Firewood or a boat?

[beekeeper]

An almost composed post will go away if one clicks refresh instead of spell check. :x
As Forrest said I will redo it "again".

1. How does turbulence behind the boat slow it down? Has anyone paddled both kinds of pirogues and would have a first hand impression? I squared my boat's stern to increase the capacity and but still fit into my truck (location sensitive).
2. Slower deceleration means longer or shorter glide?
3. The straight sides of the bottom decreased the rocker. If the sides were not straight but tapered from 36" beam near center to the two end ribs (24" beam) could the sides be cut convex to keep the rocker the same?


I know. I know seedtick says just build one out of cheap and see how it works. Probably quicker and easier than trying to post these questions.

beekeeper

 

[JEM]

2. Let Matt answer this one.

I wouldn't be comfortable doing that since I don't have the hull in front of me or a working software model.

 

[Kayak Jack]

1. How does turbulence behind the boat slow it down? Has anyone paddled both kinds of pirogues and would have a first hand impression? I squared my boat's stern to increase the capacity and but still fit into my truck (location sensitive).
2. Slower deceleration means longer or shorter glide?
3. The straight sides of the bottom decreased the rocker. If the sides were not straight but tapered from 36" beam near center to the two end ribs (24" beam) could the sides be cut convex to keep the rocker the same?

1. Beekeeper, turbulence is an indication that drag has already occurred. Turbulence doesn't slow you down; it is the visible indicator that drag has already done that. If your boat were pointy on both ends, it would part the water in front, and put it back together again (albeit not perfectly) as the water slid off the back pointy end. A squared off end will not do that, and drag is created.

Stick your hand down in running water and see the turbulence behind it. The pressure on your hand is similar to drag on the back of a square boat.

2. Slower deceleration means a longer glide. It is slowing down at a slower rate.

Water (a liquid) and smoke (a mixture of gasses) are both fluids. Fluids flow. If the flow is streamlined, it loses very little energy. When a flow is disrupted, like a rock in a stream or a blunt end on a boat, turbulence is created. The streamlined flow no longer knows where to go, and seeks new paths. That takes energy. Energy can move you forward or in some other directions. Energy that is moving in other directions is not available for forward motion. So, you slow down and/or have to paddle harder.

 

[beekeeper]

1. Beekeeper, turbulence is an indication that drag has already occurred. Turbulence doesn't slow you down; it is the visible indicator that drag has already done that. If your boat were pointy on both ends, it would part the water in front, and put it back together again (albeit not perfectly) as the water slid off the back pointy end. A squared off end will not do that, and drag is created.

Stick your hand down in running water and see the turbulence behind it. The pressure on your hand is similar to drag on the back of a square boat.

Water (a liquid) and smoke (a mixture of gasses) are both fluids. Fluids flow. If the flow is streamlined, it loses very little energy. When a flow is disrupted, like a rock in a stream or a blunt end on a boat, turbulence is created. The streamlined flow no longer knows where to go, and seeks new paths. That takes energy. Energy can move you forward or in some other directions. Energy that is moving in other directions is not available for forward motion. So, you slow down and/or have to paddle harder.

:? :? :? I understand that the boat passing through the water pushes it aside and this causes turbulence. The stern end of my boat is tapered to shed the water flowing around the sides. If the turbulence occurs behind my boat how can it effect forward motion? The boat is similar in shape to a boat tail bullet. I don't see how the absence of a pointed stern would be a significant loss of speed? Are you saying the water passing around a pointed stern moves the boat forward? I thought forward energy came from pushing/pulling off the paddle's resistance in the water. All else( friction, weight, hull shape, etc.) is resistance to forward movement. A more pointed forward section would be an obvious improvement for my boat.
Thanks for you input and patience

beekeeper

 

[jdupre']

The turbulence at the square stern causes water to be actually pulled along with the boat rather than smoothly turning it loose as in a pointed stern boat. Might not be noticed much at 2mph but starts to come into play at about 3 mph. I've seen resistance charts online for all types of paddle craft and there is VERY little difference among them at around 2mph. For every quarter or one half mph above that, you start having to make significant changes in design. Narrower and longer is what does it. Almost no getting around it. Probably narrower with sharper ends gives the most bang for the buck. You can't fool physics.

 

[beekeeper]

Thanks jdupre' I think I'm only one :? now and that's probably better than normal. :lol:
Guess it is back to the compromise, and trial and error game. Set some goals (location sensitive), apply ideas, build it the best you can, hope for the best, and never be completely satisfied. So much fun.

beekeeper

 

[Kayak Jack]

Joey is right. You're pulling water some along behind you. Pointy ends pull less water. The more you pull, the more turbulence shows. If you could see a shape in a smoke tunnel, you would see it plainly. In water or air that is all one color, it is hard to see.

Look in a stream of water, in behind a rock or log, there will be an eddy. If a downstream current is strong enough, and the shape of an obstruction is angled enough, the eddy will actually reverse and flow upstream. Only difference here is, the obstruction is standing still and fluid is flowing past it. A boat passes through (somewhat) still water. It's the relative motion that provides the power, and the obstacle that provides a disruption.

The small, circular eddies off the ends of your paddle are the same phenomenon.

 

[beekeeper]

I think I know why I didn't understand at first. Very few eddies in south Louisiana and I make too big a splash with my paddle to see any behind it. :wink:
With all the science applied to our paddling boats I know there is a formula or computer program to figure my lose of speed relative to each feature. I will take the simple route and ask these questions:
1.Has anyone paddled a pirogue standard shape and a similar one with a square stern. I'm thinking a UJ model because the plans say build it to plans and then add the transom. 2. A pirogue with outside chines and one with out them? 3. A wider than normal (24" for the UJ I believe) bottom, my skiff is is 28". and a standard one. 4. The UJ plans show two builds, a 3 rib or a 4 rib boat., has anybody had experience with both?
Real world, common sense, impressions of actual comparison of useing two similar boats but with different features is what I'm asking.

beekeeper

 

[jdupre']

Bee, something just popped into my mind that might be up your alley. It seems you are quite interested in stability but you kind of like a fairly quick boat too. Why not a fairly long and skinny pirogue/kayak type boat with removable outriggers? If you make them quickly deployable, you could scoot out to your fishing spot and just plop those outriggers down and have a super stable platform. For any change of location less than a half mile or so, you could just leave them down and not really pay a big drag penalty. Best of both worlds.

Joey

 

[oldsparkey]

I made a pirogue at 18 feet and then cut off the stern at the one foot mark. The stern was at the water line and did not create a back wash. The stern was squared off but the bottom of the boat was still at a point.
To check it I paddled threw some algae on the surface of the water and it just flowed back in like it would do with a pointed end. Not a wide disturbed (mixed ) trail of algae and water like you would see behind a wide stern boat.

What Jack was saying about the eddies , I used them on the last trip to hold me in place. The water was flowing
quite well in the creek and turning around to see where the guys were I would slip up on the down river side of a larger Cypress tree and the eddy from the water flowing around the tree. It would hold the canoe there for me with the point of the bow against the tree. The canoe was in a direct line from the tree , down river side , and in that eddy. The lazy way to take a break and stay in one spot without getting a paddle wet.

Chuck.

 

[beekeeper]

Joey
I considered a longer boat, and the use of an outrigger befor I built the skiff. My goals were a simple, easy to paddle, stable enough for my large size, fit in my truck by myself, boat to fish out of. A longer boat with outrigger would meet the goals of stability and easy to paddle, but would be a compromise of simplicity and fitting into my truck. My skiff is simple to use, stable, easy to load, and I didn't have to remove my tool box for it to fit in my truck. It is not "hard" to paddle, but after leisurely paddling and fishing all mourning with a tail wind, the return paddle into a stronger wind could have been easier. I am not an experienced paddler. The boat may be easy. I have no experience base to know. Your comment about it's pace and the head wind trip makes me believe it is not.
I'm trying to decide what and how much any changes will be, befor doing all work.

Chuck
How wide was the bottom of the boat at the transom? It may be I can have a narrower transom, keep the same length of boat without too much loss of stability.

beekeeper

 

[oldsparkey]

It was really narrow , about an inch at the most with about 6 inches at the top. Just enough that later on I could of put a small trolling motor on there, if I would of wanted to.

Chuck.

 

[Kayak Jack]

... Why not a fairly long and skinny pirogue/kayak type boat with removable outriggers? ...

Here is a site that has good sponsons. The guy is a nut, but his product is good. I have them and like them. http://www.sponsonguy.com/

But, be forewarned, this guy is a fruitcake.

 

[beekeeper]

Chuck
I understand now. Your boat is pointed under water, a dull point, but not a pronounced square like mine. If I would have added another foot to the rear of my boat it could have been pointed, but not fit into my truck without removing the tool box.

kayak Jack
Thanks for the "interesting" link but now I'm too scared to get back in my little boat. :wink: Good to learn if I capsize and die somebody else will be at fault fault ($ $ $). :shock:

beekeeper

 

[Kayak Jack]

Bee, for nothing else other than a good example to your kids and family, ALWAYS wear a PFD if even approaching the water. The example will teach the kids that "Even the Olde Man believes what he does." lesson.

And, of course, there's always the offhand chance that it will save your sorry ar$e. But the rally important thing is - it could save THEIRS.

 

[beekeeper]

Kayak Jack
I'm puzzled as to you assumptions. You posted the link by the "fruitcake", your words. I was humorously commenting on it's death and doom tone. The purpose of the :wink: at the end. The site also portrayed different groups responsible for all types of deaths including people wearing PFD's. My comment about this was followed by a :shock: indicating another attempt at humor. I should have refrained from sarcasm and commenting on any thing not boat building or paddling. Your opinion of me being a"sorry ..." is is not puzzling to me. It's the fact you assumed I'm not a responsible user of nor an advocate for PFD's use, that puzzles me. :lol:

beekeeper

 

[Kayak Jack]

Well, I blew it. Sorry 'bout that.

 

[funbun]

You could also consider Gary Dierking's Three Board Canoe. It has a separating hull design and no part of the boat is more than 8 feet long.

It's mostly a sailing vessel, but I've emailed him and this kind of boat is used for fishing open water in the south pacific a lot. I wanted to build one, but I've settled on a jon boat: not much waste, lots of carrying capacity, and don't need much speed.

If you want more speed, just throw a trolling motor on the thing. As they say in aviation, anything can fly if you give it enough thrust. For me, I'm tired of paddling. I want to fish.

 

[Kayak Jack]

Take apart boats offer a special appeal all their own. I've seen canoes that come apart into two,and three sections. The boat does not need a full bulkhead at points of attachment. They do, however, need a reinforced lip of a few inches deep where they bolt together - and a good seal.

Properly done, all sections will nest into each other. They will not be symmetrical, or equal length. Length and width has to be carefully considered for nesting to be permitted.

 

[Coal]

Some other nesting designs by Ken Simpson.

http://www.duckworksbbs.com/plans/simpson/EZ/index.htm