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Old 29-12-2015, 10:57   #16
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Re: Powering PDQ 44

I don't know why many people on this site reply to a persons inquiry/question if they have nothing valid to contribute to solving the posters problem. Nulik, I am very interested in fuel economy also. From my research the PDQ Antares came with engines ranging from 28 to 40 hp. Fuel consumption for these different can be hard but not impossible to find.
A good way to get info is on YouTube. Search the boat in question and PM the vids poster/uploader for the info. Don't forget to like the vid and maybe subscribe to his/her channel.
This guy claims these numbers on a PDQ 44 with Yanmar 3gm30 engines.
The 40s should be about 10 to 20% higher
One engine fuel curve ...
RPM Speed (calm) Fuel
2400 4.5 .5 Gph
2750 5 .79 Gph
3000 5.5 1.05 Gph
3200 6 1.34
3400 6.5 1.71 Gph

this is the link
Cruising speed - PDQ Owners Forum

KORITHFW Greg
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Old 30-12-2015, 17:21   #17
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Re: Powering PDQ 44

The hull speed of a 44 foot vessel will be about 8.9 knots. Going faster than that will require extreme power. The change from 30 hp to 40 hp will increase speed about 10%. Assuming you have the same displacement (a strong assumption) as the PDQ 44 cited in reply #16, you could go about 10% faster. It's not clear from the data shown whether or not 6.5 knots is his maximum speed. At least you should be able to go 7.1 or 7.2 knots with the same displacement.

The advice above about relying on good weather forecasting and motor sailing if you need to get away from a named storm is good advice.
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Old 30-12-2015, 20:55   #18
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Re: Powering PDQ 44

Well, not quite. Tank testing has shown that at higher LWL:BWL ratios, above around 8:1, bow wave propagation begins to reduce, and at higher ratios reduces to the point that the theoretical hull speed ceases to exist.


Most cruising cat's have LWL:BWL ratios of 10:1 or higher.


Which is why you see often cat's and tri's sailing at far higher speeds than theoretical hull speed, without planing.
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Old 30-12-2015, 21:30   #19
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Re: Powering PDQ 44

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Originally Posted by 44'cruisingcat View Post
Well, not quite. Tank testing has shown that at higher LWL:BWL ratios, above around 8:1, bow wave propagation begins to reduce, and at higher ratios reduces to the point that the theoretical hull speed ceases to exist.


Most cruising cat's have LWL:BWL ratios of 10:1 or higher.


Which is why you see often cat's and tri's sailing at far higher speeds than theoretical hull speed, without planing.

If your unsure of the LWL:BWL ratio of your cat or one your interested in, go to multihulldynamics.com. Great website that will give you some insight into the performance and stability figures on a lot of multis.


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Old 31-12-2015, 07:17   #20
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Re: Powering PDQ 44

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Originally Posted by 44'cruisingcat View Post
Most cruising cat's have LWL:BWL ratios of 10:1 or higher.

You need to get up into the other hemisphere. Up there, the typical cruising cat is probably 8:1 or less.

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Old 31-12-2015, 07:20   #21
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Re: Powering PDQ 44

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Originally Posted by mcarling View Post
It's not clear from the data shown whether or not 6.5 knots is his maximum speed. At least you should be able to go 7.1 or 7.2 knots with the same displacement.

The data were for one engine only. It just peters out before hull speed. Maybe the prop is too small (it goes right up to rpm limit).

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Old 31-12-2015, 07:24   #22
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Re: Powering PDQ 44

Quote:
Originally Posted by goofienewfie63 View Post
I don't know why many people on this site reply to a persons inquiry/question if they have nothing valid to contribute to solving the posters problem. Nulik, I am very interested in fuel economy also. From my research the PDQ Antares came with engines ranging from 28 to 40 hp. Fuel consumption for these different can be hard but not impossible to find.
A good way to get info is on YouTube. Search the boat in question and PM the vids poster/uploader for the info. Don't forget to like the vid and maybe subscribe to his/her channel.
This guy claims these numbers on a PDQ 44 with Yanmar 3gm30 engines.
The 40s should be about 10 to 20% higher
One engine fuel curve ...
RPM Speed (calm) Fuel
2400 4.5 .5 Gph
2750 5 .79 Gph
3000 5.5 1.05 Gph
3200 6 1.34
3400 6.5 1.71 Gph

this is the link
Cruising speed - PDQ Owners Forum

KORITHFW Greg

This fuel consumption is quite close to what we get with our Volvo MD2030 (29hp, 3600rpm) on a Manta 40. The speeds are a bit low for us by half a knot.

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Old 31-12-2015, 08:23   #23
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Re: Powering PDQ 44

Since the Yanmar 3gm30 engines have a max rpm of 3600 and a max continuous rpm of 3400, I would say the numbers are accurate for the boat. Bearing in mind that these numbers are real world and not speculation. It would be interesting to see the numbers with a larger prop or more pitch.
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Old 31-12-2015, 14:15   #24
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Re: Powering PDQ 44

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Originally Posted by colemj View Post
You need to get up into the other hemisphere. Up there, the typical cruising cat is probably 8:1 or less.

Mark
Er, no, I think I'll stick to this hemisphere thanks...

Happy new year BTW.
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