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Thread: Best freighter hull shape

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    Default Best freighter hull shape

    I'm contemplating building a composite 20+foot freighter canoe. I've been looking at old hull designs and most are running a shallow V or Y type hull. I'm more interested in a shallow arch type hull with a slight flare and somewhere between slight to moderate rocker.

    Is anyone aware of a 20'+ freighter with that type of hull design? Most seem to be more of a lake or open water design.

    I'm leaning towards a carbon fiber core, sandwiched between fiberglass and Kevlar, w/ Epoxy infusion for the hull. No wood in the sandwich.

    Any help or ideas out there?

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    Good question and a great project.

    One thing I noted on my HB...with the Y shaped hull at the transom, when I accelerate the canoe digs in and raises the bow. Not a big deal, but with me back there with a 130 lb engine I have to ensure I add a lot of ballast to the bow. So...maybe think about not flaring the stern at all.

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    I don't want any keel or Y stern sticking down. Our rivers up here are not conducive to that hull style. I'm considering a moderate rocker arch stern. Just a slight rocker on the bow...

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    I'd go with the shallow arch with as flat a bottom as possible. Rather than a keel and keelsons I'd look at putting in slight indents and inlay strips of slippery plastic in them so that the edges where semi protected and have them slightly proud of the hull so they could take the brunt of dragging.

    The stern would have straight lines and I'd avoid the Scott Canoe indents. I'd play with the depth, width and lay-up to keep the weight at no more than 140-150 pounds. This would allow for carrying it on racks and portaging with two men. To this theme I'd make two of the thwarts yoke shaped.

    The light weight would be critical as there are trips I'd like to take my HB on that require a portage past Class 4 rapids/waterfalls. I have considered taking my Rokon and two sets of canoe wheels to accomplish this but 100 pounds less weight and man hauling would be much better. Also beaver dams are all over the place. Even with a Z-Drag horsing a 250 pound boat with 150 pound motor up a 4 foot beaver dam is a bit of a stretch! Lighter boat and motor would make a big difference.

    I have looked at the 20 foot Tripper XL and like it's lines if upscaled just a bit to maintain 20 feet length with a flat stern. In the end I wouldn't bother with the indentations but would research slippery tough solutions for the bottom. I will likely simplify my life and look for a used 20 foot Tripper and side mount a 5-6 Horse for my next boat. Unfortunately used XL's are seldom parted with and often command a price very close to new.

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    I agree with your weights North61. Carbon fiber in the layup for a stiffening layer, should keep the weight down around @150lbs. Kevlar skids for the outer wear areas... Infusion bagging to keep from putting excess resin in the layup. Trying to keep it rigid enough without overkill, is going to be the main engineering problem.

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    Quote Originally Posted by pipercub View Post
    I agree with your weights North61. Carbon fiber in the layup for a stiffening layer, should keep the weight down around @150lbs. Kevlar skids for the outer wear areas... Infusion bagging to keep from putting excess resin in the layup. Trying to keep it rigid enough without overkill, is going to be the main engineering problem.
    If you take on this project please let us know what you learn...very interested in following in some-ones foot steps!

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    I'm in the research and design phase of Freighter canoe construction. I need to finish my current project, restoring a 1977 Piper Supercub, Before I have the shop space available for canoe construction. Late summer of 2014, I hope to be starting this canoe.... Lots of things to consider and materials to line up before then.

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    Sounds like you guys have some good thoughts regards freight canoes. Many seasons ago I built a 20' David Hazen Micmac freighter with the Y, or wineglass transom. This is a 20'X4 X19 " depth canoe built to haul "two men and half a moose." In 5/16 western red cedar core and with overlapping
    9 oz cloth and epoxy finish plus many layers of reenforcement at stem and stern the boat came in at 110 pounds. I used no seats relying on multiple ash thwarts. The gunnels were spacer block style which adds some weight. Haden's Micmac is a big water boat with strait bottom and vestage v shaped
    "keel" features fore and aft. There is not enough bearing surface aft for true on step motoring so its not the hull we might want to run the Little Su upstream under power. However she came in at 5.5 pounds per foot and two people roll her onto roof racks easily. If you widen the aft sections out to say a 30' transom I suspect this boat might still come in well under 6 LBS per foot. With pure composite, and you might want some sort of light core, the weight shoul be even less and light enough to carry over beaver ponds easily. Good luck with whatever you build.

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    Thanks upstreamV, the composite carbon fiber should be in the 6lb per foot range...depending on how carried away you get with the resin and the transom beef ups...I have worked with composite cores in the aerospace industry. I've not decided on wether to incorporate any yet. The aerospace cores are not designed to take any impact stress. There are some pretty tough carbon fiber structural panels available...haven't thought it out that far yet...

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    I'm certainly not an expert here and I've only built an ocean cedar kayak with Kevlar bottom skids...18'/77 lbs. and fast.

    I am playing with CF and vinyl ester with the idea of bagging leading edge parts and maybe ribs for flaps and ailerons for my cub like build. Also trying 5 oz glass too and I'm coming out with parts that are heavier than their aluminum counterparts. Obviously, I have too much resin in the mix and I need to learn how to squeeze it out with the vacuum but I have very little confidence that I could get a 20' canoe together using home grown composite technology and make it lighter than with the wood strip method. If you guys can explain the tricks on how you would do this, please share with the lesser qualified. Don't get me wrong...I love my modified Cargo but I might need a new project when I finish my plane.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

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    Lowrider, why use vinyl ester instead of epoxy resin?

    "Infusion Bagging" using a very low viscosity epoxy resin, cures under vacuum, but still wets out and penetrates the layup. You have to get the excess resin out to save weight. Also epoxy resin strength is @ 2000psi and vinyl ester is @ 500 psi... For aircraft parts you want to use epoxy for maximum cross-linking strength. For the highest strength composites, you would use a heat cure type epoxy. This is not your home depot /lowes type stuff.

    This technology is really advancing and is hard to keep up with if you aren't involved in it on a day by day basis. Boeing and other Aerospace manufacturers are making huge composite structures that are incredibly strong and light. While they have huge forms and autoclaves to work with, Us common mere mortal types, can borrow aspects of this technology, to improve our planes, boats, paddles, surfboards, skiis and whatnot.....

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    My guess is that a good hand laid,or bagged, home build Kevlar boat will beat the same boat in cedar, glass, epoxy layup, weight wise, by the weight of a gallon of whiskey per 18 foot length. The bottle weight does not count!


    In my opinion a good boat can be build by either bagging or hand layup. The key is a technique which guards against having to sand excess resin and that puts fabric weight and resin weight in appropriate ratio from the start.


    There is more than one way to skin that cat. For hand layup first coat wets cloth to point of eliminating white spots, second coat half fills the weave, third coat fills weave. Never find yourself sanding excess resin. Advanced technique often skips the pre soak wet out and wets the core and fabric in one step. Never float your cloth. I am a fan of careful hand layup as vacume bagging cost of bleeder etc. adds up. Put me on the epoxy side of the resin question. It's money we'll spent! Commercial sources can save resin cost and often have better product than that stringy when kicking popular brand.


    Reliance on advanced process does not assure a light boat any more than leading edge cuff and stall fence allow an average cub driver shorter landing than that of a really good pilot in a stock aircraft.


    Attention to detail counts. For instance light colored cedar weighs less than dark color cedar. Absence of this fact has won me a lot of George Dickel as a friend shaved gunnels and skimped on decks in a series of double paddle canoes trying to best a canoe build with 15% lighter core.


    First boats rarely weigh what they should regardless of the layup schedule. Most times that little extra weight is just not that important. If it is important to you get a scale and weigh small test sections until you have it right.


    Here is a good article on cedar boat weight: http://www.greenval.com/weight.html


    Good luck!

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    Well, there certainly are a lot of ideas about what is the right way to do this. I was using epoxy until the "expert" at US Composite told me I should use vinyl ester in any area where there is a chance of gasoline being on the product...so I switched. He said the difference in strength would not matter and vinyl ester would stand up to vibration better than epoxy which could be brittle and vinyl ester would be better to use on leading edges.

    I did a lot of reading and many folks think the glass/vinyl ester mix is the most flexible and withstands chemicals much better than epoxy which is why it is used for gas/chemical tanks. I built a tool box that way years ago for a dirt bike and it is still together and unaffected by oil spilled inside for years on end and it has never cracked even though it has been dropped or banged around repeatedly....pretty tough stuff.

    I'm getting what I think is good test pieces with CF and glass using epoxy and vinyl ester but they are not wafer thin like they should be. On hand layups I'm using 3 coats, the first diluted with alcohol and 2 well screeded coats to get the resin out and smooth up the product. Flat stuff is much easier to do than curved. Maybe practice will make me better.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

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    Sorry Lowrider I was thinking of materials/weights for your possible canoe project. There is nothing about fuel tanks or aircraft parts I would be qualified to address. I think you will build a nice light canoe though from the sound of your hand layup details.

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    I guess if you were building composite fuel tanks, I could understand using it.

    I've seen your project thread on supercub.org. But I have never looked at it, so I not familiar with what type of aircraft you are putting together.
    I'm working on a certified cub project this winter...not much composite work on that....

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    It's just an LSA Cub with a Ribblet wing and an 0-320 so I'm trying to save weight to stay as light as possible. The RV-4 I built came out a little heavy so I'm trying to use the CF and composite to help out where I can.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

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    In 1978 bought a 22' yukon freighter canoe. These canoe's were made in tetlin canada. Empty weight was around 400-450 lbs. Gross weight payload 5000 lbs. Friends had a 20' and they could haul 3750 lbs. They were made out of cedar ribs and cedar planks then covered with canvas oak keel strips and sides.

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    I did not get a chance to read all posts, but this is a video of some 28 footers that were built in Delta for military training...pretty cool outfits and certainly seemed like a ok design...


    https://www.youtube.com/watch?v=UNoddr1-LA0

    I think the river work starts about 6 minutes in....
    “Nothing worth doing is easy”
    TR

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    Gramps was that right after Korea. Looks like paid in two dollar bills.
    Now left only to be a turd in the forrest and the circle will be complete.Use me as I have used you

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    Quote Originally Posted by Amigo Will View Post
    Gramps was that right after Korea. Looks like paid in two dollar bills.
    I think that training at Greely started in 1948, the boats were built into the 70's sometime.
    7' Beam



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