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Planning new pirogue

jdupre'

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Sep 9, 2007
2,286
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South Louisiana
The slightly less flair at the stems don't do much for stability either way. Their main job is to lengthen the waterline and have the added benefit of having a little sharper angle of attack in the water.
 

jdupre'

Well-Known Member
Sep 9, 2007
2,286
38
South Louisiana
Doing some rethinking. If I'm planning on doing some epoxy/glass work anyway, I might just go ahead and tape and epoxy all the hull joints. I definitely don't want to do a whole inside/outside glass job. Taping the bottom and stem joints is really not too bad. Time wise, it's probably close to building with chine logs and wood stems. Epoxy/glass joints are very strong and the 1/4" ply is strong enough everywhere else. I could always put in a couple of ribs if it needs it. Still mulling it over.
 
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jdupre'

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Sep 9, 2007
2,286
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South Louisiana
Thoghts on stability. I've built 3 boats with a 22" wide bottom and approx. 25 degree flair. No real problems with stability. They definitely weren't stand-up and dance boats, but plenty stable enough for my use. I figure it this way. A boat with a 22" bottom sinks a little deeper in the water, lowering the center of gravity, helping with stability........sort of like the heavy bottomed ocean bouy.

I finally figured something out I've been reading about for years. It seems a 4" waterline depth is a good standard to shoot for. I didn't really understand that until just recently. A boat sinking 4" means it's beam is about the narrowest it can go and still be useful in a small paddle craft. Wider beam= more stable= a little less streamlned. Narrower beam=less stable=more streamlined. It's all a balancing act. I'm comfortable in the narrower range of beam widths.
 

oldbuffpilot

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May 13, 2014
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Central Kansas and Central Texas
Well put, simple enough for even for me. I have always favored the shallow draft, but now understand the trade off.Let me add another thought, when Matt drew the crawdad for me he asked if I wanted a flat or V bottom. He explained the V would put more weight in the center for lateral stability and more hull in the water. The last two boats I have built had concave v bottoms only because I was copying my favorite store bought boat.My opinion is both the V bottom and concave V bottom are probably more stable than a flat bottom. The added joint and angle definitely make the fiberglassed bottoms more sturdy. I suspect that would not be true for a coventional wood contruction.The Concave bottom can cause a "suction effect " in soft mud. As we know there are more factors that affect stability. But without a flat bottom it really isn't a pirogue? Thanks for starting the discussion, I really appreciate your real world experince.
 

jdupre'

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Sep 9, 2007
2,286
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South Louisiana
Put another way, the lower a boat sits in the water, the lower the center of gravity and the higher you can mount your seat. I'm favoring a higher seat nowadays. It's a LONGER way up than it used to be.

I've been doing some drawing and this boat is looking to be a shorter, less severe version of the Swamper kayak I built several years ago. That one was 16' long, but the front 4 feet was so pointy that it hardly contributed to stability or floatation. It was hardly 6" wide on the bottom at 4' from the bow.
 

oldbuffpilot

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May 13, 2014
543
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Central Kansas and Central Texas
I can easily relate to your explanations, learning more about how pirogues work. Just thinking I was happy with and thankfull for my hardware store kit pirogue in 1970. I guess the make it better bug bit me! I have several good small boats and still building. Like you said " I could go buy a used canoe to fish out of ".
You and beekeeper have helped with understanding stability and how flare, rocker, and rest interrelate. Now to solve the get down and up seating problem. I 'm working on my older body to solve that up and down problem and helping some. But the eventual solutions probably is a seat inovation.
Keep updating us on your plans.
 

jdupre'

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Sep 9, 2007
2,286
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South Louisiana
Will do.

Re: Flair. I've been noticing in canoe and kayak design information, that most don't have really much flair above the waterline. The most i"ve used is 25 degrees and a couple around 20 degrees. Can't say I saw much difference. I did have a good experience with a little 12 ft x 24" bottomed pirogue that seedtick and Keith Felder built. VERY stable and manuverable. With the wider waterline width due to the flair, it was noticeably slower that a boat with less flair. No free lunch. I think I've settled for somewhere around 25 degrees for my needs.
 

beekeeper

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Mar 4, 2009
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Boat building/designing merry-go-round is powered by capacity (enough to float/draft), efficiency (easy/fast enough), stability (upright/steady enough), suitable materials, appearances, and a few other puzzles. The builders goals will determine which aspect is worth pursuing and what sacrifices must be made. It all depends on what "game" you are playing. A boat can't be the fastest, most stable, lightest, most durable, highest capacity, etc.
Knowing what your needs/goals are then recognizing what is possible and building towards those features will yield a very good boat for you.
We should also understand it may not be right for someone else. The may other needs/goals.

Stability and efficient idea = Narrow bottom with near vertical sides to the water line, then flair the sides to the maximum beam you can paddle. Might be fast and stable but hard on the eyes and getting over logs, shallow water, etc.

Joey I think you miss your Swamper".
 

jdupre'

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Sep 9, 2007
2,286
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South Louisiana
I miss it for the ease of paddling, for sure. It just seemed to go at a pace I liked. It was just a bit too long and cumbersome. Stability was good but the seat needed to be at a maximum of 4" high. It had a 22" bottom with only about 20 degrees of flair. I'll probably go with 22" bottom and 25 degrees of flair. I'm kinda over the 5-10 mile trips I used to do in her. Around 12' long should be about right for me now. Decent speed and stability and weight about 40 lbs or so.
 

jdupre'

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Sep 9, 2007
2,286
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South Louisiana
This really surprised me. I put my angle finder on a bunch of online kayak cross section diagrams from different manufacturers, both recreational and sea kayaks. The average flair of the sides from vertical was 13-15 degrees. The commercial canoes were even less than that. Now, I have been using 20-25 degrees from vertical and beekeeper has been using 30 degrees. Being so many kayaks out there use such minimal flair, there must be something to it. More flair does make for a more forgiving, stable boat, for sure. I'm going to do a little more research on the matter.
 
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Kayak Jack

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Aug 26, 2003
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Okemos / East Lansing Michigan
In my experience on rivers, inland lakes, and the Great Lakes - a semi rounded bottom gave me the most predictable stability. As they go into a roll, it gets more and more resistant to a full capsize because more and more boat is pushing back against the rolling moment. Flat bottoms presented a lot of initial resistance, and as the corner got further under water, the boat would suddenly do a snap roll into a full, unpredicted capsize.

For my uses, the semi rounded bottom is the hands down best (least-worst) design. It provides less resistance to paddling forward, and more predictable behavior in sideways stability. In the Great Lakes area, there is more moving water than in Louisiana. And, still water has different dynamics than moving water. Different stuff swilling in it too.
 

jdupre'

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Sep 9, 2007
2,286
38
South Louisiana
I agree with the idea that flat bottoms have a lot of initial resistance to roll...........and that's what I'm after in my type of paddling. This boat will see almost zero wave action. I've been in rounded bottom boats and I have to agree on the predictable behavior......predictably skittish. It seems I can never relax in one. It's always wanting to move one way or the other. I find it tiring. And as far as this "snap roll" thing, I've never experienced it. I've put an honest 2000 miles in paddlecraft under all conditions including 2 foot waves. Never have I gotten even close to a snap roll. Maybe flat hulls in the 3 foot width range may do that, but hulls in the 22-26" width range don't seem to do that at all.
 

Kayak Jack

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Aug 26, 2003
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Okemos / East Lansing Michigan
More likely it’s just that you haven’t practiced enough at being clumsy? I’ve been honing that skill set a long time. Remember Lurch? I trained him.

A couple of friends of mine have Bell Fire canoes. Those boats HAVE to have cargo in, or they flip. WAAYYYY to tender. They sometimes invite another guy along, to lay in the bottom of the boat as ballast when they don’t have cargo. See, he’s smarter than a sand bag. But not so much smarter as to cause much trouble.
 

beekeeper

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Mar 4, 2009
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Since joining this forum this discussion continues to pop up and probably won't end after this time. That is a good thing.
Jack points out (rightfully so ) that a somewhat rounded design will resist turning over in waves better than a flat bottom boat.
Joey feels like a rounded design feels "skittish".
I agree with both based on my limited experiences. I think the rounded profile when tipped over somewhat by a wave offers less resistance to the next wave pushing on the bottom compared to a flat bottom. The boat rocks and slides over the wave. These differences in profile is also why a flat bottom is less "skittish". The flat bottom offers more resistances to turning over (initial stability).
Both styles have a "snap roll" , "O No" or other explicit moment. The pirogue seems to reach that point sooner because it has less volume. Build one with 12" to 14" mid ship depth and stems 16" to 20" high and it will be hard to turn over accidentally.
Flat sides resist rolling with a flat profile. Round sides roll with the forces but offer more volume.
All these choices are what makes this so much fun.
 

jdupre'

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Sep 9, 2007
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South Louisiana
A couple of key points. If you find yourself in 4' waves while in a pirogue, you've made some supremely silly decisions. Pirogues and most flat bottomed boats were never designed for rough water. Flat bottom= flat water. Horses for courses. When I went on Lake Verret in my pirogues, I got off the water by about 10:00 AM before the waves normally started coming up. I've turned back and went elsewhere when the wave action started early.

Kayaks, with their center cockpits SUCK on tree-cluttered banks in South Louisiana. Pirogues are much more suited for this type of environment. If you find yourself close to the tip-over point in a pirogue very often (which I've yet to reach), you might have the wrong sized boat for your use. Like I always say, to get a pirogue in that position, you have to do something VERY wrong.

And yes, beekeeper, all these choices are what makes it so much fun.
 
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beekeeper

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Mar 4, 2009
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Found this information about canoe designs It seems to mirror and organizes all the discussion here

 

oldbuffpilot

Well-Known Member
May 13, 2014
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Central Kansas and Central Texas
Found this information about canoe designs It seems to mirror and organizes all the discussion here

Thanks for posting this. Basically what you and Joey have been saying about reationships of the different parts and shapes. I might understand it someday!
 

jdupre'

Well-Known Member
Sep 9, 2007
2,286
38
South Louisiana
Spent an hour this morning making a 1/3 rd scale model of the proposed pirogue. I went with a bow shape used in many short, pack canoes. This should give waterline length very close to the overall length. The sheer line is a bit wonky because the ply didn't want to bend exactly right. The reverse curve cut on the bottom equals to about a 4" depth which should give me very minimal rocker which I want.

unnamed - 2022-04-04T144519.196.jpg
 

beekeeper

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Mar 4, 2009
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Looking good. I like the near vertical stems. They give the water line a little more length per over all boat's length, but it is harder to get the sheer line to conform to a point. That is probably what gave you the "wonky" look. Probably will not be an issue full size. Thinner plywood (luan) for the model may have worked better.
What length boat are you considering?
 

jdupre'

Well-Known Member
Sep 9, 2007
2,286
38
South Louisiana
I suspect the gunnels would even out that wonky section. The sheer line pretty much makes itself on my boats, depending on the amount of flair. More flair= more dip in the sheer line at midships. I'll probably cut the sides about 12' long. The finsihed length will probably be about 11' 8" or so. I'll shoot for 8" high sides at midships with around 11-12" at the stems. Not going to fight waves in Lake Verrett.