Reply
 
Thread Tools Display Modes
 
Old 09-10-2010, 01:49 PM   #21
TF Site Team
 
Baker's Avatar
 
City: League City, Tx
Country: Texas
Vessel Model: Carver 356
Join Date: Oct 2007
Posts: 5,630
Mainship 34 models

Quote:
Marin wrote:

*

So flat or flat-ish bottom is not automatically*part of the definition of a semi-planing boat.

*


-- Edited by Marin on Thursday 9th of September 2010 07:23:06 PM
*

No it isn't...not at all. *BUT.....Semi planing to me(ignorant) is a hull that does not produce lift over ALL of its area(hence the term). *The front half does not produce any lift at all. *The aft half does. *Now to get the boat onto plane with some semblance of speed/efficiency, a lot of lift "lost" on the front half has to be regained in the aft lifting sections. *As you stated and as most of us know, the flatter it is, the more lift it provides. *And most semi planing hulls flatten out significantly aft whereas a modified V generates lift over the entire wetted area so they carry a lot of V all the way aft(deadrise). *Modern V hulls are more effiicent and more stable at higher speeds but they do tend to pound into the weather. *Whereas a semi planing hull sacrafices speed and efficiency but the do "slice thru the snot" better....as Albin Man put it. *Because of this, they also have a tendency to be wetter since they are going THROUGH the weather instead of over it.

EDIT:


But, now that I think about it(ignorantly), if you did carry a lot of deadrise in a Semi boat that instability we have been talking about would be greatly exaggerated. *In other words, I will go back and somewhat disagree with your above quoted statement. *Semi planing boats need to have "flat as a board" aft sections not only to increase lift/speed/efficiency, but also for stability purposes. *Too much V aft and the thing would just flop over to one side....not to mention the speed/efficiency that would be lost.

*




-- Edited by Baker on Friday 10th of September 2010 01:55:01 PM
__________________
Advertisement

Baker is offline   Reply With Quote
Old 09-10-2010, 03:03 PM   #22
Guru
 
Codger2's Avatar
 
City: San Diego
Country: US
Vessel Name: "Sandpiper"
Vessel Model: 2006 42' Ocean Alexander Sedan
Join Date: Oct 2007
Posts: 5,420
RE: Mainship 34 models

Quote:
Baker wrote:" Too much V aft and the thing would just flop over to one side....not to mention the speed/efficiency that would be lost."
Doesn't dihedral or anhedral have the same effect on an aircraft as deadrise has on a boat? The result being "Stability" in both cases?

*
__________________

Codger2 is offline   Reply With Quote
Old 09-10-2010, 04:12 PM   #23
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
RE: Mainship 34 models

Quote:
Baker wrote:Semi planing to me(ignorant) is a hull that does not produce lift over ALL of its area(hence the term).
Your definition is not the one I've read in articles by marine architects like Tom Fexas.* They use the term semi-planing to refer to a boat that is incapable of achieving a full plane unless almost unachievable amounts of power are available.

I've never seen these guys refer to a planing hull as being one that can develop lift, or significant lift, over the entire wetted surface.* In fact I've never seen any of the terms--- planing, semi-planing, semi-displacement, or displacement--- related to how much of the hull area produced lift (or didn't produce lift in the case of the displacement boat).**They are related to how much lift is generated, but not how much of the hull's area is generating that lift.* At least not the way I've seen it written about.

A semi-planing hull, by guys like Fexas' definition, is one that uses speed and hull shape to achieve a degree of hydrodynamic lift that will at least begin to lift the hull and reduce drag.

Fexas has designed some fully-planing hulls that, other than a much more raked-back stem, have bottom configurations exactly like commercial lobsterboats--- Vee in the front, flat in the back.* He's also designed fully-planing hulls that are deep-V in shape all the way back*(and have massive powerplants).


If you take the keel off a Grand Banks*hull you'll have*a halfway decent planing*hull if you put sufficient power in it.* I say halfway decent because even without the keel, it's not an efficient design for a fully-planing*hull.* But the keel and the*fairing into it*adds a massive amount of*drag, thus rendering* the hull*"semi-planing" because there's no way you'll get it*onto a full plane with the kind of power typically used in recreational boats.
Marin is offline   Reply With Quote
Old 09-10-2010, 04:15 PM   #24
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
RE: Mainship 34 models

Quote:
SeaHorse II wrote:


Baker wrote:" Too much V aft and the thing would just flop over to one side....not to mention the speed/efficiency that would be lost."
Doesn't dihedral or anhedral have the same effect on an aircraft as deadrise has on a boat? The result being "Stability" in both cases?

*

I would say yes.* If you look at the back end of some deep-V hulls they are almost as "veed" at the transom as they are*much farther forward.* This makes for a smoother ride, and yes, it would add stability, at least while underway.

*
Marin is offline   Reply With Quote
Old 09-10-2010, 04:28 PM   #25
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Mainship 34 models

Quote:
Baker wrote:

*Modern V hulls are more effiicent and more stable at higher speeds but they do tend to pound into the weather.
I'll give you the "stable" part but not the "efficient" part.** A V-hull is less efficient in terms of the amount of power*it takes to plane it than a flatter hull.* As I described earlier, this was a conscious compromise by Mr. Arima in the hull design of his very popular trailerable fishing boats, and is also apparent in the C-Dory.* In these two boats, it was all about efficiency and needing less power to plane (which kept purchase and operating costs down).* So Arima designed a hull specifically for PNW waters which can be rather choppy even on nice days due to tide rips and such, but also provided the ability to go fast with relatively little power.* The resulting hull has a very deep forefoot to deal with the chop and a very flat mid and afterbody to make it plane with little power.

A V-hull takes more power to plane because its hull shape is less efficient at producing hull-lifting hydrodynamic force (the force is angled in due to the angle of the bottom as opposed to straight up as is the case with a flat-bottom boat.)* So for a given speed*you need to generate more hydrodynamic pressure against the V-bottom for a boat of a given weight than you would with the same size and weight of boat with a flat bottom.* Which takes more power to do.

Not sure all that made sense but the bottom line is that a V-bottom is a less-efficient planing configuration than a flatter bottom but it gives a much easier ride.

*


-- Edited by Marin on Friday 10th of September 2010 04:30:56 PM
Marin is offline   Reply With Quote
Old 09-11-2010, 11:34 AM   #26
TF Site Team
 
Baker's Avatar
 
City: League City, Tx
Country: Texas
Vessel Model: Carver 356
Join Date: Oct 2007
Posts: 5,630
RE: Mainship 34 models

We are getting into semantics here Marin like we always do. The reason why your marine architects define it as a hull "that does not achieve full plane" is because they do no develop as much lift as a planing hull...simple as that. Now I stated the reason why they don't above. I am in full agreement with their definition...I just went a little further as to the "why" of it.

As far as dihedral goes and how it relates to this....well it doesn't really. There is alot more going on in an airplane(ie other lifting and stabilizing surfaces). I will go further to say that the entire hull of an airplane is immersed in the fluid and every single inch of it's surface has a dynamic effect on the whole operation. So it is a crude comparison and one I don't think really applies.

A V hull has dynamic pressure along the full length of the wetted area...IOW, lift is created basically along the full length of the hull. The forward part of a semi boat is basically a full displacement hullform. It does not create enough(if any) hydrodynamic pressure to provide stability. To counter that lack of stability forward, you need more aft. If you had too much deadrise aft, it would suffer stability issues. Trim tabs might help but I think you would need more than that....strakes and such.

Marin, my point about efficiency ref V hulls was one of comparison. A v-hull is more efficient than a semi hull. Everybody knows that a flatter hull is more efficient. Are you trying to tell me that Mr. Arima is hiding some magical semi planing hull design that he has never sprung on the marine world? I am thinking it is more a "negative economies of scale" thing...ie something you can get away with on a smaller hull that won't translate well into a larger one. There is nothing magical about your Arima hull....however sweet it may be.

The spectrum would be:

A flat bottom skiff on one end with a sailboat hullform on the other with a semi planing hullform right in between. Now you know as well as I do that we can build a boat anywhere along that spectrum. ANd as it relates to efficiency on plane, that flat bottom boat is the most efficient and they become less efficient as you go towards the sail boat....ON PLANE!

Gotta go....wife wants me off this thing and I don't blame her....beautiful, although hot, day down here in Tejas!!! Y'all have a great day.
Baker is offline   Reply With Quote
Old 09-12-2010, 01:17 PM   #27
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Mainship 34 models

Quote:
Baker wrote:

Are you trying to tell me that Mr. Arima is hiding some magical semi planing hull design that he has never sprung on the marine world?
An Arima is a fully planing hull, not a semi-planing hull.* What I'm saying is that the flatter the bottom of a fully-planing hull is, the more efficient it will be.* However the ride will suck as the water gets rougher.* It sounded like you were saying that a V-bottom on a planing boat is more efficient than a flat bottom on a planing boat.* It's the other way round.* What Arima did is create a boat that was, in his opinon, the optimum compromise for our local waters between very efficient planing and a halfway decent ride.* So his boats have a deep-V forefoot that rapidly flattens out as you go aft.* Nothing semi-planing about it.

Here's a not-so-great shot of Malolo on its trailer.* Nothing magic about it's design, it's just one of the more successful hull-shapes for this type of boat.* At cruise rpm (not full throttle) Malolo goes 30 mph with 90hp.* If the hull was a deeper V all the way back, like a Grady-White or something, the ride would be way nicer in choppy water but it would take a lot more power to achieve the same speed for the same size and weight of boat.



*


-- Edited by Marin on Sunday 12th of September 2010 01:24:41 PM
Attached Thumbnails
Click image for larger version

Name:	malolo.jpg
Views:	131
Size:	118.8 KB
ID:	2653  
Marin is offline   Reply With Quote
Old 12-18-2010, 04:35 PM   #28
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,701
RE: Mainship 34 models

About Baker's idea about lift here and no lift there * * ..any part of the hull that is acting on the water passing under it that is at some angle of attack is (would be) creating lift. But also any part of the hull that is decreasing in deadrise as the water goes aft will also produce lift.Consider the M 34. It's deadrise decreases constantly all the way to the transom. So the M34 would be creating lift over it's entire bottom when the keel is running level. Most or at least many boats have constant deadrise from amidships to the transom or from a point 1/4 of the way fwd back to the transom. Of course at mid planing speeds down to almost disp speeds there will be considerable angle of attack and lift will be over the entire hull in contact w the water. Of course any part of the hull not in the water will not be creating lift from the water. Many people think that a planing hull will have a nice soft ride if it has a nice pointy bow. Not so. Planing hulls ride on their bottoms * *..not their bows.*While quartering a following sea the aft corner of a hull like the M 34 sticks out to meet the wave and contacts it before it would if there was plenty of deadrise or if the boat was a double ender or even if it were flat. So the wave pushes the windward corner up prematurely and since there is little buoyancy to counter act that force, some aft but very very little fwd the boat rolls w it's lee rail down. If the boat is wide and full at the chines fwd (like a Uniflite, an Island Gypsy or a 43 Albin the boats rolling toward the trough is arrsted. If the seas contact the port stern corner first lots of port rudder will help roll the boat into the rushing sea and away from the trough.
Nomad Willy is online now   Reply With Quote
Old 04-10-2011, 11:54 PM   #29
Hospitality Officer
 
Andy G's Avatar
 
City: Pittwater
Country: Australia
Vessel Name: Sarawana
Vessel Model: IG 36 Quad Cabin
Join Date: Sep 2010
Posts: 1,557
RE: Mainship 34 models

I have been trying to follow this post, but with my limited grasp of the finer points that John,Eric & Marin decend/ascend to I a am a little lost.

As I just happen to have some shots of the underside of our IG36 I am putting them up as I am of a more visual than theoretical leaning.

To me the aft of the IG looks pretty flat once it is fared away(?) from the keel,she looks to me a little like the lobster boats photos.

Am I right in thinking that in a following sea then, and given the small rudder area, she is more susepetable to broaching than say a bilge keel configeration?
Attached Thumbnails
Click image for larger version

Name:	dsc_0929.jpg
Views:	139
Size:	97.3 KB
ID:	5647   Click image for larger version

Name:	dsc_0931.jpg
Views:	303
Size:	129.5 KB
ID:	5648   Click image for larger version

Name:	dsc_0932.jpg
Views:	129
Size:	109.8 KB
ID:	5649  
Andy G is online now   Reply With Quote
Old 04-14-2011, 06:38 PM   #30
Guru
 
Moonstruck's Avatar
 
City: Hailing Port: Charleston, SC
Country: USA
Vessel Name: Moonstruck
Vessel Model: Sabre 42 Hardtop Express
Join Date: Nov 2008
Posts: 7,847
RE: Mainship 34 models

I have owned and run planing boats with sharp entry and 12 degree deadrise aft, 24 degree deep V to the transom, and 16 degree deadrise to the transom.* They do not pound into a head sea.* The deeper the deadrise the more stable they are in a following sea.* Without dynamic lift from speed, they will roll almost like a round bottom.* At speed they have a tendency which increases with deadrise to lean into the wind.* That is why trim tabs are needed on a deep vee.* Tabs also help trim angle.* Too much bow down and the boat*gets squirlly.* In a big following sea take the tabs off to sink the stern down for stability.* The deeper the Vee the more power to keep it up on plane.

My Mainship 34 Pilot was good in a head sea.* Squirlly in a following sea, and wet until I added smart rails to deflect spray.* It was a full keel lobster styled hull that would cruise 17 knots with a 370 hp Yanmar.* All in all it was a good cruising boat.
Moonstruck is offline   Reply With Quote
Old 04-15-2011, 08:58 AM   #31
JD
Guru
 
JD's Avatar
 
City: New Bern NC
Country: USA
Vessel Name: Stella Di Mare
Vessel Model: Mainship 34t
Join Date: Apr 2010
Posts: 1,702
RE: Mainship 34 models

Quote:
Moonstruck wrote:*It was a full keel lobster styled hull that would cruise 17 knots with a 370 hp Yanmar.* All in all it was a good cruising boat.
*Do you have some specs as to your fuel burn at different speeds or RPM's?

Thanks

*
JD is offline   Reply With Quote
Old 04-15-2011, 09:24 AM   #32
Guru
 
Codger2's Avatar
 
City: San Diego
Country: US
Vessel Name: "Sandpiper"
Vessel Model: 2006 42' Ocean Alexander Sedan
Join Date: Oct 2007
Posts: 5,420
Mainship 34 models

Quote:
Moonstruck wrote
Quote:
My Mainship 34 Pilot was good in a head sea.* Squirlly in a following sea, and wet until I added smart rails to deflect spray.* It was a full keel lobster styled hull that would cruise 17 knots with a 370 hp Yanmar.* All in all it was a good cruising boat.
* * ** Having owned a Mainship Pilot 30, the 34 was at the top of my list when I decided I* needed a little more room. Being weak in character, I fell in love with the "Gourmet cruiser" at first sight and threw all my hard earned wisdom to the winds. Like a brazen hussy & a sailor on the beach, I picked her up and took her home. The Pilot 34, however, remains dear to my heart.

*

Pilot 34 (Not mine)


-- Edited by SeaHorse II on Sunday 17th of April 2011 09:36:22 AM
Attached Thumbnails
Click image for larger version

Name:	pilot 34.jpg
Views:	187
Size:	101.3 KB
ID:	5691  
Codger2 is offline   Reply With Quote
Old 04-17-2011, 08:57 AM   #33
Guru
 
Moonstruck's Avatar
 
City: Hailing Port: Charleston, SC
Country: USA
Vessel Name: Moonstruck
Vessel Model: Sabre 42 Hardtop Express
Join Date: Nov 2008
Posts: 7,847
RE: Mainship 34 models

Quote:
JD wrote:Moonstruck wrote:*It was a full keel lobster styled hull that would cruise 17 knots with a 370 hp Yanmar.* All in all it was a good cruising boat.
*Do you have some specs as to your fuel burn at different speeds or RPM's?

Thanks

*

*JD, the meaningful fuel burn spec to me is the average on a long cruise.* Counting all engine hours on a long cruise, she averaged 1.86 statute miles per gal.* The miles are in statute because the miles are in statute on the ICW.* That gave accurate mileage between fuel stops.

Walt, the picture of the pilot 34 you put up was made it front of the Fort in St. Augustine, FL harbor.* Mine was like it only an antique white topsides.* She was often mistaken for a Hinckley by some of the dockmasters.* Even the one at St. Augustine Municipal Marina asked if she was a Hinckley.* I miss the boat, but needed the size of the current one.

*
Moonstruck is offline   Reply With Quote
Old 04-18-2011, 05:11 PM   #34
JD
Guru
 
JD's Avatar
 
City: New Bern NC
Country: USA
Vessel Name: Stella Di Mare
Vessel Model: Mainship 34t
Join Date: Apr 2010
Posts: 1,702
RE: Mainship 34 models

Quote:
Moonstruck wrote:JD wrote:Moonstruck wrote:*It was a full keel lobster styled hull that would cruise 17 knots with a 370 hp Yanmar.* All in all it was a good cruising boat.
*Do you have some specs as to your fuel burn at different speeds or RPM's?

Thanks

*

*JD, the meaningful fuel burn spec to me is the average on a long cruise.* Counting all engine hours on a long cruise, she averaged 1.86 statute miles per gal.* The miles are in statute because the miles are in statute on the ICW.* That gave accurate mileage between fuel stops.

Walt, the picture of the pilot 34 you put up was made it front of the Fort in St. Augustine, FL harbor.* Mine was like it only an antique white topsides.* She was often mistaken for a Hinckley by some of the dockmasters.* Even the one at St. Augustine Municipal Marina asked if she was a Hinckley.* I miss the boat, but needed the size of the current one.

*

*Thanks Don.

*
JD is offline   Reply With Quote
Old 07-31-2011, 08:22 PM   #35
Guru
 
Moonstruck's Avatar
 
City: Hailing Port: Charleston, SC
Country: USA
Vessel Name: Moonstruck
Vessel Model: Sabre 42 Hardtop Express
Join Date: Nov 2008
Posts: 7,847
RE: Mainship 34 models

Here's my 2004 Pilot 34 Sedan.* I really enjoyed that boat.

*

*
Attached Thumbnails
Click image for larger version

Name:	caper at anchor (old moonstruck).jpg
Views:	149
Size:	27.5 KB
ID:	6843  
Moonstruck is offline   Reply With Quote
Old 07-31-2011, 11:11 PM   #36
Guru
 
Codger2's Avatar
 
City: San Diego
Country: US
Vessel Name: "Sandpiper"
Vessel Model: 2006 42' Ocean Alexander Sedan
Join Date: Oct 2007
Posts: 5,420
RE: Mainship 34 models

Don; I still love the Mainship 34 (as shown) & would highly recommend it to anyone.
Codger2 is offline   Reply With Quote
Old 08-01-2011, 04:50 AM   #37
TF Site Team
 
dwhatty's Avatar
 
City: Home Port: Buck's Harbor, Maine
Country: USA
Vessel Name: "Emily Anne"
Vessel Model: 2001 Island Gypsy 32 Europa (Hull #146)
Join Date: Sep 2008
Posts: 2,730
RE: Mainship 34 models

Quote:
SeaHorse II wrote:
Don; I still love the Mainship 34 (as shown) & would highly recommend it to anyone.
*Except for the color of that one, of course.
dwhatty is offline   Reply With Quote
Old 08-01-2011, 08:40 AM   #38
Guru
 
Moonstruck's Avatar
 
City: Hailing Port: Charleston, SC
Country: USA
Vessel Name: Moonstruck
Vessel Model: Sabre 42 Hardtop Express
Join Date: Nov 2008
Posts: 7,847
RE: Mainship 34 models

Quote:
dwhatty wrote:SeaHorse II wrote:
Don; I still love the Mainship 34 (as shown) & would highly recommend it to anyone.
*Except for the color of that one, of course.

*Someone needs to Photoshop David's boat to show him how a dark hull would improve on*its good*looks.
Moonstruck is offline   Reply With Quote
Old 08-01-2011, 04:10 PM   #39
JD
Guru
 
JD's Avatar
 
City: New Bern NC
Country: USA
Vessel Name: Stella Di Mare
Vessel Model: Mainship 34t
Join Date: Apr 2010
Posts: 1,702
RE: Mainship 34 models

Quote:
dwhatty wrote:SeaHorse II wrote:
Don; I still love the Mainship 34 (as shown) & would highly recommend it to anyone.
*Except for the color of that one, of course.

*Green might be better at that.
JD is offline   Reply With Quote
Old 08-11-2011, 03:08 PM   #40
Doc
Guru
 
Doc's Avatar
 
Join Date: Oct 2007
Posts: 508
RE: Mainship 34 models

I am beginning to consider a Pilot 34. How noisy are they up on plane?
__________________

Doc is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Mainship 40 and 43 moneyplays Marlow - Mainship 7 08-13-2017 04:30 PM
Mainship 36 Tony B Marlow - Mainship 30 09-27-2016 07:59 PM
Mainship shuts down yachtbrokerguy Marlow - Mainship 9 02-16-2012 02:38 AM
Why a Mainship? Liquid Living Marlow - Mainship 8 01-25-2011 10:04 AM
Mainship 390 Robkann Marlow - Mainship 17 09-21-2010 07:44 AM




All times are GMT -5. The time now is 11:14 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012