How about this bulbous bow?

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Looks like it is sitting right on its painted waterline. Looks like the bulb is high to me also. What about those roll chocks. Nice boat.
 
I don't like it at all for 6 or 7 reasons or features.

What do you mean stubones99 by "how bout"? The way it looks or the bulb or what? Mark may like the green color. But I think it should be darker.

But rebel if the painted WL is correct that's a significant plus.
 
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If the bulb is underwater at cruise speed, then I guess it is not too high. Looks too high.
 
The benefits of a bulbous bow on a 50' or so trawler are illusory. I recall that for one of the early Nordhavns a bulbous bow was tank tested and showed promise. But in full scale, almost no difference. They gave up on that idea.


David
 
djmarchand said:
The benefits of a bulbous bow on a 50' or so trawler are illusory. I recall that for one of the early Nordhavns a bulbous bow was tank tested and showed promise. But in full scale, almost no difference. They gave up on that idea.


David
Click to expand...


The bulb did reduce hobby horsing allegedly on the N50.

The "maintenance strakes" that they put in around the engine to give better headroom gave a boost to efficiency that surprised them. The bulges in the hull increased water flow somehow IIRC.
 
All the books I've read say that bulbous bows have to be designed for a target speed and are ineffectual at other speeds. They also say that less than 60' length and you can't tell if it's there or not.

The how about thing... It looks like it's hobby horsing all the time. One of the images has the waterline painted coming up and around the bulb. I guess that was a test that didn't work out.
 
djmarchand said:
The benefits of a bulbous bow on a 50' or so trawler are illusory. I recall that for one of the early Nordhavns a bulbous bow was tank tested and showed promise. But in full scale, almost no difference. They gave up on that idea.


David
Click to expand...


Just another "I wanna be like the big boys" feature.
It's like extended OB brackets ... better to just extend the whole boat.
 
The bulbous bow are usually hollow, so the can serve a number of function. Usually speed and range is what comes to mind. However they also protect the bow from damage, and can affect a quick raise fall of the bow, and allow addition weight in the bow.

Everett, Wa use to have a commercial yard, and many or the bulbous bows had gorgeous on damage, and most where empty so the bow did not sink down as far ans quicker recovery. Anyway speed is a factor but there are other benefits.
 
Outboard brackets are designed to take into account for the rise in water after the transom when running. They allow for higher engine mounting allowing for shallower draft without tilting and less drag.


Outboard brackets have a lot of design in the good ones.
 
Psneeld that's an advantage I had'nt thought of.
 
Bulbous bows take many different forms, and are installed for various reasons, not limited to just reducing resistance. The different shaped bulbs work in different ways. Optimizing a bulb for a particular hull and speed is a complex series of tank tests, usually never worthwhile for a pleasure boat where saving 5-10% on fuel is a minor detail and won't affect the sale. I don't think any tank testing went on for the Independent Shipwrights boat and thus doubt the bulb does anything significant. It used to be that bulbs were smaller and out of sight below waterline. On modern beamier boats bulbs have become far larger and often extend well above the at rest waterline, see the new Danish trawler (a real trawler) in the photo.

Some earlier writing on the subject.

Bulbous Bows

BirgitteMartine.jpg
 
Good grief. That bulb is huge.

It's interesting to see how much hull is below the waterline on a real offshore trawler. That boat looks like it draws 8-9' but looking at the markings on the bow maybe only 5-6'? Or am I looking at that wrong?
 
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cardude01 said:
Good grief. That bulb is huge.

It's interesting to see how much hull is below the waterline on a real offshore trawler. That boat looks like it draws 8-9' but looking at the markings on the bow maybe only 5-6'? Or am I looking at that wrong?
Click to expand...

Draft marks are in metres, bottom one is 2.6, upper one 4.4. The white painted line is right at 3 metres. The boat is approximately 55' long with a beam of 20'.
 
That Danish trawler is one oddly ugly boat.
I'd call that a bow goiter.
 
Looks like the trawl might have hung up.
 
Rebel112r said:
Looks like the trawl might have hung up.
Click to expand...

Either that or that is one hobby horse of a ride. It sure does not look like rough enough water to create that kind of bow rise!
 
manyboats said:
Just another "I wanna be like the big boys" feature.
It's like extended OB brackets ... better to just extend the whole boat.
Click to expand...


Have you ever been on a bulbous bow boat or run one for a time in various seas.

I disagree with your comments of keeping up with the big boys, the ones I have run have produced a softer ride with less hobby horsing than other designs with increased speeds from less power.

Just my 2cents worth based on personal experience
 
gwkiwi,
Yes they do dampen pitch but that costs dearly in the ability for a boat to rise up to a sea .... something I think is important for a small boat to do.

And part of the "all chain rode" is also a "big boys" thing.
Speaking of big boys your bow line looks thke those on a ship.
 
Tad Roberts said:
Draft marks are in metres, bottom one is 2.6, upper one 4.4. The white painted line is right at 3 metres. The boat is approximately 55' long with a beam of 20'.
Click to expand...

That's still too deep for most of the ICW.

9 feet draft is a bit deep for a 55, but a open ocean work boat probably makes it much more stable.
 
Hi, Stubones99-
I'd call that one a parrot bow, from the front it looks just like one.
The ships look pretty good, but wouldn't water (in bad weather and rough seas) splash right up that ramp and blast the pilothouse?
I bet they're fast.
 
 
Seems to me we really have no real information to draw any accurate conclusions on the merits of different bow shapes for our boats. Ours came with a bulb, but I doubt Selene would have been able to provide hard facts to convince me to spec it out that way.

PS - don't blame me for lack of maintenance :) The pic was taken during pre-purchase survey few years ago.
 

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No Mast,
What's that thing hang'in down under the bulb?
A fwd shooting sonar?

It would seem to me that if you .. no when you slam into big seas that thing will be subject to very high forces and must be quite heavy and strong to not get damaged. But assuming it does lower drag at some speed ... and you do go that speed the extra weight and cost may be worth it. Adding weight to a boat isn't often a win win.

Tom,
New, different and shocking applies to the political world as well. Not to mention the media. Both have run wild because of it.
 
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My guess is many bulbous bow might actually add buoyancy or are neutral.
 
haha yea its just a shadow
 
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