It is currently October 31st, 2020, 6:11 am

All times are UTC - 5 hours




Post new topic Reply to topic  [ 92 posts ]  Go to page Previous  1 ... 3, 4, 5, 6, 7  Next
Author Message
 Post subject:
PostPosted: January 25th, 2008, 11:22 am 
Offline

Joined: September 28th, 2004, 6:52 am
Posts: 442
The design waterline is exactly that. It is the basis from which the designer calculates the performance, stability, course stability etc. etc.

The designer knows that the boat will float on that waterline for only milliseconds during its life but he also knows that what the boat will do when it is paddled off trim because he can, using is handy dandy computer, calculate how the boat will handle in any trim. Because of my sailboat background I also calculate how the boat will handle when heeled. Forceof habit I guess.

After you have done this kind of thing a bit you learn that a boat that performs well (or at least as expected) when trimmed to the designed waterline will also perform well within the typical range of trims and conditions. Very few boats are shaped such that they become waterpigs when out of trim a bit. If you have read your Joseph Conrad you will have read some comments by him about how some ships sailed better bow down and some stern down. This still happens. Designers make mistakes. Of course, everyone here knows that symmetrical boats only float on a symmetrical waterline for milliseconds at a time and the whole idea of a symmetrical boat is specious at best. Symmetrical boats have asymmetrical shapes in the water. The difference between them and asymmetrical boats is that the asymmetrical boat was designed that way.

Another common thought is that designers create boats from whole fabric. Nonsense. We all build on the backs of others. Interestingly I have proven that a person who has never paddled a boat can design a perfectly reasonable boat using a computer and just six points in 3D space. Not perfect boats but boats that some one somewhere will like or maybe even love. What teh designer tries to do is design the best possible boat for a specific market. You can do that through trial and error or you can do it using the accumulated knowledge of thousands of years. Both work - sometimes

What experts say about boats is not as important as what you feel about a boat. Interesting and useful, maybe, but gospel, no. Some boats do handle better trimmed down by the stern. Particularly boats built symmetrically fore and aft. Interestingly such boats trim down by the stern naturally since the stern paddler sits further from the center than the bow paddler and often weighs more. If a person were desiging a boat to be built symmetrically he would calculate the centers of gravity and adjust the trim for his calculations to suit. In short, he would design an asymetrical boat that was built symmetrically about its center. Sounds illy? Not at all. that is the way the boats turn out whether the builder/designer wanted it or not. Solo boats are a different kettle of fish. They float (more or less) as designed.

So, Yes, there is a designed waterline and, yes, it is important to know what it is and, yes, it is useful to the designer. It is commonly said that since a boat operates in a dynamic environment that all bets are off. Quite the contrary. designers learn from experience (hopefully) as well as analysis what characteristics work well over a wide range of conditions. When they learn or observe something they try to understand it better. This is the analysis part. For example, some boats seemed to handle waves better than others and pitch less. People had lots of theories but no hard data. Analysis revealed that the boats that handled best had the center of flotation aft of the center of buoyancy. This offset dampened pitching which had a positive effect. The offset between the two centers is calculated on the design waterline. Why? because you can't easily do much calculating on a moving target. You can, however, work from a fixed point.

Oh Yes, Graybeard, I did not mean to suggest that you're comments were negative. I was referring to the tendency of paddlers to assume that there is something magic in how boats perform and that it is something we mere mortals will never figure out but some reformed house builder from New Brunswick can figure out just by looking at the boat. :D

_________________
Cheers,

John Winters


Top
 Profile  
 
 Post subject:
PostPosted: January 25th, 2008, 2:04 pm 
Offline
User avatar

Joined: July 18th, 2007, 10:25 pm
Posts: 89
Location: Vermont
JW; :clap:

Thank you for your very generous, helpful, knowledgeable, and experienced overview of the working relationship between a good designer's efforts and the performance of the designed boat. Am I correct in guessing that when a paddler trims a boat a bit heavy in the stern it will most likely still be within the range of conditions that the designer anticipated but closer to one edge of that range?

I have to add that I was particularly tickled by your comment that "Solo boats are a different kettle of fish." I will now be able to tell my wife that I have it on good authority that when she says there's something "fishy" about by my preoccupation with "that tub," she's wrong. It's not a tub, it's a kettle.

b

_________________
There's only one world out there; we'd do well to take good care of it.


Top
 Profile  
 
 Post subject:
PostPosted: January 25th, 2008, 6:04 pm 
Offline

Joined: September 28th, 2004, 6:52 am
Posts: 442
Graybeard wrote:

Quote:
Am I correct in guessing that when a paddler trims a boat a bit heavy in the stern it will most likely still be within the range of conditions that the designer anticipated but closer to one edge of that range?


Dead on. Keep in mind that people are not very good at quantifying perceptions anyway,

Research in what is called perceived exertion (I was surprised to find out that people actually research such stuff) by some reveals that +/- 10% 50% of the time is pretty good and is often called the "just noticeable difference". Tank testing shwed my crude old performance prediction program KAPER was much better than that.

I know some people claim to be better and they may be but I would sure like to see the documented proof. Test tanks with all the expensive testing equipment used to be happy with +/- 5%. I think they expect better now but I haven't kept pace with tank developments.

Tell your wife it's better to smell something fishy than Chanel #5 on your shirt. :D

_________________
Cheers,

John Winters


Top
 Profile  
 
 Post subject:
PostPosted: January 25th, 2008, 6:21 pm 
Offline
User avatar

Joined: January 29th, 2007, 10:19 am
Posts: 2461
Location: Just outside the Blue Line
Graybeard wrote:
BK:

... it doesn't explain why the design is presented to the public either by the designer or the builder as having certain characteristics when experienced paddlers trim the boat in a manner that changes those characteristics. The simplest and most readily visualized characteristic is rocker.

Yet isn't that misleading if the analysis is based on the designed lwl and the feedback from paddlers is based on performance when trimmed by the stern?

Perhaps the growing number of asymmetrical designs is simply a reflection of designers observing that their boats function best at a trim other than they intended. It raises the possibility that an "all new asymmetrical design" might be nothing other than a successful old design with a neat pin-stripe indicating a lwl when loaded a bit aft. :-?


GB,

I'm not quite sure if I agree or disagree.

As far as canoes go, I don't really think any actual design is presented to the public. In fact, although it is highly unusual in the boat world to sell a product without giving at least a lines drawing, I have never seen anything like a lines drawing given for any commercially available canoe. Carrying Place Canoes in Ontario gives lines drawings for his canoes, most every one else leaves the actual hull shape as a bit of a mystery to the end user.

As far as rocker is concerned, I personally feel it is one of the least easily visualized parts of the design specs. Just where does it begin and end? Is it all in the ends or does it originate from amidships? Only a lines drawing can give this answer.

The best manufacturers today give length, beam, rocker fore and aft and displacement at various waterlines, but little info about what those waterlines actually look like. Therefore, a symmetrically designed canoe that is trimmed slightly stern heavy is not necessarily the same as a boat that is deliberately designed with less stern rocker when properly trimmed to the DWL. In addition, many other aspects beside rocker may be asymmetrical both below and above the waterline and they will all affect performance and handling.

I don't think there is any recent push toward asymmetrical designs. If you look at the plans for any number of classic pulling and sailing vessels, you would be hard pressed to find more than a handful of them that are symmetrical. Asymmetry is the rule and not the exception in just about everything except classic Canadian canoe designs. Most of the classic pulling boats had "cod head" shapes that are narrower aft with up swept lines at the stern, often leading to elegant wineglass transoms. They also have little in the way of rocker. St. Lawrence River skiffs, Whitehalls and Rangeleys all were built that way and they are proven to be among the fastest fixed seat pulling boats ever designed. My little boat Scherzo is also built that way.

There are other asymmetries for other reasons. The Bell Wildfire is symmetrical throughout except for the sheer, which is higher forward that it is aft. The Bell Yellowstone Solo, which came out of the Wildfire design, has a differential rocker added to the hull. This wasn't accomplished merely by seat placement. It is an entirely different design catering to the needs of less skillful paddlers who had trouble keeping the Wildfire in a straight line. Then there are all the racing canoes that are narrower in front with the idea that they slice through the water better.

I don't think the canoe manufacturers are misleading in publishing these design specs. I think they are just trying to present some handy reference points to their prospective customers that are based on the lines as the designer drew them. I really feel that it is often the paddlers that end up misleading themselves. :)

_________________
“We can have great disparities of wealth or we can have democracy. But we cannot have both.” - Former Supreme Court Justice Louis Brandeis


Top
 Profile  
 
 Post subject:
PostPosted: January 26th, 2008, 8:34 am 
Offline

Joined: September 28th, 2004, 6:52 am
Posts: 442
For the most part I agree with BK except that I have always made lines drawings available to anyone who wanted them. We provide simplified lines on the Green Valley site. Most people don't understand them anyway so publishing them doesn't really amount to much. Many builders fear that people will steal the lines and build boats. Usaually people are to lazy to do that and prefer to pull moulds off existing boats. Happens occasionally and I am sure the people who do will rot in Hell.

Sea Kayaker magazine has published lines of kayaks for years.

I once asked Harry Roberts (Canoesport Journal) why they didn't publish lines and he said most builders didn't have them.

The rocker thing has been discussed here before and essentially it is a meaningless number since builders do not measure it the same way so what's to compare? The person who deamed up "rocker" will also rot in Hell.

I attempted to get Canoesport to use a profile coefficient but builders did not have lines drawings so the could not calculate it without measuring a boat. Scratch that idea.

I agree with BK that customers read into measurements more than they should. Not sure if that is good or bad. As I get older I care less and less.

_________________
Cheers,

John Winters


Top
 Profile  
 
 Post subject:
PostPosted: January 26th, 2008, 8:47 am 
Offline

Joined: June 13th, 2007, 1:31 pm
Posts: 1102
Jwinters wrote:
For the most part I agree with BK except that I have always made lines drawings available to anyone who wanted them. We provide simplified lines on the Green Valley site. Most people don't understand them anyway so publishing them doesn't really amount to much. Many builders fear that people will steal the lines and build boats. Usaually people are to lazy to do that and prefer to pull moulds off existing boats. Happens occasionally and I am sure the people who do will rot in Hell.


Jwinters

Slightly Off-Topic, so I hope the half-hijack is ok, but I am curious...

What is a purely "Ballpark" figure for a mould these days???

Let's say a guy came to you and asked you to build him a mould...
and you had full autonomy to pick the lines of it...
ie... you didnt have to cater to the customer, just grab your materials
and just start creating a mould from your minds-eye...

Ignore your "Creativity Fee, Intellectual Property Fee, etc..."

Just Time and Material... for a decent 16 footer to your personal suitability.

What would be a reasonable cost in your estimation?

Regards

Sundown


Top
 Profile  
 
 Post subject:
PostPosted: January 26th, 2008, 2:22 pm 
Offline
User avatar

Joined: January 29th, 2007, 10:19 am
Posts: 2461
Location: Just outside the Blue Line
Jwinters wrote:
For the most part I agree with BK except that I have always made lines drawings available to anyone who wanted them. We provide simplified lines on the Green Valley site. Most people don't understand them anyway so publishing them doesn't really amount to much. Many builders fear that people will steal the lines and build boats. Usaually people are to lazy to do that and prefer to pull moulds off existing boats. Happens occasionally and I am sure the people who do will rot in Hell.


I was mostly speaking about the big companies, not the designers themselves. I should have mentioned Green Valley and Bear Mountain as well since they also make simplified lines available. I know some designers make study plans available for a nominal fee, and that can be very helpful to those who are hungry for a bit more knowledge.

I agree that most folks can't understand or interpret lines drawings, especially when looking for subtle differences. Still, I think it would be nice to see a simplified body plan. The graphic design software used to create 3-D renditions of canoe hulls that are used by some makers in advertising should be able to spit them out without a problem (I know for a fact that Maya can do it).

This idea of "stealing" lines has always puzzled me. The time honored practice of takings the lines off an existing boat seems to have fallen to the wayside. I have often wondered just how much of a boat design can be considered copy protected. When I wanted to make a copy of a Wildfire, I went right to the source and asked DY and Charlie for permission. This was a matter of common courtesy and respect for them rather than fear of a copyright infringement lawsuit. But if I took the lines off an existing Wildfire and modified them a bit, is that considered a new design? In a legal sense, not in an "eternal fire" sense?

Like you said, John, boat design is an evolutionary process. In the old days, a designer could look at an existing hull and make a half model that was as close as his eye could see (that ability is tuned in some folks to an extraordinary degree) and then take the lines directly from the half model. My question is, where is it OK to start from in a canoe and how much different do you have to be to have an original design?

_________________
“We can have great disparities of wealth or we can have democracy. But we cannot have both.” - Former Supreme Court Justice Louis Brandeis


Top
 Profile  
 
 Post subject:
PostPosted: January 28th, 2008, 2:47 pm 
Offline

Joined: September 28th, 2004, 6:52 am
Posts: 442
BK wrote:
Quote:
My question is, where is it OK to start from in a canoe and how much different do you have to be to have an original design?


I know of no absolute on this. I have been an "expert" witness in cases where I thought one side or the other would win and was wrong. Judges and juries are inscrutable and, for the most part, don't understand the problems anyway.

My personal opinion is that any change that does not significantly affect performance is a clear theft of intellectual property. So, for instance, if a person took an existing design, modified the shape of the stems but changed none of the hull shape it is theft. On a more technical basis I think that a boat that retains the original boat's form coefficients (+/- 1%) is theft. Because these coefficients are non-dimensional scaling a boat is theft.

Keep in mind this is just my personal opinion and suffers from the bitter taste of seeing my own designs competing with with boats built by legitimate builders who pay me royalties.

Of course, the reality is that it is only perceived as theft if you take the crook to court and win. :D :( My son the high priced lawyer says court it isn't worth it unless you hpe to get a settlement in the six figure range or if you don't care if you win or not and just want to make an expensive point.

BK is right that it would be no big deal to publish lines and even less to publish the form coefficients, stability curves and performance estimates. Even if the consumer did not understand them they might ask key questions and become better informed. Any lines drawing can be easily published in PDF format which always looks good because hte curves are nice and smooth.



GB wrote:
Quote:
What is a purely "Ballpark" figure for a mould these days???


I have no idea. Been years since I was involved in mould making. I used to charge $50 per square foot to build a hull plug. That may date me rather badly. :D

I would guess that a production quality mould could cost $100 per sqaure foot but if I am off it is on the low side. I bet the people using resin injection or infusion or whatever spend a lot more.

Glad I don't have to do that.

_________________
Cheers,

John Winters


Top
 Profile  
 
 Post subject:
PostPosted: January 28th, 2008, 6:20 pm 
Offline

Joined: April 27th, 2003, 10:25 am
Posts: 1351
Quote:
What is a purely "Ballpark" figure for a mould these days???

Between 2-3 times the finished part, but that's "ballpark".

Quote:
That may date me rather badly.

If you'd be willing to work that cheap I know where you can find quite a bit of work. :lol:

Quote:
I bet the people using resin injection or infusion or whatever spend a lot more.

That's a safe bet. To go into production for infusion you should really be infusing the mould since the process exerts over a ton of pressure per sq/ft. That's a lot of stress on a mould.


Top
 Profile  
 
 Post subject: Finished pix
PostPosted: January 30th, 2008, 12:58 pm 
Offline
User avatar

Joined: July 18th, 2007, 10:25 pm
Posts: 89
Location: Vermont
Born, a 16-lb, 8 oz. child any mother could love--from a distance--on a moonless night.
http://www.vermontel.net/~bobmoran/Finished-2.JPG
http://www.vermontel.net/~bobmoran/Finished-1.JPG
Now on to the combination seat-backrest/portage-frame/camp-chair.

_________________
There's only one world out there; we'd do well to take good care of it.


Top
 Profile  
 
 Post subject: Re: Finished pix
PostPosted: January 30th, 2008, 1:42 pm 
Offline

Joined: June 13th, 2007, 1:31 pm
Posts: 1102
Graybeard wrote:
Born, a 16-lb, 8 oz. child any mother could love--from a distance--on a moonless night.
http://www.vermontel.net/~bobmoran/Finished-2.JPG
http://www.vermontel.net/~bobmoran/Finished-1.JPG
Now on to the combination seat-backrest/portage-frame/camp-chair.


Sweet :clap: :clap: :clap: :clap:

Um... trade ya some sugar for that Oak/Ash in the Background???

Well Done, Sir.

Regards

Sundown


Top
 Profile  
 
 Post subject:
PostPosted: February 13th, 2008, 11:57 am 
Offline

Joined: July 29th, 2005, 11:03 am
Posts: 100
Location: Vandorf, Ontario
Hi Graybeard,

I hope your project is progressing well. I thought you might be interested in this article. The builder has used 1/8" thick strips and 4 oz cloth on a 18.5' stripper.

Regards,

Moonman

http://www.smallboatforum.com/PDFfiles/ ... Canoes.pdf


Top
 Profile  
 
 Post subject:
PostPosted: February 13th, 2008, 1:37 pm 
Offline
User avatar

Joined: July 18th, 2007, 10:25 pm
Posts: 89
Location: Vermont
Moonman;

Thanks very much for that link!

His techniques are quite different from mine and so provide quite a feast for thought. I notice that his form's edges are covered with what looks like 3M's "Blue Tape," their premium masking tape, to prevent glue squeeze-out from bonding the strips to the forms. I used that tape on the recent build and will never use it again for that purpose--the glue stuck to it like, um, glue. I was seriously afraid of destroying the boat trying to get the stem moulds out. A word to the wise: test the glue you intend to use on the release-tape you intend to use. I'll go back to 3M clear plastic packaging tape on my next build.

I was also delighted to read his comments on David Hazen's Abenaki. I built the 14' version in '87. David considers it strictly a solo boat but since my wife and I together only weigh 240 lbs and use quite lightweight camping gear I fitted it out for tandem use.
We've found it to behave just as Hazen described it; fast, somewhat tender, tracks extremely well, and requires a harbor tug to turn. The tenderness is within our comfort zone as long as we have camping gear stowed low but pushes our comfort zone without the ballast. Now, after twenty years of use, I intend to redo the seats so they can be easily lowered or raised a couple of inches to make day trips less spooky. We've found the 14' size to be quite satisfactory for us; not overloaded on trips up to a week, yet not needlessly heavy.

Again, many thanks for that link.

b

_________________
There's only one world out there; we'd do well to take good care of it.


Top
 Profile  
 
 Post subject: Maiden Voyage
PostPosted: April 20th, 2008, 11:08 pm 
Offline
User avatar

Joined: July 18th, 2007, 10:25 pm
Posts: 89
Location: Vermont
The Deed is Done!

On Saturday, April 19, Awetcanoe joined me for the maiden voyage of Lillian on Glen Lake in West Central Vermont.

1. She floats.
2. Initial "tippiness" characteristic of pack canoes is modest; less than a Hemlock Nessmuk as I recall the Nessmuk.
3. She firms up nicely and smoothly as weight is shifted to heel her. Since it was only days after ice-out, I didn't heel her to the gunwale.
4. I'm quite happy with both her tracking and her maneuverability but that is not based on wide experience with pack canoes in the 12' +/- range. She certainly maneuvers more easily than my 14' rockerless tandem but, naturally, doesn't track as well.

She can be seen athttp://www.vermontel.net/~bobmoran/Lillian.JPG

I finally settled on a single coat of spray-can enamel for UV protection. Auto lacquer would have required at least three coats for reasonable opacity and UV filtering spar varnish would have required at least two coats, weighed much more, and cost much, much, much more.

The seat shown in the picture shows promise but is still under development as a combination seat/backrest, camp chair, and attachment point for a cut-down pack frame.

Yes, I'm a happy camper!

b

_________________
There's only one world out there; we'd do well to take good care of it.


Top
 Profile  
 
 Post subject:
PostPosted: April 21st, 2008, 8:34 am 
Offline
User avatar

Joined: February 3rd, 2008, 8:02 am
Posts: 23
Location: Down low in the hills of Vermont
And yes Bob now has a used boat, here is his first time entering it.
Image

And about a mile away on the other side of the lake,
Image

We paddled a 3.73 mile route around the lake. Temps climbed into the mid 20s and was severe clear skys. It was a nice outing.

_________________
Cheers,
Charlie
If it ain't broke, modify it!


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 92 posts ]  Go to page Previous  1 ... 3, 4, 5, 6, 7  Next

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group