SailNet Community - Reply to Topic
Thread: Production Boats and the Limits Reply to Thread
Title:
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :
Post Icons
You may choose an icon for your message from the following list:
 

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



  Additional Options
Miscellaneous Options

Click here to view the posting rules you are bound to when clicking the
'Submit Reply' button below


  Topic Review (Newest First)
12 Minutes Ago 09:25 PM
Capt Len
Re: Production Boats and the Limits

Bob, sorry if I wasn't detailed enough in my calculations regarding placement of my galley sink relative to the precise length of my shaft and whether I offset it to allow for prop walk . My comments were meant to be chatty and pertaining to my vessel specifically ,which is as it is. I personally designed and built and modified the shape and size of my stuff .My comments were based on my personal take on what works for me and how little modifications affected operational handling of my vessel. This is not theorizing in the real world This IS the real world.
1 Hour Ago 08:04 PM
Classic30
Re: Production Boats and the Limits

Quote:
Originally Posted by bobperry View Post
The fact is that once you get done theorizing in the real world the choice of where the prop goes in relation to the rudder is pretty much laid out for you given the other design features aft and where the engine is located which is a function of interior layout. Talk without including all those variables is just talk.
Actually, Bob, by using a modern hybrid drive (electric motor, controller and generator) designers like yourself have an enormous amount of flexibility with these variables. Being able to stick the maintenance-free shoe-box sized motor down in the bilge with a straight run to the prop and the engine/generator where you can actually get at it (not just in line with the prop) makes life a heck of a lot easier than it used to be..
3 Hours Ago 06:20 PM
bobperry
Re: Production Boats and the Limits

Len:
Everything is relative! Einstein taught us that. Weren't you listening?

How about some definitive numbers that can reduce the amount of guessing going on here and distill this discussion down to a level of good old objective science? You guys can spout your theories all day long with zero accountability, just friendly chat. That's fine. I have no problem with it. But what I think gets built and can cost more than $2,000,000. I can't guess. I have to measur, quantify and evaluate all the variables the best I can so I am not guessing. As you brought up, the prop is a huge variable as is the rudder, the skeg, the aperture, the hull and the keel. I will continue to go with what I know.

The fact is that once you get done theorizing in the real world the choice of where the prop goes in relation to the rudder is pretty much laid out for you given the other design features aft and where the engine is located which is a function of interior layout. Talk without including all those variables is just talk.
5 Hours Ago 03:58 PM
Jeff_H
Re: Production Boats and the Limits

I have a bunch of questions directed at me that I have not answered.

Starting with Outbound's question about my sail cloth, it is panel constructed Aramid with sheet polyester skins (Mylar), stick on sun screens, and lots of sacrificial wear patches.


Quote:
Originally Posted by davidpm View Post
Wow those boats are considered racer, cruser?

That big destroyer wheel and open back makes me immediately think racer.
Do people really live on a boat like that for an extended amount of time and cruse. I'll have to check into that. I love the idea of making good time especially to weather.

Is the Farr 395 in the same class?

Any other older boats that approach the ideal? I thinking closer to 100+ rather than 300-400+
To begin with, (working backward) I do not consider the Farr 395 in the same class as the Aerodyne 38. I have not sailed the 395 in dicey conditions, but I understand that they have a pretty poor motion. I had a chance to discuss this with someone who had sailed both boats, and he considered the Farr 395 to be more reliably faster than the Aerodyne 38, but thought that the Aerodyne was definitely better built and a much nicer boat for offshore use. He commented negatively on the motion of the 395 in certain conditions, but said that the Aerodyne had a much nicer motion.

I understand why you might look at a boat like the Aerodyne and ask the questions that you did. To some extent, the answer your question, "Do people really live on a boat like that for an extended amount of time and cruise? is "yes" but with some qualifications. Questions like these lie in the eyes of the beholder and while there are people who would cruise and live on a boat like this, not everyone would. Whether this is the right boat for you lies in your own personal philosophy on sailing, cruising and performance.

There is no doubt that cruising on boats like these take a different mindset than someone choosing to cruise a more conservative design. It takes making performance a priority that overrides the need for 'all of the comforts of home'. While these boats are not exactly Spartan (look at a 1960's era similar displacement boat if you want to see Spartan), they do require a certain discipline that would not necessarily be demanded by a more cruising oriented design.

There is a financial commitment as well as these boats cost more to buy (for a given displacement or volume) and potentially can cost more to maintain than similar displacement boats lower performance designs. That said, they tend to be a bargain compared to similar vintage, similar displacement blue-water oriented cruisers.

And while the Aerodyne 43 would be a boat that I personally would love to own and distance cruise (with the 38 being okay as well) frankly, in stock form these are not particularly set up to be cruisers. I personally would want to modify the boat to be a better cruiser.

Personally, I do not consider any retracting bowsprit to be suitable for offshore use. No matter how well conceived, when things get really bad they will leak, and that is not acceptable. I would probably add a fixed prod with proper anchor handling gear. I would also add a windlass in the so-called anchor well, and install better cleats, chocks, etc.

I would probably construct a light weight, and removable locker that would close off the transom, and provide storage for line, fenders, and fuel storage. It would not extend fully to the cockpit sole so large amounts of water could run out, but would have a hinged flap to minimize water coming into the cockpit from an overtaking wave.

The large destroyer wheel is a topic for another post, but that, or tiller steering, is actually an ideal solution for offshore sailing since it allows a very low friction steering system, which in turn is less wearing on the crew, and on self-steering devices, and which allows you to move around the cockpit to see, stay dry or make adjustments. I'll discuss that further later.

There are similar things that I would do to make the cabin more useful, but I think you should get the general thrust of my comments. I would also note that some of the boats that I listed earlier are 'no compromise' cruisers (the X boat and Halberg for example) while others are much closer to being full blown racers.

Jeff
8 Hours Ago 01:18 PM
Capt Len
Re: Production Boats and the Limits

Close to rudder is relative. When I changed to a Max prop I had to cut an arc out of the leading edge of the rudder to allow for the fatter blades.Rudder was balanced some 8% leading the pivot .Even cutting out a little sliver made a huge difference (negative) on ease of steering when using the prop wash to kick the stern about.
8 Hours Ago 01:09 PM
JonEisberg
Re: Production Boats and the Limits

Quote:
Originally Posted by bobperry View Post
But Jon, you have no idea how that particular boat would have behaved if the prop had been farther away. All you can do is speculate. Of course I recognize you have a lot of experience to speculate with. But so do I.
I suppose you're right, I'm just guessing....

But my initial guess would be, that in order to get some water flowing past that rudder from a dead stop, I might have had to apply a hell of a lot more throttle to a prop placed further forward...

;-)
8 Hours Ago 01:07 PM
Capt Len
Re: Production Boats and the Limits

An afternoon hanging around any dock will tell you of the handling skills of the modern sailor. Entertainment. using prop wash off the rudder means you don't need the bow thruster .If there's wind, prop walk only makes it a bit easier one way over the other. Skilled bursts of wash .Thane could go around and around slow inside a 55 ' circle just left in foreward at idle ,turn a 180 in her length at full sp and power and move sideways into a slip with a few back and fill. Only 22 tons but I knew where the pivot point was . Seems most now just get a stern line ashore and hope some one will pull on it.
8 Hours Ago 12:55 PM
bobperry
Re: Production Boats and the Limits

But Jon, you have no idea how that particular boat would have behaved if the prop had been farther away. All you can do is speculate. Of course I recognize you have a lot of experience to speculate with. But so do I.

I do not believe in generalizing on these things. It's just silly. I treat each boat as an individual.
For instance, what is "father away"? How are you measuring that? As a percentage of DWL? Or are you even measuring it at all? We are swimming, some are dog paddling, is a sea of undefined variables here. Does not work for me.
8 Hours Ago 12:48 PM
JonEisberg
Re: Production Boats and the Limits

Quote:
Originally Posted by Jeff_H View Post
With all due respect, I think that is a bit of an oversimplification. I think that Bob makes a good case that with a properly shaped rudder and a familiarity with not having propwalk, then maneuverability should not be an issue. And I will defer to Paulo's point that the choice of propeller influences propwalk as much than having a saildrive.

But I am less comfortable with the idea that separating the prop from the rudder is a good thing in low speed maneuvers. It is still very helpful in turning the boat to be able to send a blast of propwash over the rudder and spin the stern. I have come think that the current trend towards installing bow thrusters on ever smaller boats, is in part a response to the wider spread use of saildrives, along with the philosophy of making things easy for someone who has not learned the techniques and who is not willing to expend the energy to do things the more traditional ways.

Jeff
As usual, I completely agree... But all I'm ever good for might be an 'anecdote' as to what works best FOR ME, so I'll offer my latest example... :-)

Just returned from running a Freedom 45 out to Vermillion, Ohio (what a beautiful spot, btw) and as a result much of last week was spent on the Erie Canal... I love that trip, but it's definitely far better done on a stinkpot, without that irreplaceable bit of carbon fiber dangling off each end... That can make for a bit of 'delicate' maneuvering from time to timed during the course of transiting 36 locks, or docking in some funky spots unaccustomed to dealing with boats of this size... ;-)





Running the Barge Canal is not especially difficult, but the occasional tricky situation can be magnified a bit when doing it alone, and with a deck somewhat littled with parts of the rig ;-) But the only thing that can make it a bit dicey when singlehanded, is WIND... And while I was blessed with a week of beautiful weather last week, seeming more like September than July in upstate NY, I did have to contend with a good amount of breeze... by every afternoon, it would be honking out of the west, and my crossing of Oneida Lake was about as sporty as you'll likely ever see...

One can often find a surprising amount of swirling wind effect when entering an empty lock chanber, often exacerbated by side currents from dams adjacent to the lock, all while entering the chamber at a snail's pace... You definitely want a boat responsive to the helm, especially one without a bow thruster... But the real challenge during windy conditions when the lock is filled, and the boat is fully exposed to the effects of the breeze...

So, all I can say is, when it came time to jump back aboard this boat with relatively high freeboard and a fair amount of windage, and maneuver that beautifully Awlgripped hull out from between the confines of those steel and concrete lock walls, with a good breeze swilrling about, no assistance from a bow thruster, from a dead stop, well.... I was damn thankful the prop on that boat was closer to the rudder, as opposed to being further away... I rarely had the Time, or the Room, to wait for the boat to get some way on before getting some water flowing over the rudder, and thus gaining some directional control as a result...

;-))








9 Hours Ago 11:58 AM
Jeff_H
Re: Production Boats and the Limits

Quote:
Originally Posted by Jaramaz View Post
Hm, this was interesting ...

from saildrive to prop walk to rudders. Dependences everywhere!

So we agree now that saildrive and prop walk are rather independent? With the rather free position of the prop in a saildrive then that should give minimum propwalk. The rest is up to the prop itself and such.

Good, then we move on to if prop walk is a good quality or not. Clearly, prop walk decreases efficiency, moving some of the engine power off course instead of directly on course. From that perspective, prop walk is not a good quality.
Is prop walk good when manoeuvring in tight quarters? May be so, sometimes. Can also cause some issues now and then - OK, to that some always says: never happens me. However, when studying how most boats move around in a harbour - for most prop walk is not good.

Rudder function should be separated from the prop. That is obvious. A carefully designed rudder, correctly placed - it is possible to fully control the boat. If not, it is not correctly designed. (Yes, I have also been sailing on these nice long keeled things with the rudder attached at the end. That is a good example of "design by tradition". ).

The arguments that it is good with a dependence rudder - prop just stems from badly functioning rudders (as the long keeled things).

/J
With all due respect, I think that is a bit of an oversimplification. I think that Bob makes a good case that with a properly shaped rudder and a familiarity with not having propwalk, then maneuverability should not be an issue. And I will defer to Paulo's point that the choice of propeller influences propwalk as much than having a saildrive.

But I am less comfortable with the idea that separating the prop from the rudder is a good thing in low speed maneuvers. It is still very helpful in turning the boat to be able to send a blast of propwash over the rudder and spin the stern. I have come think that the current trend towards installing bow thrusters on ever smaller boats, is in part a response to the wider spread use of saildrives, along with the philosophy of making things easy for someone who has not learned the techniques and who is not willing to expend the energy to do things the more traditional ways.

Jeff
This thread has more than 10 replies. Click here to review the whole thread.

Posting Rules  
You may post new threads
You may 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 On

 
For the best viewing experience please update your browser to Google Chrome