Hull Shapes----Show us your girl's bottom

Yes it has a Selene with a very high angle that caused the lift and block guy a bit of confusion when I made him block the front end a foot higher than the stern.

Dave

Fatty

motor banca

Our motor Banca in the Philippines. 53' and has a automotive transmission. Clutch and four forward gears. Reverse is about useless, makes lots of noise but takes forever to stop using reverse.

Recently hauled our boat for bottom paint and through-hull maintenance.

Shiny props, Ray. Looking good. ... Saw the Mahalo Moi resting comfortably in the Vallejo Marina today. Is the canvas covering the stern new?

No. Same vintage as the rest.

Going back into the water today

freshalaska,
It appears the Joy of Life has amas. What is her displacement and power. Hull speed must be really mov'in along.

When I see this thread w a new post I'm always eager to see what's new.
Fryedaze, I can see a twist in your stern bottom and know Giggitoni has even more. From the side your boat has that just right look about it that is frequently the mark of a classic. VERY nice looking boat.

Our

girl bottom

Is it

Boatgm said:

Fatty

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the photo of your last boat ?
Or your trimaran lost one arm ?

longcours62 said:

the photo of your last boat ?
Or your trimaran lost one arm ?

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Just had one off. They are just pinned and lashed on.

First

Boatgm said:

Just had one off. They are just pinned and lashed on.

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i am thinking your prao is already finish.

longcours62 said:

i am thinking your prao is already finish.

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No I am not that fast and have a big tri in the works so the single out rigger boat may have to wait till you get out to Asia

New to the forum and I like this thread so here are a couple of photo's of our 46 Nordhavn's bottom. The black paint makes it a little hard to see but it's similar to the Willard posted earlier. Smooth and round.

We've been cruising for 5 years now, started in Anacortes WA, went to SE Alaska twice and have been in Mexico for 3 years.

Frank
MV Discovery
M/V Discovery Blog

I enjoyed reading your blog, Frank. I found your itinerary interesting regarding the transit distances and times. Those are useful for planning for our future coastal trip from San Francisco to Southern California. Welcome to the forum.

I frequently think of the Willard 30 as a shrunk down Nordy 46. Good for me as the Nordy is my favorite boat but it's out of my price range.

I like your boot stripe a lot. Nice way to dress up a black boat. Earth is a bit vague for a home port but I get the message.

I wonder about the black bottom paint. A fisherman locally says the black antifoul has much better antifouling properties. I've never heard of such a thing. I've always been a traditional red bottom guy but I thought color was just color. Could there be any truth to that?

Strange that you would have a 4 blade propeller w only 101 hp. Looks like a high blade area too.

manyboats said:

I wonder about the black bottom paint. A fisherman locally says the black antifoul has much better antifouling properties. I've never heard of such a thing. I've always been a traditional red bottom guy but I thought color was just color. Could there be any truth to that?

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The fact a fisherman told you this should make you suspicious right away.

My guess is no, black is not more effective than some other color. While we have always put black bottom paint on our boat this is because it's the "correct" bottom paint color for our vintage of GB (along with the red boot stripe), not because black is better. When we bought the boat out of Alameda, the bottom paint was blue.

From what I see in the big yard in our marina, the most popular bottom paint color on recreational boats, power and sail, is blue. Just about every new GB has blue bottom paint with a darker blue or sometimes green boot stripe. I see very few recreational boats in the yard with red (rust red) bottom paint anymore. But a lot of the commercial fishing boats use red.

We've never had the yards where we've had our boat painted tell us that black is more effective. It's just "what color do you want us to use?"

Now if you could keep your whole boat in the dark that would do a lot to reduce bottom growth because the algae and "moss" and whatnot need light to grow. But that's usually not practical. But black bottom paint is not the same thing as no light so my guess is that no matter what color paint you use, the end result in terms of resistance to bottom growth will be the same.

manyboats said:

Strange that you would have a 4 blade propeller w only 101 hp. Looks like a high blade area too.

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manyboats,
We have a Deere 6068DFM main rated at 130 hp with a 30” x 21” LH prop. We normally run at 1600 rpm doing 6.5 kts burning 2.0 gph.

We have the first 46 to have a non-Lugger main engine and with over 6K hours on it it runs like a clock and burns no oil. The longest nonstop run we've done is 7 days and it never missed a beat. I love my Deere.

Marin said:

I see very few recreational boats in the yard with red (rust red) bottom paint anymore.

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Regardless, a red bottom goes well with a yellow stripe and green hull. ... But black would go well with a white boat.

manyboats said:

Strange that you would have a 4 blade propeller w only 101 hp. Looks like a high blade area too.

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If so, stranger yet is the Coot's 4-blade propeller with only an 80 h.p. JD 4045D. I suppose it's because the Coot was designed to go slow.

fosborne said:

We have the first 46 to have a non-Lugger main engine

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Of course many if not all of Lugger's prime movers are based on Deere engines.

Re the black anti-foul .....good, I kinda thought that was so.

Re the propellers usually a larger area blade or more blades are used to absorb more power and to optimize blade loading within the space the boat has to offer. A higher aspect ratio 3 blade should be a tad more efficient than fosborne's wide 4 blade but his prop looks like about the best possible for smoothness.
I have room for a much larger dia prop on the Willard but for some reason an 18" prop is what Willard provided. I'd like to change to a 3-1 gear and run a 20" (or so) prop but not worth changing......probably. Or w a 3.5-1 gear perhaps even a larger prop. But the efficiency drops off faster w bigger slower turning props as you reduce speed even though at full speed/load the larger prop excels we all run well down the curve where a smaller prop may be just as efficient.

Marin,
I'm quite sure the smallest Deere is a Toyota.

Mark wrote:
"I suppose it's because the Coot was designed to go slow."
Probably it's because of the limited vertical space available. Also a 3 blade prop on the Coot would bring the blades closer to the bottom of the boat and cause more hydrodynamic vibration on the thin steel bottom. All is not always as it appears.

We've been told by prop shops and others in the business that the fewer blades a propeller has the more efficient it will be. The more blades a propeller has the smoother it will run.

Also the fewer blades a prop has the better it will back (meaning less propwalk).

In the case of high-horsepower, faster boats I believe there can be times when more blades are needed to get the best use of the power. Carey's lobsterboat, for example, seems to do better with a five-bladed prop than with the boat's original four-bladed prop.

manyboats said:

Marin,
I'm quite sure the smallest Deere is a Toyota.

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It may well be. Our good friend, recently retired as the head of the engineering department since the day the company started as Alaska Diesel Electric, made frequent business trips to suppliers in Japan and Germany as well as the US. He told me that the Lugger that is most used to repower boats like ours--- a 150 hp NA diesel---- is based on a Deere engine as are a number of their other prime movers. But they use Japanese base engines for some of their generators so it stands to reason that they might use them for their smaller prime movers, too.

manyboats said:

Re the black anti-foul .....good, I kinda thought that was so.

Re the propellers usually a larger area blade or more blades are used to absorb more power and to optimize blade loading within the space the boat has to offer. A higher aspect ratio 3 blade should be a tad more efficient than fosborne's wide 4 blade but his prop looks like about the best possible for smoothness.
I have room for a much larger dia prop on the Willard but for some reason an 18" prop is what Willard provided. I'd like to change to a 3-1 gear and run a 20" (or so) prop but not worth changing......probably. Or w a 3.5-1 gear perhaps even a larger prop. But the efficiency drops off faster w bigger slower turning props as you reduce speed even though at full speed/load the larger prop excels we all run well down the curve where a smaller prop may be just as efficient.

Marin,
I'm quite sure the smallest Deere is a Toyota.

Mark wrote:
"I suppose it's because the Coot was designed to go slow."
Probably it's because of the limited vertical space available. Also a 3 blade prop on the Coot would bring the blades closer to the bottom of the boat and cause more hydrodynamic vibration on the thin steel bottom. All is not always as it appears.

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3 over 4 more efficient as you approach top end... because many of us run at way less than top rpm...the four bladed is considered more efficient at cruise rpm because it is SO slow.

psneeld said:

3 over 4 more efficient as you approach top end... because many of us run at way less than top rpm...the four bladed is considered more efficient at cruise rpm because it is SO slow.

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I dunno about that. Older GBs like ours with low-power Lehmans in them came from the factory with three-bladed props. When we thought we had to replace our props the shops we talked to all recommended we go back to three blades as they said they would be enough more efficient to be worth going back to as long as we didn't have a vibration problem (which we didn't). Our engineer friend from Northern Lights/Lugger told us the same thing.

So we decided to change back to three-bladed props specced the same as the ones that American Marine installed on the boat when they made it. But when the prop shop said our four-bladed props were fine physically, they were just horribly set up, we decided to save a ton of money had have them rework what we had rather than buy new props.

Marin said:

I dunno about that. Older GBs like ours with low-power Lehmans in them came from the factory with three-bladed props. When we thought we had to replace our props the shops we talked to all recommended we go back to three blades as they said they would be enough more efficient to be worth going back to as long as we didn't have a vibration problem (which we didn't). Our engineer friend from Northern Lights/Lugger told us the same thing.

So we decided to change back to three-bladed props specced the same as the ones that American Marine installed on the boat when they made it. But when the prop shop said our four-bladed props were fine physically, they were just horribly set up, we decided to save a ton of money had have them rework what we had rather than buy new props.

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Just going on 45 years learning about props..on boats, helos, planes, wind generators....

Three blades are cheaper...that's why manufacturers put them on stock boats AND because they think you will be running the boat near top RPM....Many of us trawler guys stay in the torque peak for fuel economy...not the upper RPM range. Michigan props I think say the same...here is what they say about one of their 5 blade designs...

Many operators are selecting the HyTorq MY-T5 for new construction, repowering, and propeller upgrading. The main reason is to employ more blade area without having to increase propeller diameter, which may not be possible due to clearance or tip speed considerations. Another common reason is to improve propeller performance in installations where heavy vee struts, dead wood, or other hull appendages are agitating the water flow to the propeller.

Not arguing that higher aspect is more efficient...it is...IN THE PERFECT WORLD....

Well, you'll have to argue that one with the prop shop, who's been doing props for everything from little toy boats like ours up to commercial ocean tugs since 1947.

Every boat configuration is different and operating rpm and boat speeds are different so there is certainly no one-size-fits-all solution. But for our boat, with the hull configuration it has and the power it has and the cruise speed it has, if efficiency is the primary consideration, three blades are better than four given the same diameter, at least so say the people whose living depends on their knowing what they're talking about.

For Carey's boat, an entirely different machine than ours, it turned out that five blades are better than four, at least for performance. I don't know about efficiency.

The absolute, most efficient prop according to the pros, is one blade. But it would be a bitch to balance.

Just add another 3 feet to the shaft

Normaly four bladed are little more effective than three bladed as you can read on this sample :http://a31.idata.over-blog.com/4/56/46/39/Passagemaker/calcul-helices.JPG
made by Volvo the four bladed even with one inch less in pitch give 6,4 % more in kgs for the same diameter of 27"
And some builder don't like or even refuse to fit one four cylinder engines with four bladed propeller for some potential "resonance" problems between them.