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Thread: Geodesic Airolite Boats

  1. #1
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    May be of interest,

    Geodesic Airolite Boats
    http://gaboats.com/
    (Arrow 14)

    20 lbs for a solo canoe!

    Could these covered in Kevlar?
    Are they tuff enough for a week n the back country?

    Doug

    .

  2. #2
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    Cool, aren't they? I could be mistaken but I thought I read that Platt Monford recently passed away. Sorry if I've got the facts wrong.

  3. #3
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    It appears that many people worry about the toughness. In the Q&A section there are instructions for adding a second layer of dacron.

    It is difficult to say if the second layer provides enough toughness ...

  4. #4
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    Platt passed away on June 9, 2005. His widow, Bette, is going to continue the plans business. I've always loved his designs, even if I didn't have the courage to build one. RIP.

  5. #5
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    I've rowed a wherry and paddled an open double blade of his designs and plan to make a kayak for Mary Ellen one day.

    I have no qualms about the toughness of heat-shrunk dacron over wood and carbon fiber that's then epoxied.

    Like any light hull, it won't withstand a point impact. I'd not try a "seal launch" off a jetty, but then again, lots of glass kayaks can't take that either.

    I saw one guy carrying a wherry on his sholders on a windy day. A gust got under it and blew it tumbling down the beach before I - happened to be to leeward about 100 yards - caught it. The boat was undamaged by that.

    The carbon fiber and frame structures prevent tears from going very far. A bit of duct tape will get you home.

    Seems to me a waste to add a second layer of dacron. I've know idea if kevlar cloth can be heat shrunk as well as dacron.

    If you car-top a lot, you might make a boat glove, like kayakers and surfers do routinely anyway, to protect the finish against sand scaring.

    Build these as spec'ed and you'll have a wonderful boat.

    G'luck

  6. #6
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    I built one. As Ian says, it's plenty tough except for a sharp object with a fair bit of weight behind it.

    I made a test frame before I built the canoe, then tested it to destruction. It took "almighty" blows from a hammer to damage it, and even then it was the frame that broke, not the fabric. Then I stabbed it with a big slot screwdriver and again it took a lot of force before it perforated.

    It sure is a pleasure to portage. If you want to "single-trip" the carries, it's the obvious boat.

    In use, the one negative I found is that dirt and sand and stuff tends to work its way between the fabric and the stringers. Then later, if you repaint it and sand it first, the sandpaper cuts through the fabric where the grain of sand bulges it out, and you have a pinhole leak. (You've caused it yourself, but there it is.) This can be avoided by using only a "scrub pad" rather than sandpaper, and also Monfort added one step to the building sequence since I built mine -- hot-glue strips. These tapes of glue are spot tacked to the stringers before covering. Then, when the covering is on and heat shrunk into place, you allow the hot iron to touch the fabric over the stringers and the glue melts and activates and grabs the fabric on each stringer.

    It seems to me that this would keep the sand from getting in between.

    But it was a minor problem. I am quite happy with the boat and the method.

  7. #7
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    They are ultra-lightweight boats and work best in deep water and civilized venues. Geo's are not for testing the wilderness. Even a $3000 lightweight Kevlar/CF/whatever canoe would find the going tough in the boonies. Anyone who showed up for a wilderness trip in an old style 20 lb. Kevlar racing canoe would be advised to come back another time with a more suitable boat.
    Kevlar is an amazing fabric. It's greatest asset is TENSILE strength. In most other ways it's about as good as 'glass. In one way its poorer than 'glass. If it's gouged yellow tufts pop out.
    Being 10 times stronger than an equal weight of steel they can't be sanded off and they are only cut with an exceptionally sharp pair of shears.
    In short, you do not want Kevlar anywhere near the outer surface of a boat.
    Charlie

  8. #8
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    Tests by the Navy at David Taylor sez kevlar belongs INSIDE the boat..

  9. #9
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    No I wouldn't it them with kevlar. The dacron fabric has a lot of flexible "give" to it, and that's why the unit is strong.

    As for back country, well that depends. I do a fair amount of canoeing in N. Ontario. Sure, I'd take it, but I'd treat it like a wood-canvas in the flat water, and I wouldn't run rapids much at all.

    But you could sure hike into some isolated lakes.... I've been thinking about just that since I viewed this thread. Make a 15-footer, paddle across a big lake, then into small chains of lakes in the higher country. Go in spring before the bugs come out... sleep under a simple tarp... do it all solo... lightweight and simple... hmmm.

  10. #10
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    Doug, Kevlar and/or carbon won't work for this type of application as they aren't woven tightly enough to keep water out with a couple simple coats of paint. The thing which keeps water out of a regular Kevlar, carbon or fiberglass boat is the thick layer of resin, saturating the fabric, not the fabric itself. The cloth is in there to strengthen the resin. Without some sort of surface or mold for the liquid resin to flow against and spread out on during application, it would be extremely difficult to try to achieve a watertight surface. If you ever try to saturate these types of fabrics when they're "hanging out in space" rather than up against a mold or solid hull, you'll find that the result looks a lot like screen wire and plugging all those little holes with additional coats of resin is nearly impossible.

    Ian, Kevlar can't be heat-shrunk (at least in a controlled method). It might shrink slightly, just before the heat destroys it, but back when I worked inspecting hot-air balloons the FAA standards for Kevlar-cored deflation and control lines (which hang inside the balloon) specified that they had to be able to withstand a direct, 8-second blast with a balloon burner at close range. That's a LOT of heat from a very big flame.

    This is also one of the reasons that Kevlar is so expensive. Unlike polyester (Dacron), nylon and most of the other fancy fibers, you can't heat and melt the raw material which becomes Kevlar. In order to spin or extrude it out into tiny strands to be made into cloth, rope, etc. they have to use acid to "melt" the stuff.

  11. #11
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    A fellow I know and have paddled with built an Arrow 14 , it is a beautiful boat. Almost too pretty to use. Compared it to a SOF kayak with a 9oz polyester skin the Arrow is more easily abraded on landings and launching after all the Arrow's skin is... what 3oz . I can safely run over barnacles but the Arrow would get ripped . With SOF construction it really comes down to skin thickness. 9 oz is about the lightest weight I'd use.

    In terms of impacts SOF construction does very well.

    I like Monfort's designs they are stronger than they look .

  12. #12
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    I've lusted at the whitehall in this format. Looks like it would just float on air. Probably would if it wasn't tied to a stake on the beach

  13. #13
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    Three Cedars;
    "With SOF construction it really comes down to skin thickness. 9 oz is about the lightest weight I'd use"
    Can you get 9oz Dacron cloth threw Monfort's site?
    Or, would two layers of a lighter cloth be best?

    Thanks
    Doug

    .

  14. #14
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    The type of Dacron (DuPont's private trade name for their polyester fabrics) used for G.A. boats doesn't come that heavy. The heaviest weight available is generally 3.7 oz. This is applied and then heat shrunk to make a nice tight cover.
    http://www.aircraftspruce.com/menus/cs/dacron.html

    The types of Dacron that are available in heavy weights like 9 oz. are not designed to be heat shrunk to fit. They are often heat shrunk as part of the fabric manufacturing process (like sail fabric and high thread-count polyesters built to be windproof, semi-waterproof or downproof) but by the time you get them, they aren't going to shrink much more. Also, you would need an oven big enough to hold the boat to do it if they even would shrink any more as it takes a lot of heat on heavy cloth. The SOF kayak builders have to sew the skins on tightly and to shape, rather than rely on the skin shrinkage as a major fitting tool.

    I'm actually somewhat surprised that any of the builders of SOF kayaks are using heavy Dacron, since it has fairly poor tear strength compared to a similar weight of nylon and the way it tears is very different (and a lot less desirable for that type of use) but maybe the Dacron's lower stretch characteristics are more important than it's limited tear strength.

    In any case, if you want to build yourself a GA boat, you'll pretty much be using Platt's techniques and materials, which have been worked out over the past 20 years or so. If there was some sort of quick substitution that would make the boats better or tougher, it would most likely already be in use by GA.

  15. #15
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    I built a SOF canoe useing kayak type construction. Lashed the joints with atrificial sinew (fancy dental floss) and pegging the breasthooks, stems to keelson etc. Covered with 12 oz nylon from Nelson Bidarka in Washington state. Coated with 5 applications of oil base polyurethane varnish. I started treating it like an egg shell. It has proven to be totally capable of withstanding everyday use. I have never come close to a puncture in spite of running into several underwater snags on the local rivers.

  16. #16
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    If you want a stronger skin, you have three options: add a second layer of Monfort's 3.7 oz Dacron, add a layer of Mylar (both of which are mentioned in Monfort's website), or use an 8 oz Nylon skin from

    Dyson, Baidarka & Company
    435 West Holly St., Bellingham WA 98225
    telephone: 360-734-9226 fax: 360-671-9736

    (no website - call or write)

    I have read that the 9 oz Dacron is no longer available. Above that you get into 12 oz Nylon and 13 oz Dacron, which are much stronger but kind of defeat the purpose of making an ultralight boat.

  17. #17
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    I think you actually really only have two options:
    #1 - build a Geodesic Aerolite-type boat
    #2 - Build a more traditional Skin-on-Frame boat

    Other than the fact that both use a suspended skin and look somewhat similar, these are two very different methods and technologies. People seem to be trying to mix and match parts of them as if they are interchangable, which they aren't.

    If you try to build a shrunken-skin GA boat using the same skin material as a typical SOF boat it's not going to work. Likewise, if you built a traditional skin boat or cover a wooden canoe (eg. Old Town Featherweight model) with 3.7 oz. heat-shrink Dacron, it will work and be somewhat lighter, but it will lose a LOT of durability.

    Doubling up the skin on the GA boats would seem to be the only real alternative to increase puncture resistance. I don't know if you've ever worked with MonoKote, but it's pretty light stuff. It would certainly allow you to make your boat metallic purple if desired, but don't expect it to be a miracle cure for punctures, because it isn't.

    Even with mainstream carbon/kevlar composites, I haven't seen an ultralight canoe or kayak yet that could be classified as particularly durable. Most of the racing and tripping boats which use these materials are doing so more in the interest of making the boats light and stiff, than tough. The fact that in certain aspects Kevlar is stronger than steel or that some types can be used for bullet-proof vests really has little to do with boats. Just ask any yahoo who thought he'd be clever and take a shot at his $1,500 Kevlar We-No-Nah with a 22 and found that it went right through.

    The GA boats are gorgeous boats and facinating constructions, but they have some serious durability limitations compared to traditional skin boats, composite boats or wooden boats. Once you understand that, you should be fine, but there are no miracle materials available which can be substituted to instantly transform one into a heavy-duty, drag it around on the beach and cruise-shallow-rocky-streams sort of boat.

    [ 11-01-2005, 01:48 PM: Message edited by: Todd Bradshaw ]

  18. #18
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    Originally posted by Todd Bradshaw:
    If you try to build a shrunken-skin GA boat using the same skin material as a typical SOF boat it's not going to work.
    Check out the canoe at http://www.capefalconkayak.com/canoe.html

    It weighs 30#, which is actually 2# lighter than the advertised weight of the same length Geodesic Aerolite canoe. The website does not say what fabric is used to cover it, but based on various posts by the builder on the Greenland Kayaking Forum, I suspect it is 8 oz nylon.




  19. #19
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    Originally posted by Doug Canada:
    Three Cedars;
    "With SOF construction it really comes down to skin thickness. 9 oz is about the lightest weight I'd use"
    Can you get 9oz Dacron cloth threw Monfort's site?
    Or, would two layers of a lighter cloth be best?

    Thanks
    Doug

    .
    Doug - Todd covered your question very well. The two methods of construction are different. Stick with one method and no doubt you will be happy with either of them.

    I like to go with the more traditional method just because it is cheaper , quite straightforward to do once you have built a few. After building one or two to someone else's directions you will see that there are different techniques to get the job done just as well. Also you will probably become a designer along the way which is very satisfying especially when you get one right .

    Todd - Heavier polyester is not be as strong as nylon in tear resistance it is true but in practical terms it is plenty strong enough . Personally I've used 9 oz polyester, 8 and 12 oz nylon. Other's I trust have used 16 oz polyester and report upon it favourably. All the fabric came from George Dyson who has sold out all of his 9 oz polyester and 8 oz nylon the last I heard. Dyson has many years of experience and provides reliable service.

    Another source of nylon fabric is kavonfilter@litenet.net here is their blurb and no i don't have any connection to them . " If anyone is interested we have an additional nylon material that is available
    for fabrication of kayaks.We will be carrying soon a lighter weight material in a 8oz & 6oz, in addition to the already 13.0z. stock material.
    Width available in 57-58 " width. Please contact us at our e mail address kavonfilter@litenet.net for more information. "

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