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PostPosted: May 10th, 2007, 11:32 am 
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Location: Belleville, ON
Ok so I'm well into building the prototype of the solo canoe I designed.

I'm working out a technique that I think will be fast and give me a reasonable durable, lightweight hull. Sufficient to let me evaluate the design without spending too long on building it or too much on quality materials.

Its a household insulation foam core that will be covered in Dacron (polyester) and epoxy.

Right now I've got the stations cut, and about 20, 8' strips done all in less than 6 hours work.

Here are the photos of the stations:
The bow sections.
Image

The stern sections.
Image

Total cost of foam for stations and hull is about $60. Weight without epoxy is going to be about less than 15 lbs.

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PostPosted: May 10th, 2007, 12:39 pm 
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Seems to be almost round-bottomed amidships, to me that appears T-I-P-P-Y.... almost like the racing shells I used to row, but I have no idea what you designed it for, maybe explain why this shape?

Has anyone else made canoes from strips of foam or core material, like Core-Cell... I've thought of building an economy "stripper" from some foam material, I know that fiberglass and epoxy will bond to Core-Cell, dunno about the 8-foot sheets of insulating foam available at Home Depot.

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PostPosted: May 10th, 2007, 12:43 pm 
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Neat!

My guess is you're going find this one a bit challenging to paddle, I think it's going to feel pretty tippy - both getting in and out and also once it's on the water. Your bow will probably feel pretty light to initate turns but the stern's going to drag around corners. I also think you may find it a bit uncomfortable in a strong trailing wind. Headwinds will probably be a little harder to keep the boat from swinging around but tracking should be okay in a tail wind, but there may be some concern about waves coming over the rails.

You've got a center station cross section that looks a lot like a white water play boat I once built that I dubbed cedar humility.

Let us know what you find once it's on the water.


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PostPosted: May 10th, 2007, 12:52 pm 
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Looks like fun, be neat watching your progress. I've been thinking along the same lines for a project and have some lightweight carbon kevlar set aside for it.

Did you plan to use the foam as a mould and wax it or will you be leaving it as part of the core?

frozentripper, epoxy and glass fiber will work with foam and you don't need to go to the added expense of Core Cell if you plan to use a solid glass lamination schedule but the CC is higher density so helps with stiffness.

Other foams can be roughed up with sandpaper before glassing which will give you close to the same mechanical bond as the CC.


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PostPosted: May 10th, 2007, 1:24 pm 
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I was concerned with stability (hence the earlier thread about evaluating hull designs.) But think it'll be manageable for me. Its definitely going to be more tender than an Osprey (or a Winisk :roll: ). Curves show it firming up as heel increases though.

This is a solo boat 15'7" OAL, 15' WL, Beam is 23.5" at waterline. Design is an attempt to produce a low wetted surface. Hull design forward is to have easy turning with bow strokes, but good tracking from the deep aft V. Its meant as a high efficiency stillwater hull for poking along shores and making time solo with single or double blade paddle. Some of the stuff is pretty "extreme" in terms of taking those things quite far. But that's why the prototype build first.

Foam will remain as a core, made of two layers of 1/2" thick strips. Giving a 1" thickness overall. The foam is Owens Corning Celfort 300, 30 psi compressive strength. Bonds well with and to epoxy.

It'll be semi-decked, fore and aft decks about 3'-4' long with the stem molds and stations left inside those areas for greater strength/rigidity.

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PostPosted: May 10th, 2007, 1:55 pm 
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Rapt wrote:
Curves show it firming up as heel increases though.


My gut feeling is that whatever firming up it does will feel very slight and it'll be pretty much right at the point where a paddler would have to have their center of balance in the right spot or they're goin' over. I don't think this one will see mass market potential but it should do most of what you designed into it as long as you're okay with the tender bottom. You might want to learn that white water low brace before you christen it :-)


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PostPosted: May 10th, 2007, 2:10 pm 
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Rolf Kraiker wrote:
Rapt wrote:
Curves show it firming up as heel increases though.


My gut feeling is that whatever firming up it does will feel very slight and it'll be pretty much right at the point where a paddler would have to have their center of balance in the right spot or they're goin' over. I don't think this one will see mass market potential but it should do most of what you designed into it as long as you're okay with the tender bottom. You might want to learn that white water low brace before you christen it :-)


This is where I get to quote JW and say "I didn't design it for the mass market". :D

Really though, its quite a focused design and meant to be my personal boat. At the very least a step towards my "ideal" and educational in the extreme... It may be slightly more tender than I'd want, but that's all part of the learning process.

I'll probably be going swimming with it since I hope to have it built and christened in a couple weeks... Not more than a month.... More to follow on the building technique that I hope will let me do this.

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PostPosted: May 10th, 2007, 2:39 pm 
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More on the technique...

I'm cutting all the foam using a hot wire cutter. There are numerous plans and ways to go about making one. With tons of info available online. Mine uses a regular car battery charger and a regular household dimmer switch to regulate the current and thus the temperature. The wire is stainless steel, about .030" and available at home DIY type stores.
Image
In the picture you can see the cutter, the dimmer on the to[p of the arm, and the fence I have set up to let me cut even strips. Also you can see the strip and a piece of scrap from the stations that I'm converting to strips. I'm using 1" foam and cutting half inch strips.

Here you can see the fence and wire in action.
Image

And finally a bunch of strips and how tough and flexible the foam is in thin sections.
Image

More updates to follow as time and progress allow....

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PostPosted: May 10th, 2007, 4:51 pm 
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I am enjoying this. Keep us informed about your progress.

Quote:
prototype of the solo canoe I designed.


Any hint about the software used in your design?

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PostPosted: May 11th, 2007, 8:53 am 
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I doodled with your photo a bit to change the perspective so that I could see it looking more straight down. Hard to say how much that's changed the shape from what you actually created, but it didn't look quite as round once I did that. I overlaid some changes that I'd be inclined to make based on my experience for your info original in red on left, changes in blue on right. I only did the bow.

Image


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PostPosted: May 11th, 2007, 10:06 am 
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Shy,
I did this design in Bearboat. Its easy to use and easy to output. But still lets you have reasonable control and provides useful parameters and stability curves.

Also transfered it to Deftship/Freeship... Lots more control, and neat faring information, but getting an output is less straightforward and convenient for me at the moment.

Rolf,
There is in fact more "flat" in the bottom than is apparent. A portion of the midships bottom is totally flat due to my constraining the draft to be no more than 4". So its not as "round" as many think. The flat starts with the fourth section and widens out to about a foot by midships. Fairly broad since its only 23.5" wide at the waterline at midsection.

Your tweaks look pretty subtle to me, but I do see some variance. To me it looks as though the entry is a bit finer/sharper and the more midsections are a bit fuller higher up and slightly more elliptical below the waterline. More traditional in shape. But as you may have guessed I'm not necessarily tied to "traditional" although in some areas I like it.

I've been playing with the design and looking at the 'effects' in the theory side for about 5 years. Using KAPER, stability curves, etc... There is surprisingly little calculated difference in subtle hull shape variations, doing things like you've illustrated. So I went to an extreme with the design, trying to have full 'U" shaped sections forward and more "V" shaped sections aft to see if the variations that don't show in calculation do really make that big a difference in feel. I was also seeking to keep a fairly strong flare in the hull to help shed waves/spray, without making the hull too wide for easy paddling.The other thing is this hull is quite asymmetrical, which I may have taken too far as well. My understanding going too far with the asym thing can make a hull thats very trim sensitive.

But I wanted to do this and learn from it rather than just build someone else's design. At least partly because until Placid came out with their Rapdifire, and Steve Killing/Bearmountain announced their Freedom Solo 15'3", I hadn't seen anything that looked close to what I was looking for.

Even if the hull is a total failure in meeting my design goals it'll still be a big success in teaching me a lot about the subtle aspects of hull shape. Mainly after years of doing the theory and trying to sort out an inexpensive quick way to build hull prototypes I figured its time to actually try it out. :) Put my butt where my mind is ... or something like that. :lol:

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PostPosted: May 11th, 2007, 10:48 am 
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Rapt, I really aplaud what you're doing. I did much the same thing early on but didn't use a computer program in the design - did it old school with full size paper drawings. Some of what I did in my designs weren't completely successful but like you I still counted that as a success because I learned a ton in the process - plus there's a huge satisfaction in having done it.

I found your comment about slight changes in design not having much effect when the calculations are done puzzling. That doesn't agree with my experiences having gone through some of that tweaking process. The closest thing I can think of to compare it to is moving big flatish rocks (something I'm doing a fair bit of at the moment). There's a balance point where it takes a great deal of effort to get it to the point where the rock will roll over easily but once you reach that point, you can relax and it takes very little effort to roll it over. The canoe hull is kinda like that except in reverse. The little extra fullness I added to your midsection will provide that rolling resistance and give the paddler a bit more time to adjust with either shifting body weight or paddle force application. I think your lines would put you on the balance point very quickly - but it's hard to tell from the photo and hey, I could also be way off base.

The tweak I made to your entry line (second station) should do a couple of things. I think it'll help improve your handling in waves (keeping the boat drier) and it should also help with control surfaces during turning when you heel the boat over. I don't know if your computer program will let you do this, but when I was working on paper I'd place waterlines on my hull shape at different angles of lean and then plot them out full size lengthwise on paper to see what happens. By redcuing that slight bulge you've got on the bottom of the second station it should improve your tracking without affecting your turning abilities much. If you heel the boat slightly when you turn it should become easier to turn than it would be in your current shape. You should also be able to initiate some turns with my tweak by doing a slight counter lean before starting your paddle control, ie lean right to lenghten the waterline curve on that side forcing the canoe left - once underway, heel it to the left and apply paddle strokes to finish the turn. That technique works well with the right hull shape but it can work against you in the wrong shape. Food for thought when you get around to Version 2.0


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PostPosted: May 11th, 2007, 11:22 am 
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Neat idea... and once you find one that really works you could use it as a mold to pull off a fiberglass hull. Or use the plans for a cedar strip...

I used the same software and designed a 10 foot whitewater boat a while back. Had I thought about using foam strips like that I might have tried it out instead of making a cedarstrip - and I didn't want to go the Kevlar route. As it is, I have only 9 strips left until I start pulling staples and sanding.

I'm concerned about the tip factor, especially since this is the first boat I've designed / built. I'd be curious to see the curves for a boat like the Zoom from Esquif... I got into Al Greve's Zoom and promptly fell out - hoping not to repeat that with this boat!


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PostPosted: May 11th, 2007, 1:13 pm 
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Rolf Kraiker wrote:
... I found your comment about slight changes in design not having much effect when the calculations are done puzzling. That doesn't agree with my experiences having gone through some of that tweaking process. ...


I don't think it should be that puzzling... The calculations are theoretical and don't consider things like shifting CoG. They also don't work out tracking/turning ability.

Mainly the midships sections affect stability, as the ends tend to come clear of the water pretty quickly with heel.

Like you I was surprised to find that minor shape changes there didn't affect stability as much as I expected. Given the waterline beam (23"-24")and maximum beam (29"-30") as well as the maximum design draft (4"), and trying to keep wetted area below 21 sqft for a 15' length means generally only minor variations are possible. Unless you really want to depart from tradition. For example look at a Freedom Splitrock. I test paddled one and was surprised and how the edge felt. It wasn't at all unstable in my opinion, and didn't need the wings, but heeling until the wing touched the water bogged the boat down dramatically and immediately. I hated that feeling, and I had played with that type of shape for a time but discarded it after that experience.

Tweaking the curve of the sides within the outlined constraints seems to make minor variations in the stability curve position and shape. Generally much less than 10% at any point. Tweaks below the water line tended to have less effect than above the waterline. Say a 30/70 split...

A flatter bottom gives a slightly steeper initial slope, but lower peak righting moment and lower angle for negative moment. This shape gave me close to the highest peak righting moment, and greatest angle of lean before negative moment. At the cost of slightly lower initial slope. The lower slope may mean a canoe that reacts too fast to be comfortable, but only getting in it on the water will tell me that. Its very close in initial slope to a rowing dory I built and use that I stand up in easily..

I appreciate your insights and experience and will keep them in mind when I'm at the design table.

Oh and one other thing... Seating will be a kneeling position rather than a seat so effective stability won't be hampered by "sitting" too high. Ideally I hope it can also be paddled by sitting on the floor which should make it REALLY stable.... Like a beginner kayak.

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PostPosted: May 11th, 2007, 2:06 pm 
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Thanks for the explanation Rapt - "puzzling" was probably too strong a word on my part, maybe "interesting" or "curious" might have been better. My puzzlement was more about the discrepancy between what is felt as opposed to what is calculated. I'm not surprise that the calculated difference isn't great, just surprised at how noticable the slight difference is.

Have you spent time paddling a canoe sitting like a kayak? I have some observations about that if you don't have extensive experience. I also have some ideas for a seat designed specifically for that purpose. Be happy to share that.


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