This has probably been asked and answered before, but I have not found it in my searches here or on the net.
The offsets in Ted Moores' book Canoecraft has an area that I cannot figure out. On the Bow/Stern section there are some points with two numbers. Example, in the Hiawatha Chart A at centerline distance 14, the Bow/Stern offset shows 5+ /19 3/4. The 5+ is ok it plots out just fine, but the 19 3/4 has me stumped. I can't figure out what that is. Can someone explain these to me?
Many thanks for any help on this puzzle.
Hiawaths Table of Offsets
Hiawaths Table of Offsets
John Wright
Guess I'm confused. Here is a link to the cad drawing of the bow based only on the offsets without the numbers after the /. It appears to be correct, so I'm not sure exactly sure how the arc figures in to the drawing?
http://www.midlandscc.net/Pictures/bow.png
Many thanks for your kind reply.
http://www.midlandscc.net/Pictures/bow.png
Many thanks for your kind reply.
John Wright
Since you mention chart B I know you have an older version of CanoeCraft. I have two versions and neither one has the plot you mention. I believe with the older version that when two numbers are represented for one plot one indicates the distance off the base line and the other indicates the location of the sheer line.If what you are drawing looks right it probably is.
Hiawaths Table of Offsets
willo,
OK, thanks. I also have the 2000 edition and have checked them against the 1999 edition. They're close enough for government work.
Many thanks again.
I can now fair the curve in my cad program and get them printed for full sized plans. Just have to find someplace that can print something that large.
I am also thinking of doing a little scaling to give me a little more length. I have done something like this in the past with airfoils, but not sure if the same laws will apply to canoe forms.
OK, thanks. I also have the 2000 edition and have checked them against the 1999 edition. They're close enough for government work.
Many thanks again.
I can now fair the curve in my cad program and get them printed for full sized plans. Just have to find someplace that can print something that large.
I am also thinking of doing a little scaling to give me a little more length. I have done something like this in the past with airfoils, but not sure if the same laws will apply to canoe forms.
John Wright
Hi John
Years ago I went to a print shop in Ames Iowa. They were able to take my plans and enlarge them slightly, and make copies.
College towns , and I'm sure Omaha should have something.
One of my first canoes was the Hiawatha, early edition. I wished I would've set it up as a solo, I loved it ! As a tandem it was a little small for my liking.
What modifications are you planning ?
Keep us posted ! Building something a lttle different to me is great !
Good luck
Jim
Years ago I went to a print shop in Ames Iowa. They were able to take my plans and enlarge them slightly, and make copies.
College towns , and I'm sure Omaha should have something.
One of my first canoes was the Hiawatha, early edition. I wished I would've set it up as a solo, I loved it ! As a tandem it was a little small for my liking.
What modifications are you planning ?
Keep us posted ! Building something a lttle different to me is great !
Good luck
Jim
Keep your paddle wet and your seat dry!
Hiawaths Table of Offsets
I was thinking of making it longer, say to 17' feet or so. I just like the lines of this boat more then the RedBird.
The problem, as I see it, with a simple scaling is now the forms are all changed. Otherwise the form placement will move as the scaling increases or decreases. I'm not sure exactly what impact this will have, but right now I am trying to find a way to layout the hull in my cad so I can create new forms 12" apart.
The other issue I have is that, at least with subsonic airfoils, a simple scale up or down does not always works as expected. We start to see changes in the separation points and drag as we scale up. I don't remember if we see this in supersonic (incompressible flow) or not and water is an incompressible liquid so it should behave a lot like supersonic flow over an airfoil.
Anyway, just playing with the numbers and drawings right now. I'll keep you posted.
The problem, as I see it, with a simple scaling is now the forms are all changed. Otherwise the form placement will move as the scaling increases or decreases. I'm not sure exactly what impact this will have, but right now I am trying to find a way to layout the hull in my cad so I can create new forms 12" apart.
The other issue I have is that, at least with subsonic airfoils, a simple scale up or down does not always works as expected. We start to see changes in the separation points and drag as we scale up. I don't remember if we see this in supersonic (incompressible flow) or not and water is an incompressible liquid so it should behave a lot like supersonic flow over an airfoil.
Anyway, just playing with the numbers and drawings right now. I'll keep you posted.
John Wright
John,
IIRC, the Hiawatha was designed to be paddled from the sitting position and if it's going to be paddled solo and reversed, the extra width could be too much. Maybe better in stretch than to scale up in three dimensions... anyway just a thought.
I can't comment on the hydrodynamics relating to aerodynamic principles, but scaling up the Hiawatha so that length, width and depth all increase by the same proportion may have the effect that the hull becomes too wide to paddle comfortably from the sitting position.... just speculating since I've never paddled one.The other issue I have is that, at least with subsonic airfoils, a simple scale up or down does not always works as expected.
IIRC, the Hiawatha was designed to be paddled from the sitting position and if it's going to be paddled solo and reversed, the extra width could be too much. Maybe better in stretch than to scale up in three dimensions... anyway just a thought.
Hi Rick
If I was going to use the Hiawatha as a tandem, scaling it up to 35" width, and stretching it by adding a half to an inch to each station would be my choice. You would have to play with the stem forms to get the hull to fair. That's just my two cents worth.
On the other hand, if I was going the sit and switch solo route, I'd just change the seat placement. I'd probably add some tumblehome too !
Yeah I know that's getting out there, but again that's my take.
Good luck, and have fun with it !
Jim
If I was going to use the Hiawatha as a tandem, scaling it up to 35" width, and stretching it by adding a half to an inch to each station would be my choice. You would have to play with the stem forms to get the hull to fair. That's just my two cents worth.
On the other hand, if I was going the sit and switch solo route, I'd just change the seat placement. I'd probably add some tumblehome too !
Yeah I know that's getting out there, but again that's my take.
Good luck, and have fun with it !
Jim
Keep your paddle wet and your seat dry!
Hiawaths Table of Offsets
Everyone,
Many thanks for all the inputs. A lot to ponder and think about.
Many thanks for all the inputs. A lot to ponder and think about.
John Wright