Outside the box or am I barking mad?
Message-ID: F884F6976FAC4BB58C0E44929A2BE494@GarryPC
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Hi Guys,
Thanks for the input it is much appreciated!
We are off down to Auckland to look at boats this weekend and the cat will
be one of them.
After all your input I raised my concerns with the vendor..
He stated that with one 200hp 2 stroke running at 2700 rpm the boat runs
along at 9knots..With both running at 2300 he gets 9 also.
Interestingly with the 4 stroke high thrust engines thrust is stated to be
60% greater than equivalent 2 strokes. Giving me approx thrust either side
equivalent to 2 90s thru the mid range (to4500rpm).
That is not to far off his one 200hp (older) 2 stroke . This is thrust and
does not compare with wot at which point the 200 will just keep going
faster.
Upshot is that I will likely be able to run at 8-9 staying in my fuel
efficient 3000-4500 range.
I am meeting with engine reps from Yamaha and Honda to discuss further.
Handling he states is fine but does admit to hull slap in significant waves
although not bone jarring.
He states that coming off head on only slightly towards the shoulder smooths
things out at low speeds.
This I do in my current boat in any case except for the odd headland
rounding.
Good news is I try the boat sunday and at least 15knots of wind is expected
and the Hauraki gulf should poduce some of it's
steep chop for us to play in!
The boat listing is here if any of you want to take a look.....
http://www.trademe.co.nz/Trade-Me-Motors/Boats-marine/Motorboats/auction-242
544140.htm
Cheers. Garry.
Mangonui
New Zealand.
Power-Catamaran Mailing List
End of Power-Catamaran Digest, Vol 53, Issue 12
[demime 1.01d removed an attachment of type image/jpeg which had a name of image001.jpg]
Hi Garry,
This is Graham Pfister from Vancouver, Canada, not quite as far North as
Bob, but still on the Pacific Coast. Sorry I'm so late buying into this but
I'm new to this site and still learning the ropes; thanks for your help
Georgs, I hope I've got it right this time.
As I see it you have planning hulls which means they operate best in smooth
water and with the right power to weight ratio it will go fast and be fairly
efficient.
The table below is for 48' vessels, but disregard all the numbers and what
it will then show you is that a planning power catamaran, correctly designed
and built, will produce a performance something similar to the blue curve.
This means you burn more fuel to get the boat up on the plane and once over
the 'hump' fuel burn drops back as speed increases. I've inserted the table
in this email, but I'm not sure if it will stay. It shows very graphically
how a planning catamaran performs, so if it doesn't appear and you want me
to send it to you drop me an email to graham@trawlercatmarine.com
Data Supplied by Len Gilbert, Diesel craft Evaluations
The problem, as I mentioned above, is that you need fairly smooth water to
stay above the hump. If you don't know what speed the boat planes at then
try it on a calm day to establish the best rpm's. Full rpm's will get you
up to the hump quickly and then as the nose starts to drop down and the boat
starts leveling out slowly back off the power. Trim tabs help you get on
the plane quicker if you have them.
Weight is the enemy of planning hulls, as is weight distribution. Big heavy
motors on the back don't make it any easier to get up on the plane. The
heavier the boat the more fuel you need to burn and the higher speed you
need to lift it all over the hump. Keeping the weight off, including the
lighter engines, will all add up to fuel saving and a lower planning speed.
Oh and don't worry about building up a bow wave, it all happens below the
hump, once you're on the plane it's clear sailing, or in this case clear
powering, without pushing a bow wave.
Pounding will depend on the conditions. If it's bumpy then it will pound
and it's a matter of how much pounding you can put up with before you pull
back the power and become a wallowing boat pushed about at the whim of the
waves.
Pounding comes in two forms. The first is when you drive into a wave and it
slams up under the deck or when the boat slams down off the top of a wave.
These can cause an unnerving shudder and should be taken seriously as it can
damage the boat. The second pounding is not actually pounding at all, its
waves slamming into the side of the hulls at the bow, especially the inside
of the leeward hull. It sounds loud and can also cause the boat to shudder
but it's mostly just a lot of noise as the hull acts like a piano sounding
board amplifying the noise. After a lot of pounding it's always a good idea
to check the under wing deck and hull joins for any stress cracks and deal
with any as soon as possible.
I hope this helps,
Cheers,
Graham
-----Original Message-----
From: power-catamaran-bounces@lists.samurai.com
[mailto:power-catamaran-bounces@lists.samurai.com] On Behalf Of
power-catamaran-request@lists.samurai.com
Sent: Thursday, September 24, 2009 9:00 PM
To: power-catamaran@lists.samurai.com
Subject: Power-Catamaran Digest, Vol 53, Issue 12
Send Power-Catamaran mailing list submissions to
power-catamaran@lists.samurai.com
To subscribe or unsubscribe via the World Wide Web, visit
http://lists.samurai.com/mailman/listinfo/power-catamaran
or, via email, send a message with subject or body 'help' to
power-catamaran-request@lists.samurai.com
You can reach the person managing the list at
power-catamaran-owner@lists.samurai.com
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Power-Catamaran digest..."
Today's Topics:
1. Re: Outside the box or am I barking mad? (Flurohood)
----------------------------------------------------------------------
Message: 1
Date: Fri, 25 Sep 2009 11:36:22 +1200
From: "Flurohood" <flyingbuss@xtra.co.nz>
To: "Power Catamaran List" <power-catamaran@lists.samurai.com>
Subject: Re: [PCW] Outside the box or am I barking mad?
Message-ID: <F884F6976FAC4BB58C0E44929A2BE494@GarryPC>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Hi Guys,
Thanks for the input it is much appreciated!
We are off down to Auckland to look at boats this weekend and the cat will
be one of them.
After all your input I raised my concerns with the vendor..
He stated that with one 200hp 2 stroke running at 2700 rpm the boat runs
along at 9knots..With both running at 2300 he gets 9 also.
Interestingly with the 4 stroke high thrust engines thrust is stated to be
60% greater than equivalent 2 strokes. Giving me approx thrust either side
equivalent to 2 90s thru the mid range (to4500rpm).
That is not to far off his one 200hp (older) 2 stroke . This is thrust and
does not compare with wot at which point the 200 will just keep going
faster.
Upshot is that I will likely be able to run at 8-9 staying in my fuel
efficient 3000-4500 range.
I am meeting with engine reps from Yamaha and Honda to discuss further.
Handling he states is fine but does admit to hull slap in significant waves
although not bone jarring.
He states that coming off head on only slightly towards the shoulder smooths
things out at low speeds.
This I do in my current boat in any case except for the odd headland
rounding.
Good news is I try the boat sunday and at least 15knots of wind is expected
and the Hauraki gulf should poduce some of it's
steep chop for us to play in!
The boat listing is here if any of you want to take a look.....
http://www.trademe.co.nz/Trade-Me-Motors/Boats-marine/Motorboats/auction-242
544140.htm
Cheers. Garry.
Mangonui
New Zealand.
------------------------------
_______________________________________________
Power-Catamaran Mailing List
End of Power-Catamaran Digest, Vol 53, Issue 12
***********************************************
[demime 1.01d removed an attachment of type image/jpeg which had a name of image001.jpg]
