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Old 02-28-2011, 11:03 AM   #21
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RE: Twin to Single conversion- Oh My!

Quote:
nomadwilly wrote:*There was a GB 36 that has had it's 2 120 hp Lehmans removed and 2 55hp Yanmars installed. The boat (I think) produced was considerably more economical to run and more seaworthy as well.
********* Can't wait to hear what Marin says about the "more seaworthy" part.

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Old 02-28-2011, 06:13 PM   #22
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RE: Twin to Single conversion- Oh My!

It's simple John. Take a ton or so out of a big old heavy boat and it will go faster, run drier and not bury it's bow so much, be smoother, *be more economical, probably make less noise and be less likely to broach. The engines will be much less obnoxious and Marin won't like that. Two D8 Cat engines would make him much happier.
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Old 03-04-2011, 01:44 PM   #23
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RE: Twin to Single conversion- Oh My!

Eric,** What about the Center of Gravity?* Without the ballast of all that iron the boat would be lighter and float higher.

Adding ballast would defeat the purpose.

So the higher CG would be no problem?

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Old 03-06-2011, 04:11 PM   #24
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Twin to Single conversion- Oh My!

John,
I now have a response from one of the best NAs on the forum.
However he's not too egar to stick his neck out too far as I was unable to be specific enough. Also he made reference to "the main deck" and I for one was not sure what he meant. Anyway he said that the vertical CG (VCG) is on most"modern motoryachts" is approximately 1/2 WL to main deck height. He claims that to be quite vague and general as there are so many variables but none the less that's much higher than I had thought unless the "main deck" is the same as the salon, after decks and aft deck. In the GB example the engines on the twin are 6" higher than the single but VCG is close to only 1" different. All of this seems odd to me but let's see what he says about where the main deck is.***** Later


His next post showed the CG to be about 12" above the WL. Still higher than I thought. Now
I like my 2 tons of ballast even more.......and no FB. ha ha


-- Edited by nomadwilly on Sunday 6th of March 2011 09:24:09 PM
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Old 03-06-2011, 10:18 PM   #25
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RE: Twin to Single conversion- Oh My!

Eric,
Are you sure you don't really long for a twin screw, flybridge boat with 1,500 horsepower burning 75 GPH??? Just think how fast you could zip around Thorne Bay and the view you would have from up high on the bridge!
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Old 03-06-2011, 10:38 PM   #26
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RE: Twin to Single conversion- Oh My!

Quote:
Woodsong wrote:

Eric,
Are you sure you don't really long for a twin screw, flybridge boat with 1,500 horsepower burning 75 GPH??? Just think how fast you could zip around Thorne Bay and the view you would have from up high on the bridge!
TonyYour ability to read between the lines and discover the true Eric, the Eric that Eric didn't know was there, is amazing. I imagine Eric breaking a tear right now, as he realizes that what you say is true.*

*
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Old 03-07-2011, 06:05 AM   #27
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RE: Twin to Single conversion- Oh My!

Quote:
nomadwilly wrote:
I like my 2 tons of ballast even more.......and no FB. ha ha

**********Eric, Seems like boats can be pretty forgiving as to the weight and #of engines.

********* On a smaller boat the FB is a lot of free realestate, and does not have to be heavy.

********* If conditions are bad it is easy to stay off the bridge and keep all the crew weight low.

********* On big boats the bridges have tons of furniture, outdoor kitchens and 8 person hot tubs.*

********* But they can always lose the helicopter if things get rough and take a trip to the mall or something. ha ha.

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Old 03-07-2011, 06:22 AM   #28
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RE: Twin to Single conversion- Oh My!

Quote:
Carey wrote:

*
Tony
Your ability to read between the lines and discover the true Eric, the Eric that Eric didn't know was there, is amazing. I imagine Eric breaking a tear right now, as he realizes that what you say is true.*

*


*



Caery,

They don't call me the "Dr. Phil" of boating for nothing! *
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Old 03-07-2011, 09:11 AM   #29
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Twin to Single conversion- Oh My!

Nail on the head Carey but I just can't afford it. I'd have a 53' Krogen Express. Or a 31' Bertram w twin 375hp. Or a Shannon SRD 38. Or a Mainship Pilot 34. Or a Sterling Atlantic 43. Or an Eagle 40. But the one I really want is a slow boat***** ...Nordhavn 46.

John,
The FB real estate is NOT free. One pays the price of higher CG and windage. Do you really think a typical FB is light? My anti-FB stand is not as bad as most of you think. I DO think most FBs on a 26 or 28' boat is bad design but on a 36' typical trawler it's more of a preference to me. A boats purity of design is more important to me than most. I'll never say a GB is more seaworthy with it's FB than without it though. But if I had a 42 GB I'd not remove the FB.

-- Edited by nomadwilly on Monday 7th of March 2011 10:23:52 AM
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Old 03-07-2011, 12:58 PM   #30
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RE: Twin to Single conversion- Oh My!

But if I had a 42 GB I'd not remove the FB.


Depending on how the boat was built it might be self removing.

I had to create a cored roof for a 42 Californian , as the mounts for the FB , deck boxes and seats , leaked into a ply "composite" .

Screw removal was not required to strip the old stuff off.
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Old 03-07-2011, 01:10 PM   #31
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RE: Twin to Single conversion- Oh My!

Eric,* I think if I had a big boat I would skip the Flybridge as the pilothouse would be so commodious the whole party could enjoy the view and lounge or dine while the helmsman could bask in their company.

You get the picture.*** JohnP
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Old 03-07-2011, 03:48 PM   #32
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RE: Twin to Single conversion- Oh My!

A well laid out FB on a nice warm day is lots of fun. On ours we have:
--Seating for 8+
--All the necessary instruments
--Map table
--Full layout dayberth for snoozing
--Enclosed or open dependent upon temps
--Great 360 degree vision for spotting things
--Seaview glass window with wiper in the front for visibility in rain
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Old 03-07-2011, 06:44 PM   #33
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RE: Twin to Single conversion- Oh My!

And Tom,
Your boat's plenty big and wide enough to support that FB.
If you gave me your boat I wouldn't remove the FB either.
If a FB weighs next to nothing I would'nt critisize it even on
a 25' boat if was'nt too high up. I guess I've made my point
that the FB dosn't help seaworthyness but in most all conditions
the FB dosn't make the boat unsafe either. If it's fun to poke
at me about this I'll poke back untill everyone's asleep.
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Old 03-07-2011, 08:48 PM   #34
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RE: Twin to Single conversion- Oh My!

If no CG issues with a FB, how about windage?

With*an Oxygen Tent (A.K.A. FB)*extending an extra 6 to 7 feet above, would that not attribute to windage?

Then wouldn't extra weight/ballast have to be placed below the CG to offset the windage?
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Old 03-07-2011, 08:53 PM   #35
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RE: Twin to Single conversion- Oh My!

El Sea,

Big time


Big time


Would be good but almost never done.
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Old 03-07-2011, 09:59 PM   #36
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RE: Twin to Single conversion- Oh My!

El Sea

When we dock in 20 - 25 knots the windage from the fly bridge enclosure doesn't seem an issue. But our DeFever is very deep and heavy. I've watched many lighter boats, including my previous ones,* blow around in 10 knots with no flybridge.
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Old 03-08-2011, 04:36 AM   #37
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RE: Twin to Single conversion- Oh My!

For folks that run the AICW a fly bridge might slow your progress to sail 6K cruise speeds.

IF you need a lift on every bridge it is common for the tender to assemble a pack , rather than grant individual OPENINGS.

SO you get to mill about for a half hour as the snail sail boats gather from the last bridge opening.

While it has a great effect on interior volume (a religion for some) our 12ft bridge air height probably saves 3 or 4 days on an ICW migration.

Decide weather the oxygen tent will be a bother where you live and cruise .
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Old 03-08-2011, 09:46 PM   #38
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RE: Twin to Single conversion- Oh My!

Quote:
JohnP wrote:******* There were tons of twin screw trawlers built in the hay days back in the 70s and 80s.** It is possible there could be a huge glut on the market as these boats age.
The little guy $$$ is being squeezed out of boating and the big guy $$$ will want something newer than these 30+ year old boats.

******* As these boats sit on the market and deteriorate their value will plummet.
Ahh, do you know what a Monk 36 sold for in 1983?* And what one in good condition sells for today?* not including inflation, that is a pretty good deal.

Boats are wierd.* Something you don't need and can last forever if taken care of properly.* Who would buy that?

*
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