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Old 12-28-2012, 04:19 AM   #1
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Post Bulbous Bow - Anyone Done One???

Has anyone on this forum ever put a bulbous bow on a trawler? I'm rebuilding a 38' custom fiberglass trawler based upon a Ron Rawson hull, doing a 4' hull extension under the swimstep, changing the superstructure from a tri-cabin to a Europa style, etc. I'm going to add a bulbous bow using a 20" diameter sono-tube and I was wondering if anyone had any plans, specs, formulas, calculations, etc.
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Old 12-28-2012, 05:58 AM   #2
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Not me, but all the reading and tests I've seen say it won't do you any good, nor harm.
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Old 12-28-2012, 06:13 AM   #3
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Some of the stuff I've read says the boat has to be about 42-45' long before you see much of a gain - I'm 38' but I'm doing a 3'6" hull extension under the swim step so I'll end up about 41' approximate. The other thing that I'm also hoping to gain is more flotation in the bow as I've always been just a little heavy to the bow and I'm also going to an all-chain anchor rode which is going to add a few hundreds pounds right on the nose - which the bulbous bow would offset.
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Old 12-28-2012, 06:50 AM   #4
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Really get some use out of it by putting a sonar in there...
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Old 12-28-2012, 06:57 AM   #5
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Yeah - don't think I haven't thought of that - I'm already putting a bow and stern thruster on. And for a few thousand more......
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Old 12-28-2012, 07:43 AM   #6
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A bulb is only effective for efficiency enhancement within a very narrow speed range, outside that range it only creates drag and you lose more than you gain by having it.

Maersk, the world's largest containership operator is making drastic modifications on the bulbs fitted to their ships because they discovered this after instituting what the industry calls "slow steaming" to save fuel.

They look cool though and everyone who sees the bulb will be impressed and it may add some bouyancy but is is worth it? You won't know until you either tank test your hull before and after or find out by experience.
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Old 12-28-2012, 11:22 AM   #7
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Rick:
I would think he would need to do the stern hull extension first, find out what effect that has on performance, over a few hundred hours of use, then do the bulbous bow. To do it all at once will completely confound any ability to know the effect of any one component of the modifications.
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Old 12-28-2012, 11:37 AM   #8
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Yea I got one last month.
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Old 12-28-2012, 11:44 AM   #9
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Eric:
Complete with forward looking sonar and a thruster (doors closed in your picture) I presume.
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Old 12-28-2012, 11:52 AM   #10
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I have look at them more for protection of the hull as most on the long range boats especially from Alaska have some bow damage at the water kine. As for performance most say they have not noticed much. I have also looked at them as the RW 58 bow is a little light with the wide flare, I been told by other 58, so maybe to weight it down. Anyway if I was going to added it would be to protect the bow and to make the Eagle look meaner/uglier.
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Old 12-28-2012, 12:02 PM   #11
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Phallic Bows

This is the bow on the N57 I was on for almost three weeks... the dolphins LOVED thething and would spend hours eying the thing. I had the forward cabin and noticed the thing made noise both ways when the boat bobbed in waves at anchor. The water normally makes noise ( inside the hull ) when the bow goes down in a wave.. this actually made more noise on the upper motion. From what I had read in the past they only make a difference in a very narrow speed spectrum. Nordhavn has not installed them on their new 64's so they must have not made enough difference to warrant installation.
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Old 12-28-2012, 12:24 PM   #12
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Quote:
Originally Posted by hollywood8118 View Post
This is the bow on the N57 I was on for almost three weeks... the dolphins LOVED thething and would spend hours eying the thing. I had the forward cabin and noticed the thing made noise both ways when the boat bobbed in waves at anchor. The water normally makes noise ( inside the hull ) when the bow goes down in a wave.. this actually made more noise on the upper motion. From what I had read in the past they only make a difference in a very narrow speed spectrum. Nordhavn has not installed them on their new 64's so they must have not made enough difference to warrant installation.
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that looks cool!
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Old 12-28-2012, 01:01 PM   #13
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Actually I think my bulbous bow extension would be better spent at the stern if the propeller didn't come out of the water and in Willy's case I don't think it would. My knowledge of BBs is limited but it would seem to me the issue is the effective length of the hull so why not the stern ... or bow and stern.

As I usually say about extended OB mount brackets ... why not just extend the whole boat? And that's what I'd like to do w Willy. But it's already been done. The 32' Fales boat is a lengthened Willard. Lengthened by adding a 2' section to the middle. Probably more effective that my BB 30'.
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Old 12-28-2012, 01:32 PM   #14
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Nose art on the BB's is definitely the way to go. The Flying Tigers shark face would be my first choice.
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Old 12-28-2012, 02:17 PM   #15
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Marshall Islands-registered, 374-meter, 12-knot crude oil tanker Melodia shows its fat/tall bulbous nose after unloading in Martinez:



Is the shape dependent upon hull shape or what?
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Old 12-28-2012, 03:47 PM   #16
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That's quite a lump!
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Old 12-28-2012, 04:40 PM   #17
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Its fun watching those big guys when they leave Vancouver loaded and get up a head of steam heading south for Juan de Fuca. They push up a huge bump of water a long ways ahead of them.

I've tried to capture it in pictures but it never looks as impressive in the picture as it does in real life.

There was a fishing boat at Platypus this spring that they had stretched and added a bulbous bow. Maybe that is justified on a commercial vessel although I'd have to see the numbers. On a toy boat I think we'd be better off to sell and replace the vessel rather than getting into that kind of major renovations.
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Old 12-28-2012, 04:45 PM   #18
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Interestingly, there is a shipwreck off Virginia (ethanol tanker "Bow Mariner") with a pair of bulbous protrusions that resemble a women's breasts. Only double I'm aware of. No Idea if they were a success or not.

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Old 12-28-2012, 05:11 PM   #19
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Wait a Minuit. They resemble a womans Brest only double??

I Have yet to see a single.

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Old 12-28-2012, 06:52 PM   #20
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Maybe the owner of the tanker was a "Boob" man!
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