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Old 10-14-2015, 07:16 PM   #121
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Originally Posted by O C Diver View Post
Yup, and all that space on both sides of the engine.
Yeah, all that space is just wasted. Unless you want to service the engine. Again, I understand some owners consider that "optional".

Oh, and then there's the ability to add sound insulation when the engine sits lower - and there's only one of them. But hey, if you're really proud of how your engines sound and want to share that with your passengers, then that wouldn't be a feature you'd want.

And doubling the number of hull penetrations - everyone knows that you increase seaworthiness by punching additional holes in your boat. That's just common sense, right?


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Old 10-14-2015, 07:18 PM   #122
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Tough game to play Mark. A sad one too. Became familiar with the Pilatus story and airplane a few years through a nephew who regularly flew one. While he was doing that gig another one went down in MT with 14 on board. Unfortunately sad stories of this kind involving small airplanes never seem to let up.
You're confusing me. The Hellcat I'm referring to is a WWII fighter plane with a single pilot and no others aboard.
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Old 10-14-2015, 08:53 PM   #123
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Well I like a big rudder too, but that's just me - others may not be as picky about what direction they're going.

I'm also kinda partial to a low COG and rolling moment. And a flat shaft angle, and a big prop, well down in the water. Again, that's just me - others might be happy squirreling along with marginal efficiency and control.

Oh, and I like large tanks. You know, for range.

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Keith you don't know how many people you have just PO'd with these truisms.
Noten psses me off regarding other boater's desires, needs, haves, wants, or suggestions.

Hope whatever I mention does not pss any others off. However, if any of what I post does... oh well, grow up! This is just a marine forum. Pretty darn good one at that - IMO.

Happy Trawler Forum Daze! - Art
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Old 10-17-2015, 12:46 AM   #124
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Well. . . .

I haven't been on the forum for about a month.

But I see I haven't really missed a thing....
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Old 10-17-2015, 03:46 AM   #125
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Well. . . .

I haven't been on the forum for about a month.

But I see I haven't really missed a thing....
What a coincidence! Neither have we


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Old 10-17-2015, 06:13 AM   #126
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Well. . . .

I haven't been on the forum for about a month.

But I see I haven't really missed a thing....



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What a coincidence! Neither have we

Keith
Guess we've mostly said what can be said... and, repeatedly - at that!

Ho Hum
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Old 10-17-2015, 07:55 AM   #127
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Quote:
Originally Posted by Edelweiss
Well. . . .

I haven't been on the forum for about a month.

But I see I haven't really missed a thing....





Guess we've mostly said what can be said... and, repeatedly - at that!

Ho Hum
Have we settled the point that singles are better and people with twins are looking for more of a better thing?

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Old 10-17-2015, 11:17 AM   #128
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Singles are better if that's all you can afford.
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Old 10-17-2015, 11:42 AM   #129
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You know...that emoticom really hits home doesn't it?
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Old 10-17-2015, 11:44 AM   #130
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Singles are better if that's all you can afford.
Exactly.

I'm surprised nobody has mentioned that twins use nearly double the fuel at displacement speeds.

Rule of thumb:
32'/6 tons/ single[200hp] 2 gals/hr@ 7 kts: 3-4 mpg.
32'/6-7 tons/twin[2x200hp] 4gals/hr@ 8kts: 2 mpg or less.
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Old 10-17-2015, 01:50 PM   #131
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And doubling the number of hull penetrations - everyone knows that you increase seaworthiness by punching additional holes in your boat. That's just common sense, right?
I find all this worry about extra hull penetrations amusing. It's really such a none issue. And of course twin engines don't double the total hull penetrations in a vessel compared to a single. They add like what, two?

There are plenty of good reasons to choose a single engine over a twin. But worrying about added hull penetrations isn't really one of them.
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Old 10-17-2015, 02:10 PM   #132
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Have we settled the point that singles are better and people with twins are looking for more of a better thing?

Ted

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Singles are better if that's all you can afford.
Eric and Ted - You two = "Twins"... in the way you calculate things - LOL - Art
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Old 10-17-2015, 02:27 PM   #133
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Exactly.

I'm surprised nobody has mentioned that twins use nearly double the fuel at displacement speeds.

Rule of thumb:
32'/6 tons/ single[200hp] 2 gals/hr@ 7 kts: 3-4 mpg.
32'/6-7 tons/twin[2x200hp] 4gals/hr@ 8kts: 2 mpg or less.
You better calc that again!

Twins (same exact engines as the single in same exact boat as the single) are not twice fuel consumption at displacement speed with both engines running and needing less hp each than the single needs to reach speed. Especially when you cruise at or under full displacement speed with one twin shut down. Also, twins are ok in a full displacement hull but really not needed... although they do serve for spare engine and improved close quarters maneuverability.

Twins can become quite useful on SD hulls and very useful on Planing hulls.

Cheers! - Art
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Old 10-17-2015, 02:48 PM   #134
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You better calc that again!

Twins (same exact engines as the single in same exact boat as the single) are not twice fuel consumption at displacement speed with both engines running and needing less hp each than the single needs to reach speed. Especially when you cruise at or under full displacement speed with one twin shut down. Also, twins are ok in a full displacement hull but really not needed... although they do serve for spare engine and improved close quarters maneuverability.

Twins can become quite useful on SD hulls and very useful on Planing hulls.

Cheers! - Art
That's all very well in your Tolly with gass engines that don't mind idling along at 500 revs...!

Given that a big diesel will need a few revs/load not to glaze the cylinders, a twin 200 HP boat would probably have to use 1200-1500revs which will burn at least 2 gal per engine.

Of course you could cruise with one engine, but figures I've seen on the boat design forum show virtually no gain in mpg because of prop drag....

The big question: has anyone got a 32' or larger twin engined trawler that can beat 2 mpg?
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Old 10-17-2015, 03:28 PM   #135
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That's all very well in your Tolly with gass engines that don't mind idling along at 500 revs...!

Given that a big diesel will need a few revs/load not to glaze the cylinders, a twin 200 HP boat would probably have to use 1200-1500revs which will burn at least 2 gal per engine.

Of course you could cruise with one engine, but figures I've seen on the boat design forum show virtually no gain in mpg because of prop drag....

The big question: has anyone got a 32' or larger twin engined trawler that can beat 2 mpg?
Yup – Me… that of course is… if our simple to maintain and inexpensive to own or replace gasoline engines are allowed into this discussion!

We get 2.75 to 3 nmpg at 5 +/- knots by running either engine at well under 2k rpm with one shut down and left in freewheel-prop due to that being OK with BW Velvet Drive trans.

With twins running us at 6.5 to 7 knots, i.e. just below hull speed (displacement-running hull speed on our boat calcs at 7.58 knots) we get close to 2 nmpg

Cruising on full plane at 16 to 17 knots we get 1 +/- nmpg.

WOT at 22 to 23 knots = OMG nmpg



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Old 10-17-2015, 03:31 PM   #136
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Originally Posted by Rustybarge View Post
Exactly.

I'm surprised nobody has mentioned that twins use nearly double the fuel at displacement speeds.

Rule of thumb:
32'/6 tons/ single[200hp] 2 gals/hr@ 7 kts: 3-4 mpg.
32'/6-7 tons/twin[2x200hp] 4gals/hr@ 8kts: 2 mpg or less.

Well there you go, proof positive of something
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Old 10-17-2015, 04:04 PM   #137
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Yup – Me… that of course is… if our simple to maintain and inexpensive to own or replace gasoline engines are allowed into this discussion!

We get 2.75 to 3 nmpg at 5 +/- knots by running either engine at well under 2k rpm with one shut down and left in freewheel-prop due to that being OK with BW Velvet Drive trans.

With twins running us at 6.5 to 7 knots, i.e. just below hull speed (displacement-running hull speed on our boat calcs at 7.58 knots) we get close to 2 nmpg

Cruising on full plane at 16 to 17 knots we get 1 +/- nmpg.

WOT at 22 to 23 knots = OMG nmpg



5 kts is snail pace!!!
Sorry forgot to say at 7 kts in a single screw; anything slower is like watching paint dry!

Your numbers look like 2 mpg....
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Old 10-17-2015, 04:07 PM   #138
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Well there you go, proof positive of something
Yep, that twin engines use x2 fuel consumption because you have to use higher revs to keep engines working well and that means 7-8 kts.
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Old 10-17-2015, 04:23 PM   #139
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We get 2.75 to 3 nmpg at 5 +/- knots by running either engine at well under 2k rpm with one shut down and left in freewheel-prop due to that being OK with BW Velvet Drive trans.

With twins running us at 6.5 to 7 knots, i.e. just below hull speed (displacement-running hull speed on our boat calcs at 7.58 knots) we get close to 2 nmpg


Thats incredible! What do you use to measure flow?

With twin 5.7L Crusader gas on a 29' Phoenix and a calibrated Floscan, on one engine, the best I could ever get was 5 gph at 1600 rpm for 5 knots for 1 nmpg.
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Old 10-17-2015, 04:25 PM   #140
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5 kts is snail pace!!!
Sorry forgot to say at 7 kts in a single screw; anything slower is like watching paint dry!
"....
But, But... running w/ a 3 knot current doing 5 knots through water surface = 8 knots OL speed -

Anyway... With our planning hull Tolly... we like to cruise 16 to 17 knots on full plane. Over twice as fast as the top FD hull speed for same size boats. As you know "Time Is Money!" And... although, as you say, "5 kts is snail pace"... so is 7 knots simply a crawl for us. We only go slow when we want to; rather than because we always have to!
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