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Old 02-22-2013, 12:05 PM   #141
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I was (and still am actually) a member of the Albineers of BC Canada. Most all members had the little Albin 25 ... as we did. The Albin's crossection was roundish by most mariners definition and most everybody complained about the "snap roll". That was the only really bad thing about that otherwise wonderful boat but the roll was so quick and "snappy that's what they called it.

Art says "It's not wise to run a-beam to any type of sea that is bothersome for any reason in any style boat." I was inclined to say "DUH everyone knows that" but fishermen do it all the time bottom fishing and if your half smart you'll know that most any boat will assume a position parallel to the waves w no power on. And you're much more than half smart art.

BillMFI,
Cinnibuns for me too. But beam seas that will rock your boat uncomfortably are very common indeed.
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Old 02-22-2013, 12:43 PM   #142
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I was (and still am actually) a member of the Albineers of BC Canada. Most all members had the little Albin 25 ... as we did. The Albin's crossection was roundish by most mariners definition and most everybody complained about the "snap roll". That was the only really bad thing about that otherwise wonderful boat but the roll was so quick and "snappy that's what they called it.

Art says "It's not wise to run a-beam to any type of sea that is bothersome for any reason in any style boat." I was inclined to say "DUH everyone knows that" but fishermen do it all the time bottom fishing and if your half smart you'll know that most any boat will assume a position parallel to the waves w no power on. And you're much more than half smart art.
TY for such a high compliment Eric... please note that my operative term was 'run a-beam"; which connotes cruising a boat at some upper speed... not bottom fishing! lol
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Old 02-22-2013, 01:39 PM   #143
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My bad Art ... I spoze I better read more carefully before posting.

I have a problem w my i-pad as it continuously selects the words to post w/o my input it changes the words I type to what it thinks is most appropriate. And frequently it's not of course. It would help if I learned to type looking at the screen instead of the keyboard but my fingers don't do that very gracefully. I couldn't play the piano for this reason. So I usually read through and edit my own stuff before hitting the post bar. HaHa but sometimes I'm in a hurry.
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Old 02-22-2013, 01:40 PM   #144
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If you think tugs throw out a huge wake, you should try getting over the wake of a nuclear submarine scootin' right along on the surface. Most of the boat (yes, they are called "boats) is underwater, so the wake is quite large.
Leaving Norfolk we were waked pretty good by a sub. Susan chastised them on the radio until I reminded her that they had nuclear missiles. Chuck
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Old 07-26-2013, 01:43 PM   #145
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.....And I don't believe there is a rule that says displacement hulls have to have round bottoms and chines. I've posted these shots before, which I did not take, but it shows one of the sampans or aku boats that were built locally in Hawaii in the later 1940s and early 50s for the tuna (aku) fishery there. These relatively narrow boats incorporated flat albeit curved bottom sections, hard chines, and even gunwale " hull bulges" (my term) to provide roll stability in the often very rough waters these boats fished in, like the infamous Molokai Channel. The "hull bulge" is obvious in the second shot and was quite effective as these boats were often rolled to their gunwales in the windy swells and waves around the islands.

all the aku boats had the same basic lines above and below the waterline-- but whoever it was, he understood the nature of the open ocean the boats were going to work in and how to design a hull to effectively meet the challenge.
Interesting posting Marin. I'm going to have to look up some more info on these hull shapes if there is not more discussion of them as I read thru this tread.

Another item I see yet to be mentioned is bilge keels? Do they work to limit the rolling motion?
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Old 07-26-2013, 02:39 PM   #146
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I have about 5000 hard hours in full keel Shamrocks as an assistance tower...I have completely rebuilt them from the keel to the cabin top...they are submarines they are so wet (without a pilothouse/windshield wiper I almost refuse to run one) they can reach 30 knots but struggle even with a 454 in them, they stall pretty bad in sharp turns with a really nasty wall of water coming over the bow, pound badly in anything more than 2 feet above 16-18 knots...yet I can't think of a better swiss army knife for assistance towing work (for the bang for the buck of what they cost now)...but I would NEVER own one as a private boater...they can do everything asked OK but do nothing well (plus I have fished them for over 10 years on a regular basis so it's not all work)....
What would you think of slowing that Shamrock hull design down to something around displacement speed? It sure is nice looking.
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Old 07-26-2013, 03:01 PM   #147
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"The worst roll of all is in a wide and hard chine boat a-beam to a steep and short sea. Some call it a "snap roll". It's VERY annoying and even dangerous."

Nope,, the worst roll is in a catamaran with wider beam and higher flotation further outboard than even a chine boat.
That is a snap roll !
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Old 07-26-2013, 03:09 PM   #148
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What would you think of slowing that Shamrock hull design down to something around displacement speed? It sure is nice looking.
No as it is not a displacement speed hull and wouldn't get the job done at those speeds.

It's best feature is that it's a little good at everything ad really good at nothing...kinda like a Swiss Army knife. If you can only drive one (relatively inexpensive) boat for assistance towing or carry one tool in a survival situation......
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Old 07-26-2013, 04:23 PM   #149
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No as it is not a displacement speed hull and wouldn't get the job done at those speeds.
I'm having trouble defining exactly what the optimum 'displacement speed hull' is ??

As I looked thu that rather lengthy subject thread "Hull Shapes....show us your girls bottom", it appears to me that many different hull shapes can be operated reasonable well at displacement speeds. It's when they try to get above their displacement speed that they need a lot of tweeking.

I don't see where this general shape is that much different than the Grand Banks hulls, other than being a little flatter in the stern?
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Old 07-26-2013, 05:53 PM   #150
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Besides the FACT - - > That: Every individual configuration in a hull WILL make it react differently with water it travels through and the sea conditions it encounters while traveling or at stand still; as well as speeds it travels, weight on boat's superstructure as it gets buffeted by winds, and a myriad of other of the boat’s entire-design/natural-conditions/weight-load-area factors/pilot’s-capabilities!

Traveling along in most midsized pleasure cruisers at a bit below (4 to 5% below) mathematically calculated hull speed is usually just about the most fuel efficient rate of travel - IMHO

Every person who owns or often pilots a particular boat has learned (instinctually “knows”) what is correct speed for their boat (if they have more than one brain cell that is – lol). In addition there are many who are absolutely locked into belief that their D or SD/SP or P hull design are simply way above the other hull shapes... well, all I can say is each to their own!

Bottom line as I see it is if any one of us likes our boat and she handles well enough to please us – then we should be pretty darn happy! This is (trawler) pleasure cruising after all!!

PS: If the hull and boat do not please us then we should either not purchase that craft – or, if we already own it – as Barnacle Bill the Sailor might say – Dump the Bitch!
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Old 07-26-2013, 08:22 PM   #151
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I'm having trouble defining exactly what the optimum 'displacement speed hull' is ??

As I looked thu that rather lengthy subject thread "Hull Shapes....show us your girls bottom", it appears to me that many different hull shapes can be operated reasonable well at displacement speeds. It's when they try to get above their displacement speed that they need a lot of tweeking.

I don't see where this general shape is that much different than the Grand Banks hulls, other than being a little flatter in the stern?
sure...ANY hull can be operated reasonably efficient at displacement speed..but it's pretty hard to water ski there....

I run the shamrock as an assistance tower...people aren't going to wait for me to show up at "displacement speeds"....
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Old 07-26-2013, 08:41 PM   #152
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Here's what Ed Monk and some others have done to "soften" the roll reversal on a hard chine, semi planing hull. Theoretically also has the benefit of running on a narrower, lower drag hull when the boat begins to lift (I won't say plane) at higher speeds.

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Old 07-26-2013, 10:49 PM   #153
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Interesting posting Marin. I'm going to have to look up some more info on these hull shapes if there is not more discussion of them as I read thru this tread.

Another item I see yet to be mentioned is bilge keels? Do they work to limit the rolling motion?
Brian,
Our local waters are relatively unprotected and confused, and there is rarely less than 15-20 kts of wind. Typically about 6 ft of messy swell, so there aren't many recreational type trawlers. (only real ones) Deep vee hull Bertram 35's and the like are the most popular power boat for those who can afford the fuel.

I went for a full displacement hull which is shaped like a small Willard 40. Very efficient round stern, but the standard versions roll like a bitch in a beam sea. The manufacturer tried in minimise this on later models like mine by adding bilge keels, and from what I understand this helped a little. But still in a beam sea - its rock and roll time; soft and gentle but LOTS of movement. Hold onto your beer! I would say the motion is still very safe, but not at all comfortable.

Just before the company stopped production they released a few motor sailers. Once I raise my small sails (total 300 sq ft), its a totallly different story. Everyone aboard breathes a sigh of relief and you no longer have to wedge yourself in a corner.

Larger bilge keels may do more to slow the roll, (mine protrude anout 12" from the hull, and run about half the length of the WL), but in a bad sea and a very soft chine you need additional roll attenuation of some sort.

I went with the sails, rather than stabilizers/fish so I could add a knot or two rather than take one off, and have no regrets at all.
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Old 07-26-2013, 11:17 PM   #154
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Here's a pic showing the bilge keels.
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Old 07-26-2013, 11:24 PM   #155
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Here's what Ed Monk and some others have done to "soften" the roll reversal on a hard chine, semi planing hull. Theoretically also has the benefit of running on a narrower, lower drag hull when the boat begins to lift (I won't say plane) at higher speeds.

Attachment 21674
Skidgear

That photo's chine area looks very similar to some Monk designed Tollycraft that were produced only for a couple years. Being in the Tolly Club I can attest that most owners of that hull design seem not too happy with its lack of stability in seas when anchored and I've heard complaints about its beam sea actions at trawler speeds as well as unpleasant hard cornering at higher speeds. At least two I've seen picts of while refit was underway; they filled in that "inverted, cupped chine" and brought the chine back into standard Tollycraft design conditions. As you mentioned, Monk's intent was less friction due to less bottom surface when a Tolly was on full plane... Tolly’s such as these had WOT speeds of 21 to 25 knots with factory power. If repowered with real meat I read of one that reached into the high 30’s!

Like I said in post # 150: “Every individual configuration in a hull WILL make it react differently with water it travels through and the sea conditions it encounters while traveling or at stand still; as well as speeds it travels,...”

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Old 07-26-2013, 11:26 PM   #156
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....I went with the sails, rather than stabilizers/fish so I could add a knot or two rather than take one off, and have no regrets at all.
Yes I've been a sailor all my life, and I understand them. Those sails can make all the difference. ...and I've had a life-long interest in motorsailers.

What I'm trying to do right now is understand power boat hulls,...that I have very little experience with. And I don't pretrend to be interested in the go-fast and planning powerboats, that's a whole different ballgame. I'm interested in what makes the ideal DISPLACEMENT-SPEED powerboat hull. And at this particular time a displacement speed hull for coast-wise, inland waters, not offshore work.
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Old 07-26-2013, 11:43 PM   #157
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I'm having trouble defining exactly what the optimum 'displacement speed hull' is ??

I don't see where this general shape is that much different than the Grand Banks hulls, other than being a little flatter in the stern?

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sure...ANY hull can be operated reasonably efficient at displacement speed..but it's pretty hard to water ski there....

I run the shamrock as an assistance tower...people aren't going to wait for me to show up at "displacement speeds"....
So you agree with me that most any hull can be operated efficiently at displacement speeds. I was NOT asking about water skiing.

As far as the Shamrock hull shape is concerned I was suggesting that this hull shape might be expanded up to the ~40 foot size, and still be a reasonable hull configuration for a displacement operating trawler? Again I was not asking for a fast boat shape that your people are not wanting to wait for.
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Old 07-26-2013, 11:59 PM   #158
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Here's a pic showing the bilge keels.
AusCan

You’ve got a cool designed boat w/ nice looken bottom!

Bet she economically and smoothly slips through the water nice and quiet at hull speed while sitting fairly upright at anchor as wakes come broadside. Beam sea action should be dampened quite a bit by the side keels. Following sea would only be problematic if you've not enough power/speed to keep up with the waves and the rollers roll up on/against/under your stern... but, it also looks like she has a rounded soft stern to let the rollers slide underneath, if necessary. Hitting a head sea should be no problem as she has a fine flair at her prow and the superstructure looks to have ben planned to handle some rough encounters. Her general shape/design reminds me of some real nice New England coastal seagoing boats I became accustomed to in 1950’s - 70’s.

Am I reading your rather small photo correctly! It won’t punch up and enlarge for me... but I did blow it up another way, although it became blurry.
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Old 07-27-2013, 12:33 AM   #159
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Sorry Art. I don't have much for pics here on my work PC, but here's a slightly better one. The black hull still doesn't show the lines well in a photo, but she certainly is slippery.
It loves a following sea. I've surfed some big waves coming in to our marina, at she does it with style. No hint of broaching so far.

The bilge keels don't do as much as I expected to stop the rolling in a beam sea. She stays perpendicular to the water, but when the swell is big, that doesn't mean upright. When the seas get confused, with short messy swell, the sails become a necessity. It works well for the consistently windy local conditions.
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Old 07-27-2013, 01:13 AM   #160
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Sorry Art. I don't have much for pics here on my work PC, but here's a slightly better one. The black hull still doesn't show the lines well in a photo, but she certainly is slippery.
It loves a following sea. I've surfed some big waves coming in to our marina, at she does it with style. No hint of broaching so far.

The bilge keels don't do as much as I expected to stop the rolling in a beam sea. She stays perpendicular to the water, but when the swell is big, that doesn't mean upright. When the seas get confused, with short messy swell, the sails become a necessity. It works well for the consistently windy local conditions.
FUN BOAT!! Congrats! One of the nicest I've seen on TF...
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